Mod Bandwidth:

Used to limit bandwidth utilization of your normal and virtual hosts .

Home Page:
System /. OS : CentOS 5

You will need httpd-devel should be installed.

cd ~
tar xzf mod_bw-0.8.tgz
cd mod_bw

apxs -i -a -c mod_bw.c

chmod 755 /usr/lib/httpd/modules/

[activating module `bw’ in /etc/httpd/conf/httpd.conf]

You should be able to see the LoadModule command in your httpd.conf . You can restart apache at this time.

#grep bw /etc/httpd/conf/httpd.conf

LoadModule bw_module /usr/lib/httpd/modules/

service httpd restart

In your Virtual Host section:-

I want to restrict all downloads of files larger than 500kb, to a speed of 50kb/s.

< VirtualHost *:80 >
BandwidthModule On
ForceBandWidthModule On

#Unlimited Bandwidth for all (except for large files, see below):-  
BandWidth all 0  
#No one should be able to open more than 5 simultaneous connections at one time :-  
MaxConnection all 5  
#Limit files greater than 500kb to 50kb/s :-  
LargeFileLimit * 500 50000

DocumentRoot /var/www/vhosts/  

Time to restart Apache web service.

service httpd restart

Alhumdulillah. Done.