ZyXEL Communications USG 2000 User Manual

Chapter 21 ALG

ZyWALL USG 2000 User’s Guide

The following table describes the labels in this screen. 

 

 

Table 101   Configuration > Network > ALG

Enable SIP ALG

Turn on the SIP ALG to detect SIP traffic and help build SIP sessions 
through the ZyWALL’s NAT. Enabling the SIP ALG also allows you to 
use the application patrol to detect SIP traffic and manage the SIP 
traffic’s bandwidth (see 

).

Enable SIP 
Transformations

Select this to have the ZyWALL modify IP addresses and port numbers 
embedded in the SIP data payload. 

You do not need to use this if you have a SIP device or server that will 
modify IP addresses and port numbers embedded in the SIP data 
payload.

Enable Configure 
SIP Inactivity 
Timeout

Select this option to have the ZyWALL apply SIP media and signaling 
inactivity time out limits. 

SIP Media 
Inactivity 
Timeout

Use this field to set how many seconds (1~86400) the ZyWALL will 
allow a SIP session to remain idle (without voice traffic) before 
dropping it.

If no voice packets go through the SIP ALG before the timeout period 
expires, the ZyWALL deletes the audio session. You cannot hear 
anything and you will need to make a new call to continue your 
conversation.

SIP Signaling 
Inactivity 
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 ZyWALL. 

If the SIP client does not have this mechanism and makes no calls 
during the ZyWALL SIP timeout, the ZyWALL deletes the signaling 
session after the timeout period. Enter the SIP signaling session 
timeout value (1~86400).

SIP Signaling 
Port 

If you are using a custom UDP port number (not 5060) for SIP traffic, 
enter it here. Use the Add icon to add fields if you are also using SIP 
on additional UDP port numbers.

Enable H.323 
ALG

Turn on the H.323 ALG to detect H.323 traffic (used for audio 
communications) and help build H.323 sessions through the ZyWALL’s 
NAT.  Enabling the H.323 ALG also allows you to use the application 
patrol to detect H.323 traffic and manage the H.323 traffic’s 
bandwidth (see 

).

Enable H.323 
Transformations

Select this to have the ZyWALL modify IP addresses and port numbers 
embedded in the H.323 data payload. 

You do not need to use this if you have a H.323 device or server that 
will modify IP addresses and port numbers embedded in the H.323 
data payload.

H.323 Signaling 
Port 

If you are using a custom TCP port number (not 1720) for H.323 
traffic, enter it here. 

Additional H.323 
Signaling Port  
for 
Transformations

If you are also using H.323 on an additional TCP port number, enter it 
here.