Voip Requirements; Bandwidth Assessment - Panasonic KX-NCP500 Manual

2.1.1 Bandwidth Assessment

2.1 VoIP Requirements

2.1.1 Bandwidth Assessment
When using the IP telephones and V-IPGW16 card, you must ensure that the IP network in use has enough
bandwidth to support VoIP communications. If the amount of bandwidth required for VoIP communications is
more than the network can accommodate, speech quality will be compromised. In addition, there may be an
adverse effect on the performance of other applications (e.g., email or web applications) that use the same
network. Therefore, care must be taken when assessing bandwidth requirements.
Inform your network administrator of the required bandwidth, and make sure that the network can support VoIP
communications even under conditions of maximum network traffic.
Bandwidth Assessment for Virtual IP Extension Card
Required Bandwidth per IP telephone for a Call
The required bandwidth depends on what combination of codecs and packet sending intervals is used. Keep
in mind the following points about the type of codecs and packet sending intervals, in terms of speech quality:
•
The speech quality of the codecs varies as follows: (High) G.722, G.711, G.729A (Low)
•
The shorter the packet sending interval, the higher the speech quality.
•
The higher the speech quality the IP telephones provide, the more bandwidth the IP telephones require.
When the preferred codec of each party differs, the call will be established using the lower codec. For example, if the caller prefers
*1
G.711 while the called party prefers G.729A, the call will be established using G.729A.
Codec
G.722 /G.711
*1
G.729A
*1 G.722 is only available for the KX-NT300 series IP-PTs and some SIP Extensions that support this codec during peer-to-peer
communication. For details, refer to "13.1.8 Peer-to-Peer Connection" in the Feature Manual.
Required Bandwidth for Each Virtual IP Extension Card
To allow all IP telephones to make calls simultaneously, it is necessary to keep available the bandwidth required
by a virtual IP Extension card with the maximum number of IP telephones connected.
Provided below is the formula to calculate the amount of bandwidth required for each virtual IP Extension card.
Required Bandwidth = (Required Bandwidth per IP telephone ´ 32)
Bandwidth Assessment for V-IPGW16 Card
Required Bandwidth for One VoIP Channel
The required bandwidth depends on what combination of codecs and packet sending intervals is used. Keep
in mind the following points about the type of codec and packet sending interval, in terms of the speech quality:
•
The speech quality of the G.711 codec is higher than that of the G.729A codec.
•
The shorter the packet sending interval, the higher the speech quality.
•
The higher the speech quality the V-IPGW16 card provides, the more bandwidth the card requires.
14 IP Networking Guide
20 ms
87.2 kbps 79.5 kbps
31.2 kbps 23.5 kbps
Packet Sending Interval
30 ms 40 ms
—
19.6 kbps
*1
60 ms
—
15.7 kbps
Document Version 2009-12