M
`TIP
`
`MACMILLAN
`TECHNICAL
`
`MACMILLAN NETWORK
`
`ARCHITECTURE AND
`
`DEVELOPMENT SERIES
`
`SWITCHED, FAST,
`AND GIGABIT
`ETHERNET THIRD EDITION
`
`Understanding, Building, and Managing
`
`High-Performance Ethernet Networks
`
`1
`
`Comcast, Ex. 1228
`
`

`

`

`

`

`

`:>r
`
`JtOr
`,tt
`
`rdinator
`
`oordinator
`
`d
`
`About the Authors
`Robert Breyer joined the networking industry in 1990, when he joined Intel in
`Folsom, California, as a product marketing engineer. His work there involved
`the sales and marketing of Ethernet 10BASE-T transceiver and controller chips.
`One of Robert's projects was the LAN on Motherboard program, which inte(cid:173)
`grated Ethernet directly into PCs.
`
`In 1993, Robert moved to Intel's network adapter group in Portland, Oregon, to
`develop the concept of value-added software for Intel's new line of network
`adapters. Subsequently, Robert was part of the team that launched the first
`10/100 PCI adapter, as well as the first 10/ 100 intelligent server adapter.
`
`Robert moved back to Johannesburg, South Africa, in 1995, where he became
`Intel's South African representative. During this time, Robert received the Intel
`Achievement Award, Intel's highest award. Robert was part of a team that set
`up an International Telecommunications Union (ITU) video-conferencing
`telemedicine demonstration featuring Dr. Andrew Grove, president and CEO of
`Intel, and Nelson Mandela, president of South Africa. From 1996 to 1998, Robert
`established and subsequently managed the official Intel sales subsidiary in
`South Africa. Robert is currently on a one-year leave-of-absence from Intel.
`
`Robert has a bachelor's degree in electrical engineering from the University of
`the Witwatersrand in Johannesburg, South Africa. In addition, Robert holds a
`master's of science in electrical engineering and a master's of business adminis(cid:173)
`tration from the University of California at Davis. He has written a number of
`white papers and application notes on local area networking technologies.
`
`Sean Riley, currently the director of marketing for Intel's networking products
`in Europe, the Middle East, and Africa, began work in the networking industry
`in 1992. Beginning in Intel's Folsom, California, factory as a technical marketing
`engineer, Sean worked on several early versions of Ethernet silicon products. In
`1993, Sean moved to Portland, Oregon, to develop and champion a new technol(cid:173)
`ogy called Fast Ethernet.
`
`During the next four years, Sean was involved early on in the High-Speed
`Working Group of the Institute of Electrical and Electronic Engineers (IEEE).
`This resulted in Sean becoming a founding member of the Fast Ethernet Alliance
`and a signing member of the IEEE 802.3u subcommittee, which standardized
`lO0BASE-T Fast Ethernet.
`
`4
`
`

`

`

`

`vi
`
`ievelop(cid:173)
`:chnology,
`into the
`
`iring from
`nd appli-
`1 the
`
`About the Technical Reviewer
`This book's technical reviewer, Matt Birkner, contributed his considerable practi(cid:173)
`cal, hands-on expertise to the development process for Switched, Fast, and Gigabit
`Ethernet. As the book was being written, he reviewed all the material for techni(cid:173)
`cal content, organization, and flow. His feedback was critical to ensuring that
`Switched, Fast, and Gigabit Ethernet fits our readers' need for the highest quality
`technical information.
`
`Matthew H. Birkner has been working in the networking industry for seven
`years. He has been a network design engineer, network operations center engi(cid:173)
`neer, and technical support engineer. Formerly senior networking engineer in
`MCI's outsourcing unit, he was responsible for the resolution of complex cus(cid:173)
`tomer networking issues. He is currently employed as a network consulting
`engineer at Cisco Systems, where he works on enterprise network designs and
`performance/analysis. Matt holds a bachelor's of science from Tufts University,
`where he majored in electrical engineering, and he is a Cisco Certified
`Internetwork Expert (CCIE).
`
`6
`
`

`

`

`

`Numerous individuals have helped make this new and improved third edition
`a reality. We would like to thank John Chambers, Doug Wills, and Maureen
`Kasper from Cisco Systems for contributing the Foreword to this book. We are
`also grateful to Kevin Tolly and Charlie Bruno from the Tolly Group for their
`interesting perspectives on Ethernet's future, covered in the Epilogue. Many
`thanks go to our technical reviewer, Matt Birkner, who taught us a thing or two
`about the IETF, bridging, and routing. We also want to thank Tony Beam from
`AMP, who provided some valuable input for Chapter 6, "Cabling and More on
`Physical Layers," and Sven Iversen who lent us his considerable knowledge of
`network management.
`
`We would also like to thank Kitty Jarrett and Amy Lewis from Macmillan
`Technical Publishing, who literally made the third edition happen. Finally, we
`would like to thank Brett Bartow at Macmillan for backing this project 100%
`(even though his authors resembled slugs at times) .
`
`We wish you luck with your new Switched, Fast, and Gigabit Ethernet networks.
`We hope you learn as much from reading this book as we did from writing it.
`Feel free to email us with comments, especially fourth edition suggestions!
`
`-Sean Riley (Sean. Riley@intel.com)
`RobertBreyer(Robert_A_Breyer@yahoo . com)
`October 1998
`
`n 1994, we
`jthernet
`red
`1bps ver(cid:173)
`~ether.
`r to put
`ation for
`
`:> a second
`·er a year
`· many
`.me
`that both
`1 into
`~ second
`to sub(cid:173)
`.ayer 3
`,witched
`Layer 3
`
`:atified
`y switch(cid:173)
`ndwidth
`~ third edi(cid:173)
`ents.
`ut a dozen
`
`ne as the
`:ause it
`to sepa(cid:173)
`rour
`h.ernet
`tg the way,
`ng, prior-
`~ the latest
`
`8
`
`

`

`

`

`xv
`xix
`
`1
`
`3
`
`37
`
`39
`83
`135
`161
`
`207
`209
`277
`317
`
`381
`
`383
`445
`469
`511
`545
`
`551
`
`553
`557
`567
`577
`
`Table of Contents
`Introduction
`
`Part I: The History of Ethernet
`
`CONTENTS
`ix I
`
`xix
`
`1
`
`3
`1 The History of Ethernet
`The Origins of Ethernet: The ALOHA Radio System (1968-1972) ................. 3
`Building the First Ethernet at Xerox PARC (1972-1 977) ... .. ..... ... ............. ... ..... 5
`DEC, Intel, and Xerox Standardize Ethernet (1979-1983) .. ................ ....... ....... 7
`3Com Productizes Ethernet (1980-1982) ......................... ... ..... ..... .. ....... ....... ...... 8
`Star LAN: A Great Idea, Except for Its Speed (1984-1987) ... .......................... 12
`The Demise of StarLAN ................................. ......... ..... .. ................... ....... 13
`The History of lOBASE-T and Structured Wiring (1986-1990) .......... .......... .14
`Fiber Ethernet and UTP Ethernet... ............... ......................................... . 14
`Structured Wiring: StarLAN and Token Ring ....................................... 14
`Syn Optics Communications Is Founded ..................................... .......... 15
`lOBASE-T Is Approved as an IEEE Standard .............. .......................... 15
`Novell NetWare: The Networked "Killer Application" ...................... 16
`The Demise of Token Ring ............................................ .. ... ...................... 17
`Ethernet Switching and Full-Duplex Emerge (1990-1994) .. .... ..... ....... .. ....... .18
`Full-Duplex Ethernet ................. ..................................... ........................... 19
`Fast Ethernet Emerges (1992-1995) ............................................................. ...... 19
`The IEEE 802.3 l00Mbps Standards Wars .................... ..................... .... 20
`Taking Ethernet into the Next Century: VLANs and Layer 3 Switching
`(1996-1998) .................................. ................................. .......... ..... .. ....... ....... .. ...... 21
`VLANs .. ..... ..... ...................... .. ....... ....................... ........ ........ .. ..... ....... ........ . 23
`Layer 3 Switching ................ ........ .............. ....... .. ......... ....... ......... .............. 23
`Industry Merger and Acquisition Trends (1993-1998) ..... .............................. 26
`3Com ....................................... ................ ..................... ... ............................. 27
`Bay Networks ................................................ ................................. ............ 27
`Cisco Systems ................ ....................... : ........................ ......................... .... 27
`Cabletron .............. ......... .................. ................................ ....... ..................... 28
`The Giants of the Networking Industry .................... ................ ............ 28
`Gigabit Ethernet (1995-1998) ......................... ......................... ....... .................. ... 30
`Summary .................. ......................... ................ ............... ......... ......... .......... ......... 36
`
`Part II: Repeating, Bridging, Switching, and Layer 3 Switching
`
`37
`
`39
`2 An Overview of High-Speed LAN Technologies
`A Historical and Somewhat-Biased Perspective .. ...... ........ ... ......................... .40
`Migration Issues ................................................. .. ...... .. ............. .......... ................. 41
`Connection Costs .............. ........ .... ........... .. ..................... .. .... ........... ......... . 42
`Performance Considerations ... ....... ................ ......................................... .42
`Quality of Service .. ... ....... ................. ........ ..... ........................................... .44
`Ease of Migration ....... ............. ................ .......... ......... ................................ 45
`
`10
`
`

`

`

`

`

`

`

`

`

`

`

`

`.. ....... 351
`.. ....... 364
`.. ..... .. 366
`...... ... 366
`·········367
`......... 372
`..... .... 379
`
`381
`
`383
`.... .... . 385
`.... ..... 385
`···· ·····386
`·········386
`........ . 387
`.... ..... 388
`......... 388
`... ..... .389
`.... ... .. 390
`.... ..... 391
`.... ... .. 392
`... ...... 394
`·········397
`.... .. ... 397
`.. .... ... 398
`........ .400
`.. .... ... 401
`... ... .. .402
`... ... .. . 403
`.. .... .. .404
`..... .... 404
`..... .. .. 406
`........ .408
`......... 410
`......... 412
`..... .... 413
`.... ..... 415
`......... 415
`.... ..... 417
`.... .... . 419
`······· .. 423
`......... 425
`......... 425
`
`CONTENTS
`xv I
`
`Deployment Step 5: Rou ters, Layer 3 Switching, and VLANs
`in the Backbone ........ ......... ................ .. .. .... ..... .......... .. .... ....... ................. .... ... .. .427
`Fast Ethernet Routers .... .... ....... ..... ... .......... ... ........... .... .. ...... .. .. ..... .. ....... .427
`Layer 3 Switches in the Backbone .......................................... ......... ... ... 429
`VLANs .. ..... ........... .............. .. ..... .. ........ ...... ... ... .... .... ................ ..... ... ... .. ... .. 435
`Deployment Step 6: Gigabit Backbone Switches .. ... ........ ............ .................. 438
`Connecting Multiple Workgroups ... ......... ................... .... ..... .... .. .... ...... 439
`Scaling Gigabit Ethernet Switches ........... ..... .. .. ... ........ .... ...... ........... .... 440
`Connecting Gigabit Ethernet Switches to
`Gigabit Ethernet Servers ... ....... ....... .. .... ............................................... 440
`Summary .. ... ... ... ..................... ..... ............. ............... .... ............ ... ..... ......... ........ ... 442
`
`445
`
`10 Deployment Examples
`Example 1: Deploying Switched and Fast Ethernet in a New
`Network ........ ........ .......... ...... ......... ........ .... .... ......... .............. ..... ..... .... ...... ...... .. 446
`The Backbone Solution: A lO0BASE-FX Switched Backbone ....... .. .. 447
`The Workgroup Solution: A Combination of Switched
`and Fast Ethernet ....... ......... ....... .......... ...... .......... .... ............ ........ ... ...... 449
`Cost Analysis ......... .... ............. .. ... .... ....... .. ... .................. .. ... .... .... ... .... ..... . .454
`Example 2: Adding Layer 3 Switching Capability to the Backbone ........ . .456
`Example 3: Deploying Switched and Fast Ethernet in a LAN
`with an Existing FDDI Backbone ... ...... .... .. .............. .... ....... .......................... 458
`Adding lO0BASE-T Workgroups to an FDDI Ring ... .... ..... ................ 459
`Extending an FDDI Ring with lO0BASE-FX ... ..... ....... .... .. ... ... ........ .. .. .460
`Example 4: Deploying a Gigabit Ethernet Switched Backbone .. .... ....... "' ... 461
`Example 5: Deploying a 10-Mbps Switch as a Switch of Hubs .. ............. ... 463
`Example 6: Deploying Fast Ethernet in a Branch Office .. ..... .... ....... .... ........ 465
`In the Real World, Every Network Is Different.. ....... .. ....... ....... .. ... ........ ... .. .. 467
`
`469
`11 Managing Switched, Fast, and Gigabit Ethernet Networks
`Network Management. .............. .. ..... .. : ...... ............. .... ......... ... .... .... ........ ..... ...... 470
`SNMP ......... ........ .............. ... ..... .... ............. ...... ... ............. .... ...... ...... .... .... .. .471
`RMON ................ .......... ...... ..... ........... .......... ... ................ ............. ....... .... .. 475
`Other Aspects of Network Management .... ....... ........ .......................... 487
`Desktop Management. .. ....... .................... ..... ........... ................... .. .... ... .... .. .. ..... . 490
`Asset and Applications Management ... ... ...... .............. .. ........... .. ......... . 491
`Server Monitor Services Management .......... ..... .... ............ ........ ... ...... 491
`Help Desk Services Management ........................................................ 492
`Business Management ....... ... ....... .. ................ .... ......... ........... ... .... ..... ... ........ ..... 492
`Chargeback .......... .................. ..................................................... .......... .... 492
`Cost Management ........ ......... ................................................ ............... .... 493
`Key Issues for Managing Switched Networks ................ .. ....... ..... .... .... ........ 493
`VLANs .. ...... ............ .... ... .... ... .. .................... .... ... ......................... ... .......... .. 494
`Managing Service Levels .... ........ ....... ......... ................ ......... ....... ........ .. . .500
`Managing Switches at Gigabit Speeds ............. ........ ......... ..... .... ........ . .503
`Planning for Future Needs ... ................ .............. .. ....... .......... .......... ..... . .505
`The Future of Managing Switched Networks ........................... ....... .. .508
`
`16
`
`

`

`

`

`P A R T H REPEATING, BRIDGING, SWITCHING/AND LAYER 3 SWITCHING
`
`
`
`10Mbps Ethernet MAC and PHY Standards
`Ethernet is strictly basedon a layered 051 model. As a result, you can easily ,
`combine the Ethernet MAC With different PHYnghis Section discusses the
`‘
`10Mbps Ethernet MAC standards, and the fourmajor basebandPI—IY
`specifications.
`_
`-
`,
`,
`,
`,
`it
`
`The Ethernet CSMA/CD MAC
`The Ethernet MAC technology is called carriér—sense multiple access with collisiok
`detection (CSMA/ CD). Figure32 illustratesthe CSMA/CD flow.
`I
`‘
`
`’
`Station ls ,
`ready to send _
`
`
`
`
`
`
`
`,' Walt seeming to
`backo'ff strategy,
`(6)
`
`
`
`
`
`Transmit data and
`, sense channel
`(4)
`
`
`
`Transmlt
`
`
`
`jam signal
`
`,
`, (5)
`
`
`
`
`
`FIG u a: 3.2 A flow diagram illustrating the CSMA/CD MAC.
`
`CSMA/CD is the shorthand version for about seven different steps that mak
`up’an Ethernet transmisSion. Notice the analogy to human speech among Vmul
`tiple individuals:
`
`1. A station wanting to transmit a frame of information has to ensure tha _
`no other nodes or stations are currently using the shared media, so the*
`'
`station listens to the channel first. (This is the carrier sense part, also ,
`'
`known as ”listen before talking”)
`
`
`
`
`18
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`18
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`

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`C H A P T E R 3
`
`
`ETHERNET, FAST ETHERNET, ANDGIGABIT ETHERNET STANDARDS
`
`IE9
`
`,«Ifs’che channel1s quiet for a certain minimum period of time, called the
`, nterframe gap (IFG), the station may initiate a transmission (“talk if
`
`
`If the channeIL'is buSy,it is monitored continuously until it becomes free
`' for the minimumIFGtime period At this point, transmission begins
`
`
`
`2——byte frame type/length field Figure 3.3 shows both frame types.
`
`ting at almost the same time This event would lead to a collision and
`
`destroy both data frames. Ethernet continuously monitors the channel
`
`during transmission to detect collisions (collision detection, or ”listen
`
`iwhile talking’’.)
`'
`L
`_ station detects a collision during transmission, that transmission
`
`mmediately stops. Ajamsignal15 sent to the channel to guarantee that
`
`llother stations detect the collision and reject any corrupted data frame
`L,they mayhave beenreceiving (also part of the collision detection,or ’one
`
`talker at a time’’).
`L
`After a waiting period (called a backoff) the stations that wishto transmit
`
`ttempt to make a new transmission A special random baCkoLff algorithm J
`
`(called binary exponential backoff, or BEB) determines a delay time that
`
`1edifferent stations will have to wait before attempting to send their
`dataagain Of course, another collision could occur after the first one,
`
`especially whenmany nodes aretrying to obtain access at the same time.
`
`fter 16 consecutive collisions fOr a given transmission attempt, the
`
`acket will be dropped. This can and does happen if the Ethernet channel
`roverutilized Thisis also part of the multiple access method.
`L
`
`
`
`
`etuses frames of data to transmit the actual information, also known as
`load fromLsource to destination Like most Other LANsin existence today,
`
`1 Let transmits a frame of variable length Thelength of the frame changes
`
`use thepayload or data field can vary.
`original Ethernet frame specified by Digital, Intel, and Xerox is known as
`
`DEC-Intel—Xerox Ethernet V2.0 frame, or just DIX or Ethernet II frame. The
`cial IEEE Ethernet frame subsequently replaced it; The only difference is in
`
`"The sequence returns to step’l.
`
`19
`
`19
`
`

`

`
`
`
`
`
`
`I
`
`_ REPEATING,’ BRIDGING, SWITCHING, AND LAYER 3 SWITCHING
`
`P A R T _l
`90l
`
`_
`
`,
`._ Bits
`_
`_
`:Qontent
`.y
`generatedby 76543210
`
`r-L' L
`_
`802.3
`l
`
`,
`
`'
`
`
`
`StartFrameDelimiter
`Destination Address
`‘Source Address
`
`-
`
`
`
`
`
`
`,
`
`‘
`
`"
`,_’.
`
`'
`
`,
`I
`,
`802.2 LLC
`generated
`subframe
`
`3
`,
`_
`,, Bits
`Length
`L 76543210
`
`
`7 Bytes
`Preamble
`"
`'
`1 Byte
`StartFrameDelimiter
`
`
`6 Bytes
`Destination Address
`
`6 Bytes
`Source'Address
`,
`,
`
`g 1Byte m_
`1 Byte
`‘
`1Byte
`1or2Bytes
`'
`Variable
`
`
`
`
`
`(PDU)
`
`I
`
`I
`
`D1agzggagsfi
`
`Variable
`
`.4Byies
`
`Pad
`
`FrameCheckSequence
`IEEE 8022 Frame
`
`’
`
`-
`
`-
`
`
`
`FrameCheckSequence
`DIX Ethernet,“ Frame
`
`.
`
`(PDU) directly
`
`L
`
`L
`
`‘
`
`FLI GLU RE 3 .3 Theofficial IELEE Lundtlze alder DIX Ethernet IIframe differ in same
`respects.
`L
`L
`‘L
`L
`’
`L
`,
`_
`L
`
`1
`
`———|
`PLtL'L|(
`Novel! lPX
`‘0 00° 9-9" ‘
`fills the ),
`‘
`subframe
`
`,
`
`’,
`
`Let’s look at the individual fields that comprise the Ethernetframe:
`0 ' The preamble is Sent to allow the receiver to synchronize with the Linc
`
`ing_transtni$sion andlocate the start of the frame. The preamble is-‘a
`sequence of 01010101..., 7_bytes long.
`'
`p
`L
`"
`
`- The Start of frame delimiter (SFD),indicates that the MAC frame is ‘ab
`. to commence. The SFD octet or byte'is specified as 10101011.,
`L LIL, The source’address denotes the sender. Each node has aunique ad
`
`L
`L The first‘three bytes of the’a’dd‘ress are called‘the b10ckLID orSOrganizae
`tionally unique identifier (OUI)L and identify the manufacturer of the
`
`equipment. The IEEE assigns them. Intel, for example, is identified-b
`OO—AA—OO (hex) address, 3Com uses the OO—ZO—AF address, and Cisco
`
`00—00-0C. The other three bytes are called the device ID and are assig
`by each manufacturenThese are always unique. Three bytes of devic
`_ allows for 16 million different and unique addresses: 2A24—1 or 16,_
`
`to be exact. Some of the major Ethernet vendors have shipped mor th
`
`16 million Ethernet MAC devices and have started using new OUIs.
`Some of the references given in Appendix C, “Useful Web Links,” she
`the complete list of vendor'OUIs.
`L
`L
`L
`L
`‘
`'
`‘L
`L- The destination address specifies where the frameLwill be sent. -y
`
`
`
`
`
`
`
`L
`
`20
`
`/
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`20
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`

`

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`C H A- P T E R
`
`3
`
`ETHERNET, FAST ETHERNET, AND GIGABIT ETHERNET STANDARDS-
`
`...:.9
`
`
`
`The-protocol type is a field in the original DIX V2.0 frame type. It speci—,
`
`fied which kind'of Layer 3 protocolthe data contained. A hexadecimal
`
`:value of 08 00 indicatesaTCP/IP packet, for example,and 8137 indicates
`
`a Novell NetWare packet.
`
`
`“The newer IEEE frame differs from the Ethernet II or DIX fraIne type in
`onekey area. The IEEE frameis much mere popular thesedays and no
`
`longer uses the protocol typefield, where it has been replaced with the
`
`length field. This specifies the total length of the data that willbe trans—
`
`mitted, which can varyfrom 0 to 1500 bytes. If the contents of this field
`
`are 0 to 1500 bytes, you can be sure that it is the lengthwe are discussing.
`
`Ifthe contents of theitypelength/ type field are greaterthan 1500 bytes
`
`(for example, 8,137), we are talking about the 'olleXframe type.
`
`The data field can vary'from Oto 1500 bytes in length. The data field is
`
`L also known as theprotocol dataunit (PDU). We discuss the contents of
`
`-L the data field in more detail later.
`
`If the actual data15 less than a minimum length required,the MAC will
`
`I add a variable pad to maintain a minimum total frame size of 64 bytes If
`
`_‘ the data15 longer than the maximum frame allows, Layer3 willtypically
`
`split the packet into morethan one frame.
`,
`
`J-Finally, a frame check sequence (FCLS) ensures accuratetransmission. The
`cyclical redundancy check method (CRC) checks for invalid frames This
`value15 calculated from the rest of the packet’s dataand sent alongin the
`a , FCS frame. The receiving station performs the samecalculations and
`compares its results With the FCS transmitted With the packet If the
`results are different, the packet15 rejected.
`-
`-
`. The maximum total frame size is 1518 bytes. (The frameofficially starts
`with the source address.)
`
`
`
`
`
`There are a total of four different frame types. The DIX Ethernet 11 frame dis-
`Cussed previously, plus three different versions of the IEEE frame type. the
`
`Ethernet 802.3 frame (also known as Novell Raw LLC), the 802.2 frame, and the
`
`802.2 with SNAP frame. All look slightly different. Figure 3.4 shows the Con-
`
`tents of the 1500~byte data field for the four different frame types. Thefollow-
`
`ng list details the three different versions of the IEEE frame type:
`
`f
`
`0 The Novell Raw frame formatis used only by Novell’s NetWare operat-
`ing system, and uses the 802.3 frame shell type without adding an IEEE
`802.2 LLC header within the data field. In this case, NetWare adds its
`
`
`
`21
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`21
`
`

`

`PART
`
`W 921
`
`REPEATING, BRIDGING, SWITCHING, AND LAYER 3 SWITCHING
`
`.
`
`own IPX information. This type;of,frame is called “Novell RaW” because
`- it encapsulates the IPX data’in raW form without any 802.2 LLC infor
`. tion.:Because fthe frame‘doesn’t' use the IEEE 802.2 LLCinformation, this
`frame type is actually NoVell-proprietary and not, 802.3 compliant.
`‘
`
`
`
`
`~ ' For the802.2 fraInetype, the data field‘contains‘the 8022 LLC-embedd“
`information. The IEEE frame contains theprotocol type information
`
`'Within the LLC subframe. Three fields are located at the beginning of the
`data field. The DSAP field,a 1-byte SSAP field, and a 1-byte Control fiel
`
`The IEEE frame assigns Service Access Point numbers; among those cur:
`rently defined are E0 forNovell, F0 for NetBIOS 06 for TCP/IP and AA I
`
`”for the Subnetwork Access Protocol (SNAP)
`5
`,
`
`U V The802.2 With SNAPframeIs almost identical to the802.2 frame, except
`it supports more than 256 protocol types by adding a 5—byte Protocol
`Identification field. On any SNAP packet, both the DSAP and SSAP field
`
`_ are set to AA, and the Control field15 set to03 The 5~byte protocol field
`
`‘
`then follows.
`,
`
`, Table 3.2 lists allthe relevantEthernetMAC frame parametersMost 10Mbp
`
`Ethernet/ 802.3 MAC parameters are listedIn bit times. The Ethernet MAC1
`
`inherently scalable All the parameters can be measuredIn terms of the time
`taken to transmit 1 bit ‘of data’,’refe’Ired to as bit times. Note that the actual
`I
`” speed of Ethernet (10Mbps) is not mentioned'Inthe MAC specification at all
`This makes itvery easyto runEthernet at different speeds.
`
`TABLE 3.2 KEY 10MBPS ETHERNET MAC AND FRAME PARAMETERS, SPECIFIED IN BIT TIMES
`Parameter
`_ '
`_
`Value (Bit Times)
`Time
`512 bit times
`
`I
`
`MinIn‘t‘erFI‘ameGap’k ~
`AttemptLimit
`
`‘
`
`“
`
`'
`
`96 bit times (or 9.6 Ms)"
`‘16 (tries) '
`H
`
`I
`
`BackoffLimit
`Jamsize
`MaXFrameSjlze
`MinFr‘ameSize
`'Addr‘essSize
`
`I
`
`I
`
`‘
`
`I
`
`'
`
`I
`
`I
`:_ I
`'
`
`I
`
`'2
`I
`
`,y
`,_
`
`, A
`
`I
`
`'I
`
`,
`
`_
`
`'
`
`,
`
`_'
`
`I
`
`I
`
`’
`,
`‘ I,
`
`10 (exponent)
`32 bits
`'
`12144 bits (1518bytes)
`I 512 bits (64 bytes)
`I 48 bits
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`22
`
`
`
`
`
`
`
`
`
`22
`
`

`

`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`6 Bytes ,
`
`
`2 Bytes
`,
`, 0-1500 Bytes
`
`-_ a Bytes
`‘ Preamble
`'
`‘
`
`6 Byte;
`Destlnetion
`Address
`
`
`Type
`
`
`2 Bytes '
`
` DIX Type II Frame
`Always > 1500
`)
`8137 (NetWare
`
`
`IPX Header + Packet
`
`" Noyell RAW
`(also known as 802.3)
`’
`
`,
`
`-
`
`Length,
`2 Bytes
`‘ 0—1500 Bytes
`
`,
`
`'
`
`Proprietary
`Header
`
`Ipx‘ Packet
`
`, Ethernet802.2
`,
`
`‘
`
`N
`
`N,’ r,:‘c,»(am2e.
`
`a:
`
`o.
`
`%\at 311’U‘
`
`C 9“
`
`(DcUs“3GI
`
`
`
`ssAP’
`13),“; Comm
`E0
`ea
`
`IPX Packet
`
`SSAP Control
`1 Byte
`1 Byte
`AA
`
`2 Bytes
`
`§
`'
`IPX Packet ‘
`-
`’
`
`.
`
`F: G u R E 3 .4 The data field of the four different frame Ethernet types in use. '
`
`
`Novel!
`
`
`
` Ethemet 302.2 with SNAP
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`calculating the time to transmit 1 bit for 10Mbps Ethernet transmission
`becomes very easy:
`‘
`L
`,
`'
`
`1 bit
`10Mhz
`
`= 6.1th or‘ 1I0ns
`
`
`
`1:,_bit-time =
`
`, For 1Mbps Ethernet/StarLAN, the frame looks exactly the same. The only,
`thing that changes is the bit time. For StarLANLthe bit, time is 1 /1MHz = 1 us,
`or 1000ns. Fast Ethernet works exactly the same way: The frame is identical
`again, but the bit time is reduced to 1 /10, or 10ns.
`I
`
`th‘ernet PHYS
`This section looks at the different PHY implementations for 10Mbps Ethernet
`(see Figure 3.5). There are officially five ways to transmit 10Mbps Ethernet:
`
`
`
`
`
`
`23
`
`
`
`23
`
`

`

`
`
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`
`
`
`
`
`
`
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`
`
`
`
`
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`
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`
`
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`
`
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`
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`
`
`
`
`
`PART II
`
`”“741
`
`REPEATING, BRIDGING, SWITCHING, AND-LAYER 3 SWITCHING
`
`,' 10BASE5Is the original thick Ethernet coaxial cable standard, datinS
`to the early 1970s.
`'
`0”
`loBASEZ, also known as thin Ethernet,was added in the early 1980san
`uses a thinner coaxial cable.
`*
`
`
`y ' _ In 1990, Ethernet over unshielded tWisted=pair,‘l<noWn as 10BASE-T,w
`y'standardized.‘
`,
`_
`,
`
`
`
`
`
`,
`
`_
`
`
`
`
`
`
`
`‘y '
`
`IOBASE-F, although less well known, is very important because it util
`fiber cabling to carry Ethernet over extended distances. The physical
`ers mentioned so far all use baseband transmission methods, which
`, .meansthe entire frequency spectrum transmits the data
`
`,L 0 ' 10BROAD361s different from all the other Ethernet PHY standards In
`
`that it uses broadband transmission technology to transmit. This allo
`different channels to communicate simultaneously on the same cable;
`rlOBROAD36Is far less popularand no similar 100Mbps broadband P
`I exists, so we will not disCuss 10BROAD36In this book.
`<
`
`' Ethernet
`CSMA/CD :
`MAC
`‘
`
`
`
`
`_0BHOAD36
`1OBASEF
`1OBASIE~T
`l
`I
`Two strands
`I
`I
`Two pairs
`coax
`I Iof Cat 3 UTP
`MMF
`I
`I
`
`II
`
`_OBASE5
`509
`Thick Coax
`
`1OBASE2
`509
`Thin Coax
`
`f mun: 3.5 'ThedifferentEthernei/soza PHYS.
`
`,
`
`,
`’,
`1OBASE5:Thicknet
`
`10BASE5 is the original Ethernet 802.3 standard. 10BASE5 utilizes a thick,:_o
`_.
`yellow, coaxial cable that hasa physical diameter of 10mm. The cable hasto b ’
`terminated with a SOOhm/ 1W resistor. Up to 100 stationsper segment are
`allowed.
`'
`
`I
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`24
`
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`

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`

`C H A P T E R
`
`3
`
`ETHERNET, FAST ETHERNET, AND GIGABIT ETHERNET STANDARDS
`
`I117
`
`' TABLE 3.10 A SUMMARY or THE DIFFERENT GIGABIT ETHERNET PHYSICAL LAYER
`IMPLEMENTATIONS
`
`10“ a“ four
`: or receive, -
`s is some ' n
`
`.‘ PHY Parameter
`‘
`IEEE Standard
`
`'
`
`-
`. Number of
`. pairs required
`
`IOOOBASE-T
`802.3nbI
`
`IOOOBASE-SX
`
`Four pairs
`
`Two strands
`
` can still use a
`
`
`T uses the
`
`2, namely
`Cy as
`
`ise
`l<11
`'X/TZ-
`-,I but the co ‘
`n all four
`te of 125 I
`
`r
`
`Cable Category Category 5
`required
`or better
`
`50 or 62.5
`um MMF
`
`‘ Cable length
`
`: Encoding
`Connector
`F specified
`_, Proven
`
`100m
`
`220—550m
`
`4D-PAM5
`RJ—45
`
`8B/1013
`SC
`
`Not yet
`
`IOOOBASE-LX
`802.32
`(July 1993)
`Two strands
`
`50 or 625
`um MMF
`or 8-10um
`SMF
`
`5000111 (SMF)
`550m (MMF)2
`88/108
`SC
`
`IOOOBASE-CX
`
`Two pairs
`
`150-9
`Twinax
`
`25m
`
`EBB/108‘
`HSSC or DB-9
`
`3
`
`3
`
`Probably
`not3
`
`3
`
`3
`
`1
`
`33
`
`3
`
`3
`
`3
`
`Yes
`
`Full-duplex
`capable
`Broad product None.
`_ support
`shipping yet
`
`lires a highly
`:eiver Chip n;
`[e that will
`Intel 486
`
`.
`es’gne‘j to ana-
`
`.
`Pomt PTOd'
`
`1 layers.
`
`
`
`1 802 jab approval is expected in mid—1999. Products are expected around the same timeframe.
`2 Requires special DMD patch cord. See Chapter 6 for more details.
`3 By September 1998, not a single Gigabit Ethernet vendor was shipping CX-based product.
`
`. IEEE Auto-Negotiation Standard
`When lOOBASE-T was invented, it was no longer safe to assume that a typical
`Ethernet R145 connector would be carrying lOBASE-T. Instead, a UTP cable
`could carry one of seven different Ethernet signals: IOBASE-T, lOBASE-T full-
`duplex, 100BASE-TX, IOOBASE-TX full-duplex, 1008ASE-T4, IOOBASE-TZ, or
`IOOBASE-TZ full-duplexThe IEEE incorporated a very elegant scheme into the
`802.3u standard that has simplified your life as a LAN manager tremendously.
`The IEEE's auto-
`
`negotiation technology, originally developed by National Semiconductor and
`known as NWay, can tell what speed the other end of the wire can handle. The
`repeater, switch, or NIC will then automatically adjust its speed to the highest
`common denominator—the fastest speed that both can handle. This is how
`auto-negotiation works:
`
`0 Both devices need to contain the auto-negotiation logic. (All Fast Ethernet
`equipment shipping after mid—1996 includes this feature.)
`
`0 Auto-negotiation is an enhancement of the lOBASE-T link integrity sig-
`naling method and is backward compatible with link integrity.
`
`32
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`32
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