Gnutella is a decentralized file-sharing system whose participants form a virtual network and communicate peer-to-peer via the Gnutella protocol for distributed file search. To participate, a peer first connects to a known Gnutella host. Upon receiving a message, the servent decrements the time-to-live (TTL) field of the message. If the TTL is greater than 0 and the servent has never seen the identifier of the message (loop detection), it resends the message to all known peers. The servent also checks whether it should respond to the message. If it receives a Query, for example, it checks its local file store and responds with a QueryHit if it can satisfy the request. Responses are routed along the same path as the originating message.
Published in Chapter:
Peer-to-Peer Computing
Copyright: © 2009
|Pages: 6
DOI: 10.4018/978-1-60566-026-4.ch486
Abstract
The term peer-to-peer (P2P) was originally used to refer to network protocols where all the nodes had the same role and there were no nodes with specific responsibilities to act as the administrators or supervisors of a network (Ye, Makedon, & Ford, 2004). However, with the evolution of Internet as the dominant architecture for applications, contents, and services, applications and services have gradually migrated from the client-server paradigm to the edge services paradigm and now to the P2P computing paradigm. Therefore, nowadays, the term P2P refers to a class of systems and applications that use distributed resources to perform some function in a decentralized manner, where every participating node can act as both a client and a server (Ye et al., 2004). This article provides an overview of P2P computing, being focused on the types of multimedia distribution services and cooperation models in P2P systems. These models are classified regarding the functionality, the degree of decentralization, and the degree of structure of the information system.