Chapter 2 - 12. Understanding Congestion in Fibre Channel Fabrics

User Action

Because of the ability to absorb micro congestion, some users have gone as far as increasing the number of credits on the Fibre Channel switchports up to the maximum permissible limits. In lossy Ethernet networks with TCP transport, Active Queue Management (AQM) is quite common, as explained in Chapter 8. 由于具有吸收微拥塞的能力，一些用户甚至将光纤通道交换端口上的信元增加到允许的最大限度。在使用 TCP 传输的有损以太网网络中，主动队列管理 (AQM) 非常普遍，详见第 8 章。

Changing the number of credits on Fibre Channel ports for the purpose of absorbing congestion, if you choose to make this change, must be done after a thorough understanding of the product architecture because there may be additional implementation details, such as the number of buffers, how they are shared among the ports and any side effects of borrowing the credits. 如果选择更改光纤通道端口上的信元以吸收拥塞，则必须在充分了解产品架构后进行，因为可能还有其他实施细节，如缓冲区的数量、端口之间如何共享缓冲区以及借用信元的任何副作用。

Frame Flow within a Fibre Channel Switch

A Fibre Channel switch uses two types of flow control. 光纤通道交换机使用两种类型的流量控制。

 B2B flow control: This is used externally to the switch between the switchports and their directly connected devices. As explained earlier, it paces traffic rate from the directly connected sender to avoid buffer overrun on the receiver. B2B flow control is a standard-based approach. B2B 流量控制： 它用于交换端口与其直接连接设备之间的交换机外部。如前所述，它可以控制直接连接的发送方的流量速率，以避免接收方缓冲区超限。B2B 流量控制是一种基于标准的方法。

 Internal backpressure: This is used internally to the switch between the egress and the ingress switchports. When the egress switchport is congested, an internal backpressure paces the ingress frame rate on the ingress port to match the egress frame rate on the egress port. Consequently, the ingress switchport applies backpressure to its directly connected sender using B2B flow control. The implementation of the internal backpressure within a Fibre Channel switch depends on its architecture. 内部反向压力：这用于出口和进口交换端口之间的交换机内部。当出口交换端口拥塞时，内部反向压力会调整入口端口上的入口帧速率，使其与出口端口上的出口帧速率相匹配。因此，入口交换端口会使用 B2B 流量控制对其直接连接的发送方施加反向压力。光纤通道交换机内部反向压力的实现取决于其架构。

This section explains the frame flow path and internal backpressure mechanism using the example of the Cisco MDS switches

原文地址：https://blog.csdn.net/mounter625/article/details/143654392

免责声明：本站文章内容转载自网络资源，如本站内容侵犯了原著者的合法权益，可联系本站删除。更多内容请关注自学内容网（zxcms.com）！