RFC 1136 (rfc1136) - Page 3 of 10

Administrative Domains and Routing Domains: A model for routing in the Internet

RFC 1136          A Model for Routing in the Internet      December 1989


      Network Service Access Point (NSAP)

         A conceptual point on the Network/Transport Layer boundary in
         an End System that is globally addressable (and the address
         globally unambiguous) in the OSIE.  An NSAP represents a
         service available above the Network Layer (such as a choice of
         transport protocols).  An End System may have multiple NSAPs.
         An NSAP address is roughly equivalent to the Internet [address,
         protocol] pair.

      Administrative Domain (AD)

         "A collection of End Systems, Intermediate Systems, and
         subnetworks operated by a single organization or administrative
         authority.  The components which make up the domain are assumed
         to interoperate with a significant degree of mutual trust among
         themselves, but interoperate with other Administrative Domains
         in a mutually suspicious manner" [1].

         A group of hosts, routers, and networks operated and managed by
         a single organization.  Routing within an Administrative Domain
         is based on a consistent technical plan.  An Administrative
         Domain is viewed from the outside, for purposes of routing, as
         a cohesive entity, of which the internal structure is
         unimportant.  Information passed by other Administrative
         Domains is trusted less than information from one's own
         Administrative Domain.

         Administrative Domains can be organized into a loose hierarchy
         that reflects the availability and authoritativeness of routing
         information.  This hierarchy does not imply administrative
         containment, nor does it imply a strict tree topology.

      Routing Domain (RD)

         "A set of End Systems and Intermediate Systems which operate
         according to the same routeing procedures and which is wholly
         contained within a single Administrative Domain" [1].

         "A Routeing Domain is a set of ISs and ESs bound by a common
         routeing procedure; namely:

         they are using the same set of routeing metrics,

         they use compatible metric measurement techniques,

         they use the same information distribution protocol, and




Hares & Katz