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Effective Data Transmission Strategies in Network Communication

Explore the importance of sliding window protocol in ensuring data transmission efficiency. Learn about Individual ACKs, Cumulative ACKs, and the impact of lost ACKs. Discussing efficiency, timeliness, and packet loss scenarios.

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Effective Data Transmission Strategies in Network Communication

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  1. Reliable Transport EE 122 Discussion 9/19/11

  2. Announcements • Handouts and notes from discussion are posted on the course webpage • Bandwidth-delay product: answer corrected • Reminder: Homework-1 due today!

  3. Questions 1 and 2

  4. Sliding Window • Ensures the “pipe” is always full (efficiency) • Send W packets • When one gets ACK’ed, send the next one in line • If a packet times out, retransmit

  5. Individual ACKs and Cumulative ACKs • Individual ACK • Acknowledge every packet received • Loss: resend packet when k “subsequent packets” are received • Cumulative ACK • Highest packet number for which all previous packets have been received • Loss: resend missing packet upon k “duplicate ACKs” and wait for ACK

  6. Question 4a – Individual ACK A B 1 2 3 1 2 3 4 5 6 7 8 9 10 ACK-1 , ACK-2, ACK-3 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 ACK-4 , ACK-5, ACK-6 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 10 ACK-7 , ACK-8, ACK-9 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 ACK-10 1 2 3 4 5 6 7 8 9 10

  7. Question 4a – Cumulative ACK A B 1 2 3 1 2 3 4 5 6 7 8 9 10 CACK-upto1 , CACK-upto2, CACK-upto3 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 CACK-upto4 , CACK-upto5, CACK-upto6 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 10 CACK-upto7 , CACK-upto8, CACK-upto9 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 CACK-upto10 1 2 3 4 5 6 7 8 9 10

  8. Question 4b (k=1) A B 1 2 3 1 2 3 4 5 6 7 8 9 10 ACK-1, ACK-3 1 3 k=1 2 4 1 2 3 4 5 6 7 8 9 10 ACK-2 , ACK-4 1 2 3 4 567 1 2 3 4 5 6 7 8 9 10 ACK-5 , ACK-6, ACK-7 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 ACK-8, ACK-9, ACK-10 1 2 3 4 5 6 7 8 9 10

  9. Question 4b (k=2) A B 1 2 3 1 2 3 4 5 6 7 8 9 10 ACK-1, ACK-3 1 3 4 1 2 3 4 5 6 7 8 9 10 ACK-4 1 3 4 k=2 2 1 2 3 4 5 6 7 8 9 10 ACK-2 1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 10 ACK-5, ACK-6, ACK-7 1 2 3 4 5 6 7 …

  10. Question 4b (k=2) – Why bother? A B 1 2 3 1 2 3 4 5 6 7 8 9 10 ACK-1, ACK-3 1 2 3 4 1 2 3 4 5 6 7 8 9 10 ACK-2, ACK-4 1 2 3 4 ACK-2 is delayed 5 6 7 1 2 3 4 5 6 7 8 9 10 ACK-5, ACK-6, ACK-7 1 2 3 4 5 6 7 Efficiency vs. timeliness 8 9 10 1 2 3 4 5 6 7 8 9 10 ACK-8, ACK-9, ACK-10 1 2 3 4 5 6 7 8 9 10

  11. Question 4d (k=1) – Lost ACK A B 1 2 3 1 2 3 4 5 6 7 8 9 10 ACK-1, ACK-3 1 2 3 k=1 ACK-2 is lost 2 4 1 2 3 4 5 6 7 8 9 10 ACK-2 , ACK-4 1 2 3 4 567 1 2 3 4 5 6 7 8 9 10 ACK-5 , ACK-6, ACK-7 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 ACK-8, ACK-9, ACK-10 1 2 3 4 5 6 7 8 9 10

  12. Question 4d (k=1) – Lost CACK A B 1 2 3 1 2 3 4 5 6 7 8 9 10 CACK-upto1, CACK-upto3 1 2 3 CACK-upto2 is lost 4 5 6 1 2 3 4 5 6 7 8 9 10 CACK-4 , CACK-5, CACK-6 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 10 CACK-7 , CACK-8, CACK-9 1 2 3 4 5 6 7 8 9 11 packets with Lost ACK vs. 10 packets with Lost CACK 10 1 2 3 4 5 6 7 8 9 10 CACK-10 1 2 3 4 5 6 7 8 9 10

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