Comparison with Lossless Networks

Recall that in Fibre Channel fabrics (explained in Chapter 3, “Detecting Congestion in Fibre Channel Fabrics”) and lossless Ethernet networks (explained in Chapter 7), when the source of congestion is within an end-device, these devices are called slow-drain devices and they are detected using the metrics of the flow-control mechanism, such as the lack of the Tx B2B credits on the Fibre Channel switchport and excessive Pause frames on the Ethernet switchport. 回想一下，在光纤通道 Fabric（在第 3 章 "检测光纤通道 Fabric 中的拥塞 "中解释）和无损以太网网络（在第 7 章中解释）中，当拥塞源在终端设备内时，这些设备被称为慢耗设备，它们是通过流量控制机制的指标检测到的，例如光纤通道交换端口上缺少 Tx B2B 学分和以太网交换机端口上过多的暂停帧。

In TCP storage networks, when an end device is the source of congestion, the network ports do not show any indication. 在 TCP 存储网络中，当终端设备是拥塞源时，网络端口不会显示任何提示。

Source of Congestion within the Network

When the source of congestion is within the network, the primary detection approach is to find packet drops. If a network is provisioned for notifying the end devices using ECN, then detecting the ECN counters is another mechanism. ECN does not guarantee there will be no packet drops. Hence, ECN counters should be an early indication of congestion. They should be investigated at the same severity as the packet drops. 当拥塞源在网络内部时，主要的检测方法是发现数据包丢弃。如果网络规定使用 ECN 通知终端设备，那么检测 ECN 计数器就是另一种机制。ECN 不能保证不丢包。因此，ECN 计数器应作为拥塞的早期指示。对它们的调查应与数据包丢失的严重程度相同。

Packet Drops or Discards