Peer-to-peer SIP (P2P-SIP) is an implementation of a distributed voice over Internet Protocol (VoIP) or instant messaging communications application using a peer-to-peer (P2P) architecture in which session control between communication end points is facilitated with the

Session Initiation Protocol The Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, and terminating communication sessions that include voice, video and messaging applications. SIP is used in Internet telephony, in private IP telepho ...

(SIP).

SIP in a P2P architecture

In a pure peer-to-peer application architecture no central servers are required, whereas traditional SIP telephony networks have relied on using centrally deployed and managed SIP servers, in analogy to the centralized switching architecture of the

public switched telephone network The public switched telephone network (PSTN) provides Communications infrastructure, infrastructure and services for public Telecommunications, telecommunication. The PSTN is the aggregate of the world's circuit-switched telephone networks that ...

(PSTN).RFC 3261, ''SIP: Session Initiation Protocol'', J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, E. Schooler, The Internet Society (June 2002) P2P application design can improve scalability and survivability in the event of central network outages. The Session Initiation Protocol is in principle a client-server protocol, however it has been described in analogy to the P2P relationship, called a ''dialog'', which is defined by a unique combination of SIP protocol parameters (To-tag, From-tag, Call-ID). Both endpoints of a communication session implement a user-agent server and a user-agent client, which enables any two

user agent In computing, a user agent is any software, acting on behalf of a user, which "retrieves, renders and facilitates end-user interaction with Web content". A user agent is therefore a special kind of software agent. Some prominent examples of us ...

s to communicate directly with one another without the mediation of another a central switching system. SIP also provides facilities of registering (REGISTER request) the network location of a user agent with other SIP elements and subscription (SUBSCRIBE request) and notification (NOTIFY request) features for event tracking between user agents. Based on these inherent SIP features it is possible to construct a peer-to-peer network of SIP nodes. In another approach, SIP over P2P, the SIP location service is replaced by conventional P2P overlay networking approach, such as the OverSim framework. In this model, the overlay network is used for service or node discovery and rendezvous. The search key in such a mechanism is the

Uniform Resource Identifier A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, conc ...

(URI) of a user agent. This URI requires resolution to a particular device or Uniform Resource Locator (URL) that must be performed in real time. P2P-SIP systems may employ structured peer-to-peer approaches, as well as unstructured peer-to-peer architectures.

Standards

The Internet Engineering Task Force (IETF) is conducting a working group (P2PSIP) that develops standards-track specifications for P2P-SIP. This effort is based on using the ''REsource LOcation And Discovery (RELOAD) Base Protocol'' a peer-to-peer (P2P) signaling protocol for use on the Internet. The P2P signaling protocol provides the network nodes that form an overlay network with abstract storage, messaging, and security services.

References

External links

The OverSim home page

P2PSIP demonstrator based on P2PNS
* * * A code library for P2P over SIP
Sip2Peer project
{{DEFAULTSORT:P2p-Sip Peer-to-peer computing Voice over IP