UC San Diego

Standardization of networking protocols enables interoperability and reduces cost, but is generally a slow process. As a result, there are many cases in which a networking protocol and the devices that implement it are not able to satisfy emerging user requirements. In such cases, the networking protocol falls short of current user requirements but has been too widely deployed to make a redesign sufficiently timely or cost-effective. In this dissertation, we advocate an approach to solving this problem that leaves deployed devices unmodified, by treating them as a black box. Rather, we show that for certain network devices, it may be sufficient to change the behavior of the device by "externally controlling" it, e.g., from software or another device, such that it solves the problem at hand. We demonstrate the effectiveness of such a black box approach for several challenging problems from two different areas: two problems from 802.11 wireless networking and one problem from inter-domain routing. In the first problem, we discuss the increasingly popular use of VoIP applications in the 802.11 protocol. Our experimental results show that 802.11 is ill-designed to carry VoIP traffic : an 802.11 hotspot faced with even a moderate number of VoIP calls in combination with data traffic may severely degrade the performance of both. The second problem, also from the area of 802.11, addresses unfairness of 802.11 in the face of emerging and potentially selfish upload-oriented applications. The third problem is from the area of inter-domain routing. We address a modern ISP's requirement for detailed control over routing to meet traffic engineering and security goals and to support applications such as VoIP. We show that the current inter-domain routing protocol, BGP, lacks the flexibility needed to implement the required degree of route control. We have implemented solutions to these problems that follow a black box approach and evaluated their effectiveness in combination with commercial networking devices. Our evaluation demonstrates that enhancing deployed networking protocols using a black box approach can be effective and efficient, yet portable and backward compatible with legacy devices