1.1.2.3 Uplink Message Delivery-Sequence of Events
1.An uplink message generated by a CAA is addressed and delivered(by the
contracted service provider's network)to the platform hosting the internetworking function.
2.The internetworking function will determine the appropriate service provider for delivery(based on current media advisory information or default delivery preferences).
3.The internetworking function shall address and deliver the message to the appropriate DSP for delivery.If the service provider's own DSP is chosen the message may have TEIs added indicating the correct message path for delivery. If another service provider's DSP is chosen no instructions for message delivery are included in the message.
4.If successful delivery1 is achieved, a Message Delivery Confirmation message shall be returned to the internetworking function. Upon receipt of the Message Delivery Confirmation message the internetworking function shall forward this to the CAA.
5.If delivery is unsuccessful2,either an Untransmittable Message Assurance or an Undeliverable Message Assurance will be returned to the internetworking function.
Receipt of these messages by the internetworking function will result in either;
a)another attempt at message delivery as required by the routing logic in the internetworking function or
b)the Untransmittable Message Assurance or Undeliverable Message Assuarance or being forward to the CAA.
1.1.2.4 Internetworking Function-Operational Scenarios
The uplink routing philosophy mentioned above gives rise to a number of operational scenarios.Although,any number of service providers may support an
internetworked service,in any given instance delivery of uplink messages will only be attempted through two service providers'DSPs.Again it is stressed that the term,"Contracted Service Provider " refers to the Service Provider contracted by the CAA for FANS-1/A datalink service.
1Indicated by receipt of an aircraft ACK as described in ARINC 618.
2Indicated as described in ARINC 618.
