Re: [Sip] Dual registration without Outbound

["DRAGE, Keith \(Keith\)" <drage at alcatel-lucent.com>]

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: sip-bounces at ietf.org [mailto:sip-bounces at ietf.org] On 
> Behalf Of Dean Willis
> Sent: Tuesday, October 07, 2008 11:17 PM
> To: Paul Kyzivat
> Cc: sip at ietf.org; 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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