Login_Bb_Credit Equals Zero; Open And Close Latencies; Fabric F_Port Attachment Initialization - Sun Microsystems storagetek sl500 Reference Manual

Login_BB_Credit Equals Zero

StorageTek libraries advertise Login_BB_Credit =0. When Login_BB_Credit=0 at
the other L_Port, the following rules apply:
The OPN originator must receive R_RDYs (receiver readys) from the library
■
before transmitting a frame.
The OPNed responder transmits R_RDYs for the number of buffers available to
■
receive frames.
Note – Sun StorageTek libraries respond with two to four R_RDYs on an OPN.
OPN Originators open as either full or half duplex, regardless of the value of the
Login_BB_Credit.

Open and Close Latencies

When Login_BB_Credit=0, a latency exists while before the libraries respond with
two (2) R_RDYs. This exists for every OPN before frame transmission can begin.
Some NL_Ports reduce CLS latency in another way:
To prevent buffer overruns, a CLS recipient is only required to have maximum
Login_BB_Credit, granted to any L_Port buffers, available before receiving the next
OPN.

Fabric F_PORT Attachment Initialization

In the absence of a loop environment the StorageTek tape libraries will attempt to
initialize with a fabric. This is accomplished by doing a Fabric Login (FLOGI). The
FLOGI process will be attempted in each class of service that the library supports.
Once the FLOGI process is successful the library will attempt to login (PLOGI)
with the fabric attached name server, if it exists. This process allows the device to
register its presence with the name server such that other initiators may query the
name server to find target tape libraries to use.
The library now waits for initiators on the fabric to complete a Port Login (PLOGI),
a Process Login (PRLI), and then to start executing commands.
96122 • Revision: F
Fabric F_PORT Attachment Initialization
Chapter 5 Fibre Channel Operations 51