Intelligence in the Network
In his essay "The Rise of the Stupid Network," David Isenberg envisioned a dumb but ultra-fast network whose only task is delivering a large amount of data from one place to another. All intelligence resides on the computers attached to this network, and connectivity is the only service that the network provides. This is the opposite of the PSTN model, where the network is intelligent and the end devices (telephones) are dumb. One must subscribe to a three-way calling service from the telephone company to bridge two phone calls together. Imagine having to subscribe to a similar service in order to open two web-browsing sessions at the same time.
Although the stupid network paradigm serves a useful purpose, it's becoming increasingly clear that mere connectivity is no longer the most important aspect of networking. Users are interested in increasingly sophisticated services that require the networknot just the end systemsto participate. The Internet is starting to resemble a utility, and users bring to it certain expectations, such as stability, availability, and protection from abuse and attack.
The computers connected to the Internet may have the appropriate software and enough processing power to guard against attack and abuse, but it isn't always feasible to rely on users to properly configure their software and hardware resources for this task. On the other hand, if the task of guarding against attack and abuse is implemented within the network itself, the end-system computer can focus on being a device used to access network services.
Internet access is quickly becoming the vehicle in which all kinds of communication services are carried. Therefore, expectations are evolving far beyond that of simple connectivity. The development of virtual private networks is one step in that evolution.