Fibre Channel logins takes place after a link is operational (AC = active state), using ELS (Extended Link Service) protocol. There are three different types of logins in Fibre Channel technology:
Fabric Login (FLOGI) - F_Port login, presence of fabric, requests a unique 24-bit address (FCID/PID), class of service and BB_Credit from the Fabric Login Server;
Port Login (PLOGI) - N_Port login, request login to another N_port, before any data exchange between ports;
Process Login (PRLI) - establishes communication between two FC-4 layer processes (SCSI), between two different N_Ports
In the Login process different operational parameters are exchanged:
FC-PH version support
Classes of service supported
Frame size
Type of ACK supported: single frame, multiple frame
Number of buffer credits
Addressing
Time out values: E D TOV and R A TOV
Error recovery policies
Number of sequences
