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[Sipping] 回复： RE: early-session & p-early-media /////Re: PRACK: Doesnon-200 response cease re-transmission ofreliable 18x?
hi，
To early session, there is only one dialog, where new early session SDP comes, old one is replaced according to rfc3264.You donot need to terminate early dialog by 199 or something else.
I think early session and forking early media both have some disadvantages.
Can you list "the other things" you mentioned to make forking early media easier than early session?
Regards,
Eric
原信息
主题： RE: [Sipping] early-session & p-early-media /////Re: PRACK: Doesnon-200 response cease re-transmission ofreliable 18x?
发件人： "Christer Holmberg" <christer.holmberg at ericsson.com>
日期： 2009/04/06 13:41
Hi,
>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.
You have an excellent tool which can help you with that: 199 :)
When you are done with your early-media, you send 199 in order to
terminate that early dialog. The UAC can then "switch" to the other
dialog.
This of course requires support of 199 in the UAC, but I think it's
easier to implement that (it is useful also for other things) than
early-session.
Regards,
Christer
________________________________
From: sipping-bounces at ietf.org [mailto:sipping-bounces at ietf.org]
On Behalf Of wang.libo at zte.com.cn
Sent: Monday, April 06, 2009 11:05 AM
To: Paul Kyzivat (pkyzivat)
Cc: sipping-bounces at ietf.org; eric.wangxr at gmail.com;
sipping at ietf.org; Brett Tate
Subject: [Sipping] 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 at zte.com.cn 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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