oSIP is an implementation of SIP. This library aims to provide 
multimedia and telecom software developers an easy and powerful 
interface to initiate and control SIP based sessions in their 
applications. oSIP is little in size and code and thus could be 
used to implement IP soft-phone as well as embedded SIP 
software. oSIP does not intend to provide a high layer API for 
controlling "SIP Session" at this step. Instead, it currently 
provides an API for the SIP message parser, SDP message parser, 
and library to handle "SIP transactions."