Chapter 4-6. Troubleshooting Congestion in Fibre Channel Fabrics

Once the congestion is chased to the adjacent switch (Switch-1 in Figure 4-8), then continue looking for congestion on that switch and repeat these steps. If the congestion indication on the ISL port on the local switch (Switch-3 in Figure 4-8) is TxWait yet the adjacent switch (Switch-1 in Figure 4-8) does not indicate egress or ingress congestion on any ports, this means congestion could be because of insufficient B2B credits for the ISL’s speed, distance, and average frame size. This scenario is demonstrated in Case Study 4. 一旦拥塞被追至相邻交换机（图 4-8 中的 Switch-1），则继续查找该交换机上的拥塞，并重复上述步骤。如果本地交换机（图 4-8 中的 Switch-3）上 ISL 端口的拥塞指示为 TxWait，但相邻交换机（图 4-8 中的 Switch-1）上没有任何端口显示出口或入口拥塞，这意味着拥塞可能是由于 ISL 的速度、距离和平均帧大小导致 B2B 点数不足。案例研究 4 演示了这种情况。

If the congestion indications show high percentage utilization on an ISL then the remedy is simple: increase the capacity between the switches. Do this by adding additional individual ISLs, adding additional links to the existing port-channel, or even adding an additional equal bandwidth port-channel. Any of these increases the capacity between switches eliminating the high percentage utilization. 如果拥塞指示显示 ISL 的使用率很高，那么补救措施很简单：增加交换机之间的容量。具体做法是增加单独的 ISL、在现有端口通道上增加额外链接，甚至增加一个额外的等带宽端口通道。任何一种方法都能增加交换机之间的容量，消除高百分比利用率。