Panasonic Hybrid IP-PBX, Руководство пользователя

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2.1 VoIP Requirements
12 Information about IP Proprietary Telephones
2.1 VoIP Requirements
2.1.1 Bandwidth Assessment
When using IP-PTs, 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 larger 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.
Required Bandwidth per IP-PT for a Call
The required bandwidth depends on what combination of CODEC and packet sending interval is used. Keep
in mind the following points about the type of CODEC and packet sending interval, in terms of 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 IP-PTs provide, the more bandwidth the IP-PTs require.
Required Bandwidth for Each IP-EXT16 Card
To allow all IP-PTs to make calls simultaneously, it is necessary to keep available the bandwidth required
by an IP-EXT16 card with the maximum number of IP-PTs connected.
Provided below is the formula to calculate the amount of bandwidth required for each IP-EXT16 card.
2.1.2 Network Configuration
You must evaluate the structure of the existing network to see if a VoIP network can be implemented. Below
are the points that should be evaluated.
Is the IP network a managed network?
A VoIP network should be implemented on a managed IP network such as Frame Relay, Leased Line, or
IP-VPN (Virtual Private Network).
An unmanaged network, such as the Internet (including an Internet VPN), cannot be used to employ a VoIP
network because delays and loss in data transmission can cause huge degradation in speech quality.
CODEC
Packet Sending Interval
20 ms 30 ms 40 ms 60 ms
G.711 87.2 kbps 79.5 kbps — —
G.729a 31.2 kbps 23.5 kbps 19.6 kbps 15.7 kbps
Required Bandwidth
= (Required Bandwidth per IP-PT × 16)