topic Hello I just moved hard in Unified Communications Infrastructure

when will hard conference bridge be used ?

yuexp0929 — Tue, 19 Mar 2019 16:17:02 GMT

Hello All

I have a question of conference bridge.

Call manager system is 9. I have three sites Site A , Site B and Site C. The codec is G729 between any two sites.

I did a test of conference. I made conference with cisco 7942 on site A. I pull two phone in site B to join the conference. I thought the PVDM in site A 's voice gateway will be used, but it dose not be used. and I found that the codec change from G729 to G711 when the phone join the conference.

Could you help me to explain why the codec change from G729 to G711. Thank you very much !

Hardware based conference

Terry Cheema — Thu, 05 Mar 2015 10:29:35 GMT

Hardware based conference bridge are used when you have calls joining the conference with different codecs, for example, if you try to dial From Site A - Site B (G729) and then conference in a PSTN call (using G711), then you will need h/w based conference bridge to mix and stream the audio.

So wherever you have multiple sites with multiple codecs involved you normally would need a h/w based bridge.

If it was a single site using G711 throughout you would not need a h/w conferencing bridge, CUCM software Conference bridge would have been enough.

As software based bridge can mix and stream the variants of G711 (i.e G711alaw and G711 ulaw) and it can support up to 48 streams.

-Terry

Please rate all helpful posts

Hello Terry Cheema,

yuexp0929 — Thu, 05 Mar 2015 10:35:40 GMT

Hello Terry Cheema,

Thanks for your answer !

I did a test as like you said. first I make a call from Site A to Site B. the codec is G729 and make a call from Site A to PSTN . but the hard conference is not be used ? I used sh dspfarm dsp all to check it.

Make the conference call.

Terry Cheema — Thu, 05 Mar 2015 10:45:50 GMT

Make the conference call. From the gateway for the site initiating the conference call, run the output of below two commands:

sh voice call status

sh sccp connections

-Terry

What CFB you use is defined

Jaime Valencia — Thu, 05 Mar 2015 15:21:00 GMT

What CFB you use is defined by the MRGL you have assigned to your devices, and what codec you will speak to the CFB is defined by your regions.

You might simply have it configured to speak G711 to your CFB via your regions.

And if you are expecting CUCM to magically choose the HW CFB when you have to mix codecs, that won't happen, the MRG/MRGL defined what CFB will be used, if more that one are in the same MRG, they will attempt to be used in a round robin fashion to distribute the load. If you need to use something besides G711 and you have it so that your SW CFB is the first option, the call will simply fail. The only "intelligence" CUCM has in regards to choosing a CFB is when you attempt a Videoconference and a VCFB is configured.

When will it be used??? When you configure that to happen.

Hello Terry, As your said I

yuexp0929 — Fri, 06 Mar 2015 01:05:41 GMT

Hello Terry,

As your said I initiated a conference all. first call is from Site A to Site B through WAN. This call is internal call, so it is not showed at voice gateway. Second call is from site A to PSTN.

cnpt1#sh voice call status
CallID CID ccVdb Port Slot/DSP:Ch Called # Codec MLPP Dial-peers
0x46E6 54F 0x2AB1F014 0/0/0:15.31 0/1:1 *3810523220 g711ulaw 1001/1000
1 active call found
cnpt1#sh sccp connections

Total number of active session(s) 0, and connection(s) 0

As Jaime had posted check

Terry Cheema — Fri, 06 Mar 2015 02:16:52 GMT

As Jaime had posted check your MRGL/MRG for this site and confirm what resources do you see there. It must be using resources according to your config in CUCM.

Hello All I checked the

yuexp0929 — Fri, 06 Mar 2015 02:37:26 GMT

Hello All

I checked the configuration of MRGL/MRG. It is correct. for verify it, I moved all soft CFB from MRG except CFB on Voice Gateway. The CFB is used.

cnpt1#sh dspfarm dsp all
SLOT DSP VERSION STATUS CHNL USE TYPE RSC_ID BRIDGE_ID PKTS_TXED PKTS_RXED

0    2   26.8.2   UP     1    USED conf    2      0x1B16      12104     26283
0    2   26.8.2   UP     1    USED conf    2      0x1B19      12343     26280
0    2   26.8.2   UP     1    USED conf    2      0x1B1C      9004      18590
0    2   26.8.2   UP     1    USED conf    2      0x1B1F      7462      15930
0    2   26.8.2   UP     1    USED conf    2      0x1B22      5718      11993
0    2   26.8.2   UP     1    USED conf    2      0x1B25      4691      10746
0    2   26.8.2   UP     1    USED conf    2      0x1B28      4164      9429
0    2   26.8.2   UP     N/A FREE xcode 1      -         -         -
0    2   26.8.2   UP     N/A FREE xcode 1      -         -         -
0    2   26.8.2   UP     N/A FREE conf   2      -         -         -
0    2   26.8.2   UP     N/A FREE conf   2      -         -         -
0    2   26.8.2   UP     N/A FREE conf   2      -         -         -

Total number of DSPFARM DSP channel(s) 6

Hello All I just make a

yuexp0929 — Fri, 06 Mar 2015 03:00:02 GMT

Hello All

I just make a conference call as before. The MRG include soft and Hard CFB.I check the trace on RTMT and find a soft CFB,CFB_2 is used.

Ok - good. CUCM will allocate

Terry Cheema — Fri, 06 Mar 2015 06:05:07 GMT

Ok - good. CUCM will allocate the resource accroding to the need.

Please do rate all helpful posts and mark the thread as answered if you have no other queries.

Terry

Hello Terry， I do not

yuexp0929 — Fri, 06 Mar 2015 06:37:50 GMT

Hello Terry，

I do not understand ！

A phone in siteA make a call to a phone in siteB. The codec is G729. When the phone in siteA make a conference call and pull the the phone in siteB into conference , the codec change from G729 to G711.

Do it mean that soft CFB also support mixing conference ?

Thats exactly the function of

Terry Cheema — Fri, 06 Mar 2015 07:20:08 GMT

Thats exactly the function of h/w conference bridge, takes all different connection, with multiple codecs and streams into a single G711 stream.

Refer to here: Read this chapter you will get better under standing

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/9x/uc9x/media.html#wp1112995

Conferencing

A conference bridge is a resource that joins multiple participants into a single call (audio or video). It can accept any number of connections for a given conference, up to the maximum number of streams allowed for a single conference on that device. There is a one-to-one correspondence between media streams connected to a conference and participants connected to the conference. The conference bridge mixes the streams together and creates a unique output stream for each connected party. The output stream for a given party is the composite of the streams from all connected parties minus their own input stream. Some conference bridges mix only the three loudest talkers on the conference and distribute that composite stream to each participant (minus their own input stream if they are one of the talkers).

Audio Conferencing

Audio conferencing can be performed by both software-based and hardware-based conferencing resources. A hardware conference bridge has all the capabilities of a software conference bridge. In addition, some hardware conference bridges can support multiple low bit-rate (LBR) stream types such as G.729 or G.723. This capability enables some hardware conference bridges to handle mixed-mode conferences. In a mixed-mode conference, the hardware conference bridge transcodes G.729 and G.723 streams into G.711 streams, mixes them, and then encodes the resulting stream into the appropriate stream type for transmission back to the user. Some hardware conference bridges support only G.711 conferences.

All conference bridges that are under the control of Cisco Unified Communications Manager (Unified CM) use Skinny Client Control Protocol (SCCP) to communicate with Unified CM.

Unified CM allocates a conference bridge from a conferencing resource that is registered with the Unified CM cluster. Both hardware and software conferencing resources can register with Unified CM at the same time, and Unified CM can allocate and use conference bridges from either resource. Unified CM does not distinguish between these types of conference bridges when it processes a conference allocation request.

The number of individual conferences that may be supported by the resource varies, and the maximum number of participants in a single conference varies, depending on the resource.

Hello I just moved hard

yuexp0929 — Fri, 06 Mar 2015 08:58:00 GMT

Hello

I just moved hard CFB out site A's MRG. I made a conference call as before and it is successful.

Do it mean Hard CFB is not necessary ？

Hard CFB is definitely

Terry Cheema — Fri, 06 Mar 2015 09:11:57 GMT

Hard CFB is definitely required when you have G729 involved. Software CFB supports only G711 codec.

Hello What aobut my test ?

yuexp0929 — Fri, 06 Mar 2015 09:29:53 GMT

Hello

What aobut my test ? I moved Hard CFB. and Make a conference call. One phone is in site B. the codec is G729 between them. another call is PSTN Phone. The codec became G711 when the both phone join the conference. and the conference is successful.

I mean that no hard CFB is used in this time. I do not know what situation Hard CFB is necessary ?