SIP User Agent(sipua) - software installed in VoIP-GSM gateways ELGATO. Now this software supports SIP via rfc3261, rfc3262. Back compatibility (for incoming requests) via protocol SIP rfc2543.
Ссылки:
http://en.wikipedia.org/wiki/Session_Initiation_Protocol
http://tools.ietf.org/html/rfc3261
http://tools.ietf.org/html/rfc3262
http://tools.ietf.org/html/rfc2543

SIP User Agent(sipua) - software installed in VoIP-GSM gateways ELGATO. Now this software supports SIP via rfc3261, rfc3262. Back compatibility (for incoming requests) via protocol SIP rfc2543.

Links:

+ Dev by wwsiter