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Fibre Channel Interface Manual, Rev. D 37
The loop initialization process begins when any NL_Port forces the loop into the INITIALIZING state. See Fig-
ure 11. This initializing port begins transmitting loop initialization primitive sequences (LIPs). Any NL_Port can
cause this by sending any of the LIPS listed in Table 15. All LIPs cause the 4-step initialization process to
occur. A loss of signal will also force the loop to initialize.
There are five Loop Initialization Primitive (LIP) sequences:
The next L_Port in the loop receives the LIPs and transitions to the OPEN_INIT state and transmits LIPs to the
next L_Port on the loop. This cycle continues until the port that started the initialization process receives the
LIPs. It then also transitions to the OPEN_INIT state. This means all L_Ports on the loop are in the OPEN_INIT
state at this point.
Each port transmits a minimum of 12 LIPs and then transmits Idles for the AL_TIME (15 msecs). The L_Port
then transmit Loop Initialization Select Master (LISM) frames to select a loop master who will then control the
initialization process.
Loop initialization steps
There are four primary steps involved in initializing the loop.
1. Select a loop master based on the 8-byte port name (Loop Initialization Select Master—LISM).
2. Assign each port an arbitrated loop physical address (AL_PA). There are four ways a port can acquire an
AL_PA. These are listed below.
• Fabric assigned (Loop Initialization Fabric Assigned—LIFA)
• Previously acquired (Loop Initialization Previously Acquired—LIPA)
• Hard assigned (Loop Initialization Hardware Assigned—LIHA)
• Soft assigned (Loop Initialization Soft Assigned—LISA)
3. Generate AL_PA position map (Loop Initialization Report Position—LIRP).
4. Transmit completed AL_PA position map around the loop (Loop Initialization Loop Position—LILP).
Table 15: Loop Initialization Primitive (LIP) sequences
LIP Reason Code Use Description
F7, F7 Initializing LIP Used when an L_Port wants to acquire an AL_PA.
F8, AL_PS Loop failure The originating L_Port has detected an input failure. The
AL_PS is the AL_PA of the L_Port.
F8, F7 Loop failure The originating L_Port has detected an input failure but the
L_Port does not have an AL_PA.
F7, AL_PS Performance degradation The originating L_Port has detected poor loop performance.
Example: The L_Port is unable to win arbitration.
AL_PD, AL_PS Selective reset The source L_Port (AL_PS) wants to reset the destination
port (AL_PD). All L_Ports complete loop initialization. The
selected L_Port performs a reset after loop initialization.
FF, AL_PS Reset all The source L_Port (AL_PS) wants to reset all other L_Ports
supporting LIP reset on the loop. All L_Ports complete initial-
ization. The L_Ports supporting LIP reset all (generally only
the targets in a storage implementation) perform a reset after
loop initialization.