[Cerowrt-devel] BBR congestion control algorithm for TCP in net-next

Mikael Abrahamsson swmike at swm.pp.se
Wed Sep 21 07:28:39 EDT 2016

On Wed, 21 Sep 2016, Alan Jenkins wrote:

> That assumes the measured maximum bandwidth (over an interval of 10*rtt) 
> remains constant.  (Say there were 100 BBR flows, then you added one 
> CUBIC flow to bloat the buffer).  I don't have a good intuition for how 
> the bandwidth estimation behaves in general.

My example was single CUBIC flow already existing, steady state, full 
speed, filling pipe and buffer with 100ms of packets, and it's not filling 
buffer to 110ms of packets because its window is full. There is no packet 
loss currently.

Now you add single BBR flow. What happens, what's the ratio between BBR 
and CUBIC after 20 seconds of letting things settle down to new 

Consider the FIFO buffer practically infinite, or at least able to buffer 
5 seconds of packets without drop. It's an interface with a single, 
stupid, huge FIFO buffer.

Mikael Abrahamsson    email: swmike at swm.pp.se

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