Buffer sizing in internet routers

直到最近，人们还普遍认为互联网路由器需要大量的缓冲区。今天的商业路由器具有巨大的数据包缓冲区，通常存储数百万个数据包，假设大缓冲区导致良好的统计复用，从而有效地使用昂贵的长途链路。最近，我们（在斯坦福大学时）展示了可以用更小的缓冲区构建网络--每个路由器中只有几十个数据包缓冲区，代价是100%的链路利用率。如果这是正确的，会有有趣的实际后果。它可以消除一个主要的路障，以建立光学分组交换路由器。技术的最新进展（在UCSB）也使光FCFS包缓冲区，可以容纳几十个数据包在一个集成的光电芯片;更大的全光缓冲区仍然是不可行的。我们有兴趣探索的可行性，一个操作的全光网络，只有几十个光包缓冲区在每个路由器，并研究我们的理论结果举行的边界条件。以前在这方面的尝试包括在有限的实验室环境中进行的实验。有限数量的路由器和交换机（通常是一个或两个），固定的流量模式，平凡的哑铃形拓扑结构，...这是这些实验的一些缺点。在这个项目中，我们提出了一个更广泛的实验，以探索我们的缓冲区大小的结果的有效性的边界。为此，我们将使用斯坦福大学最近设计的4端口千兆以太网路由器，称为可控和可观察缓冲区（COB）路由器。COB路由器构建在NetFPGA平台上，具有可配置的缓冲区大小，能够以16 ns的时间分辨率（小于一个数据包的到达时间）监控和报告缓冲区占用情况。这将使我们比任何商业路由器都具有更多的控制和可观察性，此外还可以在我们的实验室中构建大型COB路由器拓扑。此外，NetFPGA系统比商业路由器便宜得多，使我们能够在实验室中构建大型COB路由器拓扑。

Until recently, Internet routers were widely believed to need large buffers. Commercial routers today have huge packet buffers, often storing millions of packets, under the assumption that large buffers lead to good statistical multiplexing and hence efficient use of expensive long-haul links. Recently, we (while at Stanford) showed that one can build a network with much smaller buffers still---with only a few dozen packet buffers in each router, at the expense of 100% link utilization. There are interesting practical consequences if this is correct. It could remove one major roadblock to building optical packet-switched routers. Recent advances in technology (at UCSB) also make possible optical FCFS packet buffers that can hold a few dozen packets in an integrated opto-electronic chip; larger all-optical buffers remain infeasible.We are interested in exploring the feasibility of an operational all-optical network with just a few dozen optical packet buffers in each router, and studying the boundary conditions where our theoretical results hold. Previous attempts in this direction include experiments performed in limited laboratory settings. Limited number of routers and switches (usually one or two), fixed traffic patterns, trivial dumbbell-shaped topologies, ... are a few of the shortcomings of such experiments. In this project, we propose a broader set of experiments to explore the boundaries of the validity of our buffer sizing results. To this end, we are going to use 4-port Gigabit Ethernet routers, called Controllable and Observable Buffer (COB) routers, recently designed in Stanford University. COB routers are built on the NetFPGA platform, have configurable buffer sizes, and are able to monitor and report the buffer occupancy with a time resolution of 16ns (less than the arrival time of one packet). This will allow us more control and observability than any commercial router, in addition to the possibility of building large topologies of COB routers in our lab. Furthermore, a NetFPGA system is significantly cheaper than a commercial router, allowing us to build large topologies of COB routers in our lab.