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Versions: 00 01                                                         
Network Working Group                                           M. Green
Internet-Draft                                                 CacheFlow
Expires: August 22, 2002                                         B. Cain
                                                         Cereva Networks
                                                            G. Tomlinson
                                                               CacheFlow
                                                               S. Thomas
                                                              TransNexus
                                                              P. Rzewski
                                                                 Inktomi
                                                       February 22, 2002


             Content Internetworking Architectural Overview
                    draft-ietf-cdi-architecture-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on August 22, 2002.

Copyright Notice

   Copyright (C) The Internet Society (2001). All Rights Reserved.










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Abstract

   There is wide interest in the technology for interconnecting Content
   Networks, variously called "Content Peering" or "Content
   Internetworking". We present the general architecture and core
   building blocks used in the internetworking of Content Networks.
   The scope of this work is limited to external interconnections with
   Content Networks and does not address internal mechanisms used
   within Content Networks, which for the purpose of the document are
   considered to be black boxes. This work establishes an abstract
   architectural framework to be used in the development of protocols,
   interfaces, and system models for standardized Content
   Internetworking.

Table of Contents

   1.      Introduction . . . . . . . . . . . . . . . . . . . . . . .  4
   2.      Content Internetworking System Architecture  . . . . . . .  5
   2.1     Conceptual View of Peered Content Networks . . . . . . . .  5
   2.2     Content Internetworking Architectural Elements . . . . . .  7
   3.      Request-Routing Peering System . . . . . . . . . . . . . . 11
   3.1     Request-Routing Overview . . . . . . . . . . . . . . . . . 11
   3.2     Request Routing  . . . . . . . . . . . . . . . . . . . . . 13
   3.3     System Requirements  . . . . . . . . . . . . . . . . . . . 13
   3.4     Protocol Requirements  . . . . . . . . . . . . . . . . . . 14
   3.5     Examples . . . . . . . . . . . . . . . . . . . . . . . . . 14
   3.6     Request-Routing Problems to Solve  . . . . . . . . . . . . 15
   4.      Distribution Peering System  . . . . . . . . . . . . . . . 17
   4.1     Distribution Overview  . . . . . . . . . . . . . . . . . . 17
   4.2     Distribution Models  . . . . . . . . . . . . . . . . . . . 19
   4.3     Distribution Components  . . . . . . . . . . . . . . . . . 20
   4.4     Distribution System Requirements . . . . . . . . . . . . . 20
   4.4.1   Replication Requirements . . . . . . . . . . . . . . . . . 21
   4.4.2   Signaling Requirements . . . . . . . . . . . . . . . . . . 21
   4.4.3   Advertising Requirements . . . . . . . . . . . . . . . . . 21
   4.5     Protocol Requirements  . . . . . . . . . . . . . . . . . . 22
   4.6     Distribution Problems to Solve . . . . . . . . . . . . . . 22
   4.6.1   General Problems . . . . . . . . . . . . . . . . . . . . . 22
   4.6.2   Replication Problems . . . . . . . . . . . . . . . . . . . 23
   4.6.3   Signaling Problems . . . . . . . . . . . . . . . . . . . . 23
   4.6.4   Advertising Problems . . . . . . . . . . . . . . . . . . . 23
   5.      Accounting Peering System  . . . . . . . . . . . . . . . . 25
   5.1     Accounting Overview  . . . . . . . . . . . . . . . . . . . 25
   5.2     Accounting System Requirements . . . . . . . . . . . . . . 27
   5.3     Protocol Requirements  . . . . . . . . . . . . . . . . . . 27
   6.      Security Considerations  . . . . . . . . . . . . . . . . . 28
   6.1     Threats to Content Internetworking . . . . . . . . . . . . 28
   6.1.1   Threats to the CLIENT  . . . . . . . . . . . . . . . . . . 28
   6.1.1.1 Defeat of CLIENT's Security Settings . . . . . . . . . . . 28


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   6.1.1.2 Delivery of Bad Accounting Information . . . . . . . . . . 28
   6.1.1.3 Delivery of Bad CONTENT  . . . . . . . . . . . . . . . . . 29
   6.1.1.4 Denial of Service  . . . . . . . . . . . . . . . . . . . . 29
   6.1.1.5 Exposure of Private Information  . . . . . . . . . . . . . 29
   6.1.1.6 Substitution of Security Parameters  . . . . . . . . . . . 29
   6.1.1.7 Substitution of Security Policies  . . . . . . . . . . . . 29
   6.1.2   Threats to the PUBLISHER . . . . . . . . . . . . . . . . . 29
   6.1.2.1 Delivery of Bad Accounting Information . . . . . . . . . . 29
   6.1.2.2 Denial of Service  . . . . . . . . . . . . . . . . . . . . 30
   6.1.2.3 Substitution of Security Parameters  . . . . . . . . . . . 30
   6.1.2.4 Substitution of Security Policies  . . . . . . . . . . . . 30
   6.1.3   Threats to a CN  . . . . . . . . . . . . . . . . . . . . . 30
   6.1.3.1 Bad Accounting Information . . . . . . . . . . . . . . . . 30
   6.1.3.2 Denial of Service  . . . . . . . . . . . . . . . . . . . . 30
   6.1.3.3 Transitive Threats . . . . . . . . . . . . . . . . . . . . 31
   7.      Acknowledgements . . . . . . . . . . . . . . . . . . . . . 32
           References . . . . . . . . . . . . . . . . . . . . . . . . 33
           Authors' Addresses . . . . . . . . . . . . . . . . . . . . 35
           Full Copyright Statement . . . . . . . . . . . . . . . . . 36
































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1. Introduction

   Terms in ALL CAPS, except those qualified with explicit citations
   are defined in [13].

   This memo describes the overall architectural structure and the
   fundamental building blocks used in the composition of Content
   Internetworking. Consult [13] for the system model, and vocabulary
   used in, this application domain. A key requirement of the
   architecture itself is that it be able to address each of the
   Content Internetworking scenarios enumerated in [14].  The scope of
   this work is limited to external interconnections between Content
   Networks (CN) (i.e. INTER-CN) and does not address internal
   mechanisms used within Content Networks (i.e. INTRA-CN), which for
   the purposes of the document are considered to be black boxes. This
   work is intended to establish an abstract architectural framework to
   be used in the development of protocols, interfaces and system
   models for standardized, interoperable peering among Content
   Networks.

   We first present the architecture as an abstract system.  Then we
   develop a more concrete system architecture.  For each core
   architectural element, we first present the structure of the element
   followed by system requirements. Protocol requirements for
   individual core elements are presented in accompanying works
   [17][18][15].  The assumptions and scenarios constraining the
   architecture is explained in [14].  We intend that the architecture
   should support a wide variety of business models.

   At the core of Content Internetworking are three principal
   architectural elements that constitute the building blocks of the
   Content Internetworking system.  These elements are the
   REQUEST-ROUTING PEERING SYSTEM, DISTRIBUTION PEERING SYSTEM, and
   ACCOUNTING PEERING SYSTEM.  Collectively, they control selection of
   the delivery Content Network, content distribution between peering
   Content Networks, and usage accounting, including billing settlement
   among the peering Content Networks.

   This work takes into consideration relevant IETF RFCs and IETF
   works-in-progress. In particular, it is mindful of the end-to-end
   nature [6][10] of the Internet, the current taxonomy of web
   replication and caching [11], and the accounting, authorization and
   authentication framework [12].








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2. Content Internetworking System Architecture

2.1 Conceptual View of Peered Content Networks

   Before developing the system architecture, a conceptual view of
   peered CNs is presented to frame the problem space.  CNs are
   comprised principally of four core system elements [13], the
   REQUEST-ROUTING SYSTEM, the DISTRIBUTION SYSTEM, the ACCOUNTING
   SYSTEM, and SURROGATES.  In order for CNs to peer with one another,
   it is necessary to interconnect several of the core system elements
   of individual CNs.  The interconnection of CN core system elements
   occurs through network elements called Content Peering Gateways
   (CPG). Namely, the CN core system elements that need to be
   interconnected are the REQUEST-ROUTING SYSTEM, the DISTRIBUTION
   SYSTEM, and the ACCOUNTING SYSTEM.

   Figure 1 contains a conceptual peered Content Networks diagram.


































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       +---------------+                               +---------------+
       |     CN A      |                               |    CN B       |
       |...............|   +---------+   +---------+   |.......... ....+
       |REQUEST-ROUTING|<=>|         |<=>|         |<=>|REQUEST-ROUTING|
       |...............|   | CONTENT |   | CONTENT |   |...............|
       | DISTRIBUTION  |<=>| PEERING |<=>| PEERING |<=>| DISTRIBUTION  |
       |...............|   | GATEWAY |   | GATEWAY |   |...............|
       |  ACCOUNTING   |<=>|         |<=>|         |<=>|  ACCOUNTING   |
       |---------------|   +---------+   +---------+   +---------------+
             | ^           \^ \^ \^       ^/ ^/ ^/           | ^
             v |            \\ \\ \\     // // //            v |
       +---------------+      \\ \\ \\   // // //      +---------------+
       |  SURROGATEs   |       \\ v\ v\ /v /v //       |  SURROGATEs   |
       +---------------+        \\+---------+//        +---------------+
              ^ |                v|         |v               ^ |
              | |                 | CONTENT |                | |
              | |                 | PEERING |                | |
              | |                 | GATEWAY |                | |
              | |                 |         |                | |
              | |                 +---------+                | |
              | |                   ^| ^| ^|                 | |
              | |                   || || ||                 | |
              | |                   |v |v |v                 | |
              | |               +------------- -+            | |
              | |               |    CN C       |            | |
              | |               |...............|            | |
              | |               |REQUEST-ROUTING|            | |
              | |               |...............|            | |
              \ \               | DISTRIBUTION  |            / /
               \ \              |...............|           / /
                \ \             |  ACCOUNTING   |          / /
                 \ \            |---------------|         / /
                  \ \                 | ^                / /
                   \ \                v |               / /
                    \ \         +---------------+      / /
                     \ \        |  SURROGATEs   |     / /
                      \ \       +---------------+    / /
                       \ \            | ^           / /
                        \ \           | |          / /
                         \ \          v |         / /
                          \ \     +---------+    / /
                           \ \--->| CLIENTs |---/ /
                            \-----|         |<---/
                                  +---------+


   Figure 1 Conceptual View of Peered Content Networks




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   This conceptual view illustrates the peering of three Content
   Networks; CN A, CN B, and CN C.  The CNs are peered through
   interconnection at Content Peering Gateways.  The result is
   presented as a virtual CN to CLIENTs for the DELIVERY of CONTENT by
   the aggregated set of SURROGATES.

   Note:
      Not all Content Networks contain the complete set of core
      elements.  For these Content Networks, peering will be done with
      only the core elements they do contain.

2.2 Content Internetworking Architectural Elements

   The system architecture revolves around the general premise that
   individual Content Networks are wholly contained within an
   administrative domain [3] that is composed of either autonomous
   systems [1] (physical networks) or overlay networks (virtual
   networks).  For the purpose of this memo, an overlay network is
   defined as a set of connected CN network elements layered onto
   existing underlying networks, and present the result as a virtual
   application layer to both CLIENTs and ORIGINs.  The system
   architecture for CN peering accommodates this premise by assuring
   that the information and controls are available for inter-CN-domain
   administration .  Content Internetworking involves the
   interconnection of the individual CN administrative domains through
   gateway protocols and mechanisms loosely modeled after BGP [5].

   The system architecture depends on the following assumptions:

      1.  The URI [8] name space is the basis of PUBLISHER object
          identifiers.

      2.  PUBLISHERs delegate authority of their object URI name space
          being distributed by peering CNs to the REQUEST-ROUTING
          PEERING SYSTEM.

      3.  Peering CNs use a common convention for encoding CN metadata
          into the URI name space.

   Figure 2 contains a system architecture diagram of the core elements
   involved in Content Internetworking.










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                                          +---------------+ 1
                            /-------------|REQUEST-ROUTING|<----\
                          /             4 |    PEERING    | 7   |
                        /  /------------->|    SYSTEM*    |<-\  |
                      /  /                +---------------+  |  |
                    /  /                          ^          |  |
                  /  /                            |3         |  |
                /  /                              |          |  |
              /  /                         +--------------+  |  |
            5|  |                          | DISTRIBUTION | 2|  |
             V  |                        __|    PEERING   |<-\  |
          +--------+ 6  +-----------+ 3 /  |    SYSTEM*   |  |\ |  +---------+
          |        |<---|           |<-/   +--------------+  | \ \_|         |
          | CLIENT |    | SURROGATE |                        |  \__| ORIGIN  |
          |        |--->|           |-\    +--------------+  | /-->|         |
          +--------+    +-----------+  \ 7 |  ACCOUNTING  |--//  7 +---------+
                                        \->|   PEERING    |--/
                                           |   SYSTEM*    |--\     +---------+
                                           +--------------+   \  7 | BILLING |
                                                               \-->|   ORG.  |
                                                                   |         |
                                                                   +---------+

            Note: * represents core elements of Content Internetworking


   Figure 2 System Architecture Elements of a Content Internetworking
   System

   The System Architecture is comprised of 7 major elements, 3 of which
   constitute the Content Internetworking system itself.  The peering
   elements are REQUEST-ROUTING PEERING SYSTEM, DISTRIBUTION PEERING
   SYSTEM, and ACCOUNTING PEERING SYSTEM.  Correspondingly, the system
   architecture is a system of systems:

      1.  The ORIGIN delegates its URI name space for objects to be
          distributed and delivered by the peering CNs to the
          REQUEST-ROUTING PEERING SYSTEM.

      2.  The ORIGIN INJECTS CONTENT that is to be distributed and
          delivered by the peering CNs into the DISTRIBUTION PEERING
          SYSTEM.

          Note:
             CONTENT which is to be pre-populated (pushed) within the
             peering CNs is pro-actively injected, while CONTENT which
             is to be pulled on demand is injected at the time the
             object is being requested for DELIVERY.



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      3.  The DISTRIBUTION PEERING SYSTEM moves content between CN
          DISTRIBUTION SYSTEMs. Additionally this system interacts with
          the REQUEST-ROUTING PEERING SYSTEM via feedback
          ADVERTISEMENTs to assist in the peered CN selection process
          for CLIENT requests.

      4.  The CLIENT requests CONTENT from what it perceives to be the
          ORIGIN, however due to URI name space delegation, the request
          is actually made to the REQUEST-ROUTING PEERING SYSTEM.

          Note:
             The request routing function may be implied by an in-path
             network element such as caching proxy, which is typical
             for a Access Content Network.  In this case, request
             routing is optimized to a null function, since the CLIENT
             is a priori mapped to the SURROGATE.

      5.  The REQUEST-ROUTING PEERING SYSTEM routes the request to a
          suitable SURROGATE in a peering CN.  REQUEST-ROUTING PEERING
          SYSTEMs interact with one another via feedback ADVERTISEMENTs
          in order to keep request-routing tables current.

      6.  The selected SURROGATE delivers the requested content to the
          CLIENT. Additionally, the SURROGATE sends accounting
          information for delivered content to the ACCOUNTING PEERING
          SYSTEM.

      7.  The ACCOUNTING PEERING SYSTEM aggregates and distills the
          accounting information into statistics and content detail
          records for use by the ORIGIN and BILLING ORGANIZATION.
          Statistics are also used as feedback to the REQUEST-ROUTING
          PEERING SYSTEM.

      8.  The BILLING ORGANIZATION uses the content detail records to
          settle with each of the parties involved in the content
          distribution and delivery process.

   This process has been described in its simplest form in order to
   present the Content Internetworking architecture in the most
   abstract way possible.  In practice, this process is more complex
   when applied to policies, business models and service level
   agreements that span multiple peering Content Networks.  The
   orthogonal core peering systems are discussed in greater depth in
   Section 3, Section 4 and Section 5 respectively.







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   Note:
      Figure 2 simplifies the presentation of the core Content
      Internetworking elements as single boxes, when in fact they
      represent a collection of CPGs and interconnected individual CN
      core system elements. This has been done to introduce the system
      architecture at its meta level.

   The system architecture does not impose any administrative domain
   [3] restrictions on the core peering elements (REQUEST-ROUTING
   PEERING SYSTEM, DISTRIBUTION PEERING SYSTEM and ACCOUNTING PEERING
   SYSTEM).  The only requirement is that they be authorized by the
   principal parties (ORIGIN and peering CNs) to act in their behalf.
   Thus, it is possible for each of the core elements to be provided by
   a different organization.





































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3. Request-Routing Peering System

   The REQUEST-ROUTING PEERING SYSTEM represents the request-routing
   function of the Content Internetworking system.  It is responsible
   for routing CLIENT requests to an appropriate peered CN for the
   delivery of content.

   Note:
      When the DISTRIBUTION PEERING SYSTEM and/or the ACCOUNTING
      PEERING SYSTEM is present, it is highly desirable to utilize
      content location information within the peered CNs and/or system
      load information in the selection of appropriate peered CNs in
      the routing of requests.

3.1 Request-Routing Overview

   REQUEST-ROUTING SYSTEMs route CLIENT requests to a suitable
   SURROGATE, which is able to service a client request.  Many
   request-routing systems route users to the surrogate that is
   "closest" to the requesting user, or to the "least loaded"
   surrogate.  However, the only requirement of the request-routing
   system is that it route users to a surrogate that can serve the
   requested content.

   REQUEST-ROUTING PEERING is the interconnection of two or more
   REQUEST-ROUTING SYSTEMs so as to increase the number of REACHABLE
   SURROGATEs for at least one of the interconnected systems.

   In order for a PUBLISHER's CONTENT to be delivered by multiple
   peering CNs, it is necessary to federate each Content Network
   REQUEST-ROUTING SYSTEM under the URI name space of the PUBLISHER
   object.  This federation is accomplished by first delegating
   authority of the PUBLISHER URI name space to an AUTHORITATIVE
   REQUEST-ROUTING SYSTEM. The AUTHORITATIVE REQUEST-ROUTING SYSTEM
   subsequently splices each peering Content Network REQUEST-ROUTING
   SYSTEM into this URI name space and transitively delegates URI name
   space authority to them for their participation in request-routing.
   Figure 3 is a diagram of the entities involved in the
   REQUEST-ROUTING PEERING SYSTEM.

   Note:
      For the null request routing case (in path caching proxy
      present), the caching proxy acts as the SURROGATE.  In this case,
      the SURROGATE performs the request routing via its
      pre-established proxy relationship with the CLIENT and is
      implicitly the terminating level of request routing.  In essence,
      the SURROGATE is federated into the URI namespace without the
      need to communicate with the AUTHORITATIVE REQUEST-ROUTING SYSTEM.



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                                +---------------+
                                |     CLIENT    |
                                +---------------+
                                        |
   (Request-Routing Tree Root)  +---------------+
                                | AUTHORITATIVE |
                                |REQUEST-ROUTING|
                                |     SYSTEM    |
                                +---------------+
                                       | | INTER-CN Request-Routing
                      /----------------/ \-----------------\
                      |                                    |
   (1st Level) +---------------+                     +---------------+
      .........|REQUEST-ROUTING|..........  .........|REQUEST-ROUTING|.........
      . CN A   |     CPG       |         .  . CN B   |      CPG      |        .
      .        +---------------+         .  .        +---------------+        .
      .               |                  .  .                |                .
      .        +---------------+         .  .        +---------------+        .
      .        |REQUEST-ROUTING|         .  .        |REQUEST-ROUTING|        .
      .        |    SYSTEM     |         .  .        |    SYSTEM     |        .
      .        +---------------+         .  .        +---------------+        .
      .              | |                 .  .               | |               .
      .         /---/   \-------\        .  .        /-----/   \----\         .
      .         |               |        .  .        |              |         .
      . +---------------+       |        .  .        |              |         .
      . |REQUEST-ROUTING| +------------+ .  . +-----------+    +------------+ .
      ..|      CPG      |.| SURROGATEs |..  ..| SURROGATE |....| SURROGATES |..
        +---------------+ +------------+      +-----------+    +------------+
                | INTER-CN Recursive Request-Routing
                \------\
                       |
   (2nd Level) +---------------+
      .........|REQUEST-ROUTING|..........
      . CN C   |     CPG       |         .
      .        +---------------+         .
      ,               |                  .
      .        +---------------+         .
      .        |REQUEST-ROUTING|         .
      .        |    SYSTEM     |         .
      .        +---------------+         .
      .              | |                 .
      .        /----/   \-----\          .
      .        |              |          .
      . +-----------+    +------------+  .
      ..| SURROGATE |....| SURROGATEs |...
        +-----------+    +------------+

   Figure 3 REQUEST-ROUTING PEERING SYSTEM Architecture



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   The REQUEST-ROUTING PEERING SYSTEM is hierarchical in nature. There
   exists exactly one request-routing tree for each PUBLISHER URI.  The
   AUTHORITATIVE REQUEST-ROUTING SYSTEM is the root of the
   request-routing tree.  There may be only one AUTHORITATIVE
   REQUEST-ROUTING SYSTEM for a URI request-routing tree. Subordinate
   to the AUTHORITATIVE REQUEST-ROUTING SYSTEM are the REQUEST-ROUTING
   SYSTEMs of the first level peering CNs. There may exist recursive
   subordinate REQUEST-ROUTING SYSTEMs of additional level peering CNs.

   Note:
      A PUBLISHER object may have more than one URI associated with it
      and therefore be present in more than one request-routing tree.

3.2 Request Routing

   The actual "routing" of a client request is through REQUEST-ROUTING
   CPGs.  The AUTHORITATIVE REQUEST-ROUTING CPG receives the CLIENT
   request and forwards the REQUEST to an appropriate DISTRIBUTING CN.
   This process of INTER-CN request-routing may occur multiple times in
   a recursive manner between REQUEST-ROUTING CPGs until the
   REQUEST-ROUTING SYSTEM arrives at an appropriate DISTRIBUTING CN to
   deliver the content.

   Note:
      The Client request may be for resolution of a  URI component and
      not the content of the URI itself.  This is the case when DNS is
      being utilized in the request-routing process to resolve the URI
      server component.

   Request-Routing systems explicitly peer but do not have "interior"
   knowledge of surrogates from other CNs.  Each CN operates its
   internal request-routing system.  In this manner, request-routing
   systems peer very much like IP network layer peering.

3.3 System Requirements

   We assume that there is a peering relationship between
   REQUEST-ROUTING CPGs. This peering relationship at a minimum must
   exchange a set of CLIENT IP addresses that can be serviced, and a
   set of information about the DISTRIBUTION SYSTEMs, for which they
   are performing request-routing.










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   Request-Routing Requirements

   1.  Use of a URI name space based request-routing mechanism.  The
       request-routing mechanism is allowed to use as much of the URI
       name space as it needs to select the proper SURROGATE.  For
       example, DNS based mechanisms utilize only the host
       subcomponent, while content aware mechanisms utilize use
       multiple components.

   2.  Normalized canonical URI name space structure for peered CN
       distribution of PUBLISHER objects.  The default in the absence
       of encoded meta data is the standard components as defined by
       [8].  Encoded meta data must conform to the syntactical grammar
       defined in [7].

   3.  Single AUTHORITATIVE REQUEST-ROUTING SYSTEM for PUBLISHER object
       URI name space.

   4.  Assure that the request-routing tree remains a tree -- i.e., has
       no cycles.

   5.  Assure that adjacent request-routing systems from different
       administrative domains (different CNs) use a compatible
       request-routing mechanism.

   6.  Assure that adjacent request-routing systems from different
       administrative domains (different CNs) agree to forward requests
       for the CONTENT in question.

   7.

       [Editor Note:
          System requirements being generated in the request-routing
          peering protocol design team have not yet been reconciled and
          integrated into this document.]

3.4 Protocol Requirements

   Consult [17] for request-routing peering protocol requirements.

3.5 Examples

   Consult [16] for in-depth information on known request-routing
   systems.







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3.6 Request-Routing Problems to Solve

   [Editor Note:
      This section is being preserved until it has been determined that
      these issues have been addressed in the request-routing peering
      protocol requirements draft.]

   Specific problems in request-routing needing further investigation
   include:

   1.  What is the aggregated granularity of CLIENT IP address being
       serviced by a peering CN's DISTRIBUTION SYSTEM?

   2.  How do DNS request-routing systems forward a request?  If a
       given CN is peered with many other CNs, what are the criteria
       that forwards a request to another CN?

   3.  How do content-aware request-routing systems forward a request?
       If a given CN is peered with many other CNs, what are the
       criteria that forwards a request to another CN?

   4.  What are the merits of designing a generalized content routing
       protocol, rather than relying on request-routing mechanisms.

   5.  What is the normalized canonical URI name space for
       request-routing? Because request-routing is federated across
       multiple CNs, it is necessary to have agreed upon standards for
       the encoding of meta data in URIs.  There are many potential
       elements, which may be encoded.  Some of these elements are:
       authoritative agent domain, publisher domain, content type,
       content length, etc.

   6.  How are policies communicated between the REQUEST-ROUTING SYSTEM
       and the DISTRIBUTION ADVERTISEMENT SYSTEM?  A given CN may wish
       to serve only a given content type or a particular set of users.
       These types of policies must be communicated between CNs.

   7.  What are the request-routing protocols in DNS? When a request is
       routed to a particular REQUEST-ROUTING CPG, a clear set of DNS
       rules and policies must be followed in order to have a workable
       and predictable system.

   8.  How do we protect the REQUEST-ROUTING SYSTEM against denial of
       service attacks?







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   9.  How do we select the appropriate peering CN for DELIVERY?

             The selection process must to consider the distribution
             policies involved in Section 4.  Investigation into other
             policy "work in progress" within the IETF is needed to
             understand the relationship of policies developed within
             Content Internetworking.












































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4. Distribution Peering System

   The DISTRIBUTION PEERING SYSTEM represents the content distribution
   function of the CN peering system. It is responsible for moving
   content from one DISTRIBUTION CPG to another DISTRIBUTION CPG and
   for supplying content location information to the REQUEST-ROUTING
   PEERING SYSTEM.

4.1 Distribution Overview

   One goal of the Content Internetworking system is to move content
   closer to the CLIENT. Typically this is accomplished by copying
   content from its ORIGIN to SURROGATEs.  The SURROGATEs then have the
   CONTENT available when it is requested by a CLIENT. Even with a
   single PUBLISHER and single CN, the copying of CONTENT to a
   SURROGATE may traverse a number of links, some in the PUBLISHER's
   network, some in the CN's network, and some between those two
   networks.  For DISTRIBUTION PEERING, we consider only the
   communication "between" two networks, and ignore the mechanisms for
   copying CONTENT within a network.

   In the above example the last server on the content provider's
   network in the path, and the first server on the CN's network in the
   path, must contain DISTRIBUTION CPGs which communicate directly with
   each other. The DISTRIBUTION CPGs could be located in the ORIGIN
   server and the SURROGATE server. Thus in the simplest form the
   ORIGIN server is in direct contact with the SURROGATE. However the
   DISTRIBUTION CPG in the content provider's network could aggregate
   content from multiple ORIGIN servers and the DISTRIBUTION CPG in the
   CN's network could represent multiple SURROGATEs. These DISTRIBUTION
   CPGs could then be co-located in an exchange facility.  In fact,
   given the common practice of independently managed IP peering
   co-location exchange facilities for layer 3, there exists the
   distinct opportunity to create similar exchanges for CPGs.

   Figure 4 is a diagram of the entities involved in the DISTRIBUTION
   PEERING SYSTEM.














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                                     +--------+
                                     | ORIGIN |
                                     +--------+
                                         |  | INJECTION
                      /------------------/  \----------------\
                      |                                      |
               +--------------+                        +--------------+
      .........| DISTRIBUTION |...........  ...........| DISTRIBUTION |........
      . CN A   |     CPG      |          .  . CN B     |     CPG      |       .
      .        +--------------+          .  .          +--------------+       .
      .               |                  .  .                 |               .
      .        +--------------+          .  .          +--------------+       .
      .        | DISTRIBUTION |          .  .          | DISTRIBUTION |       .
      .        |    SYSTEM    |          .  .          |    SYSTEM    |       .
      .        +--------------+          .  .          +--------------+       .
      .              | |                 .  .              |  |               .
      .       /-----/   \-------\        .  .        /-----/   \----\         .
      .       |                 |        .  .        |              |         .
      .       |        +--------------+  .  . +--------------+      |         .
      . +------------+ | DISTRIBUTION |  .  . | DISTRIBUTION | +------------+ .
      ..| SURROGATEs |.|     CPG      |...  ..|     CPG      |.| SURROGATEs |..
        +------------+ +--------------+       +--------------+ +------------+
                             |   |                 |   |
                             |   \-----------------/   |
                             \----------\  /-----------/
                                        |  |    INTER-CN DISTRIBUTION PEERING
                                        |  |
                                   +--------------+
                          .........| DISTRIBUTION |...........
                          . CN C   |     CPG      |          .
                          .        +--------------+          .
                          .               |                  .
                          .        +--------------+          .
                          .        | DISTRIBUTION |          .
                          .        |    SYSTEM    |          .
                          .        +--------------+          .
                          .              | |                 .
                          .       /-----/   \-------\        .
                          .       |                 |        .
                          .       |                 |        .
                          . +-----------+     +------------+ .
                          ..| SURROGATE |.....| SURROGATEs |..
                            +-----------+     +------------+



   Figure 4 DISTRIBUTION PEERING SYSTEM Architecture




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   While Content Internetworking in general relates to interfacing with
   CNs, there are two CN distribution peering relationships we expect
   to be common; INTER-CN distribution peering and INJECTION peering.
   INTER-CN distribution peering involves distributing CONTENT between
   individual CNs in a inter-network of peered CNs. INJECTION peering
   involves the publishing of CONTENT directly into CNs by ORIGINs.

4.2 Distribution Models

   Replication ADVERTISEMENTs may take place in a model similar to the
   way IP routing table updates are done between BGP routers.
   DISTRIBUTION CPGs could take care of exterior content replication
   between content providers and CNs, while at the same time performing
   content replication interior to their networks in an independent
   manner. If this model is used then the internal structure of the
   networks is hidden and the only knowledge of other networks is the
   locations of DISTRIBUTION CPGs.

   Replication of content may take place using a push model, or a pull
   model, or a combination of both. Use initiated replication, where
   SURROGATEs, upon getting a cache miss, retrieve CONTENT from the
   DISTRIBUTION SYSTEM, represents the pull model.  ORIGIN initiated
   replication of CONTENT to SURROGATEs represents the push model.
   DISTRIBUTION CPGs may be located at various points in these models
   depending on the topologies of the networks involved.

   With Content Internetworking it may be desirable to replicate
   content through a network, which has no internal SURROGATEs.  For
   example add a exchange network between the content provider network
   and the CN network to the example above. The exchange network could
   have a DISTRIBUTION CPG co-located with the content provider's
   DISTRIBUTION CPG, which acts as a proxy for the CN. The exchange
   network could also have a DISTRIBUTION CPG co-located with the CN's
   DISTRIBUTION CPG, which acts as a proxy for the content provider. In
   a consolidated example, the exchange network could have a single
   DISTRIBUTION CPG that acts as a proxy for both the content provider
   and the CN.

   Replication of CONTINUOUS MEDIA that is not to be cached on
   SURROGATEs, such as live streaming broadcasts, takes place in a
   different model from content that is to be persistently stored.
   Replication in this case, typically takes the form of splitting the
   live streaming data at various points in the network. In Content
   Internetworking, DISTRIBUTION CPGs may support CONTINUOUS MEDIA
   splitting replication, as they likely provide ideal network
   topologic points for application layer multicasting.





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4.3 Distribution Components

   The three main components of DISTRIBUTION PEERING are replication,
   signaling and advertising.

   The first component of content distribution is replication.
   Replication involves moving the content from an ORIGIN server to
   SURROGATE servers. The immediate goal in CN peering is moving the
   content between DISTRIBUTION CPGs.

   The second component of content distribution is content signaling.
   Content signaling is the propagation of content meta-data. This
   meta-data may include such information such as the immediate
   expiration of content or a change in the expiration time of CONTENT.
   The immediate goal in signaling is exchanging signals between
   DISTRIBUTION CPGs.

   The third component of content distribution is content advertising.
   Content providers must be able to advertise content that can be
   distributed by CNs and its associated terms. It is important that
   the advertising of content must be able to aggregate content
   information.  The immediate goal in advertising is exchanging
   advertisements between DISTRIBUTION CPGs.

4.4 Distribution System Requirements

   Replication systems must have a peering relationship. This peering
   relationship must exchange sets of aggregated content and its
   meta-data. Meta-data may change over time independently of the
   content data and must be exchanged independently as well.





















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4.4.1 Replication Requirements

   The specific requirements in content replication are:

   1.  A common protocol for the replication of content.

   2.  A common format for the actual content data in the protocol.

   3.  A common format for the content meta-data in the protocol.

   4.  Security mechanisms (see Section 6).

   5.  Scalable distribution of the content.

4.4.2 Signaling Requirements

   The specific requirements in content signaling are:

   1.  Signals for (at least) "flush" and "expiration time update".

   2.  Security mechanisms (see Section 6).

   3.  Scalable distribution of the signals on a large scale.

       Editor Note:
          We have to start being quantitative about what we mean by
          "large scale".  Are we thinking in terms of the number of
          content items, the number of networks, or the number of
          signals?  For each of those, how big is "large scale"?

   4.  Content location and serviced CLIENT IP aggregate address
       exchanges with REQUEST-ROUTING CPGs.

4.4.3 Advertising Requirements

   The specific requirements in CONTENT ADVERTISEMENT are:

   1.  A common protocol for the ADVERTISEMENT of CONTENT.

   2.  A common format for the actual ADVERTISEMENTs in the protocol.

       Editor Note:
          The following requirements need further discussion.  As it
          stands now, there isn't sufficient information to
          substantiate them.

   3.  A well-known state machine.

   4.  Use of TCP or SCTP (because soft-state protocols will not scale).


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   5.  Well-known error codes to diagnose protocols between different
       networks.

   6.  Capability negotiation.

   7.  Ability to represent policy.

   [Editor Note:
      System requirements being generated in the distribution peering
      protocol design team have not yet been reconciled and integrated
      into this document.]

4.5 Protocol Requirements

   Consult [18] for distribution peering protocol requirements.

4.6 Distribution Problems to Solve

   [Editor Note:
      This section is being preserved until it has been determined that
      these issues have been addressed in the distribution peering
      protocol requirements draft.]

   Some of the problems in distribution revolve around supporting both
   a push model and a pull model for replication of content in that
   they are not symmetric. The push model is used for pre-loading of
   content and the pull model is used for on-demand fetching and
   pre-fetching of content. These models are not symmetric in that the
   amount of available resources in which to place the content on the
   target server must be known. In the fetching cases the server that
   pulls the content knows the available resources on the target
   server, itself. In the pre-loading case the server that pushes the
   content must find out the available resources from the target server
   before pushing the data.

4.6.1 General Problems

   General problems in distribution peering needing further
   investigation include:

   1.  How would a single distribution peering protocol adequately
       support replication, signaling and advertising?

   2.  Should a single distribution peering protocol be considered,
       rather than separate protocols for each component?

   3.  How do we prevent looping of distribution updates?  That is to
       say, detect and stop propagating replication, signaling and
       advertisement of events a DISTRIBUTION CPG has already issued.


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       Looping here has the possibility of becoming infinite, if not
       bounded by the protocol(s).  IP route updating and forwarding
       has faced similar issues and has solved them.

4.6.2 Replication Problems

   Specific problems in replication needing further investigation
   include:

   1.  How do replication systems forward a request?

   2.  How do we keep pull based replication serviced within the
       DISTRIBUTION CPGs in order to prevent it from inadvertently
       bleeding out into REQUEST-ROUTING SYSTEM and potentially getting
       into a recursive loop?

   3.  How are policies communicated between the replication systems?

   4.  What are the replication protocols?

   5.  Does replication only take place between CPGs?

4.6.3 Signaling Problems

   Specific problems in content signaling needing further investigation
   include:

   1.  How do we represent a content signal?

   2.  What content meta-data needs to be signaled?

   3.  How do we represent aggregates of meta-data in a concise and
       compressed manner?

   4.  What protocol(s) should be used for content signals?

   5.  What is a scalable architecture for delivering content signals?

   6.  Do content signals need a virtual distribution system of their
       own?

4.6.4 Advertising Problems

   Specific problems in CONTENT ADVERTISEMENT needing further
   investigation include:

   1.  How do we represent aggregates of content to be distributed in a
       concise and compressed manner?



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   2.  What protocol(s) should be used for the aggregation of this data?

   3.  What are the issues involved in the creation of CPG exchanges?
       This is actually a broader question than just for distribution,
       but needs to be considered for all forms of CPGs
       {REQUEST-ROUTING, DISTRIBUTION, ACCOUNTING}.













































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5. Accounting Peering System

   The ACCOUNTING PEERING SYSTEM represents the accounting data
   collection function of the Content Internetworking system. It is
   responsible for moving accounting data from one ACCOUNTING CPG to
   another ACCOUNTING CPG.

5.1 Accounting Overview

   Content Internetworking must provide the ability for the content
   provider to collect data regarding the delivery of their CONTENT by
   the peered CNs. ACCOUNTING CPGs exchange the data collected by the
   interior ACCOUNTING SYSTEMS. This interior data may be collected
   from the SURROGATEs by ACCOUNTING CPGs using SNMP or FTP, for
   example. ACCOUNTING CPGs may transfer the data to exterior
   neighboring ACCOUNTING CPGs on request (push), in an asynchronous
   manner (push), or a combination of both. Accounting data may also be
   aggregated before it is transferred.

   Figure 5 is a diagram of the entities involved in the ACCOUNTING
   PEERING SYSTEM.






























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                      +---------+
                      | BILLING |                +--------+
                      |   ORG.  |                | ORIGIN |
                      +---------+                +--------+
                  BILLING | | ACCOUNTING PEERING    | |  ORIGIN ACCOUNTING PEERING
                    /-----/ \-----------------------|-|----\
                    | /-----------------------------/ \----|-\
                    | |                                    | |
               +--------------+                        +--------------+
      .........|  ACCOUNTING  |...........  ...........| ACCOUNTING   |........
      . CN A   |     CPG      |          .  . CN B     |     CPG      |       .
      .        +--------------+          .  .          +--------------+       .
      .               |                  .  .                 |               .
      .        +--------------+          .  .          +--------------+       .
      .        |  ACCOUNTING  |          .  .          |  ACCOUNTING  |       .
      .        |    SYSTEM    |          .  .          |    SYSTEM    |       .
      .        +--------------+          .  .          +--------------+       .
      .              | |                 .  .              |  |               .
      .       /-----/   \-------\        .  .        /-----/   \----\         .
      .       |                 |        .  .        |              |         .
      .       |        +--------------+  .  . +--------------+      |         .
      . +------------+ |  ACCOUNTING  |  .  . |  ACCOUNTING  | +------------+ .
      ..| SURROGATEs |.|     CPG      |...  ..|     CPG      |.| SURROGATEs |..
        +------------+ +--------------+       +--------------+ +------------+
                             |   |                 |   |
                             |   \-----------------/   |
                             \----------\  /-----------/
                                        |  |    INTER-CN ACCOUNTING PEERING
                                        |  |
                                   +--------------+
                          .........|  ACCOUNTING  |...........
                          . CN C   |     CPG      |          .
                          .        +--------------+          .
                          .               |                  .
                          .        +--------------+          .
                          .        |  ACCOUNTING  |          .
                          .        |    SYSTEM    |          .
                          .        +--------------+          .
                          .              | |                 .
                          .       /-----/   \-------\        .
                          .       |                 |        .
                          .       |                 |        .
                          . +-----------+     +------------+ .
                          ..| SURROGATE |.....| SURROGATEs |..
                            +-----------+     +------------+


   Figure 5 ACCOUNTING Peering system Architecture



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   There are three CN accounting peering relationships we expect to be
   common; INTER-CN accounting peering, BILLING ORGANIZATION accounting
   peering and ORIGIN accounting peering.  INTER-CN accounting peering
   involves exchanging accounting information between individual CNs in
   a inter-network of peered CNs. BILLING ORGANIZATION peering involves
   exchanging to accounting information between CNs and a billing
   organization.  ORIGIN accounting peering involves the exchanging of
   accounting information between CNs and ORIGINs.

   Note:
      It is not necessary for an ORIGIN to peer directly with multiple
      CNs in order to participate in Content Internetworking.  ORIGINs
      participating in a single home CN will be indirectly peered by
      their home CN with the inter-network of CNs the home CN is a
      member of.  Nor is it necessary to have a BILLING ORGANIZATION
      peer, since this function may also be provided by the home CN.
      However, ORIGINs that directly peer for ACCOUNTING may have
      access to greater accounting detail.  Also, through the use of
      ACCOUNTING peering, 3rd party billing can be provided.

5.2 Accounting System Requirements

   [Editor Note:
      System requirements being generated in the accounting peering
      protocol design team have not yet been reconciled and integrated
      into this document.]

5.3 Protocol Requirements

   Consult [15] for accounting peering protocol requirements.





















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6. Security Considerations

   Security concerns with respect to Content Internetworking can be
   generally categorized into trust within the system and protection of
   the system from threats. The trust model utilized with Content
   Internetworking is predicated largely on transitive trust between
   the ORIGIN, REQUEST-ROUTING PEERING SYSTEM, DISTRIBUTION PEERING
   SYSTEM, ACCOUNTING PEERING SYSTEM and SURROGATES.  Network elements
   within the Content Internetworking system are considered to be
   "insiders" and therefore trusted.

6.1 Threats to Content Internetworking

   The following sections document key threats to CLIENTs, PUBLISHERs,
   and CNs. The threats are classified according to the party that they
   most directly harm, but, of course, a threat to any party is
   ultimately a threat to all. (For example, having a credit card
   number stolen may most directly affect a CLIENT; however, the
   resulting dissatisfaction and publicity will almost certainly cause
   some harm to the PUBLISHER and CN, even if the harm is only to those
   organizations' reputations.)

6.1.1 Threats to the CLIENT

6.1.1.1 Defeat of CLIENT's Security Settings

   Because the SURROGATE's location may differ from that of the ORIGIN,
   the use of a SURROGATE may inadvertently or maliciously defeat any
   location-based security settings employed by the CLIENT. And since
   the SURROGATE's location is generally transparent to the CLIENT, the
   CLIENT may be unaware that its protections are no longer in force.
   For example, a CN may relocate CONTENT from a Internet Explorer
   user's "Internet Web Content Zone"  to that user's "Local Intranet
   Web Content Zone." If the relocation is visible to the Internet
   Explorer browser but otherwise invisible to the user, the browser
   may be employing less stringent security protections than the user
   is expecting for that CONTENT. (Note that this threat differs, at
   least in degree, from the substitution of security parameters threat
   below, as Web Content Zones can control whether or not, for example,
   the browser executes unsigned active content.)

6.1.1.2 Delivery of Bad Accounting Information

   In the case of CONTENT with value, CLIENTs may be inappropriately
   charged for viewing content that they did not successfully access.
   Conversely, some PUBLISHERs may reward CLIENTs for viewing certain
   CONTENT (e.g. programs that "pay" users to surf the Web). Should a
   CN fail to deliver appropriate accounting information, the CLIENT
   may not receive appropriate credit for viewing the required CONTENT.


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6.1.1.3 Delivery of Bad CONTENT

   A CN that does not deliver the appropriate CONTENT may provide the
   user misleading information (either maliciously or inadvertently).
   This threat can be manifested as a failure of either the
   DISTRIBUTION SYSTEM (inappropriate content delivered to appropriate
   SURROGATEs) or REQUEST-ROUTING SYSTEM (request routing to
   inappropriate SURROGATEs, even though they may have appropriate
   CONTENT), or both. A REQUEST-ROUTING SYSTEM may also fail by
   forwarding the CLIENT request when no forwarding is appropriate, or
   by failing to forward the CLIENT request when forwarding is
   appropriate.

6.1.1.4 Denial of Service

   A CN that does not forward the CLIENT appropriately may deny the
   CLIENT access to CONTENT.

6.1.1.5 Exposure of Private Information

   CNs may inadvertently or maliciously expose private information
   (passwords, buying patterns, page views, credit card numbers) as it
   transits from SURROGATEs to ORIGINs and/or PUBLISHERs.

6.1.1.6 Substitution of Security Parameters

   If a SURROGATE does not duplicate completely the security facilities
   of the ORIGIN (e.g. encryption algorithms, key lengths, certificate
   authorities) CONTENT delivered through the SURROGATE may be less
   secure than the CLIENT expects.

6.1.1.7 Substitution of Security Policies

   If a SURROGATE does not employ the same security policies and
   procedures as the ORIGIN, the CLIENT's private information may be
   treated with less care than the CLIENT expects. For example, the
   operator of a SURROGATE may not have as rigorous protection for the
   CLIENT's password as does the operator of the ORIGIN server. This
   threat may also manifest itself if the legal jurisdiction of the
   SURROGATE differs from that of the ORIGIN, should, for example,
   legal differences between the jurisdictions require or permit
   different treatment of the CLIENT's private information.

6.1.2 Threats to the PUBLISHER

6.1.2.1 Delivery of Bad Accounting Information

   If a CN does not deliver accurate accounting information, the
   PUBLISHER may be unable to charge CLIENTs for accessing CONTENT or


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   it may reward CLIENTs inappropriately. Inaccurate accounting
   information may also cause a PUBLISHER to pay for services (e.g.
   content distribution) that were not actually rendered.) Invalid
   accounting information may also effect PUBLISHERs indirectly by, for
   example, undercounting the number of site visitors (and, thus,
   reducing the PUBLISHER's advertising revenue).

6.1.2.2 Denial of Service

   A CN that does not distribute CONTENT appropriately may deny CLIENTs
   access to CONTENT.

6.1.2.3 Substitution of Security Parameters

   If a SURROGATE does not duplicate completely the security services
   of the ORIGIN (e.g. encryption algorithms, key lengths, certificate
   authorities, client authentication) CONTENT stored on the SURROGATE
   may be less secure than the PUBLISHER prefers.

6.1.2.4 Substitution of Security Policies

   If a SURROGATE does not employ the same security policies and
   procedures as the ORIGIN, the CONTENT may be treated with less care
   than the PUBLISHER expects. This threat may also manifest itself if
   the legal jurisdiction of the SURROGATE differs from that of the
   ORIGIN, should, for example, legal differences between the
   jurisdictions require or permit different treatment of the CONTENT.

6.1.3 Threats to a CN

6.1.3.1 Bad Accounting Information

   If a CN is unable to collect or receive accurate accounting
   information, it may be unable to collect compensation for its
   services from PUBLISHERs.

6.1.3.2 Denial of Service

   Misuse of a CN may make that CN's facilities unavailable, or
   available only at reduced functionality, to legitimate customers or
   the CN provider itself. Denial of service attacks can be targeted at
   a CN's ACCOUNTING SYSTEM, DISTRIBUTION SYSTEM, or REQUEST-ROUTING
   SYSTEM.








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6.1.3.3 Transitive Threats

   To the extent that a CN acts as either a CLIENT or a PUBLISHER (such
   as, for example, in transitive implementations) such a CN may be
   exposed to any or all of the threats described above for both roles.














































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7. Acknowledgements

   The authors would like to acknowledge the contributions and comments
   of Mark Day (Cisco), Fred Douglis (AT&T), Patrik Falstrom (Cisco),
   Don Gilletti (CacheFlow), Barron Housel (Cisco) John Martin (Network
   Appliance), Raj Nair (Cisco), Hilarie Orman (Novell), Doug Potter
   (Cisco), John Scharber (CacheFlow), and Oliver Spatscheck (AT&T).












































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References

   [1]   Hawkinson, J. and T. Bates, "Guidelines for creation,
         selection, and registration of an Autonomous System (AS)", BCP
         6, March 1996,
         <URL:http://www.rfc-editor.org/rfc/bcp/bcp6.txt>.

   [2]   Postel, J., "Internet Protocol, DARPA Internet Program
         Protocol Specification", RFC 791, September 1981,
         <URL:http://www.rfc-editor.org/rfc/rfc791.txt>.

   [3]   Hares, S. and D. Katz, "Administrative Domains and Routing
         Domains A Model for Routing in the Internet", RFC 1136,
         December 1989,
         <URL:http://www.rfc-editor.org/rfc/rfc1136.txt>.

   [4]   Postel, J., "Domain Name Structure and Delegation", RFC 1591,
         March 1994,
         <URL:http://www.rfc-editor.org/rfc/rfc1591.txt>.

   [5]   Rekhter, Y. and T. Li, "A Border Gateway Protocol 4 (BGP-4)",
         RFC 1771, March 1995,
         <URL:http://www.rfc-editor.org/rfc/rfc1771.txt>.

   [6]   Carpenter, B., "Architecture Principles of the Internet", RFC
         1958, June 1996,
         <URL:http://www.rfc-editor.org/rfc/rfc1958.txt>.

   [7]   Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming
         Protocol", RFC 2326, April 1998,
         <URL:http://www.rfc-editor.org/rfc/rfc2326.txt>.

   [8]   Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
         Resource Identifiers (URI): Generic Syntax", RFC 2396, August
         1998,
         <URL:http://www.rfc-editor.org/rfc/rfc2396.txt>.

   [9]   Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter,
         L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol
         -- HTTP/1.1", RFC 2616, June 1999,
         <URL:http://www.rfc-editor.org/rfc/rfc2616.txt>.

   [10]  Carpenter, B., "Internet Transparency", RFC 2775, February
         2000,
         <URL:http://www.rfc-editor.org/rfc/rfc2775.txt>.

   [11]  Cooper, I., Melve, I. and G. Tomlinson, "Internet Web
         Replication and Caching Taxonomy", RFC 3040, January 2001,
         <URL:http://www.ietf.org/rfc/rfc3040.txt>.


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   [12]  Volbrecht, J., Calhoun, P., Farrell, S., Gommans, L., Gross,
         G., de Bruijn, B., de Laat, C., Holdrege, M. and D. Spence,
         "AAA Authorization Framework",
         draft-ietf-aaa-authz-arch-00.txt (work in progress), October
         1999,
         <URL:http://www.ietf.org/internet-drafts/draft-ietf-aaa-authz-a
         rch-00.txt>.

   [13]  Day, M., Cain, B., Tomlinson, G. and P. Rzewski, "A Model for
         Content Internetworking", draft-day-cdnp-model-05.txt (work in
         progress), March 2001,
         <URL:http://www.ietf.org/internet-drafts/draft-day-cdnp-model-0
         5.txt>.

   [14]  Day, M., Gilletti, D. and P. Rzewski, "Content Internetworking
         Scenarios", draft-day-cdnp-scenarios-03.txt (work in
         progress), March 2001,
         <URL:http://www.ietf.org/internet-drafts/draft-day-cdnp-scenari
         os-03.txt>.

   [15]  Gilletti, D., Nair, R., Scharber, J. and J. Guha, "Content
         Internetworking Authentication, Authorization, and  Accounting
         Requirements", draft-gilletti-cdnp-aaa-reqs-01.txt (work in
         progress), January 2001,
         <URL:http://www.ietf.org/internet-drafts/draft-gilletti-cdnp-aa
         a-reqs-01.txt>.

   [16]  Barbir, A., Cain, B., Douglis, F., Green, M., Hofmann, M.,
         Nair, R., Potter, D. and O. Spatscheck, "Known CDN
         Request-Routing Mechanisms",
         draft-cain-cdnp-known-request-routing-01.txt (work in
         progress), February 2001.

   [17]  Cain, B., Spatscheck, O., May, M. and A. Barbir,
         "Request-Routing Requirements for Content Internetworking",
         draft-ietf-cain-request-routing-req-01.txt (work in progress),
         March 2001.

   [18]  Amini, L., Thomas, S. and O. Spatscheck, "Distribution Peering
         Requirements for Content Distribution Internetworking",
         draft-amini-cdi-distribution-reqs-00.txt (work in progress),
         February 2001.









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Authors' Addresses

   Mark Green
   CacheFlow Inc.
   650 Almanor Avenue
   Sunnyvale, CA  94086
   US

   Phone: +1 408 543 0470
   EMail: markg@cacheflow.com


   Brad Cain
   Cereva Networks

   EMail: bcain@cereva.com


   Gary Tomlinson
   CacheFlow Inc.
   12034 134th Ct. NE
   Suite 201
   Redmond, WA  98052
   US

   Phone: +1 425 820 3009
   EMail: garyt@cacheflow.com


   Stephen Thomas
   TransNexus, Inc.
   430 Tenth Street NW
   Suite N204
   Atlanta, GA  30318
   US

   Phone: +1 404 872 4887
   EMail: stephen.thomas@transnexus.com


   Phil Rzewski
   Inktomi
   4100 East Third Avenue
   MS FC1-4
   Foster City, CA  94404
   US

   Phone: +1 650 653 2487
   EMail: philr@inktomi.com


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Internet-Draft              CDI Architecture               February 2002


Full Copyright Statement

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Acknowledgement

   Funding for the RFC editor function is currently provided by the
   Internet Society.



















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