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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 2
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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 2 Mbit/s each !!! (C) Herbert Haas 2005/03/11 3 The initial idea of Ethernet was completely different than what is used today under the term "Ethernet". The original new concept of Ethernet was the use of a shared media and an Aloha based access al
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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 4 Later, Ethernet devices supporting structured cabling were created in order to reuse the voice-grade twisted-pair cables already installed in buildings. 10BaseT had been specified to support Cat3 cables (voice grade) or better, for example Cat4 (and today Cat5, Cat
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History: Bridges Store and forwarding according destination MAC address Separated collision domains Improved network performance Still one broadcast domain Three collision domains in this example ! (C) Herbert Haas 2005/03/11 5 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
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History: Switches Switch = Multiport Bridges with HW acceleration Full duplex Collision-free Ethernet No CSMA/CD necessary anymore Different data rates at the same time supported Autonegotiation VLAN splits LAN into several broadcast domains Collision-free 1000 Mbit/s plug & play scalable Ethernet ! 100 Mbit/s 100 Mbit/s 10 Mbit/s (C) Herbert Haas 2005/03/11 6 Several vendors built advanced bridges, which are partly or fully implemented in hardware. The introduced latency could
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Today No collisions no distance limitations ! 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 2005/03/11 7 Today, Gigabit and even 10 Gigabit Ethernet is available. Only twisted pair and more and more
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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 8 Remember: Hubs simulate a half-duplex coaxial cable inside, hence limiting the total network diameter. For Gigabit Ethernet this limitation would be about 25 meters, which is rather impracticable for professional usage. Although some
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MAC Control Frames Additional functionality easily integrated Currently only Pause-Frame supported Always 64 bytes 8 bytes 6 6 2 2 44 4 preamble DA SA 8808h MAC-ctrl opcode MAC-ctrl parameters FCS 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 9 Different data rates betwee
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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 2005/03/11 10 Several Ethernet operating modes had been defined, which are incompatible to
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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 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. Thus, each FLP sequence consists of a 16 bit
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100 Mbit Ethernet Overview IEEE 802.3u IEEE 802.12 Signaling Schemes Demand Priority Fast Ethernet Fast Ethernet 100VG-AnyLAN 100BaseX 100Base4T+ Signaling Signaling 100BaseT4 100BaseFX 100BaseTX (half duplex) HP and AT&T invention for real time applications "100BaseT" (C) Herbert Haas 2005/03/11 12 The diagram above gives an overview of 100 Mbit/s Ethernet technologies, which are differentiated into IEEE 802.3u and IEEE 802.12 standards. The IEEE 802.3u defines the widely used Fast Ethernet
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4B/5B Coding MII 16 code 0 0 0 1 groups 4 x 25 Mbit/s PCS 32 code 4B/5B Encoder/Decoder groups 0 1 0 0 1 PMA 125 MBaud (C) Herbert Haas 2005/03/11 13 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. This is done by a fast table lookup. Balancing the code has many advantages: better bandwidth utilization, better laser
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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 LWL SWL UTP Balanced Fiber Optic Fiber Optic Cat 5e Copper IEEE 802.3ab IEEE 802.3z physical layer physical layer (C) Herbert Haas 2005/03/11 14 Gigabit Ethernet has been defined in March 1996 by the working group IEEE 802.3z. The GMII represents a abstract interface between the common Etherne
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GE Signaling IEEE 802.3 IEEE 802.3z ANSI X3T11 Ethernet Gigabit Ethernet Fibre Channel FC-4 802.2 LLC IEEE 802.2 LLC upper layer mapping CSMA/CD FC-3 802.3 CSMA/CD or full duplex MAC common services Reconciliation Sublayer FC-2 802.3 PHY signalling PCS FC-1 encoder/decoder PHY PMA FC-0 interface and media PMD (C) Herbert Haas 2005/03/11 15 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 Chan
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GE 8B/10B Coding GMII Only used 1 1 1 1 1 1 1 1 256 code groups by 1000BaseX 8 x 125 Mbit/s PCS 1024 code groups 8B/10B Encoder/Decoder 125 million code groups per second 1 1 1 1 1 1 1 1 1 1 PMA 1250 Mbaud (C) Herbert Haas 2005/03/11 16 8B10B block coding is very similar to 4B5B block coding but allows fully balanced 10-bit codewords. Actually, there are not enough balanced 10-bit codewords available. Note that there are 256 8-bit codewords which need to be mapped on 1024 10-bit code
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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 17 Gigabit Ethernet can be transmitted over various types of fiber. Currently (at least) two types are specified, short and long wave transmissions, using 850 nm and 1300
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1000BaseT Defined by 802.3ab task force UTP 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 Cat. 5 links, max 100 m; all 4pairs, cable must conform to the requirements of ANSI/TIA/EIA-568-A Only 1 CSMA/CD repeater allowed in a collision domain (C) Herbert Haas 2005/03/11 18 It is very difficu
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Several Physical Media Supported Logical Link Control LLC Data Link Layer MAC Control (optional) Media Access Control MAC PLS Reconciliation Reconciliation Reconciliation MII MII GMII AUI PLS PCS PCS PHY AUI PMA PMA PMA (MAU) PMA PMD PMD MDI MDI MDI MDI Medium Medium Medium Medium 1-10 Mbit/s 10 Mbit/s 100 Mbit/s 1000 Mbit/s AUI Attachment Unit Interface, PLS Physical Layer Signaling, MDI Medium Dependent Interface PCS Physical Coding Sublayer, MII Media Independent Interface, GMII Gigabit Me
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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 20 10 GE only supports optical links. Note that GE is actually a synchronous protocol! There is no statistical multiplexing done at the physical layer anymore, because optical switching at that bit
