1. Introduction

   RFC 1958 [RFC1958] describes the underlying principles of the
   Internet architecture.  This note extends that work by outlining some
   of the philosophical guidelines to which architects and designers of
   Internet backbone networks should adhere.  While many of the areas
   outlined in this document may be controversial, the unifying
   principle described here, controlling complexity as a mechanism to
   control costs and reliability, should not be.  Complexity in carrier
   networks can derive from many sources.  However, as stated in
   [DOYLE2002], "Complexity in most systems is driven by the need for
   robustness to uncertainty in their environments and component parts
   far more than by basic functionality".  The major thrust of this
   document, then, is to raise awareness about the complexity of some of
   our current architectures, and to examine the effect such complexity
   will almost certainly have on the IP carrier industry's ability to
   succeed.

   The rest of this document is organized as follows: The first section
   describes the Simplicity Principle and its implications for the
   design of very large systems.  The remainder of the document outlines
   the high-level consequences of the Simplicity Principle and how it
   should guide large scale network architecture and design approaches.