Retry mechanism is enabled for every SI server for redundancy purpose. While sending SMS campaigns, if any campaign due to following reasons could not reach out to the customers, then Retry mechanism takes place.
- Switch level errors
- Network congestion issues
- Operator congestion issues
- Subscriber Device Issues
Basically, SMSC is responsible for the relaying, storing and forwarding of a short message between an SME and operator. SMSC is notified of the message status through MAP operations.
SMSC will go into a retry schedule, attempting to periodically deliver the message without getting an alert. The retry schedule interval will depend on the original failure cause - transient network failures will result in short retry schedule, whereas out of coverage will typically result in a longer schedule.