Router Requirements
•
Port Forwarding:
It may be necessary to set the NAT router so that it forwards the incoming packets to the IP address of the
V-SIPGW16 card if all of the following conditions are met:
–
the PBX uses a STUN server;
–
a V-SIPGW16 card is located under a NAT router;
–
incoming packets are routed to a SIP Client port or NAT Voice (RTP) UDP port indicated in the
[IP
Packets to V-SIPGW16 Card]
table above.
•
SIP-NAT Feature:
When a V-SIPGW16 card is located under a NAT router that supports the SIP-NAT feature
*1
, it is
recommended to disable this feature.
*1
When NAT is enabled, the router translates the IP address stored in the IP header and the port number stored in the UDP header.
When SIP-NAT is enabled, the router also translates the IP address and port number stored in SIP messages.
1.2.3 Bandwidth Requirements
When using the V-SIPGW16 card, you must ensure that the WAN has enough bandwidth to support VoIP
communications. Refer to the table below and ensure that the sum of the required bandwidth for each channel
is smaller than the amount the WAN (e.g., ADSL network) can provide.
Note that the amount in the table is only a guide. Subscribe to a network that has enough bandwidth. If the
amount of bandwidth required for VoIP communications is larger than what the network can accommodate,
speech quality will be compromised.
Required Bandwidth for Each Channel
The required bandwidth depends on what combination of CODECs and packet sending interval 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 CODECs varies as follows: G.711 (High), G.729 (Low)
•
The shorter the packet sending interval, the higher the speech quality.
•
The higher the speech quality the V-SIPGW16 card provides, the more bandwidth the WAN requires.
CODEC
Packet Sending Interval
10 ms
20 ms
30 ms
40 ms
50 ms
60 ms
G.711
110.4 kbps
87.2 kbps
79.5 kbps
75.6 kbps
73.3 kbps
71.7 kbps
G.729
54.4 kbps
31.2 kbps
23.5 kbps
19.6 kbps
17.3 kbps
15.7 kbps
8
Programming Manual for Virtual SIP CO Line Card
Document Version 2008-11
1.2.3 Bandwidth Requirements
