Congestion control is vastly important in computer networks. Arising naturally from the bursty nature of Internet traffic, congestion plagues not only the network edge, but also the network core. Many remedies have been proposed to fight congestion; active queue management (AQM) is one such proposal. AQM seeks to prevent congestion by actively avoiding it. Some queuing disciplines such as Random Early Detection (RED) will prematurely drop a random packet (with some probability) when the queue nears capacity to signal the sender to back off. However, RED utilizes queue length as a mechanism to indicate congestion. On the other hand, the Controlled Delay (CoDel) queuing discipline uses queuing delay as an indication of congestion. The problem with both RED and CoDel are that they indiscriminately treat all packets the same. Normally implemented using a FIFO queue, CoDel simply enqueues and dequeues packets in a first-come, first-served manner. Priority queuing can be carefully utilized to selectively service packets utilizing the very same metric CoDel uses for AQM, queuing delay. That said, Least Slack Time First (LSTF), a multi-processor scheduling algorithm employs priority scheduling, which coincidentally, is also based on delay. In the context of computer networks LSTF can be applied in the control plane or in the data plane. At the control plane, LSTF functions across the entire network, but in doing so requires all intermediary routers to implement it; LSTF also requires support at the packet level in terms of a slack entry. Within the data plane, LSTF can be implemented as a queuing mechanism based on delay spent in the router (just like CoDel AQM). This paper applies data plane level LSTF to CoDel AQM to enable delay-based packet classification within the confines of the CoDel AQM algorithm.

中文翻译：

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LSTFCoDel：具有 LSTF 风格优先排队的 CoDel

拥塞控制在计算机网络中非常重要。由于互联网流量的突发性，拥塞不仅困扰着网络边缘，也困扰着网络核心。已经提出了许多补救措施来对抗拥堵；主动队列管理 (AQM) 就是这样一种提议。AQM 试图通过主动避免拥塞来防止拥塞。当队列接近容量以通知发送方退出时，一些队列规则（例如随机早期检测 (RED)）会过早地丢弃随机数据包（有一定概率）。但是，RED 使用队列长度作为指示拥塞的机制。另一方面，受控延迟 (CoDel) 排队规则使用排队延迟作为拥塞的指示。RED 和 CoDel 的问题在于它们不加区别地对待所有数据包。通常使用 FIFO 队列实现，CoDel 只是以先到先得的方式将数据包入队和出队。可以谨慎地利用优先排队来选择性地使用与 CoDel 用于 AQM 的相同度量标准（排队延迟）为数据包提供服务。也就是说，最少空闲时间优先 (LSTF)，一种多处理器调度算法采用优先级调度，巧合的是，它也是基于延迟的。在计算机网络环境中，LSTF 可以应用于控制平面或数据平面。在控制平面，LSTF 在整个网络中发挥作用，但这样做需要所有中间路由器来实现；LSTF 还需要在数据包级别的 slack 条目方面的支持。在数据平面内，LSTF 可以实现为基于路由器中花费的延迟的排队机制（就像 CoDel AQM）。