It's simple to implement bandwidth throttling in the WRE via mod_bw. This tutorial assumes that you have shell access to the server and appropriate privileges to install Apache modules.

This was tested on WRE 0.8.3.

1. Become a priveleged user and download the module source.
   wget http://bwmod.sourceforge.net/files/mod_bw-0.7.tgz
2. Switch to the WRE environment:
   . /data/wre/sbin/setenvironment.sh
3. Untar mod_bw. Run the following command to compile it:
   apxs -i -c mod_bw.c
   This installs the module in /data/wre/prereqs/modules
4. Configure mod_bw in /data/wre/etc/modproxy.conf. Here is a sample config to get you started:
   
   # Support bandwidth limiting
   AddType application/x-gzip gz
   AddType application/x-bzip2 bz2
   LoadModule bw_module modules/mod_bw.so
   BandWidthModule On
   AddOutputFilterByType MOD_BW application/zip application/x-gzip application/x-bzip2 application/x-tar
   AddOutputFilterByType MOD_BW video/mpeg video/msvideo video/quicktime application/x-iso9660-image
   LargeFilelimit * 512 32768
   
   This implements bandwidth throttling at 32KB only for the mime types declared above, and only if the file is larger than 512KB. Note that the first argument for LargeFilelimit is in KB, and the second is in bytes.
   
   Note also that we had to define a custom MIME type for gz and bz2 files because these were not in /etc/mime.types on our server. Look at your /etc/mime.types file to determine what types you need to add.
5. Restart modproxy and you should be set!
   /data/wre/sbin/wreservice.pl --restart modproxy

Troubleshooting

Error - undefined symbol: apr_atomic_cas

See http://4j.blogspot.com/2008/09/fix-for-modbw-when-getting-error.html