Command line equivalent for ethereal

[Scott Kitterman]

I'm suffering from an intermittent upstream connectivity problem.  I would 
like to capture some data to try and understand the problem better.

Unfortunately, the only boxes I have in the right place on the network to 
capture the data do not have X installed and Ethereal demands X as a 
dependency.  I'd rather not install X windows and the related software on a 
remote server just to capture data.

Does anyone know of a program that's roughly equivalent to Ethereal for 
capturing packet data that will work just from the command line and is 
available for Ubuntu 6.06?

Scott K