i found it as a good read, so, for Linux members they can get the best out of this link:

http://seifried.org/lasg/network/

hints:

Listing open ports in Linux and finding out which applications are using them (using ps, netstat and lsof)

in this doc. Seifried covers the bottom 4 or so layers (transport, network, datalink, physical) of the 7 layer OSI protocol stack, he also cover some of the basic network configuration files, since an explanation is always useful.

enjoy learning

-bimmer