Researchers from the University of California, Berkeley, HP, Intel Corporation, Princeton University, the University of Washington and more than 60 universities from around the world have joined together to form PlanetLab, a global test bed for inventing and testing prototype Internet applications and services. The researchers aim to spark a new era of innovation by using "overlay" networks to upgrade and expand the Internet's features and capabilities.

PlanetLab may lead to new ways of protecting the Internet from viruses and worms. It could also enable new capabilities, such as persistent storage, the idea of giving the Internet a "memory." For example, 100 years from now a piece of data could still be found, even though the original computer on which it was posted no longer exists. In addition, this research could influence the future design of servers and network processors.

Upgrading the Internet

The Internet has been based on a small set of software protocols that direct routers inside the network to forward data from source to destination, while applications run on computers connected to the edges of the network. The simplicity of the software model enabled the Internet to rapidly scale into a critical global service; however, this success now makes it difficult to create and test new ways of protecting it from abuses, or from implementing innovative applications and services.

The PlanetLab concept was born when Intel researchers gathered a group of leading network and distributed systems researchers to discuss the implications of a new, emerging class of global services and applications on the Internet. This new class of services is designed to operate as "overlay" networks, which have emerged as a way of adding new capabilities to the Internet. The concept of an overlay or "on top of" approach might be familiar from text books where additional details are added to an image by laying a transparent sheet containing new graphics on top of an existing page. An example of this is overlaying an image of human muscles on top of an illustration of bones to show how the body works.

These overlay networks incorporate the Internet for packet forwarding, but integrate their own intelligent routers and servers on top of the Internet to enable new capabilities without affecting its performance today. These applications are decentralized, with pieces running on many machines spread across the global Internet, they can self-organize to form their own networks, and include some form of application processing inside the network (instead of at the edges), adding new intelligence and capabilities to the Internet.

One example of an overlay network enabling a new kind of Internet application is robust video multicasting. Today, a standard Web site that receives too many requests for the same video clip can bog down or crash; however, if this site were supported by an overlay network of smart routers and globally distributed content storage sites, it could redirect requests on-the-fly, sending them across the Internet to the nearest available content site to ensure the best viewing experience while keeping the site up and running.

PlanetLab consists of 170 computers (the first 100 provided by Intel) distributed at 60 research centers around the world. The goal of the project is to grow to more than 1,000 computers in the next few years. These sites connect large client populations (such as a university) to PlanetLab, providing researchers a facility that supports experimentation into new network services and applications under realistic conditions. At the same time, PlanetLab provides an environment for developing the core technologies necessary for the Internet to better support overlay networks in the future.

The initial PlanetLab core architecture was designed by Larry Peterson, Princeton University; Tom Anderson, University of Washington; Timothy Roscoe, Intel, and David Culler, Intel Research Berkeley Lab and U.C. Berkeley, who led this effort. Intel researchers continue to innovate on the PlanetLab architecture while providing operational support until the program matures. PlanetLab is currently open to research and educational institutions, including industrial research labs. Sites are allowed to join by contributing machines and bandwidth. This enables researchers from around the world, regardless of the location or size of their institution, to develop improvements for the next Internet. More information, including a complete list of PlanetLab's members, can be found at

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