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