Chapter 8 - 6. Congestion Management in TCP Storage Networks

Congestion Due to Over-utilization of the Target Link

The same problem may happen on a target/storage link when multiple hosts initiate large-size write I/O operations to the same target. 当多台主机对同一目标启动大容量写入 I/O 操作时，目标/存储链路上可能会出现同样的问题。

Comparison with Lossless Networks

A condition similar as Figure 8-4 would cause congestion also in Fibre Channel fabrics (explained in Chapter 2) and lossless Ethernet networks (explained in Chapter 7). Additionally, this would lead to congestion spreading Because Leaf-6 would invoke hop-by-hop flow control to slow down all the traffic from the spine switches on the link or within the no-drop traffic class. This congestion would spread to the source of the traffic (targets) victimizing many devices that share the same network path. 与图 8-4 类似的情况也会在光纤通道结构（第 2 章将介绍）和无损以太网网络（第 7 章将介绍）中造成拥塞。此外，这还会导致拥塞扩散，因为 Leaf-6 将调用逐跳流量控制，以减缓来自链路上脊柱交换机或无丢弃流量类别内的所有流量。这种拥塞会扩散到流量源（目标），使许多共享相同网络路径的设备受害。

In contrast, congestion does not spread in lossy networks (with or without TCP). This is the biggest difference because other unrelated devices are not affected. Adverse effect is limited to the flows that pass through the congested port. Host-1 is affected partially because some flows may be delayed due to TCP retransmission. But it is still receiving traffic at the full capacity of the link. 相比之下，拥塞不会在有损网络（无论是否使用 TCP）中传播。这是最大的区别，因为其他无关设备不会受到影响。不利影响仅限于通过拥塞端口的流量。主机-1 会受到部分影响，因为某些流量可能会因 TCP 重传而延迟。但它仍能以链路的全部容量接收流量。

The targets, that are sending traffic to Host-1, can send traffic to other hosts without being the victim of the over-utilization of the Host-1-connected switchport. Only the flows that pass through the over-utilized port are affected. To understand these differences further, compare this section to the section on Congestion in a Lossless Spine-Leaf Network in Chapter 7. 向主机-1 发送流量的目标可以向其他主机发送流量，而不会成为连接主机-1 的交换端口过度使用的受害者。只有通过过度使用端口的流量才会受到影响。要进一步了解这些差异，请将本节内容与第 7 章 "无损脊叶网络中的拥塞 "部分进行比较。

Congestion Within the Host