Re: [Bloat] when does the CoDel part of fq_codel help in the real world?

[Pete Heist <pete@heistp.net>]

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> On Nov 27, 2018, at 9:10 PM, Dave Taht <dave.taht@gmail.com> wrote:
> 
> EVEN with http 2.0/ I would be extremely surprised to learn that many
> websites fit it all into one tcp transaction.
> 
> There are very few other examples of TCP traffic requiring a low
> latency response.

This is the crux of what I was looking for originally- some of these examples along with what the impact is on TCP itself, and what that actually means for people. I got that and then some. So for future readers, here’s an attempt to crudely summarize how CoDel (specifically as used in fq_codel) helps:

For some TCP CC algorithms (probably still most, as of this writing):
- reduces TCP RTT at saturation, improving interactivity for single flows with mixed bulk/interactive traffic like HTTP/2.0 or SSH
- smooths data delivery (thus meeting user’s expectations) by avoiding queue overflow (and tail-drop) in larger queues
- increases throughput efficiency with ECN (won’t tackle this further here!)
- reduces memory requirements for TCP buffers

Regardless of TCP CC algorithm:
- reduces latency for “non-flow” traffic, such as that for some encrypted VPNs


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