SIP Registration Duration Check


As a SIP Registrar, the CSP SIP stack is subject to SIP Register requests from a diverse set of endpoints. Some of these endpoints might try to refresh registrations frequently enough to cause processor and memory overload conditions on the CSP Matrix Series 3 Card card or host application.

SIP specification RFC 2543 recommend that an endpoint that tries to register for an expiration interval less than the Registrarís configurable minimum threshold can be denied with a SIP 423 response (Interval Too Brief).

Prior to this feature, the SIP stack acted as a pass-through for all REGISTER requests. Because of this scenario, the host application was involved with the PPL Event Request handshake to generate the SIP 423 response.

Pertinent Specification

RFC 2543


This feature allows you to set a minimum registration duration threshold in the SIP stack configuration. The SIP REGISTER message that requests a lower expiration duration than the minimum duration configured is automatically rejected by the CSP with the SIP 423 response code.

The SIP 423 response generated by the CSP contains a Min-Expires header field filled with the lowest registration duration acceptable to the registrar. By being able to configure the minimum registration duration threshold, you eliminate potential processor and memory overload conditions.


This feature is enabled (that is, a check for minimum registration duration is made) only when you include the Minimum Registration Duration (0x0283) TLV in the VoIP Protocol Configure (0x00EE) message. Once enabled, to disable this feature, set the duration to a significantly low value.

Refer to the API Reference.


You can query the Registration Minimum Duration (0x0283) with the VoIP Protocol Query (0x00EF) message.