A Model for Content Internetworking (CDI)
RFC 3466

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Network Working Group                                             M. Day
Request for Comments: 3466                                         Cisco
Category: Informational                                          B. Cain
                                                                Storigen
                                                            G. Tomlinson
                                                         Tomlinson Group
                                                              P. Rzewski
                                                   Media Publisher, Inc.
                                                           February 2003

               A Model for Content Internetworking (CDI)

Status of this Memo

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

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   Content (distribution) internetworking (CDI) is the technology for
   interconnecting content networks, sometimes previously called
   "content peering" or "CDN peering".  A common vocabulary helps the
   process of discussing such interconnection and interoperation.  This
   document introduces content networks and content internetworking, and
   defines elements for such a common vocabulary.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Content Networks . . . . . . . . . . . . . . . . . . . . . .  2
       2.1   Problem Description  . . . . . . . . . . . . . . . . .  3
       2.2   Caching Proxies. . . . . . . . . . . . . . . . . . . .  4
       2.3   Server Farms . . . . . . . . . . . . . . . . . . . . .  5
       2.4   Content Distribution Networks. . . . . . . . . . . . .  6
             2.4.1 Historic Evolution of CDNs . . . . . . . . . . .  8
             2.4.2 Describing CDN Value: Scale and Reach. . . . . .  8
   3.  Content Network Model Terms  . . . . . . . . . . . . . . . .  9
   4.  Content Internetworking  . . . . . . . . . . . . . . . . . . 12
   5.  Content Internetworking Model Terms  . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . 15
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
   8.  Normative References . . . . . . . . . . . . . . . . . . . . 16

Day, et al.                  Informational                      [Page 1]
RFC 3466       A Model for Content Internetworking (CDI)   February 2003

   9.  Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16
   10. Full Copyright Statement . . . . . . . . . . . . . . . . . . 17

1. Introduction

   Content networks are of increasing importance to the overall
   architecture of the Web.  This document presents a vocabulary for use
   in developing technology for interconnecting content networks, or
   "content internetworking".

   The accepted name for the technology of interconnecting content
   networks is "content internetworking".  For historical reasons, we
   abbreviate this term using the acronym CDI (from "content
   distribution internetworking").  Earlier names relied on analogy with
   peering and interconnection of IP networks; thus we had "content
   peering" and "CDN peering".  All of these other names are now
   deprecated, and we have worked to establish consistent usage of
   "content internetworking" and "CDI" throughout the documents of the
   IETF CDI group.

   The terminology in this document builds from the previous taxonomy of
   web caching and replication in RFC 3040 [3].  In particular, we have
   attempted to avoid the use of the common terms "proxies" or "caches"
   in favor of more specific terms defined by that document, such as
   "caching proxy".

   Section 2 provides background on content networks.  Section 3
   introduces the terms used for elements of a content network and
   explains how those terms are used.  Section 4 provides additional
   background on interconnecting content networks, following which
   Section 5 introduces additional terms and explains how those
   internetworking terms are used.

2. Content Networks

   The past several years have seen the evolution of technologies
   centered around "content".  Protocols, appliances, and entire markets
   have been created exclusively for the location, download, and usage
   tracking of content.  Some sample technologies in this area have
   included web caching proxies, content management tools, intelligent
   "web switches", and advanced log analysis tools.

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RFC 3466       A Model for Content Internetworking (CDI)   February 2003

   When used together, these tools form new types of networks, dubbed
   "content networks".  Whereas network infrastructures have
   traditionally processed information at layers 1 through 3 of the OSI
   stack, content networks include network infrastructure that exists in