[Cake] [Bloat] active sensing queue management

David Lang david at lang.hm
Thu Jun 11 21:44:42 EDT 2015

On Thu, 11 Jun 2015, Sebastian Moeller wrote:

> On Jun 11, 2015, at 03:05 , Alan Jenkins <alan.christopher.jenkins at gmail.com> wrote:
>> On 10/06/15 21:54, Sebastian Moeller wrote:
>> One solution would be if ISPs made sure upload is 100% provisioned. Could be 
>> cheaper than for (the higher rate) download.
> 	Not going to happen, in my opinion, as economically unfeasible for a 
> publicly traded ISP. I would settle for that approach as long as the ISP is 
> willing to fix its provisioning so that oversubscription episodes are 
> reasonable rare, though.

not going to happen on any network, publicly traded or not.

The question is not "can the theoretical max of all downstream devices exceed 
the upstream bandwidth" because that answer is going to be "yes" for every 
network built, LAN or WAN, but rather "does the demand in practice of the 
combined downstream devices exceed the upstream bandwidth for long enough to be 
a problem"

it's not even a matter of what percentage are they oversubscribed.

someone with 100 1.5Mb DSL lines downstream and a 50Mb upstream (30% of 
theoretical requirements) is probably a lot worse than someone with 100 1G lines 
downstream and a 10G upstream (10% of theoretical requirements) because it's far 
less likely that the users of the 1G lines are actually going to saturate them 
(let alone simultaniously for a noticable timeframe), while it's very likely 
that the users of the 1.5M DSL lines are going to saturate their lines for 
extended timeframes.

The problem shows up when either usage changes rapidly, or the network operator 
is not keeping up with required upgrades as gradual usage changes happen 
(including when they are prevented from upgrading because a peer won't 

As for the "100% provisioning" ideal, think through the theoretical aggregate 
and realize that before you get past very many layers, you get to a bandwidh 
requirement that it's not technically possible to provide.

David Lang

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