1. Essentials Guide
  2. Oracle USM Supporting the IMS Core
  3. Oracle Communications Unified Session Manager as Registrar
  4. Configurable Response to Timed-Out OPTIONS Messages

Configurable Response to Timed-Out OPTIONS Messages

The Oracle Communications Unified Session Manager allows the user to configure a function by which they can cause the system to send a 408 as a response to an OPTIONS message sent to an un-responsive, registered called party. In addition, this function allows the user to specify when to send that 408.

By default, the Oracle Communications Unified Session Manager does not send messages to an originating node when OPTIONS transactions time out. This complies with RFC 4321.

When registered users do not respond to OPTIONS requests, the network never informs the calling party of the called party's status. Instead, the calling party waits for the standard 32-second retry timeout to expire. If the called party was previously reachable, the calling party treats it as reachable for the entire 32-second window.

The Oracle Communications Unified Session Manager includes a configuration option that:

  • Starts a timer when the system forwards an applicable OPTIONS message and,
  • Upon expiry of that timer, causes the system to send a 408 message to the calling party.

This option allows the network administrator to provide the calling party with this 408 response, and specify a shorter interval between request and response.

This feature works for:

  • A called party that is registered via its P-CSCF, but not currently reachable.
  • A called party that is reachable via an IBCF or BGCF.

This function has no impact on requests that result in a response, such as SIP 480, for un-registered subscribers.

For registered users with multiple contacts, the Oracle Communications Unified Session Manager uses a response from any contact as a trigger to stop the timer and not send a 408. The Oracle Communications Unified Session Manager cancels all remaining OPTIONS transactions when it receives a response from a contact. In addition, if the system used parallel forking to reach multiple contacts, it waits for the timer expiry before it sends the 200OK to the caller.

The option is available via S-CSCF processing and, as such, is available on both the Oracle USM and Oracle CSM products. There is, however, one operational difference between the Oracle USM and Oracle CSM. If the called party finally responds after this timer expires and the S-CSCF logic has sent the 408, the Oracle USM drops the response, whereas the Oracle CSM forwards it to the originating node.

The user sets the option globally in sip-config or on a sip-interface, with the sip-interface taking precedence. Values range from 1 to 32 seconds. Invalid ranges cause the system to use the maximum value of 32. The example below sets a sip-interface's timer to 4 seconds. 

ORACLE(session-router)#sip-interface
ORACLE(sip-interface)#options +options-408-timeout=4

Option syntax on the sip-config and sip-interface configuration elements is the same.

The user must consider the infrastructure carefully. Setting the value too low can cause an inordinate number of invalid 408 responses.