Aethra avc8500 User Guide
75
Appendices
Network Requirements IP\H.323
The network requirements for point-point connections between videoconferencing terminals are as follows.
The complete network path connecting two H.323 terminals must have a constant available bandwidth for the whole duration
of the connection. The effective bandwidth used on LAN/WAN Full-Duplex network connections is equal to the sum of the
The complete network path connecting two H.323 terminals must have a constant available bandwidth for the whole duration
of the connection. The effective bandwidth used on LAN/WAN Full-Duplex network connections is equal to the sum of the
Audio Rate and Video Rate, plus approximately 20% for TCP/IP overhead.
In the case of Half-Duplex LAN/WAN networks, the aforementioned bandwidth is doubled. For example, if it is necessary to
guarantee a 384K connection for the video and a 64K for the audio, the bandwidth allocated must be at least (384+64) *1.2 ≈
540K for each Half-Duplex connection. In case of dial-up WAN links, it should be underlined that their efficiency in terms of
“useful” bandwidth is approximately half the total available bandwidth.
In the case of Half-Duplex LAN/WAN networks, the aforementioned bandwidth is doubled. For example, if it is necessary to
guarantee a 384K connection for the video and a 64K for the audio, the bandwidth allocated must be at least (384+64) *1.2 ≈
540K for each Half-Duplex connection. In case of dial-up WAN links, it should be underlined that their efficiency in terms of
“useful” bandwidth is approximately half the total available bandwidth.
It is always preferable to use mechanisms such as QoS for WANs because they take into account the total bandwidth required
for a videoconference, rather than relying exclusively on over-dimensioning the network. This is necessary for the handling of
increasing numbers of simultaneous connections or a network that is already loaded.
The network needs to be set up so that latency and jitter are as low as possible. Extended times for latency and variable jitter
can create serious problems, especially in video quality.
for a videoconference, rather than relying exclusively on over-dimensioning the network. This is necessary for the handling of
increasing numbers of simultaneous connections or a network that is already loaded.
The network needs to be set up so that latency and jitter are as low as possible. Extended times for latency and variable jitter
can create serious problems, especially in video quality.
It is always preferable for H.323 terminals to be connected to switched type LAN connections to avoid the traffic generated by
terminals being superposed on the normal traffic present on the network.
It is preferable to avoid using NAT-type protocols on router interfaces that route H.323 packets, since NAT protocols often do
not allow the correct routing of connections.
If NAT, firewall or access list implementations are to be used, they must be H.323 compatible.
terminals being superposed on the normal traffic present on the network.
It is preferable to avoid using NAT-type protocols on router interfaces that route H.323 packets, since NAT protocols often do
not allow the correct routing of connections.
If NAT, firewall or access list implementations are to be used, they must be H.323 compatible.
Network Requirements for Multivideoconferences H.323 (MCU)
The same requirements indicated above apply to multipoint connections between more H.323 videoconference terminals.
In this case, more H.323 streams converge in the network, increasing the local network-load. The consequence is that the
bandwidth allocated must be the sum of the bandwidths required for each of the individual connections, calculated according
The same requirements indicated above apply to multipoint connections between more H.323 videoconference terminals.
In this case, more H.323 streams converge in the network, increasing the local network-load. The consequence is that the
bandwidth allocated must be the sum of the bandwidths required for each of the individual connections, calculated according
to the description given in the previous section.
The network requirements previously described are also valid for connections between H.323 and H.320 terminals via
gateways. In this case, more than one H.323 stream converges on the gateway increasing local network traffic. As such, the
necessary bandwidth, at the point where the H.323/H.320 gateway is to be installed, must be the sum of the bandwidths
required for each individual connection, calculated as shown in the previous section.
The network requirements previously described are also valid for connections between H.323 and H.320 terminals via
gateways. In this case, more than one H.323 stream converges on the gateway increasing local network traffic. As such, the
necessary bandwidth, at the point where the H.323/H.320 gateway is to be installed, must be the sum of the bandwidths
required for each individual connection, calculated as shown in the previous section.