The RPC protocol provides explicit support for versioning of a service. Client and server implementations of NFS version 3 protocol should support both versions, for full backwards compatibility, when possible. Default behavior of the RPC binding protocol is the client and server bind using the highest version number they both support. Client or server implementations that cannot easily support both versions (for example, because of memory restrictions) will have to choose what version to support. The NFS version 2 protocol would be a safe choice since fully capable clients and servers should support both versions. However, this choice would need to be made keeping all requirements in mind.