Have a look at http://pic.dhe.ibm.com/infocenter/reqpro/v7r1m0/index.jsp?topic=/com.ibm.rational.reqpro.install_upgrade.doc/topics/w_http.html
IHS is mainly an Apache Httpd, ssl module is different, but you can use nearly all apache modules. Ihs is delivered with mod_proxy and can handle reverse proxy directives.
Regards
Christoph