Fundamental Design Issues for the Future Internet

This 1995 paper by Scott Shenker takes a step back from the networking research of the day and tries to predict what architectural changes will be necessary for the Internet to scale into the next decade. At that time, the internet had about 3 million hosts and tens of thousands of web sites; its transition from academic curio to a piece of public infrastructure was well underway. The challenge he focuses on is Quality of Service (QoS) guarantees, with the driving applications of streaming audio and video. The architectural question behind these demands is the questions of weather or not new service models are necessary for these applications to succeed. While IP provides best-effort delivery, real-time applications might benefit from bounded latency. The solutions he explores are admission control and fair queuing within the network core.

He considers the alternatives and problems with a differentiated services model: the largest problem is fairness, in the sense that end users would have no incentive to request anything less then the best service, which would defeat the point of the service model. The only solution he proposes is the only one that probably has any chance of working: charging different service classes different amounts for their utilization. However, this paper does not seem to seriously believe this will emerge as an evolution of the internet. Shenker also seriously considers maintaining the existing best-effort service model while over provisioning the network to allow latency and bandwidth sensitive applications to perform well; footnote 12 where he contends that if "bandwidth does become extremely inexpensive, some of our design decisions will be altered. It might be preferable to merely add bandwidth rather then extend the service model." is prescient.

With the benefit of hindsight, it appears that internet architects may have overestimated the cost and difficulty of modifying the IP model; even the roughly contemporaneous IPv6 transition has yet to have a major impact. The basic conservatism of network operators and the choice between new, untested technology that might improve utilization versus a lot more of the old technology (more pipes) has so far been answered in favor of the well-understood solution of adding more bandwidth; moreover, with good results.

To argue that the only way the internet has adapted to the demands of realtime traffic in the past ten years would be simplistic. The emergence of traffic-shaping middle boxes near endpoints to effectively prioritize traffic based on deep, stateful packet inspection is one development; another is the proliferation of content delivery overlay networks which geographically distribute latency-sensitive content to put it closer to consumers is another. Both of these have apparently been easier to do then modify the underlying network model.