I have noticed the bis says proxy only forwards 2xx responses. But I still
have the doubt: If the UAC does not enable multiple dialogs, then what
should
it do on the arrival of multiple 200 responses?
-Lu Wei
"A Venkatraman"
<[EMAIL PROTECTED]> To: Wei BJ
Lu/China/IBM@IBMCN, "McMurry, Kathleen"
Sent by: <[EMAIL PROTECTED]>
[EMAIL PROTECTED] cc:
<[EMAIL PROTECTED]>
lumbia.edu Subject: RE:
[Sip-implementors] How does forking proxy handle To Tag
in er rorresponse selection?
2001-11-16 09:20
Please respond to "A
Venkatraman"
a. How does a UAC enable multiple dialogs?
b. The proxy only forwards all 200 class final responses. See line 2345 of
bis-05 pdf.
Also, see line 2423 which specifies that a proxy should send CANCEL on
all legs that sent a provisonal but no final response.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Wei BJ Lu
Sent: Thursday, November 15, 2001 6:58 PM
To: McMurry, Kathleen
Cc: [EMAIL PROTECTED]
Subject: RE: [Sip-implementors] How does forking proxy handle To Tag in
er rorresponse selection?
I have some doubt on "the proxy should select the best response from the
ones it has
received and send it to the OUA". I think it it not always true. To my
understanding,
the behaviour of a forking proxy on receiving final responses should be
different
under two circumstances:
a. If the UAC does not enable multiple dialogs(call-legs), the proxy
should forward
the best final response upstream and cancel all the unfinished forking
branches.
b. If the UAC enable multiple dialogs, the proxy should forward all the
final
responses to the UAC. Since on the UAC's side, different To tag means
different dialog.
When 180 with To tag u1 and u2 comes, the UAC will create two dialogs. If
the proxy
only forward 486(this tag u1) to the UAC, the UAC will only terminate one
dialog and
the other dialog will keep ringing.
-Lu Wei
"McMurry, Kathleen"
<[EMAIL PROTECTED]> To: "'Bob
Penfield'" <[EMAIL PROTECTED]>, A Venkatraman
Sent by:
<[EMAIL PROTECTED]>, [EMAIL PROTECTED]
[EMAIL PROTECTED] cc:
lumbia.edu Subject: RE:
[Sip-implementors] How does forking proxy handle To Tag
in er ror response
selection?
2001-11-16 04:02
Please respond to "McMurry,
Kathleen"
>-----Original Message-----
>From: Bob Penfield [mailto:[EMAIL PROTECTED]]
>Sent: Thursday, November 15, 2001 1:19 PM
>To: McMurry, Kathleen; A Venkatraman; [EMAIL PROTECTED]
>Subject: Re: [Sip-implementors] How does forking proxy handle To Tag in
>er ror response selection?
>>
>> >> Suppose a proxy forks a request from UAC to uas1, uas2,
>> >> and each returns a 18x, with tag u1 and u2 respectively, which are
>> >> forwarded, as is, to UAC,
>> >> and then uas1 returns a 486 with tag u1 and uas2 returns 500 with tag
u2
>> >> Proxy picks best response 486 to return to UAC.
>> >>
>> >> Question:
>> >> Will the TO tag in the 486 reponse be u1? Or, will there be no TO
tag.
>> >> Is this implementation specific or does the protocol specify this
>> >anywhere?
>> >>
>> >Based on section 16.6 on bis-05, the tag received in the response is
>> >preserved when the selected response is forwarded to the UAC.
Therefore,
it
>> >would be u1 for your example. The proxy is not allowed to modify the To
>> >header in the forwarded response.
>>
>> A 2xx response is the only type of response that is truly "forwarded" by
>the
>> proxy. Any non-2xx response is really hop by hop. Therefore, in your
>> example, the proxy will add its own To tag when it responds to the UAC.
>> Niether u1 or u2 would be used.
>Section 16.6 of bis-05 explicitly forbids the proxy from adding its own
tag.
>It is not a UAS in this case. The proxy is suppose to select the best
>response from the ones it has received and forward that response to the
UAC.
I agree that the proxy should select the best response from the ones it has
received and send it to the OUA. I also agree that the spec. does not
clarify the two different cases well.
In the case of a 2xx response, the proxy forwards the response to the OUA
leaving the To tag alone. For a non-2xx response however, the To tag is
used to match the corresponding ACK for each hop. Therefore, when the
non-2xx response is received by the proxy, it should ACK the UAS with the
To
tag that was added by the UAS. But when the proxy sends the response to
the
UAC, the proxy should use a To tag that it generates so that it can
determine that the corresponding ACK is meant for the proxy and should not
be forwarded.
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
