Network Simulation and Data Capturing

As mentioned before, the two programs being used for simulation and data capturing are Nistnet and Ethereal. For nistnet we have written some scripts to automatically configure the network for certain network characteristics. It is expected that as more tests are run, additional scripts will become available. The scripts can be found inside ~testbed/nistnet in the network simulator, and should have the following naming scheme:

nistnet_<bandwidth>_<delay>_<drop>

For data capturing, we use filters which have the following form:

tcp port <port> and host thinserv and host thinclient

You should replace with the appropiate port as mentioned in section 2. Some of the standard ports may have been already saved as Ethereal filters. Click on the "Filters" button, and choose one from the list. If there isn't one for the platform you want, and this platform will be used again in the future, make sure to save the corresponding filter with the appropiate name. You'll thank yourself in the future.

To save space and facilitate the processing of the captured data, the sniffer should be set up so that it only captures the first 68 bytes of each packet. To do this, in the Capture dialog set "Limit each packet to" to the appropiate value. In addition, make sure the option "Update list of packets in real time" is not set.

When capturing has finished, save the data in libpcap format in the appropiate directory with a .pkt extension (e.g. ~testbed/data/<platform>/<name_describing_test-date>.pkt). The data is ready to be analyzed as described in section 5.