[Freeswitch-users] RTP traffic on LAn

Fri Jan 11 16:13:11 MSK 2013

You need to understand that because FS is a B2BUA by default there are two
separate media sessions endpoint1->fs and fs->endpoint2. They negotiate
completely separately, and FS just copies media across during a
bridge. That means endpoint2 never sees the SDP of endpoint1... unless you
bypass_media.

If you set bypass_media=true then they will see the actual SDP of the other
endpoint (forwarded by FS). Reading RFC5245.it looks like that would be
enough for it to work. But you'll still want to know *when* to bypass_media
since it might not work in all situations especially when NAT is involved
and when one endpoints doesn't support STUN/ICE.

In a NAT situation you'll still be reliant on your router's SIP ALG being
disabled - the endpoints are setting all their candidate addresses in the
SDP and if the router were to modify them then that could break everything.

In the case bypass_media_after_bridge=true might still allow RFC2833 DTMF
for IVR menus hosted on FS before it leaves the media path. I'm not clear
on how well ICE would work with the media renegotiation, but presumably it
would work as well as the initial negotation. Chris, relying on SIP INFO
isn't necessarily a good idea - not all endpoints would send it for a
start, and it only ever made it as far as a IETF draft that was dropped...
although plenty of people have implemented it it never became an actual
standard. In particular there are timing issues with it if the packets
arrive out of order due to network jitter, since it lacks the timestamping
that RFC2833 provides. Far better to remain in the media path for IVR and
then to bow out. You're going to be wanting to play prompts to the user
during the IVR anyway.

-Steve

On 11 January 2013 12:47, Raimund Sacherer
<raimund.sacherer at logitravel.com>wrote:

> Hi,
>
> I have not looked much into this, but I was under the impression that it's
> a client-side thing, as I read it the SDP contains various IP's for the
> media, the public (which the phone seeks out via STUN) and the private, the
> other phone tries to connect to each of those and the first answer it get's
> it uses for the media path, as a LAN should answer always faster than a
> WAN, it should create the mediapath directly between the two devices,
> therefore FS will not see the media and interacts only with the signaling.
>
> This is how I have interpreted ICE.
>
> Now, if it does not work this way I appologize, up to now I did not have
> any use for ICE as all our remote offices are small and they do normally
> not call each other and in our main offices our PBX's are (still) internal
> ...
>
> Best,
> Rai
>
> ------------------------------
> *From: *"Steven Ayre" <steveayre at gmail.com>
> *To: *"FreeSWITCH Users Help" <freeswitch-users at lists.freeswitch.org>
> *Sent: *Viernes, 11 de Enero 2013 13:34:15
> *Subject: *Re: [Freeswitch-users] RTP traffic on LAn
>
>
> Unfortunately FS does not (as yet) support it. At least not AFAIK.
> It also would require that both endpoints support it too, and not all do.
>
> In any case since FS is a B2BUA not a SIP proxy the endpoints are
> negotiating with FS not the other endpoint - so you're still going to want
> to detect that you want to (try to) bypass_media.
>
> -Steve
>
>
>
>
>
> On 11 January 2013 11:19, Raimund Sacherer <
> raimund.sacherer at logitravel.com> wrote:
>
>> Hi,
>>
>> isn't there allready a protocol that does that? ICE?
>>
>> this is an excerpt from the SNOM wiki page (we have about 280 snom phones
>> in action):
>>
>> --- snip ---
>> ICE DESCRIPTION  Choose whether or not you want to use ICE (Interactive
>> Connectivity Establishment). ICE optimizes the media path. This would be
>> the case, for example, when two phones in the same network are calling each
>> other via a long media path through other, external networks. With ICE, the
>> short media path in the same network would be chosen, which will presumably
>> have better quality than the long one. Sometimes this feature will stop you
>> from being able to make calls. When this occurs, switch it off.
>> --- snip ---
>>
>> Link here: http://wiki.snom.com/Settings/user_ice
>>
>> Here seems to be more information, check "Probing Media Path":
>> http://wiki.snom.com/Networking/NAT
>>
>> Best,
>>
>> Raimund
>>
>> ------------------------------
>> *From: *"Chris B. Ware" <chrisbware at yahoo.it>
>> *To: *freeswitch-users at lists.freeswitch.org
>> *Sent: *Viernes, 11 de Enero 2013 10:30:52
>> *Subject: *[Freeswitch-users] RTP traffic on LAn
>>
>>
>> Hi all,
>>
>> I'm trying to find a way to let RTP traffic between two phones,
>> registered to a public Freeswitch, on the same LAN, remain local.
>> Usually phones are natted behind an ADSL router and using two RTP streams
>> to speack each other (because, for example, are on different
>> rooms on the same office) consume a lot of bandwidth.
>>
>> Is there anyone who has found a solution to this problem?
>>
>> I was thinking on using SIP INFO for sending DTMF (in case customer have
>> to use some phone features activated via phone), using
>> private IP (no STUN on phones) and keeping FS out of RTP streaming.
>>
>> Any help will be appreciated.
>>
>> Chris
>>
>>
>>
>> _________________________________________________________________________
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>>
>> 
>> 
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>> --
>> [image: Logitravel.com] <http://www.logitravel.com/> Raimund Sacherer
>> *Sistemas*Agencia de Viajes Online
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>
> _________________________________________________________________________
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> http://www.freeswitchsolutions.com
>
> 
> 
>
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> --
> [image: Logitravel.com] <http://www.logitravel.com/> Raimund Sacherer
> *Sistemas*Agencia de Viajes Online
> www.logitravel.com Edificio Logitravel, Parcela 3B (Parc Bit)
> Ctra. Palma - Valldemossa km 7,4 | 07121 Palma de Mallorca
> Tel 902 366 847  |  Fax 971 213 495 Síguenos en:[image: Facebook de
> Logitravel] <http://www.facebook.com/logitravel> [image: Twitter de
> Logitravel] <http://twitter.com/logitravel>[image: Blog de Logitravel]<http://www.logitravel.com/bloglogi/> [image:
> Logitravel en Youtube] <http://www.youtube.com/logitravel>[image:
> Logitravel en Foursquare] <https://es.foursquare.com/logitravel> Descarga
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> información de carácter confidencial exclusivamente dirigida a su
> destinatario. Queda prohibida su divulgación, copia o distribución a
> terceros sin la previa autorización escrita de LOGITRAVEL S.L.. En caso de
> haber recibido este correo electrónico por error, se ruega notifíquese
> inmediatamente esta circunstancia mediante reenvío a la dirección
> electrónica del remitente. Al mismo tiempo LA EMPRESA le recuerda que sus
> datos forman o formarán parte de un fichero registrado como CLIENTES con
> número de inscripción 2070610043 en la Agencia General de Protección de
> Datos, propiedad de la empresa LOGITRAVEL, con domicilio en Edificio
> Logitravel, Ctra. Palma - Valldemosa km 7,4, Parc Bit, Palma de Mallorca.
> Usted tiene derecho de acceso, oposición, rectificación y cancelación a
> estos datos que deberá ejercer mediante escrito a la dirección
> anteriormente citada.
>
> _________________________________________________________________________
> Professional FreeSWITCH Consulting Services:
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> http://www.freeswitchsolutions.com
>
> 
> 
>
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