Comcast Sued For Traffic Shaping (Again)Class action lawsuit springs up in DC ( old news - 09:47AM Thursday Feb 21 2008) tags: legal · hardware · bandwidth · cable · networkingTipped by funchords  Last November a California man filed suit against Comcast for the company's traffic shaping practices, which involve forging TCP packets in order to throttle upstream p2p traffic. While Comcast insisting their brand of network management is "reasonable" might thwart the FCC's investigation into the practice, the courts may see things differently. A second, class-action lawsuit has sprung up in Washington DC. According to a statement from the law firm involved, Comcast is misleading customers by saying they offer the "fastest Internet connection," because the ISP "intentionally blocks or impedes its customer's access to peer-to-peer file sharing." We're actually (almost) starting to feel bad for Comcast spokesman Charlie Douglas, who has been forced to repeat the same stock quote to hundreds of news outlets by now (including us): "To be clear, Comcast does not, has not, and will not block any Web sites or online applications, including peer-to-peer services, and no one has demonstrated otherwise," said Comcast spokesman Charlie Douglas. Douglas said that a minority of their customers use peer-to-peer. "Sometimes we have to delay [the sharing] because of the volume of it," Douglas said, so that the rest of the company's customers aren't affected by the network being bogged down by peer-to-peer. Comcast isn't commenting publicly on any lawsuits they're facing.
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|
 
ptrowski
Got Helix?
Premium
join:2005-03-14
Putnam, CT
clubs: | And the hits keep on rolling.... I see this happening more and more to Comcast in the future. Throttling maybe, but forging packets again is IMHO a bad situation. | |
| 
gaforces
United We Stand, Divided We Fall
join:2002-04-07
Santa Cruz, CA
 ·Cruzio Internet
edit:
February 21st, @09:39AM
| Feel bad? Why would you feel bad for a liar?
It has been demonstrated that they are forging the packets numerous times, and not just during heavy load.
--
~ Don't you ever give up, Don't ever give in. Were going to make it ~ Damian Marley | |
|  | quatrix
join:2005-02-11
Davie, FL
| Re: Feel bad? Are you complaining because you legitimately think they're doing something wrong or because you feel guilty for stealing and want to deflect the blame onto someone else? The same goes for everyone badmouthing the RIAA just because they push for enforcement of laws that they broke. | |
| | | 
Lumberjack
Premium
join:2003-01-18
Newport News, VA
 ·Cox HSI
| Re: Feel bad? said by quatrix :Are you complaining because you legitimately think they're doing something wrong or because you feel guilty for stealing and want to deflect the blame onto someone else? The same goes for everyone badmouthing the RIAA just because they push for enforcement of laws that they broke. That type of thinking is not permitted here. How dare you call out the thieves!
The reason Comcast will continually avoid this is because the people that are most affected by the "throttling" are the ones who aren't going to show up to court and say, "So I was downloading a movie that's not out yet and I had to wait two days instead of eight hours... that's not right".
Though, who knows... some P2P crackhead is bound to do that one day for not getting his porn.
--
»www.fairtax.org | |
| | | | AquaBlaze
Premium
join:2004-02-02
Encino, CA
| Re: Feel bad? said by Lumberjack :That type of thinking is not permitted here. How dare you call out the thieves! The reason Comcast will continually avoid this is because the people that are most affected by the "throttling" are the ones who aren't going to show up to court and say, "So I was downloading a movie that's not out yet and I had to wait two days instead of eight hours... that's not right". Yes, because P2P = piracy. 
Its fair to assume you don't get out much in the computer world, do you?
I participate in legal use of P2P technologies, and I'd be well affected by Comcast's methods...if I used them, that is. However, I'm sure there are plenty of Comcast users playing games that're assisted via P2P: (World of Warcraft being a huge one here), folks that download P2P-distributed large media files (again, legal ones - I've downloaded freely-avaliable audio & video this way), most any Linux distro user, etc.
Let the suit go on. It'll be interesting to see how this breaks down in the courts. | |
| | | | | | | | | | | AquaBlaze
Premium
join:2004-02-02
Encino, CA
| Re: Feel bad? said by Lumberjack :Maybe if little Joey wasn't downloading the Foo Fighters greatest hits the WoW updater wouldn't suck so bad (if you play WoW you know it's not faster than a direct download). Actually, I do play, and I get my downloads just fine off the Blizzard Downloader (if not faster than the mirroring FTP sites).
said by Lumberjack :Trying to explain the piracy relationship P2P has by citing WoW and some video content is pretty weak. That's like saying the armed bank robber was ok in his actions because he didn't kill anybody. I've never heard that comparison made. Usually the closest comparsion I've seen to criminalizing a protocol is the "banning roads due to escaping criminals". Granted the ratio of criminals : legal drivers is much different, but P2P's ratio would be much less as well if ISPs had been targeting the criminals themselves, rather than lump-sum an entire protocol's user base.
And pardon the earlier "not getting the sarcasm tags". If you read some of the posts made on these topics, you'll notice that there are some that give a 1:1 ratio of P2P users-to-pirates.  | |
| | | | | | |
Lumberjack
Premium
join:2003-01-18
Newport News, VA
·Cox HSI
| Re: Feel bad? Hardly any protocol is single usage. But I'd have to say it's almost fair to say that P2P is 1:1 with Piracy for most people that use P2P knowing it's actually P2P. And more than likely if you ask the general populous for a description of P2P they'd probably say "that's how I download my music and Heros episodes".
So I'm not good with analogies... my point is, trying to defend P2P as a viable protocol for non-pirated content is somewhat pointless (even though you're correct). P2P was created not to share linux distributions, WoW patches or whatever else... it was created to share mp3s ripped from CDs. And even if it's now used for legitimate things it still has and will always have that label.
Technically though I still think it's a spammy protocol and direct transfers or even mirror'd transfers are better. One connection, one stream is less "messy" for a network than hundreds of connections. Hell, that's probably more of an issue to providers than bandwidth... a lot harder for the feds to spy on that  .
--
»www.fairtax.org | |
| | | | | | | | NormanS
Premium,MVM
join:2001-02-14
San Jose, CA
·Pacific Bell - SBC
| Re: Feel bad? said by Lumberjack :So I'm not good with analogies... my point is, trying to defend P2P as a viable protocol for non-pirated content is somewhat pointless (even though you're correct). P2P was created not to share linux distributions, WoW patches or whatever else... it was created to share mp3s ripped from CDs. That may be true for Napster, and its ilk, but that isn't the same as BitTorrent (AFAIK).
Oddly, I have only downloaded 46 mp3s that can be considered pirated, and I did not use any P2P for those, just HTTP. Pirated in the sense that the distributors were not authorized, that I know of. However, I know that the source albums are out of print, and I searched long and hard for used copies. I drew a blank. They are imports, and I'd probably have to haunt the used CD stores in Akihabara in hopes of finding them.
Technically though I still think it's a spammy protocol...
Not by any accurate definition of "spammy". Of course, we always play fast and loose with words in English, and many words have taken on meanings far from the original. "Hacker", "Pro Life", "Saturday Night Special", and "Assault Weapon" come to mind. They currently have an evil aura, and are used as catch words for ideologically charged arguments.
...and direct transfers or even mirror'd transfers are better. One connection, one stream is less "messy" for a network than hundreds of connections. Hell, that's probably more of an issue to providers than bandwidth... a lot harder for the feds to spy on that .
--
Norman
~Oh Lord, why have you come
~To Konnyu, with the Lion and the Drum | |
| | | | | | | | AquaBlaze
Premium
join:2004-02-02
Encino, CA
| said by Lumberjack :P2P was created not to share linux distributions, WoW patches or whatever else... it was created to share mp3s ripped from CDs. Actually, the protocols they're going after (ie. BitTorrent) were created simply as a cheap means to distribute large files over the web - no specific purpose/reason was made or given. It was the pirates that jumped on this, feeling they were "untraceable" at the time, that made the protocol seem so closely tied with the technology.
Is piracy a greater volume of P2P traffic than legit users? Yes.
Does this mean that P2P = piracy? Absolutely not.
As I've said before, get the criminals off legit and legal protocol channels, not just criminalize the entire sect of the technology. | |
| | | | | 
adam henry
@comcast.net
moderated:
February 22nd, @12:04PM
thumbs down from:
gaforces
| let me guess...you download linux distros and wow patches all the time right? | |
| | | | | | AquaBlaze
Premium
join:2004-02-02
Encino, CA
edit:
February 22nd, @12:05PM
| Re: Feel bad? said by adam henry :
so in reality p2p does equal piracy you nitwit. Wow...given all your good points and mountains of research, let me reply appropriately:
Nevermind, I guess the mods did it for me.  | |
| | | | | | NormanS
Premium,MVM
join:2001-02-14
San Jose, CA
·Pacific Bell - SBC
| said by quatrix :The same goes for everyone badmouthing the RIAA just because they push for enforcement of laws that they broke. The RIAA whines a lot because sales are off from what their predictions claim they should be.
I have not bought an RIAA property in...I don't know when. I have probably spent about $30 on RIAA properties in the last ten years.
I don't download .mp3 music files; especially not those belonging to members of the RIAA.
So I must be rich from all of the money I didn't spend on them, right?
I have nearly 9GB of .mp3 files on my HDD. Probably spent a couple of thousand dollars to get them. A lot of show tunes from 美少女戦士セーラームーン。 All but two are imports. A couple of sound track albums, and an image album from ああ!女神さま!. Also imported. Some tunes from the likes of Hisaishi Joe, Kanno Yoko, Nagata Shigeru, and Namba Hiroyuki. All of which cost about double what the RIAA charges. All of which are licensed by companies who would form the RIAJ (I believe there really is a similar organization in Japan).
I have no sympathy for the RIAA. They promote music which does not suit my taste; the Japanese do, so they get my money instead.
--
Norman
~Oh Lord, why have you come
~To Konnyu, with the Lion and the Drum | |
| 
JTRockville
Data Ho
Premium,MVM
join:2002-01-28
Rockville, MD
clubs: | Arbitration Clause? Have all these folks opted-out of Comcast's arbitration clause? | |
| | 
major marco
Res Firma Mitescere Nescit
Premium
join:2003-02-13
Mission Viejo, CA
clubs:
edit:
February 21st, @10:09AM
| Re: Arbitration Clause? said by JTRockville :Have all these folks opted-out of Comcast's arbitration clause? doesn't matter because Federal and Appeals court case law have have struck down forced arb clauses for big players such as AT&T, Overstock.com and Cingular. Further, the Supremes denied cert to hear a case that would make forced arbitration binding on Class action lawsuits. So Comcrap can't rely on some forced arbitration clause to save their dumbasses from this debacle. | |
| | | axus
join:2001-06-18
Washington, DC | Re: Arbitration Clause? Gotta love statutory rights | |
| | | |
major marco
Res Firma Mitescere Nescit
Premium
join:2003-02-13
Mission Viejo, CA
clubs:
| Re: Arbitration Clause? said by axus :Gotta love statutory rights What're you talking about...statutory rights doesn't have jack to do with anything in this discussion. Case law, baby. | |
| | | 
fishmaster
Premium
join:2004-10-08
Rockford, IL
·Comcast
·Insight Communicat..
| Be sure your sin will find you out. Half truths are whole lies. While I understand the 'Network Management' aspect. But to deliberately misrepresent an action or protocol & then blatantly lie about it is as guilty as one could get.
--
Browse Alot - Sign In Little - Post Even Less | |
| | fiberguy
My views are my own.
Premium
join:2005-05-20
| Re: Be sure your sin will find you out. said by fishmaster :Half truths are whole lies. While I understand the 'Network Management' aspect. But to deliberately misrepresent an action or protocol & then blatantly lie about it is as guilty as one could get. I wonder if that same guilt passes on to those who's very actions are causing the traffic shaping.. and I'm not talking about BT use.. I'm talking about what people are using BT for.
You know,... there's a certain reason why prostitutes don't go to the police when they are beaten by their pimps.. | |
| | |
fishmaster
Premium
join:2004-10-08
Rockford, IL
·Comcast
·Insight Communicat..
| Re: Be sure your sin will find you out. Meaning what? Everyone uses BT for Illegal & Nasty stuff?? Pretty narrow minded aye. Or are you speaking from your own heart. Personally I really don't care much for BT & such. There has been a few times I have used it for legitimate software distributions, One of them from M$ themselves.That's not the real issue...
Sure some folks BT 24/7/365 and abuse bandwidth. The same can be said over people who upload/download large files too & from servers & ftp sites quite frequently. Same can be said over the Video Junkies with the ever increasing HD content. Again, that's not the real issue. 2 wrongs do not make a right.
The real issue is for a Company (Comcast in this case) to do what they are doing, Outright initially lie about it, Media propagate justification for doing so and still not being straight up. They know they are goofing up. Don't you know if the shoes were reversed in some way they would be up in arms over stuff??
Maybe I just don't quite understand your post...If I missed it? It wouldn't be the first time. No Worries.
--
Browse Alot - Sign In Little - Post Even Less | |
| | | gal
join:2006-12-21
Toledo, OH | You do realize there are movie studios selling downloads of thier films over BitTorrents don't you? There are plenty of legitimate reasons this can be used, but maybe your feeling a little guility? | |
| | | | fiberguy
My views are my own.
Premium
join:2005-05-20
| Re: Be sure your sin will find you out. Nope.. I'm feeling really good that you, like the other responder, can't read the message as written, nor do you pay attention to the entire thread, rather, you pick one word and jump. Be proud...
I do realize that movie studios use the service as well. When have I EVER said there wasn't lawful purposes behind the service? .. and for that matter, when did I ever say that it was invented FOR unlawful purpose?
Now that I have cleared the bunk from your reply, maybe we can get to the point of who has the guilty conscious. Comcast, as has been said many times (for the blind) is not throttling the downloads of BT users. If, as you are saying, you want to download a movie from the studio who is using BT, you should be fine.. their bandwidth is not being affected by Comcast's traffic shaping. You, if you are a comcast customer, which being in OH I doubt you are, should have no problem downloading from the studio since Comcast's network management isn't going to throttle the studios upload.
I've said this before and I'll say it again.. the cable model is not to handle servers which are high bandwidth users. Only those that want to spin and twist and play these f'd up mental games to justify their abuse of the TOS/AUP will continue to fight the fact that their BT programs also act as a server which is at the heart of the issue. | |
| whiteybulger
join:2003-03-11
Belmont, MA | Does packet forging reduce network traffic? I don't know how this works, but if they're just injecting fake packets to slow a given application, doesn't that actually increase network traffic? | |
| | 
koitsu
Premium
join:2002-07-16
Mountain View, CA
| Re: Does packet forging reduce network traffic? said by whiteybulger :I don't know how this works, but if they're just injecting fake packets to slow a given application, doesn't that actually increase network traffic? The trade-off is substantial. Two TCP RST packets are about ~54 bytes in size each. Consider what sort of bandwith savings they're inducing by sending 108 bytes of traffic every time someone tries to seed. | |
| | |
gaforces
United We Stand, Divided We Fall
join:2002-04-07
Santa Cruz, CA | Re: Does packet forging reduce network traffic? Its like a smart targeted DoS attack. Interfering with packets = Denial of Service. | |
| |
Jack2131
@sbcglobal.net
| P2P REALLY slows down an entire network. If someone initiates a couple popular torrents on my dsl line, everything screaches to a halt/slow motion browsing. It's why I bought a Ubicom-based router to "degrade" the p2p applications while I'm doing other things. If they didn't do that I'm sure ALOT more people would be complaining. But hey, they could spend more on infrastructure, but p2p can consume an entire line no matter how fast it is. | |
| | | 
knightmb
join:2003-12-01
Franklin, TN
·Comcast
 ·Vonage
·Speakeasy
| Re: Does packet forging reduce network traffic? said by Jack2131 :
P2P REALLY slows down an entire network. If someone initiates a couple popular torrents on my dsl line, everything screaches to a halt/slow motion browsing. It's why I bought a Ubicom-based router to "degrade" the p2p applications while I'm doing other things. If they didn't do that I'm sure ALOT more people would be complaining. But hey, they could spend more on infrastructure, but p2p can consume an entire line no matter how fast it is.
It's not just P2P, you realize that someone doing a single file upload on your DSL at maximum send rate will basically produce the same effect. It's just the limitations of a NAT based router. If you had two static IP address and each computer had it's own, the one doing P2P would have a lot less affect on the second computer since this would call into the TCP/IP even split of bandwidth between the two instead of the "race to get the packet out first" that is one of the limitations of a NAT with multiple computers behind it.
It's not easy to demonstrate on a modem with a single LAN to WAN setup, but try a DSL or Cable modem (usually has to be business class) that has multiple ports to support multiple static IP address for each port and the problem is only noticeable from a benchmarking upload speed standpoint rather than "nothing is working" view. | |
| | | |
koitsu
Premium
join:2002-07-16
Mountain View, CA
| Re: Does packet forging reduce network traffic? said by knightmb :It's not just P2P, you realize that someone doing a single file upload on your DSL at maximum send rate will basically produce the same effect. This is why packet prioritisation (read: QoS) is important. The term QoS is used incorrectly all over the place now, which is quite irritating -- so if you want a good read about how QoS can truly improve performance over slower (read: non-100mbit) links, try this. It specifically documents how to solve the above issue (re: downloading a single file at full speed causing all other applications to perform horribly) using pf ALTQ on OpenBSD or FreeBSD. I'm positive Linux has similar.
However, there is one thing I should point out about P2P vs. downloading a file at high speed via HTTP:
From a TCP state perspective (read: NAT, or anything that tracks TCP states in general), P2P is hell. The number of states which have to be tracked for torrents where there's thousands of peers is bordering on nuts. I wouldn't be surprised if a hundred users downloading the same torrent (a thousand peers each) on a single Juniper M20 could cause the routing engine to slow significantly. So from *that* perspective, P2P does in fact slow down a network.
But in that situation, you're overselling capacity, and should look into getting another M20. *shrug* That's just the way it goes. That's reality, and some ISPs want to try and pinch pennies in every way possible rather than realising users are paying for said growth.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer. | |
| | | | | 
funchords
Robb
Premium,MVM
join:2001-03-11
Hillsboro, OR
·Verizon Online DSL
·Skype
·Comcast
| Re: Does packet forging reduce network traffic? Very good points -- just wanted to clear something up (since you cleared up a few things for others)...
said by koitsu :The number of states which have to be tracked for torrents where there's thousands of peers is bordering on nuts. I wouldn't be surprised if a hundred users downloading the same torrent (a thousand peers each) on a single Juniper M20 could cause the routing engine to slow significantly. Although users can often change some of these settings, users generally do not connect to more than (some number between) 30-70 other peers in a swarm. This is by design -- there is no added efficiency in doing so. The knee of the curve of diminishing returns falls between 50-80 (depending on a lot of factors, most of which change from moment to moment).
Also keep in mind that 80%-ish to 90%-ish are on Microsoft TCP/IP stacks. They won't connect at a rate faster than 10 clients per second, and it stops attempting ANY new connections any time there are 10 unanswered connection attempts. (This is a security limit added by Microsoft.) So the problem isn't as bad as some might imagine.
1. The number of connections actually established is far less than many imagine; and
2. The rate at which clients can seek connections is usually limited.
Keep in mind that a lot of these kids have the cheapo router with just a couple of MB of RAM available for maintaining their own NAT tables and other operating variables/caches and etc.. With a few exceptions, most of these work under normal P2P use.
--
Robb Topolski -= funchords.com =- Hillsboro, Oregon
"We don't throttle any traffic," -Charlie Douglas, Comcast spokesman, on this report. | |
| | | | | |
See 6 replies to this post | |
| | | | espaeth
Misanthrope
Premium
join:2001-04-21
Minneapolis, MN
·Comcast
·Embarq
| said by koitsu :I wouldn't be surprised if a hundred users downloading the same torrent (a thousand peers each) on a single Juniper M20 could cause the routing engine to slow significantly. So from *that* perspective, P2P does in fact slow down a network. But in that situation, you're overselling capacity, and should look into getting another M20. It doesn't work that way... at all. Comcast doesn't use Juniper hardware, but the Cisco 7600s they use share a commonality with the M20 in that they're both hardware-based routing platforms. These platforms use TCAM to perform pattern matching that can do access control lists / address translation / NetFlow tracking at line rate.
With standard memory (like that in your PC) you supply an address location and then you can read or write the contents of the memory at that position. TCAM is pretty much the opposite of that -- you give it a bit pattern and it returns the index position where that particular entry exists. This process is extremely fast because it is baked into silicon as a specific operation on an ASIC and does not have the overhead of being a process running in software on a generic-use CPU; it can complete a full lookup in just a few nanoseconds. (significantly faster than the network processing demands of microsecond/sub-millisecond timing)
Whether your hardware based router is tracking a single flow, or the maximum number of flows their TCAM can store patterns for there is absolutely no measurable impact to forwarding performance. The most common use of state tracking on standard routers is gathering NetFlow traffic statistics data. The Netflow tracking flow looks something like this:
You gather statistics for as many flows as your memory will allow and simply forward anything else once you run out of memory to store additional patterns. The lookup time is roughly the same if the pattern matches or not, and the counter increment process uses a negligible amount of ASIC processing time.
The real issue is fairness in TCP flows when the link starts to become saturated. Each TCP session is like a car on the freeway; trying to go as fast as the road will allow but constantly having to adjust for other cars. TCP is greedy just like cars on the freeway as well, as soon as a gap opens up it speeds up to immediately take up that extra space. When congestion starts to occur on a link segment every TCP session slows down to roughly the same top speed because every session follows the same rules when faced with congestion. That's where the problem with BitTorrent really starts to come into play. Normally with TCP sessions slowing down in roughly the same manner that is a relatively fair situation on the network in terms of distribution of impact, but in the case of BT where you have several flows this fairness rapidly disappears. Say congestion gets to the point that flows can't grow to be faster than 40kbps. For you with BitTorrent you can still max out your upstream connection because you're establishing multiple TCP connections with 40kbps each. For me uploading content to my web server via FTP, the most network resources I get out of the deal is 40kbps because I'm only uploading my content in a single flow.
That's why closing down connections is effective: it gets the TCP-Flow per user ratio to be more consistent across the board and helps to give each user a fighting chance at a better share of the available bandwidth. | |
| | | | | |
koitsu
Premium
join:2002-07-16
Mountain View, CA
| Re: Does packet forging reduce network traffic? said by espaeth :It doesn't work that way... at all. You're always here to make my life hell, man. Just kidding.
Thank you for the crash course on hardware-based routing. I've always wondered how that was done and whether or not it was just a buzzword for "dedicated routing engine card" for offloading routing vs. on the main CPU (which I believe M20s and M40s use the equivalent of a Pentium II).
I've known Cisco uses hardware-based routing for quite some time, and was always told it was "incredibly fast" but never was given an actual description as to how it worked, so again, thanks!
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer. | |
| | | | | | | espaeth
Misanthrope
Premium
join:2001-04-21
Minneapolis, MN
·Comcast
·Embarq
| Re: Does packet forging reduce network traffic? said by koitsu :You're always here to make my life hell, man. Just kidding. Just trying to keep the facts in line.
said by koitsu :Thank you for the crash course on hardware-based routing. I've always wondered how that was done and whether or not it was just a buzzword for "dedicated routing engine card" for offloading routing vs. on the main CPU (which I believe M20s and M40s use the equivalent of a Pentium II). Ternary Content-Addressable Memory is really the magic that makes hardware routing possible. It really started with Ethernet switches taking advantage of this solution to rapidly determine which port a particular frame is destined towards. In hardware routers today you will have several TCAM instances for Netflow, the adjacency (ARP) table, the forwarding table (ie, Cisco Express Forwarding/CEF), and Access Control lists. The CPU on these boxes only handles the tasks of running the user interface to the router, running the routing protocols and building the associated forwarding table in TCAM after routes are updated, and handling maintenance traffic like SNMP and ICMP. | |
| | | | | |
funchords
Robb
Premium,MVM
join:2001-03-11
Hillsboro, OR
·Verizon Online DSL
·Skype
·Comcast
edit:
February 22nd, @08:36PM
| said by espaeth :When congestion starts to occur on a link segment every TCP session slows down to roughly the same top speed because every session follows the same rules when faced with congestion. I'm with you so far.
said by espaeth : That's where the problem with BitTorrent really starts to come into play. Normally with TCP sessions slowing down in roughly the same manner that is a relatively fair situation on the network in terms of distribution of impact, but in the case of BT where you have several flows this fairness rapidly disappears. You (and many, many others) are forgetting the fact that the first bottleneck for a residential Comcast user is his modem. You can't send any faster than that modem will accept data -- and that modem is your residential gateway. When it's maxed out, the only open flows you are restricting are your own. Maxing out your cable modem does not affect your neighbors at all.
From the modem to the CMTS, its DOCSIS. This is the second bottleneck, but it doesn't matter for two reasons. First and foremost, the paragraph above. Secondly, since it's not TCP/IP, then it doesn't know about sockets or how many you have nor where they are going. Basically, if your DOCSIS node is saturated, your byte-for-byte throughput is impacted by the same X% regardless of how many TCP/IP sockets you have open. DOCSIS can't give someone with 40 sockets an advantage because it doesn't know about sockets. It only has one flag that says "I have data to send -- tell me when." There is no flag that says "I have 40 sockets with data to send"
The third bottleneck is the Comcast network gateway. Unlike the other two, this TCP/IP to TCP/IP bottleneck is not about technology limits, it's about money. If its irrelevance is not obvious, I'm happy to discuss -- but at that connection point, there's nothing different from Comcast's network to Verizon's network.
WARNING - SHOCKING NEWS AHEAD
Web Browsers open two uploading ports simultaneously to each server to a page. As soon as they're done, they close the port. Typically 2-5 ports are actively uploading at the same time.
Now, here's the shocking piece of news to everyone: Most BitTorrent peer connections are idle at any one time -- SUBSTANTIALLY USING NO BANDWIDTH. Regardless of how many connections you have open, you're only going to be uploading on 3 or 4 sockets at a time -- the rest are choked and are using 4-9 Bytes every 20-60 seconds waiting for their turn.
When congestion happens on a TCP/IP segment, then you are right that all of the sockets that are actively using bandwidth on the bottlenecked segment will be decreased to a lower, roughly equal amount. For us using Comcast, that's the segment between your computer and the Cable modem. But people SHOULD NOT get the idea that because a P2P application has 40 open sockets and a web browser has 5 that P2P has a 40/5 advantage across the Internet. The only sockets that matter are the ones using a high amount of bandwidth (ones faster than the new congestion-created ceiling will eventually be), and in CATV-Internet, the only ones that really matter are the ones that are uploading from your own side of the modem.
This whole Sandvine thing is a farce. It's about saving money paid to backbone vendors -- money to transit the bandwidth customers have already purchased. It has nothing to do with DOCSIS and it has nothing to do with network congestion.
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Robb Topolski -= funchords.com =- Hillsboro, Oregon
"We don't throttle any traffic," -Charlie Douglas, Comcast spokesman, on this report. | |
| | | | | | | espaeth
Misanthrope
Premium
join:2001-04-21
Minneapolis, MN
·Comcast
·Embarq
| Re: Does packet forging reduce network traffic? said by funchords :You (and many, many others) are forgetting the fact that the first bottleneck for a residential Comcast user is his modem. You can't send any faster than that modem will accept data -- and that modem is your residential gateway. When it's maxed out, the only open flows you are restricting are your own. Maxing out your cable modem does not affect your neighbors at all. Saturation on the upstream is an "n-user" problem. My car is only so big, and I can get on the freeway at 3am and maybe not run into a single car. When I get that same freeway at 7:30am all of a sudden it's bumper to bumper and running slow. You can't look at singular TCP connections, you have to look at the situation once critical mass is achieved.
said by funchords :From the modem to the CMTS, its DOCSIS. This is the second bottleneck, but it doesn't matter for two reasons. First and foremost, the paragraph above. Secondly, since it's not TCP/IP, then it doesn't know about sockets or how many you have nor where they are going. Basically, if your DOCSIS node is saturated, your byte-for-byte throughput is impacted by the same X% regardless of how many TCP/IP sockets you have open. DOCSIS can't give someone with 40 sockets an advantage because it doesn't know about sockets. TCP is an end-to-end stateful protocol with sequencing and flow control. It adjusts its flow rate based on a number of criteria including max window size, round-trip time, and observed packet loss. If the DOCSIS node is busy there will inevitably be additional queuing delay, and TCP sensing an increase in round-trip time will back off on the transfer rate a bit. The maximum transfer rate (per second) for a TCP session is the (TCP Window) * (Number of Round-trip intervals per second). Assuming the TCP Window is artificially limited (true for the vast majority of Windows boxen) then queuing delay will result in a steady decrease in the performance of each TCP flow because of the reduced number of round-trip intervals per second.
said by funchords :The third bottleneck is the Comcast network gateway. Unlike the other two, this TCP/IP to TCP/IP bottleneck is not about technology limits, it's about money. If its irrelevance is not obvious, I'm happy to discuss -- but at that connection point, there's nothing different from Comcast's network to Verizon's network. This whole Sandvine thing is a farce. It's about saving money paid to backbone vendors -- money to transit the bandwidth customers have already purchased. It has nothing to do with DOCSIS and it has nothing to do with network congestion. The MSO to Internet gateway points are the cheapest part of the whole service equation. Unless Comcast is being intentionally deceptive with their PTR names (highly unlikely) you can pretty accurately piece together the bulk of their network environment.
The uBR CMTS hardware connects to the UR01/02 user routers via Gigabit ethernet (hence the gi-2-3 PTR records, signifying the gig interface in slot 2, port 3 of the 7600)
The UR01/02 gear connects to the AR01/02 area aggregation routers via 10GigE (hence the te-2-3 PTR records)
The AR01/02 routers connect to their transport peers via 10GigE in the vast majority of cases.
The cost isn't in this part of the network because you get a better per-mbps pricing with bigger circuits and large commits, and having 14 million pairs of eyeballs as a bargaining chip doesn't hurt either. If you look at how Comcast is routing their traffic they have fewer egress points for their national footprint than there are states in the nation. Just skim the Comcast forum and gather traceroute statistics and you'll find that there are only a few dozen external connection points to the Comcast network. It's not the modest handful of Internet connections that drives your costs, it's the hundreds of CMTS units and thousands of nodes deployed across the cable plant. When they turn up additional capacity for Internet peering it can be used by every single customer in the region; the cost/benefit ratio is quite favorable. It's also easily expandable because the limited number of peering locations make for nice places to consolidate fiber interconnects to their transport vendors. This means that it's easy to get more capacity in a big hurry. Need another 10GigE? You can rapidly provision new capacity until you run out of DWDM wavelengths and physical pairs of fiber.
The cable plant is a completely different story: there's a finite amount of frequency space and the frequency range that can be used for the upstream traffic is a minuscule chunk of that. The common example of a node layout is a central hub with "strings" running North, West, East, South. When service was originally built out all 4 strings likely shared the same upstream and downstream channels for HSI, and as the service grew these were eventually split out. That means if you have upstream channes 1-4 available, you can break them out so that North 1-4 are different than South 1-4, etc. The real problem comes when one segment like "West" becomes heavily loaded; at that point once you are out of frequency space your only option for providing more segment bandwidth is to split the copper plant and insert another HFC node. At that point you're talking about 5-6 figures when you work out right-of-way for the fiber path, laying additional conduit, pouring the cement slab to hold the node (if required), getting power to the node, the cost of the node itself, plus the cost of additional CTMS ports at the head-end to support the fiber connections for that node. The labor involved isn't simply a "cut and connect" operation either, as all of the amplifiers for that entire segment will need to adjusted or in some cases moved to more ideal positions on the coax plant.
The major cost of providing the service is in the last mile, not the head-end. | |
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funchords
Robb
Premium,MVM
join:2001-03-11
Hillsboro, OR
·Verizon Online DSL
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edit:
February 24th, @07:48PM
| Re: Does packet forging reduce network traffic? As far as I can tell, we mostly agreed, except in two areas -- and one of those areas, I was wrong -- I got angry.
So yeah, I concluded by tirade with "It's about saving money paid to backbone vendors." Just earlier that evening, I was explaining to one of the lawyers for tomorrow's hearing about Comcast's likely motivations for using Sandvine and I gave him a totally different (much less hotheaded) answer.
Here's what I both hope and fear: that the FCC issues a temporary order of some kind and shuts down these devices. I hope it because I hope it is so obvious on its face how wrong it is for Comcast to use this method of "network management." I fear it because I'm afraid that all Cable-TV Internet Providers have had these boxes for 1-2 years, and broadband performance across 2-3rds of the nation is going to take a dump until the cable providers make the necessary upgrades.
I'm "on the record" as requesting the immediate injunction, and I plan to stay that way (it will be too late to change it in 3 days, anyway). Extending a wrong does not make something less wrong. Either freedom is going to take a hit, or it's going to take real time and pain to make up for 1-2 years of neglect.
quote:
If the DOCSIS node is busy there will inevitably be additional queuing delay, and TCP sensing an increase in round-trip time will back off on the transfer rate a bit.
Yes, but again, the impact will be felt across the XXX number of customers, not the YYY number of streams.
I have 10 streams going "full bore", my neighbor has five streams going "full bore", and neither of us are saturating our modems somehow. But due to a hundred other factors, our neighborhood shared upload pool becomes saturated -- the number of sockets we had open isn't going to matter. DOCSIS doesn't know about sockets. Unless TCP/IP starts its recovery thing, we'll all grind down at the same ratio.
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Robb Topolski -= funchords.com =- Hillsboro, Oregon
"We don't throttle any traffic," -Charlie Douglas, Comcast spokesman, on this report. | |
| | | fiberguy
My views are my own.
Premium
join:2005-05-20
| So that's the reason why when I downloaded Spiderman III from your computer it took forever!! What's your address so I can sue you! How dare you purposely slow my free movie download for your own selfish reasons..  | |
| | gal
join:2006-12-21
Toledo, OH | They are actually sending packets to impersonate one of the machines asking the other to stop sending information therefore stopping the service. It can be restarted if the machines continue to try after a certain peroid of time. | |
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