RFC 5635 Failure

The Oracle Communications Unified Session Manager supports the RFC 5635 method of SIP application keepalives, which are endpoint-initiated, i.e., the endpoint starts the mechanism by including the keep parameter in the initial Via: header. Endpoint reachability is determined the receipt or loss of a CR/LF ping-pong message. In the SIP interface configuration element, you set the register keep alive parameter to always or bnat (behind NAT), to enable RFC 5635 functionality. This applicable to TCP or TLS connections. Always forces the Oracle Communications Unified Session Manager to always return a CRLF reply when the keep parameter is in the initial Via: header. bnat forces the Oracle Communications Unified Session Manager to replies to RFC 5635 requests when the endpoint is located behind a NAT.

Next, you can accept the Oracle Communications Unified Session Manager’s default keep alive window of 30 seconds, or you may set your own by configuring the tcp nat interval or inactive con timeout value, both found in the sip interface configuration element. The Oracle Communications Unified Session Manager uses the smaller of the two configured values. The chosen value is inserted into the keep parameter in the 200 OK message returned to the registering endpoint.

Note:

The inactive con timeout value otherwise disconnects a TCP/TLS connection after the configured value elapses. The tcp nat interval value is also inserted into the expires parameter in the Contact: header for devices identified as behind a NAT.

In addition, the Oracle Communications Unified Session Manager maintains a keep timer. The Oracle Communications Unified Session Manager adds 31 seconds to the keep value it returns and begins counting down. 31 is the chosen margin to account for any network or application delay.

If the endpoint returns the CRLF before the timer expires, the endpoint is considered up and a new CRLF ping is sent to the endpoint; the timer begins counting down again. If the Oracle Communications Unified Session Manager fails to receive the CRLF ping before the timer expires, then the UA is considered unreachable. Provisions begin to remove that contact from the registration cache and then the ENUM user database.