Mission Operations Reference Model. Draft ... - CCSDS

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DRAFT RECOMMENDED PRACTICE FOR MISSION OPERATIONS REFERENCE MODEL4.4.2 MESSAGE RECEPTION SEQUENCEFigure 4-9 shows the message reception sequence for the MAL. It includes the error cases asalternative fragments.Transport LayerMALAccess ControlMO Service LayerReceive messagePre-check messagealt MAL Check FailureTransmit check erroralt If message from a ProviderPass check error message upwardsCheck messagealt Access Control FailureTransmit Access Control errorReturn Access Control erroralt If message from a ProviderPass Access Control error message upwardsReturn updated messageStore message transaction detailsPass message upwardsalt Service FailureReturn Service errorTransmit Service errorFigure 4-9: MAL Reception SequenceThe basic outline of this sequence from the high-level sequence (figure 4-3) is that the MALreceives messages from the Transport layer and passes them up to the relevant MO ServiceLayer.a) The Transport layer passes the message to the MAL using the MAL’s abstractTransport service interface.b) The MAL checks the contents of that message to ensure that it contains all therequired aspects for the MAL itself. If it fails these checks, then an error istransmitted to the Transport layer unless the message is itself an error message.c) If the message fails the check and is from a provider (determined by examining theinteraction pattern stage fields of the message), then an error message is sent to thetransaction source. The transaction details are removed from the Transaction Store.<strong>CCSDS</strong> 520.1-R-1 Page 4-11 October 2009
DRAFT RECOMMENDED PRACTICE FOR MISSION OPERATIONS REFERENCE MODELd) If there was an error, then the sequence ends at this point.e) The MAL then submits the message to the Access Control component using itsabstract service interface. The rules that the access control component applies aredeployment specific.f) If the Access Control component rejects the message, then it returns an error to theMAL. If the message is not an error, then the MAL creates the relevant AccessControl message and passes this to the Transport layer for transmission.g) If the message is from a provider (determined by examining the interaction patternstage fields of the message), then the Access Control error message is also sent to thetransaction source. The transaction details are removed from the Transaction Store.h) If there was an error, then the sequence ends at this point.i) If the Access Control component accepts the message, then it returns the message(with updated security credentials, if applicable) to the MAL.j) The MAL then stores the transaction details if this is the first message being sent fromthe consumer. If it is a return message from a provider, then the transaction details areremoved from the store if it is the final message for that interaction pattern.k) The MAL then submits the message to the relevant MO Service Layer aspect.l) If the higher layer encounters an error during its processing off the message, then itreturns an error to the MAL. If the sender of the message is a consumer and the sentmessage is not an error, then the MAL uses the Active Transaction Store to build areturn error message to be transmitted to the sending application. If it is a provider,then an application error is returned to the provider. The sequence then ends.<strong>CCSDS</strong> 520.1-R-1 Page 4-12 October 2009
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