Yes I am of that same opinion - that any real "IP-PBX" or whatever big enough NOT to be doing Registration, and to instead do static provisioning or DNS, would be given a static hole/DMZ address in their firewall/NAT. But some of my customers have told me otherwise. (interestingly mostly in APAC region) There's also some concern that while a static entry is there for inbound TCP connections, the PBX creates outbound ones to the service provider which are ephemeral port sources and need to live for very long durations (though why they can't just do TCP keepalive is beyond me, but I'm no expert).
But anyway, the big issue we've seen is that we need both the PBX and the service provider box to detect failure before an active call/request attempt is made; to trigger alternate route selection without waiting for transport failure, and as a method to detect liveness again and revert. Today that's almost exclusively done with Options requests as far as I've seen, and lots of people don't seem to like that. -hadriel > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Sent: Wednesday, June 25, 2008 3:11 PM > To: [EMAIL PROTECTED]; Hadriel Kaplan; [EMAIL PROTECTED]; > [email protected] > Cc: [EMAIL PROTECTED] > Subject: RE: [Sip] Progress draft-holmberg-sip-keep: proxy-to-proxy use > case > > Hi, > > I'm a bit sceptical about the need for keep-alives between proxies. It > is of course entirely possible that an enterprise PBX is connected to > (or peering with) a service provider proxy through a NAT and/or a > firewall. However, wouldn't such a NAT or firewall be under the > administration of either the enterprise itself or its ISP (who quite > often would be the SIP service provider), and the required port > forwardings or firewall rules could be set through administration. This > means that there would not be need for keepalive traffic to implicitely > keep the mapping/pinhole open. > > Or are there really deployment cases where there are SIP PBXs behind > unadministrated NATs or firewalls? > > Wouldn't we then need keepalives for SMTP as well, or how has the e-mail > infrastructure managed to solve this problem? > > Markus > _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
