Chapter 8 - 17. Congestion Management in TCP Storage Networks
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Dynamic Packet Prioritization (DPP)
Dynamic Packet Prioritization is another Active Queue Management algorithm available on Cisco Nexus 9000 switches. As Figure 8-15 explains, using DPP, a specific number of initial packets of a new flow are prioritized. In other words, a new flow always gets priority. 动态包优先级是 Cisco Nexus 9000 交换机上的另一种主动队列管理算法。如图 8-15 所示，使用 DPP，新流量的特定数量的初始数据包会被优先处理。换句话说，新流量总是获得优先权。
Figure 8-15 DPP mechanism
Like AFD, DPP also works on layer 4 flows, such as TCP flows, and not on I/O flows. Refer to the earlier section on TCP Flow Monitoring versus I/O Flow Monitoring for the difference between TCP flows and I/O flows. 与 AFD 一样，DPP 也适用于第 4 层流量，如 TCP 流量，而不适用于 I/O 流量。有关 TCP 流量和 I/O 流量的区别，请参阅前面的 "TCP 流量监控与 I/O 流量监控 "一节。
DPP can help with iSCSI and NVMe/TCP traffic because, for an I/O operation, command, R2T (if sent), and response are carried in one packet each. One or more data packets are sent depending upon the size of data requested by the I/O operations. As a result, TCP flows transporting smaller-size I/O operations are prioritized with DPP as compared to the TCP flows that carry traffic for backup job, which typically uses large I/O sizes resulting in a many packets per I/O operation. DPP 可以帮助处理 iSCSI 和 NVMe/TCP 流量，因为对于 I/O 操作来说，命令、R2T（如果发送）和响应各包含在一个数据包中。根据 I/O 操作要求的数据大小，会发送一个或多个数据包。因此，与传输备份工作流量的 TCP
