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#492570 07/11/08 08:08 AM
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Story HERE


Ed Vaughn, MBSWWYPBX
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pretty interesting... i've wondered about their methods and, knowing how some folks abuse P2P services, somewhat understand why they did what they did.. but this seems like a good response.


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You can manage network bandwidth without controlling the content.

Apparently, Comcast doesn't believe this is true. Either that or they are simply taking the easy way out by blocking well-known ports of file sharing programs.

The latter tactic is sophomoric.


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We have had some problems in the past at WiFi locations served by Comcast when we tried to initiate a VPN tunnel back to a client site. Perhaps they were trying to block P2P on a more advanced level as well.

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I worked for several years for a cable company, I am confident that many cable companys will begin or are doing the same now.

The internet was not designed to handle the traffic it is hammerd with today. More true many cable companies have way too many actives on a node, P2P traffic causes serious latency issues on those nodes, which can and will effect all services, VoIP, Video, and Data.

I have noticed my connection gets throttled when I use NetFlix. Watching the throughput on my line with OpenXtra it seems obvious that after a few minutes the bandwidth is throttled from 10mbps to under 200kbps. Watching the trace shows no signs of a bottleneck.

I do know that NetFlix uses high ports and low ports and could easily be viewed as warez bandwidth. The point of the story? I dont have one, as I am really inclined to support traffic shaping, why allow a few users to absorb all the bandwidth?

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How do you know you're getting throttled when you use Netflix? Or for that matter, know who is doing the throttling? Maybe you're just seeing the effect of a bursting service such as Comcast's Powerboost... or maybe after a few minutes your buffer is full and it slows down the stream to the speed you're watching it. Netflix, unlike YouTube, doesn't buffer the whole clip - just the bit ahead of what you're watching right now.

I'm not sure I understand why you think using "high ports and low ports" could "easily be viewed as warez bandwidth." Besides, doesn't Netflix's software use random port numbers?

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Originally posted by dagwoodsystems:
Apparently, Comcast doesn't believe this is true. Either that or they are simply taking the easy way out by blocking well-known ports of file sharing programs.
No, they were using Sandvine to monitor and disrupt P2P activity specifically by forging TCP packets with the RST flag set on outbound traffic, causing the connections to be dropped. Thus, Comcast P2P users got great download speeds while uploads would slow to a crawl. Clever, but not cool according to the FCC.


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I've done a little reading about Sandvine, and they sound like an interesting company. They have certainly had a wild ride from private to publically-traded.

Sandvine boasts the ability to allow video conferencing, VoIP and gaming traffic through, while quenching or controlling P2P traffic. Seeing that I can strap BitTorrent to use the well-known ports that common networked games use, how is one to distinguish one from the other? Like P2P software, these games also send and receive a pretty solid stream of traffic.

From my reading, it appears that Sandvine does so by employing heavy SPI (apparently to the point where they can recognize the specific details of a P2P session). That's pretty clever, but this is a cat and mouse game. The service provider is ahead at the moment, but I suspect some smart guy will develop a new sharing algorithm that, for example, mimics popular game traffic, such as that of "Call of Duty 4".

Still, that's very interesting. I appreciate your inside knowledge of Comcast's network management. Thanks.


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I gave you the tools I used, I told you when and how, I accomadated the "random port". The only thing I left out was the lag seen on the first three hops. I used common traffic analyzers, I also stated that it is possible its simply load on the node.

I did not say that I knew for sure, but I suspect something when a 10Meg service is loading a buffer with a 35 minute wait.

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Quote
Originally posted by Jeremy Wood:
I did not say that I knew for sure, but I suspect something when a 10Meg service is loading a buffer with a 35 minute wait.
Calm down there young'n, I'm not here to spar with ya. I'm just saying there's "more true many" ways to understand what you're seeing. Or maybe I have trouble understanding your writing.

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Originally posted by dagwoodsystems:
From my reading, it appears that Sandvine does so by employing heavy SPI (apparently to the point where they can recognize the specific details of a P2P session). That's pretty clever, but this is a cat and mouse game. The service provider is ahead at the moment, but I suspect some smart guy will develop a new sharing algorithm that, for example, mimics popular game traffic, such as that of "Call of Duty 4".
I don't know if it's SPI per se, but they've definitely got the technology to do deep enough analysis to sort traffic by application and do it fast enough to handle being in the same rack as the BGP gear in a very large server room. I've heard a few good ideas for working around it but you're absolutely right: it's a cat & mouse game.

I'm curious to see if they keep going after the pirates or if their attention shifts when other activities take over the title of bandwidth hog.


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Originally posted by 93mdk93:
Other activities take over the title of bandwidth hog.
Great point.
I did not try to sound rude, just came out that way. In the latter part of my initial post I actually said that I agree with some packet shaping, I also indicated that system operators are also to blame for latency issues.

Comcast from first hand experience overloads nodes, does not do enough sweeps, and for the most part can’t staff enough to maintain the system and its actives.

Again no disrespect, thanks for the discussion.


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