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Nancy Greene wrote:
> Thanks for the answer, but I'd like to know why the RFC is written the way it
> is.
>
> What if there is an intermediate SIP proxy between the target in the
> Request-URI and the proxy trying to reach it? That intermediate SIP proxy
> does not allow traffic on the port mentioned in the Request-URI, so the
> request fails to reach the target. This does not seem right. Shouldn't the
> RFC at the very least require a retry at the port that the intermediate proxy
> expects traffic on?
I think you must be missing something fundamental.
I think the following describes what you are asking about:
C ----- P ------ S
where the message from C is something like:
INVITE sip:f...@s.com:12345
Route: sip:p.com
...
In the above case C would be sending the request to P using the result
of SRV lookup on p.com. The port number in the R-URI is irrelevant to
how the request is sent to P.
Once the request reaches P, it will then use the R-URI to decide where
to forward the request. So then the port number 12345 will be relevant.
Thanks,
Paul
> Nancy
>
> -----Original Message-----
> From: Paul Kyzivat [mailto:pkyzi...@cisco.com]
> Sent: March-15-10 9:08 AM
> To: Nancy Greene
> Cc: sipc...@ietf.org
> Subject: Re: [sipcore] RFC 3263 - why require use port in Request-URI?
>
> Nancy,
>
> Questions such as this should be brought to
> <sip-implementors@lists.cs.columbia.edu>.
>
> To answer your question...
>
> The port from the URI is to be used *if* it is present in the URI.
> (Would you prefer to *ignore* it?)
>
> If the the port is *not* present in the URI, then the port is obtained from
> DNS via the SRV query. That is explained further on in the same section of
> the document.
>
> Thanks,
> Paul
>
>
> Nancy Greene wrote:
>> I have a question on section 4.2 of RFC 3263:
>>
>> Why is it that the port of the Request-URI is required to be used for an
>> intermediate proxy? Is the issue that it is not known whether the next hop
>> proxy is intermediate or is the actual destination in the Request-URI?
>>
>> If so shouldn't there at least be a procedure described to use the port from
>> DNS instead of the one in the Request-URI if sending to the one in the
>> Request-URI fails?
>>
>> Section 4.2 from RFC 3263 (locating SIP servers):
>>
>> If the TARGET was not a numeric IP address, but a port is present
>> in the URI, the client performs an A or AAAA record lookup of the
>> domain name. The result will be a list of IP addresses, each of which
>> can be contacted at the specific port from the URI and transport
>> protocol determined previously.
>>
>> Nancy
>>
>>
>> _______________________________________________
>> sipcore mailing list
>> sipc...@ietf.org
>> https://www.ietf.org/mailman/listinfo/sipcore
>>
>
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