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2004.3.30.

Join the make-up class on Thursday, April 15, from 2:30-4:00pm to cover the topics of encoding, framing, and error detection in Chapter 2. Submit HW#3 before class to Meeyoung. No late turn-ins allowed.

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2004.3.30.

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  1. 2004.3.30. • Make-up class for 2004.3.23. • 2:30-4:00 on Thu, 4/15 • HW#3 • Due 2:30pm on Thu, 4/8 • Turn in to Meeyoung before class • No late turn-ins • Chapter 2.1.~2.5.

  2. Problems to Consider When Connecting Node Directly • Encoding • Framing • Error Detection • Reliable Delivery • Media Access Control

  3. Clock-Based Framing • SONET • Used mostly for digital transmission over optical fiber on long haul links • Sender and receive clocks synchronized • Part of SDH (Synchronous Digital Hierarchy) • Basic rate of 51.84Mbps (STS-1) • OC-n: OC-3, -12, -48, OC-192 (STS-1 x n)

  4. Error Detection • Q: What is prob of having a 1-bit error? • Depends on BER of the medium • Goal of Error Detection • Maximize prob of detecting errors using a small # of redundant bits • Well-known algorithms: • Two-dimensional parity • Checksum • CRC

  5. Error Detection vs Correction • When to use error correction? • BER is high • cost of retransmission is very high

  6. Reliable Transmission • Stop-and-wait • acknowledgement, timeouts, 1-bit seq no. • Sliding window • sender: window size, last ack’d rcv’d, last frame sent • receiver: window size, largest acceptable frame, last frame rcv’d

  7. Next Class • Finish Chap. 2.

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