1. Reliable Transport
CS 3700 Project 3

2. Goals
You will write a program that implements reliable transport on top of UDP
Think of it as TCP-lite
Deliver a file reliably from a sender to a receiver
Your program will be tested under various kinds of lossy network conditions
Packet drops
Packet reordering
Packet duplication
Network bandwidth and latency will also be varied
Grade based on correctness, performance, style and documentation
10% of your total grade, not as hard as project 2

3. Command Line Syntax $ ./3700recv
$ ./3700send <recv_host>:<recv_port>
Receiver prints out its port
Receiver’s IP and port are given to the sender
Sender expects to read the input file from STDIN
Helper script will automatically run the sender and receiver
./run [--size (small|medium|large|huge)] [--printlog] [--timeout <seconds>]

4. The Simulator
Today’s networks are too fast and reliable to be interesting
You’ll be testing your code in a simulator
Available on cs3600tcp.ccs.neu.edu
You must use this machine to test your code
Configuring the simulated network
$ /course/cs3700f16/bin/project3/netsim [--bandwidth <bw-in-mbps>] [--latency <latency-in-ms>] [--delay <percent>] [--drop <percent>] [--reorder <percent>] [-- duplicate <percent>]

5. The Protocol You can implement your packet headers however you see fit
UDP gives you port numbers
Everything else is up to you
Things you may want
Sequence and acknowledgement numbers?
Flags (SYN, FIN, ACK)?
Receive window size?
Checksums? Cryptographic hashes?
Selective ACK?

6. Other Considerations What about congestion control?
You’ll be tested on network links with different maximum capacities
You’ll need to manage tradeoffs between probing for additional capacity versus sending too fast and inducing packet drops
Speed and efficiency matter
You should try and cram as many bytes of data into each packet as you can, subject to MTU restrictions (plus IP and UDP overhead)
Minimizing retransmissions is key
How do you close the connection?
FIN packets may drop

7. Performance Testing We provide a script that runs all test cases
In addition to passing all tests (correctness), we will also be grading you based on performance
How fast did you complete the file transfer? (Lower times are better)
How many total bytes did you send? (Lower is better)
Leaderboard showing everyone’s performance on the test cases
$ /course/cs3700f16/bin/project3/printstats

8. Turning in Your Project
Register your group
All group members must run the script!
Create a directory for your files
All of your (well documented) code
Makefile
README
Run the turn-in script

9. Grading 10% of your total grade, due Friday October 26
75% for program correctness, i.e. passing all test cases
15% for performance
10% for style and documentation