Let me repeat, Iran is not disconnected from the Internet!
We have gotten a few queries about why we did not highlight Iran in our review of the network outages that resulted from the cable breaks. (See here, here and here.) Like most countries in the region, the outages in Iran were very significant, but for the most part they did not exceed 20% of their total number of networks. Now 20% is a significant loss, but in the context of an event where countries lost almost all of their connectivity, such a loss did not place Iran into the top 10 of impacted countries. So we focused most of our attention where the losses where the highest.
But then there was this Slashdot posting, claiming Iran had zero connectivity. This was news to us. It's said that "the first casualty of war is truth." Something similar can probably be said with regard to catastrophic failures. Truth might not be first, but it is a very close second. Journalists are pushed to meet deadlines for stories about topics for which they have little familiarity, and technical experts sometimes jump to conclusions on the basis of little evidence. It's not hard to see why the truth gets distorted; it's hard to think clearly when you believe the sky is falling.
The Slashdot claim was made since a web page at the Internet Traffic Report was reporting that the country was down. This report seems to be based on pings to a single router in Iran from multiple places around the world, which at best only indicates that one router in Iran is unavailable, not that the entire Internet has ceased to function there. Of course, once something ends up "in print", it tends to gain credibility and then be referenced by others. And before long, large numbers of people think it is actually true. (For a detailed ping analysis to the region during the outage, see this article.)
To understand what happened in Iran after the fiber cuts, we looked at actual routing data for the country, collected from around the globe. You can say with absolute certainty that if a provider does not have a route to any network in Iran, then no traffic will flow from that provider or its customers to Iran. But that is all you can say. The problem could be with the provider. That is why Renesys collects routes from a carefully selected set of peers around the world. If none of them know how to get to Iran, then you can be assured that Iran is truly off the air. Note that you have to be careful here with your selection of peers. If all of them end up traversing the same cable to get to Iran, even when other options exist, then the problem could be only with that cable and nothing more. To make a definitive statement about the worldwide reachability of any geography, you need to collect data from a diverse and at least somewhat independent set of peers so that you'll see all paths into the area. When the overwhelming majority of them have the same view of a situation, then you can conclude that the view is almost certainly correct for the entire world.
So back to Iran. In the following graph, we plotted the availability of Iranian networks for four entire days, 30 January 00:00 UTC until 3 February 00:00 UTC. The first day is the day of the cable cuts. Of the 695 networks that geo-locate to Iran, at no time were more than 199 unavailable, as observed by large number of Renesys peers. A few peers here and there might not have been able to reach Iran for local reasons, but the vast majority of the world could get to most of the networks in Iran for this entire time period. Note also that around 64 networks were unavailable before the event even started. These networks could be simply unused at this time. In other words, at most 135 networks that were active before the cable cuts disappeared for at least a short while during the outages.
|Global Reachability of Iranian Networks|
So much for Iran being off the Internet. Again, this is not to imply that Iran was not impacted by this event. A lot of networks were unavailable and some of them continue to be so. The end users of those networks are certainly noticing the problem and everyone in the country might be experiencing a slowdown due to the decrease in bandwidth to the region. Still, Iran fared much better than most.