IF A planet-wide data network, akin to the internet, were built on Mars, what would it look like? That might sound like a silly question, but it raises an important point. The design of computer networks is constrained by the need to be compatible with the internet and other systems that have grown up over the past four decades. What if network designers could start again with a clean slate, unencumbered by today's messy reality?

Ever since the internet's inception in 1969 engineers have tweaked it in a piecemeal fashion. That the system has scaled up well enough to handle almost 1 billion users and blazingly fast fibre-optic links is nothing short of amazing. But as the internet has grown, so too have problems such as spam, viruses and “denial of service” attacks that can cripple large websites—not to mention the challenge of accommodating all kinds of new devices, from cars to mobile phones to wireless sensors. “We've pretty much exhausted the tweaks we can do,” says Tom Anderson of the University of Washington.

As a result, a handful of the internet's original pioneers, along with a gaggle of young Turks, are now putting their heads together to consider how to fix the network's shortcomings—not by fiddling with a few things here or there, but by starting again from scratch. To this end, America's National Science Foundation (NSF) has launched two initiatives. The first, Global Environment for Networking Innovations (GENI), is a project to build an advanced test-bed network for piloting new protocols and applications. In January the project's leaders produced their conceptual design plan, and they must now lobby for the money to implement it. The second project, Future Internet Design (FIND), will examine how best to equip the internet for the needs of the future. In December, the NSF asked for FIND proposals from the engineering research community, which are due this month.

The aim of these schemes is to prompt academic engineers to think afresh for the longer term. “The challenging question is: can we conceive a vision for what a global communications network will look like in ten or 15 years? To do that, you have to free yourself from what the world looks like now,” says David Clark of the Massachusetts Institute of Technology, who helped to design the internet, and now is trying to fix it.“The internet is so obvious that it is hard to contemplate what a non-internet would look like,” he says.





Visions of the future

That said, it seems reasonable to assume that the number of devices on the network will continue to multiply in new and unforeseen ways. So researchers are starting from the assumption that communications chips and sensors will eventually be embedded in almost everything, from furniture to cereal boxes—“hundreds of billions of such devices”, suggested one group of engineers in a working paper last year. And while today's internet traffic is generally initiated by humans—as they send e-mails, click on web links, or download music tracks—in future, the vast majority of traffic may be “machine to machine” communications: things flirting with other things. To further complicate matters, these things will probably be connected wirelessly, and will move around.

Given all these demands, what sort of new ideas have the engineers come up with? It is still early days, of course, and a number of veteran internet engineers are holding back their own proposals in order to encourage the emergence of a younger generation, who might otherwise feel that the initiative was being dominated by the old boys' network, as it were. Still, a few proposals have already emerged.

One is “trust-modulated transparency”. The idea is to enable the network's traffic-routing infrastructure to judge the trustworthiness of packets of data as they pass by. Packets deemed trustworthy would be delivered normally, but dubious packets (from unfamiliar senders, for example) might be shunted aside for screening, just as security guards in office buildings wave through staff but look more closely at visitors. Particularly dubious packets might then be blocked, thus making various kinds of online wrongdoing more difficult. The whole system would be based on a “web of trust”, in which traffic flows freely between devices that trust each other, but is closely scrutinised between those that do not. “The basic, fundamental change is that packet-forwarding decisions are based on levels of trust between sender and receiver, as well as traditional things like optimal path,” says John Wroclawski of the USC Information Sciences Institute, one of the proposal's developers.

Another idea is a new approach to addressing, called “internet indirection infrastructure”, proposed by Ion Stoica of the University of California, in Berkeley. It would overlay an additional addressing system on top of the internet-protocol numbers now used to identify devices on the internet. This would make it easier to support mobile devices, and would also allow for “multicasting” of data to many devices at once, enabling the efficient distribution of audio, video and software.

But how could a new addressing system be tested? Dr Anderson and others have set up PlanetLab, a worldwide experimental overlay network that sits on top of the internet and acts as a testbed for new networking software. Using PlanetLab, researchers can quickly establish a global network of machines in order to test a new approach to packet routing, say, or content distribution. PlanetLab allows many such prototype networks to operate at once, without interfering with each other. One of these “virtualised” networks is in fact a recreation of the internet itself, which can be used to test modifications to the internet protocol.

Yet another proposed feature of a clean-slate internet comes from Dr Clark, who suggests adding diagnostic systems so that users can work out what has gone wrong when the internet fails to perform as expected. Then, when a videoconference call failed to connect smoothly, for example, it would be possible to determine whether the fault lay with the internet service provider or with poorly configured equipment. But the network itself would have to collect and share performance measures, something today's dumb network cannot do.

Today's network is dumb for a reason, however: it was a deliberate design decision. Back in the 1970s, rather than prejudging the kinds of uses to which the internet might be put and favouring some at the expense of others, its designers opted to make it as simple as possible. This open approach is what has made the internet such a vibrant platform for innovation. New applications, such as the web, peer-to-peer file sharing and internet telephony, were later able to emerge even though they were undreamt of back in the 1970s. None of these are explicitly provided for by the internet's underlying design, but neither does it preclude them.

The internet itself stays resolutely dumb, and blindly passes packets of data between devices on the edges of the network, which can then be upgraded to do new things. This non-discriminatory approach is known as the “end-to-end principle”, and it is one of the most cherished aspects of the internet's design. The end-to-end principle has promoted innovation at the edges of the network, but it has necessarily prevented innovation at its core. One possible remedy, which would allow diversity and innovation to flourish within the core of the internet, is the concept of “active networks” or “metanets”.

The idea is that today's routers, the boxes that direct internet traffic, would be replaced with more flexible devices, able to learn new communications protocols when needed. Devices at the edge of the network could then dynamically reprogram all the routers along the network path between them to use whatever new protocol they wanted. The routers would be able to partition themselves internally, so that other users of the network would not be affected. This approach has the advantage that new protocols would then emerge, tailored to applications such as video streaming, file sharing, and new things that have yet to be imagined. The drawback, however, is that routers are able to handle traffic quickly because they are single-minded. Adding complexity to the internet's core infrastructure might end up increasing versatility at the expense of performance—a trade-off not all users would be prepared to make.





Soul of a new network

The idea of metanets also provides an answer to the question of how to deploy a new clean-slate internet. Metanets would, in effect, allow multiple internets to run in parallel. There could then be competition between different protocols; and if one of the metanet protocols turned out to be much more secure, for instance, then security-sensitive users would have a reason to adopt it. Perhaps the clean-slate approach is not quite as esoteric and academic as it seems.

Before a Darwinian internet of competing metanets can emerge, however, engineers must dream up new ideas and devise new protocols, which will take time. And as well as confronting technical hurdles, the engineers vying to redesign the internet will undoubtedly find themselves caught up in social, political and economic arguments. That is because while the internet's existing architecture fosters innovation and promotes free speech, for example, it also allows spam and illegal music downloads to flourish. In reconsidering the technological underpinnings of the network, the engineers will inherently be making choices with far wider implications.

“When ever you design an architecture like this, you're not just designing a technical solution, but also designing an industry structure,” says Dr Clark. It may well transpire that the greatest impediment to upgrading the internet will turn out to be political disagreements over how it should work, rather than the technical difficulty of bringing it about.