[Cake] diffserv3 vs diffserv4

[David P. Reed]

This idea (dividing the link rate capacity, since "bandwidth" is an incorrect term not to be promulgated), is absurd, but typical of "bellhead" thinking.
 
Per packet latency is the key control variable, even for TCP. That's because capacity/rate is not controllable by routers, but by routing in a general Internet situation.
 
Latency is controlled by queuing delay in a packet network, not bitrate. And in mixed traffic, which after all is why traffic is classified in the first place, by its characteristics and response to increased latency end-to-end, is the core "control" for the internetwork as a whole.
 
So, by promoting thinking about "bandwidth" a whole sequence of misformulations of network management is embedded into the thinking of those designing queue management algorithms.
 
And make no mistake, queue management is the ONLY knob other than sending different packets on different routes that one has for routers.
 
I don't know who proposed this fractional division, but it is clearly a bellhead-influenced thinker who thinks all protocols are CBR flows like in the old phone system.
 
But almost no flows in the internet are CBR flows! File transfers are not, streaming TV is not, web ttraffic is not, game traffic is not. Only non-statistically multiplexed real-time telephony and *some* video conferencing is CBR.
 
Yet this bizarre idea of dividing "bandwidth" among all categories of flows pops up. Probably from employees of phone companies or phone equipment suppliers. Or folks who went to Uni and were trained in "communications" by former phone engineers.
 
Latency, latency, latency. Queue delay, queue delay, queue delay. Not link speed! Change your brains.
 
It's hard fo fight this bellhead crowd (or the bellheadedness in your own thinking) but think about packets and queues instead.
 
My good friend Len Kleinrock didn't invent "Bandwidth Theory"! He invented Queueing Theory. For a reason.
 
On Saturday, July 25, 2020 6:12am, "Kevin Darbyshire-Bryant" <kevin at darbyshire-bryant.me.uk> said:



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> 
> > On 24 Jul 2020, at 18:42, Kevin Darbyshire-Bryant
> <kevin at darbyshire-bryant.me.uk> wrote:
> >
> >
> > The move from diffserv4 to diffserv5 WAS about de-prioritization.
> 
> It was also about minimum bandwidth allocations:
> 
> LE: 1/64th
> BK: 1/16th
> BE: 1/1
> VI: 1/2
> VO: 1/4
> 
> So worst case, best effort should get 11/64ths in the extreme case of all other
> tins in use.
> 
> Cheers,
> 
> Kevin D-B
> 
> gpg: 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A
> 
> 
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