Happily Propagating Instability

February 17th, 2009 by · 1 Comment

According to several reports, the entire internet became unstable last night for about an hour.  Ordinary denizens of the web noticed somewhat, but it really got the attention of network operators.  Renesys has an excellent description of what happened which I found both entertaining and explanatory, but here is the quick version.

A small ISP in the Czech republic called SuproNet made a small, somewhat silly change to the configuration of its routers, which then propagated the change to its neighbors.  Routers being routers, they did one of two things:  a) they shrugged and passed it on, or b) they got offended and stopped talking to the router that sent it to them.  If it had been just one or the other, it wouldn't have mattered.  But it was mainly core routers that passed it on, and (mostly older) edge routers that stopped talking.  In other words, penetration was global and happened in minutes.   The core was working just fine, it just wasn't connected to as much of the edge anymore so traffic started having trouble finding paths to travel.   Of course, they got it sorted out pretty quickly, but the speed and extent of the phenomenon amazed me.

After all, the computer virus outbreaks we hear about span weeks or even months, usually propagating when unprotected users do something the virus designer tricked them to do.  This internet-born illness was made accidentally, didn't trick anybody, and it spread everywhere there was to spread in just minutes.  Automatic propagation of instability in the internet that we all depend on so heavily now is a bit terrifying, and yet that automatic propagation is systemic.  So we must rely on people to intervene when this happens, and so they did and stability was restored.

One has to wonder though, if this sort of thing can happen accidentally, just how easy would it be to deliberately take down the internet doing something like this?

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Categories: Internet Traffic · Telecom Equipment

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