In this paper, we present WIP - Web Service Initiation Protocol for multimedia and voice communication over IP. WIP is an entirely web service based communication protocol, consisting of a set of web service operations for initiating and establishing converged (e.g. multimedia, IM, voice, etc.) communication services over IP. It inherits the principle of separation signaling and media transmission of SIP (Session Initiation Protocol); but it relies on a single web service stack to provide a full featured communication signaling protocol.

WIP opens a new paradigm of web service based VoIP communication, which is extensible and can be easily integrated in end-to-end SOA solutions. The generic web service approach used in WIP overcomes many limitations which would be otherwise difficult to achieve in non-web service based communication methods used today. WIP is based on two-way, full duplex web service interaction. The communication signaling establishment in WIP is through web service interactions, and the media negotiation in WIP is modeled as a special web service "event" subscription, which is fully extensible for various media needs. The signaling messages of WIP are encoded in the standard based SOAP message envelops which can be carried by multiple transport protocols, including HTTP. WIP supports both P2P (peer-to-peer) and B2B (back-to-back) broker mode communication services. A prototype research system has been implemented, and the results indicate that WIP, as a full web service based communication protocol, is both feasible and advantageous.