total download rate with many flows

George Amanakis g_amanakis at
Tue Oct 31 18:37:33 EDT 2017

Dear List,

I am observing a strange behavior when one host in the LAN downloads 
from a couple of other hosts in WAN, but with many flows.
To give you an example:
Line is Comcast residential cable, advertised as 10000Mbps/2Mbps.
LAN-Host A is updating Windows 10, and generates many flows. It is the 
only device active on LAN and achieves a download rate of ~7.7Mbps. The 
set limit is ~11.7Mbps and it can be achieved from this host, as long as 
the number of parallel flows remains <4. If the number of flows 
increases, the actual download rate drops. Apart from this, cake is 
doing a great job: even with Host A updating Windows 10 other LAN-hosts 
can ping WAN-hosts with a latency <100ms and the traffic is very 
responsive. I am going to try to replicate this behavior using flent.

Is there a way to ameliorate this without hurting latency for the other 

ens4 is LAN interface
ens3 is WAN interface
qdisc cake 8001: dev ens4 root refcnt 2 bandwidth 12200Kbit besteffort 
dual-dsthost wash ingress rtt 100.0ms noatm overhead 18 via-ethernet mpu 64
qdisc cake 8002: dev ens3 root refcnt 2 bandwidth 2500Kbit besteffort 
dual-srchost nat wash rtt 100.0ms noatm overhead 18 via-ethernet mpu 64


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