Plaintext transmission over Session Initiation Protocol

This paper compares two telecommunication standards for plaintext transmission over Session Initiation Protocol (SIP): SIP extension for Text over Internet Protocol (ToIP) and SIP extension for Instant Messaging (IM). ToIP provides a real-time text service, while IM provides a near realtime text service. Originally, SIP is a Voice over Internet Protocol (VoIP) call signaling protocol that uses Real-time Transport Protocol (RTP) for handling audio/video media sessions. ToIP required an established RTP session for text payloads while IM does not. VoIP, ToIP and IM cooperate on IP networks in order to meet requirements for speech-capable or speech-impaired individuals in using communication facilities. There are several VoIP servers that implements SIP protocol stack. Asterisk is an open-source Internet Protocol — Private Branch eXchange (IP-PBX) that supports popular audio, video, text, and any other form of media protocols. Since SIP extension for ToIP requires an established RTP session, in this paper ToIP compares with SIP extension for IM that process text outside of RTP session. Built-in modules of Asterisk and SIPp performance tester are used to compare the performance of these standards.