Too many connections weakens networks

When it comes to connecting networks or other systems at the same time, it is best to have many, nevertheless not too many, connections, mathematicians have found.

Administrators and network engineers have long assumed that the more connections they insert between multiple networks the more resilient the communications between these networks will be. The Internet, for instance, derives much of its resiliency from multiple, redundant links. However this is true only up to a point. Too many connections can to tell the truth be dangerous, because failures in one network can easily cascade to the other, noted Charles Brummitt, a mathematics researcher at the University of California, Davis, who led a team that looked into this issue.

The work is a mathematical model of how a collection of systems works at the same time. "We're taking a larger view and studying networks of networks," he said. Interconnected networks can be vulnerable to cascading failures, in which a failure, or overload, in one network can disrupt another network. In a typical scenario, when one network is overloaded, it will offload its traffic to the second network. Nevertheless if a failure is enough to overwhelm the first network, it may overwhelm the second network as then.

"There are some benefits to opening connections to another network. When your network is in accordance with stress, the neighboring network can help you out. However in some cases, the neighboring network can be volatile and make your problems worse. There is a trade-off," Brummitt said. "We are trying to measure this trade-off and find what amount of interdependence among different networks would minimize the risk of large, spreading failures."

The study, as well available in draft form at ArXiv, primarily studied interlocked power grids nevertheless could apply to computer networks and interconnected computer systems as so then, the authors note. The work could influence thinking on issues just as how to best deal with DDOS attacks, which can take down individual servers and nearby routers, causing traffic to be rerouted to nearby networks. Balancing workloads across multiple cloud computing services could be another area where the work would apply.

Of course, one of the largest networks of networks is the Internet. For the Internet, backbone providers peer with one another, or connect their networks at the same time, which allows Internet traffic to move seamlessly from source to destination. Much has been made about the Internet's natural resiliency in the face of disaster. However is it as resilient as it could be?

Thorny question

"That's a thorny question," Brummitt admitted. "I don't think we are in a position to make any guesses. Even understanding the network structure of the Internet is a problem in itself. Nevertheless the Internet has proved to be or rather resilient. So far, it seems like the Internet is not too interdependent. Yet this is speculative."

Joab Jackson covers enterprise software and general research breaking news for The IDG News Service. Follow Joab on Twitter at @Joab_Jackson. Joab's e-mail address is Joab_Jackson@idg.com

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