Re: Dual registration without Outbound

Right.

Outbound has a "redundancy" mechanism for the proxy embedded in the spec.

What is being asked is a redundancy mechanism for the UA (based on dual homing).

My reaction is that I don't see why a redundancy mechanism  for the UA should even
be tied to draft-ietf-sip-outbound. It seems to be attempting to use a small side effect
of outbound.

Rather, I think this should be a new draft, and it should be independent from outbound.
We already have a mechanism that allows for a q-value in a contact to indicate a desire for
different forking priorities.

I think another URI parameter for a Contact indicating that 2 different contacts are 
effectively the same (because of dual homing) would do the trick, and would not 
require outbound. Or maybe a parameter that says "alternative" to indicate that it's an
alternative to a specific contact (that has the advantage of telling the Registrar which
one is preferred which is apparently required).

Bottom line is I don't think Outbound is a good sledgehammer to use for this problem.

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On 
> Behalf Of DRAGE, Keith (Keith)
> Sent: Tuesday, October 07, 2008 16:45
> To: Dean Willis; Paul Kyzivat
> Cc: [email protected]; Christer Holmberg
> Subject: Re: [Sip] Dual registration without Outbound
> 
> I am becoming concerned that we are now at this late stage 
> going into requirement inflation. This appears to be such.
> 
> I do not remember a requirement to provide redundant 
> connections to registrars as amongst the original requirements.
> 
>    1.  Must be able to detect that a UA supports these mechanisms.
>    2.  Support UAs behind NATs.
>    3.  Support TLS to a UA without a stable DNS name or IP address.
>    4.  Detect failure of a connection and be able to correct for this.
>    5.  Support many UAs simultaneously rebooting.
>    6.  Support a NAT rebooting or resetting.
>    7.  Minimize initial startup load on a proxy.
>    8.  Support architectures with edge proxies.
> 
> 
> Regards
> 
> Keith
> 
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]] On 
> Behalf Of 
> > Dean Willis
> > Sent: Tuesday, October 07, 2008 11:17 PM
> > To: Paul Kyzivat
> > Cc: [email protected]; Christer Holmberg
> > Subject: Re: [Sip] Dual registration without Outbound
> > 
> > 
> > On Oct 7, 2008, at 3:37 PM, Paul Kyzivat wrote:
> > 
> > > I think I am missing something here. I presume that the
> > knowledge of
> > > the UA is limited to:
> > > - to proxy addresses
> > > - an AOR to register
> > >
> > > Presumably the address of the registrar is derived from 
> the AOR to 
> > > register by removing the user part. So the UA, when registering, 
> > > doesn't specify two different registrars. Whether there are
> > two or not
> > > is a function of how the proxy routes the register request. 
> > So whether
> > > the two registers for the same contact go to one registrar
> > or two is
> > > unknown to the UA. In some configurations this would give you 
> > > redundancy, and in others it would not.
> > >
> > > Then, what causes the UA to register two different
> > contacts? Are the
> > > wlan contact and the 3g contact registered to *different*
> > AORs? If not
> > > I don't see the point. If anything, I would expect that 
> 3g and wlan 
> > > represent access networks and hence differing proxies, 
> not AORs or 
> > > registrars.
> > >
> > 
> > Some IMS networks have mechanisms for discovering the  edge proxy 
> > based on the air interface. This, a UA might discover one proxy for 
> > its 3g interface, and another for its WLAN interface. In 
> other words, 
> > one proxy for each Contact.
> > 
> > So, that's "proxy" discovery.
> > 
> > Registrar discovery is a separate process. With 
> config-framework, the 
> > UA is configured with a set of proxies with which it may register.
> > Under outbound-015, if there are two or more outbound 
> proxies in the 
> > configured set, the UA must register through at least two of those 
> > proxies. This assumes a singular contact at the UA.
> > 
> > Juha has, IIRC, proposed that the UA must register with at 
> least two 
> > of those proxies for each contact. This, I believe, has some merit.
> > I'm not sure it's a MUST, but it certainly seems a 
> reasonable SHOULD.
> > 
> > Of course, when the configuration mechanism is different 
> and only one 
> > proxy is provided per contact, we have a different case.
> > 
> > It seems like we are developing two conflicted use cases here
> > -- one for a singular contact with redundant registration 
> paths, and 
> > another for redundant contacts, each with singular 
> registration path.
> > 
> > Then there may be yet another case, multiple contacts, each with 
> > redundant registration paths.
> > 
> > --
> > Dean
> > 
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