Bandwidth Requirements For Video Conferencing
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 DS3-Bandwidth.com. An
excellent guideline resource for video conferencing set-up and
management is also available at "Video Conferencing Solutions".
About the author:
Michael is the owner of FreedomFire Communications....including
Business-VoIP-Solution.
com and DS3-Bandwidth.com. Michael also authors Broadband Nation
where you're always welcome to drop in and catch up on the
latest BroadBand news, tips, resources, and insights.