There are two versions of RPPs , you can see their banners at the web server errors log after a start up, e.g.
older one banner in errors logs when start up web server :
[18/Dec/2007:11:35:54] info (22836): PASS1000: Sun ONE Web Server 6.1SP3 Reverse Proxy Plugin B09/09/2004 11:59
newer RPP banner :
[15/Feb/2008:15:48:43] info (10935): PASS1000: Sun ONE Web Server 6.1SP7 Reverse Proxy Plugin B01/11/2007 23:21
You can see their docs at below:
The Reverse Proxy Plug-in is a NSAPI plug-in designed for use with the Sun Java System Web Server 6.1 SP8 and later Service packs. "
older 6.1SP3 RPP,
The Reverse Proxy Plugin is a NSAPI plugin designed for use with the Sun Java System Web Server 6.1 SP3 and later Service Packs.
Please use the suggested Sun Java System Web Server versions as noted in the above docs.