[Cake] Getting Cake to work better with Steam and similar applications

[Andy Furniss]

Dendari Marini wrote:

>> What's your RTT(ping) to the different services, like Steam and 
>> Windows Update? Some ISPs have local CDNs that can give incredibly 
>> low latency relative to the provisioned bandwidth, which can cause 
>> bad things to happen with TCP.

> I tried Battle.net and Steam (manually starting a Windows Update is 
> rather difficult) and it seems Battle.net servers are closer
> compared to the Steam ones (and as I said I don't have the same
> issues with Battle.net).

Well it seems distance is important for BBR. It seems to have a design
whereby your rtt to the server determines how badly it will bork your
latency. Unlike cubic it doesn't take loss/ecn as a hint to get out of
its exponential phase, which is IMHO not a friendly thing to do, I mean
didn't they think people have to share connections :-(

Playing with a sim, something like dash that grabs a meg waits then gets
another with a new connection needs crazy amount of back off to avoid
borking latency every chunk. The amount of disruption getting worse the
higher the RTT of the TCP.

If you don't have a close CDN plus a low latency DSL gaming is not going
to be nice sharing with repeatedly starting up bbr.

With constant download muti-thread sims - like steam, there is sometimes
a case where every 10 seconds there will be a spike as bbr does probes.
This doesn't happen as much with staggered starts for the TCPs. It does
happen with single connections.

By default cake uses rtt parameter of 100ms - this seems to cause
excessive drops/marks causing upstream bandwidth issues on a connection
like yours. Increasing to say 300 reduces drops/marks but does make some
latency spikes a bit worse.

In summary BBR if you are not close to the server is a nightmare to
shape for latency on ingress. I am testing with 40ms rtt, which I don't
thing is excessive. Where I live, luckily youtube/steam are only 8ms and
things are a lot nicer when emulating that.