Frame Relay

1989 - Frame Relay introduced as part of Integrated Services Digital Network (ISDN). Assumes network is quite reliable. Frame relay switch routes incoming frames to correct output port, checks Frame Check sequence field and discards packets with errors, checks if switch buffers are full and if so discards packets. There is no flow control. Multiplexed, connectionless, packet switched Permanent Virtual Circuits (PVCs). PVCs connect two ports which remain active and provide Committed Information Rate (CIR).

Start Frame Delimiter, 1B

Frame Relay Header contains subfields

Data Link Connection Identifier (DLCI)

Discard Eligibility (DE)

Data field, 4 kB or smaller

Frame check sequence, 2B

End Frame Delimiter, 1B

End-system

End-system

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