e of greater overhead. Both factions wanted the cell pay- load size to be a power of two. An eventual compromise was reached; before the 1988 Blue Book gave the first outline of B-ISDN, the ATM payload size became 48 octets, for a 53-octet total cell. Divestiture: Equal Access and Chinese Walls The B-ISDN program was initially dominated by telecommunications carriers that were looking for a standard for fiber-optic networks that could compete with cable television. While cable networks theoretically could com- pete with telephone companies, in the 1980s the threat was indeed little more than theoretical. But it seemed like the best defense was a good offense, however slowly it was expected to happen. As a telecom-industry project, B-ISDN was defined to work in the wide area, eventually expected to become a worldwide network, but it also had the bandwidth to be competitive in the local area. So ATM LANs were very much a possibility, with a PBX-like topology. But as the 1990s began, manufacturers had other ideas. The first practical implementations of B-ISDN were not "carrier-grade" equipment but enterprise- grade LAN switches. And they did not use SONET. The first such switch was marketed by Fore Systems, a Pittsburgh start-up (later acquired by Marconi); it used 100-Mbps fiber- optic interfaces. Other companies jumped into the fray, and the ATM Forum began as a new standards body independent of the ITU-T. In 1991 and 1992, ATM-the B-ISDN name was seen as marketing poison and largely forgotten outside of the ITU-became a major draw for venture capital. Dozens of companies produced ATM switches, ATM chips, and ATM network interface cards for PCs. The ATM Forum had a huge controversy over a stan- dard for twisted-pair ATM for the desktop, leading to an IBM-led spin-off to promote a 25-Mbps standard that competed with the ATM Forum's 50-Mbps rate. ATM was seen, for a time, as the future of networking. Except that it always lacked one important thing-customers. ATM's appeal to the LAN was that it was faster than 10-Mb