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

[Jonathan Morton <chromatix99@gmail.com>]

On Sunday, 28 September 2025, David Lang 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)
> 
> 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?

So far as Cake is concerned, the normal setup should work fine even under stress conditions.  If there are too many simultaneous flows to achieve full flow isolation, it degrades gracefully to statistical multiplexing, and you still have the AQM working to keep everything responsive.  Or rather, a thousand AQMs working in parallel...

Of course, this only matters when Cake is set up to be the bottleneck.  If wifi is the bottleneck, you'll want a wifi stack with integrated fq_codel, which I believe still applies to only some hardware since it needs to manage the MAC queue which some devices don't expose.  This has the extra smarts needed to adapt gracefully to wifi's foibles, and might already be enough to convert an effectively nonfunctional wifi into one that feels, if not fast, then at least reliable.

 - Jonathan Morton