LLFD – Link, Login, Fabric, Devices

Have just prepared a brief cheat sheet to remind which processes begin when we connect an HBA with the Brocade Fiber Channel switch port, in other words, when a device joins a fabric.

LINK

  • Signal transition (light/electrical)
  • Speed negotiation
  • Character and Word synchronization
  • Link initialization primitives (transition to active state, ready to send frames)

LOGIN

  • FLOGI – Request Fabric Login port (FFFFFE) for Port ID (PID) by sending NWWN/PWWN and exchange buffer credits capabilities with the switch port. Switch populates NS with PID, NWWN/PWWN
  • PLOGI – Port Login to Name Server (FFFFFC) to be able to register information in NS
  • SCR – State Change Registration at Fabric Controller (FFFFFD) to receive Registered State Change Notifications (RSCN) on events of online/offline of the zone members. SCR is mandatory for initiators
  • NS registration – Register additional attributes in NS: Node / port names, vendor, device model, firmware and driver versions. Separate requests are done for each attribute

FABRIC

  • Initiator requests FC-addresses of zoned devices. Makes additional requests to NS to get WWNs, etc.
  • Device probe – switch probes devices for additional information to populate NS with information from targets. Typically initiators (hosts) reject probes, while targets (storage systems) accept.

DEVICES

  • Initiator sends PLOGI to zoned targets
  • Initiator sends Process Login (PRLI) to targets
  • Start SCSI transmissions

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About mezzantrop

10 years of experience in large SAN and storage environments: mainly Hitachi, HP and Brocade. Now I am a proud SAN/storage IBMer. Empty – expect-like tool author. FreeBSD enthusiast.
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