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 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)
*1
•
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.
*1
When the preferred codec of each party differs, the call will be established using the lower codec. For example, if the caller prefers
G.711 while the called party prefers G.729A, the call will be established using G.729A.
Codec
Packet Sending Interval
20 ms
30 ms
40 ms
60 ms
G.722
*1
/G.711
87.2 kbps
79.5 kbps
—
—
G.729A
31.2 kbps
23.5 kbps
19.6 kbps
15.7 kbps
*1
G.722 is only available for calls between KX-NT400/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 IP Extension Card
To allow all IP telephones to make calls simultaneously, it is necessary to keep available the bandwidth required
by an 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 IP extension card.
When using the IP-EXT16 card:
Required Bandwidth = (Required Bandwidth per IP telephone
´
16)
When using the V-IPEXT32/V-SIPEXT32 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
Document Version 2010-08
2.1.1 Bandwidth Assessment
Summary of Contents for KX-NCP500
Page 3: ...Section 1 Introduction Document Version 2010 08 IP Networking Guide 3...
Page 12: ...12 IP Networking Guide Document Version 2010 08 1 3 2 Voice Activity Detection VAD...
Page 13: ...Section 2 Guidance for VoIP Installation Document Version 2010 08 IP Networking Guide 13...
Page 33: ...Section 4 Programming Document Version 2010 08 IP Networking Guide 33...
Page 103: ...Section 5 Appendix Document Version 2010 08 IP Networking Guide 103...
