This isn't really the best place to discuss the logic behind IMS
designs. While I have some knowledge of that, I'm not actively involved,
and I find much of what is there to be strange.
Good Luck
Paul
Dushyant Dhalia wrote:
> Paul Kyzivat wrote:
>>
>>
>> Dushyant Dhalia wrote:
>>> In 3GPP specs, related to IMS procedure, it's written that P-CSCF
>>> sends the SUBSCRIBE request to I-CSCF which in turns finds the
>>> address of S-CSCF through Cx query. My question is why can't P-CSCF
>>> send the SUBSCRIBE directly to S-CSCF using Service-Route it received
>>> during Registration.
>>
>> A SUBSCRIBE to *what*? The Service-Route gets to the UAC's own S-CSCF.
>> That's only useful if the UAC is subscribing to its own AOR. That
>> might be useful for reg event subscriptions, and a few other odds and
>> ends, but not in general.
> Dushyant - For subscription to reg event P-CSCF is subscribing to UAC's
> AoR. In any case; service-route is treated as master data for routeing
> decisions of UAC i.e. for every request originated by UAC which contains
> route header; P-CSCf validates the route header to see if it matches
> with the service route header stored with P-CSCF.
> I don't see any harm in using service route by P-CSCF, atleast for
> subscription to reg event, but it will do some good i.e., it will reduce
> load on I-CSCF as well as HSS. This aspect can be standardised so that
> it doesn't remain a proprietary implementation.
> Please comment on the above opinion.
>> In any case, the use of the Service-Route is the responsibility of the
>> UAC, not the P-CSCF. If the UAC has used it, then there will be a
>> Route header in the request, which will influence with the P-CSCF does
>> with the request.
>>
>> Paul
>
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