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STANAG 5066: PROFILE FOR MARITIME HF DATA COMMUNICATION
V1.0.2
The establishment of a Soft Link Data Exchange Session is initiated unilaterally by the
Subnetwork Interface Sublayer which has queued ARQ U_PDUs and from which a client has
not requested a Hard Link Data Exchange Soft Link Data Exchange Sessions shall be
initiated as needed, following the procedure described in Section A.3.2.1. When the data for
this node has been transmitted, the session is terminated immediately or after a suitable timeout
period (the time out period would allow for the possibility of new U_PDUs which can be
serviced by the existing soft link session). The procedure for terminating a Soft Link Data
Exchange Session is described in Section A.3.2.1.2. In order to provide “balanced” servicing
of the queued U_PDUs, a Soft Link Data Exchange Session should not be maintained for a
period which exceeds a specified maximum time if U_PDUs of appropriate priorities are
queued for different node(s). The specific values of the parameters governing the
establishment and termination of Soft Link Data Exchange Sessions (e.g. time-out periods
etc.) must be chosen in the context of a particular configuration (i.e. size of network, etc).
A.1.1.2
Hard Link Data Exchange Session
The second type of data exchange session is the Hard Link Data Exchange Session. This
session is initiated at the explicit request of a client. A client can request a hard link in order
to ensure that a physical link to a specified node is maintained (irrespective of the
destinations of other queued U_PDUs) and optionally to partially or fully reserve the capacity
of this link. The procedures for establishing and terminating hard link sessions are described
in Sections A.3.2.2.1 and A.3.2.2.2.
A.1.1.3 Broadcast Data Exchange Session
• The third type of data exchange session is the Broadcast Data Exchange Session.
During this session only non-ARQ U_PDUs can be serviced. A Broadcast Data
Exchange Session can be initiated and terminated by a management process, e.g..
a local or network administrator management client. A node configured to be a
broadcast-only node is put in a “permanent” Broadcast Data Exchange Session
during which no hard link requests or ARQ Data U_PDUs can be serviced.
Alternatively the Subnetwork Interface Sublayer can unilaterally initiate and
terminate Broadcast Data Exchange Sessions. The rules for initiating and
terminating broadcast data exchange sessions are in Annex C.
A.2 Primitives Exchanged with Clients
Table A-1 lists the primitives exchanged between clients and the Subnetwork Interface
Sublayer. The names of these primitives are prefixed with an “S_” to indicate that they are
exchanged across the interface between the subnetwork interface sublayer and the
subnetwork clients. This table is intended to provide a general guide and overview to the
primitives. For detailed specification of the primitives, refer to Figure A-1.
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