However, inter-RD routing within an Administrative Domain is tightly coordinated and represents a unified technical plan. Inter-Administrative Domain routing is concerned with managing and controlling the flow of information in a highly structured way between organizations that may require formal multilateral agreements. Multiple agreements between multiple administrations are unlikely to be implicitly transitive. This makes the analysis of policy interactions very important. Each may have sufficiently global routing knowledge to determine a path to any Internet address.
Regional networks are clearly Administrative Domains.
Multilateral policy agreements are defined between the regional networks and the backbones. On the other hand, regional networks very often are tightly coupled to individual networks and campus networks in terms of routing. In this sense, a regional network could be viewed as a Routing Domain with individual campuses thought of as Subdomains. An AS as defined represents both a single IGP and a point of policy administration. The sixteen bit value now known as the Autonomous System number may instead be viewed as an Administrative Domain number.