Re: [sipcore] I-D Action: draft-ietf-sipcore-sessiontimer-race-02.txt

Hi Christer,
Thank you for Updating the draft.
We see this work as important since we have still problems with implementations of the session timer and a lot of discussion with different SP and Vendors.

What we realized is that the definition of the  "Initial Session Refresh Request" is not clear.
You may interpret it out of the whole RFC but not from the definition. 
The definition states:
Initial Session Refresh Request: The first session refresh request
      sent with a particular Call-ID value.

This does not state if it is the Initial INVITE requesting the session timer or if it is the first INVITE refreshing the session?

The Session Refresh Request is defined as:
Session Refresh Request: An INVITE or UPDATE request processed
      according to the rules of this specification.  If the request
      generates a 2xx response, the session expiration is increased to
      the current time plus the session interval obtained from the
      response. 

It states that the session expiration is increased. So what is now increased? Is it also the initial INVITE response with the first session expire value.

>From my point of view it would help when we change the definition section to:
Initial Session Refresh Request: The first session refresh request
      sent with a particular Call-ID value. i.e. initial INVITE sending at minimum a "supported timer" which is answered by an 200 OK with a negotiated session timer.

Question is if is only my view or does others have the same view?

Thank you and Best Regards

Roland

> -----Ursprüngliche Nachricht-----
> Von: sipcore [mailto:sipcore-bounces@ietf.org] Im Auftrag von internet-
> drafts@ietf.org
> Gesendet: Donnerstag, 30. August 2018 12:38
> An: i-d-announce@ietf.org
> Cc: sipcore@ietf.org
> Betreff: [sipcore] I-D Action: draft-ietf-sipcore-sessiontimer-race-02.txt
> 
> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Session Initiation Protocol Core WG of the
> IETF.
> 
>         Title           : Session Initiation Protocol (SIP) Session Timer Glare Handling
>         Author          : Christer Holmberg
> 	Filename        : draft-ietf-sipcore-sessiontimer-race-02.txt
> 	Pages           : 7
> 	Date            : 2018-08-30
> 
> Abstract:
>    This document updates RFC 4028, by clarifying the procedures for
>    negotiating usage of the Session Initiation Protocol (SIP) session
>    timer mechansim, in order to avoid a race condition where both
>    endpoints trigger simultaneous negotiations.
> 
> 
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-sipcore-sessiontimer-race/
> 
> There are also htmlized versions available at:
> https://tools.ietf.org/html/draft-ietf-sipcore-sessiontimer-race-02
> https://datatracker.ietf.org/doc/html/draft-ietf-sipcore-sessiontimer-race-
> 02
> 
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-sipcore-sessiontimer-race-02
> 
> 
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
> 
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
> 
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