Re: [sipcore] IETF#101: Session-timer slides

[Paul Kyzivat <[e-mail]>]

Christer,

On 3/19/18 5:50 AM, Christer Holmberg wrote:
> Hi,
> 
> As some people are going to participate remotely, before I upload the 
> slides I have put the current version on GitHub.
> 
> https://github.com/cdh4u/draft-sessiontimer-race/blob/master/IETF101_SIPCORE_SESSION-RACE.pdf
> 
> We will discuss the technical stuff during the meeting, but if there is 
> something you think could be clarified then please let me know.

I went and reviewed the draft and rfc again, and I still think the fix 
in your 3.1 (to section 7.2 of 4028) is over broad.

Consider a case where a session timer has already been established 
between Alice and Bob. We are mid-dialog and there are no transactions 
in progress. Now Alice decides she wants to disable the session timer.

How can she do that? Following 4028, she does that by sending an INVITE 
or UPDATE with no Session-Expires. The response to that also has no 
Session-Expires, and then session timer is cancelled.

But with your revision, because the request did not contain 
Session-Expires, the response does not cancel the session timer.

To avoid the problem, the behavior of leaving a s-t running after 
receiving a response without Session-Expires must be limited to UPDATE 
transactions embedded within INVITE transactions.

	Thanks,
	Paul