User manual

VOPTech Document Four Channel’s GSM VoIP Gateway

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 GoIP4 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

provider for more information.