Re: early-session & p-early-media /////Re: PRACK: Does non-200 response cease re-transmission ofreliable 18x?

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Eirc,
 
IMHO, many implementations do NOT support early-session,
In theory multiple early dialogs must be supported by UAC,
so we can use one early dialog for early-media and another one for final media.
It looks like a forking or logical forking.
 
But in real world, many device does not support forking or
it can only support forking in terms of signaling,not forking to establish multiple media sessions.
 
Regards,
-Rockson
 
 


From: sipping-bounces@xxxxxxxx [mailto:sipping-bounces@xxxxxxxx] On Behalf Of wang.libo@xxxxxxxxxx
Sent: Monday, April 06, 2009 11:05 AM
To: Paul Kyzivat (pkyzivat)
Cc: sipping-bounces@xxxxxxxx; eric.wangxr@xxxxxxxxx; sipping@xxxxxxxx; Brett Tate
Subject: early-session & p-early-media /////Re: PRACK: Does non-200 response cease re-transmission ofreliable 18x?


Hi,

 We introduce early-session to our system as it can solve media clip.
There are two ways to avoid media clip, early-session and forking p-early-media.
To support them both need all equipments (except proxies) update,
the problems you mentioned exist in both methods.

Do you mean, forking early media is better than early-session?

Regards,
Eric







 From the beginning I found the early-session technique "interesting".
The problem I have with it is believing that people will attempt to
implement it, and if they do, that they will implement it correctly.

Given the amount of trouble that people seem to have implementing the
full o/a mechanism correctly, who likely is it that they will get it
right when trying to simultaneously manage two independent o/a
negotiations, most likely with the o/a role swapped between them, and
all multiplexed over the same invite. Its possible, but I'd like to hear
about it being tested at sipit.

                Thanks,
                Paul

wang.libo@xxxxxxxxxx wrote:
>
> Hi,
>
> Brett Tate has listed some.
> Also:
>  o. Services can be supplied with fewer messages.It helps lighten the
> servers stress.
>  o. You can recognize the session for the tone easily.
>  o. It's useful for services such as CF(call forward),in which case there
> may be several early diologs.
>
> Regards,
> Eric
>
>
>
>
>  > > Do you find some advantage to it over simply using early media
>  > > with a different to-tag?
>  >
>  > It allows the early media session and answered media session to be
>  > negotiated prior to INVITE 2xx.  The main benefit is to reduce
>  > clipping upon INVITE 2xx if forking has occurred and all UAS
>  > actually support early-session.
>  >
>  > More specifically, UAS may assume only answered media will be sent
>  > to the port for answer; thus it could quickly start rendering
>  > answered media prior to receiving INVITE 2xx.  UAC can allocate
>  > other ports for early media; or it can refuse or hold early media
>  > without it subsequently delaying answered media (by requiring
>  > another offer/answer exchange).
>  >
>  > Works good in theory if all user-agents support it.  I have no idea
>  > how well it works in the real world. :)
>  >
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