Hi there,
I'm using Linux (Debian), kernel version 2.4.17 on Pentium III
based PC and have a NIC 3com EtherLink 10/100 PCI (3c905b) on eth0
interface.
I've done some tests on CBQ. The class hierarchy was pretty simple
- I've created only one class (100kbit/s) except root class and it was
"bounded isolated". (Commands are shown at the end of this message.) I'
ve used an UDP traffic generator, which has been generating (in this
example) UDP packets with interpacket time of 20 miliseconds and sending
them from "host A" to "host B".
For all tests I did the number of generated packets was 5000. For
different packet sizes I got these results:
p_size (bytes) 10 50 100 200 300 400
g (kbit/s) 20,8 36,8 56,8 96,8 136,8 176,8
m (kbit/s) 20,7997 36,7995 56,7993 96,7987 105,2356 104,0127
num_of_rec_p 5000 5000 5000 5000 3947 3043
p_size (bytes) 500 800 1000
g (kbit/s) 216,8 336,8 416,8
m (kbit/s) 105,7655 103,6437 102,9431
num_of_rec_p 5000 5000 5000
p_size ... generated packet size
g ... bit-rate at which packets are sent to the interface ("host A"),
calculated from the following formula:
g=p_size+UDP header (bit)/generated_interpacket_time (s)
(generated_interpacket_time in shown example was 20 ms)
m ... packets are received at this rate ("host B"), calculated from the
following formula:
m=p_size+UDP header (bit)/measured_interpacket_time (s)
(measured_interpacket_time is average value of all received packets'
interpacket time)
num_of_rec_p ... number of received packets (on "host B")
-> My first problem is that I can't figure out why (for the packet size
greater than a 400 bytes) the packets that should be dropped go overlimit
and don't get dropped by qdisc or class?
For the packets smaller (or equal) than a 400 bytes this works normal.
-> The second one is: Why the class isn't limited exactly as I defined
(100 kbit/s)?
Hardware configuration was as follows:
["host A" eth0]------[ switch ]---------[eth0 "host B"]
192.168.19.203 192.168.19.204
CBQ definition in my example was: (the commands were started on "host A")
tc qdisc add dev eth0 root handle 1: cbq bandwidth 100Mbit avpkt 1000
tc class add dev eth0 parent 1:0 classid 1:10 cbq bandwidth 100Mbit rate
100kbit allot 1514 avpkt 1000 prio 5 bounded isolated
tc filter add dev eth0 parent 1: protocol ip prio 5 u32 match ip src
192.168.19.203/24 classid 1:10
Have I done anything wrong? Anyone has an idea? Please HELP ME.
I will be really greatful if anyone can solve this.
Thank You in advance!
Bruno
---------
Bruno Jurcic,
Faculty of Electrical Engineering and Computing, University of Zagreb
Department of Telecommunications
e-mail:bruno.jurcic@fer.hr (bj35492@pinus.cc.fer.hr)
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