For example, sharing information in a network with UNIX workstations, PCs, and Macs would be impossible if each vendor invented their own methods for connecting, sending, and receiving data. Instead, IP, IPX, and Appletalk, as different as they are, all arrange information in data packets in a way that can be interpreted by each other so that they can coexist in a single network.
The Open Systems Interconnection (OSI) model is a standard that was created by the International Organization for Standardization (ISO). It defines a layered reference model for an environment in which a process running in one computer can communicate with a similar process in another computer if they implement the same OSI layer communication protocols (illustrated above).
Protocols are defined by a standards organizations. Standards cover how computer equipment and data transmission operates. Standards are actually recommendations that enable multiple vendors to supply the demand for internetworking hardware and software.
In order for innovations in technology to be adopted, vendors describe their technology in a form called a Request for Comments (RFC). Many protocols refer to an RFC number, giving the public access to information about how a device or service is designed to work.
RFCs are published, among other places, on the World Wide Web. For example, if you want to learn more about the Ascend Multilink Protocol Plus (commonly referred to as MP+), you can go to a site on the Web with an index of RFCs, such as http://www.internic.net/ and search for MP+, or RFC 1934, which is the RFC number for this protocol.
Not all protocols are defined by RFCs and not all popular protocols are the best technologically - they became standards because they were the first to emerge with a solution that was in demand.