1. Introduction

   Computer networks form the infrastructure between the users they
   interconnect.  For example, the electronic mail service offered by
   computer networks provides a means for users to collaborate towards
   some common goal.  In the simplest cases, this collaboration may be
   solely for the dissemination of information.  In other cases, two
   users may work on a joint research project, using electronic mail as
   their primary means of communication.

   However, networks themselves are built on an underlying naming and
   numbering infrastructure, usually in the form of names and addresses.
   For example, some authority must exist to assign network addresses to
   ensure that numbering collisions do not occur.  This is of paramount
   importance for an environment which consists of multiple service
   providers.