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Communication Networks

Communication Networks. Fifth Meeting. CSMA/CD Network. Carrier Sense Multiple Access With Collision Detection ( CSMA/CD ) Broadcast network Are you sure that you have collision? Slot time (in bits) Twice the propagation time between the two most distant stations

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Communication Networks

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  1. Communication Networks Fifth Meeting

  2. CSMA/CD Network • Carrier Sense Multiple Access With Collision Detection (CSMA/CD) • Broadcast network • Are you sure that you have collision? • Slot time (in bits) • Twice the propagation time between the two most distant stations • For example, IEEE 802.3 define the slot time as 512 bits. • Round-trip delay (in seconds) • Actual time • Also, know as contention time • How much is the round-trip delay in IEEE 802.3 • What is total transmission time?

  3. CSMA/CD Network • Carrier Sense Multiple Access With Collision Detection (CSMA/CD) • Broadcast network • Are you sure that you have collision? • Slot time (in bits) • Twice the propagation time between the two most distant stations • For example, IEEE 802.3 define the slot time as 512 bits. • Round-trip delay (in seconds) • Actual time • Also, know as contention time • How much is the round-trip delay in IEEE 802.3 • What is total transmission time? • Propagation time + delay

  4. After Collision • Stops the transmission • Calculates a delay period using binary exponential backoff algorithm • After first collision, either (k = 1) • Transmit the same frame or • Wait the slot time before attempting • After the second collision (k ≥ 2) • Wait for the following period • r * slot time • 1 ≤ r < 2k • r is selected at random

  5. Logical Link Control (LLC) Physical Signaling and Coding Medium Access Control (MAC) Media Specification IEEE 802.3 Sub-Layers • Provides flexibility to separate the media-independent functions in MAC • fiber-optic, • twisted pair IEEE OSI

  6. Fast Ethernet 100baseT (100 Mbps) FDDI = Fiber Distributed Data Interface 100baseX (FDDI) 100baseTX 100baseFX 100baseT4

  7. Gigabit Ethernet • 1995 a committee is formed • Allows half- and full-duplex operations at speeds of 1000 Mbit/s. • Uses the 802.3 frame format. • Uses the CSMA/CD access method. • Is compatible with earlier 10baseT and 100baseT technologies.

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