Re: Proxy acting as UAS -- CANCEL scenario

 

While sending cancel itself, will specify the transaction
that to be
canceled.(suppose consider Invite transaction have to be
canceled.cancel
will sent with same transaction ID as of INvite). If cancel
is successfully
reached UAS.then UAS will reply with 200 ok.Then will send
487 Request
Treminated for the same.

 

     UAC                            UAS

> Invite                          Invite>    

                ------------

>cancel                           cancel>

<200 ok                            200 ok<

<487 Req Ter                      <487 Req Treminated

 

    Note : cancel should be sent before final response.if
not cancel has no
effect.

Please correct me if wrong....

 

 

Regards,

Nithya krishna.

 

 

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-----Original Message-----
From: sip-implementors-bouncescs.columbia.edu
[mailto:sip-implementors-bouncescs.columbia.edu] On Behalf
Of Prabhakaran,
Manikantan
Sent: Tuesday, June 05, 2007 12:10 PM
To: Iliff, Tina; sip-implementorscs.columbia.edu;
sippingietf.org;
Avasarala Ranjit-A20990
Subject: Re: [Sip-implementors] [Sipping] Proxy acting as
UAS -- CANCEL
scenario

 

Hi,

    Receiving a 200 OK for the CANCEL only ensures the
CANCEL

Transaction has terminated. But what about the INVITE
Transaction ? For

the INVITE transaction to be terminated the proxy should
responsd with a

487 (Requested Terminated) response.

 

 

-Regards

Mani.

 

________________________________

 

From: Avasarala Ranjit-A20990 [mailto:ranjitmotorola.com] 

Sent: Tuesday, June 05, 2007 11:59 AM

To: Iliff, Tina; sip-implementorscs.columbia.edu;
sippingietf.org

Subject: RE: [Sipping] Proxy acting as UAS -- CANCEL
scenario

Importance: High

 

 

Hi

 

In ur scenarios, SBC cannot receive 100 Trying, but it
should receive

180 Ringing from TUA. Ok say SBC does not receive 180, the
SBC will

retransmit INVITE for certain times with timer T1).. 

 

Now say OUA sends CANCEL to proxy and proxy sends 200 OK to
OUA - so

here the transaction ends with respect to OUA.

Now Proxy forwards CANCEL to SBC. and 

SBC should send 200 OK to proxy. 

 

Finally SBC can send CANCEL to TUA 

 

why should proxy send 487 to OUA?  I don't think it is
required

amd why should SBC send 408 for the INVITE that does not
exist anymore?

 

 

 

Regards 

Ranjit 

 

 

 

 

________________________________

 

From: Iliff, Tina [mailto:tina.iliffverizonbusiness.com] 

Sent: Tuesday, June 05, 2007 2:08 AM

To: sip-implementorscs.columbia.edu; sippingietf.org

Subject: [Sipping] Proxy acting as UAS -- CANCEL scenario

 

 

 

All, 

 

RFC3261 Section 16 states the following regarding Proxy
Behavior: 

 

Being a proxy is a logical role for a SIP element. When a
request

arrives, an element that can play the role of a proxy first
decides

if it needs to respond to the request on its own. For
instance, the

request may be malformed or the element may need credentials
from the

client before acting as a proxy. The element MAY respond
with any

appropriate error code. When responding directly to a
request, the

element is playing the role of a UAS and MUST behave as
described in

Section 8.2.

 

Please consider the following call flow scenario: 

 

OUA sends INVITE to Proxy 

Proxy sends 100 Trying to OUA 

Proxy routes INVITE to SBC 

SBC sends 100 Trying to Proxy 

SBC routes INVITE to TUA 

SBC does not receive 100 Trying from TUA and retransmits
INVITE several

times   

OUA sends CANCEL to Proxy 

Proxy responds to CANCEL with 200OK 

Proxy routes CANCEL to SBC 

SBC does not route CANCEL to TUA 

A CANCEL timer on Proxy pops and Proxy sends 487 for INVITE
request to

OUA 

Several seconds elapse and Timer B pops on the SBC and it
sends a 408

back to the Proxy for the INVITE request 

The proxy does not ACK the 408 response; therefore, the SBC
retransmits

the 408 for 64*T1 seconds 

 

Note:  The SBC is acting as a proxy and not a B2BUA 

 

Question:  Is the proxy behaving correctly by sending the
487 response

to the INVITE request on its own? 

 

Regards, 

 

Tina Iliff 

 

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