小缓存下路由器自主学习,仍能稳定处理高流量。
Learning in Strategic Queuing Systems with Small Buffers
- 给服务器加极小缓存,允许暂存一个未成功发送的数据包。
- 只需比集中调度多出常数倍的容量,系统即可保持稳定。
- 无需时间戳或旧包优先,随机选包也能稳定运行,适合真实网络场景。
我们研究具有轮次间传递效应的游戏中的学习结果:当前轮次的结果会影响未来状态。这类系统的重要例子是网络中的路由器,它们使用简单的学习算法寻找最佳数据包传输路径。这种简单、短视且分布式的决策过程使大型排队系统易于操作,但需要比集中协调时更多的资源。Gaitonde 和 Tardos(EC 2020 与 JACM 2023)首次研究此类系统,将其建模为无限重复博弈,其中路由器竞争服务器,系统状态(各队列中的包数)由前轮结果决定。然而,他们的模型假设服务器无缓存,导致未成功服务的包必须重发,这使得模型不现实。他们证明,在此模型中,即使服务器容量大幅增加,仍需使用时间戳和旧包优先才能保证系统稳定。本文引入两个关键改进,使模型更贴近现实并支持更高流量:第一,为每个服务器添加极小缓存,允许暂时保留一个未能即时服务的数据包;第二,不再要求时间戳或旧包优先。通过理论分析与仿真,我们发现当队列处于学习状态时,仅需比集中协调所需多出常数倍的服务器容量,系统即可保持稳定,即便服务器在同时到达的包中随机选择。
原文摘要 · Abstract (English)
We consider learning outcomes in games with carryover effects between rounds: when outcomes in the present round affect the game in the future. An important example of such systems is routers in networking, as they use simple learning algorithms to find the best way to deliver packets to their desired destination. This simple, myopic, and distributed decision process makes large queuing systems easy to operate, but at the same time, the system needs more capacity than would be required if all traffic were centrally coordinated. Gaitonde and Tardos (EC 2020 and JACM 2023) initiated the study of such systems, modeling them as an infinitely repeated game in which routers compete for servers and the system maintains a state (the number of packets held at each queue) that results from outcomes of previous rounds. However, their model assumes that servers have no buffers at all, so routers have to resend all packets that were not served successfully, which makes their system model unrealistic. They show that in their model, even with hugely increased server capacity relative to what is needed in the centrally coordinated case, ensuring that the system is stable requires the use of timestamps and priority for older packets. We consider a system with two important changes, which make the model more realistic and allow for much higher traffic rates: first, we add a very small buffer to each server, allowing the server to hold on to a single packet to be served later (if it fails to serve it immediately), and second, we do not require timestamps or priority to older packets. Using theoretical analysis and simulations, we show that when queues are learning, a small constant-factor increase in server capacity, compared to what would be needed if centrally coordinating, suffices to keep the system stable, even if servers select randomly among packets arriving simultaneously.
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