hesela.devFibre Channel exchange
A Fibre Channel exchange groups related sequences used by two node ports to conduct an operation.
The originator and responder exchange identifiers, OX_ID and RX_ID, identify exchange state in its port context. Exchanges can be unidirectional or bidirectional; RX_ID=0xffff denotes an unassigned responder exchange identifier. Do not interpret either number alone as a global operation identifier. [1]
An exchange is an FC transport construct, not a universal synonym for one SCSI command. In SCSI FCP, command status is represented separately in FCP_RSP. Neither an identifier nor a returned buffer credit demonstrates durable storage. [2]
Relations
- related
- Fibre Channel, Fibre Channel sequence, Fibre Channel frame, Buffer-to-buffer credit, SCSI, NVMe/FC
Citations
- FCIA: Inside a Modern Fibre Channel Architecture, Part 2 (2021), slides 7, 19, 23-31, 35 and 38
- Linux v6.12: fc_fcp.h, fcp_resp and SCSI status
Sources & caveats
- Source-backed protocol definition; no throughput, failure-rate or durability measurement is implied.