Practical Routing Research

A while ago I shared a single Internet connection between 3 different apartments in a complex. However, I found that most of the time I only received a small fraction, less than 1/100th, of the advertised bandwidth for the link. We eventually figured out that 1 of the three apartments was doing something to consistently steal the majority of the bandwidth. I had no idea how they were managing to do so, but I decided to try to research and see if there were any fairshare enforcement policies that I could turn on with the home router that we were using. Unfortunately, I wasn't able to find anything. I couldn't figure out if I simply didn't have the right search terms or if home routers didn't in general support such a feature. It seemed like an easy thing to do; simply maintaining some address or connection-based state and ensure that all connections receive an equal share of the available bandwidth.

Having had the above experience, I was very happy to read the research paper "Promoting the Use of End-to-End Congestion Control in the Internet". Although the main point of the paper is to introduce new mechanisms for inducing end-to-end congestion control through incentives, the article also discusses the core principles behind Internet fairshare. As the paper explains, there are two ways a connection can obtain more than its fair share of bandwidth. First, it can ignore the rules of congestion control. An example is any application that communicates through UDP. Second, the application can open multiple connections to perform the work of one connection. For instance, if all three apartments were using the network simultaneously but the application in one apartment opened up 10 connections simultaneously, then that apartment would obtain about 83% of available bandwidth. Some routers do implement per-flow scheduling using techniques such as weighted round-robin, but they are only guaranteed to work on a per-hop basis.

With the understanding I gained from the paper I am now better equipped to handle a similar problem in the future. I have a better background needed to choose the appropriate search terms to figure out if my router supports the relevant features. Furthermore, I would be better equipped to analyze packet traces on the network to determine the cause for the drop in bandwidth for two of the three apartments. While learning these things may not have been the main objective of reading the paper, it was still very enjoyable to associate what I was learning in class with solving problems I've had in real life.