On 3/1/13 4:27 AM, Neel Neelakantan wrote:
> Ramesh,
>
> See inline.
>
>> -----Original Message-----
>> From: [email protected] [mailto:sip-
>> [email protected]] On Behalf Of Ramesh Babu
>> Kuppili
>> Sent: Wednesday, February 27, 2013 12:42 AM
>> To: Paul Kyzivat; [email protected]
>> Subject: Re: [Sip-implementors] change in tag field in To header
>>
>> Paul,
>>
>> Sorry. I mistyped UAC. I meant to say UAC. Not UAS. Corrected text:
>>
>> Thanks for the response. Is there any way to know how many forks were
>> made by a proxy. My application is VoIP. I need to provide some kind of
>> error tone when the UAC determines that the call cannot be landed on any
>> of the forks. Ideally, I would like to know the total number of forks made
>> by
>> the proxy and provide error tone to the voice user when all the forks
>> responsed with error final responsed.
>>
> [Neel]
> It is not possible to know how many forks the proxy (or subsequent downstream
> proxy) made. Typically a proxy when forks, it collects all the responses and
> send only one (See section 16 of RFC 3261)).
There is no way to *know* how many forks there were.
You can use certain information to guess. This may work better in some
deployments than others. Namely:
1) You can note the total number of to-tags you see in responses. You
may get 1xx responses with a number of different to-tags, as you have
seen, as well as a final response that may be from a to-tag already seen
or a different one. This will fail to count forks that fail without
sending a 1xx.
2) You may look for a History-Info header in the responses. If found, it
may be analyzed to count the number of forks. This of course will only
work if History-Info is used by the systems involved. (History-Info is
specified by RFC4244, and there is a nearly complete revision called
draft-ietf-sipcore-rfc4244bis-11.
Thanks,
Paul
>> Thanks again for your time.
>>
>> - ramesh
>>
>> -----Original Message-----
>> From: [email protected] [mailto:sip-
>> [email protected]] On Behalf Of Ramesh Babu
>> Kuppili
>> Sent: Wednesday, February 27, 2013 10:51 AM
>> To: Paul Kyzivat; [email protected]
>> Subject: Re: [Sip-implementors] change in tag field in To header
>>
>> Paul,
>>
>> Thanks for the response. Is there any way to know how many forks were
>> made by a proxy. My application is VoIP. I need to provide some kind of
>> error tone when the UAS determines that the call cannot be landed on any
>> of the forks. Ideally, I would like to know the total number of forks made
>> by
>> the proxy and provide error tone to the voice user when all the forks
>> responsed with error final responsed.
>>
>> Thanks again for your time.
>>
>> - ramesh
>>
>> -----Original Message-----
>> From: [email protected] [mailto:sip-
>> [email protected]] On Behalf Of Paul Kyzivat
>> Sent: Wednesday, February 27, 2013 3:50 AM
>> To: [email protected]
>> Subject: Re: [Sip-implementors] change in tag field in To header
>>
>> On 2/27/13 12:38 AM, Ramesh Babu Kuppili wrote:
>>> Hello,
>>>
>>> I am having a problem with the To tag in the incoming "603 Declined" from
>> UAS.
>>>
>>> 1. Outgoing INVITE
>>> - no tag in the To header.
>>> 2. Incoming "183 Session Progress"
>>> - To tag -
>> tag=h7g4Esbg_p65547t1361882364m374065c90075s1_4069438959-13.
>> Incoming "603 Declined"
>>> - To tag -
>>> tag=h7g4Esbg_p65547t1361882364m374065c90075s1_4069388685-
>> 1940037509
>>> Can the To tag change from "183 Session Progress" to "603 Declined". How
>> do the UAS handle this?
>>
>> Yes.
>>
>> This is consistent with the request having been forked by a proxy.
>> The 183 came from one fork. Then the 603 came from a different fork.
>> Once this has happened, you generally will get no further response from the
>> first fork.
>>
>> Good Luck,
>> Paul
>>
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