The following is copied from the BBR paper: https://queue.acm.org/detail.cfm?id=3022184
"The rate balance condition alone does not ensure there is no queue, only that it can’t change size(e.g., if a connection starts by sending its 10-packet Initial Window into a five-packet BDP, then runs at exactly the bottleneck rate, five of the 10 initial packets fill the pipe so the excess forms a standing queue at the bottleneck that cannot dissipate). Similarly, the full pipe condition does not guarantee there is no queue (e.g., a connection sending a BDP in BDP/2 bursts gets full bottleneck utilization, but with an average queue of BDP/4)."
there are few points confused me:
1、”rate balance condition means packet arrival rate equals BtlBw“：so why only rate balance but full pipe can't ensure no queue? how rate balance only produce bytes larger than full pipe?
2、”only that it can't change size“：what does the ”size“ mean？
3、why there is BDP/4 queued?
