their computers interconnect. And SO in 1978, the International Organization for Standardization (ISO) began an incredibly ambitious project. Open Systems Interconnection (OSI) promised to be all things to all people. And that was its downfall. It tried to be both SNA and DECnet, both X.25 and the ARPAnet, both meat and potatoes, and instead became a mish-mash of con- fusing options. The most famous part of OSI is, no doubt, its Reference Model (the OSIRM). Defined early on, OSI's famous seven-layer model became the stan- dard method of describing computer networks. Essentially every other protocol suite has been characterized in terms of the OSIRM. One might imagine, then, that the OSIRM had been well researched before it was adopted. But the truth is a bit more prosaic. The layered model was primarily created to divide the work among various subcommittees. Memorialized in the organizational structure of huge international effort, the OSIRM was left intact long after it turned out to be, in part, unworkable! Not that the OSIRM was entirely useless. It did a good job of characteriz- ing packet-switched networks at the lower layers. Layer 1, the physical layer, transports bits. Layer 2, the data link layer, groups them into blocks called frames and provides for error detection. Together, these two layers generally operate on a hop-by-hop basis. Layer 3, the network layer, transports packets The Internet Boom and the Limits to Growth from one end of the network to the other and is the primary domain of interme- diate systems, which today are usually called routers. Although the Internet Pro- tocol itself is clearly a Layer 3 protocol, OSI's Layer 3 early on ran into an impasse in committee. One faction, largely interested in efficient terminal-to- host connectivity, wanted a connection-oriented Layer 3. It demanded, and got, a standard based on X.25. Another faction, more interested in host-to-host con- nectivity, wanted a connectionless Layer 3. It demanded, and got, one too. The ISO Connectionless Network Protoco