Tuesday, January 19, 2010

Bandwidth Requirements For Video Conferencing

Most of today's companies are maximizing their travel budgets and communication requirements by making smart use of videoconferencing as an alternative to face-to-face meetings. With this decision to implement enterprise-level videoconferencing comes a requiremnt for bandwidth requirements which are reliable and cost effective.

Videoconferencing can leverage the existing public telephone network, a private IP network or the Internet. The target bandwidth for interactive video communications is in the 300K to 400K bit/sec per stream range. This includes audio and video as well as control signaling.

The H.323 protocol does not require that two or more endpoints in a session send the same data rate they receive. A low-powered endpoint may only be able to encode at a rate of 100K bit/sec, but, because decoding is less processor-intensive, it could decode a 300K bit/sec videostream.

Nevertheless, in videoconferencing, bandwidth is assumed to be symmetrical. In full-duplex networks such as ISDN, Ethernet, ATM and time division multiplexed networks, capacity is expressed as bandwidth in one direction, though equal bandwidth is available for traffic in the opposite direction.

You need to estimate the number of simultaneous sessions your network needs to support, and figure out if your network has bandwidth end-to-end.

A T-1 bandwidth circuit offers 1.5M bit/sec in each direction and would be ample bandwidth for two 512K bit/sec or three 384K bit/sec videoconferences, depending on the amount of simultaneous traffic on the network. Also, make sure that you have 10/100 switched Ethernet throughout the LAN segments where videoconferencing traffic is expected.

Multipoint conference bandwidth (with which three or more locations can see and hear one another) is calculated separately from point-to-point sessions. Multipoint can be conducted in either IP or ISDN environments, and some conferencing units will support both network types.

Multipoint conferencing products may be software-based or accelerated with special hardware, and their configuration can produce different bandwidth consumption patterns as well as different user experiences. For example, when an endpoint is used to host a multipoint conference, the maximum bandwidth for any single participant is the bandwidth allocated to that host divided by the number of locations participating. When you need to have more than four locations on a call at the same time, network-based products are recommended.

If you decide that your IP network can't handle the additional traffic associated with live video sessions in a merged or converged network deployment, your options are to rely on circuit switched networks or to deploy additional IP bandwidth capacity. To assist in determining and acquiring the exact bandwidth to meet your requirements...it's strongly recommended to make use of a free technical consulatation service such as is available via Bandwidth Solutions.

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