TechNote (Archived)

Bandwidth calculation information

There are many network factors that may contribute to an online meeting experience. This TechNote contains information and suggestions that will help you understand bandwidth requirements for a good online meeting experience.

All meeting rooms have the ability to optimize the room bandwidth, in order to get the best experience. This option can be found under the Meeting menu, within each individual room. Setting this to DSL will provide a good experience for users on LAN and broadband connections. If most of the users are using a modem connection setting to Modem is a better option.

Select LAN only if all the users are on a high speed network and presenters are using high end systems (2Ghz and above desktops). The LAN will result in applications sending high quality audio, video and screen shared images.

Note: This not only increases bandwidth consumption but also increases CPU usage on the presenter's system. If CPU usage goes beyond 80%, latency will increase resulting in choppy audio and video.
By default the connection speed for each presenter or participant is set to LAN. It is always a good practice to set the connection speed to the actual connection speed of the user. This can be done by navigating to Meeting >My Connection Speed.
If participants experience latency or choppy audio they should lower their individual meeting room setting, which can be set in the same Meeting menu.
If multiple users are sharing a T1 or DSL connection they should be aware that this is a shared resource. Be sure to divide the total bandwidth by the number of users sharing the same connection.
- T1 - 1.5 Mbits/sec up and down.
- DSL varies based on type but in general 350 up and 1MB down

Below are some bandwidth calculations based on a meeting with audio, video, and slides. Calculations also based on 1024x768 full screen.

Room bandwidth: Modem

One presenter can generate about 26 Kbits/sec of data.
Viewers will need about 29 Kbits/sec of down stream bandwidth to have a good experience.
Having more than one presenter on a modem room setting is not recommended.
If screen sharing is added to Modem - total bandwidth required is about 49 Kbits/sec. This is close to saturating a modem connection. Any bottleneck in the network can cause latency or dropped message. (Not recommended)

Room bandwidth: DSL

1 presenter generates close to 125 Kbits/sec. Each viewer will require about 128 Kbits/sec to consume all the data generated.
Adding screen sharing: 184 Kbits/sec
To have a good live experience with DSL setting make sure viewers have at least 200 Kbits/sec down stream bandwidth and presenters have a 200 Kbits/sec upstream bandwidth.

Room bandwidth: LAN

1 presenter generates close to 250 Kbits/sec. Each viewer will require about 255 Kbits/sec to consume all the data generated.
Adding screen sharing results in about 300 Kbits/sec
To have a good live experience with LAN setting make sure viewers have at least 400 Kbits/sec down stream bandwidth and presenters have a 400 Kbits/sec upstream bandwidth.

Note: Screen sharing bandwidth can vary based on the content being shared and resolution of the screen. Also, these numbers are a general guideline and actual capacity my vary with each network environment.