Comcast Is Blocking More Than BitTorrent, Including Lotus Notes

As if the <a href="">AP's report last week wasn't enough</a>, it looks like Comcast is blocking other online services, including <a href=";jsessionid=ILWCZ5VQPJSREQSNDLPSKHSCJUNN2JVN?term=Gnutella&x=29&y=8">Gnutella</A>, <a href="">FTP</a>, and even <a href="

Stephen Wellman, Contributor

October 22, 2007

5 Min Read

As if the AP's report last week wasn't enough, it looks like Comcast is blocking other online services, including Gnutella, FTP, and even Lotus Notes. I guess Comcast doesn't respect the needs of telecommuters or net neutrality.Here's a look at Comcast's other "traffic shaping" tactics:

Yesterday, we posted about some experiments showing that Comcast is forging packets in order to interfere with its customers' use of BitTorrent. There have been reports of strange things happening with other protocols, and we've been running some tests on two other file transfer protocols in particular -- HTTP (which is used by the World Wide Web) and Gnutella. Comcast also has been strenuous in telling us, "We don't target BitTorrent". Perhaps not. Perhaps what they're doing is even worse.

In the limited tests we ran, we didn't see any interference with HTTP traffic. Comcast's network seems to behave correctly when you run a private Web server and share a few of your photos or videos over it (we tested files up to about 25 Mbytes).

But when you try to run a Gnutella P2P node on your machine, things start getting strange. Gnutella operates in two stages: first of all, your node starts a conversation with other nodes on the network. Once that conversation is happening, nodes can say things to each other to organize searches for and downloads of files. We saw forged TCP reset packets that stop some of the nodes from being able to converse with each other in the first place.

So Comcast is using a traffic shaping technique that recognizes Gnutella-specific behavior and adjusts bandwidth in such a way as to render the application slow or nearly useless? Isn't this a little excessive? And isn't targeting specific applications over others a little, you know, prejudiced? How does this not defy net neutrality?

Forged reset packets are normally the kind of thing that would only be present if a hacker was attacking your computer, but in this case, it's the ISP you pay money to each month that is sending them.

Strangely, the packet forgery only occurs when a non-Comcast node is trying to start a conversation with a Comcast customer's Gnutella node. If the Comcast customer starts the conversation, there is no Reset packet. This means that Comcast customers will not see Gnutella fail entirely -- the network just doesn't work properly.

And Comcast isn't stopping here, either. It's also targeting business applications like Lotus Notes. That's right, Comcast is going after people who are actually doing real work on its network, not just sharing MP3s or other bits of entertainment:

It isn't just BitTorrent and Gnutella that are affected. Kevin Kanarski has reported that Lotus Notes (a suite of software that many businesses use for e-mail, calendaring, and file sharing) also is being interfered with. We haven't tested this ourselves yet, but Kanarski's packet traces look a lot like the ones we've collected with BitTorrent and Gnutella.

And let's drill down to Kevin Karnarski's post on Notes and Comcast:

I finally have an end-to-end trace to share which shows that Comcast is filtering the port 1352 traffic. The images below show that Comcast is impersonating and using man-in-the-middle tactics to filter the traffic as stated in the CNet post. The images show a network packet trace from the client side and from the server side during the same session. This was a new memo composed within Notes with a 6-Mbyte attachment and then saved as a draft to the server database. The transfer did not succeed.

So I guess Comcast subscribers can't work from home now either?

It also appears that Comcast's shaping tactics haven't been limited to file sharing of either the consumer or work variety. Scores of our readers wrote in to complain that Comcast has been blocking their VoIP services. Let's take a look at some of their feedback.

Here is ET on Comcast's shaping of Vonage's VoIP traffic:

CBB is 100% correct. Comcast has been screwing around with Vonage for YEARS, and it has only gotten worse as they have expanded their offering in the VOIP arena. This should come as no surprise. THIS is what makes 'net neutrality' matter. It needs to be illegal. The concept that an ISP is somehow responsible for the traffic on its network is pure legal BS. The people engaging in child porn, or the people distributing copyrighted material illegally, are the ones that should be held accountable. ANY discussion centered on making the ISPs police the network will result in competitive censorship.

Needless to say, some of our readers are getting fed up:

I had to get rid of my VoIP and use Comcast's because the QOS stinks, now this. I would dump Comcast in a heartbeat if I had somewhere else to go.

One reader, Marco, claims Comcast blocks use of FTP to transfer backup files:

It is not just P2P and VoIP technologies. I use FTP to back up files periodically. Small files go up roughly as Comcast would advertise. Large files, after a predictable number of packets, get throttled.

Comcast's shaping of Lotus Notes, FTP, and VoIP is an attack on both telecommuters -- people who need to work from home -- as well as home-based businesses and small businesses that rely on Comcast as their service provider. If you're a telecommuter who needs to access your company's VoIP service or FTP a file to a corporate server, I guess you need another service provider. And if you're running a small business on Comcast's network, you better get Comcast VoIP or move on. That's real freedom of consumer choice.

What do you think? Is Comcast going out of its way by blocking VoIP and even work-related applications, like Lotus Notes? Or is Comcast justified?

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