[Click] BandwidthShaper element not functioning as it should be

[Peter Dedecker]

Hi all,

I have a setup with 3 hosts connected like this:
purcell (eth1) <-> (eth2) mozart (eth1) <-> (eth2) kodaly

On Mozart, I have this very simple click configuration running with the 
latest click code (userlevel) from GIT today:
FromDevice(eth2, PROMISC 1) -> C1 :: Counter -> Q1 :: Queue(10) -> 
BandwidthShaper(250000) -> ToDevice(eth1);
FromDevice(eth1, PROMISC 1) -> C2 :: Counter -> Q2 :: Queue(10) -> 
BandwidthShaper(250000) -> ToDevice(eth2);

On Kodaly, I use Rude to send 1020 packets/s with a payload of 512 
B/packet during 3s, which should result in a stream of 4.5 Mbps.  As 
BandwidthShaper is configured to shape the incoming traffic to an 
outgoing flow of 2 Mbps, one should expect a loss rate of +/- 50 %, or 
at least a full queue after 20 ms.  However, when I run this simulation 
using a script that just starts the stream, waits 1s and prints out the 
appropriate element handlers, I get following results:
$ sh clicktest.sh 10
run 1: 0 packets dropped out of 1607 = 0 % packet loss
run 2: 0 packets dropped out of 2001 = 0 % packet loss
run 3: 0 packets dropped out of 1995 = 0 % packet loss
run 4: 0 packets dropped out of 1995 = 0 % packet loss
run 5: 0 packets dropped out of 1996 = 0 % packet loss
run 6: 0 packets dropped out of 1543 = 0 % packet loss
run 7: 0 packets dropped out of 1997 = 0 % packet loss
run 8: 0 packets dropped out of 1995 = 0 % packet loss
run 9: 0 packets dropped out of 1990 = 0 % packet loss
run 10: 0 packets dropped out of 2001 = 0 % packet loss

Highwaterlevel_length at each queue returns just 1, which seems very 
strange to me.

When I check on Mozart all incoming and outgoing packets with tcpdump, 
the packets arriving from Kodaly correctly are correct: 3062 packets at 
+/- 4.5 Mbps constantly.  However, a tcpdump on the outgoing interface 
tells me 1872 packets are sent out:
- from 0 to 0.6 s at +/- 4.5 Mbps
- from 0.6 s to 3.3 s at +/- 2 Mbps

Weird, doesn't it?

FWIW: all 3 machines are identical and run Fedora Core 9 with kernel 
2.6.25.14-108.fc9.i686.  The used network cards are Realtek 
Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10).

Does anyone have an idea about what't wrong here?  Thanks a lot!

Kind Regards,

Peter


-- 
ir. Peter Dedecker
IBCN Research Group
Department of Information Technology (INTEC)
Ghent University - IBBT
Gaston Crommenlaan 8 bus 201, B-9050 Gent
Tel: +32(0)9 3314977, Fax: +32(0)9 2649969
Peter.Dedecker at intec.UGent.be