The following text is copyright 1998 by Network World, permission is hearby given for reproduction, as long as attribution is given and this notice is included.

Minutes as a measure

By Scott Bradner

The Internet is a packet-oriented device. To the Internet all is data and all data is divided into packets. Individual streams of data, known as sessions, between, for example, a web server and a browser are broken up into chunks called packets. Each packet contains an IP source and an IP destination address and is processed individually by the routers it traverses. In the Internet the data packets that make up a single session do not need to take the same path across the 'Net. They are not guaranteed to get to the destination in the same order as they were sent. They may be duplicated. They may even be lost and have to be retransmitted.

Within sessions data packets are only sent when they need to be. For example, if you are using an application that provides for telephone-like connections over the Internet, referred to as IP telephony, and you are not talking (for example, pondering the importance of the last thing that the person on the other end said) your application is not sending any data therefore no packets get sent. Well, if you cogitate too long a keepalive packet may be sent to keep the session alive but these are few and far between.

In addition, when you are connected to the Internet you may have multiple applications running simultaneously. The Internet protocols were designed to multiplex many concurent sessions, not to just run one at a time. The individual packets have tags to indicate which session they are part of.

There is nothing in the 'Net that lends itself to a time-based accounting of Internet data transfer. There may be a time-based access fee but since a specific connection potentially encompasses many parallel applications this can not be translated into a per-minute usage fee for a particular web server. Billing based on amount of data transferred may make sense but billing based on the amount of time that you spend reading some page you downloaded does not have any technical or resource usage justification.

So why is it that most stories about Internet telephony talk about billing in terms of minutes? Sure it is a familiar concept in the telephony world since many telephone calls for FAX or voice are billed per minute. For example there is projected to be over 400 billion minutes of phone usage in the US in 1998. But this does not translate to use of applications over the Internet. In some cases it might be nice -- the equivalent of a page of FAX can be transmitted from my machine at home in a small fraction of a second over my cable-TV based Internet link.

Use-based rather than usage-based pricing would also mean that sending some packets would cost more than others, a somewhat strange concept, also easy to defeat by changing the use tag between consenting end systems. But overall it seems a bit quaint to use yesterday's billing concepts for tomorrow's technology, it might even be a way to tell if the pundit understands the technology.

disclaimer: Harvard is re engineering its core systems to avoid the pejorative use of the description "quaint", but the above are my thoughts alone.