Hybrid TCP-UDP Transport for Web Traffic
Israel Cidon, Amit Gupta, Raphael Rom and Christoph Schuba
Introduction by Raphael Rom
The World Wide Web is a given today. But that was not always the case. About a decade ago, the WWW was a small experiment (that exploded) and, as such, its designers took some shortcuts to enable them to prove a point -- only to discover later that some of those decisions are to haunt us for a while (maybe forever).
One of these decisions was to base HTTP on TCP. HTTP, is the web protocol and TCP is its underlying transport. But the two do not really match. HTTP is a transaction-oriented protocol and TCP is a connection-oriented protocol and that is all the story -- the main problem being that to serve thousands of concurrent Web requests requires an equal amount of TCP connections which, in turn, require keeping context for those connections, which leads to large overhead, bad performance, and rigidity. Introducing new concepts such as QoS in web service (and not just the communication portion) proved to be hard to achieve.
An obvious solution was to base the HTTP protocol on UDP and thus avoid the connection set-up for short transactions and allow for new and innovative web-based services. But the world cannot be easily changed, and backward compatibility is necessary. This led to the work described in this report, in which HTTP is based on a hybrid approach: if UDP can be used, it will and should, and will result in better service. For the die-hards, who insist on using TCP, that is also acceptable. And, best of all, when a UDP based system determines that in certain cases TCP connections are preferred, a TCP connection will be put in place.
The work itself consisted of two parts. The first is a general analysis and parameter optimization, which is reported in this paper. It analyzes traffic patterns, UDP parameters, threshold settings, and other web characteristics. This is reported in the paper which you are urged to read. The other part, subsequently done by the authors with some students, was the creation of a complete and comprehensive web service that provides distributed hosting with load balancing based on both communications and processing and with other QoS variations. The entire system was written in the Java(TM) programming language and indeed has demonstrated the superiority of that approach.
PUBLICATIONS:
- I. Cidon, A. Gupta, R. Rom and C. Schuba "Hybrid TCP-UDP Transport for Web Traffic" Pages 177-184 in Proceedings of the 18th IEEE International Performance, Computing, and Communications Conference (IPCCC'99), Phoenix, Arizona, February 10-12, 1999.
- V. Sokhin (I. Cidon and R. Rom supervisors) "Load balancing and quality of service for distributed web services" M.Sc. Thesis, Technion, Israel Institute of Technology, February 2001.