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CS450: Introduction to Networking
Programming Assignment II
Prof. Jon Solworth
due dates:
Part I: 10 November 2004
Part II: 17 November 2004
1 Introduction
This assignment is to implement reliable packet delivery protocol on top of UDP. The pro- tocol should ensure reliable delivery of packets given that the types of errors are:
- Lost packets,
- Out-of-order delivery of packets,
- Corrupted packets, and
- Duplicate packets.
Assuming that the network is able to deliver some packets.
1.1 Part I
Since the network you’d be using will probably be fairly reliable, you will need to create your own faults. To do this you will write two procedures:
sendUdp does the actual sending of UDP packets and in addition will drop packets, corrupt packets, reorder packets, and duplicate packets. The packet errors can come from a file, specifying what’s to be done, or generated via probabilities and using a random number generator.
receiveUdp receives a UDP packet.
Here the sendUdp routine is part of the sender and the receiveUdp routine is part of the receiver. In addition to the above, the first part of the assignment will also require the program:
- to set an alarm (on the sender side) for each packet,
- to determine when a packet did not return within the time period,
- to detect what happened to the packet, and
- to acknowledge packets back to sender.
The purpose of this code is to generate the packet errors (on the sender side) and then determine what happened (on the receiver side): Recovering from the errors happens in Part II. After the packet is sent the sender waits T time for packet to be acknowledge, and then sets off an alarm. There should be two ways to determine T :
- The round-trip-time plus six times the standard deviation.
- Alternatively, the alarm should be set for a fixed time.
Note that this part is an attempt to deal with random events, both timing and packet errors, in two ways: A deterministic mode to enable testing and a random mode to mimic the real world.
2 Part II
You are to implement selective repeat for a window size of W packets, which is a parameter. You should produce:
- simulation scripts to test out your code,
- stress testing results, and
- documentation about 1) how your program is designed, 2) how your program is tested, and 3) what does and doesn’t work.
3 turnin
The turnin command is:
$ turnin -c cs450 -p a2_part# <cs-login>
The part# refers to the part number of the assignment(part1 or part2). To turnin your source and README files, store them in a directory with the same name as your cs login and turnin the entire directory. Also make sure you include a makefile that creates two executable named sender part# and receiver part# (# is either 1 or 2). (And please do not turnin any binaries or object code).
