[cisco-voip] DTMF interworking on CUBE - asymmetric payloads

[Ed Leatherman]

Thanks Daniel, that helps a lot in understanding the feature. I'm curious
if CUBE will also translate digits to KPML in this case if the leg to CUCM
has that negotiated. Wish I had a lab built out for this :)



On Mon, Jul 18, 2016 at 4:22 PM, Daniel Pagan <dpagan at fidelus.com> wrote:

> Ed:
>
>
>
> I specifically worked with the dynamic payload option for a few cases that
> came my way. Based on my findings, when a dynamic payload type (such as
> 100/101/etc.) is received by CUBE, it will check if the next-hop dial-peer
> has the asymmetric payload feature enabled and, if it is, will pass the
> received payload type through to the next call-leg. Take a look at my
> screen shot below. This was taken from some old notes where AT&T was the
> customer’s carrier.
>
>
>
>
>
> The call flow above shows two call-legs, and *the arrows represent an
> offer/answer exchange*.
>
>
>
> With asymmetric payload enabled on both call legs, the 100 offer from ATT
> is passed to CUCM despite 101 being the default PT for NTE. In the SDP
> answer from CUCM, we’re getting PT 101 -- since asymmetry is enabled on the
> DP to ATT in this call flow, we pass the 101 through to ATT despite having
> received PT 100.
>
>
>
> This results in asymmetry on our negotiated PT for each call-leg.
>
>
>
> *Let’s change it up a bit… A second example.*
>
> If asymmetry was disabled on the dial-peer to CUCM but enabled to ATT, we
> would receive 100 PT from ATT, send 101 to CUCM, receive 101 from CUCM, and
> send 101 to ATT. The resulting PTs would be symmetrical between CUBE and
> CUCM, but asymmetrical between CUBE and ATT.
>
>
>
> See screenshot below for a third example:
>
>
>
>
>
> This example shows asymmetric payload disabled on both call-legs using the
> same call flow. CUBE receives PT of 100 from ATT -- the outbound dialpeer
> has asymmetry disabled, so it transmits the PT specified for that dial-peer
> (default 101 or any hardcoded dynamic PT) to CUCM. We then receive 101 from
> CUCM and, since our inbound dial-peer has asymmetry disabled, CUBE sends
> 100 to match the original PT it received. Asymmetry is disabled so CUBE is
> not passing the received dynamic PT through to the next-hop dial-peer - we
> have symmetry on both call legs for our NTE PT.
>
>
>
> Note that CUBE has no issues receiving one dynamic PT for NTE and sending
> another (ex: receiving PT 100 and transmitting 101 for RTP-NTE) on the same
> call leg.
>
>
>
> Hope this helps
>
>
>
> - Dan
>
> --------end attach---------
>
>
>
> *From:* cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] *On Behalf
> Of *Ed Leatherman
> *Sent:* Monday, July 18, 2016 3:10 PM
> *To:* Cisco VOIP <cisco-voip at puck.nether.net>
> *Subject:* [cisco-voip] DTMF interworking on CUBE - asymmetric payloads
>
>
>
> I'm trying to get my head wrapped around some DTMF interworking
>  features...
>
>
>
> I have this setup:
>
>
>
> UCM ------ CUBE ------- 3rd party system
>
>
>
> For both call legs through CUBE I'm advertising kpml and rtp-nte for
> dtmf-relay
>
>
>
> The 3rd party sometimes sends me rtp payload type 101 for nte's, and no
> kpml, and things work (as a bonus I observed CUBE correctly interworking
> the nte's from the pbx into KPML, so uccx didn't break).
>
> Sometimes they send type 98 and no kpml, and things don't work.
>
>
>
> I'm trying to understand what is happening and what feature should fix it
> (without breaking other things)
>
>
>
> Assumption:
>
> "dtmf-relay rtp-nte kpml" is telling CUBE to offer/accept rtp type 101
> only for nte. I observe that CUBE negotiates KPML only for the associated
> call leg back to UCM and doesn't bother with rtp-nte, so its just like any
> other codec that CUBE doesn't care about.
>
>
>
> So.. if third party system ONLY sent me dtmf-relay with payload type 98,
> could I just set the rtp payload type for this to 98 on the inbound dial
> peer? would CUBE then correctly switch these up to 101 headed back to UCM?
>
>
>
> How can I (or can I at all) make this work in my particular case were I
> could receive both?
>
> I see "asymmetric payload dtmf" thrown about as a possible solution, but
> I'm having trouble understanding what it actually does. It sounds like it
> passes these payload types through CUBE, so UCM could be getting rtp
> payload type 98 - it knows what to do with it? It seems like then CUBE
> wouldn't be able to translate things to KPML this way...
>
>
>
> I'm reading
> http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/cube/configuration/cube-book/voi-dymc-payld-dtmf.html
> but I guess I'm just not drinking enough coffee today (or too much) and I'm
> not getting what exactly this command does.
>
>
>
> Anyone know how that asymmeteric command works?
>
>
>
> --
>
> Ed Leatherman
>



-- 
Ed Leatherman
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