RFC 2071 (rfc2071) - Page 2 of 14

Network Renumbering Overview: Why would I want it and what is it anyway?

RFC 2071              Network Renumbering Overview          January 1997


1. Introduction

   The popularity of connecting to the global Internet over the course
   of the past several years has spawned new problems; what most people
   casually refer to as "growing pains" can be attributed to more basic
   problems in understanding the requirements for Internet connectivity.
   However, the reasons why organizations may need to renumber their
   networks can greatly vary. We'll discuss these issues in some amount
   of detail below.  It is not within the intended scope of this
   document to discuss renumbering methodologies, techniques, or tools.

2. Background

   The ability for any network or interconnected devices, such as
   desktop PCs or workstations, to obtain connectivity to any potential
   destination in the global Internet is reliant upon the possession of
   unique IP host addresses [1].  A duplicate host address that is being
   used elsewhere in the Internet could best be described as
   problematic, since the presence of duplicate addresses would cause
   one of the destinations to be unreachable from some origins in the
   Internet.  It should be noted, however, that globally unique IP
   addresses are not always necessary, and is dependent on the
   connectivity requirements [2].

   However, the recent popularity in obtaining Internet connectivity has
   made these types of connectivity dependencies unpredictable, and
   conventional wisdom in the Internet community dictates that the
   various address allocation registries, such as the InterNIC, as well
   as the ISP's, become more prudent in their address allocation
   strategies.  In that vein, the InterNIC has defined address
   allocation policies [3] wherein the majority of address allocations
   for end-user networks are accommodated by their upstream ISP, except
   in cases where dual- or multihoming and very large blocks of
   addresses are required.  With this allocation policy becoming
   standard current practice, it presents unique problems regarding the
   portability of addresses from one provider to another.

   As a practical matter, end users cannot assume they "own" address
   allocations, if their intention is to be to have full connectivity to
   the global Internet. Rather, end users will "borrow" part of the
   address space of an upstream provider's allocation. The larger
   provider block from which their space is suballocated will have been
   assigned in a manner consistent with global Internet routing.

   Not having "permanent" addresses does not mean users will not have
   unique identifiers. Such identifiers are typically Domain Name System
   (DNS) [4] names for endpoints such as servers and workstations.
   Mechanisms such as the Dynamic Host Configuration Protocol (DHCP) [5]



Ferguson & Berkowitz         Informational