> On 14 Jan, 2019, at 6:17 pm, Rodrigo Alvarez Dominguez <[email protected]>
> wrote:
>
> Hi Jonathan
> Thanks for your quick answer. REally appreciate it!!!
> I wil try later the cake statement (is it the same as codel)?. I am starting
> with Codel. So I need to have a better understanding of codel.
Cake is a more advanced implementation of the same principles. Its shaper is
more accurate than HTB, and it's easier to configure correctly than the
component qdiscs and filters you're currently using.
> Where client asks for a FTP file to server. Link between router-server has a
> 150MBit speed with a delay of 250 ms.
> Then link between client and router has 10 Mbit and the Codel algorithm. So I
> am checking the differences between having codel or not.
> Do you have an advice to have a good scenario for testing Codel properly? Or
> a document to know how the differences parameter can affect to the
> communication?
> In my scenario it seems it is better not having Codel. See attached
> ClientFTPCodelNO-NO-NO (nocodel) versus ClientFtpCodel1000..
> where a Codel Algorithm of 1000 packets, 13 ms target and 100 interval is
> configured
First, and most importantly, you're measuring only throughput, while ignoring
latency. The primary benefit of any 'smart queue" is in reducing latency,
preferably with the least practical impact on throughput. Dumb FIFOs often
induce latencies of several seconds when loaded. The improvement is visible to
the user as quicker response and better reliability of operation while the link
is busy. Here's a better test to try out:
http://www.dslreports.com/speedtest
Second, your Codel parameters are too tight for the relatively long-latency
path you're measuring. You should set "interval" to your expected path latency
(250ms) and "target" to about a tenth of that (25ms). I would also advise
against "noecn" and replace it with "ecn"; this will safely have no effect if
you don't have ECN-enabled traffic, but reduces packet loss if you do.
Cake has an "rtt" parameter so you don't have to manually select a target and
interval, and it unconditionally supports ECN. Updating my earlier suggestion:
tc qdisc replace dev r1-eth0 root handle 1: cake bandwidth 10000kbit
besteffort flows rtt 250ms
Third, you should turn on ECN on your end-hosts if you can. Most servers will
respond with ECN traffic if requested, so search for instructions for enabling
ECN on your own machine.
- Jonathan Morton
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