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."

98%

Plz seed

Re:98%

Nah, it would melt the internet tubes.

fairness

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

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

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

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.

That behavior needs to be driven by some timing and retry logic. Also, hosts need to determine how fast they can fire these UDP packets at each other. Those are the most basic fundamentals of transmitting bulk data over a packet network. You really would be reinventing some subset of TCP.

I think what he's trying to say is the TCP connection often gets dropped completely, for example the host just goes offline, or is bogus and transmitting false data. Bittorrent needs to account for this anyway by re-requesting packets from the network, so they have implement the retry logic differently that TCP anyway.

Re:fairness

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

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

To say that TCP is optimal at dealing with congestion is to say that individual packets are always a good representation of the data blocks being sent and received at the application level, and that best thing that any application can do when expected data doesn't arrive is to wait on it to be retransmitted, with the network layer queuing up all subsequent intact packets.

Once again, this behavior is guaranteed to be completely wrong for anything but toy command-line applications that fit on a single page in the back of a musty-smelling manual.

Re:fairness

And all this time I thought that spam was going to cause the Internet to melt down. Maybe we need new terminology. Instead of "melt down", it should be "Global Internet Change".

Re:fairness

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

If I pay for 10Mbps download speed

No, you don't. A dedicated 10 Mbps link would run thousands of dollars a month (a T1, which is 1.5 each way, is ~$300 in the US) and most consumers can't swing that sort of dedicated line. Instead, you paid for a connection that is 10 Mbps maximum and you knew damn well that you would be sharing it with others in your neighborhood. How else could you rationalize paying only $60/month for faster-than-T1 level service?

Pretending that you don't understand the difference between a dedicated line and a shared line is utterly unconvincing to me.

This is a good thing

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:This is a good thing

Except that probably isn't what will happen.

Let's use Comcast as an example.

Their target customer "surfs the web", and checks their email.

Their high-maintenance customers, who complain about latency issues, throughput, etc. are the ones who use UDP in any significant volume.

UDP is used for online gaming, VoIP, etc. They will just start to deprioritize UDP, which is bad. 99% of customers won't notice the difference, but we will.

don't see it myself

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...

Scare Mongering?

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?

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

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

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?

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.

Re:Well Duh

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:Well Duh

I don't use bittorrent, but frankly those (most of those) people are paying for unlimited internet access. At least that is how it was marketed. What I do uses is streaming video for alot of the shows I had been watching on TV. If my ISP is selling me unlimited internet and they decide not to deliver, I want a rate cut. If they don't have the capacity to reasonably provide what they sold me, they shouldn't be allowed to legally weasel out of providing it without penalty.

Re:Ummm

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

Re:File Service Protocol

They also said the same thing when UDP streaming internet video became a hit-- their servers couldn't keep up.
They just had to upgrade.

Hopefully the same thing will happen now.

Re:File Service Protocol

I think this whole thing is just hinging on them upgrading the darned infrastructure. The ISP's have sat fat and lazy for too long just selling you a "faster pipe" as the last mile of cable got faster. All that while though the baseline infrastructure has been receiving upgrades as a snail's pace, while at the same time more and more users are jumping onto the net in droves.

They pocketed far too much money that should have been allocated to network upgrades to actually support increasing TRUE capacity - not just a theoretical burst speed that you might maybe be able to get for 3 or 4 minutes back home.

It's like that lazy employee who has 3 months to do 1 week's worth of work. He puts it all off until he has 2 days left, and then starts to moan about how he doesn't have enough time to do all this work. Well, at this point, he's right. It's his own fault though. My boss has a nice poster in her office that I think applies here: "Lack of planning on your part does not constitute an emergency on my part."