Experimental study of router buffer sizing

点击翻译按钮获取中文摘要

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, except with unwieldy spools of optical fiber (that can only implement delay lines, not true FCFS packet buffers).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.