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Comcast killing my Internet?


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I'll preface this by saying that I've followed all the steps located at http://forum.utorrent.com/viewtopic.php?id=15992. I apologize if there's already been a gazillion threads about this. I did a search, and was unable to find a situation exactly like mine.

I live in Boston, and use Comcast. I've lived in the same location for two years.

The problem started a week ago. Whenever I start a torrent, my Internet dies completely within a few minutes. It's a full Internet shutoff that requires a modem unplug/replug to get it going again.

When I don't have a torrent going, my Internet is rock solid. Whether it's for browsing, gaming, video streaming, or downloading large non-torrent files.

Before the problem started, I never had problems with torrents. They'd be completely stable with speeds anywhere from 300 to 800.

I have NOT changed ANY settings on my computer, in uTorrent, on my router, or my modem. I have not installed any new programs. This problem is affecting both my desktop (Vista hardwired to router) and my laptop (Macbook on wireless). My wireless network is secured. Both machines use static IPs, and the appropriate ports are opened on my router. I always have PeerGuardian2 running.

I use my own modem, a DLink DCM 202 (with the firmware that makes it work with Comcast installed), and my router is a DLink DGL 4300. Both have been outstanding wherever I've lived.

I know that Comcast has started throttling torrents, but I thought that was just supposed to kill seeding, not the entire connection itself.

Does anyone have any ideas what the problem might be? Or have heard of a similar situation where, after two years of stable and solid torrent usage, it would suddenly start to kill my Internet entirely?

Any help or advice would be greatly appreciated.



For what it's worth, if it will help solve this problem... answers directly from the sticky at: http://forum.utorrent.com/viewtopic.php?id=15992#p258238

1. I've tweaked the upload and download speed using info from DSLReports and using the Speed Guide. I've made sure net.max_halfopen was set to 8. Disabled IP resolve. Disabled DHT. Tried lowering max connections. Have not tried patching TCPIP.sys (I have Vista Ultimate). I've tried connecting my modem directly to computer. No luck on anything. Connection is still dying within two or three minutes.

2. Speed guide said to set my upload limit to 72. Download limit is unlimited. Max connections is 450. Peers per torrent is 100. net.max_halfopen is 8. IP resolve disabled. DHT disabled.

3. Status light is green.

4. Speed Guide port checker says everything's okay.

5. net.max_halfopen = 8

6. Operating system is Vista Ultimate (and Mac Leopard).

7. Security I use the Windows firewall, AVG Free, and PeerGuardian2.

8. Modem is a DLink DCM 202. Router is a DLink DGL 4300.

9. ISP is Comcast in Massachusetts.

10. Connection type is cable. DSLReports gave results of download at 6156 kb/s and upload at 981 kb/s.

Anything else I should provide that will help?

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Hm. Can you try lowering max global connections to 100, and lower net.max_halfopen to 2? As well, if AVG has some kind of web filter, can you disable it?

Edit: On second thought, it's odd that it would be affecting your MacBook as well... That'd narrow the only possibilities down to your router, modem, or anything outside of the modem (ISP).

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The FCC filed a complaint against them, they are supposedly resolving the issue by the end of the year.


I am pleased that Comcast has reached an agreement with the company BitTorrent and has committed to implement a new "protocol-agnostic" management technique by the end of the year. And I note that we have decided not to issue a fine. But contrary to some claims, Comcast's agreement with the company BitTorrent did not obviate the need for us to act today.

First, BitTorrent was not a party to the proceeding. Consumer groups brought the complaint – not BitTorrent – and they and Comcast have not settled. As a basic issue of administrative law, we need to resolve the complaint. Comcast's agreement with a single company that uses the peer-to-peer protocol is not a substitute for addressing the consumer groups' complaint.

Second, it is important for the Commission to establish the important precedent that we will stop the bad actors. We establish a clear framework for how we will conduct our fact-intensive inquiries if situations arise in the future. If we had declined to act, as the dissenting Commissioners would have preferred, we would have provided certainty that broadband operators can block access and hide their actions from their own customers.

Third, we need to protect consumers' access. While Comcast has said it would stop the arbitrary blocking, consumers deserve to know that the commitment is backed up by legal enforcement.

Finally, particularly given the previous obfuscation Comcast engaged in to date, it is important that we require Comcast to respond to many still-unanswered questions about their new management techniques:

• What exactly do they mean by a "protocol agnostic" management technique?

• Will there be bandwidth limits?

• If so, what will they be?

• Will they be hourly? Monthly?

• How will consumers know if they are close to a limit?

• If a consumers exceeds a limit, is his traffic slowed? Is it terminated? Is his service turned off?

The Commission needs to understand the answers. Perhaps more importantly, Comcasts' subscribers deserve to know the answers.

These unanswered questions seem inconsistent with the disclosures that even the dissenting Commissioners agree are necessary.

The dissenters argue that the Commission should have conducted an investigation to find out the answers to these questions. We did. Our Enforcement Bureau sent Comcast a letter asking the company to respond to the allegations in the complaint and Comcast replied. Moreover, the Commission sought comment on petitions by Vuze and Free Press, which asked the Commission to rule on the same conduct at issue in the complaint and received more than 6,500 comments in response. In addition, the Commission held two public hearing on the complaint and the petitions. In total, the record contains more than 60,000 pages filling 15 banker boxes.

The fact that Comcast still has not come forward and disclosed the true nature of its network management practices, despite numerous opportunities to do so, cannot justify inaction on the complaint. Given the voluminous record evidence that Comcast engaged in unreasonable network management practices, it was incumbent upon us to order Comcast to stop the practices and disclose them to us. That is precisely what we are doing today.

In sum, by applying the framework we adopt today, the Commission will remain vigilant in protecting consumers' access to content on the Internet. Subscribers should be able to go where they want, when they want, and generally use the Internet in any legal means. When providers engage in practices truly designed to manage congestion, not cripple a potential competitive threat, they should not be afraid to disclose their practices to consumers.

I live in NH, so I've been following this as well.

* Here is a list of the various documents filed -

Statements by various comissioners -




(If you don't have M$ Word, u can download the viewer from here - http://www.microsoft.com/downloads/details.aspx?familyid=95E24C87-8732-48D5-8689-AB826E7B8FDF&displaylang=en)

"This spring, Comcast and Pando Networks, Inc.

announced plans to lead an industry-wide effort to develop a P2P Users' Bill of Rights. This effort is

now seeing implementation under the Distributed Computing Industry Association, which is focused on

developing best practices to ensure an optimum online consumer experience. Additionally, the P4P

Working Group, which includes Comcast, other major U.S. broadband providers, and applications

companies, continues to work together and participate in trials focused on maximizing consumers'

broadband experience."

* Dissenting views



They pulled out the child safety card trying to get the soccer-moms all stirred up. Professor numbnuts goes for the gold early with this - "it is tremendously important for network operators to be authorized to guard against unlawful Internet content such as child pornography" ......those damn p2p users....condoning child pornography....put 'em all in the can

"If you use cable modem or wireless broadband services, you may not know it, but you share bandwidth with your neighbor. That's just the nature of these networks, many of which were built long before P2P became popular. If your neighbor uses more bandwidth, that leaves less for you to use. This is especially true when your neighbor uses peer-to-peer applications. Many P2P applications consume as much bandwidth as they can find. In fact, only five percent of all Internet consumers are using 90 percent of the bandwidth due to P2P. Some estimate that seventy-five percent of the world's Internet traffic is P2P. As a result of increased P2P usage, many consumers' "last mile" Internet connections are getting clogged. These electronic traffic jams slow down the Internet for the vast majority of consumers who do not use P2P software to watch videos on YouTube or surf the Web. In short, this flood of data has created a tyranny by a minority"

Those damn p2p users, first they're filling their systems with child porn, and then they are stealing MY bandwidth with their supercomputers that have no limits on their download speeds !!! :rolleyes:

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If there were only 1 semi-short message I could get out to various news agencies, it would be this one:


ComCast's "agreement" with the company BitTorrent was very one-sided...BitTorrent clients might be locked out of ComCast's networks if BitTorrent didn't "play ball" the way ComCast wanted them to. That the agreement earned ComCast good P.R. is just a sad irony.

ComCast is at least loosely a part of the P4P consortium ...to create a "better" file sharing experience. But P4P is NOT made to make P2P (and in particular BitTorrent) more efficient. It's made as an excuse to KILL regular P2P...because their carefully controlled and monitored P4P (which had the advantages of a completely mapped understanding of ComCast's inner networks in the fine-grained test...or at least AS-awareness in the coarse-grain test) is "better"! Only sponsored content will be allowed on P4P. P4P will be controlled by the ISPs and media companies as THEY see fit. "We the people" file sharing will be dead if only P4P is allowed to exist.

This is what ComCast told the FCC:

"Comcast currently operates about 3,300 CMTSs, serving 14.4 million high-speed Internet customers. On average, the company said in the FCC filings, about 275 cable modems share the same downstream port and about 100 share the same upstream port."

A single DOCSIS 1.1 or 2 download channel is 38 megabits/second download bandwidth. It only takes 7 customers trying to download at 6 megabit/second to overload the WHOLE channel. ComCast told the FCC that on average 275 customers share a single 38 megabits/second download channel. This means there is only about 140 kilobits/second download available per customer on average...well below even FCC's OLD definition of broadband (200 kilobits/second)! The lowest official speed ComCast offers is 6 megabits/second download -- more than 40 TIMES faster than what ComCast can deliver. So the contention ratio is worse than 40:1 on average...no doubt over 100:1 in congested areas and/or where lots of people are paying for FASTER than basic service!

ComCast's claim that there's a lack of bandwidth to offer to the customers, "forcing" ComCast to resort to RST packets to disrupt customers' traffic...is NOT substantiated by their other claims about the "robustness" of their networks or the cheapness and ease of upgrading their lines!

From ComCast's own quarterly report in May 2007:

"So if you take a look at how it breaks down in 2007, 65% of our node splits are these logical, very easy to do and we can basically do them on a moment's notice and at the time right when we want to deploy the capital. 25% of these node splits are the modular where you go out and put a module in the optical node, and only one in ten are where we actually place fiber, and again it's typically around 1,000 feet. If you add it all up it comes out to less than $7 per affect home passed. And again this isn't every home passed in the system, it's only those where [we] actually have to perform the work."

"The second piece is DOCSIS 3.0 has kind of been the first opportunity that the cable modem manufacturers have had in a long time to do another version, another cost-reduced version of the technology. And as you put it together, basically a four or five-fold reduction in the cost per bit for our terminal equipment goes in the head end, and the ability to offer high-speed tiers at very similar economics to what we're offering today. And again we'll select markets where it makes sense to roll it out and we don't have to do it everywhere, we can do it even within a market because we've got total flexibility on that."

"we've got 750 megahertz through 96% of our systems here. That gives you 116 6 megahertz slots. Today almost three quarters of that is analog video here with 77 channels. As we go forward in the growth that we see, obviously immediately we've got growth in high definition where we're going to need more and more slots to put in high definition ...

So let me talk a little bit, and I'm going to start with what I call very conservative assumptions or conservative approaches to recapturing some of this bandwidth. The first one is what we talked about was Switched Digital Video and from that, under the conservative scenario here, we get 16 channels back. The next one is doing some analog to digital migration, this here takes off 7 channels so you still have a 70 channel analog basic package. The third one here is 14 channels that we get back from the improved compression technology that allows us to do 3-to-1 in HD, 15-to-1 with the other SD. And then finally we will reclaim as the Circuit Switched Voice comes off the system and some of the non-Video on Demand Pay Per View we get three additional channels.

If you take a look at all of this, what you end up with is basically 78 megahertz of what I'll call wiggle room. It doesn't mean we'd leave it open on the cable system, but it means that we've got enough margin in our plans to do a number of things."

To summarize:

As of mid-2007, it costs ComCast roughly $7 to increase capacity per household upgraded and they won't need to do it all at once as some do not need an immediate increase in capacity.

They are converting analog TV channels into compressed digital channels, freeing up more space while still increasing the number and quality of channels offered. After analog-to-digital upgrades there is roughly 13 6Mhz channels of "wiggle room" for additional expansion WITHOUT ComCast converting over their (typically ~860 Mhz) CMTS systems to the currently more expensive 1-1.2 Ghz frequency models which offer roughly 20-80% more bandwidth capacity.

Put together with:

"Comcast currently operates about 3,300 CMTSs, serving 14.4 million high-speed Internet customers."

So for each area connected by a single CMTS, there are ~4300 Internet customers...who are forced by ComCast to share less than 5% of ComCast's currently available bandwidth to the homes.

"And probably one of the biggest things to bring it into context would be take a look at, when you add all this up, Comcast delivers over 418 terabytes of entertainment, communication and information into an average household every month."

...yet internet bandwidth cap is only 250 GB per month, even on the fastest internet line ComCast offers in most areas.

Who's the "bandwidth hogs" now?

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Still having no success. I tried Comcast customer support, they said the signal from my modem was fine (even when I had a torrent going and had no Internet access).

At this point I'm thinking it's my modem or router. Since I get the same results when plugging directly into the modem, I'll go for the cheaper solution first. I'll be replacing my DLink modem with a Motorola SurfBoard, which apparently works better on Comcast networks. If that doesn't do anything, I'll be forced to take a look at the router.

I really really wish Verizon would roll FiOS out to my area. I am so incredibly sick of Comcast.

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I am having the exact same problem with my comcast and torrents. It started 3 days ago. I have the Motorola modem and I have to completely unplug it in order to even get back online, It doesnt just kill my torrents it kills everything for me. As soon as I open Utorrent it goes dead within about 5 minutes needing to be unplugged again. I am in Tacoma WA btw.

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Motorola Surfboard Modems as a general rule, don't handle lots of connections very well...they slow down. :(

Try the conservative uTorrent settings in the 2nd link of my signature.

Also try disabling DHT (both kinds), LPD, and Resolve IPs (right-click in Peers window of an active torrent).

You might also get better results with encryption in uTorrent set to Enabled or FORCED outgoing, if it's not already.

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I am also having exactly the same problem with ComCast cable internet and uTorrent. Opening uTorrent establishes connection and downloads for about 30 seconds, and then it kills ALL incoming and outgoing connections from my Win XP SP2 computer. This computer is on a wireless connection (D-Link DWL-G510) to my DI-624 router.

It does NOT kill other computers' internet connections on my network, either wired or wireless.

Cable Modem: D-Link DCM-202

Router: D-Link DI-624

Shutting down utorrent completely, restarting browsers, Repairing network connection, power cycling of router will not re-enable the connection on the computer that launched uTorrent. The only thing that works, as others have mentioned, is power cycling of the cable modem while the router is off, then powering on the router.

Of interesting note is that if the router is left on, and only the cable modem is power cycled, the problem persists.

I am in NM.

Update: Tried Switeck's suggestions and now can stay open and stable with functioning connection in other programs, albeit at severely reduced speeds:

D: ~23 kB/s (Yuck!)

U: 32 kB/s (per global upload rate limit)

I used conservative uT settings based on 512 Mbps upload speed, more or less, from: http://forum.utorrent.com/viewtopic.php?id=34259

Also, in Options > Preferences, disabled: DHT (both kinds), Local Peer Discovery, and Resolve IPs (right-click in Peers window of an active torrent).

Already had (and left) encryption to Forced, with allow Legacy.

I also:

- In Connection, disabled UPnp and NAT-PMP port mapping

- Set net.max_halfopen to 6

Note that while I'm limping along, status light is yellow exclamation point, not green. Then again I use a custom port and have not checked my port forwarding recently, so that will be the next step if this dies.

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This is BS! I really wish I had another option besides Comcast for high speed internet.

I did come across this email sent to me from Comcast

Dear Comcast High-Speed Internet Customer:

Comcast is committed to providing you with the best online experience possible.

One of the ways we do that is by managing the leading fiber optic network in the nation to ensure it is fast, safe and reliable. As part of our ongoing efforts to continuously improve the quality of our service, we are switching to a new network congestion management technique by the end of the year. It is focused on managing network congestion only when and where it may occur. It will also replace the current technique and will help ensure that all of our customers receive their fair share of network resources.

What does this mean for you? Probably nothing. We ran five market trials of this technique over the summer and found that less than one percent of customers were affected. So, the vast majority of customers will not notice any change to their Internet experience as a result of this new technique. During the times of busiest network use (which could occur at any hour, depending on your neighborhood), those very few extraordinarily heavy users – who are doing things like conducting multiple and continuous large file transfers – may experience slightly longer response times for some online activities until the period of network congestion ends.

As we transition to this new technique, we have amended our Acceptable Use Policy ("AUP") and posted it on the Comcast.net Web site. For links to the amended AUP, as well as answers to Frequently Asked Questions and more information about this new technique or our network management efforts in general, please visit our Network Management Policy page at:

What aa crock. I wonder if this is what is affecting my connection. It just seems odd that it is disabling modems and completely killing any internet connection.

Also BTW I made the suggested changes to my settings. It is working currently at an extremely slow speed of course. That is what sux!

Thanx to Switeck and Netmansam, thanks for the help.

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Switched over to the Surfboard tonight, and am having success. All torrents are stable, getting speeds of ~300kb, and my Internet hasn't gone down yet (torrents have been active for about five hours). I'm using my original uTorrent settings that I've always used.

I've only tried late at night, though, so this might change tomorrow during the hours that Comcast deems "high congestion". It's great to know that, according to Comcast, my being in the 1% of users that may be impacted by their new methods means nothing to them. It feels wonderful knowing what a valued customer I am.

But, my only other option where I live is DSL, so I'll just have to deal. Verizon FiOS can't get here fast enough.

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  • 1 month later...


<Comcast>I'm having the same issue.</Comcast> (Live in PA)

When I initiate a p2p download, the internet connection stays up for anywhere between 2 - 30 minutes. It doesn't seem to be dependent on the number of connections or the transmit rate. THEN, all of a sudden, DL and UL rates dip down to nil... My home router network stays up, but internet connection to my sh1te cable modem goes completely out, even though the xmit lights show normal activity. A hasty powercycle brings it all back up. One of my machines seems to download slower than the other, and consequently seems to keep uptime longer, but it's really dicey and I'm inclined to think that it's not a proscribed amount of data downloaded that causes the ISP to send an evil kill packet to your modem, but rather a data-timing combo algorithm. It's joker-random.

I've tried this on two different pieces of hardware, both XP pro SP2. Plugged into my Linksys WRT54GL (running baseline Tomato, no port forwarding, no QoS, UPnP on) and also hardwired straight into the sh1t modem (Comcast RCA). I'm lost.


P.s. Don't anybody say "Switch to Fios! I loves it................." I've already got my bribe ready.

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