Why YouTube is Offline Right Now
(From My Computer Networks Professor)
Right now www.youtube.com is offline. Why? Because somebody else told the Internet that they could reach the addresses that correspond to YouTube. This is an example of what is called a "prefix hijack" -- where some other network (also called an Autonomous System) announces an IP prefix they do not own, causing traffic meant for the legitimate destination to go to the wrong place. For some discussion amongst network operators about the problem, see the e-mail thread on NANOG (North American Network Operators Group) starting at
http://www.merit.edu/mail.archives/nanog/msg06299.html
as well as the Slashdot at
http://politics.slashdot.org/article.pl?sid=08/02/24/1628213
The apparent perpetrator is Autonomous System 17557 (Pakistan Telecom),
e.g.,
whois -h whois.apnic.net as17557
Most likely this was an inadvertent mistake on the part of the network operators of Pakistan Telecom. The speculation is that Pakistan Telecom was trying to block access to YouTube within the country, and inadvertently announced YouTube's address block to the rest of the Internet.
When we talk about interdomain routing in the 2nd half of the semester, I'll go through this example in more detail to show how easily something like this can happen, how it can be detected, and how network operators responded. In fact, in the time I took to write this note, YouTube seems to be back online! :)
-- Jen Rexford
Right now www.youtube.com is offline. Why? Because somebody else told the Internet that they could reach the addresses that correspond to YouTube. This is an example of what is called a "prefix hijack" -- where some other network (also called an Autonomous System) announces an IP prefix they do not own, causing traffic meant for the legitimate destination to go to the wrong place. For some discussion amongst network operators about the problem, see the e-mail thread on NANOG (North American Network Operators Group) starting at
http://www.merit.edu/mail.archives/nanog/msg06299.html
as well as the Slashdot at
http://politics.slashdot.org/article.pl?sid=08/02/24/1628213
The apparent perpetrator is Autonomous System 17557 (Pakistan Telecom),
e.g.,
whois -h whois.apnic.net as17557
Most likely this was an inadvertent mistake on the part of the network operators of Pakistan Telecom. The speculation is that Pakistan Telecom was trying to block access to YouTube within the country, and inadvertently announced YouTube's address block to the rest of the Internet.
When we talk about interdomain routing in the 2nd half of the semester, I'll go through this example in more detail to show how easily something like this can happen, how it can be detected, and how network operators responded. In fact, in the time I took to write this note, YouTube seems to be back online! :)
-- Jen Rexford