no race conditions associated with editing the same file, and no need for elaborate synchronization between peers. Each resource registration contains parameters that can be used to specify the type of mapping. C 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security 9.5.4 The Resource Lookup Algorithms M. Zangrilli and D. Bryan have described how a structured peer-to-peer algo- rithm can be used for resource lookup by a P2P SIP peer protocol. Refer- ence [20] describes how to integrate a DHT based on Chord with dSIP while reference [22] describes how to integrate a DHT based on Bamboo with dSIP. The dSIP draft is extended to provide possible implementations of pluggable DHT algorithms. The Chord algorithm has been adapted to use SIP messages, as specified by dSIP, to communicate between peers in the overlay. Messages are routed by taking advantage of a key property of the Chord finger tables. A peer has more detailed, fine-grained information about peers near it than farther away, but it knows at least a few more distant peers. When locating a particular ID (either resource-ID or peer-ID), the peer will send the request to the finger table entry with the peer-ID closest to the desired ID. Because the peer receiving the request has many neighbors with similar peer-IDs, it will presumably know of a peer with a Peer-ID closer to the ID, and suggests this peer in response. The request is then resent to this closer peer. The process is repeated until the peer responsible for the ID is located, which can then determine if it is storing the information [20]. Bamboo uses prefix routing. Messages are routed SO that each hop will result in a peer that either shares a larger prefix with the ID being searched or shares the same length prefix as the previous hop's peer-ID, but the new peer's peer-ID is numerically closer to the ID than the previous hop's peer-ID. To route a message to a particular ID, the peer first looks to see if any of the peers in its leaf set are responsible for the ID. I