Iñaki Baz Castillo wrote:
> El Wednesday 20 August 2008 16:29:22 Jagan Mohan escribió:
>> Hi All,
>>
>> I would like to know whether a B2BUA can insert the SIP Methods it
>> support in the Allow header, when a SIP call is made between two UAs
>> through the B2BUA.
>>
>> If yes, then I have query on the following call flow:
>>
>> UAC ---- B2BUA ---- UAS.
>>
>> Say, UAC and B2BUA support UPDATE method. And UAS does not support
>> UPDATE method.
>>
>> If an UPDATE request for codec change is received from UAC within an
>> early dialog, then what should be the Error response from B2BUA? Here,
>> B2BUA is aware that UAS does not support UPDATE method from the reliable
>> provisional response. So, it should not forward the UPDATE request to the
>> UAS.
>
> Shouldn't B2BUA reply "405 Method Not Allowed" ot the UAC when it sends the
> UPDATE?
If the method is not allowed, then 405 is the appropriate response.
In that case, the 405 is required to contain an Allow header listing
which methods *are* allowed. It is especially disconcerting if that
Allow contains UPDATE when it is the UPDATE method that is being
rejected. Even if the Allow in the UPDATE doesn't include UPDATE, it is
disconcerting if a previous Allow stated that it was allowed.
While disconcerting, it isn't technically incorrect to change your mind
about what is allowed. The scoping of Allow is not at all well defined.
So it might be that you *did* support UPDATE when you sent an Allow
mentioning it, but stopped supporting it later. But its silly to provoke
this problem by claiming you allow something when you don't.
Thanks,
Paul
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