512 Part 5 The PMS level Section 4 Network computers and computer networks
for a local computer and local network cases, respectively. The C('IMP) is a C('Honeywell 516; 16 b/w; 12 ~16 kw; 1 m s/w) with capability to connect to four to six links at a 50-kb/s data rate.
The ARPA network leases a set of fixed links, L(50 kb/s). These emanate from four S.fixed, as shown in Fig. 7d. Thus the fixed links between the various sites, as shown in Fig. 7a, are composed of the links in Fig. 7d. For example, the L(Carnegie-Mellon University; Bolt Beranak and Newman) goes from Carnegie-Mellon University in Pittsburgh, Pa., to Williamstown, Ky., to Littleton, Mass. (on one of the two links) to Bolt Beranak and Newman in Boston, Mass. The other L(Littleton; Williamstown) is part of L(University of Michigan; Lincoln Laboratory). With such a fixed-link system the network must operate in a store-and-forward fashion, with C('IMP)'s at each site carrying out this function. Thus the C('IMP) is required at each site, since there is no uniformity in the other C's that are at a site and no control over their operation.
Conclusions
We feel the network is the most important computer structure in the book. Through understanding it, we will be able to organize more computing power than with any other structure and to achieve more reliability. The issues of switches and links are so vital that through understanding of them all computer structures will improve.
References
BhusA67; DaviD67; EverR57; PlugW6l; RobeL67; SegaR61; IBM System/360 Attached Support Processor (ASP) System Description, H20-0223-0