[Freeswitch-users] Multiple 183 SDP Change Codecs - allowed?

Tue Jul 3 22:48:57 MSD 2012

If we only we had absolutes that were that simple...

The default setting in FreeSWITCH when forking (parallel or serial) is
to consider the first bridge (leg) that returns media (of any sort) as
successful.  This FreeSWITCH behavior can be changed.  Many other
implementations behave differently.

In SIP (especially with proxies) this isn't an absolute and several
other scenarios are still valid.  A leg can return 183 w/SDP and then
a 4xx/5xx/6xx, which should then defer to another leg (or pass the
error, or branch further, etc).  Various scenarios are perfectly valid
per the specs.  It's up to the implementor/application to decide which
behavior is preferred.

On Tue, Jul 3, 2012 at 1:50 PM, Steven Ayre <steveayre at gmail.com> wrote:
> 18x messages are supposed to make the call unreroutable since they indicate
> the call has been successful on that route.
>
> -Steve
>
>
>
> On 3 July 2012 16:56, Avi Marcus <avi at avimarcus.net> wrote:
>>
>> They said the 1st carrier rejected it so the second 183 is from a second
>> carrier.. but yes, the first carrier shouldn't be sending a 183...
>> Anyway -- if you please look at the pcap from the first email, the log I
>> posted a link to later, or the past two emails -- you'll see FS originally
>> offers both PCMU and PCMA in the initial invite.
>>
>> I think we need Anthony to chime in here... he knows the RFC stuff!
>>
>> -Avi
>>
>>
>>
>> On Tue, Jul 3, 2012 at 6:22 PM, Kristian Kielhofner <kris at kriskinc.com>
>> wrote:
>>>
>>> That's pretty nasty of voxbeam to do...  Considering they return the
>>> first 183 less than one second after the initial INVITE I'd say it's
>>> very likely they're providing false ringback and/or FAS (false answer
>>> supervision).  Meanwhile the actual ringback comes over two seconds
>>> later with PCMA.  That's shady and if I were you I'd switch carriers
>>> just on principle.
>>>
>>> However, as I said before they're not doing anything that's not
>>> allowed by the various specifications although FAS is considered by
>>> many as fraud.
>>>
>>> What are your codec settings like?  Perhaps FS is rejecting PCMA
>>> because you're not allowing it?
>>>
>>> On Tue, Jul 3, 2012 at 9:38 AM, Avi Marcus <avi at avimarcus.net> wrote:
>>> > If so.. which I think is not.. is this a bug then in FS?
>>> >
>>> > http://pastebin.freeswitch.org/19423
>>> > You see from the first SDP that PCMU and PCMA were both options.
>>> > Then for the next SDP FreeSWITCH was only considering PCMU which was
>>> > the one
>>> > that got chosen by the first SDP.
>>> >
>>> > Voxbeam claims it's not their fault.. is it?
>>> >
>>> > -Avi
>>> >
>>> >
>>> >
>>> > On Tue, Jul 3, 2012 at 4:26 PM, Kristian Kielhofner <kris at kriskinc.com>
>>> > wrote:
>>> >>
>>> >> Avi,
>>> >>
>>> >>   Multiple 18x responses that change the SDP are allowed.  I can't
>>> >> find the specific document text now but as a random guy on the
>>> >> internet (for whatever that's worth) I'm certain it is allowed.
>>> >>
>>> >>   A re-INVITE can't be sent from either side until the dialog has been
>>> >> established (200+ACK).  In a case where the UAC (caller) would like to
>>> >> update the session before it is established method UPDATE must be
>>> >> used.
>>> >>
>>> >> On Tue, Jul 3, 2012 at 1:04 AM, Avi Marcus <avi at avimarcus.net> wrote:
>>> >> > Are multiple 183s from the endpoint that changes the SDP allowed?
>>> >> > I'm
>>> >> > under
>>> >> > the impression this is broken, similar to
>>> >> > http://wiki.freeswitch.org/wiki/NDLB#NDLB-allow-nondup-sdp
>>> >> > ... which is why when the codec changes, FS freaks out and cancels
>>> >> > the
>>> >> > call
>>> >> > because of codec negotiation error.
>>> >> > Does that NDLB flag allow this, too?
>>> >> >
>>> >> > First has: audio 10116 RTP/AVP 0 101 13
>>> >> > Second has:  audio 49020 RTP/AVP 8 13 101
>>> >> > PCAP: http://ge.tt/7MpyBwJ
>>> >> >
>>> >> > Can someone point me to the specific RFC so I can tell the supplier
>>> >> > to
>>> >> > fix
>>> >> > it?
>>> >> > And just curious.. what would make this allowed? A re-INVITE..?
>>> >> >
>>> >> > -Avi
>>> >> >
>>> >> >
>>> >> >
>>> >> > _________________________________________________________________________
>>> >> > Professional FreeSWITCH Consulting Services:
>>> >> > consulting at freeswitch.org
>>> >> > http://www.freeswitchsolutions.com
>>> >> >
>>> >> > 
>>> >> > 
>>> >> >
>>> >> > Official FreeSWITCH Sites
>>> >> > http://www.freeswitch.org
>>> >> > http://wiki.freeswitch.org
>>> >> > http://www.cluecon.com
>>> >> >
>>> >> > Join Us At ClueCon - Aug 7-9, 2012
>>> >> >
>>> >> > FreeSWITCH-users mailing list
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>>> >> >
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>>> >> >
>>> >>
>>> >>
>>> >>
>>> >> --
>>> >> Kristian Kielhofner
>>> >>
>>> >>
>>> >> _________________________________________________________________________
>>> >> Professional FreeSWITCH Consulting Services:
>>> >> consulting at freeswitch.org
>>> >> http://www.freeswitchsolutions.com
>>> >>
>>> >> 
>>> >> 
>>> >>
>>> >> Official FreeSWITCH Sites
>>> >> http://www.freeswitch.org
>>> >> http://wiki.freeswitch.org
>>> >> http://www.cluecon.com
>>> >>
>>> >> Join Us At ClueCon - Aug 7-9, 2012
>>> >>
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>>> >>
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>>> >
>>> >
>>> >
>>> >
>>> > _________________________________________________________________________
>>> > Professional FreeSWITCH Consulting Services:
>>> > consulting at freeswitch.org
>>> > http://www.freeswitchsolutions.com
>>> >
>>> > 
>>> > 
>>> >
>>> > Official FreeSWITCH Sites
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>>> > http://wiki.freeswitch.org
>>> > http://www.cluecon.com
>>> >
>>> > Join Us At ClueCon - Aug 7-9, 2012
>>> >
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>>>
>>>
>>>
>>> --
>>> Kristian Kielhofner
>>>
>>> _________________________________________________________________________
>>> Professional FreeSWITCH Consulting Services:
>>> consulting at freeswitch.org
>>> http://www.freeswitchsolutions.com
>>>
>>> 
>>> 
>>>
>>> Official FreeSWITCH Sites
>>> http://www.freeswitch.org
>>> http://wiki.freeswitch.org
>>> http://www.cluecon.com
>>>
>>> Join Us At ClueCon - Aug 7-9, 2012
>>>
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>>
>>
>>
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
>> consulting at freeswitch.org
>> http://www.freeswitchsolutions.com
>>
>> 
>> 
>>
>> Official FreeSWITCH Sites
>> http://www.freeswitch.org
>> http://wiki.freeswitch.org
>> http://www.cluecon.com
>>
>> Join Us At ClueCon - Aug 7-9, 2012
>>
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>
>
> _________________________________________________________________________
> Professional FreeSWITCH Consulting Services:
> consulting at freeswitch.org
> http://www.freeswitchsolutions.com
>
> 
> 
>
> Official FreeSWITCH Sites
> http://www.freeswitch.org
> http://wiki.freeswitch.org
> http://www.cluecon.com
>
> Join Us At ClueCon - Aug 7-9, 2012
>
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-- 
Kristian Kielhofner