Checking Brocade LD BB Credits

If you’re seeing excessive “Time BB Credits Zero” in the gui, or tim_txcrd_z in portstatsshow, you may want to bump up the buffer credits.

SanSW1:admin> portbuffershow
User     Port     Lx           Max/Resv    Buffer Needed          Link   Remaining
Port     Type    Mode          Buffers     Usage  Buffers     Distance  Buffers
----     ----    ----          -------     ------ -------     --------- ----------
  0              LD              40          0       -             -
  1              LD              36          0       -             -
  2        E     LD              60         71      71            25km
  3              LD              60          0       -             -
135        F      -               8          8       -             -        413

“Max/Resv Buffers” is the maximum OR reserved buffers allocated to the port, which is adjusted by changing the distance (stupid way to do it) w/ portCfgLongDistance.

“Buffer Usage” is the actual number of buffers allocated to the port. This is affected by the distance set in portCfgLongDistance.

“Needed Buffers” is the number of buffers that are needed to saturate the link. If Buffer Usage < Needed Buffers the port will go to "buffer limited mode". In LD mode the "Link Distance" is measured by the round trip time of packets sent and received.

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