The value of tmnxRadProxSrvCacheKeyAttrType specifies
the RADIUS attribute type to cache for this RADIUS Proxy server.
In order to generate the key associated with a RADIUS Access-Accept
or Accept-Request message, the system uses the attribute of the type
specified by the value of tmnxRadProxSrvCacheKeyAttrType,
within the associated RADIUS message of the type specified by the
value of tmnxRadProxSrvCacheKeyPktType.
The value zero means that no RADIUS attribute type is specified.