How to calculate video conferencing bandwidth requirements

Image motion, frame rates and screen resolution often dictate video conferencing bandwidth requirements. The number of endpoints and concurrent calls are also key factors.

As demand for high-definition video conferencing grows, so does the need to provision adequate bandwidth to support...

video needs. A successful video conferencing implementation requires addressing quality, number of endpoints, multipoint control unit location and cloud-based virtual meeting room services.

A key requirement for a successful deployment of business video conferencing is ensuring sufficient bandwidth between endpoints to support high-definition video applications and room systems. Two parameters drive video conferencing bandwidth requirements: the bandwidth per video conference call and the number of concurrent video conference calls on each network link.

Determining video conferencing bandwidth requirements

Video conferences can require anywhere from 128 Kbps for a low-quality desktop endpoint, up to 20 Mbps for an immersive three-screen telepresence suite. Video conferencing bandwidth requirements are driven by the resolution and the ability of the session to handle image motion.

The table below provides typical examples of video conferencing bandwidth requirements, considering the specified resolution and frame rate. Frame rate determines the ability of the video conference call to handle motion, while resolution determines how many pixels are on the screen image -- and, thus, how much detail users will see in that image.

These video conferencing bandwidth requirements are per screen, so dual and three-screen systems may require additional bandwidth.

Video conferencing bandwidth requirements

Bandwidth

Resolution

Frame Rate

384 Kbps

CIF

30 fps

512 Kbps

4CIF

15 fps +

768 Kbps

4CIF

30 fps

1 Mbps

HD720

15 fps +

2 Mbps

HD720

30 fps

4 Mbps

HD720

60 fps

6 Mbps

HD1080

30 fps

~7 Mbps

HD1080

60 fps

Kbps: kilobits per second
Mbps: megabytes per second
CIF: common intermediate format
HD: high definition
fps: frames per second

Use these values as guidelines to assess network bandwidth. But remember to obtain specific requirements from your vendor, since bandwidth needs are typically affected by the choice of codec, compression and proprietary system capabilities.

Also, the video conferencing bandwidth requirements in this table are for the amount of traffic supported inside the Real-Time Transport Protocol (RTP) packet payload. The actual bandwidth on the IP network -- after adding RTP, User Datagram Protocol, IP and Ethernet headers -- will be about 20% higher. So, 1 Mbps video conference calls actually use about 1.2 Mbps of network bandwidth. I refer to these values as transport bandwidth (1 Mbps) and network bandwidth (1.2 Mbps) to avoid confusion.

To determine the right resolution and frame rate for your company, make sure users experience the video conference calls in the actual context where they will be used, such as the desktop, mobile device or conference room. Additionally, users should experience the video calls with the screens or projectors you plan to use, so you can determine if the quality is sufficient.

If end users are not comfortable with the quality, they will quickly resort to other methods of communication, such as a phone call or travel. Between quality and cost, there's a tradeoff. So, while users may prefer high-definition 1080p 60 fps, the cost of provisioning sufficient bandwidth to support conferences at that resolution and frame rate may be cost-prohibitive, especially in underserved parts of the world.

Estimating concurrent video conference calls

The next step is to determine how many concurrent calls each WAN link must support.

For small offices, with only one or two video conferencing systems and no desktop or mobile video conferencing, assume the two systems are running concurrently. For larger offices, estimate how many video conference calls occur concurrently based on your busiest meeting times. A helpful guide is to assume half of your conference rooms are being used, then adjust bandwidth needs based on actual usage.

If your organization has offices across multiple time zones, factor in time shifts. Map the call patterns onto the network topology and create a spreadsheet to track concurrent call assumptions and the bandwidth per call. A spreadsheet will allow you to modify parameters to create what-if scenarios.

Beware of the video conferencing bridge

The video conferencing bridge, or multipoint control unit (MCU), is a bandwidth hotspot. All video conferencing endpoints in concurrent multipoint video calls connect directly to the bridge. Thus, the bridge needs to be in a location that supports a high-bandwidth connection.

Increasingly, organizations are looking to cloud-based virtual meeting rooms to support a growing number of conferences without making additional capital investments in MCUs. However, cloud-based MCU services will place additional demands on your network for internet bandwidth.

New video conferencing strategies often put the bridge in a data center because it looks and smells like a server. But the best place for the bridge may be in a colocation facility near the core of the WAN service provider's network. Bandwidth is inexpensive at these locations, and since video conferencing call connections come from all parts of the WAN, the bridge would be in the right place to support many endpoints. This approach also scales well as video conferencing calls grow within the company.

Small companies normally just use the built-in MCU capability in some video conferencing endpoints. This approach works well for small conferences with two or three rooms, but it doesn't scale. 

Multiple remote rooms connecting to the MCU in a small office room system will quickly eat up bandwidth. Here, again, cloud-based MCU services are nifty, because multiparty room conferences simply require each location to connect to the internet.

Managing bandwidth with call admission control

The last step is to make sure your video conferencing has call admission control (CAC).

The communications manager or gatekeeper is programmed to understand the network topology and how many concurrent calls are allowed on each link. If a new video conference call would violate one of those constraints, the call is denied. This mechanism ensures video conference calls get the bandwidth they need and maintain high quality throughout the call. 

CAC is especially important for organizations that make heavy use of desktop and mobile video conferencing over the wireless LAN, since these applications can overwhelm a network if used heavily.

Next Steps

See how video conferencing is becoming more flexible.

Need to buy bandwidth for your organization? Here's how.

Choosing the right video conferencing equipment for your organization.

This was last published in November 2016

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When estimating video conferencing bandwidth, how does your organization balance cost and quality?
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Bandwidth requirement depends upon which video conferencing software you use. For e.g. If you use R-HUB, it requires 100Kpbs per attendee (up to 3Mbps depending on your server configuration for HD video conferencing and bandwidth availability in real-time)
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