RHEV 3.5 provides a new communcation mechanism between the engine and hosts using json-rpc

In Red Hat Enterprise Virtualization (RHEV) 3.5, newly-added hosts to a cluster in 3.5 compatibility mode will use json-rpc by default. This can be overriden and xml-rpc used instead, which was previously the only option.

Existing hosts will still use xml-rpc, but can be modified to use json-rpc. This requires that the host be placed into maintenance mode first.