A1 VoIP Requirements
Getting Started 53
Required Bandwidth for Fax Communication
Via LAN
Via WAN (PPP: Point-to-Point Protocol)
Example
Consider the following case as an example:
• Communication: via LAN
• No. of Fax Machines: 1
• Required Bandwidth for Fax Communication: 75.6 kbps
• Required Bandwidth for Voice Communication: 23.5 kbps
In this case, the required bandwidth will be as follows:
Therefore, inform your network administrator and make sure that the network can support a
bandwidth of 146.1 kbps even when the network is under conditions of maximum traffic.
Note
It is recommended that all VoIP Gateway Cards in a VoIP network have the same packet
sending interval.
A1.2 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 taken into your evaluation.
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—that is, the Internet—cannot be used to employ a VoIP network
because delays and loss in data transmission can cause huge degradation in speech quality.
FAX High Reliable Method
G.711 Packet Sending Interval
20 ms 30 ms 40 ms
Don’t Use 87.2 kbps 79.5 kbps 75.6 kbps
Use 224.8 kbps 213.9 kbps 208.4 kbps
FAX High Reliable Method
G.711 Packet Sending Interval
20 ms 30 ms 40 ms
Don’t Use 84 kbps 77.3 kbps 74 kbps
Use 221.6 kbps 211.7 kbps 206.8 kbps
Required Bandwidth
= (1 × 75.6) + (3 × 23.5)
= 146.1
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