If you really want to learn security, you should get very familiar with TCP/IP.
You should understand what the 3 way handshake is, SYN, FIN, RST, ACK, ephermal ports, etc...

I would recommend learning what a port is and how they are used before trying to learn which port corresponds to a particular service.

You don't have to go too crazy.... There are some great resources on the Web that give good tutorials on TCP and IP... Here are a few for example:

http://www.pcsupportadvisor.com/TCP_...rial_page1.htm
http://www4.ulpgc.es/tutoriales/tcpip/pru/3376fm.htm
http://fringe.davesource.com/Fringe/...guages/TCP-IP/
http://www.pcnetworkadvisor.com/nasample/c04100-2.pdf


Good Luck !