I'm writing a paper on Distributed Social Network. Where can I get information?

I don’t know how knowledgeable you are so I’ll assume you don’t know much and point you here first: https://www.eff.org/deeplinks/2011/03/introduction-distributed-social-network

Also try this: http://www.w3.org/2005/Incubator/federatedsocialweb/wiki/Protocols

Having an overview of some protocols (and following the links) will help you understand project goals and give you good ideas of where the federated web is headed.

Hopefully this’ll be a good start.