Conferencing and Transcoder Resources in Campus Environment

[johnnylingo]

This is my first time working in a campus environment, and have some questions regarding best practices especially regarding conferencing and transcoding resources.

The central office consists of several buildings, all connected via gigabit fiber. It houses a single CallManager Cluster, IPCC and Unity servers, and 2 2821 voice gateways. Each gateway has a connection PRI to the PSTN, and also a PRI to the legacy PBX.

The two remote offices (50 users) are located within one mile. Each office is connected to the main office via metro ethernet, but also has a 2821 with FXO ports to handle 911 calls. In addition, the 2821 has a Data T1 terminated on a 2821 at the central office. Routing is configured so all Voice VLAN traffic goes over the Data T1 rather than the Metro ethernet.

Due to the 1.5 MB limit on the data T1, calls to/from the remote offices use G.729. Calls in the same office use G.711.

My question is where conferencing and trancoder resources should be configured. Currently, all 2821s are configure as MGCP gateways in CCM, but none have conferencing or transcoding configured. Should I configure this on the 2821s in the central office and have the remote offices use them, or configure them on the remote 2821s as well? Keep in mind the remote offices do not have PRIs, just a couple POTS lines for 911 and SRST calls.

[fred.s.mollenkopf]

John,

Well first and foremost you want to review the CCM SRND. I'm gonna link the CCM 4.1.3 (most common) but you can also find the rest at this url.

SRND Home

http://www.cisco.com/en/US/netsol/ns656/networking_solutions_program_category_home.html

CCM 4.x SRND

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_implementation_design_guide_book09186a00806e8a79.html

Ok to answer your question, you will need Transcoders located at the main site at a bare minimum so the call won't go over the WAN as G711. Transcoders on the other side wouldn't be much help.

For conferencing it's recommended to have hardware resources at both sites. But you could get away with using Software at the CCM sites and hardware in the routers at the remotes.

Now to achieve the hardware conferencing and transcoding you will need to use DSP resources. Here is a link for configuring the DSP within the IOS and CCM.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/vvfax_c/callc_c/ccm_c/index.htm

The 2821 will need DSP modules added to them. You can do a "show inventory" to see if you have any currently. Lastly a link to the DSP calculator to determine what parts you need for the amount of expected conferences and transcoding sessions.

http://www.cisco.com/en/US/support/tsd_tools_by_category.html

Please rate any helpful posts

Thanks

Fred

[Rob Huffman]

Hi Fred,

Excellent in depth answer. 5 points from me for sure!

Take care,

Rob

[johnnylingo]

What's very interesting is currently no Transcoders are configured, and indeed Perfmon has shown none to be used so far. However, calls are going over the WAN as G.729r8. This is due to how the regions are configured in CallManager. What doesn't make sense is these are mostly Call Center users using IPCC Express 4.0(4), which is configured to use G.711.

The 2821's already have 3 DSPs onboard, which should be enough. They go light on the conferencing, so I'm planning to allocate most towards transcoding.

What's still confusing me on conferencing is this - since the conference bridge will have to make X connections to the VG for every external participant, wouldn't it make sense to use the conference bridge closest to the VG and not necessarily the phone?

[fred.s.mollenkopf]

John,

Usually if IPCC is in the mix without Transcoders, then IPCC ports are put into it's own Device Pool/Region with G711 to all. Even though at the HQ to Remote you might be running Device Pool/Regions with G729 in between. Check that to be sure.

Also later IPCC versions have the option of being installed with either G711 or G729, just to make you aware of the options. If you want to verify this in IPCC 4.x, goto AppAdmin/System/System Parameters and look for the installed codec.

As far as conferencing, my original recommendation was based on normal installs. I really didn't notice in your original post that you had limited PSTN access at the remotes. So this is going to come down to your total resources. Do you have limited WAN bandwidth? Do you expect more parties on the Conference Bridge to be remote PSTN or local IP Phones? Really its going to come down to your DSP resources compared to your WAN resources.

With all that being said, from your last post I would gather that your conference calls mainly are with more participants from the PSTN. So I would configure the 2821s at the main site with enough sessions to transcode my calls to IPCC. Then configure the remainder for conferencing. Then the DSPs in the remote I would configure for conferencing. The I would create MRG for the main site resources then another for the remote. Then create a MRGL for the remotes using the main site MRG then the remote MRG.

The reason I suggest this is mainly because you feel more calls will traverse the WAN if you have the remote site initiate it's conference with a local bridge. Most importantly you want to make sure you have enough for transcoding and worse case scenario if you run out of HW conf resources at the main site you can failback to the HW resources at the remote. Of course you should really try to trend this with CCM Perfmon, looking at stats like Location utilization and the conference bridges utilization.

Hope this helps

Thanks

Fred

[johnnylingo]

Thanks Fred, that helps. We are running 4.0(4) on IPCC and appear to only support G.711. So upon further review I believe the calls are actually going as G.711 for IPCC. However, calls to/from the main campus or PSTN go G.729. The CTI route points are the the Device Pool for the main campus, which should probably be changed so they can be more easily managed.

Question - Is there a quick and easy way to see how many calls an IPCC server is currently handling? Each site has a T1, so my next task is get firm numbers on how many calls are typically in progress to each site on average.

Your suggestion to use conference resources at the main site as primary with secondary at the remote site is what I was thinking as the best design. Transcoders would be needed at both sides, assuming we do G.729 over the WAN and G.711 over the LAN.

So I guess the moral of the story here is it makes sense to put the conference bridge closest to point where most of the participants will be, not necessarily closest to the initiator.

[fred.s.mollenkopf]

John,

Yes thats true about the moral, but most of the time you don't see your scenario. I get involved with a lot of IPT rollouts and most sites have their own PSTN connections unless we are talking Campus networks, which most of those have High Speed links between the sites.

As far as IPCC 4.x, it does support G729. This option only presents itself when you install it though. I believe you need to reinstall to change the IPCC codec. Like I said in the last post, check the codec in the web page like I suggested just so you know for a fact.

As far as reporting, IPCC has some built-in reporting but I've never worked with it much, just agent based reports. You should be able to pull CDR reports from CCM on the Route Points and CTI Ports. This should give you usage for the IPCC system since everything has to flow through them.

Thanks

Fred