A mismatch can occur on the connections between an AGW and an RTR. This article explains the reason for this mismatch.
The different number of sessions depends on the session model. The following session models are the most relevant to an AGW configuration:
- Replicate: When the first outside session is set up by the application, the HUB sets up inside sessions for all SMSCs. Subsequent outside sessions only trigger additional inside sessions if the “capacity” of the existing inside sessions is lower than that of the outside sessions.
- Distribute: When an application sets up an outside session, the HUB sets up an inside session for one SMSC (unless the “capacity” requires more inside sessions, e.g., when the inside/outside window size differs). A subsequent inside session is set up to another SMSC. The HUB attempts to distribute the inside sessions evenly over the SMSCs.
The capacity is calculated based on window sizes. For example, if the outside window size is 2 and the inside window size is 10, one inside session can handle the traffic from 5 outside sessions. The following calculation determines if a new inside session will be created when a new outside session is established:
- outside session capacity = # of outside sessions * outside window size
- inside session capacity = # of inside sessions * inside window size
In general, the replicate session model is recommended for applications in an AGW configuration, as it makes an SMS application reachable from every SMSC, which allows MO-AT routing.
- When a new outside session makes the outside session capacity greater than the inside session capacity, then a new inside session will be triggered.
- If a new outside session leaves the outside session capacity less than or equal to the inside session capacity, then no new inside sessions will be established.