problems with RED element ?

[Brecht Vermeulen]

Hi,

I'm doing some tests with the red element today and I've noticed some
strange things :
test configuration : make-ip-conf script but with a RED element before
each queue (as push)
parameters of the RED element (5,20,0.1 as described in
http://www.aciri.org/floyd/REDparameters.txt)
queue length is 25.

The router has 4 interfaces and there are sent 2 streams, one from
eth1->eth2 and one from eth3->eth4 (eth0 is a fifth control interface).
These streams are gradually increasing in bandwidth: 10Mbit, 20, ...

Packet size is 256 bytes.

* first problem : if you look at next results, for the 90 Mbit and 100
Mbit case (so 180 and 200 Mbit/s in total) one stream has a very high
drop rate while the other one has a zero drop rate. All dropped packets
are dropped in the red elements (seen in the handlers). The queue itself
only drops about 30packets.


Packet	Bandwidth	Sent	Received Lost	Lost (%)
size	per flow	Packets

256	10.00000	45,289 	43,829 	1,460 	3.22374
256	10.00000	45,289 	45,024 	265 	0.58513
					

256	20.00000	90,579 	87,673 	2,906 	3.20825
256	20.00000	90,579 	90,091 	488 	0.53876
					

256	30.00000	135,869 	133,322 	2,547 	1.87460
256	30.00000	135,869 	135,869 	0 	0.00000
					

256	40.00000	181,159 	180,256 	903 	0.49846
256	40.00000	181,159 	181,159 	0 	0.00000
					

256	50.00000	226,449 	226,448 	1 	0.00044
256	50.00000	226,449 	226,449 	0 	0.00000
					

256	60.00000	271,739 	271,170 	569 	0.20939
256	60.00000	271,739 	271,463 	276 	0.10157
					

256	70.00000	317,028 	317,028 	0 	0.00000
256	70.00000	317,028 	317,028 	0 	0.00000
					

256	80.00000	362,318 	362,081 	237 	0.06541
256	80.00000	362,318 	362,081 	237 	0.06541
					

256	90.00000	407,608 	406,864 	744 	0.18253
256	90.00000	407,608 	138,361 	269,247 	66.05538
					

256	100.00000	452,898 	451,454 	1,444 	0.31884
256	100.00000	452,898 	0 	452,898 	100.00000

* 2nd problem, if I start a second test after this one : I get following
results :
so all packets of the 2nd stream are dropped ! while no packets of the
first one are dropped.

It seems as something isn't reset enough, because normally everything
(the queues are empty in between) should be zeroed. I had a little look
in the code but it was too difficult to see the solution at once, so
maybe the author of the red elements knows this immediately. The version
of the element is cvs 04th July but there are no changes in cvs.

256	10.00000	45,289 		45,289 		0 	0.00000
256	10.00000	45,289 		0 		45,289 	100.00000
					
256	20.00000	90,579 		90,579 		0 	0.00000
256	20.00000	90,579 		0 		90,579 	100.00000
					

256	30.00000	135,869 	135,869 	0 	0.00000
256	30.00000	135,869 	0 		135,869 	100.00000
					

256	40.00000	181,159 	181,159 	0 	0.00000
256	40.00000	181,159 	0 		181,159 	100.00000
					

256	50.00000	226,449 	226,449 	0 	0.00000
256	50.00000	226,449 	0 		226,449 	100.00000

* are there good values for the RED parameters and the queue lengths ?

thanks for any help
best regards,
Brecht