Policy requirements for inter Administrative Domain routing
RFC 1125

Document Type RFC - Unknown (November 1989; No errata)
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Network Working Group                                          D. Estrin
Request for Comments:  1125              USC Computer Science Department
                                                           November 1989



   The purpose of this memo is to focus discussion on particular
   problems in the Internet and possible methods of solution.  No
   proposed solutions in this document are intended as standards for the
   Internet.  Rather, it is hoped that a general consensus will emerge
   as to the appropriate solution to such problems, leading eventually
   to the development and adoption of standards.  Distribution of this
   memo is unlimited.


   Efforts are now underway to develop a new generation of routing
   protocol that will allow each Administrative Domain (AD) in the
   growing Internet (and internets in general) to independently express
   and enforce policies regarding the flow of packets to, from, and
   through its resources. (FOOTNOTE 1: The material presented here
   incorporates discussions held with members of the IAB Autonomous
   Networks Research Group and the Open Routing Working Group.)  This
   document articulates the requirements for policy based routing and
   should be used as input to the functional specification and
   evaluation of proposed protocols.

   Two critical assumptions will shape the type of routing mechanism
   that is devised: (1) the topological organization of ADs, and (2) the
   type and variability of policies expressed by ADs.  After justifying
   our assumptions regarding AD topology we present a taxonomy, and
   specific examples, of policies that must be supported by a PR
   protocol.  We conclude with a brief discussion of policy routing
   mechanisms proposed in previous RFCs (827, 1102, 1104, 1105).  Future
   RFCs will elaborate on the architecture and protocols needed to
   support the requirements presented here.


   The Research Internet has evolved from a single backbone wide area
   network with many connected campus networks, to an internet with
   multiple cross-country backbones, regional access networks, and a
   profusion of campus networks. (FOOTNOTE 2: The term Research Internet
   refers to a collection of government, university, and some private
   company, networks that are used by researchers to access shared

Estrin                                                          [Page 1]
RFC 1125                  Policy Requirements              November 1989

   computing resources (e.g., supercomputers), and for research related
   information exchange (e.g., distribution of software, technical
   documents, and email). The networks that make up the Research
   Internet run the DOD Internet Protocol [1].)  At times during its
   development the Research Internet topology appeared somewhat chaotic.
   Overlapping facilities and lateral (as opposed to hierarchical)
   connections seemed to be the rule rather than the exception.  Today
   the Research Internet topology is becoming more regular through
   coordination of agency investment and adoption of a hierarchy similar
   to that of the telephone networks'.  The result is several
   overlapping wide area backbones connected to regional networks, which
   in turn connect to campus networks at universities, research
   laboratories, and private companies. However, the telephone network
   has lateral connections only at the highest level, i.e., between long
   haul carriers.  In the Research Internet there exist lateral
   connections at each level of the hierarchy, i.e., between campus (and
   regional) networks as well.

   Additional complexity is introduced in the Research Internet by
   virtue of connections to private networks. Many private companies are
   connected to the Research Internet for purposes of research or
   support activities. These private companies connect in the same
   manner as campuses, via a regional network or via lateral links to
   other campuses. However, many companies have their own private wide
   area networks which physically overlap with backbone and/or regional
   networks in the research internet, i.e., private vertical bypass

   Implicit in this complex topology are organizational boundaries.
   These boundaries define Administrative Domains (ADs) which preclude
   the imposition of a single, centralized set of policies on all
   resources.  The subject of this paper is the policy requirements for
   resource usage control in the Research Internet.

   In the remainder of this section we describe the policy routing
   problem in very general terms. Section 4 examines the constraints and
   requirements that makes the problem challenging, and leads us to
   conclude that a new generation of routing and resource control
   protocols are needed. Section 5 provides more detail on our
   assumptions as to the future topology and configuration of
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