| Comparing types of network design |
In the early 1960s, as an introduction to a series of memoranda entitled “On Distributed Communications,” Baran made the case for shifting existing communication systems from analog-based, hierarchically organized networks to an innovative, digital, distributed type of network. He maintained that the greater connectivity and localized control of a distributed network would increase its ability to survive and adapt to various changes throughout the system. Based on his ideas, the centralized “command and control” network configuration used in previous communications systems was replaced by the distributed “hot-potato routing” version that would eventually become the basis of the World Wide Web. Baran’s work also suggests some of structural and functional differences among these three types of organizational systems.
The centralized network is obviously vulnerable as destruction of a single central node destroys communication between the end stations. In practice, a mixture of star and mesh components is used to form communication networks. For example, type (b) in Fig. 1 shows the hierarchical structure of a set of stars connected in the form of a larger star with an additional link forming a loop. Such a network is sometimes called a “decentralized” network, because complete reliance upon a single point is not always required…
Since the destruction of a small number of nodes in a decentralized network can destroy communications, the properties, problems, and hopes of building “distributed” communications networks are of paramount interest…. [E]xtremely survivable networks can be built using a moderately low redundancy of connectivity level.
The use of a standard format message block [packet] permits building relatively simple switching mechanism using an adaptive store-and-forward routing policy to handle all forms of digital data… Simulation results are shown to indicate that highly efficient routing can be performed by local control without the necessity for any central–and therefore vulnerable–control point.
On distributed communications: Introduction to distributed communications networks | Paul Baran
Paul Baran and the origins of the internet | RAND Corporation