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Evolution of Ethernet LAN Technologies

Explore the history and advancements of Ethernet LAN technologies, from ALOHAnet to Fast Ethernet and beyond. Learn about key figures like Robert Metcalfe and the development of CSMA/CD. Dive into the comparison between Ethernet and Token Ring technologies. Discover how structured cabling has shaped modern networking.

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Evolution of Ethernet LAN Technologies

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  1. Ethernet LAN Technologies Ethernet LAN Technologies John A.Clark

  2. Agenda • Early History • Ethernet Vs Token Ring • Structured Cabling • Fast Ethernet • Gigabit Ethernet • GigE Vs ATM

  3. Early History • ALOHAnet - Norman Abrahamson, University of Hawaii • First packet radio network, circa 1970 • Several island transmitters communicated reliably to a central station • Had to deal with contention on the radio channel • Multiple stations attempting to transmit at once i.e. “a collision” • Packet transmissions repeated where collisions occurred • Remains in use today for "many to one" telecommunication applications e.g. GSM digital cellular standards … became the basis for Ethernet • Name coined 1972 - Luminiferous “Ether” • … Was though to be the passive medium, through which electromagnetic • waves could propagate, like water ripples, before the work of 20th • century physics

  4. Early History Robert Metcalfe - Inventor of Ethernet Also famous for founding a network/palm-top vendor! • Bob Metcalfe's Harvard PhD Thesis outlines idea for Ethernet • Experimental version at Xerox PARC - Paulo Alto Research Centre in 1972, focussed on coaxial cable shared transmission medium • Metcalfe, Boggs et al patent 1975 • DEC, Intel & Xerox - Ethernet Version 1.0 (1980) & 2.0 (1982) • IEEE 802.3 standard 1983

  5. Experimental Version 1.0 Data Rate 2.94 Mbps 10 Mbps Max Network Span 1 Km 2.5 Km Max Segment Length 1 Km 500 m Encoding Type Manchester Manchester Coax Cable Impedance 75 ohms 50 ohms Signalling Levels 0 to +3 volts 0 to -2 volts Preamble Length 1 bit 64 bits CRC Length 16 bits 32 bits Address Length 8 bits 48 bits Early History Experimental Ethernet - “Ironing out the bugs”! Changes in the Version 1.0 specification and were based upon the experiences with the 1st generation Ethernet First generation successfully proved concept … ran between two computers called Michelson and Morley, who proved “Ether” did not exist!

  6. Early History CSMA/CD - Carrier Sense Multiple Access/ Collision Detect • Carrier sensing & collision detection added to ALOHAnet scheme • Accumulation of -0.9 volt D.C. “carrier” voltage on coax • All collisions must be detected within propagation time of min size packet, 64 bytes (512 bits) = 51.2 usec at 10 Mbps … the Slot Time • Minimum inter-packet gap of 9.6 usec • 32 bit jam - collision consensus enforcement … to flood entire segment

  7. Early History Truncated Binary Exponential Back-off Algorithm Random retransmission delay before retrying after collision • A maximum of 16 retries are allowed • Delay on the nth attempt is a random number of slot times (51.2 usec) between 0 and 2n • Holds until the 11th retry (n=10), when the random delay is truncated to a value between 0 and 210 (1024) slot times • Fairly resolves contention amongst up to 1024 stations • 32 Bit CRC (Cyclic Redundancy Check) Error detection • G(x)=x32+x26+x23+x22+ x16+x12+x11+x10+ x8+x7+x5+x4+ x2 +x+1 • The binary number from the Destination,Source, Length(Type) and Data fields is divided by the result of cycling the last CRC through the polynomial G(x) • The remainder is placed in the CRC field, following the data. • During checking a recalculated CRC is XOR’d to check for a 0 remainder

  8. Ethernet Vs Token Ring • IEEE 802.5 Token Ring • Signals travel around the network from one station to the next, the cabling forming a logical ring • Networks originally operated at 4Mbps, increasing to 16Mbps • Access method on token ring networks is by token passing • Ensures only one station can transmit at a time

  9. Ethernet Vs Token Ring IEEE 802.3 Ethernet • 10 Mbps • CSMA/CD - statistical access • Approx 40% bandwidth efficiency • 1518 Max frame size • No inherent resilience at Physical level • Cost effective to deploy • Rapid advances in technology IEEE 802.5 Token Ring • 4/16 Mbps • Token passing - deterministic access • Up to 90% efficiency - little drop in response time • 15K+ MTU size • Self-healing beaconing process • Higher equipment costs • Slower development of standards & products

  10. Ethernet Vs Token Ring Market Trends do not always follow technoloy (VHS Vs Betamax!) • Industry analysis has shown that Ethernet continued to win the battle of the desktop technologies • Token Ring really only significant in vertical markets

  11. Structured Cabling • Ethernet over twisted pair “telephone cable” !! • Thicknet 10Base5, Thinnet 10base2, optic fibre 10BaseF • AT&T Systimax PDS (Premisis Distribution System) • Flood wiring of new buildings, grid pattern outlets per sq metre • Ronald Schmidt, technical director of SynOptics, creator of the Ethernet 10baseT standard • 10 megabits of baseband data over twisted pair Network Type Max Nodes Per Segment Max Distance Per Segment 10BASE5 100 500 m 10BASE2 30 185 m 10BASE-FL 2 2000 m 10BASE-T 2 100 m

  12. Fast Ethernet Same Ethernet but 10 times faster !! IEEE802.3u 100BaseT Standard approved in 1995 Employs original Ethernet CSMA/CD access method 100BaseT supports 3 physical layers: 100BaseTx: two pair system for Category 5 cabling 100BaseT4: four pair system for Category 3, 4 and 5 cable 100BaseFx: A two strand optic fibre

  13. Gigabit Ethernet 1000 Mbps Ethernet !! • 1996 Gigabit Ethernet developed IEEE 802.3z approved 1997 Leonard Kleinrock of UCLA helped define the mathematical limits of Ethernet, and for naming CSMA/CD).

  14. Gigabit Ethernet Standards Modifications • CSMA/CD method enhanced to maintain 200m collision diameters • Carrier time and Ethernet Slot Time extended from 64 bytes (512 bits) to 512 bytes (4096 bits) = 4.096 usec • Without this change, minimum sized frames could be transmitted before CSMA/CD could detect a collision • Packets smaller than 512 bytes (min still 64 bytes) have a carrier extension to 512 bytes • Adversely affects small packet performance - new facility in CSMA/CD called packet bursting to allow switches/server to send multiple small packets • Switches operating in full-duplex mode do not need carrier/slot time extension or packet bursting • Differential Mode Delay (DMD) problems with laser launch on 62.5 micron optic fibre

  15. GigE Vs ATM Network Speed/Distance Gigabit-Ethernet • 1000BaseCX: 25m • 1000BaseSX: 500m on 50 micron MM fibre, 160m on 62.5 micron (DMD) • 1000BaseLX: 550m all MM fibre , 3km SM fibre • 1Gbps limit • Network Diameter Restrictions when Shared ATM • 25Mbps • 155Mbps - OC3c • 622Mbps - OC12c800m MM/15km SM • 2.4Gbps - OC48c … no theoretical limit • No Network Diameter Restrictions

  16. GigE Vs ATM Network Resilience Gigabit-Ethernet • Spanning Tree Protocol blocks parallel links - stability issues? • No standards based load-sharing - Mostly proprietary • Use of OSPF / RIP with Layer 3 switching ATM • Build-in Redundancy • Parallel Load-sharing links for resilience & aggregate bandwidth • Full Meshed Topologies

  17. GigE Vs ATM Standards Required Gigabit-Ethernet • 802.3z (1000BaseLX/SX/CX) • 802.3ab (1000BaseTX) • 802.3x (Flow Control), Standard since 3/97 • 802.1P (Prioritisation) • 802.1Q (Vlan Queuing) • RSVP (Resource reSerVation Protocol), RFC 2205 ATM • LANE 1.0 • IISP (PNNI Ph 0) • PNNI • LANE 2.0 • MPOA 1.0 • NHRP

  18. GigE Vs ATM Routing/Layer3 Switching Gigabit-Ethernet • Routing via high 100/1000 Mbps links • VLAN trunks with IEEE 802.1Q coming • Layer 3 hardware routing switches with n Mbps throughout/ n usec latency ATM • Routing via high 100 Mbps links (1000Mbps to follow) • VLAN trunks with ATM VNR proven • Layer 3 switching via ATM Forum MPOA (Nortel/Bay) rolling out during Q199

  19. Conclusions Ethernet has evolved at a very rapid rate, 10 Mbps … 100 Mbps … 1000Mbps - this is likely to continue Ethernet - Here to Stay !

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