CSC445 Assignment 1: An exercise in measuring transfer times and throughput over TCP and UDP.

client side

• Python 3.3+
• numpy
• matplotlib

server side

• Python 3.3+

client side

python client.py [-h] [--client CLIENT] OUTPUT MODE TYPE HOST PORT

Launch server.

positional arguments:
  OUTPUT           Output directory
  MODE             Select mode of operation.
  TYPE             Choose between TCP or UDP for transmissions.
  HOST             Set host to connect to.
  PORT             Set port to use.

optional arguments:
  -h, --help       show this help message and exit
  --client CLIENT  Name of client, for use in plot titles.

server side

python server.py [-h] TYPE PORT

Launch server.

positional arguments:
  TYPE        Choose between TCP or UDP for transmissions.
  PORT        Set port to use.

optional arguments:
  -h, --help  show this help message and exit

First run from server name.host@example.com

python server.py TCP 8888

Then run from client

python client.py outdir all TCP name.host@example.com 8888

Server waits for an initialization message from the client. Client sends a 2-byte message, where the first byte represents the testing mode (either round-trip, throughput, or size-message count interaction), and the second byte is a parameter to the test mode (representing either message size or message count, as a power of 2). The server receives the message, prepares to receive from the client, and sends and ACK to the client.

For round-trip, the client simply sends a message to the server, and the server echoes it back as soon as possible. The client records the time elapsed.

For throughput, the server also echoes a message back to the client. Under TCP, we simply record the elapsed time, and divide two times the message size by the elapsed time to get throughput. Under UDP, we have to account for lost packets and timeouts. Both the client and server try to receive the full message, but if they time out, they just stop receiving and record the fact that they timed out. First the client and server echo the message, and the client records the elapsed time. Then the client subtracts its timeout from the elapsed time if it timed out, and the server sends an ACK or NACK to signify whether it timed out as well, and the client subtracts another timeout if that's the case. Instead of multiplying the received message size by two in the throughput calculation, we take (3 times the received message size + the sent message size) divided by two. This model assumes that exactly half of the packets were lost during each transmission. The throughput is calculated as the estimated transmitted data divided by the elapsed time.

Size-message count interaction is measured by sending a 1MiB message in varying packet-sizes from the client to the server. The server simply sends an ACK to the client, and the elapsed time divided by 1MiB is recorded.

The result of each of these tests is output to outdir as a box-and-whisker plot. A sample of these plots, run between several Oswego servers and my laptop over wifi, are in the results/ folder, and hosted here.