EF and BE traffic--very strange behaviour !!

[Aditya Chugh <aditya@npi.stpn.soft.net>]

Hello Werner and friends,

I am using my modified version of TTCP (with which I can set the TOS
byte of my packets ) to test the throuput and the time taken to traverse

the path from A to B.
A and B are both linux machines  connected to the same local LAN. The
kernel of A
is diffserv enabled,while B has plain vanilla Linux.
I run a modified version of "EFCBQ" - the standard script to set the
diffserv queues for EF and BE.
I assign both EF and BE  4 Mbit of rate ( out of total b/w of 10Mbit ) I

make both the queues "bounded and isolated" ...so they can neither
borrow nor lend b/w. The weight assigned to each is 1.  (Script attached

below)

When I send both EF and BE packets simultaneously from A to B , I get EF

b/w about 467 Kb/sec
and BE bandwidth about 340Kb/sec---which is OK according to me.
When I send only EF packets from A to B the b/w is reduced to around 260

Kb/sec
When I send only BE packets the b/w I get is around 336 Kb/sec ?
These results are getting repeated consistently. (measurements have been

taken 8-10 times for each case)
Isn't this strange ??  How do we explain it ?
I am totally stumped ....and  am unable to come up with a coherent
explanation

Any help/advice/explanation from you will be sincerely appreciated.
Thanks in advance.Please reply soon.
regards,
Aditya





The script I used:---

#!/usr/bin/perl
#
$TC = "/usr/local/iproute2/tc/tc" ;
$DEV = "dev eth0";
print "$TC qdisc add $DEV handle 1:0 root dsmark indices 64
set_tc_index\n";
print "$TC filter add $DEV parent 1:0 protocol ip prio 1 tcindex ".
  "mask 0xfc shift 2\n";
print "$TC qdisc add $DEV parent 1:0 handle 2:0 cbq bandwidth ".
 "10Mbit cell 8 avpkt 1000 mpu 64\n";
#
# EF class
#
print "$TC class add $DEV parent 2:0 classid 2:1 cbq bandwidth ".
 "10Mbit rate 4Mbit avpkt 1000 prio 1 bounded isolated ".
 "allot 1514 weight 1 maxburst 4 \n";
# packet fifo for EF?
print "$TC qdisc add $DEV parent 2:1 pfifo limit 4\n";
print "$TC filter add $DEV parent 2:0 protocol ip prio 1 ".
   "handle 0x2e tcindex classid 2:1 pass_on\n";
#
# BE class
#
print "#BE class(2:2) \n";
print "$TC class add $DEV parent 2:0 classid 2:2 cbq bandwidth ".
 "10Mbit rate 4Mbit avpkt 1000 prio 7 bounded isolated allot 1514 weight

1 ".
 "maxburst 4  split 2:0 defmap 0xffff \n";
print "$TC qdisc add $DEV parent 2:2 red limit 4KB ".
   "min 20kBit max 4KB burst 4 avpkt 1000 bandwidth 10Mbit ".
   "probability 0.02\n";
print "$TC filter add $DEV parent 2:0 protocol ip prio 2 ".
   "handle 0 tcindex mask 0 classid 2:2 pass_on\n";










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