Re: Why are my cburst settings ignored?

[Andy Furniss <adf.lists@gmail.com>]

maillinglistredcap@gmx.de wrote:
> Hi there,
>
> I'm new to this list and new to traffic control as well. I want to do some traffic
> shaping on my home network and over the past few days I've studied the subject
> quite a lot. Today I decided to some first experiments on my network using the
> HTB queueing discpline which seems to suit my purposes best. Well the first
> results were disappointing... most likely due to my lack of knowledge. I tried
> to improve the result by tinkering with the burst and cburst parameters of HTB
> only to find that my cburst settings don't have any effect at all.
>
> parzival traffic # tc qdisc del dev eth0 root 2>/dev/null
> parzival traffic # tc qdisc add dev eth0 root handle 1: htb default 110
> parzival traffic # tc class add dev eth0 parent 1: classid 1:1 htb rate 100kbit
> burst 1650b cburst 1800b
> parzival traffic # tc -s class show dev eth0
> class htb 1:1 root prio 0 rate 100000bit ceil 100000bit burst 1650b cburst
> 1650b
>   Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
>   rate 0bit 0pps backlog 0b 0p requeues 0
>   lended: 0 borrowed: 0 giants: 0
>   tokens: 2062500 ctokens: 2250000

I don't know how it works exactly, but in this example as the rate and 
ceil are the same you get the same.

HTB seems to only allow certain values related to bandwidth of the 
rate/ceil and possibly r2q/quantum.

Testing your example with burst and cburst at 10b (as I once used this 
long ago) gives 10b and 10b, but changing ceil to 200kbit gives 10b and 20b.

I would only ever set low values on low bandwidth bulk classes.