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Review Session I

Join us for the final exam review session for EE 122: Introduction to Communication Networks, taking place on December 16th from 8-11 AM in 105 Stanley Hall. The exam is closed book and will allow one double-sided 8.5x11 crib sheet. It will cover the entire semester, with a focus on the material: 30% before the midterm and 70% after. Note that socket programming, advanced routing, and aspects of peer-to-peer or future networking topics will not be part of the exam. Prepare for important concepts like TCP, congestion control, and interdomain routing.

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Review Session I

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  1. Review Session I EE 122: Intro to Communication Networks Fall 2010 (Tuesday 7th December) Sameer Agarwal http://inst.eecs.berkeley.edu/~ee122/

  2. Announcements • 16th December 8-11 AM @ 105 Stanley • Closed book, with single 8.5x11 (both sides) crib sheet • Exam covers entire semester • Roughly 30% before midterm, 70% after midterm • Following is not a part of Finals: • Socket Programming • Designing in 90 minutes • Advanced routing (except what’s in final review) • P2P (except what’s in final review) • The Future of Networking

  3. TCP & Congestion Control

  4. segment 1 SS:cwnd = 1 ACK 8 ACK 2 SS:cwnd = 2 SS:cwnd = 2 segment 3 ACK 9 ACK 3 ACK 10 ACK 4 AIMD:cwnd = 3 SS:cwnd = 4 segment 4 segment 5 segment 6 segment 7 ACK 4 Timeout! Set SSthresh ACK 4 segment 10 segment 12 segment 11 segment 8 segment 9 segment 4 SS:cwnd = 1 Vanilla TCP segment 2 ACK 4

  5. segment 1 SS:cwnd = 1 ACK 2 ACK 8 SS:cwnd = 2 SS:cwnd = 2 segment 3 ACK 9 ACK 3 ACK 10 ACK 4 AIMD:cwnd = 3 SS:cwnd = 4 segment 4 segment 5 segment 6 3 Dup ACKs! Set SSthresh SS:cwnd = 1 segment 7 ACK 4 ACK 4 segment 12 segment 10 segment 11 segment 8 segment 9 segment 4 TCP+ Fast Retransmission segment 2 ACK 4

  6. segment 1 SS:cwnd = 1 ACK 2 ACK 8 AIMD:cwnd = 3 SS:cwnd = 2 segment 3 ACK 9 ACK 3 ACK 10 ACK 11 ACK 4 AIMD:cwnd = 4 SS:cwnd = 4 segment 4 segment 5 segment 6 3 Dup ACKs! Set SSthresh AIMD:cwnd = 2 segment 7 ACK 4 ACK 4 segment 11 segment 10 segment 12 segment 8 segment 9 segment 4 TCP+ Fast Retransmission & Fast Recovery segment 2 ACK 4

  7. Question 1a (‘Vanilla’ TCP) Note: Slightly modified from review session Set SSthresh = 5; Enter Slow Start SSthresh = 5 crossed. Enter AIMD Set SSthresh = 1; Enter directly into AIMD since SSthresh is already crossed.

  8. Question 1b (TCP Retransmission + Fast Recovery) Set SSthresh = 5; However, enter AIMD direclty! Set SSthresh = 1; Enter directly into AIMD since SSthresh is already crossed.

  9. Interdomain Routing

  10. 3 2 2 4 9 6 3 1 Border router Internal router IGP, eBGP, iBGP,…. • Provide internal reachability (IGP) • Learn routes to external destinations (eBGP) • Distribute externally learned routes internally (iBGP) • Select closest egress (IGP)

  11. Routing Follows the Money! • Peers provide transit between their customers • Peers do not provide transit to each other traffic not allowed traffic allowed

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