framework for SIP modules

 Net::SIP is a Perl framework that provides many useful tools with which to
 write software for SIP endpoints (e.g phones, answer machines), SIP proxies
 and registrars. It contains no GUI and no real code for working with video
 or audio, though it does have some support for RTP (no RTCP) and working with
 PCMU/8000 and PCMA/8000 data.