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Q&A from Session 5: CUCM Media Resources-Transcoder, MTP OOB, In-Band DTMF & MoH




This is the Q&A from "Technical Services Virtual Boot Camp - CUCM Media Resources - Transcoder, MTP OOB, In- Band DTMF & MoH and Trace Snippets, Session 5".

Q: Can we use external box for unicast MOH (music on hold)?

A: MOH is unicast by default. Unless the Multicast Checkbox is checked at all three places which is MRG/AUDIO source/ MOH server­.

Q: ­Where can we use software MTP (best practices)­?

A: Where ever we  use supplementary services such as hold resume etc G711ulaw and mitigating DTMF mismatches as well.  MTP are of three types primarily:

  • 1. Software MTP - IPVMSA using software drivers off the CUCM server­.
  • 2. IOS based Software MTP - MTP on the IOS with software sessions this uses CPU cycles off the IOS.
  • 3. IOS based Hardware MTP which uses PVDM and actual ASIC resources  IOS based resources can only support a single codec­.

Q: ­Can we use third party MOH server for unicast? ­

A: ­There is no third party MOH server which is supported.  We cannot add another MOH server in call manager.  If you are referring to the flash streaming MOH, then that is configured by configuring telephony service and uses the AFWB process on the IOS.

Q: ­what will happen if different MRGL is associated with device pool and Phone?­

A: ­The MRGL on the DEVICE POOL and the PHONE if have different contents, get merged together and call manager process of Media resources lookup list consolidates it together, in the hierarchy of device to device pool approach ­. This is similar to a consolidation of partitions happens when line and device CSS are different.  here the lookup list for the MEDIA manager consolidates in that way.

Q: ­If 2nd mrgl list gets exhausted, default will be used?­

A: ­Yes that is correct, the default would be used once all is exhausted, consider this as a accumulation of three MRGL device > device pool > default list­.

Q: ­Are there any specific Criteria or Route On which the ANN tune plays?­

A: ­ANN is not always used in ringbacks, but when you get announcements like " your call cannot be completed as dialed" etc and areas where ringback or reorder tone needs to be generated, there is when the ann gets invoked.  it needs to be in any mrg.

A ringback most of the times gets played by the flash memory of the phone itself.  the SCCP message to the phone which the CUCM sends instructs it s to play the ringback rather than invoking ringback always from ANN. 

Q: ­In region, if the maximum bandwidth is 64kbps, can it use G729, because it is only 8 KBPS which is less that 64kbps­?

A: ­We need to understand that bitrate(region setting) is different than Bandwidth ( locations setting).  What region setting only tells that the maximum which is supported is g711ulaw­. Next come in the setting of audio codec preference list introduced in later version which can govern that if available on either side which codec is preferred.­

Q: ­I mean between Default and Test can it use G729?­

A: ­There are various pointers which govern which codec would be used­. There is even a service parameter which is the default inter and intra-region codec which comes into play incase there is no specific audio bitrate selected between the two test regions.

­Q: ­If i have two different cluster, suppose user A is in cluster A & user B in cluster B. USER A place user B on hold. does moh plays from cluster B MOH server­?

A: ­USER A shares the audio source ID and the MRG/MRGL on phone B selects the MOH server to stream the MOH provided the file exists on its server­‑ and there can be various situations where this behaviour would change and depends on case to case scenario­‑.

Q: ­Incase, you have a call coming from Default region to a phone in Test region and default region phone prefers G729, do they negotiate on G729?­

A: ­Two endpoints whose region settings of bit rate specifically set to g729 would govern only the maximum bit rate allowed as g729, but thats not it. Each endpoints also specifies the codec it supports, and these media caps shared with Media Exchange layer ­‑­then decides whether or not there is a codec mismatch and invoke any codec mismatch mitigating device accordingly.­‑ Also do not that the audio codec preference list also plays a huge part in negotiating a codec in a pool of matching caps­‑ if you are familiar with the concept of SETS, its the intersection of the capabilities of the two endpoints and that forms pool of matching codec­‑.

Q: ­What should be the settings for customized MOH? ­

A: this document highlights in details of a custom MOH to upload:

Q: ­Is it possible to load user recorded file for hold msg?­

A: Any file which conforms to the requirement of above document can be used as a MOH audio: source.­ 

Q: ­Are hardware MTP and Transcoder are same?­

A: ­NO they are not both same. A hardware MTP supports a single codec and mitigates packetization.  however A Transcoder is of two types primary. One of the type is regular transcoder which is G711ulaw to any codec conversion other is universal transcoder which is any codec to any codec and needs PVDM3 explicitly.­‑

Q: ­Earlier HW MTP will support G711 codec only . If i want to convert the 20 ms to 30 ms for G729 codec still i can use hardware mtp?­

A: ­Same flavour of G729 with different packetization can be mitigated through hardware MTP­‑.

Q: ­How many calls a single PVDM3 supports­?

A: ­It depends if its a PVDMX64 PVDMX32 etc. its best to use the DSP calculator added later in the slides.

Q: ­MTP is mainly for SIP trunks only?­

A: ­Not at all. MTP usages was shared in one the slides, we can touch the MTP slide again if requested. There are a host of reasons why a MTP is required.  ­‑­To summarize, supplementary services(hold-transfer-conf initiation, dtmf mismatches, faststart, earlyoffer(depends), etc­‑.

Q: ­Does OOB messages between CM & UCCX is part of JTAPI messages­?

A: ­You are absolutely correct.  between CUCM and UCCX the relaying of the DTMF is always OOB and is a JTAPI message.­

Q: Does analog phones(VG224) also supported out of band and inband dtmf?­

A: ­An analog phone VG224 supports inband and out of band pulse of 8-12 pps­.

Q: If users press 1 ,then RTP payload type is 101,what if users press 4?­­

A: ­Payload type does not have anything to do with the type of digit pressed.­

Q: ­What is the app name , for the SIP , H.323 message analysis­?

A: ­The tool is notepad ++ its a freeware­.

Q: ­What is this tool?­

A: ­Tool alternatives are Jedit, wingrep, translator x.­

Q: ­Can a cube be a MGCP gateway or H.323?­

A: ­Having MGCP and h323 on the same gateways is not supported, however it is possible to have a gateway with E1's/T1's, and also have a ITSP. but again its not a supported environment. ­Also to add to it a common misconception about cube is that its only sip, basically when both inbound and outbound dial-peers are voip its more of a cube arrangement and it can have h323 on both ends and you would be having a ITSP­.

Q: How did they got these things in notepad?­

A: ­This is not the microsoft notepad, it's a tool used not just by tac but also programmers to code better and is a freeware.­

Q: ­Means it is safe to put some in default. Can we say this?­

A: ­Any media resource (ANN, MOH, MTP,) which is not in any  MRG is part of the default list.­

Q: I haven’t attended first 3 sessions. is there any web link where i can get the recording of the web sessions?­


Q: ­Can we register two CUCM clusters to a single voice gateway for example MGCP..suppose we already running one cluster and it is working with one e1/t1 and now we are going to configure another cucm cluster and here can we register it with another e1/t1 slot­?

A: ­This is not supported. A Single Voice gateway which has the MGCP process running, you would be expected to bind the MGCP interface.  Think about having a single media/signalling interface catering to two different ccm-managers .can that be possible?  not quite.­ The best way to get a deep dive on this is is understanding MGCP though the Cisco Voice and Gatekeepers book which covers how exactly a MGCP gateway registers.

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