ASCOM Ascotel AIP 6350, Системное руководство

Страница: 43 / 64

AIP 6350 / Office 35IP
Network Environment 43
6.3 Bandwidth Control
The maximum number of call connections possible simultaneously can be limited
using AIMS to ensure that the maximum number of call connections set up does
not exceed the available bandwidth.
The amount of bandwidth required by a call connection depends on the voice
compression method. This method can be set for each individual IP terminal by
selecting the correspond codec. The selected codec determines the bandwidth
necessary for each call connection.
Tab. 18: Codecs supported and their bandwidth requirements
As the bandwidth size available in the IP network is not the same everywhere, IP
terminals can be grouped into areas with the same bandwidth. The number of call
connections can be limited for each area. Once the limit is reached, no further
connections are permitted. The caller will obtain the congestion tone.
Note:
To optimise the available bandwidth, the same codec should be used for
IP terminals within a given bandwidth area.
Note:
Prioritised voice packets on a WAN link with tight design limits can slow
down the data traffic to intolerable levels. For this reason sufficient
bandwidth has to be included in the calculations when designing the
maximum number of voice channels.
Codec Bandwidth voice Effective bandwidth (without IP header compression)
in relation to the frame length Speech quality
10 ms 20 ms 30 ms
G0.711 64 kbit/s 111 kbit/s 90 kbit/s 80 kbit/s max. 4.5 MOS
G.729 8 kbit/s 55 kbit/s 32 kbit/s 24 kbit/s max. 4 MOS
G.711 is uncompressed, has small delay values (provided a small frame length has been set) and a high
speech quality (the MOS scale ranges from 1 to 5). This codec should be given priority whenever there is
sufficient bandwidth available. If the bandwidth is limited, G.729 is used to advantage.