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Station A begins transmission at t =0

Station A begins transmission at t =0. A. Station A captures channel at t = t prop. A. CSMA Random Access Scheme. P-Persistent CSMA. sensing. Performance of non-persistent CSMA. S. 0.81. Non-Persistent CSMA. 0.01. 0.51. 0.14. 0.1. G. 1. Performance of 1-persistent CSMA. S.

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Station A begins transmission at t =0

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  1. Station A begins transmission at t=0 A Station A captures channel at t=tprop A CSMA Random Access Scheme

  2. P-Persistent CSMA sensing

  3. Performance of non-persistent CSMA S 0.81 Non-Persistent CSMA 0.01 0.51 0.14 0.1 G 1

  4. Performance of 1-persistent CSMA S 0.53 1-Persistent CSMA 0.01 0.45 0.16 0.1 G 1

  5. A begins to transmit at t=0 B A B begins to transmit at t= tprop- B detects collision at t= tprop B A A B A detects collision at t= 2 tprop- Reaction time in CSMA-CD It takes 2 tprop to find out if channel has been captured

  6. Probability of 1 successful transmission: frame contention frame Packet Transmission and Contention periods Pmax Psuccess is maximized at p=1/n: n

  7. Achievable Throughputs CSMA/CD 1-P CSMA Non-P CSMA max Slotted Aloha Aloha a

  8. Frame Transfer delay for Ethernet a = 0.01 a = 0.1 a = 0.2

  9. IEEE 802.3 MAC Frame 802.3 MAC Frame 2 or 6 1 2 or 6 2 4 7 Destination Address Source Address Information FCS Pad Preamble Length SD Synch Start frame 64 to 1518 bytes • Destination address is either single address • or group address (broadcast = 111...111) • Addresses are defined on local or universal basis • 246 possible global addresses 0 Single address Group address 1 0 Local address 1 Global address

  10. Ethernet frame (DIX Standard) Ethernet Frame 2 or 6 1 2 or 6 2 4 7 Destination Address Source Address Information FCS Pad Preamble Type SD Start frame Synch 64 to 1518 bytes

  11. SNAP frame for encapsulating Ethernet frames Type ORG 2 3 SNAP Header SNAP PDU Information LLC PDU AA AA 03 1 1 1 802.3 Frame MAC Header FCS

  12. Ethernet Cabling (a) transceivers (b)

  13.       Ethernet hub-and-switch topologies Single collision domain (a) High-Speed Backplane or Interconnection fabric (b)    

  14. Fast Ethernet Ethernet Switch Server 100 Mbps links Ethernet Switch 10 Mbps links

  15. 10 Base5 10Base2 10BaseT 10BaseF Medium Thick Coax Thin Coax Twisted Pair Optical Length 500m 200m 100m 2km Topology Bus Bus Star P2P IEEE 802.3 Medium Alternatives Fast Ethernet 100Base T4 100BaseT 100BaseF Medium Twisted Pair Cat.4 Twisted Pair Cat.5 Opt. Multimode UTP 4 Pairs UTP two pairs two strands Length 100m 100m 2km Topology Star Star Star

  16. Gigabit Ethernet 1000 BaseSX 1000BaseLX 1000BaseCX 100BaseT Medium Optical Fiber Optical Fiber Shielded Copper Twist.Pair multimode single mode cable cat.5 UTP 2 strands 2 strands Length 550m 5km 25m 100m Topology Star Star Star Star

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