[LARTC] limiting bandwidth on iface

[Marcus Fritzsch <marcus.fritzsch@gmx.net>]

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Hi there!

Well, as an exercise, I try 'simulating' an adsl link (just the speed ;o))
with a GRE tunnel and HTB for bandwidth limiting. Typically in germany
adsl has about 1024kbit downstream and 128kbits upstream (yes, there are
others ;) but these are what I have) - which are the values i try to simulate.

Here is the snipped that does the real thing on the client-side:

- -----snip-----
~     23 # now setup shaping to dsl-like-speed (up:128, down:1024 - this \
~        is the dsl-client)
~     24 $tc qdisc del dev $tun root >&- 2>&-
~     25 $tc qdisc add dev $tun root handle 1: htb
~     26
~     27 # shapiung class of root --> not more than 1mbit bandwidth
~     28 $tc class add dev $tun parent 1: classid 1:1 htb rate 1mbit \
~        burst 0 cburst 128
~     29
~     30 # this is for downstream
~     31 $tc class add dev $tun parent 1:1 classid 1:10 htb rate 1mbit
~     32 # this does upstream
~     33 $tc class add dev $tun parent 1:1 classid 1:20 htb rate \
~        128kbit burst 0 cburst 128
~     34
~     35 # add fairness queues for up- and downstream classes
~     36 $tc qdisc add dev $tun parent 1:10 handle 10: sfq perturb 5
~     37 $tc qdisc add dev $tun parent 1:20 handle 20: sfq perturb 5
~     38
~     39 # now take care of what is up- and what ist down-steam
~     40 U32="$tc filter add dev $tun protocol ip parent 1:0 prio 1 u32"
~     41 # everything that is from me is upstream
~     42 $U32 match ip src $tunip flowid 1:20
~     43 # everthing that comes to me is downstream
~     44 $U32 match ip dst $tunip flowid 1:10
- -----snap-----

eplanations:
$tunip is the ip of this end of the tunnel
$tc = tc

OK, I tryied this setup and noticed that approximately every 60 seconds,
the bandwidth gues up to about 256kbits for about 3 seconds - I have no
explanation for this - well, I do not really know what to set as parameter
for burst/cburst...

Any ideas, grave mistakes?



thanks a lot,

Marcus Fritzsch

- --
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Marcus Fritzsch <marcus.fritzsch@gmx.net>  ICQ:53118621  WWW:fritschy.de
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