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Configuring the SIP ALG—Quick Configuration

You can use J-Web Quick Configuration to quickly configure SIP ALG Parameters

Figure 59 shows the SIP ALG configuration page.

Figure 59: SIP ALG Configuration

SIP ALG Configuration

To configure the SIP ALG with Quick Configuration:

  1. In the J-Web user interface, select Configure>ALGs>VoIP ALG.
  2. Select the Sip tab if it is not selected.
  3. Fill in the parameter settings as described in Table 170 and click one of the following buttons:

Table 170: SIP ALG Configuraiton Options

Enable SIP ALG

Enables or disables the SIP ALG.

Click the check box.

C Timeout

Specifies the INVITE transaction timeout at the proxy, in minutes; the default is 3. Because the SIP ALG is in the middle, instead of using the INVITE transaction timer value B (which is (64 * T1) = 32 seconds), the SIP ALG gets its timer value from the proxy.

Select a value between 3 and 10 minutes.

Inactive Media Timeout

Specifies the maximum length of time (in seconds) a call can remain active without any media (RTP or RTCP) traffic within a group. Each time an RTP or RTCP packet occurs within a call, this timeout resets. When the period of inactivity exceeds this setting, the temporary openings (pinholes) in the firewall SIP ALG opened for media are closed. The default setting is 120 seconds, the range is from 10 to 2550 seconds. Note that upon timeout, while resources for media (sessions and pinholes) are removed, the call is not terminated.

Select a value between 10 and 2,550 seconds.


Maximum Call Duration

Sets the absolute maximum length of a call. When a call exceeds this parameter setting, the SIP ALG tears down the call and releases the media sessions. The default setting is 720 minutes, the range is from 3 to 7200 minutes.

Select a value between 3 and 7,200 minutes.


T1 Interval

Specifies the roundtrip time estimate, in seconds, of a transaction between endpoints. The default is 500 milliseconds. Because many SIP timers scale with the T1-Interval (as described in RFC 3261), when you change the value of the T1-Interval timer, those SIP timers also are adjusted.

Select a value between 500 and 5,00 milliseconds.


T4 Interval

Specifies the maximum time a message remains in the network. The default is 5 seconds, the range is 5 to 10 seconds. Because many SIP timers scale with the T4-Interval (as described in RFC 3261), when you change the value of the T4-Interval timer, those SIP timers also are adjusted.

Select a value between 5and 10 seconds..


Disable Call ID Hiding

Enables or disable translation of the host IP address in the call-ID header. Translation is enabled by default.

Click the check box.

Retain Hold Resource

Enable or disables whether the device frees media resources for a Session Initiation Protocol (SIP) Application Layer Gateway (ALG), even when a media stream is placed on hold. By default, media stream resources are released when the media stream is held.

Click the check box.

Permit NAT Applied Unknown Message

Specifies how unidentified SIP messages are handled by the device. The default is to drop unknown (unsupported) messages. Permitting unknown messages can compromise security and is not recommended. However, in a secure test or production environment, this statement can be useful for resolving interoperability issues with disparate vendor equipment. By permitting unknown SIP (unsupported) messages, you can get your network operational and later analyze your VoIP traffic to determine why some messages were being dropped.

This statement applies only to received packets identified as supported VoIP packets. If a packet cannot be identified, it is always dropped. If a packet is identified as a supported protocol, the message is forwarded without processing.

Click the check box.

Permit Routed Unknown Message

Specifies that unknown messages be allowed to pass if the session is in Route mode. (Sessions in Transparent mode are treated as Route mode.)

Click the check box.


Specifies the amount of time (in seconds) to make an attack table entry for each INVITE, which is listed in the application screen.

Enter a value between 1 and 3,600 seconds.

Attack Protection

Protects servers against INVITE attacks. Configure the SIP application screen to protect the server at some or all destination IP addresses against INVITE attacks. You can include up to 16 destination IP addresses of servers to be protected.

Select None, All or, if you select Destination IP, enter or select an IP address.

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