On power-laws in SDH transport networks

It is has been previously demonstrated [4] that Internet topologies which were once considered unstructured networks with no global design processes actually follow powerlaws, both at the router level and the AS (Autonomous System) domain level. This discovery has very wide implications on network research as well as network and protocol design. The Internet is not the only network instance to exhibit power laws however; in this paper we present evidence for similar power laws also existing in transport layer topologies; in this case a real world deployed SDH (Synchronous Digital Hierarchy) network. The existence of such traits is unexpected as transport technologies are planned and engineered, in contrast to the rather looser planning and dynamic routing of the Internet. SDH networks are globally designed with multiple hierarchical levels and a specific structure, whereas the Internet is a growing collection of networks under independent control. Data is presented to demonstrate the conformance to power laws of the SDH network, the possible effects of the physical layer and the extent to which the topology remains scale-free throughout the network’s hierarchy. The possible sources of the traits are discussed and contrasted to those hypothesized for the Internet.