US006516352B1 (12) United States Patent (10) Patent N0.: US 6,516,352 B1 Booth et al. (45) Date of Patent: Feb. 4, 2003

(54) NETWORK INTERFACE SYSTEM AND 6,345,310 B1 * 2/2002 Allison et al...... 709/250 METHOD FOR DYNAMICALLY SWITCHING * Cited by examiner BETWEEN DIFFERENT PHYSICAL LAYER DEVICES Primary Examiner—Ario Etienne Assistant Examiner—Bradley Edelman (75) Inventors: Bradley J. Booth; Nestor A. FeSaS, Jr., (74) Attorney, Agent, or Firm—Blakely, Sokoloff, Taylor & both of Austin; Robert 0. Sharp, Zafman LLP Round Rock' William Kass Austin all of TX (Us) ’ ’ ’ (57) ABSTRACT _ _ A system and method for dynamically switching between (73) Asslgnee: Intel corporatlon’ Santa Clara’ CA different physical layer devices (PHYs) in a network inter (US) face. The system comprises a network interface in a network . . . . . device, e. ., a network card in a com uter s stem which ( * ) Nonce: Sub]eCt.tO any dlsclalmer’. the term of thls includes ag?rst PHY device and a secorIfd PHYydevice. The Patent 15 extended or adjusted under 35 ? t PHY device is cou led to a ?rst transmission medium U.S.C. 154(b) by 0 days. (suchrs as ?ber-optic. cable)p which. requires. a continuous. connection to the computer system when active. For a (21) APP1~N0~309/135’074 SERDES device, this continuous connection is required (22) Filed: Aug 17’ 1998 because the PHY needs ~constant access to its physical coding sublayer (PCS), which is located external to the PHY. (51) Int. Cl.7 ...... G06F 15/16 The second PHY device is coupled to a second transmission (52) 709/250; 370/463 medium (such as copper cable) which does not require this (58) Field of Search ...... 709/250, 228; Continuous Connection This Second PHY may be, for 370/463; 340/2, 8, 22, 825; 710/131, 38 example, a G/MII device,which includes the PCS internally. The network interface card further includes a link switching (56) References Cited unit, a physical layer interface unit, and a control unit. The control unit generates a select signal indicating which physi U'S' PATENT DOCUMENTS cal layer device is currently selected. Accordingly, the link 5,530,894 A * 6/1996 Farrell et a1. " 709/250 switching unit transfers data between the physical layer 5,768,530 A * 6/1998 sandor? ______709/233 interface unit and the currently selected physical layer 5,793,983 A * 8/1998 Albert et al. .. 709/239 device. The physical layer interface unit receives incoming 5,819,110 A * 10/1998 Motoyama 710/15 data from either the link switching unit or an external 578287655 A * 10/1998 M011“? ct a1~ 370/236 interface of the network interface card. The physical layer 5’838’989 A * 11/1998 Hut_°T_11S°n et a1‘ 710/11 interface unit includes two sub-layers corresponding to each 5’864’535 A * 1/1999 Bfislhco """"" " 370/231 of the physical devices. These sub-layers each produce 5,867,662 A * 2/1999 Riggs ...... 709/228 . . . . 5,918,021 A * 6/1999 Aditya 709/235 outgoing data in ‘response’ to the incoming data, and the 5,982,854 A * 11/1999 Ehreth ...... 379/56.2 aPPYOPHate Outgolng data 15 Chosen based on the Currently 6,070,199 A * 5/2000 Axtman etal...... 710/1 Selected Physical layer device 6,098,103 A * 8/2000 Dreyer et al. 709/234 6,308,239 B1 * 10/2001 Osakada et al...... 710/131 48 Claims, 17 Drawing Sheets

SELECT GENERATION UNIT 414 ‘ SELECT STATUS/ SIGNAL CONTROL 416 ‘ SERDES TO LAN 300 ' DEVICE > VIA FIBER ‘ L|NK ' m OPTIC CABLE I/F ‘ SWITCH FROM m ' m G/MII TO K) :> < PHY LAN 300 BUS MAC 7 DEVICE VIA COPPER 214 DEVICE m CABLE M NETWORK G/M" INTERFACE CARD PHY DEVICE :IAQ U.S. Patent Feb. 4, 2003 Sheet 1 0f 17 US 6,516,352 B1

.GE_. $2moi“: E265356m2 K .EEQEQQE26 NP

ESQES55mm U.S. Patent Feb. 4, 2003 Sheet 2 0f 17 US 6,516,352 B1

MAIN MEMORY 1_30 ii 112 a LAN CPU CONTROLLER .112 120 132 i; a ?v 122 PHY < > PHY MANAGEMENTINTERFACE < > DEVICEm

EXTERNAL FIG. 2A NETWORK (PRIOR ART) U.S. Patent Feb. 4, 2003 Sheet 3 0f 17 US 6,516,352 B1

fwo MAIN MEMORY m

LAN CPU 8 CONTROLLER m > LZQ 132% $134 PHY DEVICE 130

EXTERNAL NETWORK FIG. 2B L0 (PRIOR ART)

U.S. Patent Feb. 4, 2003 Sheet 6 6f 17 US 6,516,352 B1

:63 $562855“@5128mm5 $5128mg,$5128£5 DmoomI\ n_ :65:65 ao5mm:55.6 mu ..M I255E5 182288;WML/ UH Um3: QWHMT $52

a 22 mwmm 55228.$8” l .GEme. U.S. Patent Feb. 4, 2003 Sheet 7 0f 17 US 6,516,352 B1

.QEm A A

20E

U.S. Patent Feb. 4, 2003 Sheet 9 0f 17 US 6,516,352 B1

"8mg 5.518.5% womzmE>> mamE365%s gzssmdwg U.S. Patent Feb. 4, 2003 Sheet 10 0f 17 US 6,516,352 B1

SWITCH SIGNAL PHY N T E R F A C E UNIT 412 TRANSMIT SWITCH 610 BUS 540B

TXEN/TXD8 TXER/TXD9

I | I |.____.______I BUS 522 FIG. 8A U.S. Patent Feb. 4, 2003 Sheet 11 0f 17 US 6,516,352 B1

PHY INTERFACE ' I UNIT ___ m RECEIVE SWITCH 612 BUS 540A

RXDO '

7 BUS 542A

FIG. 8B U.S. Patent Feb. 4, 2003 Sheet 12 0f 17 US 6,516,352 B1

/ 700

’\/ MONITOR LINK ‘ >

INTERRUPT HOST CPU + 718 NO

YES 720 SWITCH PHY /\_/ (SEE FIG. 10)

4 I V 722 724 726 MANUAL NO SETUP PHY ’\/ CONFIGURATION AND RESTART v \ MODE? AUTO-NEGOTlATlON YES SETUP PHY

Jr

‘ 1 REPORT J32 * LINK ACTIVE + L

FIG. 9 U.S. Patent Feb. 4, 2003 Sheet 13 0f 17 US 6,516,352 B1

/ 800 812 '-\/ FIND NEW PHY T 814 NEED T0 N0 SWITCH THE # INTERFACE?

816 SET PHY TO ’\/ 825 SET PHY TO ’\/ 'ND'gQTEIEgNG INDICATE GOING + OFF-LINE ,318 T 817 ISOLATE THE PHY ISOLATE THE PHY \/

822 ‘I 826 WRITE 1 T0 SWITCH »\/ WRITE I To SWITCH v l/F SELECT DATA 507 INPUT DATA 505 T 824 T 828 WRITE 0 TO SWITCH w WRITE 0 To l/F w INPUT DATA 505 SELECT DATA 507 4 + ‘Y I 830 BRING UP NEW PHY M AND DE-ISOLATE T 832 TO STEP 722 OF M FIG. 9 FIG. 10

U.S. Patent Feb. 4, 2003 Sheet 15 0f 17 US 6,516,352 B1

1002 ,(1000 Auto-poll Enabled by Host CPU N0 Valid PHY

Valid PHY

1016

Auto-poll N0 Read

Yes FIG. 12 U.S. Patent Feb. 4, 2003 Sheet 16 0f 17 US 6,516,352 B1

/ 1100 1102 "\/ INITIALIZE T 1104 CHECK FOR COUNTER M ' TIMEOUT ‘I 1106 1120 N0 COUNTER TIMEOUT RESET V TIMEOUT? A 1108 AUTO-POLL w READ T 1110 COMPARE WITH CPU v READ DATA + 1112 MISMATCH? NO >

1114 GENERATE INTERRUPT “/ S ‘ H16 1118 ’\/ GENERATE INTERRUPT -_-_> CLEARED? I I0

FIG. 13 U.S. Patent Feb. 4, 2003 Sheet 17 0f 17 US 6,516,352 B1

1200 1202 / START /\/

1204 ENABLE ’\/ AUTO-POLLING

l 1206 RECEIVE PHY INTERRUPT

i ' 1208A ' I RECEIVE ’\/ INTERRUPT HOST CPU STATUS DATA READ i l m

CLEARS INTERRUPT w i l

I ------_ - - _ - - - - _ - - _ - - - n ------_ _ _ _ ------_ - - — . and

FIG. 14 US 6,516,352 B1 1 2 NETWORK INTERFACE SYSTEM AND location called a hub. This allows for easy modi?cation of METHOD FOR DYNAMICALLY SWITCHING the network (adding, deleting, moving computers) without BETWEEN DIFFERENT PHYSICAL LAYER having to bring down the entire network. Furthermore, the DEVICES entire network does not go down if one individual connec tion is broken. FIELD OF THE INVENTION Hybrid topologies combining one or more of the above network con?gurations may also be utiliZed to further This invention relates to the ?eld of interface hardware for increase ?exibility. local area networks, and more particularly to a network In order to permit a full range of data communications interface which ef?ciently switches between different links 1O to a local area network. among disparate data equipment and networks, the Interna tional Standards OrganiZation (ISO) developed a reference DESCRIPTION OF THE RELATED ART model known as Open System Interconnection (OSI) in Local area networks (LANs) have forever changed cor 1974. OSI is a seven-layer model which ideally allows porate and personal computing. First used for sharing simple standardiZed procedures to be de?ned, enabling the inter 15 information and resources among personal computer users, connection and subsequent effective exchange of informa LANs have dramatically evolved over the last ten years to tion between users. OSI de?nes the functions of each layer become the premier strategic computing platform for busi but does not provide the software and hardware to imple nesses today. All but the smallest corporations rely on LAN s ment the model. The model’s goal is to set a standard for and their dependence and appetite for this technology shows communication product vendors. The seven layers in no signs for slowing. Indeed, LANs have matured to the sequence from top (layer 7) to bottom (layer 1) are as point of peer status with personal computers themselves. As follows: application, presentation, session, transport, the market and deployment of ever more powerful comput network, data link, and physical. A given network does not ers continues to grow, the expectation of providing equally have to implement each layer of OSI to be compatible with high performance network connectivity grows as well. this standard. 25 One example of a local area network, LAN 10, is depicted Layer 7, the application layer, is responsible for special in FIG. 1. As shown, LAN 10 includes a server computer 14 iZed network functions such as ?le transfer, virtual terminal, and a plurality of client computers 16. Computers 14 and 16 and electronic mail. The purpose of this layer is to serve as are coupled by LAN hardware 12, which includes the actual the window between correspondent application processes transmission medium (e.g., ?ber-optic cable or copper cable which are using the OSI to exchange meaningful data. such as unshielded (UTP)) as well as various Examples of application layer protocols include SNMP, network hardware elements such as hubs, switches and RLOGIN, TFTP, FTP, MIME, NFS, and FINGER. Layer 6, routers. the presentation layer, is responsible for data formatting, The advantages of LANs are numerous. By providing character code conversion, and data encryption of data easy access to shared data (on server computer 14, for 35 generated in the application layer. This layer is not always example), computer users are allowed to interpolate more implemented in a network protocol. Layer 5, the session effectively. Users are also able to share expensive peripheral layer, provides for negotiation and establishment of a con devices such as printers, faxes and CD-ROMs between nection with another node. To do this, the session layer client computers 16. These peripheral devices are also provides services to (a) establish a session connection coupled to the various client computers via LAN hardware between two presentation entities and (b) support orderly 12. The cost of client computers may also be decreased by data exchange interactions. This includes establishing, lessening the needs for high-capacity disk drives on indi maintaining, and disconnecting a communication link vidual workstations. By storing data on one or more central between two stations on a network, as well as handling servers accessible through the LAN, this also provides an name-to-station address translation. (This is similar to plac ing a call to someone on the telephone network with easier solution for backup of vital data. 45 ALAN includes two or more computer systems which are knowing only his/her name, wherein the name is reduced to physically and logically connected to one another. The type a phone number in order to establish the connection). of connection between the computer systems is referred to as Layer 4, the transport layer, handles the reliable end-to the topology of the LAN. In a bus topology, computer end delivery of data. This layer ensures that data is delivered systems and devices are attached at different points along a in the same order that it was sent. It also ensures that data bus. Data is then transmitted throughout the network via the is transmitted or received without error, and in a timely cable. The speed of transmission of the network is governed manner. Transmission control protocol (TCP) is a common by the type of cable. One disadvantage of this topology is transport layer protocol. Layer 3, the network layer, routes that a break in the cable disables the entire network. packets of information across multiple networks, effectively Furthermore, provisions have to be made for re-transmission 55 controlling the forwarding of messages between stations. On of data in cases in which multiple computers contend for the the basis of certain information, this layer will allow data to bus (cable) at the same time, causing data collision (and How sequentially between two stations in the most economi possible loss of data). cal path both logically and physically. This layer allows Another type of topology is the ring topology, in which units of data to be transmitted to other networks though the computer systems are daisy-chained together in a circle. In use of special devices known as routers. Internet Protocol such a con?guration, data is transmitted from node to node (EP) is an example of a network layer protocol which is part (computer to computer). The data is passed from computer of the TCP/IP protocol suite. to computer until the correct destination is reached. While Layer 2, the data link layer, is responsible for transfer of this avoids the problem of data collision, a break in the addressable units of information, frames, and error check connection disables the entire network. 65 ing. This layer synchroniZes transmission and handles A third type of topology is the star topology. In this frame-level error control and recovery so that information con?guration, all computer systems are routed to a central can be transmitted over the physical layer. Frame formatting US 6,516,352 B1 3 4 and cyclical redundancy checking (CRC), Which checks for carry information up to 100 m using Category 3 UTP Wiring errors in the Whole frame, are accomplished in this layer. It or better. UTP Wiring comes in grades 1—7. Category 3 also provides the physical layer addressing for transmitted Wiring supports transmission rates of up to 16 Mbps. Cat frame. Serial Line IP (SLIP) and Point-to-Point Protocol egory 5 cable, While more expensive, can support up to 100 (PPP) are examples of data link protocols. Finally, layer 1, Mbps. Category 7 cable is the highest, most expensive grade the physical layer, handles the transmission of binary data of UTP cable. over a communications netWork. This layer includes the physical Wiring (cabling), the devices that are used to In order to meet the demand for higher transmission connect a station’s netWork interface controller to the speeds, the standard (IEEE 802.3 u) Was established in 1995. This standard raised the Ethernet bus Wiring, the signaling involved to transmit/receive data, and 10 the ability to detect signaling errors on the netWork media. speeds from 10 Mbps to 100 Mbps With only minimal ISO 2110, IEEE 802, and IEEE 802.2 are examples of changes to the existing cable structure. The Fast standards. standard had the added advantage of being backWard compatible With the 10 Mbps Ethernet standard, alloWing For a bus or star topology, a transmission protocol is users to migrate to the neW standard Without abandoning needed for devices operating on the bus to deal With the 15 existing hardWare. Like the original Ethernet standard, Fast problem of data collision (tWo devices transmitting data over Ethernet includes several different transmission media. the bus at the same time). One such technique implemented 100Base-T is a generic name for 100 Mbps tWisted pair in the OSI data link layer is called carrier sense multiple CSMA/CD proposals. Speci?c proposals include 100Base access/collision detect (CSMA/CD). Under this technique, T4 and 100Base-TX. The 100BASE-T4 standard alloWs for hardWare residing in a netWork interface card (NIC) Within 20 support of 100 Mbps Ethernet over Category 3 cable, but at a given computer system senses the voltage change of the bus before attempting transmission of data. If no bus activity the expense of adding another pair of Wires (4 pair instead of the 2 pair used for 10BASE-T). For most users, this is an is detected, the data is transmitted over the bus to the appropriate destination. If bus activity is detected, hoWever, aWkWard scheme and therefore 100BASE-T4 has seen little popularity. 100Base-TX, on the other hand, is the most the NIC holds off the access for a predetermined amount of 25 popular solution for a 100 Mbps Ethernet, utiliZing tWo pairs time before re-trying the transmission. In such a manner, the of Category 5 UTP Wiring. integrity of the transmitted data is preserved. The CSMA/ CD technique is employed by a LAN protocol Even With 100 Mbps Ethernet for LAN s, neW and existing knoWn as Ethernet, Which Was developed by Xerox Corpo netWork applications are evolving to embrace high resolution graphics, video, and other rich media data types. ration in cooperation With DEC and Intel in 1976. Ethernet 30 uses a bus/ring topology and originally served as the basis Consequently, pressure is groWing throughout the netWork for IEEE 802.3, a standard Which speci?es the physical and for increased bandWidth. For example, many applications loWer softWare layers. Ethernet technology is by far the most demand ultra-high bandWidth netWorks to communicate 3D predominant netWorking protocol in use today, accounting visualiZations of complex objects ranging from molecules to aircraft. Magazines, brochures, and other complex, full for some 80% of all installed netWork connections by 35 year-end 1996. All popular operating systems and applica color publications prepared on desktop computers are trans tions are Ethernet-compatible, as are upper-layer protocol mitted directly to digital-input printing facilities. Many stacks such as TCP/IP (UNIX, WindoWs, WindoWs 95), IPX medical facilities transmit complex images over LANs, (Novell NetWare), NetBEUI (for LAN manager and Win enabling the sharing of expensive equipment and specialiZed medical expertise. Engineers are using electronic and doWs NT netWorks) and DECnet (for Digital Equipment 40 Corp. computers). Other LAN technologies Which are less mechanical design automation tools to Work interactively in popular than Ethernet include , Fast Ethernet, distributed development teams, sharing ?les Which hundreds Fiber Distributed Data Interface (FDDI), Asynchronous of gigabytes in siZes. Additionally, the explosion of Intranet Transfer Mode (ATM), and LocalTalk. Ethernet is the most technology is leading to a neW generation of multimedia client/server applications utiliZing bandWidth-intensive Widely utiliZed because of the balance it strikes betWeen 45 speed, cost and ease of installation. audio, video, and voice. In short, the accelerating groWth of LAN traf?c is pushing netWork administrators to look to The Ethernet standard is de?ned by the Institute for higher-speed netWork technologies to solve the bandWidth Electrical and Electronic Engineers (IEEE) as IEEE Stan crunch. dard 802.3. This standard de?nes rules for con?guring an The Gigabit Ethernet standard proposed in IEEE 802.32 Ethernet as Well as specifying hoW elements in an Ethernet 50 netWork interact With one another. By adhering to the IEEE offers a migration path for Ethernet users. The IEEE 80232 standard, netWork equipment and netWork protocols inter standard alloWs half- and full-duplex operation at speeds of operate efficiently. 1,000 Mbps, relying on the 802.3 Ethernet frame format and Original LAN s based on Ethernet technology supported a CSMA/CD access method With support for one repeater per collision domain. The Gigabit Ethernet standard is also data transfer rate of up to 10 Megabits per second (Mbps). 55 IEEE 802.3 speci?es several different types of transmission backWard-compatible With 10BaseT and 100BaseT Ethernet media con?gured to meet this transmission rate. 10Base-2 is technologies. a transmission medium Which is capable of carrying infor Much of the IEEE 80232 standard is devoted to de?ni mation via loW-cost coaxial cable over distances of up to 185 tions of physical layer standards (PHYs) for Gigabit Ether meters at 10 Mbps. This is also referred to as “thin Ethernet”. 60 net. This standard uses the Fibre Channel-based 8b/10b “Thick Ethernet” (10Base-5), conversely, is con?gured to coding at the serial line rate of 1.25 Gbps. Like other transmit up to distances of 500 m over 50-ohm coaxial cable netWork models, Gigabit Ethernet implements functionality at this same rate. A ?ber-optic standard, 10Base-FL, alloWs adhering to a physical layer standard. For Gigabit Ethernet up to 2,000 m of multimode duplex cable in a point-to-point communications, several physical layer standards are link. The most popular Wiring scheme at the 10 Mbps rate, 65 emerging. hoWever, is the 10Base-T standard, Which utiliZes tWisted TWo PHYs currently exist for providing Gigabit trans pair conductors (also called UTP-unshielded tWisted pair) to mission over ?ber-optic cabling. A 1000Base-SX is targeted