Bittorrent To Cause Internet Meltdown

Gimble writes "Richard Bennett has an article at the Register claiming that a recent uTorrent decision to use UDP for file transfers to avoid ISP 'traffic management' restrictions will cause a meltdown of the internet reducing everybody's bandwidth to a quarter of their current value. Other folks have also expressed concern that this may not be the best thing for the internet."

Comments

98%

[Anonymous Coward]

Plz seed

Re: 98%

[mcpkaaos]

Bald kid: Do not try and manage UDP connections. That's impossible. Instead... only try to realize the truth.
Ted: What truth?
Bald kid: There is no connection.

fairness

[seanadams.com]

If you're going to transfer files over UDP then you need to build some TCP-like protocol on top of it. The article doesn't say exactly how BT works in this respect, but he's probably right. There's no way that BT's protocol could be as sophisticated as TCP, given its 30+ years of development.

Most people don't appreciate how amazingly well TCP's flow control works in terms of maximizing link utilization in a way that is fair to all network users. We really don't need is an arms race of new, greedier protocols.

However, one thing to realize about P2P is that because there are often dozens of active TCP connections transmitting from one machine, fairness goes pretty much out the window anyway. An alternate protocol could conceivably improve on this by applying flow control to the aggregate throughput for the whole "bundle" of connections, rather than each connection individually. This would improve fairness and also increase efficiency because you wouldn't have a bunch of TCP streams individually trying to grow their windows, causing packet losses.

Re:fairness

[Ed Avis]

If you're going to transfer files over UDP then you need to build some TCP-like protocol on top of it.

Not really. You would need that if you were transferring a file from one computer to another. But Bittorrent scrapes together little bits of file from lots of other computers. If a packet is lost here and there, that bit of file is naturally requested again, probably from a different machine. That's just a consequence of the way Bittorrent works.

However, one thing to realize about P2P is that because there are often dozens of active TCP connections transmitting from one machine, fairness goes pretty much out the window anyway.

There's no reason in principle for this to be the case; obviously, metering of bandwidth should be by subscriber according to money paid, not by some arbitrary and easily manipulated value like number of open TCP connections.

Re:fairness

[Man On Pink Corner]

There's no way that BT's protocol could be as sophisticated as TCP, given its 30+ years of development. Most people don't appreciate how amazingly well TCP's flow control works in terms of maximizing link utilization in a way that is fair to all network users. We really don't need is an arms race of new, greedier protocols.

TCP gets a lot of credit it doesn't deserve. It enforces bad design -- most client/server applications should be either stateless or session-based, rather than connection-oriented. Anything that even vaguely resembles a streaming application shouldn't even consider TCP. Finally, TCP's connection model is almost guaranteed to be suboptimal for any application that does require one.

What are the odds that HTTP, FTP, SMTP, and BitTorrent will all work optimally over TCP? Slim to none, and none is still waiting for Nagle.

Re:fairness

[Opportunist]

Not really, actually.

TCP enforces and faciliates delivery certainty. You may be sure that a packet arrived. It gives you everything to make sure some packet arrives in time, if it's fragmented and arrives in the wrong order it's reassembled and all the other little bits that are quite useful when you're normally transfering data.

This doesn't really apply to Bittorrent and the way it works. Bittorrent by its very nature transfers little parts of files. Parts in a size that can easily avoid fragmentation. Parts where it doesn't really matter whether they arrive at all. If they don't, the requesting machine will simply ask for it again. Maybe now, maybe later, maybe even from another source.

Yes, TCP has its merits and sometimes they are even used sensibly. Don't make me start about all the cases where TCP is used without any reason because neither packet size matters nor certainty of delivery is a criterion, but it's just "easier". But BT can well work on UDP and even generate less overhead and thus actually less traffic than it does today.

Face it. QoS, Netneutrality and traffic shaping or not: People will find a way around it. And when the choice is encryption and wrapping BT packets in even more overhead (because, say, the provider will only allow HTTP-Packets at full speed) or using UDP, it's a no brainer. For both sides.

Re:fairness

[nmg196]

Not really. You would need that if you were transferring a file from one computer to another. But Bittorrent scrapes together little bits of file from lots of other computers. If a packet is lost here and there, that bit of file is naturally requested again, probably from a different machine.

No... you're getting confused between network packets (a kilobyte or two) and bittorrent's blocks (many kilobytes). Each bittorrent chunk is transferred using many network packets. If you're going to transfer those chunks using UDP, you need to sort out the packet order and do all the missing-packet checks and retries etc yourself. So you still DO need to build some kind of TCP-like protocol on top - even just for the error checking.

Re:fairness

[jandrese]

The problem is that TCP self regulates and throttles itself back in the face of network congestion. UDP does not, it just blasts packets out as fast as you can feed it. Without some sort of flow control, you could disproportionally hurt TCP flows (which are trying to be good and throttling themselves back when they hit a bottleneck) by your big ugly UDP stream.

That said, the bottleneck for end users is typically the uplink on their last mile connection, so this probably won't bring the internet down or crash any ISPs, but it will make life worse for people sharing the connection.

Fun fact: The original implementations of TCP did not have flow control (it was on a test network after all). It did not take long for it to become apparent that flow control is a necessary feature. A few network meltdowns made the case quite well.

Re:fairness

[Opportunist]

Then maybe they should be sold as such.

Look, all I want is to get what I get sold. If a line is sold as a 10mbit line, I will expect it to be a 10mbit line.

If I sell you a garage for 2 bucks a month, you might wonder but you will probably take the deal. Then you come around and notice that someone else is already standing in the space I sold you, and I tell you that you're allowed to use that space to park your car but only when it's free. Would you be happy? I guess not.

People will expect to be able to use what you sell them. And some of them will even use it. They really want to use what they got allegedly sold! How dare they?

Re:fairness

[anothy]

it's true that the protocol stack would need to have some method of regulating retransmission, but i think the GP's point is that it's already there, in the BT applications. sure, it's not at the layer we tend to think it belongs, but when you're dealing with untrusted sources (as anonymous seeders inherently are), you've got to do that work anyway.
also, even if you ended up recreating a "subset" of TCP, that could still be fine. TCP is huge compared to UDP, and if you use UDP as a base for adding what you need, you can still come up with something much simpler than TCP; see, for example, RUDP. TCP's benefit is its ubiquity, but if you have the combination of a constrained enough environment and wide enough client distribution, that's less of a big deal. BT and uTorrent likely satisfy those requirements.

Re:fairness

[jandrese]

That misses the point. UDP senders don't know when they're flooding the connection, so they just keep doing it. A TCP stream would back off to try to be fair, but your UDP stream is just going to keep on blasting at full speed.

Think of it this way, you have a congested router that has 1mbps of available bandwidth. Normally you have 5 TCP streams sharing it at 200kbps each. Everybody is happy. Now you replace one of the TCP streams with your UDP sender which is configured to transmit at 800kbps. It will continue to pound the router with 800kbps worth of traffic while the TCP streams all throttle back to 50kbps. Now you're not playing fair, and there's nothing the other TCP guys can do about it because they're all trying to play fair still.

Re:fairness

[ShatteredArm]

Clearly whoever invented TCP did not properly understand game theory.

This is a good thing

[Gotung]

In the end this will be a good thing for the internet.

Forcing ISPs to treat all traffic the same, because they can't tell what is what, will be good for net neutrality.

You should get the bandwidth you pay for, regardless of what actually travels over it.

Re:A little extreme there, don't you think?

[FredFredrickson]

The problem is, that it could be ligitimate. Are you the judge and jury? Don't let something set a precedent that could affect our legal freedoms as well.

Re:Ummm

[Adriax]

Call in Mr Stevens, he's unemployed and looking for work.

don't see it myself

[myxiplx]

Well, since The Register don't seem to want to print my comment*, I'll repeat it here:

"I think this is a bit of scaremongering that's missing one vital point:

When an ISP throttles UDP packets because somebody is using excessive bandwidth, they'll be dropping packets *from that source*.

So while .torrent moving to UDP is going to affect VOiP and games, the effects of that will be *restricted to the person using excessive bandwidth* via bittorrent. There's no reason it would affect anybody else, and I doubt ISP's are going to be dumb enough to block packets at random.

Unfortunately that kind of blows the articles entire premise out of the water."

Myx

* Posted at 12:40pm, ten minutes after the article appeared, at a point where there were no other comments on the article. 3 hours later there are 37 comments, but no sign of mine. Now it may be that they've just been overwhelmed with comments, but I'm a suspicious soul at times...

Re:A little extreme there, don't you think?

[MBGMorden]

It could be, or it could not be. To me, that's not even an issue that should involve the ISP. I pay them for bandwidth, not to be my nanny. It's akin to a car dealer that keeps checking into to make sure I'm not running drugs in the car I bought from them. Right or wrong, legal or illegal, I paid for the car/bandwidth, so butt the hell out or I'm going to either find another seller who doesn't bother me about what I'm doing, or just ignore your and route around your interference.

I want an ISP that sells me a pipe. That's it. What I send down it is of no concern, and if I pay for 5Mbps or whatever other arbitrary number, then I can't possibly "steal" bandwidth from other users because by definition I'm already limited to the amount that you sold me. If you can't provide it then don't sell it, because some users will use what you sell them. If you took the current ISP business model to any other industry you'd be laughed out of town, yet they get away with it. Can you imagine signing up for a "3 DVD's at a time" plan from Netflix and then when you actually check out 3 at a time they start bitching up a storm because "You're hoarding the DVD's!!! None of the other customers will be able to rent any of them!!!". Of course not. Because like most industry's they understand that if you sell a capacity you better damn well be able to meet it.

Re:Well Duh

[MasterOfMagic]

Sounds like the ISPs should have used the tax incentives we gave them to increase network capacity and reach to, you know, increase network capacity and reach. If they had done that years ago to keep pace with the growth of their network traffic, they wouldn't be in this situation.

But no, of course, it has to be the person who uses their connection's fault.

I pay for a pipe. My ISP should take no interest in the source or destination or type of service connections in this pipe. Anything else is just allowing the system to be used abusively.

It isn't appropriate for legitimate bittorrent users to be driving other TCP off the network.

The only way the BitTorrent use can drive other users off to the network is if the ISP's network is misconfigured or is being overutilized due to too much overselling (you have to have some overselling, not everyone is on 24/7). ISPs that have their shit together will have their network designed to handle expected and future traffic growth such that all of their customers can use what they paid for.

you just want to bully other people out of their bandwidth so you get more

They paid for their bandwidth and I paid for mine. I have a cap on my connection speed; they do as well. The only difference is that their YouTube videos load instantly and my BitTorrent transfer is knee-capped. Who is the bully here?

This isn't the right way for BitTorrent to move forward

What is the right way to move forward? Accept that there are two levels of Internet traffic: "clean, good, wholesome non BitTorrent traffic" and "dirty, evil, corrupting BitTorrent traffic"?

Re:A little extreme there, don't you think?

[Chas]

Don't even pretend that most bit torrent traffic is legitimate and legal.

So what? Piracy is a social problem. Blocking BT, which IS being used legitimately, is a wrong-headed attempt to use technology to "solve" a social problem.

And in this case, they're trying to do it on the most flexible network in the world, one that's SUPPOSED to route around problem areas.

Scare Mongering?

[Concern]

This sounds like the basest kind of scare mongering, relying on a basic ignorance of the way networks work.

UDP is not any less filterable than TCP. To even make this argument, the reasoning is so contorted as to be silly. In either case, one uses a router to inspect packets and decide what to do with them. ISPs will simply go as deep through the envelopes as they like; they already do. With that knowledge they will do whatever is allowed by law. At present, almost anything is. If they abuse that power too foolishly, then it will start to be taken away from them.

And in the meantime, whoever they filter will tweak to retaliate, and it will always be a race. As far as I can see, this is just the ISPs (or their proxies) stopping at one random lap and crying how unfair it all is.

Why ignore the real issue here? If you sold a teenager in Topeka unlimited use of a large pipe, but now cannot handle her actual unlimited use of her large pipe, then you just need to start cutting better deals.

It's as simple as that.

If the teenager cannot actually use her fat pipe, 100% of the time, then stop lying about what it is you have sold to her. Either charge more or advertise less. It's as simple as that.

When I as a CEO, and millions of others like me, buy #MB upstream and #MB downstream, and utilize it 100%, 24/7, no one quakes over the calamity of the internet backbone melting down.

All of this discussion over filtering is really a discussion of pricing. And the fact that we are talking about it in the wrong terms is creepy.

Believe me, you do not want a bunch of unaccountable telecom bureaucrats playing god with the backbone. You want a free market making these decisions.

Re:A little extreme there, don't you think?

[blackfrancis75]

that Car Dealer thing is a terrible analogy. With the ISP model, everything you do with the 'bandwidth' you paid for goes through *their* systems first - they're understandably concerned that the drugs you're running across their borders are going to reflect badly on them in the long run.

Re:A little extreme there, don't you think?

[Anonymous Coward]

"that Car Dealer thing is a terrible analogy. With the ISP model, everything you do with the 'bandwidth' you paid for goes through *their* systems first - "

Which is bullshit, consider the post office, I order something online from a retailer, does this give the shipping company or government the right to open my mail and packages because it passes through their facilities? It's bullshit plain and simple. They don't have a right to watch and monitor what you send. It's just another cash grab disguised as "helping the consumer"

Re:A little extreme there, don't you think?

[adonoman]

The problem with bittorrent, is that it's MORE convenient than watching TV the old fashioned way. All the benefits of TIVO, except that I can use my computer (and keyboard) to specify which shows I want. I don't care which channels are broadcasting them, they just appear in the downloaded folder. I can watch from any computer in the house (or outside with a laptop). There are no DRM restrictions.

Ignorant much?

[burris]

The author of this article could have called or emailed Bram Cohen before writing this article, but then he wouldn't have had such sensational tripe to garner page views. If he had, he would have known that he has got it completely wrong. The switch to uTP is actually to make BitTorrent traffic more friendly to Internet traffic. You see, BitTorrent is trying to sell a content delivery service based on their client and the #1 complaint from their customers (businesses with content to deliver) and their customer's customers (end users) is that the BitTorrent DNA client seeding/downloading in the background hurts the performance of other applications. That's unacceptable if you're trying to sell an unobtrusive alternative/complement to traditional CDN.

Yup, good ol TCP is what is causing the problem. That's because BitTorrent breaks the assumption in TCP that one application needs only one TCP stream to do its work. To solve the problem BitTorrent acquired advanced congestion control techonology and it's inventors from "Plicto." The congestion control technology lets BitTorrent work without causing crazy latency for other applications on the box. BitTorrent is the responsible party here, recognizing the need for congestion control and implementing it in their protocol. Compare that to the author of this article who saw that BT was using UDP and assumed it was a naive attempt to get around ISP blocks.

The people who work at BitTorrent are smart enough to know that you can't beat your ISP by making a new protocol. The ISP sees all and can control all, even if it may lag behind the changes. That's why BitTorrent has been working to make changes where it can make a lasting difference, in the political layer of the network.

Re:A little extreme there, don't you think?

[jbezorg]

A car lease would be a more accurate analogy since you are only leasing the equipment.

Still, would you lease a car if it came with some guy who sat in the back seat and bitched about the miles you put on the vehicle? Maybe disable the car or limit how far you can travel during periods of high usage? Or said "No, you can't drive to X because X is the bad part of town and you can't possibly have a legitimate reason to go there"?

Re:A little extreme there, don't you think?

[lysergic.acid]

exactly. the argument espoused in this article is fundamentally flawed. in fact, it reads like it was written by an industry mouthpiece for the sole purpose of demonizing P2P users without absolutely no regard to logic or reality.

first off, as you said, it's impossible for the "download fiends" to actually use more than their share of bandwidth. if i have a 56K dial-up connection, there's no way for me to just decide, "hrmmm, this isn't fast enough for me. i think i'll be a dick and download at 9 Mbps by stealing bandwidth from my neighbors."

secondly, the author seems to be suggesting that everyone should use, or have access to, the exact same amount of bandwidth regardless of what they paid for, and that this level of bandwidth is decided by how much he personally uses/needs. well, that's very convenient for him and the ISPs. most of us are paying for 3+ Mbps connections, some people are paying for much more than that, but i guess we should all only be allowed to use 1~3% of the bandwidth we paid for because that's how much the author needs for his daily web surfing, e-mail, and posting of shitty articles on the web.

but why stop there? why not divide up internet bandwidth evenly between all 6.6 billion people around the globe. total global broadband internet bandwidth was estimated by Cisco to be 5,372 petabytes per month in 2008. divided up between 6.6 billion people means we all get a 0.00265869476 Mbps connection--that's each person's 'fair share' of internet bandwidth. of course, we would all have faster internet connections if it weren't for those darn greedy business/enterprise internet subscribers.

internet bandwidth isn't a fixed commodity, or a limited natural resource. technology has always been driven by consumer demand, and broadband internet is no different. it's bandwidth-intensive applications like P2P, streaming-video/audio, enterprise applications, etc. that create the push for infrastructure upgrades and ever-increasing connection speeds/network capacities. it's idiotic to accuse "power users" or "downloaders" of destroying the internet or stealing other people's bandwidth. it's even more idiotic to think that everyone should use as little bandwidth as you do, as there's always going to be a someone who uses even less bandwidth. artificially manipulating internet usage while overselling more and more is what's going to cause broadband connection quality to continue to decrease. meanwhile, there are ISPs in Japan and Korea who are doing the exact opposite by increasing network capacity and connection speeds to meet the growing demand. perhaps if ISPs in the U.S. and Canada focused on making technological progress rather than opposing it, we'd be rolling out 1 Gbps symmetric broadband connections too, rather than fussing over people actually using their 3-4 Mbps connections.

Re:A little extreme there, don't you think?

[i_ate_god]

It's called a society and there are acceptable and unacceptable behaviors. Being a filthy pirate and hogging all the bandwidth is not nor should be acceptable behavior even though you really like all the free stuff you get from it.

You can't hog all the bandwidth, you can only hog the bandwidth allocated to you.

What you're saying is this:

The ISP gave my neighbourhood 500mbps, and some asshole is using all of it so I can get on the internet, but still paying for it!

The realty is this however:

The ISP gave me personally 10mbps, and the asshole ISP is telling me now I can't use all of it but still expecting me to pay.

See the difference here?

Re:A little extreme there, don't you think?

[i_ate_god]

That's equivalent to saying "here is some electricity, but you can only use it to power your stove. If you use it for your air conditioner, you're violating our ToS and we'll cut you off"

It makes absolutely no sense.