Friday, February 04, 2011

How Egypt Cut Off the Internet

The Basics of an Internet Connection

On the simplest of levels, your computer connects to the internet through an internet service provider (ISP) TeData, LinkDotNet.. etc. Your service provider then either connects directly to all the other internet service providers around the world or to a larger internet service provider that then connects to all the others.

When you open up your web browser and type a domain name into the address bar, say, for instance your service provider sends a lightning-quick request to whichever service provider uses to make its web pages publicly available on the internet.

The computer that holds all of's web pages sends a response back through its internet service provider basically saying, "Here's the web page you requested."

The Border Gateway Protocol

In order for ISPs to establish broader connections between the computers on their networks and the rest of the computers on the internet, traffic is routed through the Border Gateway Protocol (BGP). Egypt's ISPs have a certain amount of machine-readable internet protocol (IP) addresses that are used to identify connected computers across the internet, and the BGP makes the active IP addresses visible to the rest of the world to facilitate connections.

The Border Gateway Protocol (BGP) routing table routes have been taken offline in Egypt

What BGP does is 'advertise' the local address prefixes to neighboring networks. Wholesale ISPs propagate their customer's advertisements to their neighbors so that eventually all ISPs know all other ISPs' prefixes. This enables routers to know where to send packets with a given destination address. The 3,500 Egyptian prefixes are now no longer advertised, so they're missing from the routing tables of BGP routers around the world. This means that routers no longer know where to send packets addressed to IP addresses that fall within these prefixes—even if all the cables are still working fine.

Below Tedata hops and BGP port

179/tcp open bgp

28-1-2011 - After the BGP withdrawals sequence the situation, now, appear in this mode:

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