You install SAP Web Dispatcher as the reverse proxy.
SAP recommends using SAP Web Dispatcher 7.4 as the reverse proxy. If you use any other reverse proxy, see the manufacturer’s documentation for more information.
For SAP Web Dispatcher for SAP NetWeaver 7.31, see http://help.sap.com/nw731 .
For SAP Web Dispatcher for SAP NetWeaver 7.40, see http://help.sap.com/nw74 .