Over the past several years, Internet users have changed in their usage p- terns from predominately client/server-based Web server interactions to also involving the use of more decentralized applications, where they contribute more equally in the role of the application as a whole, and further to d- tributed communities based around the Web. Distributed systems take many forms, appear in many areas and range from truly decentralized systems, like Gnutella, Skype and Jxta, centrally indexed brokered systems like Web s- vices and Jini and centrally coordinated systems like SETI@home. From P2P...