1. Ethernet The most popular LAN technology Open Standard Open and wide market

2. Ethernet 1970: Xerox in PARC, Robert M. Metcalfe, David Boggs, Charles Thacker, Butler Lampson Experimental Ethernet, 3Mbps 1979: Formal specifications DIX (DEC- Intel-Xerox). 10Mbps 1985: “IEEE 802.3 CSMA/CD” is published It has included new technologies periodically

4. Operation Stations connected to a SHARED MEDIUM No main controller Serial transmission to the medium, Manchester CSMA/CD Colissions

5. Shared Medium

6. BUS

7. Application Presentation Session Transport Network Datalink Physical Medium Physical Medium MAC LLC OSIIEEE 802 Upper Layers 802

8. Sublayers of IEEE 802 Logical Link Control –802.2 –SAPs to the upper layer –Assembly/Reassembly of frames –Addresses and fields for error detection Medium Access Control –802.3, 802.4, 802.5, 802.11,...... –Arbitrar el acceso al medio físico –Varias MACs para una sola LLC

9. Transmission in the BUS

10. Colission

11. Ethernet 10 Mbps Medium Access Control (MAC) Ethernet 10Base5 Thick coaxial 10Base5 Thick coaxial 10Base2 Thin Coaxial 10Base2 Thin Coaxial 10BaseT Twisted Pair 10BaseT Twisted Pair 10BaseF Fiber Optic 10BaseF Fiber Optic 10Broad36 Coaxial 10Broad36 Coaxial

13. 10Base5

16. 10Base2

18. 10BaseT

21. Switches Filter frames –With MAC destination address –damaged (CRC) –incomplet Self learning of addresses/port –Based on source MAC address Switching made by hardware Store-and-forward y cut-through

22. HUB

23. SWITCH

24. CSMA/CD Station ready for transmission Station ready for transmission Transmit listening Transmit listening End of transmission End of transmission Sense the channel Sense the channel Stop transmission and Start jam signal Stop transmission and Start jam signal Wait a random time (BEB)‏ Wait a random time (BEB)‏ Busy Free Collision

25. MTU Maximum Transfer Unit Big frames are not good for multiplexing –Big delays in “conversations” –More collisions

26. Importance of 2t p tptp ~ t p ~ 2t p L min (t) = 2t p