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9.1 Scope of Work
The following scope of work describes the interpretation of the requirements into development components.
9.1.1 Reliable Messaging
Reliable Messaging is a base feature of the DMS. The purpose of the Reliable Messaging feature is to ensure that messages sent to and from the aircraft client are delivered in full,
in the presence of software component, system, or network failures. If a message fails to be delivered for any reason, the DMS must understand that the client has not received the
message. The DMS must take action to reattempt delivery of the undelivered message to the client aircraft. Part of the DMS Reliable Messaging feature is the ability of the DMS
to handle breaks in communication to the client aircraft. Breaks in communication will occur when an aircraft client switches between communication networks or loses
connectivity to a communication network for any other reason. The DMS must have the ability to communicate with the aircraft client through all accepted communication
networks. Any data that is lost while being transmitted to the aircraft client due to the aircraft client switching between data networks must be understood by the DMS as not
been received by the client. The DMS must attempt retransmission of the data to the aircraft client after connection is re-established to ensure reception of the data by the
client aircraft. This also applies in the aircraft to DMS direction, where the Client DMS Component needs to make sure that DMS receives all sent messages, irrespective of any
failures.
The Reliable Messaging feature must be able to determine whether or not an aircraft client has received the message that has been sent to the client aircraft.
The Reliable Messaging feature must attempt to retransmit any data that was sent to the aircraft client but not received by the client aircraft.
9.1.2 Dispatch Module
The Dispatch Module is a service module of the DMS. The Dispatch Module purpose is to allow a non-aircraft client known in this document as “client dispatch” to receive a
full or abbreviated copy of the messages the aircraft client receives. The dispatch client has the option of requesting an abbreviation of the messages received by the client from
the DMS. The purpose of having the dispatch client request abbreviated messages t, instead of automatically sending the dispatch client the full message, is to conserve
network resources
The Dispatch Module must send the dispatch client messages containing the type
of data or the whole message received by the aircraft client after the aircraft client has confirmed the reception of the message.
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9.2 Recommended Approach