Computer science project for BSc

I want to do my final year project in network security. It has to be a research and practical project. I am thinking of designing and implimenting a local area network with a fire wall. or designing and implimenting a protocol security for a network.
I am open to suggestions and ideas about how to go about this. I will also reconsider doing something along these lines if anybody can help with project topics relating to network security. It has to be a project involving some amount of research and a pratical implimentation.

Thanks Guys.