1. Project3 - Congestion Control

2. Outline Overview Project Specification and Tasks Tools and Time Table

3. Overview BitTorrent-like file transfer application Reliability and congestion control protocol similar to TCP UDP based and C programming Allow regroup up to 3 members

4. Project Specification Intro to BitTorrent file transfer protocol Congestion control mechanism to ensure fair and efficient network utilization. Smart optimizations to get the best possible transfer time (extra credit).

5. Intro to BitTorrent A fixed-size chunk of 512Kbytes in pro3 Verification by rehashing Flooding, no tracker server Single master-file, different ownership BT = TCP, Project3 = UDP Hash( ) = =.torrent

6. Terminology master-data-file master-chunk-file 1e 34 b4 27 Peer A Peer B 1e 34 has- chunk-file Node.map Peer A Peer B GET b4 b4 27 has- chunk-file GET 34

7. File Transfer Requesting peer send “WHOHAS ” Responding peer send “IHAVE ” Decide, and send “GET ” Responding peer send multiple “DATA”

8. Packet Format MagicVersionType Header LenPacket Len Seq Num Ack Num Packet TypeCode WHOHAS0 IHAVE1 GET2 DATA3 ACK4 DENIED5 Packet Header Payload = hash list or data SPLIT PACKET LONGER THAN 1500 BYTES!

9. Provided Files  hupsim.pl – Emulates network topology using topo.map  sha.[ch] - The SHA-1 hash generator  input buffer.[ch]+bt parse.[ch] - Handle user input  debug.[ch] - helpful utilities for debugging output  peer.c - A skeleton peer file  nodes.map+topo.map - the hidden network topology

10. Project Tasks 100% Reliability & Sliding Window Congestion control *Intelligent Peer Selection and Caching

11. 100% Reliability & Sliding window Cumulative ACK Duplicate ACK SENDERRECEIVER Last ACKedLast Sent Last Available Next Expected Last Received

12. Congestion control Slow start : ACK received => window++ Congestion Avoidance : Window size = 1 after a loss (Simple Version) Fast Retransmit : Retransmit after 3 duplicate ACK Fast Recovery : No need to implement (But you may need it in Task3)

13. Tools Spiffy: Simulating Networks with Loss & Congestion sendto() => spiffy_sendto() Gnuplot and etc

14. TimeTable DateEventDescription 5/23Project3 releasedSTART EARLY 5/27CheckPoint1 (NO Hand in) WHOHAS flooding and IHAVE response 6/3CheckPoint2 (Hand in) Simple Chunk Download with stop-and-wait 6/8CheckPoint3 (NO Hand in) Sliding window flow-control with reliability 6/15CheckPoint4(Hand in) Simple Congestion Avoidance, with cwnd = 1 after any loss 6/19Early bird deadlineRequired functionality (+10 bonus points) 6/26DeadlineNo penalty

15. Thanks Good Luck & START EARLY!