Message routing has much in common with Telephony routing.
However there are several differences.
Unlike Telephony, where routing occurs by E.164 destination code, for message routing E.212 codes are used, also known as MCC-MNC codes.
MCC-MNC codes are used for message exchange, because more than 50% of mobile subscribers over the world use Number portability service, and E.164 phone number no longer identifies operator, to which subscriber is connected.
To decrease cost of message delivery, it's more feasible to route message to operator, to which subscriber is connected at the moment, and not to operator which E.164 code is used in subscriber's number.
That's why routing is based on MCC-MNC codes.
Routing system supports Transformation of E.164 number to MCC-MNC code to fulfill correct message routing.