Design and implement a media and signaling gateway for the SIPXECS platform. The media gateway should support the following functionality:

See ( http://sipx-wiki.calivia.com/index.php/Requirements_for_a_B2BUA ) :


- The firewall opens SIP and RTP ports and port forwards traffic to the sipXecs SIP trunking B2BUA
- The sipXecs SIP trunking GW anchors media and provides rewriting of the SIP headers so that packets can pass the firewall / NAT
- The sipXecs SIP trunking GW handles refers vs. re-invites
- We can assume that the ITSP uses a public IP address (no far-end NAT)
- Allows SIP registration with a SIP trunking provider
- In a phase 1 does not provide additional security in the form of deep packed inspection as Ingate does
- The sipXecs SIP trunking GW should support one or two Ethernet interfaces. I.e. It should be possible to support a one-arm connection where incoming and outgoing traffic is on the same subnet, or it should be possible to bind the left and right side of the B2BUA to two respective interfaces or subnets.

The phase 1 focus should be:

- Media anchoring and processing
- SIP signaling rewrite for NAT traversal
- SIP registrations with an ITSP
- Reduce packet size (sipXecs internal packet size too big to be handled by most ITSPs)
- Refer vs. re-invite to allow transfers
- Performance: Support for at least 2 x T1 channels
- Reusable media framework: We would like to use this for other components such as conferencing, media server, etc.