GNU SIP Witch is a secure peer-to-peer VoIP server that uses the SIP protocol.
Calls can be made peer-to-peer behind NAT firewalls, and without needing a
service provider. GNU SIP Witch does not perform codec operations and thereby
enables SIP endpoints to directly peer negotiate call setting and process peer
to peer media streaming even when when multiple SIP Witch call nodes at multiple
locations are involved. This means GNU SIP Witch operates without introducing
additional media latency or offering a central point for media intercept or
capture. GNU SIP Witch can be used to build secure and intercept-free telephone
systems that can operate over the public Internet.

GNU SIP Witch is designed to support network scaling of telephony services,
rather than the heavily compute-bound solutions we find in use today. This means
a call node has a local authentication/registration database, and this will be
mirrored, so that any active call node in a cluster will be able to accept and
service a call. This allows for the possibility of live failover support in the
future as well.