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Measuring QUIC vs TCP on mobile and desktop

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Re: Measuring QUIC vs TCP on mobile and desktop

#31

Post by vvanders »

IgorPartola wrote: post #24
_wmd wrote: post #10

Earlier quoted context omitted.

One of the major downsides to UDP is that it lacks any form of congestion control, so it's hard to justify QUIC's behaviour due to what it's built atop :) Meanwhile we're not talking about a small slice of bandwidth spent on SIP video calls playing unfairly, we're talking about 70% or more of all Internet traffic suddenly stampeding over every pre-existing protocol, they're the floodgates I'm worried about

Internet traffic or web traffic? Last I saw, Netflix and streaming video were the biggest slices of the pie.

My understanding is that most of that traffic is on the last mile due to them colocating the data at the ISP level[1].

[1] https://openconnect.netflix.com/en/

Re: Measuring QUIC vs TCP on mobile and desktop

#32

Post by puzzle »

_wmd wrote: post #16
chocolatebunny wrote: post #14

Earlier quoted context omitted.

Any chance you can point to a source about what happened in the 90s? I googled "congestion control what happened to the Internet in the early 90s" and it lead me no where.

The relevant keyword fu is 'congestion collapse', and it seems I may be misremembering what you can read about in the opening of Van Jacobsen's paper on congestion control ( http://ee.lbl.gov/papers/congavoid.pdf ) and some new algorithms that were introduced in the early-mid 90s, but perhaps someone with more clue knows what I was thinking of Finally it's not the first time Google did something foul like that in the…

Congestion collapse is what happened in the mid 80s that led to the creation of Jacobson's congestion control. He's at Google now, working on BBR (which their QUIC uses). Are you thinking of the early P2P days?

Re: Measuring QUIC vs TCP on mobile and desktop

#34

Post by ajdlinux »

jacksmith21006 wrote: post #9
_wmd wrote: post #4

Am I understanding things correctly? Because QUIC ramps up its bandwidth estimate more aggressively, it fundamentally competes unfairly with TCP? Is that an inherent property or something that can be fixed? Definitely it's too late to fix it on the TCP side Nice to know 7% of Internet traffic isn't playing fair with the rest just so one company's content loads a few ms faster! Really don't know how I feel about TCP i…

Google makes QUIC available for others to use if desired. QUIC sits on top of UDP so any other service that uses UDP you could make a similar argument they are optimizing for their service. Which everyone should be doing. Your post sounds more like it is driven more by some issue you have with Google then QUIC.

There's not much by way of production grade QUIC server software available at present.

Re: Measuring QUIC vs TCP on mobile and desktop

#35

Post by fulafel »

trevyn wrote: post #7
_wmd wrote: post #4

Am I understanding things correctly? Because QUIC ramps up its bandwidth estimate more aggressively, it fundamentally competes unfairly with TCP? Is that an inherent property or something that can be fixed? Definitely it's too late to fix it on the TCP side Nice to know 7% of Internet traffic isn't playing fair with the rest just so one company's content loads a few ms faster! Really don't know how I feel about TCP i…

QUIC fundamentally competes on a different level because TCP is broken for modern networks . From a network usage standpoint, there isn't anything "unfair" about it -- QUIC runs atop UDP, which is also a perfectly acceptable and publicly available Internet protocol. And Chrome will happily use QUIC with non-Google hosts, the real problem is that production-quality QUIC server software is currently rare outside of Goo…

This thinking is completely divorced from the principles and practice applied by the internet engineering community. The fairness benchmark is TCP, and if built on UDP, protocols are expected to respond to congestion & be fair to TCP streams.

Re: Measuring QUIC vs TCP on mobile and desktop

#37

Post by fulafel »

pixl97 wrote: post #20
gsich wrote: post #18

Earlier quoted context omitted.

Why is TCP broken?

Use TCP on a lossy network. Keep adding more users till you are using a majority of the bandwidth. Watch the network fail in congestion collapse.

Are you proposing a circuit-switched replacement for IP, or do you think the current network would serve better if there was no backoff in the face of congestion?

The ATM effort was a while back, but who knows, maybe it's time to try again.

Re: Measuring QUIC vs TCP on mobile and desktop

#38

Post by apenwarr »

This is a pretty disappointing article. It's really comparing a particular implementation (or maybe multiple implementations) of TCP congestion control, implemented in kernel space, with a particular implementation of QUIC congestion control, implemented in user space.

The article points out that both the QUIC and TCP implementations they tested are using CUBIC congestion control, but that's not enough information, because the article also points out that QUIC is using "more aggressive parameters." It's tough to say which parameters are better, but what's unsaid is that a TCP implementation could change their parameters and get the same congestion control results as QUIC.

The supposed poor performance of QUIC on resource-limited mobile devices is, as they point out, because it's a user space implementation that is thus more expensive. If QUIC becomes popular, I assume there will be kernel implementations that are as resource efficient as TCP. Meanwhile, it's a lot easier to to experiments (such as tuning CUBIC parameters!) when you don't have to reboot to install a new version.

It's also quite common for various TCP congestion controllers to completely fail to saturate busy links, because of various limitations. If that happens, it might be that QUIC is able to fill the empty space, thereby taking "more than its fair share" only because TCP wasn't going to use that share anyway. Since the article doesn't even say which TCP implementation it's comparing against, and doesn't say what happens when the TCP sessions are competing only amongst themselves with no QUIC present, it's hard to say what's going on.

The funny thing about all this is that, if they use the same congestion control (which seems to be the intention given that they are both using CUBIC and Google is separately trying to fix congestion control via BBR[1]), they should both be about equally fair. The performance benefits of QUIC are not even congestion control related!

[1] https://queue.acm.org/detail.cfm?id=3022184

[Disclaimer: I've worked with some of the people who wrote BBR and QUIC, so I'm biased.]

Re: Measuring QUIC vs TCP on mobile and desktop

#39

Post by apenwarr »

fulafel wrote: post #36

What's the current positioning of QUIC by Google? It predates HTTP/2, and Google hasn't been making noises about it lately. Is it being slowly phased out or just in a "let it be" status for now in Chrome?

It's being actively discussed at the IETF. Here's a doc that's last updated 2018-01-28: https://datatracker.ietf.org/doc/draft-ietf-quic-transport/

Re: Measuring QUIC vs TCP on mobile and desktop

#40

Post by apenwarr »

pixl97 wrote: post #20
gsich wrote: post #18

Earlier quoted context omitted.

Why is TCP broken?

Use TCP on a lossy network. Keep adding more users till you are using a majority of the bandwidth. Watch the network fail in congestion collapse.

That's actually a misrepresentation. TCP actually works pretty well on crowded networks; a major feature of TCP is to avoid congestion collapse. It doesn't always fully saturate busy/lossy networks, which is an area for improvement, but it's not the same as congestion collapse.

TCP BBR is an attempt to fix TCP congestion control so it can saturate busy/lossy networks more reliably. That doesn't require QUIC.

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