Calling Other MCU Conference Rooms

One of the conundrums of my videoconferencing life is how to make calls work with weird dialing. Since 60% of my calls are with schools across the country (off my network with various dialing policies of their own), I run into these a lot.  Please, please, please vendors, when will it work like a phone?!

Yesterday I received additional training on TMS from SKC. We spent pretty much two hours trying to figure out how to make TMS in conjunction with my Tandberg MPS 800 dial conferences on other MCUs that are off my network. Since the results are obscure and undocumented, I thought it would be helpful to share. This was tested with TMS J12.2 and the MPS J4.5.


Create a Participant Template. Enter the MCU IP as normal. In the DTMF box, enter the extension this way:

Polycom MGC:

Create a Participant Template. Enter the MCU IP as normal. In the DTMF box, enter the extension this way:


(Apparently the numbers come too fast for the MGC. The commas slow it down.)

Polycom RMX

Create a Participant Template. Enter the MCU IP as normal. In the DTMF box, enter the extension this way:


Tandberg MPS

This needs the alias@IP format, however you can’t enter this in the participant template. If you put the alias@IP in the IP field, it strips out the @IP.

So, instead, use the phone book to enter alias@IP.

This solution works for a Tandberg endpoint behind a Border Controller as well.

Your Turn: If you have additional tips for making MCUs dial conferences and extensions on other equipment outside your network, please comment!!

0 replies on “Calling Other MCU Conference Rooms”

  1. re: Please, please, please vendors, when will it work like a phone?!

    This is the fundamental problem with the video conferencing manufacturers. They all want end users and corporations to become video conferencing servcie providers. The video infrastructure, bridges, gateways, gatekeepers, etc are the same components used in the cell phone service. However, no organization builds there own cell phone service. Do you build your own internet service, long distance, local voice services, etc? Why did webex take off? Webex was a service, not software or hardware.

    Manufacturers generate large one time revenue from sales of infrastructure product. What they don’t realize, but should by now; is that making the end user deliver the service over the long term results in low usage or intense labor. Without usage justifying further investment we end up like it is today. Less than 2% of conference rooms have video conferencing. Almost 96% of the conference rooms have conference phones. The long term thinking should be to get more penetration into conference room and less focus near term large one time infrastructure sales by the manufacturers.

    So unfortunately until the manufacturers get out of their own way, it will never be as easy as dialing a phone.

    Just my two cents.

  2. To: B. Bailey… um, “No”. 😉

    Janine… “Please, please, please vendors, when will it work like a phone?!”

    It does. Today. As conference service providers (ESC, ESU, ISU, BOCE, etc.) we need to understand the technology, protocols and services we provide to our end users.

    What you’re looking for the the Global Dialing Scheme (GDS). It exists, it works and it’s… complex.

    You want it to work like a phone? Well, phones used to only come from Ma Bell. We relied on her to provide us with equipment, services, numbering, etc. Then came Key and Private Branch Exchange (PBX) equipment. And schools understood that we could reduce expenses by buying hardware and running it ourselves (instead of buying Centrex service.)

    But with that Key or PBX system, came the additional responsibility of dialing plans, extensions, trunking, least cost routing, choosing local and long distance service providers, hardware maintenance, software maintenance, user training, etc.

    Sounds a lot like video conferencing today. We have endpoints (telephones) and MCUs/bridges (PBX or Key systems). There are trunks (IP and/or ISDN connections) and numbers (IP, E.164, ISDN, etc.). As the people that run the organizations phone/video service we have to do it all.

    So… what is GDS?

    GDS is a protocol to dial between H.323 endpoints and conferences on different networks. It involves trust relationships between H.323 gatekeepers on independent video conferencing networks.

    You apply for an Organizational Prefix (OP) and create zone relationships between your Gatekeeper and upstream gatekeepers. GDS numbers get pretty long (you thought 10 digit telephone dialing was bad) and can be hard to remember, but that’s what the “phone book” is for on the endpoint or network.

    There are many design, technology and procedural issues to consider before jumping into the GDS community. But it does work. On our video conference network, we have implemented outbound GDS dialing and are still working on incoming dialing. I can dial (and have dialed) a GDS number to reach an endpoint or a conference on another organizations MCU/bridge. (For example, last time I joined the the Megaconference, I simply dialed in via the GDS number to the main bridge.)

    Maybe the K-12 VTC community need to have some sessions regarding GDS at ISTE, USDLA and/or FETC. We may also want to start small and begin by bringing a few K-12 networks together using GDS before encouraging everyone to use it. Like I said, it is complex and it is useful.

    Additional Links

    GDS – Wikipedia
    GDS – Internet2
    GDS – ViDe
    E.164 – Wikipedia

    Good reading!

    • Craig – I agree that GDS is partially a solution – we are on GDS and use it to call sites in the UK because it’s easier than having to schedule with the JANET MCUs. However, what about the places where VC is installed without any network infrastructure or support? I know schools that do Read Around the Planet who just got a unit and that’s it. They aren’t connected to a service center or state network. How would they get connected or even know about GDS?

      By the way, we have a field in the equipment profiles in CAPspace for GDS numbers….


  3. recently worked with an off-site organization to connect to one of our private network sites through our RMX or MGC. They had a Codian which would not allow them to enter the conference ID as part of the address. We did find that they could create a conference with a Polycom unit in it, connect us to the conference and use the Polycom to enter the conf ID. HOWEVER, it had to be completely “quiet”, mute everybody, for it to work.
    I’ll be interested to look into the participant template work-around.

    • Ken – what I’ve seen of the Codian there’s a “gateway” way to enter the MGC/RMX IP plus conference ID. I haven’t done it but I’ve heard others describe it – on the Codian you set up the MGC/RMX’s IP as a gateway, and then add the participant to the conference using the IP gateway and then entering the ID. I don’t think it’s that the Codian can’t call the Polycom MCUs; it’s just a matter of learning how to do it – and these things aren’t documented well…..

      Let us know how it works out….

  4. any thoughts on dialing extensions from TMS via ISDN for bridging-in a voice-only participant? My TMS (11.9.1) can sucessfully use its ISDN connectivity to direct dial my cell, but if I ask it to call my office, it doesn’t work – whether I put the extension in the extension field, in the DTMF field or in the format : number*ext….all very frustrating.

    thanks for the blog(s)!

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