|In our recent posts about Hurricane Sandy, we analyzed the impacts of the super storm on Internet connectivity in the northeastern US.
However, in addition to knocking out power and Internet connectivity in a significant part of the New York metropolitan area, Sandy also had a surprising impact on the world’s Internet traffic, traffic that neither originated from nor was destined to areas affected by the storm.
From locations around the globe as varied as Chile, Sweden and India,
Survivability And Resilience of the Internet
The Internet was originally designed for survivability and resilience in the event of the loss of a critical node,
utilizing such technologies as packet switching and
While we certainly cannot avoid outages at the edges of the Internet
(e.g., individual data centers), the Internet as a whole is a highly survivable system.
Our earlier blogs on Sandy focused on outages at such Internet endpoints,
such as those hosting webservers, residential networks or smartphone users.
Here we look at what happens when a piece of the Internet’s core disappears and routers and their operators must react in order to keep traffic flowing.
Examples of Survivability and Resilience
In our initial blog about the impacts of Hurricane Sandy, we stated that:
As a result of outages [in New York City], we’ve observed Internet traffic shift away from the city as carriers scramble for alternative paths.
We provide a few clear examples of this phenomenon below. In each of the examples, a large provider shifted traffic away from its New York City infrastructure as the storm was battering the city. Also, in each example, Internet traffic continued to flow through the affected provider.
Thus, these fail-overs occur internal to each provider’s network and hence, are not visible in global routing data.
But we are able to observe these changes using active measurements in the form of traceroutes.
Our examples should be viewed as evidence of well-engineered networks continuing to successfully carry traffic as critical equipment temporarily went offline.
In the following graphics, each dot represents the latency (y-axis) of a traceroute measurement over time (x-axis). We have colored each dot based on which major cities the measurement traversed — specifically when they crossed through New York City and when they went via an alternative path.
Level 3 (AS 3356)
Verizon (AS 701/AS 702)
Tata (AS 6453)
Hurricane Electric (AS 6939)
NTT (AS 2914)
In each of these examples, the automatic fail-overs that kept international Internet traffic flowing seamlessly was due entirely to excellent engineering, provisioning and configuration on the part of these providers.
So even with the loss of a core hub as critical as New York City, the continued flow of Internet traffic is a testament to the skill and hard work of the network engineers at these and other Internet providers.
Congratulations on a job well done!