Understanding SCCP ALG Unknown Message Types

To accommodate on-going development of the Skinny Client Control Protocol (SCCP), you might want to allow traffic containing new SCCP message types. The unknown SCCP message type feature enables you to configure the device to accept SCCP traffic containing unknown message types in both Network Address Translation (NAT) mode and route mode.

This feature enables you to specify how unidentified SCCP messages are handled by the device. The default is to drop unknown (unsupported) messages. We do not recommend permitting unknown messages because they can compromise security. However, in a secure test or production environment, this command can be useful for resolving interoperability issues with disparate vendor equipment. Permitting unknown SCCP messages can help you get your network operational so that you can later analyze your voice-over-IP (VoIP) traffic to determine why some messages were being dropped.

Note that this command 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 and you have configured the device to permit unknown message types, the message is forwarded without processing.

Related Topics

• JUNOS Software Feature Support Reference for SRX Series and J Series Devices
• Understanding SCCP ALGs
• SCCP ALG Configuration Overview
• Example: Allowing Unknown SCCP ALG Message Types (J-Web)
• Example: Allowing Unknown SCCP ALG Message Types (CLI)