help learning to read tcpdumps and network captures

[Teodorski, Chris]

Can anyone point me to a good resource to learn how to read these?   I have been 
running ethereal.....and I'm trying to make sense of what I have in my capture.  

To try and learn, I used an easy one....I caputured FTP traffic, since I knew it would 
be in clear text.......okay....so I see how that works, but now I want a better 
understanding.....

Any suggestions?

Thanks,

Chris