Use the lowest layer of RPC in the following situations:

• You need to use TCP. The intermediate layer uses UDP, which restricts RPC calls to 8K bytes of data. TCP permits calls to send long streams of data.

• You want to allocate and free memory while serializing or deserializing messages with XDR routines. No RPC call at the intermediate level explicitly permits freeing memory. XDR routines are used for memory allocation as well as for serializing and deserializing.

• You need to perform authentication on the client side or the server side by supplying credentials or verifying them.