NAT traversal ALG (application level gateway)

This applications can be installed on a linux NAT-box. They will rewrite your SIP messages 
and have some kind of UDP/RTP proxy for the media stream.

    * SaRP - SIP and RTP proxy: Perl implementation, License: GPL, Homepage: 
http://sourceforge.net/projects/sarp/.
    * siproxd: Siproxd is a proxy/masquerading daemon for the SIP protocol based on osip. 
License: GPL; Homepage: http://sourceforge.net/projects/siproxd/.