Specification • JAS Subnetwork Services provide a set of well-defined interfaces for applications to communicate across a network. They provide a layer of abstraction between the applications and the network protocols and data links, thereby allowing applications to be more portable and reusable. The services use a combination of a standard application...
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Synchronization Service
Specification • The following diagram shows how the JAS Synchronization Service fits into the overall communication stack. The Synchronization Service provides a standard interface to applications for sending and receiving time and event messages across a communication link. This service is typically used when the data link supports the ability to send...
TEP Parameters
Specification • Each TEP shall be defined with the following parameters: TEP Type Definition Local SLA The SLA assigned to the TEP for each channel. Remote SLA The SLA assigned to the TEP which is connected to the local TEP. TEP Type Identifies the TEP as transmit or receive. Window Size The...
TEP States
Specification • Each TEP shall be in one of four possible operating states: TEP State Definition CLOSED The TEP does not generate any packets on the link and does not respond to any packets received. ENABLED A TEP transitions to the ENABLED state when the host has requested it to be opened...
Time Management Service
Specification • The time access service, service type address 131 is used to access and manage time. The currently defined platform management service parameters are shown in the following table. Service Type Service Subtype Subtype Description Cmd Tlm Service Parameters Data Types and Description 131 1 Time Set X Time Time...
Trailer
Specification • JRDDP Packet Format The JRDDP packet trailer shall be a 16-bit CCITT Cyclic Redundancy Check (CRC) computed from the Destination SLA to the last byte of the Payload field. CRC The 16-bit CCITT CRC shall be computed according to the following polynomial: CRC Polynomial for JRDDP Prior to computing each...
Transmit Priority
Specification • When more than one packet is available for transmit, all ACK packets shall be transmitted first, then CONTROL packets, then URGENT packets (if implemented), then Retransmit packets (CONTROL or DATA), then DATA packets.
Transmit TEP Operations
Specification • Transmit TEP ACKs A transmit TEP shall not send an ACK packet. Transmit TEP Sequence Number Allocation Each DATA packet transmitted shall have a sequence number allocated from the TEP's transmit window range of available sequence numbers. CONTROL Packet Sequence Number All CONTROL packets shall be transmitted with a sequence...
Transport Channel Connection
Specification • A transport channel connection shall be considered established when a transmit TEP and receive TEP are both in the OPEN state.
Urgent Messaging
Specification • Urgent messaging is a best-effort priority communications path that does NOT provide for reliable delivery, missing packet detection, or out-of-sequence packet reordering. It may optionally be implemented in this protocol to facilitate an out-of-band transport pathway that may be useful for such things as time broadcasts, exception/error control, meta messages,...
Worst Case
Specification • If the link between the transmit and receive TEPs is bad, i.e. packets are corrupted or lost, and the receive TEP does not receive at least one CLOSE packet, the transmit TEP will transition to the CLOSED state after all retries have been exhausted and the receive TEP will remain...
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