
Four Channel’s GSM VoIP Gateway
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3.4.4 Codec Preference
Codec Preference allows a user to select the codes to be used and its priority to be
selected for a voice call.
Click on the check box to enable a codec. Select a codec and then press the UP or
DOWN button to move the position of the codec on the codec list with a priority in
descending order.
Note: The voice code alaw and ulaw is G.711a and G.711u.
3.4.5 NAT Traversal
3.4.5.1 Signaling NAT Traversal
Signaling NAT traversal may be required if the GoIP_4 Gateway is put behind a NAT
(or multiple NATs). Depending on your network environment and SIP Server
capabilities, this feature may or may not be turn on.
A
)
None
Select None to turn off this feature.
B
)
STUN (RFC 3489)
STUN (Simple Traversal of UDP (User Datagram Protocol) through NATs (Network
Address Translators)) is a network protocol allowing a client behind a NAT (or
multiple NATs) to find out its public address, the type of NAT it is behind and the
internet-side port associated by the NAT with a particular local port.
Select STUN (RFC 3489) to use a STUN server for Signaling NAT Traversal. Enter the
IP Address or the domain name of the STUN server to be used.
C
)
Relay Proxy
Relay proxy is a proprietary NAT traversal technology. Please consult your service