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Bufferbloat — the Submarine That's Sinking the Net
gottabeme writes "Jim Gettys, one of the original X Window System developers and editor of the HTTP/1.1 spec, has posted a series of articles on his blog detailing his research on the relatively unknown problem of bufferbloat. Bufferbloat is affecting the entire Internet, slowly worsening as RAM prices drop and buffers enlarge, and is causing latency and jitter to spike, especially for home broadband users. Unchecked, this problem may continue to deteriorate the usability of interactive applications like VOIP and gaming, and being so widespread, will take years of engineering and education efforts to resolve. Being like 'frogs in heating water,' few people are even aware of the problem. Can bufferbloat be fixed before the Internet and 3G networks become nearly unusable for interactive apps?"
Latency is bad? Bigger buffers = more latency?
I'm so glad the term has been defined so that I know what the hell we're talking about here. Oh wait, no it hasn't.
Okay, then I'll RTFA. Oh wait, two screens worth of text later and it still hasn't.
I'd like to change the topic now to the submarine that's sinking the English language: jargonbloat.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
Just start RTFAing: "In my last post I outlined the general bufferbloat problem."
Follow the link:
"Each of these initial experiments were been designed to clearly demonstrate a now very common problem: excessive buffering in a network path. I call this bufferbloat
I read TFA and I'm not seeing the problem. He can't duplicate this issue unless he maxes out his connection and then his latency goes to hell. No shit Sherlock, that's what happens when your pipe is full and the packets have to wait in the queue to be transmitted. Am I stupid or could he avoid this issue entirely by using QoS and/or rate-limiting his connection to some amount <100% of it's maximum throughout? I have QoS at the office that keeps our connection from pegging (it's limited to around 75% on the download and 90% on upload) and have never once encountered an issue with latency or jitter. At home I only throttle the upload (to 90% of maximum) and have successfully ran VPNs, bittorrent uploads and VoIP calls all at the same time without any headaches.
Really, what's the problem here?
I want peace on earth and goodwill toward man.
We are the United States Government! We don't do that sort of thing.
RAM is cheap.
High speed uplink is not cheap.
Peering agreements are manipulative, expensive, and sometimes extortionate.
So...
The poorly designed, poorly peered, under allocated back haul links can't handle the traffic that routers want to push through them -- but since RAM is cheap, operators just add RAM to the buffers so that when those back-haul lines slow down for a second the packets can get pushed through.
And we're blaming the buffer for the problem?
The problem with quotes on the internet, is that nobody bothers to check their veracity. -- Abraham Lincoln
You haven't read the article (or the many others around on LWN.net on the same topic). Basically, large buffers in networking gear, from DSL routers on your home network through to ISP's, mean that interactivity is *shite*. You might download Gb's but in terms of interactive applications it's useless and we're facing ever-increasing latency and problems through wanting to cope too much with errors and delays (e.g. huge buffers to keep resending instead of just letting packets drop and having TCP sort it out by retransmission). TCP windows never shrink because errors and buffered and retried so much from intermediate devices that any sort of window scaling is worthless because it doesn't *see* any packet-loss.
Same devices, smaller buffers, everything works fine and "faster" / "more responsive" all around. It actually would *save* money on new devices because you don't need some huge artificial buffer, you can just drop the occasional packet. But the problem is so deeply embedded into run-of-the-mill hardware that it's almost impossible to escape at the moment and thus EVERYONE from large businesses to home users are running on a completely sub-optimal setup because of it. Almost every networking device made in the last few years has buffers so large that they cause problems with interactivity, bandwidth control, QoS, etc. It's NOT just that a "faster connection" solves the problem - we are getting a percentage of optimal service that's steadily decreasing as buffers increase even though we're improving all the time. That's the point. And it *is* caused by memory prices because memory is so cheap that a huge thoughtless buffer costs no more than a tiny, thought-out buffer.
This is an excellent explanation of what issues are happening here. I can clearly see that this is an issue, and the problem is something that over time will impact everybody.
The problem is really focused on trying to deal with differences in bandwidth between computers... always a problem but in this case trying to match up slow connections with fast connections is particularly difficult. Since memory is cheap, a 1 GB buffer certainly can be found in some devices now and perhaps much more. I don't see this example as being really too far off the mark in the near future.... which is the point being raised and why buffer bloat is such a big deal.
More to the point, some of the complaints that triggered the "quality of service" debate are rooted in this problem. As mentioned in the original article triggering this whole slashdot thread, setting up "quality of service" priorities only creates multiple buffer queues.... it doesn't solve the problem of the monster queue to begin with. That is why the author of the blog post suggests that the debate over network neutrality is not based upon the real problem that is facing network engineering and why it is a political solution in search of a problem.
It takes awhile to "grok" this problem, but once you do it becomes obvious why this is such a huge deal.
2. QoS used that way is a hack to work around an issue that doesn't have to be there in the first place
3. How do you determine the maximum throughput? It's not necessarily the official line's speed. The nice thing about TCP is that it's supposed to figure out on its own how much bandwidth there is. You're proposing a regression to having to tell the system by hand.
4. QoS is most effective on stuff you're sending, but in the current consumer-oriented internet most people download a lot more than they upload.
While the Internet in-theory is beautiful, our modern implementation really is a series of layered hacks. And the solution to Bufferbloat is going to be another hack. You're crazy if you think that the solution to the Bufferbloat 'problem' is going to be some fundamental redesign of the TCP protocol (how would you force 10 people to use it?), or the total re-architecture of millions of consumer devices to remove buffering. You're also crazy if you think the ISPs and backbone providers are going to stand by while this thing kills the Internet.
So the question is: which hack will it be? The GP poster already identified one that works well enough --- using QoS to control flows. Your final objection about content providers stressing connections is the real one. But there's some probably a good hack to deal with it --- or more likely a series of hacks, some at the content providers themselves (e.g., Netflix), some in the backbone, and some at your ISP. It won't be elegant, but it will keep this problem from ever becoming anything more than a few cranky blog posts.
It doesn't help that massive numbers of people actively insist on breaking protocols which specifically exist to alleviate some of these types of problems.
Far too many people ignorantly block all ICMP traffic. As a result, the network path in between the two communicating hosts are forced to buffer more data as the destination host becomes saturated. Worse, this type of filtering has a tendency to quickly compound, which in turn creates the exact type of bufferbloat he's describing.
I wish people would understand there is a difference between, "No route to host", and a black hole. When you find a black hole, chances are really good you've found a host. As such, purposely breaking protocols for people to have an imagined increase in security only breaks the Internet as a whole when it becomes a wide spread tactic. And before people start rattling off that it opens a whole new can of worms, please realize that unlike in the past, stateful firewalls are extremely common today - so no.