Changing the STI-VS Trigger

To optimize processing and reduce unnecessary traffic, you can set the sti-vs-post-check option on the sti-config configuration element to determine when the SBC triggers STI-VS processing.

By default, sti-vs-post-check is set to disabled. In this configuration, the SBC triggers STI-VS processing after ingress Header Manipulation Rules (HMR) processing but before checking session constraints. This sequence of operations may lead to the system triggering STI-VS exchanges before the session constraints are evaluated, resulting in unnecessary processing on both the SBC and the STI server, and generating additional, often avoidable traffic processing.

When you set sti-vs-post-check to enabled, the SBC triggers STI-VS processing after checking session constraints.

Default call processing stages (when sti-vs-post-check is set to disabled):

1. SIP message parsing
2. Denial of Service (DoS) handling (including CPU load monitoring, message parsing, access control, and constraints)
3. Inbound HMR (Header Manipulation Rules)
4. Load Index (LI) processing
5. STIR-VS processing
6. Check session constraints

To enable sti-vs-post-check:

1. Access the sti-config configuration element:

   ORACLE# configure terminal
   ORACLE(configure)# session-router
   ORACLE(session-router)# sti-config
   ORACLE(sti-config)#

2. Set the sti-vs-post-check option to enabled:

   ORACLE(sti-config)# options +sti-vs-post-check=enabled

3. Save and activate your configuration.

Call processing stages after enabling sti-vs-post-check:

1. SIP message parsing
2. Denial of Service (DoS) handling (including CPU load monitoring, message parsing, access control, and constraints)
3. Inbound HMR (Header Manipulation Rules)
4. Load Index (LI) processing

   (Steps 5 and 6 are reversed.)

5. Check session constraints
6. STIR-VS processing