Configurable threshold for SIP message rates per request method. Protects SIP servers from SIP overload and DoS attacks.

FortiGate units support rate limiting for the following types of VoIP traffic:

You can use rate limiting of these VoIP protocols to protect the FortiGate unit and your network from SIP and SCCP Denial of Service (DoS) attacks. Rate limiting protects against SIP DoS attacks by limiting the number of SIP REGISTER and INVITE requests that the FortiGate unit receives per second. Rate limiting protects against SCCP DoS attacks by limiting the number of SCCP call setup messages that the FortiGate unit receives per minute.

You configure rate limiting for a message type by specifying a limit for the number of messages that can be received per second. The rate is limited per security policy. When VoIP rate limiting is enabled for a message type, if the a single security policy accepts more messages per second than the configured rate, the extra messages are dropped and log messages are written when the messages are dropped.

Use the following command to configure a VoIP profile to limit the number of INVITE messages accepted by each security policy that the VoIP profile is added to 100 INVITE messages a second:

If you are experiencing denial of service attacks from traffic using these VoIP protocols, you can enable VoIP rate limiting and limit the rates for your network. Limit the rates depending on the amount of SIP and SCCP traffic that you expect the FortiGate unit to be handling. You can adjust the settings if some calls are lost or if the amount of SIP or SCCP traffic is affecting FortiGate unit performance.

Table 110 lists all of the VoIP profile SIP rate limiting options. All of these options are set to 0 so are disabled by default.