As the population of peer-to-peer (P2P) networks increases, service differentiation issues become very important in distinguishing cooperating peers from free-loaders.  The first part of this talk would focus on: 1) defining parameters that are suitable for service differentiation in P2P networks, 2) outlining SDP, a protocol to accomplish service differentiation.
The basis for service differentiation could either be economic or the fact that the peers differ from each other in the type of services and resources they contribute to the system.  A system to measure the contributions of individual peers in the system is often referred to as the "reputation system" and can be used in a variety of contexts.  Since pricing issues are yet to be resolved in P2P networks, we adopt the approach of using peer reputations to accomplish service differentiation.  In the second part of the talk, I will describe the set of features necessary in such a reputation system.  I will also outline how the reputation system previously developed by us is suitable for the purpose.

The primary components of this talk are derived from our works published at NOSSDAV'03 and NGC'03.