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[Linphone-developers] Re: [Linphone-users] not ACKing retransmitted 200'

From: Aymeric Moizard
Subject: [Linphone-developers] Re: [Linphone-users] not ACKing retransmitted 200's.
Date: Mon, 27 Oct 2003 13:45:53 +0100 (CET)

Hi troy!

On Fri, 24 Oct 2003, Troy Cauble wrote:

> Greetings,
> Using linphone-0.11.0 with osip-0.9.7, I see the following:
>   When a 200 is received in response to an INVITE, it is ACKed.
>   But if the ACK is lost, the far end (not a linphone) repeats the 200.
>   Linphone never ACKs these repeated 200s.
> In osip/fsm/ict_fsm.c, ict_rcv_2xx() has two callbacks
> to functions in linphone/osipua/src/ict_callbacks.c:
>   1) ict_2xx_received() handles the 200 and sends the ACK, and
>   2) ict_kill_transaction() frees the transaction
> It appears that either ict_rcv_2xx() should not callback
> ict_kill_transaction(), or ict_kill_transaction() should
> not actually remove the transaction, so that subsequent
> 200's can be matched.  Can someone suggest which one?
> If someone clarifies which library should be responsible,
> I can write the code.

In the SIP rfc, only ONE 200ok is handled by the finite state
machine. Th other must be handled by what it called the "TU" (which
is the application above osip: linphone). A patch exist for this
and osip & linphone can be compiled to handle retransmissions
of ACK when a 2xx retranmission is received.

BUT: a real UA should be able to understand that a new 200ok can
come from a new User Agent and create a new SIP dialog. Linphone
don't handle those new 200ok...


> Also, how long should it guard against repeat 200's?
> A few seconds?  The life of the dialog?
> Also, I see OSIP_RETRANSMISSION ifdefs in linphone
> for repeating the 200ok msgs until an ACK is received.
> But it appears that some osip portions are missing
> from 0.9.7.  What's the status of this?
>    I find references to these functions
>    (osip_start_200ok_retransmissions(), etc.) in osip2.
>    Can linphone-0.11.0 (& it's osipua library) be used with osip2 ?
>    I thought osip2 was not compatible and you had to wait for an
>    eXosip version of linphone.  Or maybe there are cvs entries
>    between osip 0.9.7 and 2.0.0 that contain these??
> Please, no eXosip suggestions.  I need to get a pre-eXosip
> linphone working.
> Thanks,
> -troy
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