[Babel-users] [Make-wifi-fast] reducing delays in wifi mcast queues

[Jonathan Morton]

> On 19 Sep, 2018, at 3:43 am, Juliusz Chroboczek <jch at irif.fr> wrote:
> 
>>> Or perhaps, if we know which queue that is,
>>> we could modify Babel's packet scheduling to be more AQM friendly?
> 
>> How would you describe babel's packet schedulig now?
> 
> The main flaw is that it sends periodic updates as a burst of back-to-back
> full-size packets.  That could trigger Codel if you had more than 60
> routes or so.
> 
>> So dumping packets in there at a rate no more than 20ms each (short term
>> burst of 100ms) - relative to whatever bandwidth can be achieved vs the
>> other flows.
> 
> Right.  Guilty as charged.

The general principle you want is pacing, rather than bursting.  If you have a defined refresh interval, spread your routing updates evenly across that interval.  Or pick a rate to send updates at, and use ECN feedback to adjust that rate.

 - Jonathan Morton