RE: [Sip] Open Issue #7: CANCEL for non-INVITE

> -----Original Message-----
> From: Shail Bhatnagar [mailto:shbhatna@cisco.com]
> Sent: Thursday, August 23, 2001 3:28 PM
> To: Kim Liu
> Cc: Jonathan Rosenberg; 'sip@ietf.org'
> Subject: Re: [Sip] Open Issue #7: CANCEL for non-INVITE
> 
> 
> Kim Liu wrote:
> 
> My take is that although CANCEL for non-INVITE is academic,
> it should be allowed. Main reason is to not make special checks
> in the state machine about original method and this CANCEL.

This argument would be true if the cost of the CANCEL for non-INVITE was
otherwise nil. But, thats not true. What happens if the CANCEL actually
beats the server to sending the final response? Now, you have to actually
cancel it. How does one CANCEL a SUBSCRIBE? A NOTIFY? An OPTIONS? Each
method would need special code. 

Furthermore, since its usage is always a race condition, an entity that
sends CANCEL would always need to handle the case where the cancel works and
doesn't work. Thus, its extra work to do this.

Note that I have stipulted that for backwards compatibility, if you get a
CANCEL for non-INVITE, you still respond to it, but otherwise do nothing. In
that sense, its "allowed", but we explicitly define it as a no-op.

-Jonathan R.
---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
jdrosen@dynamicsoft.com                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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