[Sipwitch-devel] Peer-to-peer communication

[HK]

Hi,

I am just trying to get some knowledge on NAT, port forwarding and hole punching. While doing so, I can across, GNU SIP Witch.
Can somebody please clarify the following?
1) It says SIP witch is peer to peer VoIP server. Does this mean that for the initial call establishment server would be used and later for VoIP data, peer to peer communication is possible between the SIP clients ?

2)  It says: Calls can be made peer-to-peer behind NAT firewalls, and without needing a service provider.  What does this mean ?

3) Does SIP Witch use hole punching mechanism for peer to peer communication ?

Thank you.