Egypt got disconnected from the internet last night, but it does not appear that DNS is to blame.
It what appears to be an unprecedented move, internet traffic to and from Egypt dried up to a trickle, apparently as a result of a government effort to crack down on anti-presidential protests.
While a number of reports have blamed DNS for the outage, the currently available data suggests the problem is much more deeply rooted.
Traffic monitoring firm Renesys seems to be one of the best sources of primary data so far. The company’s James Cowie blogged today:
At 22:34 UTC (00:34am local time), Renesys observed the virtually simultaneous withdrawal of all routes to Egyptian networks in the Internet’s global routing table. Approximately 3,500 individual BGP routes were withdrawn, leaving no valid paths by which the rest of the world could continue to exchange Internet traffic with Egypt’s service providers. Virtually all of Egypt’s Internet addresses are now unreachable, worldwide.
BGP is the Border Gateway Protocol. It’s used where networks interconnect, enabling ISPs to “announce” what IP addresses they are responsible for and exchange traffic accordingly.
With no BGP routes into or out of Egypt, whether the DNS works or not is pretty much moot.
Blocking individual domain names, such as twitter.com, is one way to stifle communication. Another way is to instruct local ISPs to turn off DNS altogether.
But in both cases users can route around the blockade by choosing overseas DNS servers, such as the services Google and OpenDNS make available for free.
Even without DNS, users can still access web resources using IP addresses, if they know what they are.
But when ISPs stop announcing their IP addresses, even that becomes impossible. Even if you know how to find a web site, it has no way of finding you.
In this case, it seems likely that Egypt has physically unplugged itself from the global internet, which means its traffic is going nowhere, no matter what protocol you’re talking about.
But even this is not foolproof. According to experts interviewed on BBC news in the last hour, ISPs outside of the country are offering free dial-up access to Egyptians.
Egyptians with access to a dial-up modem, phone jack, compatible computer and long-distance service will presumably be able to use these services to reach the outside world, albeit at 1990s speeds.
With all the inter-governmental debate about the management of domain names over the last several years, the Egypt crisis is a useful reminder that DNS is not the quintessential element of internet governance it is often made out to be.