1/28 Digital Carrier Systems Surasak Sanguanpong [email protected] http://www.cpe.ku.ac.th/~nguan Last updated: 11 July 2000 Applied Network Research Group Department of Computer Engineering, Kasetsart University 2/28 Digital carrier standard z T-carrier z North America, Japan z E-carrier z Europe, South America z SONET/SDH z world-wide new standard Applied Network Research Group Department of Computer Engineering, Kasetsart University 3/28 Comparison of the layer OSI T-1 SONET/SDH Application Presentation Session Transport Network Data link Physical Physical Physical Applied Network Research Group Department of Computer Engineering, Kasetsart University 4/28 Organization of telephone services The telephone message are routed through : • a switch at the central office (CO) for a local calls Toll • a switching center for out-of-area calls • toll exchanges for long distance calls exchange CO zz The original IOT Area toll connectionsconnections were were made made change over an analog system calledcalled N-carrier. Inter-office to local zz The T-carrier system CO trunk CO call CO was the first widely (IOT) deployed digital transmissiontransmission system system local loop switch Applied Network Research Group Department of Computer Engineering, Kasetsart University 5/28 T-1 carrier system z 24 voice channels are sampled, quantized and encoded into a TDM PCM signal CH1 z T-1 carrier has a transmission rate of 1.544 Mbps CH2 PCM CH1 CH2 CH3 CH23 CH24 CH23 CH24 zz Bipolar encoding xxx x xxxx zz B8ZS for T-1 zz B3ZS for T-3 MSB LSB (sign bit) zz Full duplex zz Channel-based digital transmission Applied Network Research Group Department of Computer Engineering, Kasetsart University 6/28 T-1 frame 1 frame bit T-1 bit rate : (24x8 +1 bit)/125 µs = 1.544 Mbps 125 µs CHCH 1 1 CHCH 2 2 CHCH 24 24 .............. (8(8 bit) bit) (8(8 bit) bit) (8(8 bit) bit) 192 bits zz The early frame standard called D1, D2 and D3 were used. zz There are two framing standard for the T-1, called D4 (superframe)(superframe) and andextended extended superframe superframe(ESF) (ESF) zz The T-3 used the M13 framing Applied Network Research Group Department of Computer Engineering, Kasetsart University 7/28 Frame and Superframe 1 superframe = 12 frames (2316 bits in 1.5 ms) Fodd 10 101 0 Feven 0011 1 0 Fcombine 100011011100 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 Frame # F data (192 bits) z T-1 carrier frames are transmitted in 1 1 dddd dddd -- dddd dddd groups of 12 called superframes 2 0 dddd dddd -- dddd dddd 3 0 dddd dddd -- dddd dddd z F-bit in even-numbered frame has a 4 0 dddd dddd -- dddd dddd pattern of 101010 for synchronization 5 1 dddd dddd -- dddd dddd 6 1 dddd dddX -- dddd dddX z Signaling information is accomplished 7 0 dddd dddd -- dddd dddd by robbing the LSB position of each 8 1 dddd dddd -- dddd dddd 9 1 dddd dddd -- dddd dddd channel. This is performed only in the 10 1 dddd dddd -- dddd dddd 6th and 12th frame to keep distortion 11 0 dddd dddd -- dddd dddd minimum 12 0 dddd dddX -- dddd dddX Applied Network Research Group Department of Computer Engineering, Kasetsart University 8/28 Extended Superframe 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Remote configuration and monitoring (4Kbps) CRC Frame synchronization z ESF framing groups 24 frames into an ESF superframe z every 193rd bit are used for the above purposes Applied Network Research Group Department of Computer Engineering, Kasetsart University 9/28 Multiplexing z CSU (Channel Service Unit) router phone z performs several protective and diagnostic functions z DSU (Data Service Unit) z convert the digital data from a (for example) router to T1 voltages and MUX encoding. CSU/DSU T-carrier Applied Network Research Group Department of Computer Engineering, Kasetsart University 10/28 T-carrier Digital Multiplexing Hierarchy T1 DS1 DS1 Two 1.544 Mbps DS1 channels are multiplexed into a single 3.152 Mbps DS1C channel Two DS1C channels are multiplexed into a single 6.312 Mbps DS2 channel DS1C DS1C T1-C Seven DS2 channels are T2 multiplexed DS2 into a single DS2 DS2 DS2 DS2 DS2 DS2 44.736 Mbps DS3 channel T3 DS3 DS3 DS3 DS3 DS3 DS3 Six DS3 channels are multiplexed into a single 274.176 Mbps DS4 channel DS4 T4 Applied Network Research Group Department of Computer Engineering, Kasetsart University 11/28 E1-frame 30 voice channels+2 control channels 125 µs CHCH CHCH CHCH CHCH CHCH 00 11 22 1616 3131 frame signaling synchronization channel E1 bit rate : (32x8 bit)/125 µs=2.048Mbps Applied Network Research Group Department of Computer Engineering, Kasetsart University 12/28 E-carrier Thirty 64 Kbps channels are multiplexed to Four E1 channels are create one 2.048 E1 E1 E1 E1 multiplexed into a single Mbps E1 8.448 Mbps E2 channel channel Four E2 channels E2 E2 E2 E2 are multiplexed into a single 34.368 Mbps E3 channel Four E3 channels are multiplexed E3 E3 E3 E3 into a single 139.264 Mbps E4 channel Four E4 channels are multiplexed E4 E4 E4 E4 into a single 565.148 Mbps E5 channel E5 Applied Network Research Group Department of Computer Engineering, Kasetsart University 13/28 Digital carrier comparison Europe x31 E1 x4 E2 x4 E3 x4 E4 x4 E5 2.0482.048 8.4488.448 34.36834.368 139.264139.264 564.992564.992 x24 T1 x2 T1C x2 T2 x7 T3 x6 T4 USA 6464 1.5441.544 3.1523.152 6.3126.312 44.73644.736 274.176274.176 x24 J1 x4 J2 x5 J3 x3 J4 x4 J5 Japan 1.5441.544 6.3126.312 32.06432.064 97.72897.728 397.200397.200 Applied Network Research Group Department of Computer Engineering, Kasetsart University 14/28 PDH almost synchronous z PDH = Plesiochronous Digital Hierarchy z Digital transmission systems (T-carrier, E carrier) combine lower order multiplex stream to get higher bit rate z Each device runs its own free-running clock z Different streams have small differences in clock signals. z Solve by adding justification bit Applied Network Research Group Department of Computer Engineering, Kasetsart University 15/28 PDH deficiencies (I) z Lack of flexibility z impossible to identify a lower bit rate channel from the higher-order bit stream. Extraction of 2 Mbps channel from 140 Mbps channel 34 Mbps 140 M 140 140 140 M LTE 34 LTE 34 8 Mbps 34 34 8 8 2 Mbps demux the high bit rate down to the lower level 8 8 remux back into higher 2 2 level for onward transmission Customer site Applied Network Research Group Department of Computer Engineering, Kasetsart University 16/28 PDH deficiencies (II) z Lack of performance z No standard for monitoring the performance of traffic channel z No management channel z Lack of ‘Mid-Fibre meet’ z undefined interface specification on the line side of a line transmission PDH SDH LTE standard Network G.703 non standard interface line code and Node Interface (NNI) optical levels functional integration of MUX and LTE Applied Network Research Group Department of Computer Engineering, Kasetsart University 17/28 SDH&SONET z What is SDH/SONET ? z Standard interface developed for using in the public network z multiplexing standard for optical fiber transmission z SONET = Synchronous Optical Network z refers to the system used within the U.S. and Canada z SDH = Synchronous Digital Hierarchy z international community term (ITU-T recommendations) Applied Network Research Group Department of Computer Engineering, Kasetsart University 18/28 SDH/SONET goals z Goals z make it possible for different carrier to interwork z unify the U.S., European and Japanese digital system z Provide a way to multiplex multiple digital signal together z provide support for operations, administration, and maintenance z Characteristics z use single master clock to synchronize z Bit stream can be a added or extracted directly z Basic transmission rate = 155.52 Mbps Applied Network Research Group Department of Computer Engineering, Kasetsart University 19/28 SDH/SONET topology z Typical SDH/SONET DS1 DS1 DS3 DS3 topology is a dual ring (fiber optics) z Oneringistheworking TA TA facility, and the other ring is ADM ADM the protection facility (standby) z End-user devices operating on LANs or other transport DCC systems are attached through terminal adapter DS1 Other SONET/SDH DS3 networks Applied Network Research Group Department of Computer Engineering, Kasetsart University 20/28 SDH/SONET System z consists of switches, mux and repeaters mux repeaters mux repeaters mux section section section section line line path Applied Network Research Group Department of Computer Engineering, Kasetsart University 21/28 Multiplexing level SONET SDH Bit rate (Mbps) STS-1/OC-1(Not defined) 51.84 STS-3/OC-3 STM-1 155.52 STS-9/OC-9 STM-3 466.56 STS-12/OC-12 STM-4 622.08 STS-18/OC-18 STM-6 933.12 STS-24/OC-24 STM-8 1244.16 STS-36/OC-36 STM-12 1866.24 STS-48/OC-48 STM-16 2488.32 STS = Synchronous Transport Signal OC = Optical Carrier STM = Synchronous Transport Module Applied Network Research Group Department of Computer Engineering, Kasetsart University 22/28 SDH Basic Frame structure 1frame=2430bytesin125µs 1 2345 6 789 STM-1 row/column mapping 9bytes 261 bytes Overhead : SOH for system management 3bytes information (OAM) SOH = Section Overhead LOH = Line Overhead 9bytes Payload TOH = Transport Overhead LOH 6bytes Payload : user data TOH Applied Network Research Group Department of Computer Engineering, Kasetsart University 23/28 SONET Basic Frame structure 1 frame = 810 bytes in 125 µs 1 234567 89 STS-1/OC1 row/column mapping 3bytes 87 bytes Overhead : SOH for system management 3bytes information SOH = Section Overhead LOH = Line Overhead 9bytes Payload TOH = Transport Overhead LOH 6bytes Payload : user data TOH Applied