ALG Configuration Page Options

Enable DNS

Provides an ALG for the domain name system. The DNS ALG monitors DNS query and reply packets and closes the session if the DNS flag indicates the packet is a reply message.

Select the check box to enable the ALG.

Enable TFTP

Provides an ALG for Trivial File Transfer Protocol. The TFTP ALG processes TFTP packets that initiate a request and opens a gate to allow return packets from the reverse direction to the port that sends the request.

Select the check box to enable the ALG.

Enable REAL

Provides an ALG for RealAudio and RealVideo protocol. The REAL ALG processes Progressive Networks Audio (PNA) packets over the TCP connection and looks for the control commands in the packet where the port number is embedded. It performs NAT and opens gates for the UDP data connection.

Select the check box to enable the ALG.

Enable SUNRPC

Provides a method for a program running on one host to call procedures in a program running on another host. Because of the large number of RPC services and the need to broadcast, the transport address of an RPC service is dynamically negotiated based on the service's program number and version number. Several binding protocols are defined for mapping the RPC program number and version number to a transport address.

Select the check box to enable the ALG.

Enable RTSP

Provides an ALG for the Real-Time Streaming Protocol.

Select the check box to enable the ALG.

Enable TALK

Provides an ALG for the TALK protocol. The TALK protocol uses UDP port 517 and port 518 for control-channel connections. The talk program consists of a server and a client. The server handles client notifications and helps to establish talk sessions. There are two types of talk servers: ntalk and talkd. The TALK ALG processes packets of both ntalk and talkd formats. It also performs NAT and gate opening as necessary.

Select the check box to enable the ALG.

Enable H323 ALG

Enables or disables the H.323 ALG.

Select the check box.

Message Flood Gatekeeper Threshold

Limits the rate per second at which remote access server (RAS) requests to the gatekeeper are processed. Messages exceeding the threshold are dropped. This feature is disabled by default.

Enter a value.

Enable Permit NAT Applied

Specifies how unidentified H.323 (unsupported) messages are handled by the device. The default is to drop unknown 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 H.323 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.

Select the check box.

Enable Permit Media From Any Source Port

Allows media traffic from any port number. By default, this feature is disabled. When enabled, the device allows a temporary opening, or pinhole, in the firewall as needed for media traffic.

Enter a value from 1 through 50,000 seconds.

Enable MGCP

Enables or disables the Media Gateway Control Protocol.

Select the check box.

Maximum Call Duration

Sets the maximum length of a call. When a call exceeds this parameter setting, the MGCP 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 from 3 through 7,200 minutes.

Connection Flood Threshold

Limits the number of new connection requests allowed per Media Gateway (MG) per second. Messages exceeding the ALG.

Enter a value from 2 through 10,000.

Enable Permit NAT Applied

Specifies how unidentified MGCP messages are handled by the Juniper Networks 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 MGCP (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.

Select the check box.

Inactive Media Timeout

Indicates 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 gates opened for media are closed.

Select a value from 10 through 600 seconds.

Call Flood Threshold

Protects SCCP ALG clients from flood attacks by limiting the number of calls they attempt to process

Select a value from 2 through 1,000.

Enable Permit NAT Applied

Specifies how unidentified SCCP 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 SCCP (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.

Select the check box.

Enable Retain Hold Resource

Enables or disables whether the device frees media resources for a SIP, even when a media stream is placed on hold. By default, media stream resources are released when the media stream is held.

Select 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 from 3 through 10 minutes.

Inactive Media Timeout

Specifies the maximum 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 10 through 2550 seconds. Note that, upon timeout, while resources for media (sessions and pinholes) are removed, the call is not terminated.

Select a value from 10 through 2,550 seconds.

Enable Permit Routed

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

Select the check box.

Enable Attack Protection

Protects servers against INVITE attacks. Configures the SIP application screen to protect the server at some or all destination IP addresses against INVITE attacks.

Select All Servers or Selected Servers as the options.