[Serusers] Rewriting URI in the Contact field

Maxim Sobolev sobomax at FreeBSD.org
Tue Jan 14 11:14:50 CET 2003


Jiri Kuthan wrote:
> 
> Isn't the ATA able of "double registration" (see draft-ietf-sipping-nat-scenarios-00.txt) ?
> I thought it was able to register, look at received and rport and re-register
> then again with the host/port it learned from reply to the first registration.
> 
> Or does it do so only for IP address (received) and not for port numbers (rport)?

Unfortunately it doesn't do it yet neither for received nor for rport.

-Maxim

> 
> -Jiri
> 
> At 03:15 PM 1/10/2003, Maxim Sobolev wrote:
> >Yes, I know - we have studied all those methods in details. Our
> >method of choice is symmetric signalling/symmetric media (aka COMEDIA)
> >due to the following reasons:
> >
> >1. Things should work without modifying or reconfiguring existing
> >user's infrastructure (NATs) and should be compatible with all
> >widely-used NATs.
> >
> >2. We are bound to ata186 as UA. It is compatible with this method.
> >Support for other UAs isn't required.
> >
> >3. The calls will be terminated to Cisco GWs, while COMEDIA support
> >was recently added into Cisco IOS, so that theoretically the only
> >thing we need is to add received/rport support into proxy/registrar
> >and update IOS at termination points.
> >
> >4. No media relay is allowed, because this will create excessive
> >bandwith load in a single point.
> >
> >5. COMEDIA support is likely to become part of the standard, so that
> >our investments into development are protected.
> >
> >-Maxim
> >
> >On Fri, Jan 10, 2003 at 02:26:07PM +0100, Jiri Kuthan wrote:
> >> There is actually a plenty of options how to traverse NATs.
> >> Sadly, none of them works in all possible scenarios.
> >>
> >> a) STUN -- some phones (kphone for linux, snom hardphones)
> >>    have the ability to "fool" NATs to accomplish traversal
> >>    using the STUN protocols; particularly good if you cannot
> >>    manipulate the NAT
> >> b) geek tweaks -- you have a configurable NAT and configurable
> >>    phones (there are some of both of them).  you configure static
> >>    port forwarding in the NAT and phones to advertise the
> >>    public address in contacts and elsewhere
> >> c) ALG -- use a SIP-aware NAT such as PIX or Intertex
> >> d) UPnP -- takes UPnP enables phones (snom is) and NATs
> >> e) SIP/media relay -- that's a too ugly story
> >>
> >> What to choose best depends on your network setting -- can you
> >> tweak the NAT, can you afford replacing it with a SIP-enabled
> >> one, are the phones you are using configurable or do they use
> >> STUN, do you have a server on the public or private NAT side
> >> or on each of them, etc.
> >>
> >> I remember someone shared with us he was using ser in his
> >> network to do the translation of SIP addresses on behalf
> >> ot the phones. The ser script was configured to statically
> >> rewrite private IP addresses to the public address using
> >> replace/textops.
> >>
> >> -Jiri
> >>
> >> At 01:32 PM 1/10/2003, Maxim Sobolev wrote:
> >> >Folks,
> >> >
> >> >I need an advise on how to better implement one feature, which isn't
> >> >currently present in SER. We need to allow UAs behind NAT properly
> >> >register with the registrar - by "properly" I mean that host:port portion
> >> >of URI in Contact field should not be used, but host:port the request
> >> >came from should be used instead. By definition we know that those UAs
> >> >will support symmetric SIP signalling, so that this scheme will work just
> >> >fine.
> >> >
> >> >In my opinion there are two ways to do it: either add new rewritecontact*
> >> >family of functions similar to rewritehost ones. or add a new flag for
> >> >the save() function. This is where I need your help - which implementation
> >> >looks better for you (or maybe you have even some better idea), since
> >> >we are really interested in inclusion of our changes into the mainline to
> >> >reduce our local hacks.
> >> >
> >> >Regards,
> >> >
> >> >Maxim
> >> >
> >> >_______________________________________________
> >> >Serusers mailing list
> >> >serusers at lists.iptel.org
> >> >http://lists.iptel.org/mailman/listinfo/serusers
> >>
> >> --
> >> Jiri Kuthan            http://iptel.org/~jiri/
> 
> --
> Jiri Kuthan            http://iptel.org/~jiri/



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