On Wed, Oct 11, 2006 at 02:31:29PM -0400, Martin Gignac wrote: > On 10/11/06, Jon Radel <[EMAIL PROTECTED]> wrote: > > >>> If my memory serves me right, SIP actually has ALG built into the > >>> standard itself and www.opensip.org might already give you what you > >want. > >> > >> Hmm, wasn't aware of that. Do you have any specific RFC or 3GPP spec > >> number that I could check out concerning this? > >> > >> -Martin > >> > > > >The standard? But SIP has so many..... > > I was asking because although I'm familiar with the usual SIP RFCs > (3261 and family) I was not aware of the "SIP actually has ALG built > into the standard itself" notion that Girish mentionned and I wanted > to know if there was any actual documentation to support this. I am so sorry...
Did not realize that I was rubbing shoulders with giants... Good lesson for me to STFU when reqd. :) > > >But the core spec, RFC 3261, http://www.rfc-editor.org/rfc/rfc3261.txt , > >doesn't touch on the topic at all so far as I've ever noticed. > > Yeah, I've never heard of this in 3261 either. > > >NAT fixup for SIP is a nasty thing and I've seen a number of broken > >implementations and incompatible solutions. As a hosted IP PBX > >provider, we've had the best luck using session border controllers at > >the edge of our network, which are configured to assume that phones are > >behind NAT. > > Yeah, we use SBCs in IMS as well. > > >Unfortunately, SIP is nowhere near being "a" standard where you can > >assume interop just because you implement a bunch of RFCs. Especially > >if you mix NAT in. > > Add to that the 3GPP and OMA additions for IMS and it gets even wilder. > > -Martin Let me take a stab at guessing how things are going to turn out. I don't know when or if at all IPv6 is going to get deployed. Then NATs instead of disappearing as originally intended may actually get more widespread use. Horrors! I think ultimately some startup will come up with widely used VoIP solution and all NAT manufacturers will be forced to open up ports. It is the ports determination problem of FTP,RTP and other protocols that make operation across NATs so hard and unpredictable. If only ports were standardised better... Port negotiation should never be part of the protocol itself. But the world is not perfect and we have to live with it. regards, Girish
