SN10k Route Retry theory and config
Posted by Michal Podoski, Last modified by Daniel Lizaola on 22 November 2017 01:25 PM
Route Retry algorithm
Route Retry feature is applied when more than one matching route is returned by the active routing script. Algorithm works in the following way:
Call attempt is considered failed in the following conditions:
Route retry timeout can be customized using two parameters:
If the timeout delay is expired before call reaches the specified state, call is considered failed and retry occurs. If the call reaches the minimal state, timeout isn't taken under consideration anymore, but explicit termination from remote side with error cause may still trigger retry with next route.
The 4 states above correspond to the following protocol-specific events:
SIP: Accepted: 100 Trying Progress: 183 with SDP (*) Alerted: 180 Ringing Answered: 200 OK ISDN: Accepted: CALL PROCEEDING Progress: PROG Alerted: ALERTING Answered: CONNECT SS7: Accepted: <none> Progress: CPG Alerted: ACM Answered: CONN/ANM CAS R2: Accepted: SeizureAckCasBit Progress: <none> Alerted: GroupB SuccessDigit Answered: AnswerCasBit
(*) 183 with SDP is usually interpreted as a "ALERT" (not a PROGRESS) unless explicitly configured on NAP level ("
Route Retry termination cause configuration
To control if the route retry algorithm should stop or continue to the next route, each termination cause can be configured in the profile and set to either Continue or Stop.
Configuration is delivered via WebPortal in Profile setup '
Route Retry global configuration
Route Retry mode and timeout parameters can be configured globally, per NAP, or per Route. Configuration precedence takes following order:
The global Route Retry mode and timeout parameters can be found in the SmartMedia WebPortal Gateway application configuration menu:
Route Retry per-NAP configuration
Per-NAP Route Retry mode and timeout parameters are configured by adding a custom 'NAP column':
After creating above columns, each time you create or edit a NAP in NAP Columns menu, Route Retry mode and timeout paramters will be available. In case those are left blank for a particular NAP, global configuration will take precedence. Assigning a value in either of these parameters will override the global value for that parameter.
Route Retry per-route configuration
Per-route Route Retry mode and timeout parameters are configured by adding a custom 'Route column':
After creating above columns, each time you create or edit a Route, Route Retry mode and timeout parameters will be shown under Custom Params. In case those are left blank for a particular Route, global configuration will take precedence. Assigning a value in either of these parameters will override the global value for that parameter.
Customize Route retry parameters from routing script
Any part of the routing script that has access to the route object can read or modify below parameters:
Those fields initially contain values of 'Custom Route Columns' (as explained above), but can be overwritten by the routing script.