Re: [Sipping] Rollback issue: a proposal

[Gonzalo Camarillo <[e-mail]>]

Hi,

> Comments for 
> http://www.ietf.org/internet-drafts/draft-camarillo-sipping-reinvite-00.txt
>  
> 1. I think that it is BCP level. And the solution can be effective by 
> restricting Non-2xx when Offer/Answer pair has been exchanged.

yes, we will need to decide on the status (BCP vs. PS vs. Informational)
at some point.

> 2. Your proposal considered legacy UAS. But currently, the situation is 
> legacy UAC with legacy UAS. And it is the original issue.

the draft describes the behavior of a new UAC that faces a legacy UAS,
which is the interesting situation. Other situations are not interesting
because a legacy UAC will be able to do the right thing when facing a
new UAS and if we have a legacy UAC against a legacy UAS, there is
nothing we can do because they were implemented some time ago and are
already out there.

> 3. "In order to undo changes that were already executed, the UAS uses a new
>    offer/answer exchange or a target refresh request."
> If the new offer/answer exchange need precondition, the other side can 
> reject it with 504. then the modification(undo changes) may not be done 
> by UPDATE/200OK. And Re-INVITE can not be used here(for the pending 
> original Re-INVITE).

The whole point is that the UAS should not send an error response. It
should send a 200 (OK) to the re-INVITE and then use traditional
mechanisms (i.e., UPDATEs or re-INVITEs) to modify the session if needed.


> Comments for 
> http://www.ietf.org/internet-drafts/draft-camarillo-sipping-precons-00.txt
>  
> 1. "However, the fact that the UAs can start using the new media 
> parameters does not mean that they need to start using them 
> immediately." Yes.

we agree on this one, then.

> More than one Offer/Answer pais before Precondition Ok, and Caller can 
> be answerer for some and Callee for the others. Then the two sides may 
> waiting peer using new parameters
> after Precondition OK. It may be deadlock.

No, they will not be a deadlock because the UAS is in charge of starting
using the new parameters and of initiating a new offer/answer exchange.

Thanks for your comments,

Gonzalo