Cisco MDS 9000 Series Configuration Manual page 156

Information About Congestion Detection
fc9/16 is up
Hardware is Fibre Channel, SFP is short wave laser w/o OFC (SN)
Port mode is F, FCID is 0x0c0100
Transmit B2B Credit is 16
Receive B2B Credit is 32
.
.
.
32 receive B2B credit remaining
16 transmit B2B credit remaining
The following example displays the transmitted and received credits information on an E port that is in
R_RDY mode:
switch# show interface fc1/5
fc1/5 is trunking (Not all VSANs UP on the trunk)
Hardware is Fibre Channel, SFP is short wave laser w/o OFC (SN)
Transmit B2B Credit is 64
Receive B2B Credit is 500
.
.
.
500 receive B2B credit remaining
64 transmit B2B credit remaining
The following example displays the transmitted and received credits information on an F port that is in
ER_RDY mode:
switch# show interface fc9/1 | i i fc | credit
fc9/1 is trunking
Transmit B2B Credit for vl0:15 vl1:15 vl2:40 vl3:430
Receive B2B Credit for vl0:15 vl1:15 vl2:40 vl3:430
0 invalid CRC/FCS,0 unknown class
Transmit B2B credit remaining for virtual link 0-3: 15,15,40,428
Receive B2B credit remaining for virtual link 0-3: 15,15,40,430
• Level 3
Level 3 slow-drain condition is characterized by Fibre Channel BB_credits being unavailable for 1 to
1.5 seconds. This condition causes the credit-loss recovery mechanism to be invoked to reinitialize both
Tx and Rx credits on a link.
Level 3 slow-drain condition is always accompanied by level 2 and level 1 or level 1.5 slow-drain
condition.
Credit loss recovery that is initiated by either side of a link can be seen in the following ways:
The following example displays the count of credit loss recovery being initiated by a switch on an
interface:
switch# show interface fc1/1 counters details
fc1/1
Cisco MDS 9000 Series Interfaces Configuration Guide, Release 8.x
138
27651428465 frames, 59174056872960 bytes received
0 class-2 frames, 0 bytes received
0 class-2 discards
0 F_BSY frames, 0 F_RJT frames
generated against class-2 frames
0 port reject frames
27651428465 class-3 frames, 59174056872960 bytes received
Congestion Detection, Avoidance, and Isolation