FLOGI and PLOGI

Hi,

Lots of good technical details in the links above. Here is a summary.

N_Port: an end device connecting to a switched fabric network, such as a SCSI initiator or a SCSI target.

F_Port: a port on a switch that provides access to Fabric Services (eg. the Fabric Nameserver & the Fabric Login Server etc)

Fabric_point_2_point initialization (ie. N_Port to F_Port initialization) involves the following ordered sequence: FLOGI, PLOGI, PRLI.

• FLOGI
  •           N_Port requests a unique 24-bit address from the Fabric Login Server (accessible via an F_port on a Fabric switch).
• PLOGI
  •           N_Port informs the Fabric Name Server of its personality and capabilities. For example:
    • WWNN, WWPN
    • Buffer credits for flow control
    • clock frequency ('speed capability')
    • Upper layer protocol support (eg. SCSI-3, IP)
• PRLI
  • Upper layer protocol communication. Well, ever since SCSI was designed and engineered (1970s, or so, previously SASI...), SCSI initiators need to discover SCSI targets. So, during PRLI, N_Port SCSI initiators discover N_Port SCSI targets (which is an opportunity for the host (maybe a UNIX host) to assign a target ID to the device path).

•      Depending on the OS, you may be able to investigate further with commands like:

• egrep -i 'flogi|plogi|prli' /var/adm/messages    

Thought for the Day. How completely is SCSI ?  It's had a few makeovers, but maybe we should now call it BCSI . Hats off to the SCSI developers !!!