The protocol stack for SpaceFibre is illustrated in Figure 1.

SpaceWire Protocol Stack

Figure 1 SpaceFibre Protocol Stack

The Network layer protocol provides two services for transferring application information over a SpaceFibre network: the packet transfer service and the broadcast message service. The Packet Transfer Service transfers SpaceFibre packets over the SpaceFibre network, using the same packet format and routing concepts as SpaceWire. The broadcast message service broadcasts short messages carrying time and synchronisation information to all nodes on the network. The network layer is responsible for the specification of nodes, routing switches, routing mechanisms, message broadcast and the definition of packets. Read more about SpaceFibre networks.

The Data Link layer provides quality of service, flow control and error handing for a SpaceFibre link. It sends packet information in frames of up to 256 bytes. The Data Link layer is responsible for the overall operation of the link, the quality of service and link error recovery.

The Multi-Lane layer operates several SpaceFibre lanes in parallel to provide higher data throughput. In the event of a lane failing the Multi-Lane layer provides support for graceful degradation, automatically spreading the traffic over the remaining working lanes. It does this rapidly without any external intervention. The Multi-Lane layer is responsible for lane coordination and lane failure recovery.

The Lane layer initialises each lane and re-initialises the lane when an error is detected. Data is encoded into symbols for transmission using 8B/10B encoding and these symbols are decoded in the receiver. 8B/10B codes are DC balanced, supporting AC coupling of SpaceFibre interfaces. The Lane layer is responsible for the individual lanes providing lane initialisation and encoding of data and control words.

The Physical layer serialises the 8B/10B symbols and sends them over the physical medium. Both electrical cables and fibre-optic cables are supported by SpaceFibre. The physical layer is responsible for the serialisation and de-serialisation (SerDes), electrical driver and receiver, connectors and cables. Flight connectors and cables for both electrical and fibre-optic media are being developed.

The Management layer supports the configuration, control and monitoring of all the layers in the SpaceFibre protocol stack with a management information base.

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