[Cake] Re: help request for cake on a large network

[Sebastian Moeller <moeller0@gmx.de>]

Hi David,

while I have no real answer for your questions (due to never having had that kind of load in my home network ;) ) I would like to ask you to make take scripted captures of tc -s qdisc for the wan interface is reasonable short intervals (say every 10 minutes?) as that might be just what we need to actually answer your question.



> On 28. Sep 2025, at 13:06, David Lang <david@lang.hm> wrote:
> 
> I'm starting to prepare for the next Scale conference and we are switching from Juniper routers to Linux routers. This gives me the ability to implement cake.
> 
> One problem we have is classes that tell everyone 'go download this' that trigger hundreds of people to hammer the network at the same time (this is both a wifi and a network bandwidth issue, wifi is being worked on)

So one issue might be that with several 100 users the default compile-time size of queues (1024, IIRC) that cake will entertain might be too little, even in light of the 8 way assoziative hashing design. I believe this can be changed (within limits) only by modifying at source and recompilation of the kernel, if that should be needed at all.

I wonder whether multi-queue cake would not solve this to some degree, as I assume each queue's instance would bring its own independent set of 1024 bins?


> The network is pretty flat, a couple of subnets each on ipv4 and ipv6.
> 
> Any suggestions on how to configure cake for this sort of environment where there are so many devices?

Maybe switch to a simpler pure per-flow isolation mode than the default triple-isolate?

BTW what kind of uplink capacity will you use?

> 
> David Lang
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