Routing in a Multi-provider Internet
RFC 1787

Document Type RFC - Informational (April 1995; No errata)
Last updated 2013-03-02
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Network Working Group                                         Y. Rekhter
Request for Comments: 1787        T.J. Watson Research Center, IBM Corp.
Category: Informational                                       April 1995

                  Routing in a Multi-provider Internet

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.


   This document was prepared by the author on behalf of the Internet
   Architecture Board (IAB). It is offered by the IAB to stimulate

   Over the past few years the Internet has undergone significant
   changes.  Among them is the emergence of multiple Network Service
   Providers, where resources that provide Internet-wide IP connectivity
   (routers, links) are controlled by different organizations.  This
   document presents some of the issues related to network layer routing
   in a multi-provider Internet, and specifically to the unicast

1. Network Service Providers vs Network Service Subscribers

   Within the current routing paradigm the service offered by a provider
   at the network layer (IP) is the set of destinations (hosts) that can
   be reached through the provider. Once a subscriber establishes direct
   connectivity to a provider, the subscriber can in principle reach all
   the destinations reachable through the provider. Since the value of
   the Internet-wide connectivity service offered by a provider
   increases with the number of destinations reachable through the
   provider, providers are motivated to interconnect with each other.

   In principle a provider need not offer the same service (in terms of
   the set of destinations) to all of its subscribers -- for some of the
   subscribers the provider may restrict the services to a subset of the
   destinations reachable through the provider. In fact, for certain
   types of subscribers constrained connectivity could be seen as part
   of the service offered by a provider.

   In a multi-provider environment individual providers may be driven by
   diverse and sometimes even conflicting goals and objectives. Some of
   the providers exist to provide connectivity to only a specific group

Rekhter                                                         [Page 1]
RFC 1787          Routing in a multi-provider Internet        April 1995

   of Network Service Subscribers. Other providers place no constraints
   on the subscribers that can subscribe to them, as long as the
   subscribers pay the fee charged by the providers. Some of the
   providers place certain constraints on the reselling of the
   connectivity services by organizations (e.g., other providers)
   attached to the providers. Some of the providers may be operated by
   companies that are subject to specific regulations (e.g.,  regulated
   monopoly), while other providers are completely unregulated.  The
   scope of geographical coverage among providers varies from a small
   region (e.g., county, town) to a country-wide, international, or even

   There is no centralized control over all the providers in the
   Internet.  The providers do not always coordinate their efforts with
   each other, and quite often are in competition with each other.

   Despite all the diversity among the providers, the Internet-wide IP
   connectivity is realized via Internet-wide distributed routing, which
   involves multiple providers, and thus implies certain degree of
   cooperation and coordination. Therefore, there is a need to balance
   the providers' goals and objectives against the public interest of
   Internet-wide connectivity and subscribers' choices. Further work is
   needed to understand how to reach the balance.

2. Routing Requirements

   Conceptually routing requirements can be classified into the
   following three categories: source preferences, destination
   preferences, and constraints on transit traffic. Source preferences
   allow an originator of a packet to exert control over the path to a
   destination.  Destination preferences allow a destination to exert
   control over the path from a source to the destination. Constraints
   on transit traffic allow a provider to control the traffic that can
   traverse through the resources (routers, links) controlled by the

   From a conceptual point of view the requirements over the degree of
   control for source and destination preferences may vary from being
   able to just provide connectivity (regardless of the path), to being
   able to select immediate providers, to more complex scenarios, where
   at the other extreme a subscriber may want to have complete control
   over the path selection.

   From a conceptual point of view the requirements over the degree of
   control for transit traffic may vary from control based only on the
   direct physical connectivity (controlling the set of organizations
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