ZyXEL Communications NBG410W3G - Manual (Page 296)

Chapter 18 ALG Screen
NBG410W3G Series User’s Guide
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18.5.2 SIP ALG Details
• SIP clients can be connected to the LAN or DMZ. A SIP server must be on the WAN.
• You can make and receive calls between the LAN and the WAN, between the DMZ and
the WAN. You cannot make a call between the LAN and the LAN, between the LAN and
the DMZ, between the DMZ and the DMZ, and so on.
• The SIP ALG allows UDP packets with a port 5060 destination to pass through.
• The ZyXEL Device allows SIP audio connections.
The following example shows SIP signaling (1) and audio (2) sessions between SIP clients A
and B and the SIP server.
Figure 184 SIP ALG Example
18.5.3 SIP Signaling Session Timeout
Most SIP clients have an “expire” mechanism indicating the lifetime of signaling sessions.
The SIP user agent sends registration packets to the SIP server periodically and keeps the
session alive in the ZyXEL Device.
If the SIP client does not have this mechanism and makes no calls during the ZyXEL Device
SIP timeout default (60 minutes), the ZyXEL Device SIP ALG drops any incoming calls after
the timeout period.
18.5.4 SIP 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.
18.6 ALG Screen
Click ADVANCED > ALG to open the ALG screen. Use the ALG screen to turn individual
ALGs off or on and set the SIP timeout.
A
1
2
B