Comcast Blocking More Traffic

Aron Schatz
April 7, 2008

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It is pretty stupid that Comcast takes it upon itself to block bandwidth that customers pay for, but now they are intruding on services that really effect daily life. They are injecting packets for any sort of internet stream. Last Saturday, I couldn't get to my website for most of the day while other sites worked. I could ping and could not connect through SSH or HTTP. The server was fine, it was Comcast blocking the traffic.


Recently, it has been observed that Comcast is disrupting TCP connections using forged TCP reset (RST) packets [1]. These reset packets were originally targeted at TCP connections associated with the BitTorrent file-sharing protocol. However, Comcast has stated that they are transitioning to a more "protocol neutral" traffic shaping approach [2]. We have recently observed this shift in policy, and have collected network traffic traces to demonstrate the behavior of their traffic shaping. In particular, we are able (during peak usage times) to synthetically generate a relatively large number of TCP reset packets aimed at any new TCP connection regardless of the application-level protocol. Surprisingly, this traffic shaping even disrupts normal web browsing and e-mail applications. Specifically, we observe two different types of packet forgery and packets being discarded.


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