Chapter |CC|: Congestion Control
As introduced in Chapter |Intro|, a packet-switched network based on statistical multiplexing risks congestion at various routers and switches throughout the network. Chapter |Capacity| looks at the router side of the problem, where the immediate concern is that buffers fill up, and packets may eventually have to be dropped. We now turn our attention to the role played by the edge hosts, which are responsible for the volume of traffic flowing through those nodes.
The problem was not top-of-mind when the Internet protocol stack was first deployed in the early 1980s. By the end of the decade, however, with the Internet gaining serious use in universities (but predating the World Wide Web's invention by several years), the network began to experience a phenomenon known as congestion collapse. A solution—congestion control—was developed and deployed in the late 1980s and the immediate crisis was addressed. The Internet community has been studying and refining its approach to congestion control ever since. This chapter is about that journey.
The most famous early efforts to manage congestion were undertaken by two researchers, Van Jacobson and Mike Karels. The resulting paper, Congestion Avoidance and Control, published in 1988, is one of the most cited papers in networking of all time. There are good reasons for that. One is that congestion collapse really did threaten the nascent Internet, and the work undertaken to address it was foundational to the Internet's ultimate success. Without that work it's unlikely we'd have the global Internet we have today.
Another reason for the citation impact of this work is that congestion control has been an amazingly fruitful area of research for over three decades. Congestion control, and resource allocation more broadly, are wide open design spaces with plenty of room for innovation. Decades of research and implementation have built on the early foundations, and it seems fair to assume that new approaches or refinements to the existing approaches will continue to appear for as long as the Internet exists.
Further Reading
V. Jacobson. Congestion Avoidance and Control. ACM SIGCOMM '88 Symposium, August 1988.