Cisco 7942 - T302/Interdigit Time Out

[czerewacz]

Dears:

I`m testing the SIP firmware SIP42.9-0-3S on the Cisco 7942G. Also I did not configure a SIP Dial rule so by default KPML is enabled (

https://supportforums.cisco.com/docs/DOC-21748)

The issue is that when I dial for example, this dial pattern: 9XXXXXXXX on the SIP phone, it does take more time to start making the call that a SCCP phone.

It seems that the T302 in Service Parameters - Call Manager it{s only affecting the SCCP phones. Now is configured to 4 seconds but from the SIP phone it takes 15 seconds.

(Even if I dial #, does not terminate the time out)

Any ideas?

Thanks!!

Marcelo Czerewacz

[will.alvord]

I apologize for not knowing the answer to your question, but I am curious about something you posted.  Dialing # only signals CUCM to not wait for the T302 timer to expire if your route pattern is configured with a # right?  ...or is that functionality native to CUCM??  As to your issue, the only thing off the top of my head is that it sounds like you've got an overlapping dialplan.  On your testing to compare calls from a SIP phone vs SCCP phone, are you using identical css?

[czerewacz]

The # pattern only signals CUCM to not wait for the T302 timer to expire if your route pattern is configured with a #. In the SCCP phone works.

SCCP and SIP phone have identical CSS. Weird, no?

[clileikis · Accepted solution]

Hi Marcelo,

Although it isn't an exact match to your behavior there are some bugs regarding T302/SIP loads (CSCsz40616 - No inter-digit timeout when making second call, CSCtc01407 : CM 7.1.2 - T302 fails when dialing translation pattern from SIP phone).  Any reason why you are using the SIP load?  I'd recommend using SCCP as there are lots of issues with the earlier SIP loads.

HTH,

Chris

[czerewacz]

Thanks Clileikis:

In the

Related Bug Information

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCtc01407)

CM 7.1.2 - T302 fails when dialing translation pattern from SIP phone

Symptom: T302 timer does not pop when dialing translation pattern with wildcard from SIP phones on CM 7.1.2.  Conditions: T302 timer fails to pop for SIP phones on translation patterns but works for route patterns.  SCCP phones work as expected.  Workaround: Use SCCP phone load.

This is my case and I have CUCM 8.3. It is fixed in 8.5.... We will see.

[Harmit Singh]

Hi Marcelo,

Just to clarify - the versions given in the defect are not CUCM versions, they are phoneload versions. Defect ID CSCtc01407 is a duplicate of CSCsz40616, which means the code fix for both issues is the same. The phone firmware version where the issue was fixed is 9.0.1SR1. The firmware you mentioned is 9-0-3S which would have a fix for the above defects already. Hence, it is not a good match for your issue.

The solution is to avoid using overlapping dialplan based on the explanation I gave earlier.

HTH.

Regards,

Harmit.

[Harmit Singh]

Hi Marcelo,

Let me take a stab at this. I had run into something similar 2-3 years ago and did some testing in the lab to see what the difference in behavior is between SIP and SCCP endpoints when dialing a pattern / DN (both overlapping and unique). Here are some important points to keep in mind:

1>  SCCP endpoints use enbloc mechanism while the Cisco SIP endpoints use overlap sending mechanism.

2>  Enbloc mechanism collects all the digits and then sends them to the Call Agent. Overlap mechanism sends the called digits one by one.

3>  The Cisco SIP endpoints, by default, use the overlap sending / receiving mechanism because of the Key Press Stimulus Protocol (KPML). This mechanism provides for "digit reporting" or "DTMF reporting".

4>  When the CUCM sees “Allow-Events: kpml” in the INVITE message coming from the Cisco SIP endpoint, it also switches over to the overlap receiving mode. You would ideally see “|setEndpointsDtmfCaps: KPML Supported.|” in the traces suggesting the same.

5>  KPML uses the SUBSCRIBE and NOTIFY methods of SIP. The CUCM would respond back with a TRYING to the Cisco SIP endpoint and perform a digit analysis.

6>  If the digits that came in the INVITE message match a dialing pattern and there is no overlapping, it will route the call immediately. If there is an overlapping dialing pattern, you will see the CUCM send a SUBSCRIBE message to the Cisco SIP endpoint. This message contains the KPML request and also specifies the following timers “

7>  This is purely because of the way overlap sending and receiving works. It will always look for the longest match in the dialplan. In enbloc dialing, it will always look for the closest match in the dialplan. Hence the delay.

Hope this helps.

Regards,

Harmit.

[czerewacz]

Thanks for the clarification! Regards

[Harmit Singh]

Hi Marcelo,

Glad I could help :-) Please rate helpful posts and mark as answered if it takes care of the question you had.

Regards,

Harmit.