Layer2 software design

Hi Board members, I have good knowledge with unix internals and programming. But suddenly I wanted to become a datacom developer.. lol. I have read a good amount about networking and various layer 2 protocols and some routing protocols. However, I could not find any material discussing about the layer2 software design itself. Though I learnt protocols I am not able to face Layer 2 interviews from a software design point of view.

Are there any good online source for getting some layer 2 software development knowledge.