With iSCSI, connection attempts are expensive; it may take many
seconds to determine that a connection will fail.  SRP connection
attempts are much less expensive, so we may as well avoid the
"optimisation" of declaring a state of permanent failure after a
certain number of attempts.  This allows a gPXE SRP initiator to
resume operations after an arbitrary amount of SRP target downtime.

SRP is the SCSI RDMA Protocol.  It allows for a method of SAN booting
whereby the target is responsible for reading and writing data using
Remote DMA directly to the initiator's memory.  The software initiator
merely sends and receives SCSI commands; it never has to touch the
actual data.