Subject: [SIP] Proxy Routing Logic

From: [email-masked]
Date: Fri, 29 Dec 2000 17:38:10 -0600

Jonathan Rosenberg wrote
> > -----Original Message-----
> >  From: Keith Robinson [mailto:[email-masked]]
> >Sent: Monday, December 18, 2000 6:01 AM
> >To: Billy Biggs
> >Cc: SIP List
> >Subject: Re: [SIP] Proxy Routing Logic
>>
>>
>>
>>
> >For the first case, couldn't this be the result of a roaming
> >UA using source
> >routing to get the
> >initial INVITE to its home domain proxy to do the actual
> >routing (perhaps the
> >user has
> >originating call features registered that they wish to use);
> >in which case I
> >would expect the
> >behaviour in 2 to take place.

>In this case, I don't think the roaming user would construct the URI in this
>fashion. Rather, it would use a Route header to accomplish this task.

Is that a recommended behavior - using Route versus maddr? That may be a better
way but it is not intuitive at all. Check any available SIP User Agent - I have
yet to see one that would convert typed in (or clicked on) RURI of
sip:[email-masked];maddr=local.proxy.com into RURI=sip:local.proxy.com,
... Route=sip:[email-masked] (pardon my syntax) which is what is
implied (I think). Another problem occurs when [email-masked]
registered at the proxy with contact of
'sip:[email-masked];maddr=local.proxy.com'. If the Proxy gets INVITE
with RURI of [email-masked] then it will find the appropriate contact
and proxy the message to RURI=sip:local.proxy.com, ...
Route=sip:[email-masked]. But according to Table5 of the spec the Proxy
is not even allowed to insert Route header on its own.

>
>That aside, there is an important issue here. When using a local outbound
>proxy, you most definitely do NOT want to set the maddr parameter in the
>request URI to point to that proxy. This is confusing, since you would want
>the URL to have the maddr parameter outside of the context of the request
>URI.
>Specifically, lets say I want to have a URL in a web page that causes people
>to call me through some local proxy. That URL in the web page would look
>like:
>
>sip:[email-masked];maddr=local.proxy.com
>
>This URI would not be inserted directly into the request URI, however. That
>maddr needs to be stripped.

Although it is a valid proposal I think there are some cases where the maddr
cannot be stripped. If my UAC cannot resolve domain names and maddr is
local.proxy.com and my outbound proxy is always 111.111.111.111 I do not know if
111.111.111.111 and local.proxy.com are the same so I would have to include
maddr in the RURI. So the point is proxy can receive a request where maddr of
RURI actually does match proxy itself and there has to be a way/rule to process
such a message properly. The whole subject of this thread is to make this
processing not confusing.

>
>So, I propose we add some text to the spec somewhere along these lines: "The
>maddr parameter should be present in the Request URI only if the server the
>request is sent to is not the one in the maddr parameter.". Probably this
>can be better phrased.

That is certainly a good idea but again, Proxy must be able to deal with RURI
that would not follow that rule.

>-Jonathan R.
regards, Jacek Grabiec
sip:[email-masked]

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