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List:       sip-implementors
Subject:    Re: [Sip-implementors] What shold do ?
From:       "Medhavi Bhatia" <mbhatia () nextone ! com>
Date:       2002-08-26 15:34:17
Message-ID: 009401c24d16$2ed7f780$1fe4b4cc () laptopeng3
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In scenario (1), where the proxy will forward the CANCEL to B,
and return a 200 OK for CANCEL to A. B will return a 200 OK
for the CANCEL to the proxy. The 200 OK for the INVITE will
be forwarded by the proxy to A, which who will then determine
that his CANCEL did not work, and generate a BYE.

In scenario (3), the proxy would have forwarded the 200 OK for
the INVITE to A. The CANCEL will be forwarded statelessly by the
proxy. The processing on A is similar to scenario (1).

Scenario (2) is a mix of (1) and (3), as either the 200 OK or the
INVITE will be processed by the proxy first.

-Medhavi.

----- Original Message -----
From: "feng zhang" <y01317@njupt.edu.cn>
To: <sip-implementors@cs.columbia.edu>
Sent: Monday, August 26, 2002 10:49 AM
Subject: [Sip-implementors] What shold do ?


Hi All,

   Look at the scenarios below:

1)

   User A              Stateful Proxy               User B
     |                       |                         |
     |-----1.INVITE--------->|                         |
     |                       |------2.INVITE---------->|
     |<----3. 100------------|                         |
     |                       |<------4. 100------------|
     |                       |                         |
     |-----5.CANCEL--------->|           <--200 OK-----|

  NOTE that , Stateful Proxy has received "CANCEL", at the same time

User B's "200 OK" is on the line, and Proxy has not received it. For

stateful proxy has received User A's "CANCEL", so it forwords "CANCEL"

request to User B. But once it sends "CANCEL", User B's "200 OK"

arrives. NOW, what should the proxy do? and what should User B do?

User B has just sent "200 OK", then he/she will receive "CANCEL"

2)

User A              Stateful Proxy               User B
     |                       |                         |
     |-----1.INVITE--------->|                         |
     |                       |------2.INVITE---------->|
     |<----3. 100------------|                         |
     |                       |<------4. 100------------|
     |                       |                         |
     |-----5.CANCEL--------->|<-------------200 OK-----|

Here, AT THE SAME TIME Stateful Proxy receives User A's "CANCEL" AND User
B's "200 OK",

what should Proxy do then?

3)

User A              Stateful Proxy               User B
     |                       |                         |
     |-----1.INVITE--------->|                         |
     |                       |------2.INVITE---------->|
     |<----3. 100------------|                         |
     |                       |<------4. 100------------|
     |                       |                         |
     |-----5.CANCEL--->      |<-------------200 OK-----|

Here, User A's "CANCEL" is on the line, while stateful proxy has recieved

User B's 200 OK, proxy should forward this 200 OK, but when it has forwarded

the 200 OK, it receives User A's "CANCEL", then , what should proxy do?

And User A will receive User B's 200 OK after the "CANCEL" request,

what should User A do ?

Thanks a lot to give me an answer1

Best Regards.




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