[cisco-voip] Cisco IOS Enhanced Software Media Termination Point, DTMF and SIP

[Keith Klevenski]

I tried rtp-nte in the past and it did not work.  In the CUCM 7.x SRDN I read that you should not use nte on h323 gateways because CM doesn't support it on h323 gateways:  http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/7x/media.html#wp1056938 I will certainly try it again as it was a few weeks ago when I was messing with it.  

All the voip dial-peers to CM are configured with h245-signal so I'm not sure how the gateway and Asterisk could have matching DTMF capabilities, but either they do or an MTP is being invoked and I am not detecting it.  Even internal SCCP calls to Asterisk should be invoking an MTP for DTMF right?  SCCP device calls Asterisk, media is up, SCCP device presses a digit and DTMF is sent OOB to CM, CM invokes MTP, MTP sends RFC2833 digit to Asterisk.  However I don't see any MTP's being invoked when I do this and it works fine and all devices only have access to an IOS SW MTP in which I can see no activity with a 'deb sccp packet' which should definitely give me something if it is being invoked.

The combination of SIP, g729, MTPs and DTMF is boggling to me.  Does the fact that all calls are g729 a factor?  All devices are in a g729 region.  I read in CM help that 'To configure G.79 codecs for use with a SIP trunk, you must use a hardware MTP or transcoder that supports the G.79 codec' however I do not need one as it is working just fine wihtout it internally.  I check MTP required, but one doesn't get invoked that I can tell yet internal DTMF works and all devices only have access to one device which is the IOS SW MTP.  Which doesn't show any sign of being invoked...

I wish they would just buy Unity.  :P

Thanks for your help Ryan.  I'll play around with it some more and report back.

-k


-----Original Message-----
From: Ryan Ratliff [mailto:rratliff at cisco.com] 
Sent: Wednesday, September 09, 2009 4:32 PM
To: Keith Klevenski
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] Cisco IOS Enhanced Software Media Termination Point, DTMF and SIP

Why require the MTP at all?  You can configure more than 1 dtmf type  
on the dial-peer going to CUCM.  Add rtp-nte to the dtmf payload types  
(in addition to h245-alpha) and you shouldn't need an MTP at all.   
Since you mentioned h245-alpha I assume your gateway is H.323.

The CUCM software MTP can also convert from oob to 2833 DTMF so it may  
be using that one as well.  The only difference in the IOS one is the  
codec support.  If CUCM really isn't invoking an MTP then it's because  
the gateway and Asterix have matching dtmf capabilities.

One thing you'll want to check is the payloadType for the 2833 DTMF.   
IOS gateways don't support dynamic payload types currently and I think  
use 101 by default.  If Asterix is using something else you'll want to  
change it on the dial-peer with the command 'rtp payload-type nte  
<97-127>' where the number matches whatever Asterix is using.  It may  
be that both sides think they can do 2833 but the gateway is sending a  
payloadType Asterix isn't looking for.

-Ryan

On Sep 9, 2009, at 5:02 PM, Keith Klevenski wrote:

All,

Trying to get DTMF to pass to an Asterisk VM server from the PSTN with  
no love.  Using H323 PSTN gateways running 12.4(24)T1, ISDN PRI's,  
CUCM 7.02, with a SIP trunk to Asterisk.  This is all g729 as well.  I  
can dial into Asterisk internally and DTMF works fine, but I can't get  
it to pass DTMF from the PSTN.  The call goes though to Asterisk fine  
from the PSTN, but doesn't seem to be passing DTMF.

sccp ccm group 1
  associate ccm 1 priority 1
  associate ccm 2 priority 2
  associate profile 1 register softmtp2
!
dspfarm profile 1 mtp
  codec g711ulaw
  maximum sessions software 50
  associate application SCCP

sh sccp

SCCP Admin State: UP
Gateway Local Interface: GigabitEthernet0/0.101
         IPv4 Address: 10.1.101.3
         Port Number: 2000
IP Precedence: 5
User Masked Codec list: None
Call Manager: 10.1.101.11, Port Number: 2000
                 Priority: 1, Version: 7.0, Identifier: 1
Call Manager: 10.1.101.10, Port Number: 2000
                 Priority: 2, Version: 7.0, Identifier: 2

MTP Oper State: ACTIVE - Cause Code: NONE
Active Call Manager: 10.1.101.11, Port Number: 2000
TCP Link Status: CONNECTED, Profile Identifier: 1
Reported Max Streams: 100, Reported Max OOS Streams: 0
Supported Codec: g711ulaw, Maximum Packetization Period: 30
Supported Codec: rfc2833 dtmf, Maximum Packetization Period: 30
Supported Codec: rfc2833 pass-thru, Maximum Packetization Period: 30
Supported Codec: inband-dtmf to rfc2833 conversion, Maximum  
Packetization Period: 30

 From what I understand the IOS software MTP should be what I need to  
allow RFC2833 and h245-signal (tried h245-alphanumeric as well) to  
communicate, even with g729.  The IOS SW MTP is registered and  
configured, but DTMF is still not being passed.  The IOS software MTP  
is in the MRG/MRGL for all device pools for all devices.  I've even  
put all the other media resources in a temp MRG to ensure only the  
software MTP is able to be invoked (it's all g729 satellite sccp  
analog phones so no moh/annunciator or anything).  I do a 'deb sccp  
packet' on the gateway with the IOS MTP, but I get nothing when  
sending DTMF.  In RTM I don't see any MTP resources being used on the  
IOS MTP.  I've had the SIP trunk configured with MTP required checked  
and unchecked (although CM should still dynamically allocate and MTP  
for DTMF if needed even if it is not checked), RFC2833 set as the DTMF  
type and G729/G729a as the codec on the trunk.  It seems like the MTP  
is not being invoked at all, but I'm not sure why or how to absolutely  
prove that it is or isn't.  So far I don't see any attempts being made  
to invoke it by looking at RTM or 'deb sccp packet'. I don't have  
access to the Asterisk box (and wouldn't know what to do if I did),  
but it works fine internally so I'm pretty sure the problem is with  
two DTFM types needing an MTP.

Any suggestions or insight?

Thanks!

Keith



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