I'm using a NetBSD box as a firewall at a client site, and
they're starting to want to play with SIP for VoIP phones,
they have a PBX (asterisk) at a datacentre, and want to
have a bunch of handsets at their office (behind the ip filter
firewall on the NetBSD (3.1) box.

I've had a bit of a poke around in pkgsrc and found partysip and
ser, and am wondering if these, or anything else, would be
recommended for pushing the SIP traffic through the firewall?
Something like the ftp module for ipfilter, or some sort of
application-level proxy like squid etc?

Any hints?

Thanks

Carl