255-100-201 Issue 4

Data Networking Products Terminology  Copyright 1995, 1996 AT&T All Rights Reserved Printed in USA

Developed by Bell Laboratories Technical Publications Center.

ACCUNET, Billdats, Billdats II, CommKit, CompuLert, DACScan, Datakit, DATAPHONE, FT-2000, GlobeView, MacSTAR, SLC, StarKeeper, StarServer, StarWAN, Systimax, Teletype (TTY), and TOPAS are registered trademarks of AT&T. 4ESS, and NetPartner are trademarks of AT&T.

Amdahl and UTS are registered trademarks of Amdahl Corp. AppleTalk and EtherTalk are registered trademarks of Apple Computer, Inc. Banyan and Vines are registered trademarks of Banyan. DEC, VAX, and VT are trademarks of Digital Equipment Corp. HP is a registered trademark of Hewlett-Packard Co. IBM and Token Ring are registered trademarks; PC-DOS is a trademark of IBM, Inc. Microsoft and MS-DOS are registered trademarks of Microsoft Corp. OPEN LOOK, , and are registered trademark of Novell, Inc. Networked File System, NFS, Sun, and SunOS are registered trademarks of Sun Microsystems, Inc. UNIX is a registered trademark in the United States and other countries, licensed exclusively by X/Open Corp. Verilink is a registered trademark of Verilink Corp. XNS is a trademark of Corp.

The information in this document is subject to change without notice. AT&T assumes no responsibility for any errors that may appear in this document. ______

Data Networking Terminology

This publication includes terms used in customer documentation and marketing literature for BNS-2000, BNS-1000, and Datakit II Virtual Circuit Switch (VCS), plus a small selection of terms related to the StarKeeper II Network Management System (NMS), other networking products, and industry standards such as frame relay and Switched Multimegabit Data Services (SMDS). For terms speci®c to the GlobeView±2000 Broadband System and asynchronous transfer mode (ATM), see the system's customer document library. Terms are listed in alphabetical order, in the following sections:

Abbreviations and Acronyms 5 Glossary 25 ASCII and EBCDIC Character Codes 53

Terms are de®ned and special labels are used as follows: A term is de®ned in its singular form, unless only a plural form is appropriate A brief functional description is added to some de®nitions An application for an acronym is listed after the de®nition in parentheses: Inter-Carrier Interface (SMDS) Labels for terms include: Ð abbrev. for a term's short form, which differs from an acronym Ð abbrev. sw. for software messages, reports, and ®les Ð abbrev. command for software commands Ð apparatus code for a hardware component: AWJ15 Ð label for a hardware component such as the switch position: DIAG Ð protocol, ITU-T/CCITT Recommendation, and ITU-T for recognized standards See and see also refer to other de®ned terms Also precedes a synonym or alternative term

Data Networking Products Terminology, Issue 4 3 ______

Abbreviations and Acronyms

De®nitions for many of these terms are given in the Glossary following this section. Some capitalized abbreviations and acronyms appear in lowercase letters on computer screens or in printed system messages and reports.

A AIN Advanced Intelligent Network (SS7 OS)

A also amp. Ampere AIS alarm indication signal (SMDS) AAR automatic alternate routing AISS alarm indication signal seconds (SMDS physical layer) aau command parameter. alarm activator unit; see ARU AI-T1 Access Interface±T1 module (BNS-2000 SMDS) AC alternating current AI-T3 Access Interface±T3 module (BNS-2000 ACD alternating current distribution (cabinet/system); SMDS) automatic call distribution AI-T3A Access Interface±T3 module for asynchronous ACE Automated Cable Expertise (OS); Access transfer mode (ATM) Control Encryption (LCS60E security) AI-T3P Access Interface±T3P module (BNS-2000 ACF access control ®eld (SMDS) SMDS) ACP Adjunct Communications Processor AMA Automated Message Accounting (billing format) AC PS AC Power Supply module AMADNS AMA Data Network Service (TCP ACX582 apparatus code. AC Power Supply unit transfers across LAN/WAN for billing) ACX610 apparatus code. Battery Charger AMATPS AMA Teleprocessing System (BX.25 or X.25 modem links for billing) ADU asynchronous data unit AMI alternate mark inversion (code) AF aggregator to formatter/transmitter amp also A. Ampere AGS asynchronous gateway server ANI automatic number identi®cation

AI Access Interface (BNS-2000 SMDS) ANS Access Network System (OS) ANSI American National Standards Institute AID byte Attention Identi®cation byte API application program interface AI-E1 Access Interface±E1 module (BNS-2000 SMDS) APLS Automatic Protection Logic Switch (Verilink) APS automatic protection switching (Verilink) AI-E3 Access Interface±E3 module (BNS-2000 SMDS) AR Access Rate AI-E3A Access Interface±E3 module for ARA Apple Remote Access asynchronous transfer mode (ATM) ARAP AppleTalk Remote Access Protocol (routing) AIM Asynchronous Interface Module (ISN) ARP Address Resolution Protocol (TCP/IP)

Data Networking Products Terminology, Issue 4 5 ______Abbreviations and Acronyms

ARPANET Advanced Research Projects Agency AWJ10 apparatus code. SWT I/O distribution board Network; see also DARPA, DDN, NSFNET (DTE RS-449/422, optional NRZI)

ARSB Automated Repair Service Bureau (OS) AWJ11 apparatus code. SWT I/O distribution board (DTE RS-232-C, optional NRZI) ARU Alarm Relay Unit; see also aau AWJ12 apparatus code. Disk Drive I/O distribution ASAI Adjunct/Switch Application Interface board (ECPU con®guration) ASCII American Standard Code for Information AWJ15 apparatus code. ECPU I/O distribution board Interchange AWJ16B apparatus code. MRCM I/O distribution ASN.1 Abstract Syntax Notation 1 board ASP2 apparatus code. fuse module AWJ17 apparatus code. CPMML, SDLC8, SYNC8, ASP4B apparatus code. SCSI unit I/O distribution TSM8, and X.25 I/O distribution board (DTE RS- board 232-C) ASP7B apparatus code. CTRM I/O distribution AWJ18 apparatus code. SDLC8, SYNC8, TSM8, board and X.25 I/O distribution board (DCE RS-232-C) ASP8 apparatus code. Tape Drive I/O distribution AWJ24 apparatus code. CPMML-HS, FRM, TRK- board (ECPU con®guration) PQ, TSM-T1, X.25P, and X.75 I/O distribution board (DTE V.35) ASPEN Automated System for Performance Evaluation of Networks (OSS) AWJ32 apparatus code. SAMML I/O distribution board (DTE V.35) Async protocol abbrev. asynchronous transmission AWJ33 SWT I/O distribution board AT address translation; abatement threshold (SMDS) (G.703/G.704/G.706 DTE) ATM asynchronous transfer mode AWG American Wire Gauge AWJ2 apparatus code. CPM-HS and TRK-HS I/O B distribution board (®ber) B3ZS Bipolar Three Zero Substitution (SMDS) AWJ3 apparatus code. SFT I/O distribution board B8ZS Bipolar Eight Zero Substitution (SMDS) AWJ4 apparatus code. TRK-T1 (V.35 or RS-449), MSM (RS-232-C), and TY12 (RS-232-C) I/O BA balanced asynchronous distribution board BAC bandwidth assurance counter (SMDS) AWJ5 apparatus code. SDLC8, SYNC8, TSM8, and BAF Bellcore AMA Format (billing) X.25 I/O distribution board (DCE RS-232-C or DTE V.35) BAS Backplane Receiver and Address Screener AWJ6 apparatus code. SDLC8, SYNC8, TSM8, and BAsize buffer allocation size X.25 I/O distribution board (DTE RS-232-C or DTE BBE background block error (SMDS physical layer) V.35) BBER background block error ratio (SMDS physical AWJ7 apparatus code. SDLC8, TSM8, and X.25 I/O layer); see also ESR, SESR distribution board (DTE RS-232-C, NRZI) BBUP label. battery backup AWJ8 apparatus code. SDLC8, TSM8, and X.25 I/O distribution board (DCE RS-232-C, NRZI) BBUS broadcast bus AWJ9 apparatus code. CPMML, SAMSL, and SWT Bc committed burst (frame relay) I/O distribution board (DTE V.35, optional NRZI) bcc block check character; see also CRC

6 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

BCC blocked calls cleared C

BCD binary coded decimal CAC call admission control; Customer Assistance BDFB battery distribution fuse board Center (AT&T) BDT billing day table CAD/CAE/CAM computer-aided design/computer- aided engineering/computer-aided manufacturing Be excess burst (frame relay) CALLPROC call processing (software subsystem) BECN backward explicit congestion noti®cation (frame relay) CAROT Centralized Automatic Reporting on Trunks (OSS) BER bit error rate CAS Craft Access System (OSS) BEtag beginning-end tag CBDS Connectionless Broadband Data Service (ETSI BGP Border Gateway Protocol standard for SMDS in Europe) BIOS basic input/output system CBM call back modem (software) BIP bit interleaved parity CBR constant bit rate (ATM) BIP-8 PLCP code violation (CV) CBUS contention bus B-ISDN Broadband±Integrated Services Digital CC0> or CC1> Control Computer prompts Network CC Control Computer; Country Code (E.164 BISYNC abbrev. protocol; also BSC. Binary addressing) Synchronous Communications CCC clear channel capability (SMDS) blks blocks CCIO Control Computer input/output BOM beginning of message (SMDS) CCITT Consultative Committee for International BPI billing period indicator Telegraph and Telephone; see ITU-T bps bits per second COM continuation of message (SMDS) BPV bipolar violation (SMDS) CCOM Concentrator Common Module (ISN) BRG band rate generator CCM Control Computer Module BRI Basic Rate Interface (ISDN) CCS Customer Control System (StarKeeper II NMS) BSC protocol. See BISYNC CD Carrier Detect (RS-232-C signal); see also DCD, BSC3270 See SYNC8 RLSD bss abbrev. sw. block static storage cd abbrev. command. change directory BSSSB Basic Special Services System Breakthrough CDPD Cellular Digital Packet Data (OSS) CDM channel division multiplexer BTAM Basic Telecommunications Access Method (IBM); see also VTAM CDMA Code Division Multiple Access

BTR bus terminating resistor CEPT Conference of European Postal and BWM broadcast warning message Telecommunications Administrations BYT billing year table CFA carrier failure alarm (SMDS)

Data Networking Products Terminology, Issue 4 7 ______Abbreviations and Acronyms

CEY1 apparatus code. HS-TRK and TRK-HS I/O CMA15 apparatus code. GAR circuit pack distribution board (®ber) CMA16 apparatus code. TRK-T3I (ingress) circuit CEY2 apparatus code. SAMSL I/O distribution board pack (V.35) CMA17 apparatus code. AI-T3P (ingress and egress) CEY3 apparatus code. SAMSL I/O distribution board circuit pack (3 meg) (DTE RS-232) CMA18 apparatus code. TRK-E3A (ATM E3) and CEY4 apparatus code. SAMDL I/O distribution TRK-T3A circuit pack board CMC2 apparatus code. CIM I/O distribution board CGA color graphics adapter CMC3 apparatus code. SSM4 I/O distribution board ChE1 channelized E1 (frame relay) CMC5B apparatus code. AI-T1 I/O distribution ChT1 channelized T1 (frame relay) board CIB CRC32 indication bit CMC6 apparatus code. AI-T3, TRK-T3, and TRK- T3S I/O distribution board CIC carrier identi®cation code (SMDS); Customer Information Center (AT&T) CMC6B apparatus code. AI-T3, AI-T3P (egress), TRK-T3, TRK-T3I (egress), and TRK-T3S I/O CICS Customer Information Control System (IBM) distribution board CIM committed information rate (frame relay, ANSI CMC8 apparatus code. AI-E1 I/O distribution board T1.606a-1992, Annex A) CMC13 apparatus code. AI-E3, TRK-E3, and TRK- CIU Communications Interface Unit (Amdahl) E3S I/O distribution board CLEI Common Language Equipment Identi®er CMC13B apparatus code. TRK-E3S I/O distribution (Bellcore equipment code equipment code) board CLNAP Connectionless Network Access Protocol CMC14 apparatus code. AI-T3P (ingress), GAR, and (ITU standard for the connectionless service layer) TRK-T3I (ingress) I/O distribution board CLNP Connectionless Network Protocol (OSI) CMC15 apparatus code. TRK-T3A I/O distribution CLNS connectionless network service; see also CONS board CLP cell loss priority (ATM) CMC16 apparatus code. TRK-E3A I/O distribution board CM community CMC17 apparatus code. FRM-M2 channelized T1 CMA1 apparatus code. Switch (ESWTCH) module I/O distribution board; TRK-E3A I/O distribution CMA2 apparatus code. CIM circuit pack board CMA5 apparatus code. AI-E1 and AI-T1 circuit pack CMC18 apparatus code. FRM-M2 channelized E1 I/O distribution board (75 Ohms) CMA9 apparatus code. TRK-T3 circuit pack CMC19 apparatus code. FRM-M2 channelized E1 CMA9B apparatus code. TRK-E3 and TRK-T3 I/O distribution board (120 Ohms) circuit pack cmd abbrev. sw. command CMA11B apparatus code. AI-E3 and AI-T3 circuit pack CMIP Common Management Information Protocol (ISO/IEC 9596) CMA13 apparatus code. TRK-E3S and TRK-T3S CMIS Common Management Information Service circuit pack (ISO/IEC 9595) CMA14 apparatus code. TRK-T3I (egress) circuit CMISE Common Management Information Service pack Element (SMDS)

8 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

CMOT CMIP over TCP/IP CRA1 apparatus code. SAM16 I/O distribution board (DTE V.35/V.11 trunk interface) CMS-1C Circuit Maintenance System±1C (OSS) CNA1 apparatus code. Intershelf Cable/Clock I/O CRA2 apparatus code. SAM16 I/O distribution board distribution board (ICCIOB) for Control Computer (DCE RS-232-C trunk interface) slot A in BNS-2000 Series M2 Switch Shelf CRAS Cable Repair Administrative System (OSS) CNA2 apparatus code. Extension Intershelf CRC cyclic redundancy check Cable/Clock I/O distribution board (ECCIOB) for Control Computer slot A in a BNS-2000 Series M2 CRC4 cyclic redundancy check 4-bit Extension Shelf CRC32 cyclic redundancy check 32-bit CNC Customer Network Controller (OSS) CRI CPE receive interval CNCC Customer Network Control Center (OSS) CRSAB Centralized Repair Service Attendant Bureau CNM customer network management (SMDS) (OSS) CO central of®ce CRT1 apparatus code. BNS-microSwitch Trunk Board CO-ACCESS central of®ce access CRT2 apparatus code. BNS-microSwitch Customer CO-LAN central of®ce Interface Board CO-MAN central of®ce metropolitan area network CRTC Canadian Radio±Television and CO-OS Central Of®ce Operations Systems Telecommunications Commission COM continuation of message CS cabling speci®cations; channel set; convergence sublayer; current state (measurements) con®g abbrev. con®guration CSACC Customer Service Administrative Control CONS connection-oriented network service; see also Center (OSS) CLNS CSCANS Customer Service Computer Access COSMOS Computer System for Mainframe Network Standard Operations (OSS) CSC Common Signaling Channel (SMDS); Common CP customer premises Supervision Channel; Customer Support Center CPAC Customer Planning and Consultation (AT&T) CPC circuit provisioning center (OTC) CSD1 apparatus code. FRM (ChT1) I/O distribution board CPE customer premises equipment CSD2 apparatus code. FRM (ChE1) I/O distribution CPM-HS Computer Port Module±High Speed board (75 Ohms) CPMML Computer Port Module Multiple Link CSD3 apparatus code. FRM (ChE1) I/O distribution CPMML-HS Computer Port Module Multiple board (120 Ohms) Link±High Speed CSD4 apparatus code. X.25P I/O distribution board CPS calls per second (8 DCE/DTE RS-232-C ports) CPU central processing unit CSD6 apparatus code. LPM I/O distribution board CPW1 apparatus code. SAM16 circuit pack CSD9 apparatus code. Tape Drive I/O distribution CPW2 apparatus code. BNS-microSwitch Main board (TN2233 [DDS] or TN2097) Board CPY1 apparatus code. SAM16 I/O distribution board CSMA/CD protocol. Carrier Sense Multiple Access (DTE RS-232-C) with Collision Detect ()

Data Networking Products Terminology, Issue 4 9 ______Abbreviations and Acronyms

CSS controlled slip second (SMDS) DCD Data Carrier Detect (RS-232-C signal); see also CD, RLSD CSU channel service unit CTG5 apparatus code. FRM-M2 DCE data communications equipment (usually, a modem) CTH1 apparatus code. FRM-M2 mezzanine board DCN data communications network (SMDS) CTRM Clock/Trunk/Repeater Module; terminal emulation software (AT&T) DCOS Data Collection Operation System (OSS) CTS Clear To Send (RS-232-C signal) DC PS DC Power Supply module CTS1 apparatus code. MRC I/O (MRCIO) DCX1836 apparatus code. DC Power Supply module distribution board DDCMP Digital Data Communications Message CTS2 apparatus code. CCM I/O distribution board Protocol (synchronous) (shelf-to-shelf connections without MRC DDD Direct Distance Dialing functionality) apparatus code. DDM Digital Data Multiplexer CU control unit DDN Defense Data Network, proprietary PDN for the CUG closed user group (X.25 security) Department of Defense; see also ARPANET, CV code violation(s) DARPA, NSFNET C-VDM central (of®ce) voice/data multiplexer DDP Datagram Delivery Protocol (AppleTalk routing) CVG convergence DDS Digital Data System (56 Kbps); Digital Data Storage cartridge (for CCM con®guration tape drive) DE discard eligibility (frame relay congestion D management bit) D4 framing mode on T1 facilities diag abbrev. command. diagnostics DA destination address (SMDS) DIAG label. diagnostics (control or interface module switch position for a diagnostics subsystem of Control DACS Digital Access Cross-Connect System Computer software) DARPA Department of Defense Advanced Research DIP dual in-line package (switch) Projects Agency; see also ARPANET, DDN, NSFNET DISAB label. disable (control or interface module switch position) DAS dual attached station (FDDI) DISTR distribution (software subsystem) db or DB database DIW D-inside wire dB decibel DL data link DBG debugger, Control Computer process and command mode DLCI data link connection identi®er (frame relay) D-bit delivery con®rmation bit (in X.25 data packet); DLL data link layer see also M-bit, Q-bit DM degraded minute DBM Data Bus Monitor DMA direct memory access DBMS database management system DMPDU Derived Media Access Control Protocol Data DC direct current; device controller Unit (SMDS) DCC Data Communication Channel; Data Country DN distinguished name (SMDS) Code (®rst 3 digits of a DNIC)

10 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

DNCC Data Network Control Center (OTC) E1 digital transmission link with 2.048 Mbps of bandwidth capacity; wire trunk (CEPT) DNI dialed number identi®cation DNIC Data Network Identi®cation Code E2A protocol. asynchronous telemetry standard (CO); asynchronous telemetry module (4-port) DNS Domain Name Server E3 digital transmission link with 34 Mbps bandwidth DOSS Direct Order Service System capacity; wire trunk (CEPT) DPC Data Processing Center E4 digital transmission link with 274.176 Mbps DPMS Data Processing Management System bandwidth capacity (CEPT) DQDB CLNS Media Access Control (MAC) protocol. EA extended address (SMDS) Distributed Queue Dual Bus (IEEE 802.6) DRAM dynamic random access memory EADAS Engineering and Administration Data Acquisition System (OSS) DS Digital Signal (ANSI/CCITT/ITU-T); digital service EB errored block (SMDS physical layer)

DS0 Digital Signal, Level 0 (ANSI/CCITT/ITU-T) EBAS Enhanced Backplane Address Screener DS1 Digital Signal, Level 1 (ANSI/CCITT/ITU-T) EBCDIC protocol. Extended Binary-Coded Decimal DS3 Digital Signal, Level 3 (ANSI/CCITT/ITU-T) Interchange Code

DSG default slot generator (SMDS) EBIM Ethernet Bridge Interface Module (ISN) DSIS Data Switching Information System EC Entering Congestion (FRM buffer memory use) DSL Digital Subscriber Loop ECC error checking and correction DSR Data Set Ready (RS-232-C signal) ECCIOB Extension Shelf Cable/Clock I/O DSU data service unit distribution board (BNS-2000) DSX-1 Digital Signal Cross-Connect, Level 1 (ANSI T1.403) ECPU enhanced central processing unit DTE data terminal equipment ED2P465-30, G1 apparatus code. T1-TRK I/O distribution board (SAM504 only) DTF digital transmission facility (DS1/DS3) DTR Data Terminal Ready (RS-232-C signal) ED2P466-30, G1 apparatus code. TERM32 I/O distribution board (SAM504 only) DUART dual universal asynchronous receiver/transmitter (integrated circuit) ED2P471-30, G1 apparatus code. HS-TRK I/O distribution board (®ber) DUSART dual universal synchronous/asynchronous receiver/transmitter (integrated circuit) ED2P472-30, G1 apparatus code. HS-TRK I/O distribution board (®ber) DXI Data Exchange Interface, "Dixie" (SMDS) ED5P066-30, G1 apparatus code. TY6 I/O DXI/SNI Data Exchange Interface/Subscriber Network distribution board Interface (SMDS) ED5P074-30, G1 apparatus code. E2A I/O distribution board E ED5P077-30, G1 apparatus code. SLM I/O distribution board E.nnn CCITT/ITU-T symbol. Series E Recommen- dations for the telephone network and ISDN ED5P1000-30, G194 apparatus code. LPM I/O distribution board

Data Networking Products Terminology, Issue 4 11 ______Abbreviations and Acronyms

EDH European Digital Hierarchy F

EDOS event-driven FA1/FA2 Frame Alignment signal (E3 frame overhead byte) EEPROM electrically erasable programmable read- only memory; see also EPROM, FEPROM, PROM, FBUS from (the switch) bus ROM FBX From-Backplane Transformer EF&I engineer, furnish, and install FC ¯ow control EGA enhanced graphics adapter FCC Federal Communications Commission EGP External Gateway Protocol (routing) FCS frame check sequence EIA Electronic Industries Association FDDI Fiber Distributed Data Interface (ANSI) EISA Extended Industry Standard Architecture FDM frequency division multiplexing ELIU electrical line interface unit FE frame (synchronization) error; far end (SMDS) EM error monitoring BIP-8 (E3 frame overhead byte) FEBE far-end block error EMC electromagnetic compatibility FECN forward explicit congestion noti®cation (frame EMI electromagnetic interference relay) EMS Element Management System FEP front-end processor ENABL label. enable (control or interface module FERF far-end receive failure switch position) FIFO ®rst in, ®rst out EOM end of message (SMDS) FIM Fiber Interface Module (ISN) EP endpoint FMAC Facility Maintenance Administration Center EPN endpoint number (X.121) (OTC) EPROM erasable programmable ROM FP framed path (SMDS) EQL (line) equalization FPM frequency packet multiplexing ES errored second FEPROM ¯ash erasable programmable ROM ESD electrostatic discharge FPS framing pattern sequence ESDI Enhanced Small Device Interface FR frame relay

ESF extended superframe (T1 format) FRAD frame relay assembler/disassembler; see also PAD ESIG European SMDS Interest Group FRM Frame Relay Module (Datakit II VCS/BNS- ESR errored second ratio (SMDS physical layer) 2000 Series M1 shelf) FRM-M2 Frame Relay Module±M2 (BNS-2000 Series ESS electronic switching system M2 shelf) ESWTCH label. Eswitch module frport software parameter. LPM virtual frame relay port ETS external timing source (SMDS) frs abbrev. command object. full remote shelf ETSI European Telecommunications Standards (MPC15) Institute fsck command. ®le system check

12 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

FSK Frequency Shift Keying HLPI higher layer protocol identi®er (SMDS) FT fault tolerant HOB head of bus FT1 fractional T1 HP Hewlett-Packard

FT-2000 Fiber Terminal 2000 (transmission system) HPAD host packet assembler/disassembler HPQ high-priority transmit queue; see also LPQ FTAM File Transfer Access Management HSS8 High Speed Serial 8 FTDM Flow Through Data Manager (OSS) HSSI high-speed serial interface FTP ®le transfer protocol HS-TRK High Speed±Trunk (link) module (in SAM64/504) G GA generator to aggregator I

GAA Group Address Agent (SMDS carrier) I.nnn CCITT/ITU-T symbol. Series I GAR Group Address Resolver module (BNS-2000 Recommendations for Integrated Services Digital SMDS) Network (ISDN), or GB gigabyte(s) I-2000 generic name. DACS II Element Management System (EMS) Gbps gigabits per second (1 × 109 bits per second) IA5 international alphabet GID group identi®cation I&M installation and maintenance GND or GRND abbrev. ground (electrical) IAC Integrated Access Controller GNE Gateway Network Element IARP Inverse ARP (RFC 1490) GOS grade of service IC Interexchange Carrier (SMDS); see also IXC GOSIP (U.S.) Government OSI Protocol ICCIOB Intershelf Cable/Clock I/O distribution board GSDN Global Software De®ned Network (BNS-2000) GUI graphical ICI Inter-Carrier Interface (SMDS) GW gateway ICI-LEC Inter-Carrier Interface±Local Exchange Carrier (SMDS) H ICIP Inter-Carrier Interface Protocol (SMDS) ICMP HBPP heart beat polling process (frame relay) Control Message Protocol (TCP/IP) ICN HCS header check sequence (SMDS) international CUG number (international interlock code, addressing) HDB3 high density bipolar of order 3 (FRM/ChE1 ID line coding) identi®cation; identi®er; see also GID, PID, UID, XID HDLC protocol. High Level Data Link Control (ISO IDLC 4335/1984) Integrated IEC HE header extension (SMDS) International Electrotechnical Council IEEE HEC header error control (SMDS) Institute of Electrical and Electronics Engineers iep HEL header extension length (SMDS) internal endpoint

Data Networking Products Terminology, Issue 4 13 ______Abbreviations and Acronyms

IETF Internet Engineering Task Force K

IHL Internet Header Length (IP header) KB kilobyte(s) IIC international interlock code Kbps kilobits per second IMPDU Initial Media Access Control (MAC) Protocol Kft kilofeet Data Unit (IEEE 802.6) KHz kilohertz IMS Information Management System (IBM) km kilometer(s) INIC International Network Identi®cation Code (addressing) init abbrev. command. initialize L INP internet nodal processor L2 Level 2 INS Information Networking Services (SMDS) L3 Level 3 I/O input/output L2-PDU Level 2 Protocol Data Unit (SIP/SMDS) IP (a datagram protocol) L3-PDU Level 3 Protocol Data Unit (SIP/SMDS) IPC interprocess communications LAC Line Assignment Center (OTC) IPX protocol. Internet Packet Exchange (Novell) LADC FCC standard. Local Area Data Channel ISDN CCITT/ITU-T Recommendation. Integrated LAN local area network Services Digital Network lanport software parameter. LPM physical local area IS-IS protocol. Intermediate System to Intermediate network port System (TCP/IP and OSI routing) LAPB CCITT/ITU-T Recommendation. Link Access ISN Information Systems Network (AT&T) Procedure Balanced (X.25) ISO International Standards Organization LAPD CCITT/ITU-T Recommendation. Link Access Procedure (on the) D-channel (ISDN) ISP Information Services Platform LAPF CCITT/ITU-T Recommendation. Link Access ISSI Inter-Switching System Interface (SMDS) Procedure for Frame Mode Bearer Services (frame ITCO Independent Telephone Company; see also relay) OTC, RBOC LAPM CCITT/ITU-T Recommendation. Link Access ITI Interactive Terminal Interface Procedure for Modems (error control) ITS Integrated Test System (OSS) LAPX CCITT/ITU-T Recommendation. Link Access Procedure for half-duplex operations; half-duplex ITU-T International Telecommunications version of LAPB Union±Telecommunications LATA Local Access and Transport Area IVD integrated voice and data LBO line build out IVR interactive voice response LPBK loopback IXC Interexchange Carrier; see also IC LC Leaving Congestion (FRM buffer memory utilization)

J LCG logical calling group

J1P186N-1 apparatus code. SAM16 circuit pack LCH logical channel (number)

14 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

lcl local (group) M2 Series M2 shelf (BNS-2000)

LCN logical channel number (X.25) M2CHIO Series M2 channelized I/O distribution LCS LAN Communication System(s) board (BNS-2000) LCS> system prompt. LAN Communication System MA Maintenance and Adaptation (E3 frame overhead byte) LCV line code violation (SMDS physical layer) MAC protocol. Media Access Control (IEEE 802); LD logical device Master Alarm Collector (StarKeeper II NMS) LEC Local Exchange Carrier Macstar Memory Access Controller±Star (OS) LED light-emitting diode MAN Metropolitan Area Network LES line errored seconds (SMDS physical layer) MAPDU Management Application Protocol Data Unit LIM Link Interface Module (SMDS) LIS Logical IP Subnetwork; loss of incoming signal MAR maximum arrival rate (SMDS threshold) LIV link integrity veri®cation MAU Multistation Access Unit (IBM Token Ring) LKDS link down seconds MB megabyte(s) LLC logical link control M-bit more-data bit (in X.25 data packet) LMI Local Management Interface (frame relay) Mbps megabits per second (1,000,000 bits per second) LMOS/WM Loop Management Operations System/Work Manager (OS) MC machine congestion LOF loss of frame MC1, -2, -3 machine congestion, level 1, -2, or -3 LOS loss of signal MC1D085A-1 apparatus code. SFT circuit pack

LPQ low-priority transmit queue; see also HPQ MC1D088A-1 apparatus code. TSM8 circuit pack LPM LAN Protocol Module MC1D089A-1 apparatus code. SYNC8 circuit pack LRC longitudinal redundancy check; see also CRC, VRC MC1D090A-1B apparatus code. SAMSL circuit pack ls abbrev. command. list MC1D106A-1 apparatus code. SAMDL circuit pack LSB least signi®cant bit MC1D116A-1 apparatus code. SDLC8 circuit pack LSES line severely errored seconds (SMDS physical layer) MC1D117A-1 apparatus code. CPMML circuit pack LSI large-scale integration MC1D138A-1 apparatus code. ECPU circuit pack LSN logical session number MC1D139A-1 apparatus code. CPMML-HS circuit pack LSS link status signal (SMDS) MC1D143A-1 apparatus code. FRM circuit pack LTDM Lightwave Time Division Multiplexer MC1D149A-1 apparatus code. TSM-T1 circuit pack LU logical unit MC1D151A-1 apparatus code. X.75 circuit pack

MC1D152A-1 apparatus code. TRK-PQ circuit pack M MC1D153A-1 apparatus code. X.25P circuit pack M1 Series M1 shelf (BNS-2000)

Data Networking Products Terminology, Issue 4 15 ______Abbreviations and Acronyms

MC5P025A-1 apparatus code. SLM circuit pack MRI message receive interval (SMDS) (processor) ms also msec. millisecond MCDU maximum (number of) concurrent data units (SMDS) MSB most signi®cant bit

MCS Module, Channel, Switch MS-DOS Microsoft MCUP Mechanization and Cooperative User Program msec also ms. millisecond

MDF main distribution frame MSG message MSI message send interval (SMDS) MEAS measurements (software subsystem) MSKERR mask error MET Metropolitan Area Network (MAN) Switching System Exchange Termination MSM Multispeed Module MSS Metropolitan Area Network (MAN) Switching MF-AIM Multi-function Asynchronous Interface System Module (ISN) MTBF mean time between failure MFOS Multifunction Operations System (OSS) MTBSO mean time between service outages MHz megahertz MTTR mean time to restore; mean time to repair MIB Management Information Base (SNMP) µP/CLK microprocessor clock MID message identi®er, -cation (SMDS) MUX abbrev. multiplexer MINI-SH system command interpreter. interactive shell MINI-SH> system prompt. interactive shell N MLP multilink protocol NA network administrator MLT Mechanized Loop Test System (OS) NAC Network Access Controller (Network Access Control System) MMOC Minicomputer Maintenance and Operations Center (OTC Data Center) NAI Network Administration Interface (Control Computer software subsystem) MMU Memory Management Unit NANP ITU-T/CCITT X.121 Recommendation. North MOC measure of congestion American Numbering Plan MoU Memorandum of Understanding (CEPT) NB Network Builder (StarKeeper II NMS) MPC7 Multipurpose Concentrator 7-slot NCC National Country Code MPC15 Multipurpose Concentrator 15-slot NCI Network Control Indicator (SMDS) MRC maintenance (remote) and redundancy control NCS National Communications Standards (Federal functions (CCM with MRCIO board) Telecommunications) MRC> system prompt. maintenance and redundancy NCSC National Customer Service Center (AT&T) control functions (CCM with MRCIO board) NDC national destination code; Network Data MRCIO CCM I/O board with MRC functions Collection (SMDS) MRCM Maintenance and Redundancy Control Module NDWB Network Designer's Workbench MRCM> system prompt. Maintenance and NE network element Redundancy Control Module functions

16 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

NE2NE Network Element to Network Element NRZ non-return to zero (signaling) NEBS Network Equipment Building Speci®cation NRZI non-return to zero inverted (signaling) NEMA National Electrical Manufacturers Association N(S)N National (Signi®cant) Number (E.164 addressing) NESD Network Element Software Download (DKAP) NTM (NetMinder) Network Traf®c Management NESPA Network Element Security Parameter (OSS) Administration (SMDS) NTN Network Terminal Number (X.121) netaddr abbrev. NTSO National Technical Support Organization NEU network expansion unit (AT&T) NFS Networked File System NWKFC network ¯ow control NFSNET National Science Foundation Network; see NWT network technology also ARPANET, DARPA, DDN NI network interface; Network Identi®er (last digit of DNIC) O NIST National Institute of Science and Technology OA&M Operations, Administration, and Maintenance (provides NAC time synchronization) OAM&P Operations, Administration, Maintenance, NM network management; network manager; Network and Provisioning Monitor (StarKeeper II NMS) O&SIS Operations and Service Integration System NMA-F Network Maintenance Administration± (OS) Facilities (OSS) OC Optical Carrier (SONET) NMC Network Management Center (SMDS) OC-1 Optical Carrier, Level 1 (SONET) NMI non-maskable interrupt OC-3 Optical Carrier, Level 3 (SONET) NMOL Network Management OPEN LOOK OC-12 Optical Carrier, Level 12 (SONET) NMP Network Management Protocol (AT&T) OC-48 Optical Carrier, Level 48 (SONET) NMS Network Management System OCD Out of Cell Delineation nmsiep Network Management System internal endpoint (StarKeeper II NMS) ODL Optical Data Link NMU Network Mediation Unit (OSS) ONA Open Network Architecture (developed by the FCC) NNI Network-to-Network Interface (frame relay/SMDS); Network Node Interface (ATM) ONI Open Network Interface NOET Network Operations Education and Training OOF out of frame NOS OS Operations System; operating system NPC Network Parameter Control (ATM NNI) OSI Open Systems Interconnection nping network ping (frame relay delay diagnostic); OSN Operations Systems Network see ping OSPF protocol. open shortest path ®rst (TCP/IP and NPSI Switching Interface (IBM) OSI routing) Nr number received OSS Operations Support System(s) NRT node reroute table (session maintenance) OT onset threshold

Data Networking Products Terminology, Issue 4 17 ______Abbreviations and Acronyms

OTC operating telephone company POS Point-of-Sale ppm parts per million P PP physical port PPP Point-to-Point Protocol PAD packet assembler/disassembler PAP permanently active port pps packets per second PBD power board distribution PQ priority queueing; see TRK-PQ

PBX private branch exchange PR page reservation; Performance Reporter PC personal computer (StarKeeper II NMS) PCC page counter control PRI Primary Rate Interface (ISDN, equivalent to DS1 and T1) PCG physical calling group PCM pulse code modulation; page counter modulus PRM performance report measurements (SMDS) PD power distribution PROM programmable read-only memory

PDD prede®ned destination PROV provisioning (software subsystem) PDE portable development environment PRS Primary Reference Source (reference clock) PDH Plesiochronous Digital Hierarchy (international asynchronous standard) PS Packet Service PDN public data network PSC protection switch counts (SMDS)

PDS Premises Distribution System (AT&T Systimax) PSD protection switch duration PDSC power distribution service cabinet PSK Phase Shift Keying (line code or format) PDU Protocol Data Unit (SIP/SMDS) PSP Packet Stream Protocol PE parity error PSPDN packet-switched public data network pF picofarad(s); one-trillionth of a farad PSTN public switched telephone network PFC power factor correction PT payload type (SMDS); port (session maintenance) PI protocol identi®er; Programmer's Interface PTT Post, Telegraph, and Telephone (European (StarKeeper II NMS) governmental carriers) PID pin identi®cation; product identity code PU physical unit PL PAD length PVC permanent virtual circuit PLCP Physical Layer Convergence Procedure (IEEE 802.6) PWR label. power PLOF PLCP loss of frame

PLP packet layer protocol Q

PLPP Physical Layer Protocol Processor Q.nnn CCITT/ITU-T symbol. Series Q Recommendations for telephone signaling and PM performance monitoring (SMDS) switching

POP point-of-presence QAM Quadrature Amplitude Modulation (line code or format)

18 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

Q-bit quali®ed data bit (in X.25 data packet) RMS-D3 Remote Maintenance System±Digital 3 (OSS) QoS Quality of Service (ATM, classes of service in cell relay switching) RMS-DS1 Remote Maintenance System±Digital Signal 1 (OSS) qrs quasi-random signal (frame relay, T1.403) RMS-G1 Remote Maintenance System±Gateway 1 (OSS) R RMS-M Remote Maintenance System±Metallic (OSS) R.nnn Series of Recommended EIA Standards RNMS Regional Network Management System (OSS) RAI Remote Alarm Indicator ROM read-only memory RAM random access memory ROSE remote operation service element (OSI) RAMERRS random access memory (RAM) errors RPC remote procedure call RAO Revenue Accounting Of®ce (OTC billing collection center) RPOA Recognized Private Operating Agency, a data transit network RAP Routing Algorithm Process RPT repeater RBOC Regional Bell Operating Company; see also RR receive ready ITCO RRC rerouted call RC reverse charging rrs abbrev. command object. reduced remote shelf RC or RCLK Receive Clock (RS-232-C signal) (MPC7) RCCM Remote Concentrator Common Module RxSN receive sequence number RCV receive RS&R Repair, Service and Return (AT&T customer RD Receive(d) Data (RS-232-C signal) support service) RDN relative distinguished name (SMDS); see also RTE route table entry (session maintenance) DN RTIC real time interface coprocessor RF radio frequency (noise) RTN or RET return; neutral side of a −48 VDC power RFA remote frame alarm connection RFS Remote File Sharing (UNIX); ready for service RTNR Real Time Network Routing RHC Regional Holding Company RTS Request To Send (RS-232-C signal) RID record identi®er RTT reroute tracking table (session maintenance) RIP Routing Information Protocol (TCP/IP suite) RTU Right-to-Use (software license) RLSD Received Line Signal Detector (RS-232-C R-VDM remote voice/data multiplexer signal); see also CD, DCD RMAS Remote Memory Administration System S (OSS) RMS-D1 Remote Maintenance System±Digital 1 S abbrev. short (cable) (OSS) SA source address (SMDS); Service Area (X.121) RMS-D2 Remote Maintenance System±Digital 2 SAC Service Access Code (SMDS) (OSS)

Data Networking Products Terminology, Issue 4 19 ______Abbreviations and Acronyms

SAM Synchronous/Asynchronous Multiplexer SDLC protocol. Synchronous Data Link Control SAM16 Synchronous/Asynchronous Multiplexer 16- SDLC8 Synchronous Data Link Control 8-port port interface module SAM64 Synchronous/Asynchronous Multiplexer 64- SDS software disk striping (StarKeeper II NMS) port SDU service data unit (SMDS/SIP); synchronous data SAM504 Synchronous/Asynchronous Multiplexer unit 504-port SEF severely errored framing (SMDS) SAMDL Synchronous/Asynchronous Dual Link SEFS severely errored framing seconds (SMDS module physical layer) SAMML Synchronous/Asynchronous Multiple Link SES severely errored seconds (SMDS physical layer); module Spares and Exchange Service (AT&T customer support service) SAMSL Synchronous/Asynchronous Single Link module SES II Service Evaluation System II (OSS) SAP Service Access Point (OSI) SESR severely errored second ratio (SMDS physical layer) SAPI Service Access Point Identi®er (SMDS) SET Switching System Exchange Termination SAR segmentation and reassembly (sublayer) (SMDS) SARTS Switched Access Remote Testing System SF superframe format; see also ESF (OSS) SFT Standard Fiber Trunk (interface module) SAS single attached station SG signal ground SAT subscriber access termination (SMDS) sh abbrev. sw. shell (program) SC0> or SC1> standby Control Computer prompts SI state indication SC standby Control Computer SID Security Identi®cation (ID) SCAI Switch-to-Computer Applications Interface (ANSI) SIG SMDS Interest Group SCAMIS Schedule Control and Maintenance SIM Synchronous Interface Module Information System (OSS) SIP SMDS Interface Protocol (SMDS); Subscriber SCANS Software Change Administration and Interface Protocol (IEEE 802.6) Noti®cation System SIR Sustained Information Rate (SMDS) SCARLET international version of SCAMIS (OSS) SIRIUS Service Information Reporter and Integrator SCC Switching Control Center (CO) for Users System (OSS)

SCCS Switching Control Center System (OSS) SLC Subscriber Loop Carrier; SONET Loop Carrier SCSI Small Computer System Interface SLIM-B StarLAN Bridge Interface Module (ISN)

SCSI/DKI label. on Small Computer System SLIP Serial Line Interface Protocol (TCP/IP) Interface module SLM Synchronous Link Module SDAS Switch Database Administrative System (OSS) SLP Single Link Procedure SDH CCITT/ITU-T Recommendations, G.707/708/709. SM session maintenance Synchronous Digital Hierarchy; see also SONET SMDS Switched Multimegabit Data Service

20 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

SMDS CIC Switched Multimegabit Data Service STP Spanning Tree Protocol (IEEE 802.1); Signal carrier identi®cation code Transfer Point SMTP simple message transfer protocol (OSI) STS Synchronous Transport Signal (SONET) SN Subscriber Number SunOS Sun (Microsystems) Operating System SNA Systems Network Architecture (IBM) SVC switched virtual circuit; service connection(s)

SNAPS Switch Network Analysis Performance SVID System V Interface De®nition (UNIX operating System (OSS) system) SWERR switch error SNAS Signal Network Analysis System (OSS) SWT Standard Wire Trunk (interface module) SNI Subscriber Network Interface (IEEE 802.6/SMDS/ATM) SYN synchronous idle Sync Protocol abbrev. synchronous transmission SNMP Simple Network Management Protocol (Internet/TCP/IP standard) SYNC8 Synchronous 8-port module (BSC3270) SONET ANSI Standard. Synchronous Optical syncp synchronous call process Network; see also SDH SYSERR system error SP Session (layer) Protocol SYSGEN system generation; software subsystem ®le SPDU Session Protocol Data Unit SPM statistical packet multiplexing T SPP Sequenced Packet Protocol (Banyan Vines) SPX protocol. Sequenced Packet Exchange (Novell) 10BASE-T twisted pair Ethernet (IEEE 802.3) SQL Structured Query Language T1 digital transmission link with 1.544 Mbps capacity; wire trunk SR special report (SMDS); Service Region (X.121) T1C digital transmission link with 3.10 Mbps SRI SIP Relay Interface (SMDS) capacity; wire trunk SRS Secondary Reference Source (reference clock) T3 digital transmission link with 45 Mbps capacity (28 SRT source routing transparent T1 channels); wire trunk srvc abbrev. sw. service; service state T3POST/VISA 90 protocol. Terminal link level standard for connections between subscribers and SS Switching System (MAN) information providers, used in credit card veri®cations SS7 CCITT/ITU-T Recommendation. Signaling (DKAP) System 7 TA terminal adapter (SMDS CPE interface module; SSC Special Service(s) Center (OTC); Service ISDN); Technical Advisory (Bellcore) Support Centers (AT&T) TACACS Terminal Access Controller Access Control SSM single segment message (SMDS) System (LCS60E security) SSM4 Stratum 4 Clock module TBC Time Beginning Call TBUS transmit (to) bus SSS SMDS Switching System TBX To-Backplane Transformer ST segment type (SMDS) TC or TCLK transmit clock; to clock STM synchronous transfer mode TCA threshold crossing alert (SMDS)

Data Networking Products Terminology, Issue 4 21 ______Abbreviations and Acronyms

TCC Telephone Country Code (X.121 addressing) TN2092B apparatus code. SWT circuit pack TCP Transmission Control Protocol TN2094 apparatus code. X.25 circuit pack TCP/IP Transmission Control Protocol/Internet TN2096 apparatus code. CTRM circuit pack Protocol TN2097 apparatus code. Tape Drive circuit pack TD transmit data (ECPU con®guration) TDC Telex Destination Code (X.121 addressing) TN2098 apparatus code. Disk Drive circuit pack (ECPU con®guration) TEC Time End Call TN2099 apparatus code. enhanced Switch module TDM Time Division Multiplexing circuit pack (ESWTCH) TDMS Traf®c Data Management System (OS) TN2109C apparatus code. MRCM circuit pack TDSI Transit Delay Selection and Indication (X.25P TN2111B apparatus code. MSM circuit pack port parameter) TN2157 apparatus code. TY12 circuit pack TEI terminal endpoint identi®er (SMDS) TN2175 apparatus code. Disk Drive circuit pack TERM32 module (in SAM64/504s) (ECPU con®guration) TIM Trunk Interface Module (ISN) TN2175B apparatus code. Disk Drive circuit pack TM Task Manager (StarKeeper II NMS) (ECPU con®guration) TMAS Transport Maintenance and Administration TN2233 apparatus code. Tape Drive (CCM System (OSS) con®guration) TMN telecommunications management network TN2229 apparatus code. LPM circuit pack (ISDN) TN2235 apparatus code. Control Computer Module TN1001B apparatus code. Clock circuit pack (in (CCM) MPCs) TNM Total Network Management (OS) TN1002B apparatus code. Switch circuit pack (in TNS Total Network Surveillance (OSS); see also MPCs) SCCS, TNM TN1006 apparatus code. TY6 circuit pack TOBUS to (the switch) bus; see also TBUS TN1009B apparatus code. CPM-HS circuit pack TOPAS Testing, Operations, Provisioning, and TN1010 apparatus code. TRK-HS circuit pack Administrative System (OSS) TN1011D apparatus code. TY12 circuit pack TOS Type of Service (IP header) TN1012 apparatus code. E2A circuit pack TP termination point TN1013 apparatus code. CPM-422 circuit pack TPAD Terminal PAD TN1015 apparatus code. TRK-T1 circuit pack TR Technical Reference (Bellcore); terminal ready; Token Ring; trouble report; tracking report; Trail TN1016B apparatus code. SYNC8 circuit pack Trace (E3 frame overhead byte) TN1391 apparatus code. HS-TRK circuit pack (in TRAC TCP/IP Remote Access Controller (Datakit II SAMs) VCS/BNS-2000 IP product) TN1392 apparatus code. T1-TRK circuit pack (in TRK abbrev. trunk SAMs) TRK-E3 Trunk-E3 module (connection-oriented and TN1394B apparatus code. TCONB circuit pack (in connectionless interface) SAMs)

22 Data Networking Products Terminology, Issue 4 ______Abbreviations and Acronyms

TRK-E3A Trunk-E3 module for asynchronous UART universal asynchronous receiver/transmitter transfer mode (E3 interconnection between BNS-2000 (integrated circuit) and ATM switches) UAS unavailable seconds (SMDS physical layer) TRK-E3S Trunk-E3 Screening module (connection- UAT unavailable time (SMDS) oriented and connectionless SMDS ICI) TRK-HS Trunk±High Speed module (®ber interface) UDLC Universal Data Link Control TRK-PQ Trunk±Priority Queueing module (wire UDP (TCP/IP) interface) UI unit interval (SMDS); unacknowledged information TRK-T1 Trunk-T1 module (wire interface) UID user identi®cation TRK-T3 Trunk-T3 module (connection-oriented and UIS Universal Information Services connectionless interface) TRK-T3A Trunk-T3 module for asynchronous transfer UL Underwriters Laboratories mode (T3 interconnection between BNS-2000 and UMA usage measurement adjunct (SMDS) ATM switches) UMA/T Usage Measurement Adjunct/Transmitter TRK-T3I Trunk-T3 ICI module (connectionless SMDS) UMT usage measurement transmitter TRK-T3S Trunk-T3 Screening module (connection- UN221 apparatus code. SLM oriented and connectionless SMDS ICI) UN315 apparatus code. TERM32 module TRLR trailer UN635B apparatus code. SCSI/DKI module trm terminal emulation software (StarKeeper II NMS) UNI User Network Interface (ANSI/CCITT/ITU-T; TSM8 Transparent Synchronous Module±8 port ATM/SMDS) TSM-T1 Transparent Synchronous Module±T1 UNIXP UNIX Operating System Protocol (CommKit Host Interface Software) TSV technical services UNMA Uni®ed Network Management Architecture TSY technology systems (AT&T standard) TTBUS total transmit bus UPC Usage Parameter Control (ATM UNI) TTL transistor-to-transistor logic; Time to Live (IP UPS uninterruptible power supply header) URP Universal Receiver Protocol (AT&T) TTY teletype terminal USART universal synchronous/asynchronous TUI terminal user interface receiver/transmitter (integrated circuit) TxSN transmit sequence number USI user system interface (SMDS) TY Terminal Module (asynchronous interface); utilsh abbrev. sw. utility shell asynchronous terminal; terminal port UTS UNIX (Universal) Time-sharing System TY6 Terminal Module 6-port (asynchronous interface) (Amdahl) TY12 Terminal Module 12-port (asynchronous interface) V

U V.nnn ITU-T/CCITT symbol. Series V Recommendations for data communications over the UAI Uniform Alarm Interface (StarKeeper II NMS) telephone network

Data Networking Products Terminology, Issue 4 23 ______Abbreviations and Acronyms

VAC volts alternating current XA-SMDS Exchange Access SMDS (inter-LATA SMDS) VAX minicomputer (DEC) XDR external data representation (TCP/IP) VBR variable bit rate XID exchange (station) identi®er VC virtual circuit; virtual channel (ATM) XLG load generator VCI virtual circuit identi®er; virtual channel identi®er (ATM) XMIT or XMT transmit VCS Virtual Circuit Switch XNS

VDC volts direct current XON/XOFF transmitter on/transmitter off (¯ow VDM voice/data multiplexer control for asynchronous transmission) VDT video display terminal XPC X.25 Protocol Converter Chip VGA video graphics adapter VLP Virtual Line Protocol Z VME Versa Modula Europa ZBTSI zero byte time slot interchange (SMDS) VP virtual path (ATM); virtual port ZCS zero code suppression VPI virtual path identi®er (ATM) VRC vertical redundancy check; see also CRC, LRC VS abbrev. sw. version (®rmware/software) VT Virtual Terminal (OSI service) VTAM Virtual Telecommunications Access Method (IBM); see also BTAM VTOC Volume Table of Contents (disk layout) VUE Visual User Environment, Hewlett-Packard (StarKeeper II NMS)

W

WAN WIC wire center (OTC) W(O)C work center (OTC Data Center) WS workstation

X

X.nnn ITU-T/CCITT symbol. Series X Recommendations for data communications networks XA-OM Exchange Access Operations Management (SMDS)

24 Data Networking Products Terminology, Issue 4 ______

Glossary

In a de®nition, a term printed in bold type is a cross-reference to a main entry.

A ACCUNET Packet Service AT&T X.25 public packet-switched network. A/B switch An electronic switch, installed between an MPC or SAM and a duplicated trunk to a Datakit ACD cabinet Alternating current distribution cabinet; II VCS node. The switch automatically monitors the see Base Power Unit. status of both legs of the duplicated trunk, and active channel set (CS) For session maintenance, a switches over to the standby when a failure is detected set of channels that is con®gured to transport data. in the active link. The node is unaware of the switch. address An identifying code for a physical Access Class The maximum data rate at which a component in a network (a physical address) or for a subscriber is allowed to input data into the SMDS service that end users can access (service address). network. address balancing Also load sharing. A method of access DQDB The SMDS protocol layer distributing traf®c to a remote node when equidistant (Distributed Queue Dual Bus [DQDB]) used on the paths (having the same trunk weight) to the node Subscriber Network Interface (SNI). exist; see also EPN hash value. Access Interface (AI) Node-resident modules that address resolution A method for resolving support T1/T3 and E1/E3 access from LANs or discrepancies in computer addressing schemes. WANs to the node for SMDS. address screening An SMDS feature that checks Access Interface±E1 (AI-E1) A module that individual addresses and group addresses and allows provides CEPT E1 access to the node for SMDS or disallows access for data transmission based on applications. address permissions. Access Interface±E3 (AI-E3) A module that address screening table A list of source and provides CEPT E3 access to the node for SMDS destination addresses (SAs/DAs) in the node database applications. for permissible transmission paths. Access Interface±T1 (AI-T1) A module that provides T1 (DS1) access to the node for SMDS. Adjunct/Switch Application Interface (ASAI) An interface between a computer providing Access Interface±T3 (AI-T3) A module that applications as an adjunct processor and a PBX of a provides T3 (DS3) Class 1±5 access to the node for CO switch; generically described as switch-to- SMDS. computer networking. Access Interface±T3P (AI-T3P) A two-board, administration mode See operations mode. high-performance module that provides T3 (DS3) Class 1±5 access to the node for SMDS, with separate Alarm Relay Unit (ARU) abbrev. sw. aau for alarm ingress and egress paths. activator unit. A peripheral device for a node access path A path that connects equipment at the cabinet/shelf that provides audible and visible relay customer premises with the SMDS Switching System closures for major and minor alarms; it is driven by (SSS). signals from the Control Computer ports. ACCUNET DATAPHONE Data Service Private-line alarm threshold A de®ned level, when an error has digital service with data rates from 2.4 to 56 Kbps, occurred more than a speci®ed number of times, that using digital transmission. activates certain alarms.

Data Networking Products Terminology, Issue 4 25 ______Glossary

alias An alternative network-, area-, or exchange- ATM trunk See Trunk-T3A/E3A (TRK-T3A/E3A). level name for a node in the same network, area, or attention character A de®ned, single element of a exchange as other nodes. network attention signal that causes the Control alternate mark inversion (AMI) A bipolar line Computer to respond with the action de®ned. code or format in which successive 1s are transmitted autobaud detection An automatic routine that as alternating positive and negative signals of equal allows an asynchronous terminal to set its network amplitude, and 0s are transmitted as zero amplitude. interface port at connection time without a alternate routing The association of multiple groups prespeci®ed port baud rate; see also host autobaud. of network trunks with a single service address, autodialer See dialer. allowing the network to select alternate communication paths on call setup (connection- Automated Cable Expertise (ACE) System A oriented service); see also session maintenance. microcomputer-based Operations System (OS) used by a telephone company to troubleshoot cable American Standard Code for Information problems. Interchange (ASCII) A standard established by ANSI that represents characters, numbers, punctuation automatic alternate routing (AAR) See alternate marks, or signals and uses seven on/off bits plus a routing and session maintenance. parity bit to achieve compatibility among data automatic protection switching (APS) The services; see Table 1. transfer of live calls to another link when a trunk fails. A port See port A. automatic reboot The automatic restarting of the Control Computer when power is restored after a area Part of the destination (code) used in an failure or when the system experiences serious address; similar to a telephone area code. The second problems; see also boot. level in an address hierarchy (network, area, exchange, local), correlating to an X.121 service automatic recovery In a node with a Maintenance region. and Redundancy Control Module (MRCM) or an MRCIO, automatic routines run to reboot a Control assisting node For session maintenance, a one-hop Computer or to switch to a standby Control Computer or two-hop neighbor node to a primary node that can if a critical component fails. be requested to participate in rerouting data. automatic switchover In a node with a asynchronous transmission abbrev. async. Maintenance and Redundancy Control Module Transmission, usually in ASCII, in which the time (MRCM) and dual Control Computers, a change from between characters may be of unequal length, and that the active to the standby Control Computer, which is controlled by start and stop bits at the beginning then becomes active. and end of each character; also a standard for this kind of transmission, which supports "dumb" autoreboot See automatic reboot. terminals and often omits error correction. autoresize A database utility that generates a new set asynchronous data unit (ADU) 1. A limited- of table sizes based on the current usage of each distance modem used in pairs to extend the range of database table, rather than requiring the use of a the asynchronous signaling distance. 2. A device that prede®ned template. converts EIA digital signals into signals with lower autorestore The automatic restoration of a voltages, compatible with LADC II requirements. concentrator to service after a link failure is cleared. asynchronous transfer mode (ATM) Also cell relay. A and multiplexing technique de®ned by the ATM Forum for broadband access to B ISDN that uses a packet of ®xed length (53 bytes including 5 header bytes) and operates at higher babbling port A malfunction of an interface module speeds; asynchronous means the cells are received or attached equipment that generates a continuous intermittently, not on a regular basis; see also fast sequence of 25 or more attention signals, which can packet multiplexing. overload the Control Computer and reduce the call connection rate.

26 Data Networking Products Terminology, Issue 4 ______Glossary

backbone network A set of nodes and transmission Billdats Network Server for the BNS-2000 facilities designed to interconnect lower speed Switch A data collection system that interfaces with distribution channels or clusters of dispersed user network elements or services to generate Automated devices over a high-speed network. Message Accounting (AMA) billing records and teleprocess data to the Billdats II Collector. backhaul To provide a user connected to a local central of®ce (CO) with the services of a remote CO billing See call accounting. via normal transmission; the user is unaware of the bipolar signaling A signaling method used for connection beyond the local CO. digital transmission services (DDS and T1), in which backplane A bus (common circuit board) in a node the signal carrying the binary value successively to which all control and interface modules connect. alternates between positive and negative polarities. backplane module Also resident module. An bisynchronous abbrev. bisync; also BSC. A link- interface module located in a node cabinet/shelf. layer protocol for synchronized transmission, usually in EBCDIC, of binary coded data, primarily for IBM backplane utilization A measurement of the 3270-type equipment; controls the establishment of a amount of data being transmitted across the valid connection and the transfer of data; supports backplane, relative to the total bandwidth available. "intelligent" terminals and generally supports error backward explicit congestion noti®cation correction. (BECN) indicator A bit in a frame relay frame that bit 1. The smallest unit of information in a binary is set by the network to notify the user's equipment system, representing the choice between a mark that congestion avoidance procedures should be (pulse) designated as 1, or a space (no pulse) started to limit the amount of traf®c injected into the designated as 0, condition. 2. The speed at which bits network or sent to the node processor. The ®eld is set are transmitted, usually expressed in bits per second in a frame going in the opposite direction of the (bps). congestion. bit error rate (BER) The ratio of the number of bandwidth The amount of data that can be characters of a message incorrectly received to the transmitted over a channel, measured in bits per number of characters of the message received. second. BNS-1000 A fast packet switch offering connection- bandwidth balancing A procedure that allows oriented broadband technology for frame relay service effective sharing of bandwidth across several modules and LAN interconnect with network management. contending for bandwidth. BNS-2000 A cell relay switch that offers connection- bandwidth, expected For session maintenance, a oriented service (300 bps to 1.54 Mbps) and measure of the average traf®c expected on a facility, connectionless, high-speed service (1.5 to 44.74 over its combined, active channel sets, over time. Mbps) using broadband technology. Base Power Unit A base cabinet that provides AC BNS-microSwitch A switching product that power distribution and optional power factor provides low-speed SMDS access and local switching correction, battery backup, and a battery charger. when bandwidth needs are in the 64 to 768 Kbps battery backup A power option that provides power range. if power to a cabinet/shelf power fails. boot To start a computer system; see also automatic baud A measure of signaling speed; the number of reboot, cold boot, warm reboot. times per second that the state in a channel is switched B port See port B. (or reversed) during data transmission; each state change may represent two or three bits; hence, a baud bridge A device that enables similar or dissimilar rate of 300 may equal 900 bits per second. LANs to exchange data. B-Channel A circuit-switched bearer channel, a bridge module The Ethernet Bridge Interface component of ISDN, that carries voice or data at 64 Module (EBIM), which resides only in an ISN Kbps in either direction. concentrator.

Data Networking Products Terminology, Issue 4 27 ______Glossary

bridging See virtual multipoint bridging. bus The wiring through which data travels to the Control Computer. bridging concentrator A generic term for the ISN Concentrator. byte A measure of consecutive binary digits; a sequence of eight bits. broadband Describes a facility that allows trans- mission of more than one message at a time, each on a different frequency within the bandwidth, and that can handle more than one channel simultaneously; a C communications channel that has a bandwidth of 1.54 cabinet The basic unit of a node, housing shelves to 155 Mbps, which is greater than a voice-grade containing control, interface, and trunk modules; see channel; in contrast, narrowband can carry two-way also shelf. voice and data communications at a range of frequencies between 300 bps and 9600 bps, a cabinet alarm(s) See shelf alarm(s). relatively slow speed. Cabinet Interface Module (CIM) The module in a Broadband±Integrated Services Digital Series M2 Switch Shelf that converts an URP packet Network (B-ISDN) A high-speed network stream (from a Series M1 Control or Port Shelf) into architecture that allows the movement of information cell segments for data transport. at 156 or 622 Mbps, along with the transmission of Cable Repair Administrative System voice, full-motion video, and data signals. (CRAS) An Operations Support System (OSS) used broadcast The sending of information by a telephone company to analyze outside plant simultaneously to more than one receiving station; the troubles and performance characteristics. stations must be on the same circuit and be accessed call accounting A service for tracking the date and by a common calling procedure. For example, a host connection time of calls through the network on a port broadcasts all transmission over all virtual per-port basis to assess charges. circuits associated with the port; see also fanout, 2. call hold A node activity that establishes a virtual broadcast bus See receive bus. circuit across a network and allows a user to have broadcast storm In large, bridged networks, many more than one call, or connection, active at any time. network devices producing packets as fast as they can, call looping A routing error that occurs when a call pushing thousands of packets onto the network each setup (connection-oriented service) request is rerouted second. Causes include inaccurate device setup by endlessly without reaching its destination. miscon®guring the broadcast address, bugs in software design, or network implementation. calls barred An X.25 feature that allows the node administrator to restrict incoming and outgoing brouter A coined term for a bridging device that is switched virtual circuit calls at an X.25 endpoint. extended to copy some functions such as path splitting, which takes partial advantage of redundant call screening See CPM call screening; trunk call paths through the network between source and screening. destination. call screening security pattern A character string that de®nes permitted and prohibited destinations for buffer ¯ushing An optional feature that clears the calls entering a node from a trunk. memory buffers of synchronous ports in TSM-T1s, running on GOS5 lines and handling HDLC and call setup A node activity that establishes a virtual SDLC protocols; this avoids ending sessions over full circuit (for connection-oriented service) across the duplex endpoints when buffer overruns occur as a network. result of synchronous devices transmitting continuous collapsed backbone LAN interconnection using a streams of data. single high-speed switch instead of a network of BURST IEEE 802.1. A spanning tree algorithm for bridges and routers. routing and the recovery of connectionless network cell The type of packet format transmitted in ATM service (CLNS) traf®c. switching technology, consisting of 5 header octets

28 Data Networking Products Terminology, Issue 4 ______Glossary

and the information payload (48 octets) at the User channelized T1 (ChT1) An input/output (I/O) Network Interface (UNI); see asynchronous option for the Frame Relay Module (FRM) with an transfer mode (ATM), cell relay. integrated DSU that provides 24 x DS0 in N x 56/64 allotments and that supports ESF and D4 framing and cell relay One of two types of fast packet switching AMI and B8ZS line encoding. technology; cell relay and frame relay are both hybrid forms of traditional packet switching and channel service unit/data service unit circuit switching. (CSU/DSU) External multiplexing devices. central of®ce (CO) A telephone company location channel set (CS) A group of channels, or links on where call switching is done. the node backplane; each set is designated for incoming, outgoing, or two-way communication; on a central of®ce (CO) equipment Apparatus used in session maintenance trunk, a set of up to 126 a telephone company central of®ce (CO) for contiguous channels, including 125 user channels; a communications services. channel set can be con®gured as active or standby; see central of®ce (CO) frame The mounting rack in a also active channel set (CS), standby channel set telephone company central of®ce (CO) where node (CS). cabinets/shelves are installed; frame mounting meets CIM±CTRM link A ®ber connection between a Series central of®ce environmental requirements. M2 Switch Shelf and a Series M1 Control Shelf central of®ce local area network (CO-LAN) A and/or Port Shelf. data communications network, switched through a circuit board Also circuit pack. telephone company central of®ce (CO), that covers an area with a radius up to 3 km by combining voice and Circuit Maintenance System±1C (CMS-1C) An data on the same subscriber loop. Through CO-to-CO Operations Support System (OSS) system used by connections, a CO-LAN can be extended to unlimited telephone companies to support and administer 4ESS wide area networks (WANs). switch and Toll Terminal equipment associated with a central of®ce (CO). Central Of®ce Operations Systems (CO-OS) A network of support systems switched through a Clear To Send (CTS) A signal sent from the DCE to telephone company central of®ce (CO). the DTE indicating the line is clear to receive data; a response to RTS from the terminal. Central Of®ce voice/data multiplexer (C-VDM) An AT&T Voice Data Multiplexer that client Any executing program that makes a request of receives a signal through telephone lines at a central a server. of®ce (CO) and separates it into voice and data Clock/Trunk/Repeater Module (CTRM) A signals; it also combines these signals sent from a module that provides connection for a Series M1 central of®ce to communicate with a remote Control or Port Shelf to a Series M2 Switch Shelf; it voice/data multiplexer (R-VDM) on the customer also provides the clocking function for M1 shelves. premises. closed user group (CUG) A set of network devices central processing unit (CPU) A component of that can communicate only with other members the Control Computer that includes the circuits sharing the same administered pro®le, used in X.121 controlling the interpretation and execution of addressing; see also closed user group pro®le. instructions. This unit is labeled ECPU. closed user group (CUG) pro®le An administered certi®er See Hard Disk Certi®er. set of shared characteristics that de®nes security for a group of endpoints; see also pro®le. channel A transmission path or link; a logical closed user group (CUG) security A security transmission path in a trunk or other module. scheme in which access to or from de®ned groups of channelized E1 (ChE1) An input/output (I/O) endpoints is restricted. option for the Frame Relay Module (FRM) with an Code Division Multiple Access (CDMA) A integrated DSU that provides 31 x DS0 in N x 64 digital system that allows more simultaneous allotments and that supports CEPT and CRC4-CEPT telephone calls onto the same radio frequency than framing and HDB3 line coding. TDMA, an older digital technology.

Data Networking Products Terminology, Issue 4 29 ______Glossary

cold boot To start the Control Computer(s), in- CompuLert Computer Administration and cluding the Switch module(s) that control call Maintenance System. An Operations Support System processing. (OSS) used by telephone companies to log operations system activity and alarms and to isolate trouble. cold reboot To restart the Control Computer and the Switch module from an out-of-service state; to Computer Port Module±High Speed (CPM- reinitialize the operating system and StarKeeper II HS) A multiplexed optical ®ber interface module for NMS; see also warm reboot. connection to a host computer. cold standby trunk A spare trunk interface module, Computer System for Mainframe Operations or link, ready for service if the primary trunk fails; it (COSMOS) An Operations Support System (OSS) must be started manually. used by telephone companies to keep inventory control, to assign exchange facilities, and to control Comcode AT&T ordering code for cables and other mainframe administration for telephone subscribers. equipment. concentrator A communication device that command mode A level of interaction with the combines multiple channels over a single transmission network in which an end user can access help and path or link to the node; the aggregated rate option screens, and use call hold. (transmission speed) of the channels can be greater than the link rate; see also bridging concentrator, committed information rate (CIR) A frame relay Multipurpose Concentrator 15-slot (MPC15), protocol for the rate (expressed in bits per second) at Multipurpose Concentrator 7-slot (MPC7), which the network agrees to transfer information terminal adapter (TA). under normal conditions, established during administration of permanent virtual circuits (PVCs). concentrator links The following modules are used A network can be con®gured to provide a minimum to link concentrators to the node: SFT, SWT, TRK- CIR even under times of congestion. When using T1, TRK-HS, SAMML. CIR, a PVC may burst up to the full access rate. connectionless network service (CLNS) Also datagram. Interconnected communication that takes CommKit Host Interface Software Connects place without requiring separate, de®ned stages of computers running UNIX System V with the node, connection, as in BNS-2000; see also connection- and provides ®le transfer and remote execution oriented service (CONS), Switched Multimegabit service; multiplexed host software that enables the Data Service (SMDS). host connection to a Computer Port Module (CPM). connection-oriented service (CONS) CommKit FR An abbreviation for CommKit-attached Communication that proceeds through three de®ned hosts that interface with the Datakit II VCS Frame phases: (1) establishment of a connection, (2) transfer Relay Module (FRM) and the LAN Protocol Module of data, and (3) taking down the connection (for (LPM). example: frame relay, X.25, TCP, ordinary telephone calls). common equipment In Datakit II VCS and BNS- 1000, this equipment includes the Control Cabinet ConnectVU An Operations Support System (OSS) with its Control Computer modules. In BNS-2000, that provisions and maintains trunks for the 4ESS and this equipment includes the Series M2 Switch Shelf other network switches. and the Series M1 Control Shelf with its Control console Also administration console; system console. Computer modules. A video display terminal (VDT) used as an common modules In BNS-2000, these modules administrative interface to the node. include the CTRM, CIM, and dual Switch modules. console security A password optionally required for administrative access to a node. community (CM) A database entity that includes a collection of device controllers sharing an Consultative Committee for International interconnection to a higher level (closer to the Telegraph and Telephone (CCITT) A group backplane) unit. Examples of communities are all appointed by the United Nations to set international backplane shelves, concentrators, and session communication standards for user interfaces and maintenance trunks. network to network interfaces, now part of the ITU-T.

30 Data Networking Products Terminology, Issue 4 ______Glossary

contention A method of data transmission line CSCANS/SCANS Applications used by U.S. RBOCs control in which stations vie for control of a common to download software changes and updates via dial-up bus or communication line. modem to their AT&T network elements such as the 4ESS and 5ESS switches. contention bus See transmit bus. Customer Network Controller (CNC) A control byte An 8-bit value that operates in end-to- microprocessor-based Operations Support System end signaling over a virtual circuit or that acts as a (OSS) used by telephone companies to allow supervisory byte for end-to-common control use. customers to control the digital cross-connect capability of the Digital Access Cross-Connect Control Cabinet (Shelf) In Datakit II VCS/BNS- System (DACS) from a terminal at their own of®ces. 1000, a modular cabinet that contains the Control Computer. In BNS-2000, a Series M1 shelf that customer premises equipment (CPE) Equipment connects to Series M2 shelves. owned and managed by the customer of a telephone company. Control Computer (CC) The modules and units cyclic redundancy check (CRC) A method of (including the ECPU with memory, Eswitch, disk/tape error detection using cyclic redundancy code. A CRC controller(s), and SCSI unit) that control call value is generated at the transmitting terminal, based processing and switching activities in the node. on the contents of the message transmitted. An Control Computer Module (CCM) Introduced in identical CRC generation is performed at the BNS-2000, Release 4.0 and Datakit II VCS, Release receiving terminal and if it does not match, the 6.0, this single board module replaces the modules in message was received incorrectly; see also the Control Computer (CC) plus the MRCM; a longitudinal redundancy check (LRC) and vertical separate tape module can be located internally in a redundancy check (VRC). shelf or externally.

Control Computer administration mode See D operations mode. DACSlink transmission shelf A small equipment control modules See Control Computer Module shelf that translates IP commands on a StarLAN to (CCM); Control Computer (CC). X.25, linking a Datakit II VCS to a DACS IV-2000. controller See Control Computer Module (CCM); DACSmate software Remote maintenance terminal Control Computer (CC). software. controller mode switch The switch on the DACScan±2000 A system that provisions and faceplate of the Control Computer Module (CCM). manages networks controlled by AT&T Digital Cross-connect Access Systems (DACSs) from a CPM call screening A security feature that allows central location. the network administrator to set limits on the calls that database resizing A restructuring of the size of can be made from host computers connected to the system resource tables in the database. node via a Computer Port Module (CPM). Data Carrier Detect (DCD) Also Carrier Detect Craft Access System (CAS) An Operations (CD) or Received Line Signal Detector (RLSD). A System (OS) used by telephone companies to allow signal sent from the DCE to the DTE that the call has service technicians to access operations systems such been established through the data facility. as the Loop Maintenance Operations System/Work Manager (LMOS/WM). data circuit equipment (DCE) Also data communications equipment. The functional crankback An extended routing function that drops a equipment that establishes, maintains, and ends: a call-setup request (for connection-oriented service) connection, the signal conversion, and the coding back to the originating node to try an alternate route if required for communications with a data circuit. DCE it cannot complete the current route to its destination may or may not be a part of a computer (a modem, for because of a trunk failure; see route advance; see example, is DCE). For synchronous interfaces, DCE also hop count. refers to the device that provides clocking.

Data Networking Products Terminology, Issue 4 31 ______Glossary

datagram A packet switching service named after assigns order numbers, and maintains price ®les, information packet, called datagrams, that are self- among other activities. contained and carry a complete address and are data terminal equipment (DTE) 1. Equipment that transferred between end users. Datagrams are routed usually includes the control logic, buffer store, and independently and may arrive out of order; one or more input/output devices (terminals, printers, con®rmation of delivery is provided by higher level or computers). 2. For synchronous interfaces, protocols; see data unit. devices that receive clocking. DTE can also provide Datakit II Virtual Circuit Switch (VCS) A data error control, clock synchronization, and station switch with low delay that provides high-speed data identi®cation. communication between different networks and data transport facility The media (wire, carrier, various computer equipment. The switch can connect ®ber, or radio) through which data signals travel from LANs into wide area networks (WANs), and one device to another; see also facility. interworks with BNS-1000 and BNS-2000. data unit Packetized information called a datagram data link connection identi®er (DLCI) In frame that is transferred between end users. relay transmission, a number that identi®es a pre- established circuit (path through the network to a data window See window size. desired destination); the number also identi®es the end DDS Trunk See ACCUNET DATAPHONE Data device owning that particular frame of information. Service. Data Network Control Center (DNCC) A central debugger (DBG) mode A low-level processing location in a telephone company where personnel state built into the ®rmware on the Control perform network management and surveillance for Computer where software errors or bugs can be Operations Support Systems (OSS) covering one or isolated. more central of®ces (COs). default An operation, function, or value that is Data Network Identi®cation Code (DNIC) An supplied by the operating system, set by the system X.121 address level, a four-digit number from 0000 to administrator, or customized by the end user; factory 9999 that identi®es a network, equivalent to the default means an operation, function, or value set mnemonic network level address. A DNIC is used to during the manufacture of a discrete component. route calls to other public data networks. The ®rst 3 digits of a DNIC are the Data Country Code (DCC) default routing A feature of automatic alternate and the last digit is the Network Identi®er (NI). routing that centralizes address knowledge in a small set of hub nodes; a hierarchical scheme consisting of data network interface A device that translates one a hub node with attached subsidiary nodes that can network's protocol to the protocol used by another route calls with unknown address information to the device or network. hub node, which has knowledge of all addresses, for Data Processing Center (DPC) A site where rerouting. mainframe-based computer systems are operated and destination (code) The call address for an endpoint maintained. or terminal on the network made up of network, area, data service unit (DSU) A device that provides an exchange, and local service address, or DNIC, service interface between data terminal equipment (DTE) region, service area, and endpoint number, or any and a digital transmission service, such as DDS or T1. subset or combination of these addresses. data set A term synonymous with modem. device controller A physical entity within a community (CM) that controls physical or logical Data Set Ready (DSR) A signal that the DCE is devices, directly or indirectly, or trunks to another operational. node. Data Switching Information System (DSIS) A dialer An automatic dialing mechanism that accepts a software system that assists personnel involved in code which is part of a dial string, or destination node design in con®guring nodes. The system (code), and uses it to set up a call; also accepts a determines modules needed to support various telephone number on a switched or leased telephone communication services, monitors node resources, network as part of a destination request.

32 Data Networking Products Terminology, Issue 4 ______Glossary

dial string A service address; see destination international PDN address numbering plan; a (code). subsidiary standard for an international address format under X.25. Digital Access Cross-Connect System (DACS) A multipurpose operations system echoplex An asynchronous terminal-to-host controlled by a microprocessor and used by telephone communication mode in which the host echoes each companies to administer cross-connects and to test character entered at the terminal. access for digital signals. ECPU The central processing unit of the node; see Digital Data Service (DDS) II A digital Control Computer. transmission carrier service; see ACCUNET electromagnetic interference (EMI) Disruption of DATAPHONE Data Service. signal transmission caused by radiation of unwanted Digital Signal (DS) Also Digital Service; A series of electrical and magnetic frequencies that are "picked signals (service levels) de®ned by ANSI and accepted up" by electronic devices. by the ITU-T/CCITT: egress The direction of data traf®c transmitted from DS0 Digital Signal, Level 0, one of twenty-four 64 the switch via the SMDS Subscriber Network Kbps channels, a subrate of T1 service (FT1). Interface (SNI) to the subscriber device; see also ingress. DS1 Digital Signal, Level 1, 1.544 Mbps, equivalent to T1. egress SNI The Subscriber Network Interface (SNI) between the destination subscriber's equipment and DS3 Digital Signal, Level 3, is 44.736 Mbps, the SMDS Switching System (SS) that serves the equivalent to 28 T1 channels, or T3. subscriber. directory assistance An on-line list of calling egress SS The SMDS Switching System (SS) that addresses and network services. serves as the destination address (DA) for traf®c. disk/tape subsystem The SCSI disk and tape drive electrostatic discharge (ESD) Release of a built- system in the node Control Computer. up electrical charge from an electronic component Distributed Queue Dual Bus (DQDB) IEEE such as a printed circuit board. 802.6/D12. A cell relay standard for Metropolitan embodied SAC An embodied Service Access Code Area Networks (connectionless Media Access Control (SAC) in which a switching system (SS) must process [MAC]). the three digits of the address following the SAC to downloadable module A module that requires determine the network serving the address. In voice software to be downloaded from the node Control , an example of an embodied SAC is the 900 Computer or an external host. SAC. DS1 Internodal Trunk See Standard Wire Trunk encapsulation The process of encasing one protocol (SWT), Trunk-T1 (TRK-T1). in another protocol's format. DS3 Internodal Trunk See Trunk-T3 (TRK-T3), endpoint One end of a potential virtual circuit; any Trunk-T3A (TRK-T3A), Trunk-T3I (TRK-T3I), device connected to a terminus of the network such as and Trunk-T3S (TRK-T3S). a terminal, host port, or printer.

endpoint number (EPN) An X.121 numeric address level, equivalent of the mnemonic local service E address. E1 A digital transmission facility providing 2.048 end user A PC, terminal, or workstation user in the Mbps of bandwidth. network. E3 A digital transmission facility providing 34 Mbps enterprise network platform Hardware and of bandwidth. communications facilities to interconnect private E.164 ITU-T/CCITT Recommendation. Numbering LANs and WANs. Plan for the ISDN Era, Geneva, 1991. An

Data Networking Products Terminology, Issue 4 33 ______Glossary

envelope In layered communications protocols, the that are used to expand node and networking data presented by a higher level to a lower level is services. enclosed within control information and the whole is external transmission equipment extends the called an envelope; see also packet. range of EIA RS-232-C signals for synchronous EPN hash value A number derived from a and asynchronous communications. destination endpoint number (EPN) that is used in address balancing to route traf®c across equidistant Erasable Programmable Read-only Memory paths; EPN hash values fall into eight categories. (EPROM) Computer memory that can be totally erased and reused. EPN range 1. In E.164 addressing: a block of 1,000 endpoint numbers (EPNs); for example, EPN range 0 error threshold The number of errors (designated as is 0000±0999 in a Service Area (SA); a node can have a level) at which an alarm is generated or other action up to ten SAs and all ten blocks can be assigned to is generated. one SA. 2. In X.121, for Datakit II VCS, BNS-1000, Ethernet A baseband LAN speci®cation invented by or BNS-2000, an EPN can be a block of 1 to 10,000 Xerox Corp. and developed by Xerox, Intel, and DEC. EPNs assigned to an X.25 endpoint. Ethernet networks operate at 10 Mbps, using equipment categories The major categories of CSMA/CD running over thick or thin coaxial cable or Datakit II VCS, BNS-1000, and BNS-2000 equipment twisted pair cable; IEEE 802.3 de®nes this are the following: speci®cation. node equipment is the backbone of a network. It Ethernet Bridge Interface Module (EBIM) An oversees network communications, performs interface module that supports LAN bridging for administrative and diagnostic functions for modules Ethernet environments. and devices connected to the node, and provides EtherTalk The AppleTalk over services to users. Ethernet/IEEE 802.3. LAN interconnect equipment, including event-driven operating system (EDOS) An bridges, routers, and gateways; see LCS- terms. operating system that runs on any downloadable concentrators link a group of users to the node Synchronous Interface Module (SIM) and that over a ®ber or wire line. They provide an implements data communication protocols and alternative to direct connections that saves node provides interprocess communication through event capacity for other equipment, reduces cabling costs, and stream interfaces. and provides a variety of access speeds. exchange Part of a destination (code) used in an interface modules are circuit boards located in address. nodes and in concentrators that supply services to expanded Service Region (SR) When routing connected devices. These modules support messages from the source to their intended asynchronous and synchronous communications, destination, if a node makes decisions based on frame relay, Switched Multimegabit Data Service Service Region + Service Area (SR+SA), the SR (SMDS), networking, host interfaces, LAN added to an SA is called an expanded SR. connections, and X.25/X.75 services. Extended Binary-Coded Decimal Interchange input/output (I/0) distribution boards are used Code (EBCDIC) An eight-bit character code. See with interface modules to provide signal interfaces, table following this glossary. such as EIA RS-232, EIA RS-422/499, and ITU- T/CCITT V.35, etc. extended routing A feature enabling a call-setup integrated applications processor module, request, for connection-oriented service (CONS), on abbrev. DKAP, provides context switching, encountering a problem in its path, to drop back to its protocol conversion, security protection, X.25 originating node and then try a new path; see passthrough, SVC-to-PVC splicing, broadcast, crankback, hop count, route advance. software download, and other services. Extension Shelf, Series M2 A BNS-2000 cabinet peripheral equipment includes various designed to hold high-speed interface modules, for autodialers and voice/data multiplexers (VDMs) connection to the Series M2 Switch Shelf.

34 Data Networking Products Terminology, Issue 4 ______Glossary

Extension Cable/Clock I/O Board (ECCIOB) An fractional T1 (FT1) service Transmission that uses I/O distribution board placed in a Series M2 one, or several, of the twenty-four 64 Kbps channels Extension Shelf that connects via multicoax cable to in T1; used for trunks, links, and frame relay service. an Intershelf Cable/Clock I/O Board (ICCIOB) in a frame The data unit of transmission at the link layer Series M2 Switch Shelf. of the Open Systems Interconnection (OSI) Reference Model. F frame relay ITU-T/CCITT Recommendation (I.122). A statistically multiplexed interface standard for facility 1. A data link. 2. All the equipment and high-speed data transmission in which user data is transmission media between two nodes, or between a packaged into variable length frames, each containing node and a concentrator. 3. When con®guring an a frame header that identi®es the virtual circuit with Access Interface (AI)±T1 module, the timing for the which the frame is associated. Frame relay AI-T1 comes from the Stratum 4 Clock (SSM4) or a incorporates the function of error detection, but router; if a router supplies timing, the AI is said to get correction is performed by an intelligent endpoint its timing or clocking from the facility. such as a router. By streamlining network processing, frame relay makes data transmission faster and more fanout 1. A feature that provides multipoint bridge ef®cient. emulation of synchronous protocols within the TSM- T1. 2. The connection of different control units on a An application of frame relay is LAN interconnect, single multipoint host line to physically different lines the carrying of LAN traf®c from a router over a wide on any node in the network. Fanout dynamically area network (WAN). determines the channel to route data for each station Frame Relay Module (FRM) An interface module address by broadcasting the ®rst occurrence of an that provides 4 physical ports for frame relay service address to all channels associated with a port; see and that resides in a Series M1 shelf or a also broadcast. Multipurpose Concentrator (MPC). fast packet multiplexing A generic term for a frequency division multiplexing (FDM) remote networking technique that can provide: 1. 1. Dividing the available transmission frequency transport for a dynamically varying combination of range into narrower bands, each used for a separate asynchronous data, synchronous data, fax, video, channel. 2. One of four standard multiplexing voice, and LAN traf®c; 2. high (90% or better) technologies. See also FPM, SPM, TDM. network ef®ciency; 3. low network delay; and 4. predictable delivery of time-sensitive information. from bus See receive bus. ®ber host interface module See Computer Port full-duplex transmission Simultaneous two-way Module±High Speed (CPM-HS). communication. Fiber Interface Module (FIM) A trunk module in an fully connected A network con®guration in which ISN node; the counterpart of the Standard Fiber every node has a direct trunk connection to every Trunk (SFT). other node. ®rst in, ®rst out (FIFO) A queue structure, for fuse and alarm panel The panel in the top of a CO memory or a buffer, in which data that enters the frame that provides circuit protection for cabinet queue ®rst is the ®rst to exit from the queue. shelves and audible alarm signals. ®rst listed A search algorithm specifying access to group elements in their listed order; see also round robin. G ¯ow control The process of controlling data G.700±G.795 ITU-T/CCITT Recommendations. communication by allowing the receiver to regulate General Aspects of Digital Transmission Systems; transmission from the sender to avoid buffer over¯ow; Terminal Equipments. see buffer ¯ushing.

Data Networking Products Terminology, Issue 4 35 ______Glossary

G.703 ITU-T/CCITT Recommendation. LATA. Although there may be multiple LECs in a Physical/electrical characteristics of hierarchical LATA, only one LEC is the agent for the group digital interfaces. address. G.704 ITU-T/CCITT Recommendation. Synchronous Group Address Resolver (GAR) A module frame structures used at primary and secondary located in a BNS-2000 Series M2 shelf that provides hierarchical levels. the capabilities of a Group Address Agent (GAA). The GAR is used only in an SMDS network that G.707 ITU-T/CCITT Recommendation. Synchronous serves as a GAA for group addresses. digital hierarchy bit rates. group name An identifying label for a database G.708 ITU-T/CCITT Recommendation. Network element consisting of a set of ports. node interface for the synchronous digital hierarchy. G.709 ITU-T/CCITT Recommendation. Synchronous multiplexing structure. H gateway A server module or unit that transforms the Hard Disk Certi®er A program that checks the address and protocol conventions of one network into existing format of a hard disk for the node operating the conventions of another. system and that can repartition the disk for faster Global Software De®ned Network (GSDN) An access to data. AT&T service that interconnects with a variety of hello message A PAD identi®cation service signal switching systems used by international such as X.28 signaling; see message of the day. telecommunications companies to provide fast call setup times (for connection-oriented service) and help An interface between the operating system and high-quality transmission. the end user that provides on-screen instruction. grade of service (GOS) Various levels of support high availability The level of service readiness of a for certain protocol features such as ¯ow control, node equipped with redundant Control Computers, error detection, and error correction: GOS1Ðno ¯ow dual Switch modules, redundant power supplies, and control, no error control; GOS2Яow control, no remote maintenance capabilities. error control; GOS3Ðno ¯ow control, no retransmission, error detection; GOS4Яow control, High Level Data Link Control (HDLC) A data error detection, no retransmission of blocks with link, bit-oriented synchronous data communications errors or missing blocks; GOS5Яow control, error protocol, included in the X.25 packet-switching detection, retransmission. protocol. Graphics System See StarKeeper II NMS hop The logical distance between two adjacent nodes; Graphics System. each node in a call's path counts as one hop. Graphics Workstation See StarKeeper II NMS hop count The maximum number of nodes traveled Graphics System. by a call-setup request for connection-oriented service (CONS). A hop count prevents the looping that group A database component identifying a set of results from routing errors; see also hop. ports that are considered a unit. There are two kinds of groups: local (can include any module except a host A computer that provides services for another trunk) and trunk (includes only trunk modules). network entity. group address A collection of E.164 addresses to host autobaud A feature that sets a remote network which Protocol Data Units (PDUs) can be sent port to match the speed of the host port, allowing use simultaneously. of autobaud detection on the destination host. Group Address Agent (GAA) network A host interface An interface (module) between the network that serves a particular Group Address. The node and a host computer. agent for this group address, or community of interest, host port The port on a node or concentrator to is a carrier. For a LEC, the agent network chosen is a which a host computer is connected.

36 Data Networking Products Terminology, Issue 4 ______Glossary

hub node In default routing, a high-level node that ingress Switching System (SS) The SMDS can resolve network routing in a network hierarchy. Switching System (SS) that serves the source address (SA) for traf®c. hunt group A set of endpoints on carrier facilities that can be addressed as a unit for routing purposes; input/output (I/O) distribution board A small the association of a list of receiving devices with a circuit board that plugs into the backplane from the single local service address. side opposite an interface module and that physically connects via cables from an external device to a node or Multipurpose Concentrator (MPC). I Inter-Carrier Interface (ICI) The interface that provides SMDS among carrier networks. I.121 ITU-T/CCITT Recommendation. The standard for asynchronous transfer mode (ATM) transmission. interface A shared, or common, boundary between associated devices, systems, or modules, usually in I.122 ITU-T/CCITT Recommendation. The standard the same node. for frame relay transmission; framework for providing additional packet mode bearer services. interface module A printed circuit board providing network access for a speci®c type of end device. I.364 ITU-T/CCITT Recommendation. The standard for Connectionless Service. intermediate node In session maintenance, a node that relays calls between originations and destinations, I.555 ITU-T/CCITT Recommendation. The standard some of which are on other nodes. Unlike a tandem for Frame Relay Interworking. node, an intermediate node has local endpoints that ICI modules Inter-Carrier Interface (ICI) modules can originate and receive calls. include the Access Interface (AI) modules, Group internal endpoint (iep) A logical terminus of a Address Resolver (GAR) module, and TRK-T3I virtual circuit for internal communication between a module. node and StarKeeper II NMS. IEEE 802.1 A standard for the spanning tree international CUG number (ICN) The algorithm; see BURST. international interlock code (IIC) for network routing. IEEE 802.3 A standard for Ethernet. International Telecommunications Union± IEEE 802.5 A standard for token ring networking. Telecommunications (ITU-T) International standards-setting organization that supersedes CCITT. IEEE 802.6 A standard for Distributed Queue Dual Bus Metropolitan Area Network (MAN) technology Internet A collection of packet-switched networks with two protocol layers, the Media Access Control that are connected via gateways. (MAC) layer and the physical layer (subdivided into internetwork SMDS Switched Multimegabit Data PLCP and TSD). Service (SMDS) that originates within one SMDS IEEE 802.6i A standard for intercompany client company's network and that terminates in a communications remote bridging. different SMDS network (usually involving an Interexchange Carrier). IEEE 802.9 A standard for integrated voice and data (IVD) transmission. interworking The capacity to establish trunk connections between different network switching individual address An E.164 address that identi®es products over which compatible end devices can a single Subscriber Network Interface (SNI). interact and share a common set of network services ingress The direction of data traf®c transmitted from and features. the subscriber device to the switch via the SMDS I/O board See input/output (I/O) distribution Subscriber Network Interface (SNI); see also egress. board. ingress SNI The SMDS Subscriber Network ISN Concentrator A bridging concentrator Interface (SNI) between the originating subscriber's connected to a node via optical ®ber (local) or wire equipment and the Switching System (SS) that serves trunk (remote) with interface slots for the Ethernet the subscriber. Bridge Interface Module (EBIM).

Data Networking Products Terminology, Issue 4 37 ______Glossary

isochronous Uniform in time; a characteristic of an LCS60 Network Interface for Ethernet A VME- event or signal that recurs at regular intervals, based hardware platform (terminal/gateway/server) required to support voice or video transmissions. with an Ethernet interface board and CommKit Host Interface Software that provides high-speed telnet gateway connections between TCP/IP LANs to K AT&T data switches or a Multipurpose Concentrator 15-slot (MPC15). For remote networking, the LCS60 keep-alive test Messages sent by a node to detect a supports Serial Line IP (SLIP) and Point-to-Point trunk or link failure. The test keeps track of the (PPP) protocols. number of messages lost in a sliding window of time, LCS200 Network Routers A family of routers called the threshold. If too many messages are lost connecting LANs to WANs; WAN connections within a threshold, a trunk failure is declared. include X.25, SMDS, ATM, and frame relay; LAN Kermit protocol. A ®le transfer standard with a wild connections include FDDI, Ethernet, and Token Ring. card feature that allows multiple ®le transfers with leaf node In default routing, a node connected to a one command; in the public domain, but supported by hub node. Columbia University. leaky bucket The policing algorithm used with frame relay and ATM to arbitrate usage of network L resources.

LAN bridging A service that extends a local area legacy network The existing network and equipment network (LAN) environment by joining that must interwork with or be replaced by new geographically separated LANs in a single logical technology. network. Level 2 Protocol Data Unit (L2-PDU) Also LAN Communications System (LCS) AT&T's segment. A unit of information processed by the name for a family of products for LAN inter- second level of the SIP; also a unit of service counted connections; see also LCS- terms. for data generation. LAN interconnect Local area network (LAN) Level 3 Protocol Data Unit (L3-PDU) Also packet; interconnection via a device or module that allows SMDS data unit. A unit of information processed by connection of a LAN running under a particular the third layer of the SIP; also a unit of service protocol to the transport backplane of the node. LAN counted for data generation. interconnect is characterized by high-speed, bursty data transmission. light-emitting diode (LED) A small solid-state light that shows hardware or ®rmware status. LAN interconnect interfaces Interface modules such as the AI-T1, AI-T3, AI-T3P, FRM (ChE1, line A connection at the physical layer of the network ChT1, V.35), and LPM for LAN interconnections. between two points, characterized by a rate and a LAN Interconnect Services Services available means of modulating a signal onto the physical with the LCS60 Network Interface and LCS200 transmission equipment. Network Routers; see also frame relay. link A data transport facility connecting a node to a LAN Protocol Module (LPM) A module that concentrator; see also CIM±CTRM link. combines the elements of a Frame Relay Module Link Access Procedure Balanced (LAPB) (FRM) and an IP router with static routing support. protocol. A data link-layer standard under X.25 The module has two physical twisted pair Ethernet responsible for providing an error-free line for the ports and 27 frame relay logical ports. The LPM is higher layers. designed for use with central of®ce (CO) networks that use TCP/IP networking. Link Access Procedure D-channel (LAPD) protocol. A data link-layer standard under X.25 for LAN-WAN convergence Use of the same protocols ISDN connections. The D-channel is a 16 Kbps in local and wide area networks to simplify operations signaling channel within ISDN primary-rate access. and interworking.

38 Data Networking Products Terminology, Issue 4 ______Glossary

link interface A trunk-like connection between the loop around See loopback. node backplane and a concentrator device housing multiple modules. loopback A test pattern sent and returned from the Control Computer to a module or port, to diagnose Link Interface Module (LIM) A module that problems. connects an ISN concentrator to the node. loopback connector A connector for loopback loader mode A transition state in the system diagnostics. software preceding monitor mode. Local Area Data Channel (LADC) FCC standard. LADC I and LADC II are standards for signals sent M over LADC wiring. LADC I applies to signals sent over systems that include cables outside a building. Macstar Software System An Operations System LADC II applies to signals sent over systems using (OS) that allows Centrex customers to prepare and use cables entirely within a building, which permit telephone line feature changes and con®gurations. transmission of signals with higher frequencies (because bandwidth is greater) than LADC I. magic A property that allows a module to control access to the node backplane. local area network (LAN) A data network with communicating devices and connection media running main distribution frame (MDF) A distribution at a rate of 1 megabit or greater that occupies a single frame on which outside plant cables terminate on geographic location, usually with a radius of 3 vertical protector strips, and from which they cross kilometers or less. connect to central of®ce (CO) line equipment on horizontal blocks. local service address Part of the addressing scheme that refers to an endpoint or a host on a Maintenance and Redundancy Control Module network that receives calls; part of a service address; (MRCM) A multiport administrative interface see also area, destination (code), exchange, module that adds maintenance and automatic recovery network, service address. capabilities to a node. logical channels In session maintenance, Management Information Base (MIB) transmission paths on a physical trunk module that are A collection of information on an SNMP agent, logically grouped to form a channel set (CS). including con®guration and status values, that can be logical device (LD) A collection of transport accessed via SNMP. MIBs are organized into endpoints addressed as a unit for routing; an external modules: the foundation module is a MIB-II entity or a set of internal functions within a device conforming to Internet standards; extension modules controller. A port is always associated with one or de®ned by hardware vendors are called enterprise- more logical devices. Logical devices include speci®c MIBs. terminals, hosts, and maintenance and signaling channels for a device controller. M-bit A more-data bit, used in an X.25 data packet, for block mode devices. logical drive See partition. M-bus A communication path between the processor logical network Groups of devices linked by and SCSI unit. address through an intermediary device rather than through a direct physical connection. Mechanized Loop Test (MLT) System An longitudinal redundancy check (LRC) Also Operations System (OS) used by telephone companies longitudinal parity check. A technique for checking to test and qualify local transmission loops. errors in which an LRC character (called a block check character [bcc]) is accumulated at both the message The data sent from a transmitter to a sending and receiving stations during the transmission receiver over a common medium. of a block; the transmitted bcc is compared with the receiving end bcc for an equal condition, which message of the day Optional text lines that can be indicates a good transmission of the previous block; sent to terminal users when they connect to the see also CRC and VRC. network.

Data Networking Products Terminology, Issue 4 39 ______Glossary

message packet For connection-oriented network Multifunction Operations System (MFOS) A service (CONS), coded information of 180 bits or 18 system that collects and reports on traf®c envelopes (10-bit envelopes with one 8-bit data byte); measurements from network elements. for connectionless network service (CLNS) traf®c, multimedia A description usually applied to a device ®ve to 14 words with 32 bits per word. that can use more than one medium to display or metacharacter Special keyboard characters used for transmit information across a network, such as searches (pattern matching) and character substitution. different types of data (text and graphics) or a combination of voice, data, video components. mezzanine board A small circuit board with multiplexed host interface An interface module application-speci®c hardware that plugs onto a main providing a single high-bandwidth link to the network board. The main board with a mezzanine board uses for an asynchronous host computer; see Computer only a single slot in a BNS-2000 node; for example, Port Module±High Speed (CPM-HS). the FRM-M2 mezzanine board. multiplexer A device that transmits data from Minicomputer Maintenance Operations Center multiple circuits over a single physical circuit. (MMOC) A telephone company work center that contains minicomputer-based maintenance programs multipoint bridging, virtual See virtual for Operations Support Systems (OSS); equivalent to multipoint bridging. a data center for OS hosts. multipoint line A single communications channel (typically, a leased telephone circuit) to which more mini-node A two or three-shelf Datakit II VCS in a than one station or other device is attached. On Central Of®ce (CO) with less than ®ve attached selection, one or more devices on such a line may concentrators, provisioned with multiple trunks, each send or receive transmissions to or from the control connected to a different node in a utility network. station. mini-shell (MINI-SH) A UNIX-like interactive multipoint link See multipoint line. command interpreter used to gain access to utility programs for upgrading a database and other tasks. Multipurpose Concentrator 7-slot (MPC7) A concentrator, similar in function but smaller than the mode The different levels at which an administrator Multipurpose Concentrator 15-slot (MPC15), that can enter commands to the system. connects to the node via optical ®ber or wire trunk, modem (modulator-demodulator) Also data set. and has interface slots for CPM-HS, FRM, LPM, A device that converts digital signals from a form that MSM, TY12, X.25, X.25P, and X.75 modules. is compatible with data processing equipment to a Multipurpose Concentrator 15-slot (MPC15) A form that is compatible with analog transmission concentrator consisting of a cabinet that connects to equipment. the node via optical ®ber or wire trunk, and that has modem pool The association of modems by group interface slots for CPM-HS, FRM, LPM, MSM, or service address. TY12, X.25, X.25P, and X.75 interface modules. module A hardware unit of one or two boards (circuit multistation access unit (MAU) A device that packs) that plugs into the node backplane, has a bus provides access to a Token Ring/IEEE 802.5 LAN by interface, and a slot address in a cabinet or a shelf. up to eight individual workstations. In a star con®guration, MAUs are connected to each other in a monitor mode A low-level processing state built dual ring con®guration. into the ®rmware on the Control Computer that allows administrators to boot the system, copy and Multispeed Module (MSM) An interface module format a disk, display diagnostics, and test the Control that supplies high-speed asynchronous services such Computer hardware. as dial-in remote access to a local area network (LAN); for example, the MSM connects work-at- multicast A form of broadcast in which one original home users who need higher access speeds to support copy of a message is replicated and delivered to PC graphics. This module supports asynchronous multiple destinations. protocols at speeds from 75 bps up to 115 Kbps.

40 Data Networking Products Terminology, Issue 4 ______Glossary

N Network Management System (NMS) See StarKeeper II Network Management System NetMinder NetMinder Operations Systems manage, (NMS). monitor and troubleshoot the performance and status of voice and data network traf®c for medium to large Network Monitor See StarKeeper II NMS Network PTTs, RBOCs, independent and international Monitor. networks. N-hop neighbors In session maintenance, adjacent nodes whose shortest connecting path contains a NetPartner A management system for public speci®ed number (N) of physical trunks; a 2-hop networks that allows a telephone company's neighbor to a given node, is one in which the shortest customers to monitor surveillance messages and enter path to that node crosses two trunks. trouble reports to ensure that their network is operating at peak performance. node One or more cabinets or shelves that switch data traf®c under the supervision of a Control Computer. NETSTAR A management system that allows users to create services for international intelligent networks, Node Reroute Table (NRT) A table in the database including the creation, customizing, validation, and of a node supporting session maintenance that is used administration of a subscriber's call routing plans. to determine where to send reroute requests. The node uses the table to decide the reroute trunks and network ISO TC97. An interconnected group of assisting nodes that can aid in backing up a failed nodes; a series of points, nodes, or stations connected session maintenance trunk. by communications channels; the assembly of non®ber A term describing wire, satellite, and equipment through which connections are made microwave media. between data stations. Also, part of the destination (code) used in an address; similar to an international Non-Return to Zero/Non-Return to Zero telephone code. Each network can include multiple Inverted (NRZ/NRZI) Methods of encoding signals areas, each area can include multiple exchanges, and for transmission in data communications. each exchange can include multiple local service North American Numbering Plan (NANP) ITU- addresses. The ®rst level in the structure (network, T/CCITT X.121 Recommendation. The standard that area, exchange, local) of a service address, equivalent de®nes the structure of the Network Terminal Number to an X.121 Data Network Identi®cation Code (NTN) into the DNIC plus three ®xed length subparts: (DNIC). 4-digit DNIC, 3-digit Service Region (SR), 3-digit Network Access Control System A security Service Area (SA), and 4-digit endpoint number server software package that controls access to (EPN). resources and devices in a network. null packet An empty packet transmitted across the backplane bus when none of the modules has any data network access password An identifying code packets to transmit. assigned to a group of originating groups to prevent unauthorized access to a network; see also password. network address abbrev. netaddr. Representation O of a speci®ed network element in StarKeeper II NMS; the element's network address is a unique octet Eight (8) bits. identi®er. one-way logical channel An X.25 service that network attention signal A de®ned character(s) allows channels in a two-way group to be dedicated used to set up a call, to enter command mode, and to to incoming or outgoing switched virtual circuit disconnect a call from a network. (SVC)s. Network Builder See StarKeeper II NMS Network Open Systems Interconnection (OSI) Builder. model International Standards Organization (ISO). A seven-layer mode of the logical functions network element (NE) A piece of equipment or a performed in communications between user service that is part of a communications network. applications.

Data Networking Products Terminology, Issue 4 41 ______Glossary

operating telephone company (OTC) A PAD ID See x28sig. telephone company providing local or long-distance PAD service An X.5 service that allows exchange carrier service. Refers to all AT&T as well asynchronous to X.25-type connections; see packet as non-AT&T entities. assembler/disassembler (PAD). operations mode The typical state of the Control parity A common technique for detecting bit errors. Computer for monitoring and managing the network. See also loader mode; monitor mode; utility mode. partition A section of a hard disk that functions as a logical drive. Operations Systems Network (OSN) A data network used by telephone companies to run pass-through A system capability that allows access Operations Support Systems (OSS). to node operations, administration, and maintenance (OA&M) commands through StarKeeper II NMS. Optical Carrier (OC) SONET. A series of transmission speed transport levels from OC-1 up to pass-through service Synchronous X.25 to X.25- OC-96. type connections. optical ®ber range extender A device, used in password An identi®er required for administrative pairs, that increases the optical A ®ber signaling access to the node; see also network access distance. password, select group password. originating group The type of group assigned to path format A framed structure of digital devices, such as data terminals, that can call other information carried across a physical layer connection devices. between two points at a particular rate and enabling error detection; examples are D4, Super Frame originating group security pattern A pattern of Format (SF), ESF, and SONET. numeric, alphabetic, and special characters specifying the originating groups that are allowed or forbidden to Performance Reporter See StarKeeper II NMS access a given trunk group, receiving group, or two- Performance Reporter. way group. permanently active port A feature that allows a TSM-T1 synchronous port to be considered active as soon as it is put into service. P permanent virtual circuit (PVC) A full duplex packet Also Level 3 Protocol Data Unit (L3-PDU). A end-to-end connection between two communicating group of bits that is transmitted as a unit through a devices that depends on logical associations rather network, usually including data and control than a dedicated physical pathway; it is provisioned information such as addressing, identi®cation, and by a network administrator to connect one compatible error control ®elds. See also Level 3 Protocol Data endpoint to another. Unit (L3-PDU); cell. physical address See address. packet assembler/disassembler (PAD) ping abbrev. Packet Internet Groper. A utility An interface between a device and an X.25 packet- program, originally used in the Internet, to test switched network; the PAD converts the protocol used whether a destination can be reached by sending it an by the device and the X.25 protocol used by the ICMP echo request and waiting for a reply. The term network, allowing terminals to exchange data with is now in general use as a noun and also as a verb, for other packet mode terminals and hosts. example: "please ping host A to see if it is alive." Packet Stream Protocol (PSP) A connection- pipe A connection that routes a data stream from one oriented service convergence standard to translate destination to another (for example, from one router to URP in IEEE 802.6 another); multiplexed connections can be sent over paddleboard Technical slang for an input/output one such connection. (I/O) distribution board. A small component board pipelining The transmission of synchronous data as it used to install circuit elements (for example, bus arrives at the network interface, without waiting until terminators and shelf option cards) on the node a frame is ®lled; internal pipelining refers to the backplane. network.

42 Data Networking Products Terminology, Issue 4 ______Glossary

polling See status polling. pro®le An administered set of characteristics associated with speci®ed endpoints; see also closed port 1. A physical access point on an interface user group (CUG) pro®le, trunk call screening module. 2. In session maintenance, a physically pro®le, X.3 pro®le. independent I/O interface unit of a device controller; the port represents both the interface and the physical protocol(s) A set of rules, procedures, or line it supports. A session maintenance trunk has two recommendations governing control transmission and ports per device controller. reception between data communications devices. There are three main protocol categories, based on port A A Control Computer or MRCM port typically message framing techniques: character oriented; byte connected to a local administration console. count oriented; and bit oriented. port B A Control Computer or MRCM port typically Protocol Data Unit (PDU) The data entity connected to a system printer or to StarKeeper II transferred between two instances of a single layer of NMS. a protocol at two separate locations. public data network (PDN) A generic term for a Port Cabinet (Shelf) In Datakit II VCS and BNS- packet switching data communications network that is 1000, an 8 Mbps cabinet that contains interface available for public use. modules. In BNS-2000, a Series M1 shelf that connects to the Series M2 Switch Shelf. port M An administrative port on the Maintenance Q and Redundancy Control Module (MRCM) that can override ports A and B. Q.920 ITU-T/CCITT Recommendation. See Link Access Procedure D-Channel (LAPD). power factor correction (PFC) A recti®er with a power phase adjustment circuit that aligns the phase Q.921 ITU-T/CCITT Recommendation. ISDN User- between the alternating current and voltage to Network InterfaceÐData Link Layer Speci®cation. A maximize power transfer and minimize source power standard that speci®es the frame structure, elements of requirements; Power Unit, 562A. procedure, format of ®elds, and procedures for the operation of the Link Access Procedure on the D- power supply A unit that converts source power to channel (LAPD). nominal 5 VDC and 12 VDC for control and data circuits in a node shelf. Q.931 ITU-T/CCITT Recommendation. ISDN User- Network Interface Speci®cation. A standard that prede®ned destination (PDD) An association of a speci®es a network layer protocol, and procedures for ®xed network destination with an originating end establishing, maintaining, and clearing connections at device, administered by the network manager, that the interface. results in an automatic call setup request (for connection-oriented service) as soon as the originator quasi-random signal (QRS) T1.403, Frame Relay comes on line. standards. A signal consisting of a bit sequence that approximates a random signal. PREDICTOR An Operations Support System (OSS) used by telephone companies to locate potential cable query A request from the system for information, failures before they affect service. which is displayed on a terminal screen and requires a response from the end user at the keyboard. primary node The reroute node that is in charge of detecting a failed session maintenance trunk and queue A line or list formed by items waiting for initiating a reroute. service in a computer system. Primary Reference Source (PRS) A Stratum 1 timing source, or reference clock, that is a 1.544 MHz R B8ZS coded signal carried on a T1 circuit; a Secondary Reference Source (SRS) has identical random access memory (RAM) Read and write characteristics. capabilities without permanent storage of information.

Data Networking Products Terminology, Issue 4 43 ______Glossary

read-only memory (ROM) A special factory- single active channel set (CS) from a failed trunk. programmed memory that can be read but not written reroute request In session maintenance, a message after installation. When a device is turned on, it uses sent by the primary node on detection of a trunk the information stored in the ROM. failure; requests pass from Control Computer to real time network routing (RTNR) Priority routing Control Computer to create reroute paths that support during a network interruption. the active channel set (CS) from the failed trunk. receive bus Also broadcast bus, from bus, or FBUS. reroute tracking table (RTT) The table that shows The portion of the node backplane that carries the reroute status of each session maintenance trunk packets outbound from the switch. and channel set (CS). receive(d) data (RD) Data received by the DTE ring network A network con®guration in which from the DCE. every node is connected to exactly two other nodes. Receive Clock (RC) Also RCLK. A timing signal round robin A local service address search from a modem to a terminal receiver interface that sequence specifying access to group elements provides signal element timing. beginning with the element listed next after the last to receive a call. See also ®rst listed. receiving group The type of group assigned to devices, such as host computers, that can receive calls route advance In call routing, an algorithm for from other devices connected to the node. ®nding an alternative path when a call-setup request (for connection-oriented service) enters a node via the recti®er The power circuit that converts the trunk group that the node would use as the primary alternating supply current and voltage to direct current path to the call's destination; see crankback; see also and voltage; an entire application package inside the hop count. Base Power Unit for a node. Routing Algorithm Process (RAP) An AT&T reference clock A highly stable and accurate clock proprietary process that runs in the BNS-2000 Control (timing signal), which may be autonomous, with a Computer to implement BURST. frequency that serves as a basis of comparison for the frequency of other clocks; see Primary Reference routing, alternate See alternate routing; default Source (PRS). routing. remote console An administration console Routing Information Protocol (RIP) A connected through an asynchronous module. subprotocol of the TCP/IP suite; used for building, remote voice/data multiplexer (R-VDM) A maintaining, and using internetwork routing tables. multiplexer located at customer premises that is used RS-232-C An EIA interface standard for data to send and receive voice and data. communications, describing the electrical, Request To Send (RTS) A signal from the DTE to mechanical, and functional characteristics of the the DCE that data is ready to be transmitted. connections between devices exchanging data in serial binary form; the interface between DCE and DTE. rerouted trunk In session maintenance, a trunk that Speci®es an unbalanced interface through a 25-pin has been rerouted because of trunk failure D-shell connector or an 8-pin modular connector. (failed±rerouted) or the "route trunk alternate" command (healthy±rerouted). RS-422/RS-449 An EIA interface standard describing the electrical (RS-422), mechanical, and reroute node A node at the end of a session functional (RS-449) characteristics of the connections maintenance trunk: one node is the primary node; the between devices exchanging data in serial binary other node is the secondary node. form. Speci®es a balanced interface, with voltages reroute path In session maintenance, the series of measured as the difference between two signaling standby channel sets (CSs) that carry the traf®c of a leads, and 37-pin and 9-pin connectors.

44 Data Networking Products Terminology, Issue 4 ______Glossary

S server Any program offering a service that can be reached over the network; applies also to specialized save area A partition or section of a disk. machines, such as a ®le server. scalability A characteristic of computer products and service address An administered identi®cation code networking technology that allows incremental for a destination in the network. An address code can growth from small to large, slow to fast, or local to be represented as mnemonic, as X.121 numeric, or as wide area. both. There are four levels of a service address: Schedule Control and Maintenance Information network (or an X.121 Data Network Identi®cation System (SCAMIS) A set of systems used by Code), area (or an X.121 service region), exchange telephone companies for the special services (or an X.121 service area), local (or an X.121 environment. endpoint number); see also destination (code). SCSI board Small Computer System Interface service area (SA) An X.121 numeric address level, (SCSI) module. equivalent to the mnemonic exchange level; see destination (code). search sequence See ®rst listed; hunt group; round robin. service location The site where the SMDS Subscriber Network Interface (SNI) enters the BNS- secondary node In session maintenance, the node at 2000 network. the far end of a trunk from a primary node that responds to a reroute request from the primary node; session maintenance (SM) A feature that enables the secondary node determines the channel sets (CSs) all calls on a failed facility to be automatically that need to have sessions moved and the reroute rerouted before the applications using the facility paths to be used. sense the failed state and drop their calls; see also alternate routing. Secondary Reference Source (SRS) See Primary Reference Source (PRS). session maintenance (SM) trunk A physical trunk, partitioned into channel sets (CSs), and security server A standalone host computer that identi®ed as participating in session maintenance. checks a call setup request to determine whether the call should be connected to its destination. shelf A carrier inside a cabinet containing a backplane and other hardware that supports the security set See trunk call screening. insertion of modules into the backplane; see Series segment A Level 2 Protocol Data Unit (L2-PDU); M1, Series M2. the data unit of 53 octets in the Distributed Queue Dual Bus (DQDB) protocol transferred between peer shelf alarm(s) Warning signals of power, layer entities as the information payload. temperature, or voltage problems in a speci®c shelf on the backplane that appear on the system console select group A feature that allows users to choose screen or that are sent to a dedicated printer. the originating group whose access permissions they wish to assume. shell (sh) A computer interface that allows the running of program tools, or batch programming select group password The restricted code that scripts for node or network administration, allows use of the select group feature for requesting maintenance, and other tasks; the system supports connection to the network. running the shell alone (see mini-shell [MINI-SH], Series M1 Cabinets housing 8 Mbps shelves: the standalone utility shell), or concurrently with the Series M1 Control Cabinet (Shelf) houses control system processes; see also utility shell (utilsh). modules and user interface modules; the Series M1 Port Cabinet (Shelf) houses interface modules. signal ground (SG) A signal that establishes a common ground reference for all other signals on the Series M2 Cabinets housing 200 Mbps shelves: the interface except the protective ground. Series M2 Switch Cabinet (Shelf) houses Switch modules and interface modules; the Series M2 Signaling System 7 (SS7) The international ISDN Extension Cabinet (Shelf) houses additional high- standard for controlling network operations. speed interface modules.

Data Networking Products Terminology, Issue 4 45 ______Glossary

Simple Network Management Protocol SNMP Proxy Agent A software system that enables (SNMP) Internet. A protocol that communicates one machine, the proxy, to translate Simple Network network management information between a manager Management Protocol (SNMP) requests from the and an agent. SNMP allows a manager to retrieve SNMP Manager into transactions needed by machines management information from an agent on request that do not support SNMP agent software. and an agent to send information to the manager software disk striping A feature of StarKeeper II without an explicit request (this operation is called a NMS that allows partitioning of the hard drive. trap); see also SNMP agent, SNMP Manager, SNMP Proxy Agent. software download A feature in which updated software is directly downloaded from StarKeeper II SIP, Level 1 SMDS access protocol. A level of the NMS to a node. SMDS Interface Protocol (SIP) that describes physical and electrical connections to SMDS service, the software feature card A card that identi®es a lowest level of the protocol. Level 1 services are software feature package by name and by unique usually handled by CSUs/DSUs. numerical code. SIP, Levels 2 and 3 SMDS access protocol. Levels software registration key A code, provided by the of the SMDS Interface Protocol (SIP) that describe AT&T Customer Assistance Center (CAC), that addressing, framing, and other protocol processing for enables installation of the system software. SMDS service; Level 2 includes the part of the access source address (SA) An SMDS address assigned to protocol that speci®es the L2-PDU and Level 3 the SMDS subscriber who originates the SMDS data includes the L3-PDU. transfer. slot A physical space for placing a module in a spanning tree algorithm See BURST. cabinet/shelf. In BNS-2000 the physical slots are labeled 0±15 in Series M1 shelves and A/B0±13 in the speedcall A shortened name, or short code, for a Series M2 shelves. network destination address, set up by the network administrator; see also alias. SMDS Data Unit See Level 3 Protocol Data Unit (L3-PDU). speed matching A feature that allows two endpoints on the network, running at different speeds, to SMDS Interface Protocol (SIP) The protocol communicate without changing speeds; ¯ow control de®ned at the interface, or boundary, between the must be enabled. network and the customer; a Media Access Control (MAC)-level interface that is a subset of the splice A service that enables the node to connect two Distributed Queue Dual Bus (DQDB) connectionless virtual circuits involving two end devices (both MAC protocol. connected to one host) and to remove the intermediate host. SMDS Switching System (SS) An SMDS switching con®guration of one or more BNS-2000 Stand-alone DDS Drive A portable, AC-powered nodes. tape drive with a SCSI Interface to the Control Computer complex for a CCM con®guration. SNMP agent A software system that implements standalone utility shell A computer interface Simple Network Management Protocol (SNMP) in the program used to execute disk commands and some exchange of network management information with database manipulation commands, running as the only an SNMP manager/station. In a device such as a host system process; see also utility shell (utilsh). or gateway, the agent has a process responsible for performing the network management operations Standard Fiber Trunk (SFT) An interface module requested by the SNMP Manager. for an optical ®ber connection that provides up to 8 Mbps between two nodes, a node and a Multipurpose SNMP Manager A software system that implements Concentrator (MPC), or a node and an ISN network management operations by controlling concentrator. requests for information, setting of variables, and asynchronously receiving traps; see Simple Network Standard Wire Trunk (SWT) A wire interface Management Protocol (SNMP). This manager module that supports 9.6 Kbps to 2.048 Mbps to a system also executes operations that monitor and T1/E1 facility, used for long-distance connections control SNMP agent systems. between a node and a Multipurpose Concentrator

46 Data Networking Products Terminology, Issue 4 ______Glossary

(MPC), or a node and an ISN concentrator, or two StarKeeper II NMS Task Manager A software nodes. application that provides a platform for the StarKeeper II NMS application packages. standby bandwidth The bandwidth expected to be available to support rerouted traf®c on a facility. StarRep Customer Service Systems Advanced Initial standby bandwidth is calculated by subtracting Operations Systems (OSs) that allow telephone the expected bandwidth from the line speed. For any company service representatives to resolve customer point in time, the standby bandwidth is calculated by calls quickly and ef®ciently; via menus, provides subtracting bandwidth currently being used for details on a company's present and upcoming session maintenance reroutes from the initial standby services, correlated data from other systems that bandwidth. pinpoint trouble and recommend corrective actions, and trouble tracking and reporting. standby channel set (CS) In session maintenance, a channel set (CS) that is con®gured to be ready to StarServer FT computer StarServer Fault Tolerant take over the traf®c from an active channel set (CS) computer. on a failed trunk, when using session maintenance. StarWAN Brouter A LAN device that combines StarKeeper II NMS Core System A processor bridging and routing functions. equipped with the StarKeeper II NMS central, or star topology A network con®guration with a central core, system functions and processes; this processor switching node and devices connected to it as "points contains no graphics application packages. on a star." StarKeeper II NMS Co-resident System A station The network access point (endpoint) to which processor equipped with the StarKeeper II NMS core a user device is connected. processes and one or more of the graphics application packages. station ID The local node name, module address, and originating port number to which a user terminal is StarKeeper II NMS Graphics System. A connected. processor, separate from the StarKeeper II NMS Core System, with capabilities for running optional status packet A packet generated by a module that graphics application packages. Speci®cally, this identi®es the module type and the state (whether it is processor supports Task Manager, OPEN LOOK enabled or disabled); Status Packet is the name of a graphical user interface (GUI), cut-through admini- quarterly newsletter for AT&T's data networking stration, StarKeeper II NMS administration customers. connections, graphics administration software, and the status polling A regular check by the Switch optional graphics applications. module of all slots in the network to detect module StarKeeper II NMS Network Builder A high faults and hardware states, such as in or out of resolution bit-mapped, graphics-based application that service; this information is sent to the Control includes network con®guration and administration Computer. tools to provision, maintain, and analyze networks. Stratum 4 Clock (SSM4) A timing device that StarKeeper II Network Management accepts a clock signal from a central source and uses System (NMS) A central system used to view an it to synchronize BNS-2000 AI-T1, AI-T3, TRK-E3A, entire network and to con®gure, monitor, control, and and TRK-T3A modules. diagnose any node in the network. subscriber access termination (SAT) The StarKeeper II NMS Network Monitor A high termination of an SMDS access path, located at the resolution bit-mapped, graphics-based application for customer's site. network fault monitoring and diagnostics that Subscriber Network Interface (SNI) The provides multiple, separate displays of the network boundary between customer premises equipment and network status lists. (CPE) and the network supporting Switched StarKeeper II NMS Performance Reporter A Multimegabit Data Service (SMDS). At this SNI high resolution bit-mapped, graphics-based boundary, or interface, the CPE attaches to an access application that provides menu-based access to facility linking it to a Metropolitan Area Network performance reports and physical and logical network (MAN) Switching System (MSS); only data resources.

Data Networking Products Terminology, Issue 4 47 ______Glossary

belonging to a particular subscriber is transported T across an individual SNI. T1 A digital transmission facility providing 1.544 superblock The memory segment on the operating Mbps of bandwidth; see also DS1, fractional T1 system disk that describes the disk contents. (FT1) service. switch Mode setting device on an interface module or T1.6ca ANSI standard for frame relay. Core Aspects I/O board; see also Switch module. of Frame Protocol For Use With Frame Relay Bearer Service. Switch Cabinet (Shelf), Series M2 A BNS-2000 modular cabinet that holds switch and interface T1.6FR, Annex D ANSI standard for frame relay. modules; see Series M2. Additional Procedures for PVCs Using UI Frames. Switched Multimegabit Data Service (SMDS) A T3 A digital transmission facility providing a total high-speed, connectionless, public, packet switching bandwidth of 44.736 Mbps; see also DS3. service that extends local area network (LAN)-like talk battery A ±48 VDC ®ltered battery power performance beyond the subscriber's premises, across source. a metropolitan or wide area. tandem node A node typically housing trunk switched virtual circuit (SVC) A virtual circuit modules that relays calls between endpoints attached that is established dynamically when an endpoint to other nodes. responds to a DESTINATION: prompt with the address of another endpoint in the network. Task Manager See StarKeeper II NMS Task Manager. Switch module Also Eswitch. A control module that performs packet switching for the node, connects the terminal adapter (TA) A multiport commercial transmit and receive buses, and handles all data and bridge, router, workstation, or host that supports control packets. T1/E1 and T3/E3 interfaces; it is also an ISDN interface. A TA is viewed as a concentrator. switchover See automatic switchover. 10BASE-T An IEEE 802.3 medium speci®cation that Synchronous Data Link Control (SDLC) A link- de®nes the parameters for CSMA/CD access over layer, bit-oriented protocol, similar to HDLC, for the twisted pair using a star topology. The "10" refers to transfer of data between stations in a point-to-point, 10 Mbps and the "T" refers to the twisted pair multipoint, or loop arrangement, using synchronous medium (with a maximum segment length of 100 data transmission techniques. meters). Because CSMA/CD networks, de®ned in Synchronous/Asynchronous Multiplexer IEEE 802.3, commonly called Ethernet, this medium (SAM) A concentrator located remotely from the is sometimes referred to as twisted pair Ethernet. main switching node that provides switched terminal autobaud A feature that automatically asynchronous and transparent synchronous services as determines the speed of the end user's hardware con®gurable options for independently administered device. ports, available in three versions: SAM16 (16 ports), SAM64 (64 ports), SAM504 (504 ports). threshold A sliding window of time (de®ned as a level), set at 2 to 120 seconds, in which lost keep- synchronous data unit (SDU) A device used in alive messages are counted to detect excessive errors pairs that extends synchronous signaling distance. on a trunk; see also error threshold. synchronous transmission A form of time-division multiplexing (TDM) Time sharing of communication in which the data characters and bits a channel by preallocating short time slots to each are transmitted at a ®xed rate with the transmitting transmitter on a regular basis; variations include and receiving device synchronized, eliminating the statistical and asynchronous TDM, which allocate need for a stop and a start bit. slots more ¯exibly. system hang An expression describing a system that timing source See facility; Primary Reference is locked up. Source (PRS).

48 Data Networking Products Terminology, Issue 4 ______Glossary

to-bus or TBUS See transmit bus. trunk, healthy A session maintenance trunk that has not missed receiving a threshold number of loopback traf®c loading A measure of the amount of data packets. A healthy trunk that has the "route trunk (bandwidth) that a Subscriber Network Interface alternate" command issued is still considered healthy; (SNI) injects into or receives from the network. see also trunk, failed. transmission See transmit bus. Trunk Interface Module (TIM) In a remote ISN concentrator, the counterpart wire interface module to transmit bus Also TBUS or to-bus. The portion of the Standard Wire Trunk (SWT), in a node; formal the backplane that carries packets inbound from name for module in ISN nodes and concentrators. sending modules to the switch. trunk latency The interval of time in which a single transmission facility See data transport facility, segment message is received from the backplane and facility. transmitted onto a facility, under normal conditions. Transmit(ted) Data (TD) Data transmitted from a trunk module An interface module to an optical ®ber DTE to a DCE. or wire link between two nodes or between a node Transmitter Clock (TC) A timing signal from a and a concentrator. modem to a terminal transmitter interface that trunk module, failed A trunk module that has been provides signal element timing. removed from service, either manually by an Transparent Synchronous Module±T1 (TSM- administrative command or automatically by the T1) An interface module that provides non-switched system because of a system fault. synchronous or asynchronous connection at speeds trunk, normally routed A session maintenance from 56 Kbps to 1.544 (T1) up to 2.048 Mbps; up to 4 trunk that is not rerouted. ports may be simultaneously con®gured at 384 Kbps. The TSM-T1 can transport, for example, point-to- trunk, rerouted See rerouted trunk. point SMDS circuits or high-speed host-to-host traf®c. Trunk-E3 (TRK-E3) A trunk interface module to an E3 transmission facility that provides connectionless TransVU-2000 A network surveillance and control and connection-oriented data transport. system, customized for operating telephone companies (OTCs), that provides trouble Trunk-E3A (TRK-E3A) A trunk interface module identi®cation for the evolving digital network; it that provides E3 interconnection between BNS-2000 passes alarm and trouble information through to other and ATM switches. support systems and supports an embedded base of Trunk-E3S (TRK-E3S) A trunk interface module to remote telemetry devices. an E3 transmission facility that provides trap See Simple Network Management Protocol connectionless and connection-oriented data transport (SNMP). for SMDS. trunk A facility connecting two nodes; see also Trunk±High Speed (TRK-HS) A trunk interface session maintenance trunk. module that supports ®ber connections between nodes and between nodes and SAM504 and SAM64 trunk call screening A security feature that checks modules. incoming calls from other nodes; see also trunk call screening pro®le. Trunk±Priority Queueing (TRK-PQ) A trunk interface module that supports wire connections for trunk call screening pro®le An administered set of multi-protocol traf®c with fair queueing, enhanced security patterns applicable to one or more trunks; see buffering, and enforcement of committed information also pro®le. rate (CIR) for frame relay traf®c at up to T1/E1 rates. trunk, failed A session maintenance trunk that has Trunk-T3 (TRK-T3) A trunk interface module that missed receiving a threshold count of loopback supports connectionless and connection-oriented packets and whose circuits should be moved to traf®c between nodes at transmission speeds up to T3 reroute paths; see also trunk, healthy. (DS3).

Data Networking Products Terminology, Issue 4 49 ______Glossary

Trunk-T3A (TRK-T3A) A trunk interface module sub-networks. UNMA is based on an OSI network that provides T3 interconnection between BNS-2000 management protocol. and ATM switches, and supports connectionless and connection-oriented data transport for both Uniform Alarm Interface (UAI) A standard for IntraLATA and private InterLATA traf®c at T3 (DS3) sending/receiving alarms to/from StarKeeper II NMS. rates. uninterruptible power supply (UPS) A device Trunk-T3I (TRK-T3I) A two-board trunk interface that provides power for network systems if a power module that supports connectionless Interexchange outage occurs or if the power is uneven. Carrier (IXC) data transport at T3 (DS3) rates. user channel A channel on a trunk that is speci®ed Trunk-T3S (TRK-T3S) A trunk interface module by the network administrator for the normal transport that supports connectionless and connection-oriented of user data; user channels are distributed across data transport for both IntraLATA and private active channel sets (CSs). InterLATA traf®c at T3 (DS3) rates. utility backbone network A BNS-2000 network trunk weight A value assigned to each trunk used to that is used as a higher tier network to an existing determine the best route between nodes. The routing Datakit II VCS network. algorithm favors a trunk with the lowest value, or the least weighted path, because that is the shortest, and utility commands Commands used for checking and most ef®cient, transmission path. Trunk weight correcting the Control Computer ®le system; for allows a network administrator to control traf®c formatting, copying, and verifying disk cartridges; distribution. and for creating historical records. two-way (2-way) group The transmission directions utility mode A software state during which of a group assigned to devices that can originate or commands can be used for checking and correcting receive calls to and from network endpoints. the Control Computer ®le system; for formatting, copying, and verifying disk cartridges; for creating TY12 A terminal interface module that supports up to historical records; and to install software. 12 asynchronous user ports. utility networking Describes switching of frame relay and other traf®c. U utility shell (utilsh) A computer interface program UART universal asynchronous receiver/trans- used to execute disk commands and some of the mitter. An integrated circuit that converts the serial database manipulation commands concurrently with data of a communication line to the parallel data used the system processes; see also standalone utility internally in a system, and vice versa. shell. UB speci®cation An SMDS interface speci®cation developed by Ungermann-Bass, et al. and open to all vendors; uses HDLC encapsulation to transfer data V from the router to the DSU. The physical interface V.11 ITU-T/CCITT Recommendation. A standard for can be V.35, RS-449, or HSSI. De®nes four logical data communication: Electrical Characteristics for links between the two devices; hardware reset, data Balanced Double-current Interchange Circuits for transfer and ¯ow control, link performance General Use With Integrated Circuit Equipment in the monitoring, and element management. Field of Data Communications. un-expanded Service Region (SR) When routing V.24 ITU-T/CCITT Recommendation. A standard for messages from the source to their intended data communication, comparable to RS-232-C: List destination, if a node makes decisions based on of De®nitions for Interchange Circuits between Data Service Regions (SRs) only, these SRs are described Terminal Equipment (DTE) and Data Circuit as un-expanded. Terminating Equipment (DCE). Uni®ed Network Management Architecture V.29 ITU-T/CCITT Recommendation. A standard (UNMA) AT&T's comprehensive end-to-end format for half-duplex 4800- and 9600-baud serial integration of management for a wide variety of data transmission over telephone lines. multidomain, multivendor, voice/data networks and

50 Data Networking Products Terminology, Issue 4 ______Glossary

V.32bis ITU-T/CCITT Recommendation. A standard W format for data transmission at up to 19.6 Kbps over telephone lines ("bis" means an extension of the warm reboot To reinitialize the system from a original standard). powered state (only the Control Computer is rebooted); see also cold reboot. V.34 ITU-T/CCITT Recommendation. A standard format for data transmission at up to 28.8 Kbps over warm spare controller A backup Control telephone lines; see also V.fast. Computer with its power switched on.

V.35 ITU-T/CCITT Recommendation. A standard for wide area network (WAN) A communications the physical layer of the X.25 protocol, describing the network that can cover an unlimited distance. electrical, mechanical, and functional characteristics of the connections between devices exchanging data window A ¯ow and error control method for virtual in serial binary form. circuits that limits the number of packets one endpoint can send before waiting for acknowledgment from the V.fast A preliminary protocol that does not conform receiver. precisely to the V.34 standard. vertical redundancy check (VRC) An error window size The number of outstanding packets that checking technique in which a check, or parity, bit is can be sent before an acknowledgment is required; added to each character in a message so that the see also window. number of bits in each character, including the parity bit, is odd (for odd parity) or even (for even parity); see also cyclic redundancy check (CRC), X longitudinal redundancy check (LRC). X.3 ITU-T/CCITT Recommendation. A standard for a vertical services Context switching, protocol packet assembly/disassembly (PAD) facility in a conversion, security protection, and similar services public data network. implemented via an applications processor module. X.3 pro®le An administered set of values de®ning virtual call Also switched virtual circuit (SVC). A access to a PAD by an asynchronous terminal; see term for a data call; a temporary association between also pro®le. two X.25 DTEs. virtual circuit Network facilities that provide an end X.25 ITU-T/CCITT Recommendation. user with service that is equivalent to a physical Recommendations for standard communications circuit. Data in a virtual circuit can be routed protocols for access to packet-switched networks, dynamically through a variety of physical paths de®ning the interface between a host and network, between endpoints, allowing many virtual circuits to including: 1. A standard describing HDLC protocol share the same transmission facilities concurrently. for the interface between a synchronous host and a packet-switched public data network (PDN); includes virtual multipoint bridging The multiplexing of Link Access Procedure Balanced (LAPB). 2. A physically different access lines onto a single standard for the DTE to DCE interface between a multidrop host line, by which the node allows the host synchronous host and a packet-switched data network. to see the connection as a single multipoint line; see also fanout. X.25 module This interface module supplies X.25 voice/data multiplexer (VDM) A device that allows services, allowing X.25 hosts and asynchronous the sending and receiving of simultaneous voice and terminals to connect to a public data network (PDN) data transmissions through existing telephone lines. or other X.25 hosts. The module provides 4 RS-232- C ports that can be con®gured individually at speeds voltage range selector switch Also HIGH-LOW from 1200 to 19.2 Kbps, or 1 port that can be switch; located on the off-line power supply switch. con®gured at up to 64 Kbps with the remaining 3 VT A Digital Equipment Corporation code for a series con®gured at up to 9.6 Kbps. The module supports of computer terminals; most asynchronous computer X.121 address translation via gateway tables. terminals are VT-compatible and most PCs can emulate the VT- series.

Data Networking Products Terminology, Issue 4 51 ______Glossary

X.25P module This interface module supplies X.25 (PVC) calls among X.25 networks. Address services, allowing X.25 hosts and asynchronous translation of X.121 addresses from one numbering terminals to connect primarily to other X.25 hosts and scheme to the Datakit/BNS-2000 numbering scheme network elements. The module capabilities include: is accomplished via gateway address tables. extended I-frame numbering, larger packet and X.121 ITU-T/CCITT Recommendation. A standard window sizes and better performance than the X.25 that de®nes an international numbering scheme for module (con®gurable on a port-by-port basis) and packet-switched public data network (PDN) addresses packet segmentation. The module can provide 4 V.35 (internetworking of DTEs worldwide), consisting of a ports con®gured at speeds up to 64 Kbps; or 8 ports data network identi®cation code (DNIC) and a individually con®gured at up to 19.2 Kbps. network terminal number (NTN). X.28 ITU-T/CCITT Recommendation. A standard for X.213 ITU-T/CCITT Recommendation. A standard commands sent by terminals to a packet assembler/ that de®nes a network for Open Systems disassembler (PAD) and for service signals Interconnection (OSI). (messages) sent by the PAD to terminals; this de®nes the interface between an asynchronous terminal and X.225 ITU-T/CCITT Recommendation. Connection- an X.25 network. oriented (CONS) session protocol, equivalent to ISO 8327 (for OSI Session Layer 5). x28sig X.28 packet assembler/disassembler identi®cation (PAD ID) service signal for the PAD X.400 ITU-T/CCITT Recommendation. A standard user. for electronic message handling (email).

X.29 ITU-T/CCITT Recommendation. A standard for X.500 ITU-T/CCITT Recommendation. A standard the communication procedures between an X.25 DTE for directory services. or packet assembler/disassembler (PAD) and XON/XOFF Control characters used for software ¯ow another PAD. control in a data connection, usually the ASCII DC1 X.75 ITU-T/CCITT Recommendation. A standard that and DC3 characters. In-band ¯ow control protocol speci®es the interface between X.25 networks; the uses XOFF Control S to suspend data ¯ow standard for international gateway services between and XON Control Q to resume data ¯ow. packet-switched networks. X-Splicer A software application that allows an asynchronous endpoint to call a DKAP module, via a X.75 module An interface module that functions as a switched virtual circuit (SVC), which then sets up a national or international gateway to route switched PVC call to an X.25 endpoint, splices the calls, and virtual circuit (SVC) or permanent virtual circuit drops out of the virtual circuit.

52 Data Networking Products Terminology, Issue 4 ______

ASCII and EBCDIC Character Codes

For quick reference, this table gives the meanings of abbreviations.

TABLE 1. ASCII and EBCDIC Codes ____________ASCII  Mnemonic  EBCDIC      _______Hex Octal  Characters  Meaning  Hex  Prints as  _______00 00  NUL  Null  00         ______01 01  SOH  Start of Header  01   _______02 02  STX  Start of Text  02       ______03 03 ETX  End of Text 03        ______04 04  EOT  End of Transmission  04   _______05 05  WRU/ENQ  Enquire  09       ______06 06 RU/ACK  Acknowledge 06        ______07 07  BELL/BEL  Bell  07  bell  _______08 10  BS  Backspace  08         ______09 11 TAB/HT Horizontal Tab 05       _______0A 12  LF  Line Feed  25  line feed  _______0B 13  VT  Vertical Tab  0B         ______0C 14  FORM/FF  Form Feed  0C   _______0D 15  CR  [Carriage] Return  15  CR      ______0E 16 SO  Start of Header 0E        ______0F 17  SI  Shift In  0F   _______10 20  DLE  Delete  10       ______11 21 X-ON/DC1  Device Control 1 11        ______12 22  TAPE/DC2  Device Control 2  12   _______13 23  X-OFF/DC3  Device Control 3  13         ______14 24 DC4 Device Control 4 14       _______15 25  NAK  Negative Acknowledgment  0A   _______16 26  SYN  Synchronize  16         ______17 27  ETB  End of Transmission Block  17   _______18 30  CAN  Cancel  18  

Data Networking Products Terminology, Issue 4 53 ______ASCII/EBCDIC Character Codes

TABLE 1. ASCII and EBCDIC Codes (continued) ____________ASCII  Mnemonic  EBCDIC      ______Hex Octal Characters  Meaning Hex  Prints as       _______19 31  EM  End of Medium  19       ______1A 32 SS  Start of Special Sequence 1A        ______1B 33 ESC Escape 1B       _______1C 34  FS  File Separator  1C       ______1D 35 GS  Group Separator 1D        ______1E 36  RS  Record Separator  1E   _______1F 37  US  Unit Separator  1F       ______20 40 blank  Space Bar 40  blank       ______21 41  !   5A  !  _______22 42  "   7F  "      ______23 43 #  7B  #       _______24 44  $   5B  $      ______25 45 %  6C  %       ______26 46 & 50 &       _______27 47  ′   7D  ′      ______28 50 (  4D  (       ______29 51  )   5D  )  _______2A 52  *   5C  *      ______2B 53 +  4E  +       ______2C 54  ,   6B  ,  _______2D 55  -   60  -      ______2E 56 .  4B  .       _______2F 57  /   61  /      ______30 60 0  F0  0       ______31 6l 1 F1 1       _______32 62  2   F2  2      ______33 63 3  F3  3       ______34 64  4   F4  4  _______35 65  5   F5  5      ______36 66 6  F6  6       ______37 67  7   F7  7  _______38 70  8   F8  8      _______39 71  9   F9  9 

54 Data Networking Products Terminology, Issue 4 ______ASCII/EBCDIC Character Codes

TABLE 1. ASCII and EBCDIC Codes (continued) ____________ASCII  Mnemonic  EBCDIC      ______Hex Octal Characters  Meaning Hex  Prints as       _______3A 72  :   7A  :      ______3B 73 ;  5E  ;       ______3C 34 < 4C <       _______3D 75  =   7E  =      ______3E 76 >  6E  >       ______3F 77  ?   6F  ?  _______40 100  @   7C  @      ______41 101 A  C1  A       _______42 102  B   C2  B  _______43 103  C   C3  C      ______44 104 D  C4  D       _______45 105  E   C5  E      ______46 106 F  C6  F       ______47 107 G C7 G       _______48 110  H   C8  H      ______49 111 I  C9  I       ______4A 112  J   D1  J  _______4B 113  K   D2  K      ______4C 114 L  D3  L       _______4D 115  M   D4  M  _______4E 116  N   D5  N      ______4F 117 O  D6  O       _______50 120  P   D7  P      ______51 121 Q  D8  Q       ______52 122 R D9 R       _______53 123  S   E2  S      ______54 124 T  E3  T       ______55 125  U   E4  U  _______56 126  V   E5  V      ______57 127 W  E6  W       _______58 130  X   E7  X  _______59 131  Y   E8  Y 

Data Networking Products Terminology, Issue 4 55 ______ASCII/EBCDIC Character Codes

TABLE 1. ASCII and EBCDIC Codes (continued) ____________ASCII  Mnemonic  EBCDIC      ______Hex Octal Characters  Meaning Hex  Prints as       _______5A 132  Z   E9  Z      ______5B 133 [ or 1  4F         ______5C 134 \ 4A ¢       _______5D 135  ]   5F       ______5E 136 ↑ or à  6A        _______5F 137  ← or -   6D  -         .    .   0       ______.        .       .     0      ______.         ______7E 176  ESC  Escape  1B   _______7F 177  DEL  Delete  FF  

56 Data Networking Products Terminology, Issue 4