Autonomous confederations
RFC 975
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(February 1986; No errata)
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Network Working Group D. L. Mills
Request for Comments: 975 M/A-COM Linkabit
February 1986
Autonomous Confederations
Status of This Memo
This RFC proposes certain enhancements of the Exterior Gateway
Protocol (EGP) to support a simple, multiple-level routing capability
while preserving the robustness features of the current EGP model.
It requests discussion and suggestions for improvements.
Distribution of this memo is unlimited.
Overview
The enhancements, which do not require retrofits in existing
implementations in order to interoperate with enhanced
implementations, in effect generalize the concept of core system to
include multiple communities of autonomous systems, called autonomous
confederations. Autonomous confederations maintain a higher degree of
mutual trust than that assumed between autonomous systems in general,
including reasonable protection against routing loops between the
member systems, but allow the routing restrictions of the current EGP
model to be relaxed.
The enhancements involve the "hop count" or distance field of the EGP
Update message, the interpretation of which is not covered by the
current EGP model. This field is given a special interpretation
within each autonomous confederation to support up to three levels of
routing, one within the autonomous system, a second within the
autonomous confederation and an optional third within the universe of
confederations.
1. Introduction and Background
The historical development of Internet exterior-gateway routing
algorithms began with a rather rigid and restricted topological model
which emphasized robustness and stability at the expense of routing
dynamics and flexibility. Evolution of robust and dynamic routing
algorithms has since proved extraordinarily difficult, probably due
more to varying perceptions of service requirements than to
engineering problems.
The original exterior-gateway model suggested in RFC-827 [1] and
subsequently refined in RFC-888 [2] severely restricted the Internet
topology essentially to a tree structure with root represented by the
BBN-developed "core" gateway system. The most important
characteristic of the model was that debilitating resource-consuming
routing loops between clusters of gateways (called autonomous
Mills [Page 1]
RFC 975 February 1986
Autonomous Confederations
systems) could not occur in a tree-structured topology. However, the
administrative and enforcement difficulties involved, not to mention
the performance liabilities, made widespread implementation
impractical.
1.1. The Exterior Gateway Protocol
Requirements for near-term interoperability between the BBN core
gateways and the remainder of the gateway population implemented
by other organizations required that an interim protocol be
developed with the capability of exchanging reachability
information, but not necessarily the capability to function as a
true routing algorithm. This protocol is called the Exterior
Gateway Protocol (EGP) and is documented in RFC-904 [3].
EGP was not designed as a routing algorithm, since no agreement
could be reached on a trusted, common metric. However, EGP was
designed to provide high-quality reachability information, both
about neighbor gateways and about routes to non-neighbor gateways.
At the present state of development, dynamic routes are computed
only by the core system and provided to non-core gateways using
EGP only as an interface mechanism. Non-core gateways can provide
routes to the core system and even to other non-core gateways, but
cannot pass on "third-party" routes computed using data received
from other gateways.
As operational experience with EGP has accumulated, it has become
clear that a more decentralized dynamic routing capability is
needed in order to avoid resource-consuming suboptimal routes. In
addition, there has long been resistance to the a-priori
assumption of a single core system, with implications of
suboptimal performance, administrative problems, impossible
enforcement and possible subversion. Whether or not this
resistance is real or justified, the important technical question
remains whether a more dynamic, distributed approach is possible
without significantly diluting stability and robustness.
This document proposes certain enhancements of EGP which
generalize the concept of core system to include multiple
communities of autonomous systems, called autonomous
confederations. Autonomous confederations maintain a higher
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