DotSlash: A Scalable and Efficient Rescue System for Handling Web Hotspots

This paper describes DotSlash, a scalable and efficient rescue system for handling web hotspots. DotSlash allows different web sites to form a mutual-aid community, and use spare capacity in the community to relieve web hotspots experienced by any individual site. As a rescue system, DotSlash intervenes when a web site becomes heavily loaded, and is phased out once the workload returns to normal. It aims to complement existing web server infrastructure such as CDNs to handle short-term load spikes effectively, but is not intended to support a request load constantly higher than a web site's planned capacity. DotSlash is scalable, cost-effective, easy to use, self-configuring, and transparent to clients. It targets small web sites, although large web site can also benefit from it. We have implemented a prototype of DotSlash on top of Apache. Experiments show that DotSlash can provide an order of magnitude improvement for a web server in terms of the request rate supported and the data rate delivered to clients even if only HTTP redirect is used. Parts of this work may be applicable to other services such as the Grid computational services and media streaming

530 IEEE/ACM TRANSACTIONS ON NETW~RKINO,V~L.I,N~.~.AUGUST 1999 Mitigating Server-Side Congestion in the Internet Through Pseudoserving

Abstract-Server-side congestion arises when a large number of users wish to retrieve files from a server over a short period of time. Under such conditions, users are in a unique position to benefit enormously by sharing retrieved files. Pseudoserving, a new paradigm for Internet access, provides incentives for users to contribute to the speedy dissemination of server files through a contract set by a “superserver. ” Under this contract, the superserver grants a user a referral to where a copy of the requested file may he retrieved in exchange for the user’s assurance to serve other users for a specified period of time. Simulations that consider only network congestion occurring near the server show that: 1) pseudoserving is effective because it self-scales to handle very high request rates; 2) pseudoserving is feasible because a user who participates as a pseudoserver benefits enormously in return for a relatively small contribution of the user’s resources; 3) pseudoserving is robust under realistic user behavior because it can tolerate a large percentage of contract breaches; and 4) pseudoserving can exploit locality to reduce usage of network resources. Experiments performed on a local area network that account for the processing of additional layers of protocols and the finite processing and storage capacities of the server and the clients, corroborate the simulation results. They also demonstrate the benefits of exploiting network locality in reducing download times and network traffic while making referrals to a pseudoserver. Limitations of pseudoserving and potential solutions to them are also discussed in this paper. Index Terms- Caching, flash-crowd, Internet server technol-ogy, pseudoserving