MCS-7835 Conferencing and Transcoding capabilities

[patrick.hurley]

How much conferencing and transcoding capabilities does a MCS-7835H have before using a DSP Farm or other hardware DSP resources is desireable or required?

[jasyoung]

The IP Voice Media Streaming Service defaults to 48 conference participants. This is also the recommended maximum for a co-resident installation, where the server is expected to handle IP phone and gateway registrations as well. The conference bridge function may be invoked in any combination; 16 bridges of 3 participants or one bridge of 48 participants.

For very large clusters, IPVMS may be deployed on a server that doesn't run the CallManager service itself, which is to say, phones don't register to it. In this case, the upper limit may be adjusted at least to 128 participants (256 is possible, but 128 is the recommended max). Individual conferences may have up to 64 participants. You can make this adjustment on the Service Parameters page of the IP Voice Media Streaming Service.

For many deployments, adding hardware conference bridge resources is a good idea. This cuts down on the load on your servers. Some hardware conferencing resources can directly accept low-speed codecs into a conference, eliminating the need for a transcoder on that call. One limitation to keep in mind is that most of the hardware conference bridges (all but maybe the WS-SVC-CMM module, can't remember) limit the number of participants in one conference to 6 or 8 with no possibility of adjustment. It's up to you or your customer if that's a problem.

You'll note I didn't really talk about transcoding. The Media Termination Point service (also part of IPVMS) is technically a transcoder. However, it can only transcode between the G.711 μ-law and G.711 a-law codecs, and I believe Cisco's wideband codec as well. It does not support transcoding to or from any of the "low speed" codecs such as G.729. That's what most people want from a transcoder, so you really have to have hardware transcoding services available whenever you have sites that use low speed codecs.

Determining exactly what resources you need for any given installation can be complicated. This subject is discussed at length in the CallManager Solution Reference Network Design (SRND) documents. I recommend that you read them top-to-bottom, but the Media Resources section has some of the answers you're looking for. The SRNDs are found here:

http://www.cisco.com/go/srnd

[tarun.pahuja]

Excellent info! have a question

If i have only 1 central site. I creat a MRGL for all the phones in this site. This MRGL includes 1 MRG. This MRG includes software conference bridge and hardware conference bridge (lets say i register pvdms on an HDV module for conferencing).

Now, My question is, how many participants can i have in one conference??

Will the software bridge do load balancing with hardware conferencing capabilities??

Will i be able to have 64 participants in 1 conference bridge is CCM choose software conference bridge in the MRG??

Thanks

[jasyoung]

You can't really load balance within a MRG/MRGL. Resources within an MRG are used in strict order, and MRGs within an MRGL are used in strict order. If your hardware conference bridge is listed first in your single MRG, then it always be used unless it is full or unregistered. There is no capability to move a conference to another bridge resource once it's started. Neither is there a capability to link together two conference resources. CallManager will stop you from "conferencing a conference" under almost all circumstances.

So to answer your question, it depends on how you arrange your MRG, and depends on how your CallManager is configured. The maximum participants in a single conference is the maximum of a) the capabilities of the bridge hardware/software selected from your MRG/MRGL, and b) the 'Maximum Ad Hoc Conference' Service Parameter for the CallManager service ('Maximum MeetMe Conference Unicast' for meet-me conferences).

On small to medium sized cost-sensitive deployments, we are in the habit of configuring all extra PVDM resources as transcoders, and letting IPVMS handle all the conferencing. Modern MCS servers have way more CPU power than needed for all those < 500 phone deployments, so it's essentially free to do it there. It also lets us have extra transcoders. If you have sufficient resources to offer hardware conferencing, it is generally a good idea to have both available in your MRG/MRGL with the hardware bridge placed first. This way, IPVMS can take over conference bridging duties if the hardware conference bridge dies.

[dweiner]

These numbers are not correct, though perhaps technically possible. In CCM 3.x Cisco supports up to 6 participants on an ad hoc or MeetMe conference. In CCM 4.x we support up to 16, assuming the conferencing resource can handle that many (IOS-based DSP resources handle up to 6 with the NM-HDV modules or up to 2 conferences of 8 each with the new NM-HD-xVE or NM-HDV2 modules). 6608 and CMM ACT modules can handle the 16 participants. CMM sw-based conf resources can handle 16, but G.711 only.

CallManager will look at all conferencing resources in the MRG and use the one with the most unused capacity at the time of the conference.

[maharris]

I don't mean to butt in, but his numbers are right out of the latest SRND, I followed the link he provided, just to further my education, and read the Media Resources chapter. It looks like resources are load shared within a MRG, but you can prioritize them using the MRGL, so all resources in the first MRG will be exhausted, then it will move to the next MRG in the list.

Mary Beth

[jasyoung]

I stand corrected on the MRG ordering issue. We usually put all our hardware resources in one MRG and the software in another and use MRGLs for ordering, so I hadn't noticed that the MRGs were not internally ordered. Thanks.

However, I stand by the numbers on software conferencing. The max participants in a software conference are documented all over CCO, and as maharris mentioned, I drew the numbers right out of the CallManager 4.0 SRND. Are you certain?

[dweiner]

I STAND CORRECTED!

Thank you all for keeping me straight. I did not notice that we (Cisco) had opened this up in 4.x! This had previously been restricted from a support standpoint, though not technically (you could do it, it just wasn't supported). Last I heard we were going to 16 in 4.0 but it ended up better than that.

I was ALSO wrong about the CMM ACT module - it supports up to 8 participants in any one conference.

Jeez, what a day...

[maharris]

You know, if you guys would quit CHANGING this stuff.. I know, I know, it is all in the name of progress

; )

Mary Beth

[patrick.hurley]

So back to my original question then. Does any of this affect what 4.1 can do from a transcoding perspective going from G.729a to G.711 or is hardware transcoding still the only way to accomplish this?

Thanks,

Patrick

[maharris]

You will need hardware dsps for transcoding. I even checked the 4.1 release notes to make sure they didn't slip something in under 'new and changed'

Mary Beth