Re: [Sipping] Re: draft-elwell-sipping-service-retargeting-00.txt

[David R Oran <[e-mail]>]

On Oct 19, 2005, at 1:02 AM, Dean Willis wrote:

> On Tue, 2005-10-18 at 16:22 -0500, Francois Audet wrote:
>
>
>> My issue is when the endpoint is "faking" the 486 because there was
>> never any
>> 486 received. I think a GW (or B2BUA or SIP phone) sending a 302  
>> with an
>> embedded
>> fake 486 just to make the other end believe (through History-Info or
>> not) that
>> it was Call Forward Busy is an abuse of the protocol.
>>
>> If there is a 486 Reason in there, it should be because there was  
>> a 486
>> received.
>>
>
> Well, if I send you a 302 because I would have sent you a 486 if I
> hadn't had an alternative (i.e. a call-forward because I was busy  
> here)
> is that faking?
>
>
Off the wall... (common for me)...
302 says "moved temporarily -please try this other contact, not me"
486 says "busy here" you'll have to figure out what if anything to do  
about this.

What we don't have a way of saying is "I'm busy, go try this other  
place".

One way to do that is to put a Reason header on the 302. That's more  
than a bit weird because it says you need more than the SIP response  
to tell you what's happening (Mary pointed this out in a message I  
just finished digesting).

Another way to do this is to allow a contact on a 486. That's also  
kind of weird.

A third way is to in fact invent a new 3xx which means exactly "Try  
this other place because I'm busy" (as opposed to moved temporarily).

Why don't we just do the last of these? It's completely  
straightforward to me.

Dave.

P.S. In terms of the debate over "telling you what happened so you  
can figure out what the right thing to do is" versus "telling the SIP  
infrastructure exactly what to do", I have consistently been in the  
former camp. In fact, that reasoning was one of the things that  
motivated both the Reason header and the History-Info work. I have a  
strong preference to avoid putting service directives into URIs  
except as a last resort, and only then when you know EXACTLY what you  
want a server to do and can ensure that the request in fact gets  
routed to that server.


> Can't I legimately file a "History-Info" saying I redirected you for a
> reason? If so, what other reason would you suggest I use?
>
> What if the 302 were being generated bya B2BUA instead of a  
> terminal UA?
>
> Or is History-Info just sort of broken when generated by a UA?
>
> --Dean
>
>
>
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