cake: changing bandwidth on the rate limiter dynamically

[Dave Taht]

One of the nice things that the gargoyle-qos system does is that it
attempts to measure the bandwidth actively and modify the actual
bandwidth in the rate limiter to suit.

It does this with some very hairy code into the htb/hfsc subsystem,
and measuring ping to either a server elsewhere or short ttl udp +
icmp returns.... (can't remember which)

dealing with the measurements correctly when traffic is possibly
bottlenecking in both directions I think it fails on. As does
streamboost.

Now, it turns out that cake makes altering the bandwidth really easy,
you can just change it from the command line.

http://pastebin.com/Jr9s6EBW

I am pretty sure changing it is currently pretty damaging to stuff in
flight (don't remember), but
it needent be.

I think dynamically sensing the underlying bandwidth would be a great
boon, rather than having to set it so explicitly, and perhaps by
sensing some other parameters like ack clocks or overall traffic flow
at a depth that bpf could resolve, might be a valid approach.


-- 
Dave Täht

http://www.bufferbloat.net/projects/bloat/wiki/Upcoming_Talks