Most firewalls don't allow TCP/IP communication, while some solutions like Iona's Wonderwall proxy allow IIOP to go through firewalls. To account for this, RMI comes with the ability to tunnel communication in HTTP by disguising communication as HTTP POSTs and REQUESTs. However, OMG's real firewall/IIOP effort is not to add IIOP support to firewalls which currently don't work with IIOP at all, but rather to add intelligent IIOP support to the firewall, including method level filtering and argument validation.