Hurricane Sandy caused major damage in both the Caribbean and the North-Eastern part of the USA. In an earlier article (RIPE Atlas - Superstorm Sandy) we showed data on 15 RIPE Atlas probes that are located in or near the affected areas in the USA. Most of these locations now appear to be back to normal round trip times to targets we monitor.

But the effects of Hurricane Sandy were felt beyond the immediately affected area. The region in Hurricane Sandy’s path happens to contain two major hubs for international Internet connectivity: the New York City (NYC) and Washington DC/Ashburn (ASH) areas. We looked at IPv4 traceroutes sent by RIPE Atlas probes that traverse paths through these areas to see what they could tell us about the impact that Hurricane Sandy had on the wider Internet.

The image below shows the number of paths we identified going through NYC (red) and ASH (blue) for traceroute4 measurements from all RIPE Atlas probes towards ns.ripe.net around the time Sandy hit the East Coast of the US. Because ns.ripe.net is located in Amsterdam, the Netherlands, RIPE Atlas probes on the American continent need to cross the Atlantic for the shortest path towards this destination. The time Sandy made landfall (on 30 October 2012 at midnight UTC) is marked with an orange line. You can see that the paths identified as going through NYC (red) dramatically drop about an hour before Sandy made landfall, and again drop a few hours later. At the same time as the number of paths through NYC drops, the number of paths identified as going through the ASH (blue) area increases significantly.

We also wanted to see the geographical extent of Sandy-correlated path changes from the NYC area to the ASH area. In the map below, each marker represents a RIPE Atlas probe. They are coloured as follows:

• Grey if NYC was not in the path before and after Sandy hit
• Blue if NYC was in the path before and after Sandy hit
• Red if NYC was in the path before, but not after Sandy hit
• Green if NYC was not in the path before, but was in the path after Sandy hit

The orange circle on the map represents the geographic location of the traceroute destination.

We found that for the destination in the Netherlands, the paths that were diverted away from NYC (marked red) were mainly located in North America, Oceania and South-East Asia.

What you can see from this article are examples of how the Internet routes around damage. It is telling that even with a major connectivity node under extreme stress the Internet kept going. The network operators who made this happen deserve a lot of credit for the work they put into planning their networks, and keeping them operational and interconnected under difficult circumstances.

What is also striking about this particular situation is the geographic extent of end-points that saw paths move away from the New York City area. For the five destinations that we examined, we saw paths stop traversing the NYC area for a significant number of sources as far away as South-East Asia and Africa, even for destinations that were not close to the area affected by Hurricane Sandy.

For many more graphs and maps and for a more detailed description of the methodology, please refer to the background article on RIPE Labs: RIPE Atlas: Hurricane Sandy And How the Internet Routes Around Damage.