Reliable (TCP/TLS) Connections

For the maximum number of concurrent TLS connections supported by the device, refer to the Release Notes.

Reliable connection reuse depends on the [EnableTCPConnectionReuse] parameter. For incoming connections, reuse also depends on SIP message characteristics (presence of Via header’s ‘alias’ parameter in initial request) and the [FakeTCPalias] parameter.

Persistent connections are determined by the [ReliableConnectionPersistentMode] parameter. However, if the destination is a Proxy server (configured in the Proxy Sets table), the connection is always persistent, regardless of the parameter's settings.

The device releases unnecessary persistent TLS connections to prevent them from accumulating and reaching the device's maximum number of supported TLS connections. If the number of incoming TLS connections exceeds 80% of the maximum, the device closes incoming TLS connections that aren’t in use and that are kept open only because they are persistent. Similarly, the device releases reliable (TCP/TLS) connections that aren’t in use (i.e., no active SIP dialogs and not associated with a registered user) and are kept open only because they are persistent, when exceeding 80% of the maximum number of supported reliable connections.

The device sends the SNMP alarm acTLSSocketsLimitAlarm (OID 1.3.6.1.4.1.5003.9.10.1.21.2.0.159) when the number of incoming TLS connections exceeds 95% of the maximum TLS connections supported by the device.