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User’s Guide
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APPENDIX F
SIP Passthrough
Enabling/Disabling the SIP ALG
You can turn off the WiMAX Modem SIP ALG to avoid retranslating the IP address
of an existing SIP device that is using STUN. If you want to use STUN with a SIP
client device (a SIP phone or IP phone for example) behind the WiMAX Modem,
use the ip alg disable ALG_SIP command to turn off the SIP ALG.
Signaling Session Timeout
Most SIP clients have an “expire” mechanism indicating the lifetime of signaling
sessions. The SIP UA sends registration packets to the SIP server periodically and
keeps the session alive in the WiMAX Modem.
If the SIP client does not have this mechanism and makes no call during the
WiMAX Modem SIP timeout default (60 minutes), the WiMAX Modem SIP ALG
drops any incoming calls after the timeout period. You can use the ip alg
siptimeout command to change the timeout value.
Audio Session Timeout
If no voice packets go through the SIP ALG before the timeout period default (5
minutes) expires, the SIP ALG does not drop the call but blocks all voice traffic
and deletes the audio session. You cannot hear anything and you will need to
make a new call to continue your conversation.