Cisco MDS 9000 Series Configuration Manual page 161

Congestion Detection, Avoidance, and Isolation
• Level 1 or Level 1.5
Level 1 or level 1.5 slow-drain condition indicates that the interface is without transmit BB_credits at
times. The interface can track the exact amount of time an interface is at zero transmit credits, in Fibre
Channel and the exact amount of time FCoE class is paused in both directions, in FCoE. When an FCoE
interface receives a PFC pause, it cannot transmit credits like a Fibre Channel interface when the Fibre
Channel interface is at zero transmit credits. This duration of time when an interface cannot transmit
credits is called TxWait and is counted in 2.5-micro intervals. An FCoE interface transmitting a PFC
pause (to prevent the other side from transmitting) is like a Fibre Channel interface not returning
BB_credits. This duration of time when an interface cannot receive credits is called RxWait and is counted
in 2.5-micro intervals. Currently, RxWait only applies to FCoE. In Fibre Channel, this duration of time
when an interface cannot receive credits is not measured, except by a software process, and is measured
only in 100-ms amounts of continuous time.
Module: 1 flow-control timeout-drops
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Show Clock
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2018-08-22 17:16:57
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ERROR STATISTICS INFORMATION FOR DEVICE DEVICE: FCMAC
---------------------------------------------------------------------------------------------------------
Interface |
| Time Stamp
Range |
|MM/DD/YY HH:MM:SS
|
|
---------------------------------------------------------------------------------------------------------
fc1/1 |F16_TMM_TOLB_TIMEOUT_DROP_CNT
|08/22/18 10:25:15
fc1/1 |F16_TMM_TOLB_TIMEOUT_DROP_CNT
|08/22/18 10:24:55
fc1/1 |F16_TMM_TOLB_TIMEOUT_DROP_CNT
|08/22/18 10:24:35
fc1/1 |F16_TMM_TOLB_TIMEOUT_DROP_CNT
|08/22/18 10:24:15
fc1/1 |F16_TMM_TOLB_TIMEOUT_DROP_CNT
|08/22/18 10:23:55
• Display of credit transitions to zero on a port (Fibre Channel only)—Whenever a port hits zero
transmit or receive BB_credits, the transmit (Tx) or receive (Rx) BB_credits transitions to zero is
incremented. When the transmit BB_credit transitions to zero is incremented, it indicates that the
adjacent device has withheld BB_credits or BB_credits are lost. When the receive BB_credit
transitions to zero is incremented, it indicates that the switchport is withholding BB_credit from an
adjacent device. The port-monitor counters can increment occasionally under normal conditions.
The most important thing to note is the duration that the Tx or Rx remaining credits were at zero
credits, and not when they hit zero credits. The port-monitor counters do not give any indication of
the amount of time the counters were at zero credits. Therefore, these counters are not a preferred
indication of congestion on a port. See the TxWait counter for a better indication of Tx congestion
on a port.
Error Stat Counter Name
Cisco MDS 9000 Series Interfaces Configuration Guide, Release 8.x
Information About Congestion Detection
|
|
|
|14713116
|13338566
|11929676
|11881213
|11771790
Count
143