On the other hand, DCOM defines cross-platform services (or abstractions) for object-oriented distributed computing, including connection to, and creation of, components, locating components, invoking methods on components, and a security framework.
Beyond this, DCOM simply uses the services available on each platform to implement multithreading and concurrency control, user interface, file system interaction, non-DCOM network interaction, and the actual security provider.
The DCOM wire-protocol is based on DCE RPC, so it is easy to implement DCOM on platforms for which DCE RPC is already available. DCE RPC defines a proven standard for converting in-memory data structures and parameters into network packets. Its Network Data Representation (NDR) is platform neutral ("reader makes right") and provides a rich set of portable data types.
COM and DCOM also borrow the notion of globally unique identifiers (GUIDs) from DCE RPC. GUIDs provide collision-free, unmanaged naming of objects and interfaces and are the basis of COM's robust versioning.
DCOM's pluggable security providers enable seamless integration with DCE-based security environments. Windows NT 4.0 can serve today as a gateway between platforms supporting ORPC-enhanced DCE RPC (DCOM) and platforms that provide only standard DCE RPC support. This is very useful for integrating existing DCE RPC-based applications on other platforms, and it provides a smooth migration path for multitier applications that can incrementally take advantage of DCOM features.