[Bloat] [Cerowrt-devel] DOCSIS 3+ recommendation?

Sebastian Moeller moeller0 at gmx.de
Fri Mar 20 09:46:29 EDT 2015

Hi David,

On Mar 20, 2015, at 14:31 , David P. Reed <dpreed at reed.com> wrote:

> The mystery in most users' minds is that ping at a time when there is no load does tell them anything at all about why the network connection will such when their kid is uploading to youtube.

	But it does, by giving a baseline to compare the ping tim under load against ;)

> So giving them ping time is meaningless. 
> I think most network engineers think ping time is a useful measure of a badly bufferbloated system. It is not.
> The only measure is ping time under maximum load of raw packets.

	Why raw packets? But yes I agree; I think “ping” in this discussion here is short hand for "latency measurement under load” which writes a bit unwieldy. The typical speed tests are almost there as they already perform (half of) the create maximum load requirement for the additional measurements we need (as well as already measuring unloaded latency, they all already report a “ping” number back, but that is best case RTT, so the baseline with which to compare the latency under load number (well obviously both numbers should be measured exactly the same)). Measuring latency under simultaneous saturation of both up- and downlink would be even better, but measuring it during simplex saturation should already give meaningful numbers.
	I think it would be great if speedtest sites could agree to measure and report such a number, so that end customers had data to base their ISP selection on (at least those fortunate few that actually have ISP choice…).

> And that requires a way to test maximum load rtt.
> There is no problem with that ... other than that to understand why and how that is relevant you have to understand Internet congestion control.  
> Having had to testify before CRTC about this, I learned that most access providers (the Canadian ones) claim that such measurements are never made as a measure of quality, and that you can calculate expected latency by using Little's lemma from average throughput. And that dropped packets are the right measure of quality of service.
> Ookla ping time  is useless in a context where even the "experts" wearing ties from the top grossing Internet firms are so confused. And maybe deliberately misleading on purpose... they had to be forced to provide any data they had about  congestion in their networks by a ruling during the proceeding and then responded that they had no data - they never measured queueing delay and disputed that it mattered. The proper measure of congestion was throughput.
> I kid you not.
> So Ookla ping time is useless against such public ignorance. 

	But, if people make their choice of (higher/ more expensive) service tiers dependent on its behavior at “capacity” as approximated by a speedtest latency under (full) load test that would make it much easier for ISPs to actually respond to it; even marketing can realize that this can be monetized ;)

Best Regards


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