Knowledge of Protocols

Hi, I have just finished C & linux application programming with a tinge of socket programming. I would like to know what do statements like the following mean -  "Have knowledge of Protocols such as TCP/IP, IPSec, IPV6 or SSL" Does it mean to have a theoretical view of the facets which constitute the protocol which can be done by reading RFC  or does it also mean to have implementation knowledge (code understanding) as well. I am not very clear about this statement which is generally used quite often. Secondly, it the latter understanding is correct (Theory - RFC + Implementation - Code) then where to look for the code which deals with a particular protocol ? Thanks !