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HP 180 Degree Turn Product Review

The ethernet evolution.
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The Ethernet Evolution
The 180 Degree Turn
(C) Herbert Haas
2005/03/11
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  • Page 1

    The Ethernet Evolution The 180 Degree Turn (C) Herbert Haas 2005/03/11...

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    “Use common sense in routing cable. Avoid wrapping coax around sources of strong electric or magnetic fields. Do not wrap the cable around flourescent light ballasts or cyclotrons, for example.” Ethernet Headstart Product, Information and Installation Guide, Bell Technologies, pg. 11...

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    History: Initial Idea Shared media CSMA/CD as access algorithm COAX Cables Half duplex communication Low latency No networking nodes (except repeaters) One collision domain and also one broadcast domain 10 Mbit/s shared by 5 hosts Mbit/s each !!! (C) Herbert Haas 2005/03/11 The initial idea of Ethernet was completely different than what is used today under the term "Ethernet".

  • Page 4

    History: Multiport Repeaters Demand for structured cabling (voice-grade twisted-pair) 10BaseT (Cat3, Cat4, ...) Multiport repeater ("Hub") created Still one collision domain ("CSMA/CD in a box") (C) Herbert Haas 2005/03/11 Later, Ethernet devices supporting structured cabling were created in order to reuse the voice-grade twisted-pair cables already installed in buildings.

  • Page 5

    History: Bridges Store and forwarding according destination MAC address Separated collision domains Improved network performance Still one broadcast domain (C) Herbert Haas 2005/03/11 Bridges were invented for performance reasons. It seemed to be impractical that each additional station reduces the average per-station bandwidth by 1/n. On the other hand the benefit of sharing a medium for communication should be still maintained (which was expressed by Metcalfe's law).

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    History: Switches Switch = Multiport Bridges with HW acceleration Full duplex Collision-free Ethernet necessary anymore Different data rates Autonegotiation VLAN splits LAN into several broadcast domains 1000 Mbit/s 100 Mbit/s 10 Mbit/s (C) Herbert Haas 2005/03/11 Several vendors built advanced bridges, which are partly or fully implemented in hardware.

  • Page 7

    Today No collisions Gigabit Ethernet becomes WAN technology ! Over 100 km link span already Combine several links to "Etherchannels" Acts as single link from the spanning-tree view • Cisco: Port Aggregation Protocol (PAgP) • IEEE 802.1ad: Link Aggregation Control Protocol (LACP) 1 Gbit/s or even 10 Gbit/s long reach connection !!! (C) Herbert Haas...

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    What About Gigabit Hubs? Would limit network diameter to 20- 25 meters (Gigabit Ethernet) Solutions Frame Bursting Carrier Extension No GE-Hubs available on the market today forget it! No CSMA/CD defined for 10GE (!) (C) Herbert Haas 2005/03/11 Remember: Hubs simulate a half-duplex coaxial cable inside, hence limiting the total network diameter.

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    MAC Control Frames Additional functionality easily integrated Currently only 8 bytes preamble 8808h MAC-ctrl opcode ... Defines function of control frame MAC-ctrl parameters ... control parameter data (always filled up to 44 bytes) (C) Herbert Haas 2005/03/11 Different data rates between switches (and different performance levels) often lead to congestion conditions, full buffers, and frame drops.

  • Page 10: Auto Negotiation

    Auto Negotiation Enables each two Ethernet devices to exchange information about their capabilities Signal rate, CSMA/CD, half- or full-duplex Using Link-Integrity-Test-Pulse-Sequence Normal-Link-Pulse (NLP) technique is used in 10BaseT to check the link state (green LED) 10 Mbit/s LAN devices send every 16.8 ms a 100ns lasting NLP, no signal on the wire means disconnected (C) Herbert Haas...

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    Fast Link Pulses Modern Ethernet NICs send bursts of Fast-Link-Pulses (FLP) consisting of 17-33 NLPs for Autonegotiation signalling Each representing a 16 bit word GE sends several "pages" (C) Herbert Haas 2005/03/11 A series of FLPs constitute an autonegotiation frame. The whole frame consists of 33 timeslots, where each odd numbered timeslot consists of a real NLP and each even timeslot is either a NLP or empty, representing 1 or 0.

  • Page 12

    The 100VG-AnyLAN technology had been created by HP and AT&T in 1992 to support deterministic medium access for realtime applications. This technology was standardized by the IEEE 802.12 working group. The access method is called "demand priority".

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    4B/5B Coding 4 x 25 Mbit/s 125 MBaud (C) Herbert Haas 2005/03/11 The diagram above shows the basic principle of the 4B5B block coding principle, which is used by 802.3u and also by FDDI. The basic idea is to transform any arbitrary 4 bit word into a (relatively) balanced 5 bit word.

  • Page 14: Gigabit Ethernet

    Gigabit Ethernet Media Access Control (MAC) Gigabit Media Independent Interface (GMII) 1000Base-X 1000Base-T 8B/10B encoder/decoder encoder/decoder 1000Base-CX 1000Base-LX 1000Base-SX 1000Base-T Shielded Balanced Fiber Optic Fiber Optic Cat 5e Copper IEEE 802.3ab IEEE 802.3z physical layer physical layer (C) Herbert Haas 2005/03/11 Gigabit Ethernet has been defined in March 1996 by the working group IEEE 802.3z.

  • Page 15

    GE Signaling IEEE 802.3 Ethernet 802.2 LLC 802.3 CSMA/CD or full duplex MAC Reconciliation Sublayer 802.3 PHY (C) Herbert Haas 2005/03/11 Gigabit Ethernet layers have been defined by adaptation of the LLC and MAC layers of classical Ethernet and the physical layers of the ANSI Fiber Channel technology.

  • Page 16

    GE 8B/10B Coding GMII Only used 256 code groups 1000BaseX 8 x 125 Mbit/s 1024 code groups 8B/10B Encoder/Decoder 125 million code groups per second 1250 Mbaud (C) Herbert Haas 2005/03/11 8B10B block coding is very similar to 4B5B block coding but allows fully balanced 10-bit codewords.

  • Page 17

    1000BaseX Two different wavelengths supported Full duplex only 1000Base-SX: short wave, 850 nm MMF 1000Base-LX: long wave, 1300 nm MMF or SMF 1000Base-CX: Twinax Cable (high quality 150 Ohm balanced shielded copper cable) About 25 m distance limit, DB-9 or the newer HSSDC connector (C) Herbert Haas 2005/03/11...

  • Page 18

    1000BaseT Defined by 802.3ab task force Uses all 4 line pairs simultaneously for duplex transmission! (echo cancellation) 5 level PAM coding • 4 levels encode 2 bits + extra level used for Forward Error Correction (FEC) Signal rate: 4 x 125 Mbaud = 4 x 250Mbit/s data rate •...

  • Page 19

    Several Physical Media Supported Logical Link Control LLC MAC Control (optional) Media Access Control MAC Reconciliation PMA (MAU) Medium Medium 1-10 Mbit/s 10 Mbit/s AUI Attachment Unit Interface, PLS PCS Physical Coding Sublayer, MII Interface, PMA Physical Medium Attachment, MAU Medium Attachment Unit, PMD Physical Medium Dependent (C) Herbert Haas 2005/03/11...

  • Page 20

    10 Gigabit Ethernet / IEEE 802.3ae Only optical support 850nm (MM) / 1310nm /1550 nm (SM only) No copper PHY anymore ! Different implementations at the moment – standardization not finished! 8B/10B (IBM), SONET/SDH support, … XAUI ("Zowie") instead of GMII (C) Herbert Haas 2005/03/11 10 GE only supports optical links.

  • Page 21

    Note GE and 10GE use synchronous physical sublayer !!! Recommendation: Don't use GE over copper wires Radiation/EMI Grounding problems High BER Thick cable bundles (especially Cat-7) (C) Herbert Haas 2005/03/11 Both GE and 10GE are synchronous physical technologies on fiber. It not recommended to use GE over copper wires anymore although 802.3ab would specify it.

  • Page 22

    Summary Ethernet evolved in the opposite direction: Collision free WAN qualified Switched Several coding styles architecture Plug & play through autonegotiation Much simpler than ATM but no BISDN solution – might change! (C) Herbert Haas 2005/03/11 Complex PHY...

  • Page 23

    Quizz Why tends high-speed Ethernet to synchronous PHY? Can I attach a 100 Mbit/s port to a 1000 Mbit/s port via fiber? What is the idea of Etherchannels? (Maximum bit rate, difference to multiple parallel links) (C) Herbert Haas 2005/03/11...

  • Page 24

    Hints Q1: On fiber its difficult to deal with asynchronous transmission, photons cannot be buffered easily, store and forward problems Q2: No, autonegotiation on fiber does not care for data rates Q3: "normal" parallel links would be disabled by STP, Etherchannel supports up to 8 links (C) Herbert Haas 2005/03/11...

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