Making Sense of Our Video Lingo: MCUs, Video Bridges, and VMRs


In the videoconferencing industry we traditionally held our meetings on video bridges, otherwise known as MCUs (Multipoint Control Units). Today, we tend to use a more modern term to describe this meeting experience; the VMR or Virtual Meeting Room. This had led to a little bit of confusion. Are these terms interchangeable? Is a VMR the same thing as an MCU? If not, which one should your organization be shopping for?

What is a VMR?

Let’s start with the VMR as it is more self defining. I could meet with you in a physical meeting room, where we can shake hands and share a pizza, or I can meet with you in the cyberspace equivalent, which is the VMR. There are many different types and flavors of VMR, each providing a significantly different experience, but there is the one key thing they all share in common. The fact that it is a virtual experience. The experience of meeting with people, even though you are not physically in the same space as them.

With some VMR experiences you may see all meeting attendees on the screen, Brady Bunch style. With others you may only see the active speaker. Some VMRs may allow meeting attendees to share their screen for real time collaboration. Some may support chat or allow recording. Some may be manageable by an administrator, who can join the meeting to troubleshoot and moderate (muting, inviting, dropping attendees, etc.). Regardless of features (or lack thereof), as long as you are enjoying a meeting in an imaginary room over the internet, you are in a VMR.

Theoretically, even a two person video meeting is a virtual meeting experience. While we tend to think of 2 person meetings as “point to point” calls, or “direct” calls, the fact is you are still being provided with the experience of meeting with that person, even though you are not in the same place. However, the term VMR is generally used to refer to multiparty meetings. Or at least it is used to refer to meetings that could support multiple people, regardless of how many participants actually attend any given meeting. You are arguably technically correct if you refer to a person to person Skype call as a VMR experience, but that isn’t how we generally use the term.

What is an MCU?

An MCU is the technology which creates the VMR experience. MCUs are also known as video bridges, which helps to clarify their function. It literally provides the bridge, or the connection, between the video systems (or desktops, or even mobile devices), that are joining the meeting. The MCU is the platform/product which creates the VMR experience. Some MCUs are very basic, a server running in your IT closet that creates a very basic VMR which you can call into. Think of the virtual equivalent of a meeting room with nothing in it but 6 chairs. Other MCUs have a robust feature set, and they, in turn, create a more robust VMR experience. Think of the virtual equivalent of a meeting room with whiteboards, touchscreens, recording equipment, lecture platforms, etc. While MCUs vary greatly in capabilities, the only essential element is that they can connect multiple video systems into a single meeting.

MCUs and VMRs go hand in hand. You can’t have one without the other. This may confuse those who are looking at VMR services. Vendors like BlueJeans, StarLeaf, Univago, Videxio, and Zoom sell a VMR experience. You pay for licenses or accounts, and connect to your virtual meeting. There doesn’t appear to be any MCU. You never buy an MCU or install one in your IT closet. However, all of these VMRs are being hosted on MCUs. Each of those vendors has MCUs (either their own proprietary MCUs, or MCUs they purchased from other vendors) running on server farms, or in the cloud. You can’t buy a BlueJeans MCU, but if you join a BlueJeans meeting, that VMR experience is being hosted on one of their MCUs.

On the other hand, we have our traditional MCU products, such as Acano (now Cisco Meeting Server), Avaya Scopia, Pexip Infinity, and the Polycom RMX. We don’t think of these as VMRs, these are products, not experiences. Most are hardware devices, server appliances, and one (Pexip) is pure software, which can be installed on your own server, or in the cloud. However, each of these creates VMR experiences. When you power up a Polycom RMX, and create a new call with five attendees, they are enjoying a VMR experience.

What does this all mean for video customers?

At the end of the day, an organization needs to decide whether they want to purchase an MCU to create and manage their own VMRs, or whether to use a cloud video service and rent/lease VMR space. While the trend is clearly going towards the cloud, there are still reasons for organizations to keep things internal. In particular, organizations with unusually high security concerns might want to keep all communication traffic within their building. However, this trend towards the cloud is not necessarily a death knell for MCU manufacturers. Organizations may be turning to service providers for their VMR experiences, but those service providers still need to host the calls on an MCU.

I realized these terms needed clarification during a recent briefing with an end user organization. I was speaking with a CIO who was asking about various platforms and services. At one point he said he was surprised that some service providers were using Pexip as an MCU (as Yorktel does with its Univago service). I said, “Well, everyone who uses Pexip is using it as an MCU, because that is what it is. Pexip Infinity is a software MCU.” He then said, “Oh, no Pexip is a VMR, like Acano.” I replied, “Acano is also an MCU,” to which he responded, “Acano can’t be an MCU, it doesn’t have manageability like the RMX or the old Codian. Administrators can’t use the Acano to moderate meetings.” Well, Acano does have managament software that does exactly that, but even if it didn’t it would still be an MCU. It is an appliance that creates a VMR experience. The Acano box is the MCU, the Acano call is the VMR.

Perhaps I can add a final bit of clarification with some obvious analogies. Let’s say you take an Uber ride in a Toyota. The Toyota is like the MCU and the Uber ride is like the VMR. The Toyota is the technology, the product, while the ride is the experience. If you go to see the new Star Wars movie, the projector, film, and screen are like the MCU, and the movie experience is like the VMR. The projector, file and screen are the technology, creating the movie experience. If you go to a fancy restaurant, the steak and veggies on your plate are like the MCU and the meal experience is the VMR.

While this may have been a bit of a pedantic exercise, I hope it provides some clarification for anyone who may have been confused by the way we tend to throw these terms around. For those of my friends in the industry who use these terms on a regular basis, do you agree with what I’ve written here, or did I miss the mark? Let me know in the comments below!


About Author

David Maldow is the Founder & CEO of Let's Do Video and has been covering the visual collaboration industry, and related technologies, for over a decade. His background includes 5 years at Wainhouse Research, where he managed the Video Test Lab and evaluated many of the leading solutions at the time. David has authored hundreds of articles and thought pieces both at Telepresence Options, where he was managing partner for several years, as well as here at Let's Do Video. David often speaks at industry events and webinars as well as hosting the LDV Video Podcast.

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