Subject: Re: SIP: CANCEL request/2xx-response to INVITE

From: "Christian Jansson" <[email-masked]>
Date: Wed, 2 Jun 1999 11:05:56 +0200

Is this the correct behavior of handling CANCEL and BYE messages?
If not, what is wrong?

1)
UAC                        UAS
|----------INVITE--------->|
|----------CANCEL--------->| The CANCEL does terminate the session = no BYE
needed to be sent from UAC
|<--------CANCEL 200-------|
|                          |

2)
UAC                        UAS
|----------INVITE--------->|
|---CANCEL--\  /-INV. 200--|
|            \/            |
|            /\            |
|<----------/  \---------->| The CANCEL does not terminate the session
|<--------CANCEL 200-------|
|------------BYE---------->|
|<---------BYE 200---------|
|                          |

3)
UAC                        UAS
|----------INVITE--------->|
|-----------BYE----------->| The BYE does terminate the session
|<--------BYE 200----------|
|                          |

/Christian Jansson

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From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 02 Jun 1999 09:42:36 -0400

> |<--------BYE 200----------|

These are all correct. One note on the last, though. Since BYE is a
totally separate transaction, and in your example would be without
routing headers (since it is sent before the 200 OK to the INVITE is
received), it may not reach the same set of people who got the INVITE.
This could happen in very dynamic routing situations, like some kind of
ACD. Also, if the BYE does fail somewhere, or isn't received by one of
the original INVITE recipients, you'll never know. The BYE responses
will be merged, as other responses to INVITE. To be safer, I think
you're better off sticking with case 2, waiting for a 200 and sending a
BYE with the routing headers to make sure it goes to the right place.

-Jonathan R.

-- 
Jonathan D. Rosenberg                       Lucent Technologies
Member of Technical Staff                   101 Crawfords Corner Rd.
High Speed Networks Research                Holmdel, NJ 07733
FAX:   (732) 834-5379                       Rm. 4C-526
EMAIL: [email-masked]
URL: http://www.cs.columbia.edu/~jdrosen

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From: "Rex Coldren" <[email-masked]>
Date: Wed, 02 Jun 1999 08:15:35 -0700

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