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EF and BE traffic--very strange behaviour !!
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
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
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
Any help/advice/explanation from you will be sincerely appreciated.
Thanks in advance.Please reply soon.
The script I used:---
$TC = "/usr/local/iproute2/tc/tc" ;
$DEV = "dev eth0";
print "$TC qdisc add $DEV handle 1:0 root dsmark indices 64
print "$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 $DEV parent 2:0 classid 2:2 cbq bandwidth ".
"10Mbit rate 4Mbit avpkt 1000 prio 7 bounded isolated allot 1514 weight
"maxburst 4 split 2:0 defmap 0xffff \n";
print "$TC qdisc add $DEV parent 2:2 red limit 4KB ".
"min 20kBit max 4KB burst 4 avpkt 1000 bandwidth 10Mbit ".
print "$TC filter add $DEV parent 2:0 protocol ip prio 2 ".
"handle 0 tcindex mask 0 classid 2:2 pass_on\n";
org:Network Programs ;Switching Excellence Centre
adr:;;B-1-C,Sector 10;NOIDA , GAUTAM BUDH NAGAR;;;INDIA
title:Member Technical Staff - (BBS-CAP)
fn:Aditya Chugh Amar