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STANAG 5066: PROFILE FOR MARITIME HF DATA COMMUNICATION
V1.0.2
The sending peer retrieves Client U_PDUs from its Queues (according to Priority and/or
other criteria), encodes them into appropriate DATA S_PDUs and sends them to its peer at
the remote end of the Link. A S_PDUs is submitted to the Channel Access Sublayer as a
C_UNIDATA_REQUEST Primitive of the appropriate priority or as a
C_EXPEDITED_UNIDATA_REQUEST Primitive, depending upon whether the encoded
U_PDU was submitted as a S_UNIDATA_REQUEST or as a
S_EXPEDITED_UNIDATA_REQUEST Primitive by the Client.
The Receiving Peer decodes the S_PDU and extracts from it the U_PDU, the Destination
SAP_ID and the other encoded attributes described in Figure A-4. The U_PDU is then
delivered to the Destination Client as a S_UNIDATA_INDICATION Primitive or as a
S_EXPEDITED_UNIDATA_INDICATION Primitive, depending upon whether the received
S_PDU was submitted by the Channel Access Sublayer as C_UNIDATA_INDICATION
Primitive or C_EXPEDITED_UNIDATA_INDICATION Primitive. If the received S_PDU
has the “CLIENT DELIVERY CONFIRM REQUIRED” field set equal to “YES”, then the
Receiving Peer must respond with either a “DATA DELIVERY CONFIRM” S_PDU (type 1)
or a “DATA DELIVERY FAIL” S_PDU (type 2) depending upon whether the U_PDU was
successfully delivered to the destination Client or not. Normally these response S_PDUs
should have the same Priority (or be of “Expedited” format) as the DATA S_PDU that
caused them. However, as the Priority of these Response S_PDUs does not affect
interoperability, it is left as an implementation issue.
It should be noted that, as shown in Figure A-3, there is no explicit indication that the
S_PDU is a “normal” or an “expedited” one. The reason for this is that the underlying
sublayers are expected to treat Expedited S_PDUs differently and implicitly pass the
information to the receiving peer by (for example) delivering Expedited S_PDUs as
C_EXPEDITED_UNIDATA_INDICATION Primitives rather than normal
C_UNIDATA_INDICATION Primitives.
The procedures for exchanging DATA S_PDUs for both the Sending and Receiving Peers are
shown in Figure A-7.
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