Chiu, Dah MingDah MingChiuHuang, J.Liu, Q.Lei, Z.2021-11-292021-11-292012991637531507541https://repository.sfu.edu.hk/handle/sfu/1957When peer-to-peer (P2P) networks meet <i>social networks</i> (for instance, Facebook), the former develops new characteristics. A notable change is that peers would use real names in social networks, and hence the P2P networks become naturally clustered according to the human relationship imported from the social networks. Conceivably, social network theories can be applied to improve the performance of P2P networks. This chapter introduces the social network theories, including <i>small world</i> (six degrees of separation), <i>weak ties</i>, <i>structural holes</i>, and others, and their applications in P2P networks. Specifically, the chapter describes applications of social networks in P2P networks using <i>network coding</i> as well as social networks in P2P <i>content-centric networking</i> (CCN) or <i>named data networking</i> (NDN), which is a brand-new framework for future communications.book part10.1007/978-1-4471-4048-1_12