[SR-Users] [Sems] Solutions to missing BYEs, accounting for them

[Raphael Coeffic]

On 23.04.10 11:58, Alex Balashov wrote:
> On 04/23/2010 05:18 AM, Raphael Coeffic wrote:
>> On 23.04.10 09:51, Alex Balashov wrote:
>>> On 04/22/2010 10:01 AM, Stefan Sayer wrote:
>>> ]
>>>> clean? I am not so sure any more, trying to hack something together to
>>>> see where this gets. Is there a clean and simple method to do 
>>>> re-invite
>>>> from the b2bua, which catches all the possibilities (changed session
>>>> etc)?
>>>>
>>>> e.g., one possibility, reinvite with last SDP from the other side
>>>
>>> From my understanding of SSTs, this is the correct approach (last
>>> known SDP). This has the advantage of not breaking the changes of real
>>> re-INVITEs that actually happened.
>>>
>> Sending an empty INVITE has the appeal of working with either side (no
>> matter with which you begin). With the other, you might have to remember
>> which side initiated the last INVITE or UPDATE transaction, and send the
>> last positive SDP answer to this side as a re-INVITE. Or am I missing
>> something?
>>
>> However, it might happen that the one of the ends does not support
>> receiving empty INVITEs... (less probable today).
>
> I thought about empty INVITEs first, but my--admittedly naive--reading 
> of the specs suggests that many endpoints would take the absence of an 
> SDP offer/answer in a sequential request or reply within the same 
> session to mean that the media elements of the session have been 
> rescinded.
>
RFC 3261 says on the topic (section 14.1):
   "Of course, a UAC MAY send a re-INVITE with no session description, 
in which case the first
    reliable non-failure response to the re-INVITE will contain the offer
    (in this specification, that is a 2xx response)."

> If I'm wrong, that would certainly make all this a lot easier.
>
So I guess you MAY be wrong ;-)

Another question is: what would be the expire value you would like to 
use for SST? This could dramatically change the requirements in terms of 
load. Where you thinking about 15 minutes? (sending a re-INVITE approx. 
every 7 minutes?) Or do you need a precise billing (maybe minute based?) ?

Cheers,
Raphael.