<pre>Internet Engineering Task Force (IETF)                  B. Niven-Jenkins
Request for Comments: 8006                                     R. Murray
Category: Standards Track                                          Nokia
ISSN: 2070-1721                                             M. Caulfield
                                                           Cisco Systems
                                                                   K. Ma
                                                                Ericsson
                                                           December 2016


        <span class="h1">Content Delivery Network Interconnection (CDNI) Metadata</span>

Abstract

   The Content Delivery Network Interconnection (CDNI) Metadata
   interface enables interconnected Content Delivery Networks (CDNs) to
   exchange content distribution metadata in order to enable content
   acquisition and delivery.  The CDNI Metadata associated with a piece
   of content provides a downstream CDN with sufficient information for
   the downstream CDN to service content requests on behalf of an
   upstream CDN.  This document describes both a base set of CDNI
   Metadata and the protocol for exchanging that metadata.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in <a href="./rfc7841#section-2">Section&nbsp;2 of RFC 7841</a>.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   <a href="http://www.rfc-editor.org/info/rfc8006">http://www.rfc-editor.org/info/rfc8006</a>.















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Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.





































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Table of Contents

   <a href="#section-1">1</a>. Introduction ....................................................<a href="#page-5">5</a>
      <a href="#section-1.1">1.1</a>. Terminology ................................................<a href="#page-5">5</a>
      <a href="#section-1.2">1.2</a>. Supported Metadata Capabilities ............................<a href="#page-6">6</a>
   <a href="#section-2">2</a>. Design Principles ...............................................<a href="#page-7">7</a>
   <a href="#section-3">3</a>. CDNI Metadata Object Model ......................................<a href="#page-8">8</a>
      3.1. HostIndex, HostMatch, HostMetadata, PathMatch,
           PatternMatch, and PathMetadata Objects .....................<a href="#page-9">9</a>
      <a href="#section-3.2">3.2</a>. Generic CDNI Metadata Objects .............................<a href="#page-11">11</a>
      <a href="#section-3.3">3.3</a>. Metadata Inheritance and Override .........................<a href="#page-14">14</a>
   <a href="#section-4">4</a>. CDNI Metadata Objects ..........................................<a href="#page-15">15</a>
      <a href="#section-4.1">4.1</a>. Definitions of the CDNI Structural Metadata Objects .......<a href="#page-16">16</a>
           <a href="#section-4.1.1">4.1.1</a>. HostIndex ..........................................<a href="#page-16">16</a>
           <a href="#section-4.1.2">4.1.2</a>. HostMatch ..........................................<a href="#page-17">17</a>
           <a href="#section-4.1.3">4.1.3</a>. HostMetadata .......................................<a href="#page-18">18</a>
           <a href="#section-4.1.4">4.1.4</a>. PathMatch ..........................................<a href="#page-19">19</a>
           <a href="#section-4.1.5">4.1.5</a>. PatternMatch .......................................<a href="#page-20">20</a>
           <a href="#section-4.1.6">4.1.6</a>. PathMetadata .......................................<a href="#page-21">21</a>
           <a href="#section-4.1.7">4.1.7</a>. GenericMetadata ....................................<a href="#page-23">23</a>
      4.2. Definitions of the Initial Set of CDNI
           GenericMetadata Objects ...................................<a href="#page-24">24</a>
           <a href="#section-4.2.1">4.2.1</a>. SourceMetadata .....................................<a href="#page-24">24</a>
                  <a href="#section-4.2.1.1">4.2.1.1</a>. Source ....................................<a href="#page-25">25</a>
           <a href="#section-4.2.2">4.2.2</a>. LocationACL Metadata ...............................<a href="#page-26">26</a>
                  <a href="#section-4.2.2.1">4.2.2.1</a>. LocationRule ..............................<a href="#page-28">28</a>
                  <a href="#section-4.2.2.2">4.2.2.2</a>. Footprint .................................<a href="#page-29">29</a>
           <a href="#section-4.2.3">4.2.3</a>. TimeWindowACL ......................................<a href="#page-30">30</a>
                  <a href="#section-4.2.3.1">4.2.3.1</a>. TimeWindowRule ............................<a href="#page-31">31</a>
                  <a href="#section-4.2.3.2">4.2.3.2</a>. TimeWindow ................................<a href="#page-32">32</a>
           <a href="#section-4.2.4">4.2.4</a>. ProtocolACL Metadata ...............................<a href="#page-33">33</a>
                  <a href="#section-4.2.4.1">4.2.4.1</a>. ProtocolRule ..............................<a href="#page-34">34</a>
           <a href="#section-4.2.5">4.2.5</a>. DeliveryAuthorization Metadata .....................<a href="#page-35">35</a>
           <a href="#section-4.2.6">4.2.6</a>. Cache ..............................................<a href="#page-35">35</a>
           <a href="#section-4.2.7">4.2.7</a>. Auth ...............................................<a href="#page-37">37</a>
           <a href="#section-4.2.8">4.2.8</a>. Grouping ...........................................<a href="#page-38">38</a>
      <a href="#section-4.3">4.3</a>. CDNI Metadata Simple Data Type Descriptions ...............<a href="#page-39">39</a>
           <a href="#section-4.3.1">4.3.1</a>. Link ...............................................<a href="#page-39">39</a>
                  <a href="#section-4.3.1.1">4.3.1.1</a>. Link Loop Prevention ......................<a href="#page-40">40</a>
           <a href="#section-4.3.2">4.3.2</a>. Protocol ...........................................<a href="#page-40">40</a>
           <a href="#section-4.3.3">4.3.3</a>. Endpoint ...........................................<a href="#page-40">40</a>
           <a href="#section-4.3.4">4.3.4</a>. Time ...............................................<a href="#page-41">41</a>
           <a href="#section-4.3.5">4.3.5</a>. IPv4CIDR ...........................................<a href="#page-41">41</a>
           <a href="#section-4.3.6">4.3.6</a>. IPv6CIDR ...........................................<a href="#page-42">42</a>
           <a href="#section-4.3.7">4.3.7</a>. ASN ................................................<a href="#page-42">42</a>
           <a href="#section-4.3.8">4.3.8</a>. Country Code .......................................<a href="#page-42">42</a>
   <a href="#section-5">5</a>. CDNI Metadata Capabilities .....................................<a href="#page-42">42</a>




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   <a href="#section-6">6</a>. CDNI Metadata Interface ........................................<a href="#page-43">43</a>
      <a href="#section-6.1">6.1</a>. Transport .................................................<a href="#page-44">44</a>
      <a href="#section-6.2">6.2</a>. Retrieval of CDNI Metadata Resources ......................<a href="#page-44">44</a>
      <a href="#section-6.3">6.3</a>. Bootstrapping .............................................<a href="#page-45">45</a>
      <a href="#section-6.4">6.4</a>. Encoding ..................................................<a href="#page-46">46</a>
      <a href="#section-6.5">6.5</a>. Extensibility .............................................<a href="#page-46">46</a>
      <a href="#section-6.6">6.6</a>. Metadata Enforcement ......................................<a href="#page-47">47</a>
      <a href="#section-6.7">6.7</a>. Metadata Conflicts ........................................<a href="#page-47">47</a>
      <a href="#section-6.8">6.8</a>. Versioning ................................................<a href="#page-48">48</a>
      <a href="#section-6.9">6.9</a>. Media Types ...............................................<a href="#page-49">49</a>
      <a href="#section-6.10">6.10</a>. Complete CDNI Metadata Example ...........................<a href="#page-50">50</a>
   <a href="#section-7">7</a>. IANA Considerations ............................................<a href="#page-54">54</a>
      <a href="#section-7.1">7.1</a>. CDNI Payload Types ........................................<a href="#page-54">54</a>
           <a href="#section-7.1.1">7.1.1</a>. CDNI MI HostIndex Payload Type .....................<a href="#page-54">54</a>
           <a href="#section-7.1.2">7.1.2</a>. CDNI MI HostMatch Payload Type .....................<a href="#page-55">55</a>
           <a href="#section-7.1.3">7.1.3</a>. CDNI MI HostMetadata Payload Type ..................<a href="#page-55">55</a>
           <a href="#section-7.1.4">7.1.4</a>. CDNI MI PathMatch Payload Type .....................<a href="#page-55">55</a>
           <a href="#section-7.1.5">7.1.5</a>. CDNI MI PatternMatch Payload Type ..................<a href="#page-55">55</a>
           <a href="#section-7.1.6">7.1.6</a>. CDNI MI PathMetadata Payload Type ..................<a href="#page-55">55</a>
           <a href="#section-7.1.7">7.1.7</a>. CDNI MI SourceMetadata Payload Type ................<a href="#page-56">56</a>
           <a href="#section-7.1.8">7.1.8</a>. CDNI MI Source Payload Type ........................<a href="#page-56">56</a>
           <a href="#section-7.1.9">7.1.9</a>. CDNI MI LocationACL Payload Type ...................<a href="#page-56">56</a>
           <a href="#section-7.1.10">7.1.10</a>. CDNI MI LocationRule Payload Type .................<a href="#page-56">56</a>
           <a href="#section-7.1.11">7.1.11</a>. CDNI MI Footprint Payload Type ....................<a href="#page-56">56</a>
           <a href="#section-7.1.12">7.1.12</a>. CDNI MI TimeWindowACL Payload Type ................<a href="#page-57">57</a>
           <a href="#section-7.1.13">7.1.13</a>. CDNI MI TimeWindowRule Payload Type ...............<a href="#page-57">57</a>
           <a href="#section-7.1.14">7.1.14</a>. CDNI MI TimeWindow Payload Type ...................<a href="#page-57">57</a>
           <a href="#section-7.1.15">7.1.15</a>. CDNI MI ProtocolACL Payload Type ..................<a href="#page-57">57</a>
           <a href="#section-7.1.16">7.1.16</a>. CDNI MI ProtocolRule Payload Type .................<a href="#page-57">57</a>
           <a href="#section-7.1.17">7.1.17</a>. CDNI MI DeliveryAuthorization Payload Type ........<a href="#page-58">58</a>
           <a href="#section-7.1.18">7.1.18</a>. CDNI MI Cache Payload Type ........................<a href="#page-58">58</a>
           <a href="#section-7.1.19">7.1.19</a>. CDNI MI Auth Payload Type .........................<a href="#page-58">58</a>
           <a href="#section-7.1.20">7.1.20</a>. CDNI MI Grouping Payload Type .....................<a href="#page-58">58</a>
      <a href="#section-7.2">7.2</a>. "CDNI Metadata Footprint Types" Registry ..................<a href="#page-58">58</a>
      <a href="#section-7.3">7.3</a>. "CDNI Metadata Protocol Types" Registry ...................<a href="#page-59">59</a>
   <a href="#section-8">8</a>. Security Considerations ........................................<a href="#page-60">60</a>
      <a href="#section-8.1">8.1</a>. Authentication and Integrity ..............................<a href="#page-60">60</a>
      <a href="#section-8.2">8.2</a>. Confidentiality and Privacy ...............................<a href="#page-60">60</a>
      <a href="#section-8.3">8.3</a>. Securing the CDNI Metadata Interface ......................<a href="#page-61">61</a>
   <a href="#section-9">9</a>. References .....................................................<a href="#page-62">62</a>
      <a href="#section-9.1">9.1</a>. Normative References ......................................<a href="#page-62">62</a>
      <a href="#section-9.2">9.2</a>. Informative References ....................................<a href="#page-63">63</a>
   Acknowledgments ...................................................<a href="#page-65">65</a>
   Contributors ......................................................<a href="#page-65">65</a>
   Authors' Addresses ................................................<a href="#page-66">66</a>






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<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>.  Introduction</span>

   Content Delivery Network Interconnection (CDNI) [<a href="./rfc6707" title="&quot;Content Distribution Network Interconnection (CDNI) Problem Statement&quot;">RFC6707</a>] enables a
   downstream Content Delivery Network (dCDN) to service content
   requests on behalf of an upstream CDN (uCDN).

   The CDNI Metadata interface (MI) is discussed in [<a href="./rfc7336" title="&quot;Framework for Content Distribution Network Interconnection (CDNI)&quot;">RFC7336</a>] along with
   four other interfaces that can be used to compose a CDNI solution
   (the CDNI Control interface, the CDNI Request Routing Redirection
   interface, the CDNI Footprint &amp; Capabilities Advertisement interface
   (FCI), and the CDNI Logging interface).  [<a href="./rfc7336" title="&quot;Framework for Content Distribution Network Interconnection (CDNI)&quot;">RFC7336</a>] describes each
   interface and the relationships between them.  The requirements for
   the CDNI Metadata interface are specified in [<a href="./rfc7337" title="&quot;Content Distribution Network Interconnection (CDNI) Requirements&quot;">RFC7337</a>].

   The CDNI Metadata associated with a piece of content (or with a set
   of content) provides a dCDN with sufficient information for servicing
   content requests on behalf of a uCDN, in accordance with the policies
   defined by the uCDN.

   This document defines a CDNI Metadata interface that enables a dCDN
   to obtain CDNI Metadata from a uCDN so that the dCDN can properly
   process and respond to:

   o  Redirection requests received over the CDNI Request Routing
      Redirection interface [<a href="./rfc7975" title="&quot;Request Routing Redirection Interface for Content Delivery Network (CDN) Interconnection&quot;">RFC7975</a>].

   o  Content requests received directly from User Agents.

   Specifically, this document defines:

   o  A data structure for mapping content requests and redirection
      requests to CDNI Metadata objects (Sections <a href="#section-3">3</a> and <a href="#section-4.1">4.1</a>).

   o  An initial set of CDNI GenericMetadata objects (<a href="#section-4.2">Section 4.2</a>).

   o  An HTTP web service for the transfer of CDNI Metadata (<a href="#section-6">Section 6</a>).

<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a>.  Terminology</span>

   This document reuses the terminology defined in [<a href="./rfc6707" title="&quot;Content Distribution Network Interconnection (CDNI) Problem Statement&quot;">RFC6707</a>].

   Additionally, the following terms are used throughout this document
   and are defined as follows:

   o  Object - a collection of properties.

   o  Property - a key and value pair where the key is a property name
      and the value is the property value or another object.



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   This document uses the phrase "[Object] A contains [Object] B" for
   simplicity when a strictly accurate phrase would be "[Object] A
   contains or references (via a Link object) [Object] B".

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [<a href="./rfc2119" title="&quot;Key words for use in RFCs to Indicate Requirement Levels&quot;">RFC2119</a>].

<span class="h3"><a class="selflink" id="section-1.2" href="#section-1.2">1.2</a>.  Supported Metadata Capabilities</span>

   Only the metadata for a small set of initial capabilities is
   specified in this document.  This set provides the minimum amount of
   metadata for basic CDN interoperability while still meeting the
   requirements set forth by [<a href="./rfc7337" title="&quot;Content Distribution Network Interconnection (CDNI) Requirements&quot;">RFC7337</a>].

   The following high-level functionality can be configured via the CDNI
   Metadata objects specified in <a href="#section-4">Section 4</a>:

   o  Acquisition Source: Metadata for allowing a dCDN to fetch content
      from a uCDN.

   o  Delivery Access Control: Metadata for restricting (or permitting)
      access to content based on any of the following factors:

      *  Location

      *  Time window

      *  Delivery protocol

   o  Delivery Authorization: Metadata for authorizing dCDN User Agent
      requests.

   o  Cache Control: Metadata for controlling cache behavior of
      the dCDN.

   The metadata encoding described by this document is extensible in
   order to allow for future additions to this list.

   The set of metadata specified in this document covers the initial
   capabilities above.  It is only intended to support CDNI for the
   delivery of content by a dCDN using HTTP/1.1 [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>] and for a dCDN
   to be able to acquire content from a uCDN using either HTTP/1.1 or
   HTTP/1.1 over Transport Layer Security (TLS) [<a href="./rfc2818" title="&quot;HTTP Over TLS&quot;">RFC2818</a>].







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   Supporting CDNI for the delivery of content using unencrypted HTTP/2
   [<a href="./rfc7540" title="&quot;Hypertext Transfer Protocol Version 2 (HTTP/2)&quot;">RFC7540</a>] (as well as for a dCDN to acquire content using unencrypted
   HTTP/2 or HTTP/2 over TLS) requires the registration of these
   protocol names in the "CDNI Metadata Protocol Types" registry
   (<a href="#section-7.3">Section 7.3</a>).

   Delivery of content using HTTP/1.1 over TLS or HTTP/2 over TLS SHOULD
   follow the guidelines set forth in [<a href="./rfc7525" title="&quot;Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)&quot;">RFC7525</a>].  Offline configuration
   of TLS parameters between CDNs is beyond the scope of this document.

<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>.  Design Principles</span>

   The CDNI Metadata interface was designed to achieve the following
   objectives:

   1.  Cacheability of CDNI Metadata objects;

   2.  Deterministic mapping from redirection requests and content
       requests to CDNI Metadata properties;

   3.  Support for DNS redirection as well as application-specific
       redirection (for example, HTTP redirection);

   4.  Minimal duplication of CDNI Metadata; and

   5.  Leveraging of existing protocols.

   Cacheability can decrease the latency of acquiring metadata while
   maintaining its freshness and can therefore decrease the latency of
   serving content requests and redirection requests, without
   sacrificing accuracy.  The CDNI Metadata interface uses HTTP and its
   existing caching mechanisms to achieve CDNI Metadata cacheability.

   Deterministic mapping from content to metadata properties eliminates
   ambiguity and ensures that policies are applied consistently by all
   dCDNs.

   Support for both HTTP and DNS redirection ensures that the CDNI
   Metadata meets the same design principles for both HTTP-based and
   DNS-based redirection schemes.

   Minimal duplication of CDNI Metadata improves storage efficiency in
   the CDNs.

   Leveraging existing protocols avoids reinventing common mechanisms
   such as data structure encoding (by leveraging I-JSON (Internet JSON)
   [<a href="./rfc7493" title="&quot;The I-JSON Message Format&quot;">RFC7493</a>]) and data transport (by leveraging HTTP [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>]).




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<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>.  CDNI Metadata Object Model</span>

   The CDNI Metadata object model describes a data structure for mapping
   redirection requests and content requests to metadata properties.
   Metadata properties describe how to acquire content from a uCDN,
   authorize access to content, and deliver content from a dCDN.  The
   object model relies on the assumption that these metadata properties
   can be grouped based on the hostname of the content and subsequently
   on the resource path (URI) of the content.  The object model
   associates a set of CDNI Metadata properties with a hostname to form
   a default set of metadata properties for content delivered on behalf
   of that hostname.  That default set of metadata properties can be
   overridden by properties that apply to specific paths within a URI.

   Different hostnames and URI paths will be associated with different
   sets of CDNI Metadata properties in order to describe the required
   behavior when a dCDN Surrogate or request router is processing User
   Agent requests for content at that hostname and URI path.  As a
   result of this structure, significant commonality could exist between
   the CDNI Metadata properties specified for different hostnames,
   different URI paths within a hostname, and different URI paths on
   different hostnames.  For example, the definition of which User Agent
   IP addresses should be grouped together into a single network or
   geographic location is likely to be common for a number of different
   hostnames; although a uCDN is likely to have several different
   policies configured to express geo-blocking rules, it is likely that
   a single geo-blocking policy could be applied to multiple hostnames
   delivered through the CDN.

   In order to enable the CDNI Metadata for a given hostname and URI
   path to be decomposed into reusable sets of CDNI Metadata properties,
   the CDNI Metadata interface splits the CDNI Metadata into separate
   objects.  Efficiency is improved by enabling a single CDNI Metadata
   object (that is shared across hostnames and/or URI paths) to be
   retrieved and stored by a dCDN once, even if it is referenced by the
   CDNI Metadata for multiple hostnames and/or URI paths.

   Important Note: Any CDNI Metadata object A that contains another CDNI
   Metadata object B can include a Link object specifying a URI that can
   be used to retrieve object B, instead of embedding object B within
   object A.  The remainder of this document uses the phrase "[Object] A
   contains [Object] B" for simplicity when a strictly accurate phrase
   would be "[Object] A contains or references (via a Link object)
   [Object] B".  It is generally a deployment choice for the uCDN
   implementation to decide when to embed CDNI Metadata objects and when
   to reference separate resources via Link objects.





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   <a href="#section-3.1">Section 3.1</a> introduces a high-level description of the HostIndex,
   HostMatch, HostMetadata, PathMatch, PatternMatch, and PathMetadata
   objects, and describes the relationships between them.

   <a href="#section-3.2">Section 3.2</a> introduces a high-level description of the CDNI
   GenericMetadata object, which represents the level at which CDNI
   Metadata override occurs between HostMetadata and PathMetadata
   objects.

   <a href="#section-4">Section 4</a> describes in detail the specific CDNI Metadata objects and
   properties specified by this document that can be contained within a
   CDNI GenericMetadata object.

<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>.  HostIndex, HostMatch, HostMetadata, PathMatch, PatternMatch, and</span>
<span class="h3">      PathMetadata Objects</span>

   The relationships between the HostIndex, HostMatch, HostMetadata,
   PathMatch, PatternMatch, and PathMetadata objects are described in
   Figure 1.

   +---------+      +---------+      +------------+
   |HostIndex+-(*)-&gt;|HostMatch+-(1)-&gt;|HostMetadata+-------(*)------+
   +---------+      +---------+      +------+-----+                |
                                            |                      |
                                           (*)                     |
                                            |                      V
   --&gt; Contains or references               V         *****************
   (1) One and only one                +---------+    *GenericMetadata*
   (*) Zero or more               +---&gt;|PathMatch|    *     Objects   *
                                  |    +----+---++    *****************
                                  |         |   |                  ^
                                 (*)       (1) (1) +------------+  |
                                  |         |   +-&gt;|PatternMatch|  |
                                  |         V      +------------+  |
                                  |  +------------+                |
                                  +--+PathMetadata+-------(*)------+
                                     +------------+

           Figure 1: Relationships between CDNI Metadata Objects
                         (Diagram Representation)

   A HostIndex object (see <a href="#section-4.1.1">Section 4.1.1</a>) contains an array of HostMatch
   objects (see <a href="#section-4.1.2">Section 4.1.2</a>) that contain hostnames (and/or IP
   addresses) for which content requests might be delegated to the dCDN.
   The HostIndex is the starting point for accessing the uCDN CDNI
   Metadata data store.  It enables the dCDN to deterministically
   discover which CDNI Metadata objects it requires in order to deliver
   a given piece of content.



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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-10" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   The HostIndex links hostnames (and/or IP addresses) to HostMetadata
   objects (see <a href="#section-4.1.3">Section 4.1.3</a>) via HostMatch objects.  A HostMatch
   object defines a hostname (or IP address) to match against a
   requested host and contains a HostMetadata object.

   HostMetadata objects contain the default GenericMetadata objects (see
   <a href="#section-4.1.7">Section 4.1.7</a>) required to serve content for that host.  When looking
   up CDNI Metadata, the dCDN looks up the requested hostname (or IP
   address) against the HostMatch entries in the HostIndex; from there,
   it can find HostMetadata, which describes the default metadata
   properties for each host as well as PathMetadata objects (see
   <a href="#section-4.1.6">Section 4.1.6</a>), via PathMatch objects (see <a href="#section-4.1.4">Section 4.1.4</a>).  PathMatch
   objects define patterns, contained inside PatternMatch objects (see
   <a href="#section-4.1.5">Section 4.1.5</a>), to match against the requested URI path.
   PatternMatch objects contain the pattern strings and flags that
   describe the URI path to which a PathMatch applies.  PathMetadata
   objects contain the GenericMetadata objects that apply to content
   requests matching the defined URI path pattern.  PathMetadata
   properties override properties previously defined in HostMetadata or
   less-specific PathMatch paths.  PathMetadata objects can contain
   additional PathMatch objects to recursively define more-specific URI
   paths to which GenericMetadata properties might be applied.

   A GenericMetadata object contains individual CDNI Metadata objects
   that define the specific policies and attributes needed to properly
   deliver the associated content.  For example, a GenericMetadata
   object could describe the source from which a CDN can acquire a piece
   of content.  The GenericMetadata object is an atomic unit that can be
   referenced by HostMetadata or PathMetadata objects.

   For example, if "example.com" is a content provider, a HostMatch
   object could include an entry for "example.com" with the URI of the
   associated HostMetadata object.  The HostMetadata object for
   "example.com" describes the metadata properties that apply to
   "example.com" and could contain PathMatches for
   "example.com/movies/*" and "example.com/music/*", which in turn
   reference corresponding PathMetadata objects that contain the
   properties for those more-specific URI paths.  The PathMetadata
   object for "example.com/movies/*" describes the properties that apply
   to that URI path.  It could also contain a PathMatch object for
   "example.com/movies/hd/*", which would reference the corresponding
   PathMetadata object for the "example.com/movies/hd/" path prefix.









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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-11" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   The relationships in Figure 1 are also represented in tabular format
   in Table 1 below.

   +--------------+----------------------------------------------------+
   | Data Object  | Objects it contains or references                  |
   +--------------+----------------------------------------------------+
   | HostIndex    | 0 or more HostMatch objects.                       |
   |              |                                                    |
   | HostMatch    | 1 HostMetadata object.                             |
   |              |                                                    |
   | HostMetadata | 0 or more PathMatch objects.  0 or more            |
   |              | GenericMetadata objects.                           |
   |              |                                                    |
   | PathMatch    | 1 PatternMatch object.  1 PathMetadata object.     |
   |              |                                                    |
   | PatternMatch | Does not contain or reference any other objects.   |
   |              |                                                    |
   | PathMetadata | 0 or more PathMatch objects.  0 or more            |
   |              | GenericMetadata objects.                           |
   +--------------+----------------------------------------------------+

           Table 1: Relationships between CDNI Metadata Objects
                          (Table Representation)

<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>.  Generic CDNI Metadata Objects</span>

   The HostMetadata and PathMetadata objects contain other CDNI Metadata
   objects that contain properties that describe how User Agent requests
   for content should be processed -- for example, where to acquire the
   content from, authorization rules that should be applied,
   geo-blocking restrictions, and so on.  Each such CDNI Metadata object
   is a specialization of a CDNI GenericMetadata object.  The
   GenericMetadata object abstracts the basic information required for
   metadata override and metadata distribution, from the specifics of
   any given property (i.e., property semantics, enforcement options,
   etc.).

   The GenericMetadata object defines the properties contained within it
   as well as whether or not the properties are "mandatory-to-enforce".
   If the dCDN does not understand or support a mandatory-to-enforce
   property, the dCDN MUST NOT serve the content.  If the property is
   not mandatory-to-enforce, then that GenericMetadata object can be
   safely ignored and the content request can be processed in accordance
   with the rest of the CDNI Metadata.







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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-12" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   Although a CDN MUST NOT serve content to a User Agent if a
   mandatory-to-enforce property cannot be enforced, it could still be
   safe to redistribute that metadata (the "safe-to-redistribute"
   property) to another CDN without modification.  For example, in the
   cascaded CDN case, a transit CDN (tCDN) could convey
   mandatory-to-enforce metadata to a dCDN.  For metadata that does not
   require customization or translation (i.e., metadata that is
   safe-to-redistribute), the data representation received off the wire
   MAY be stored and redistributed without being understood or supported
   by the tCDN.  However, for metadata that requires translation,
   transparent redistribution of the uCDN metadata values might not be
   appropriate.  Certain metadata can be safely, though perhaps not
   optimally, redistributed unmodified.  For example, a source
   acquisition address might not be optimal if transparently
   redistributed, but it might still work.

   Redistribution safety MUST be specified for each GenericMetadata
   property.  If a CDN does not understand or support a given
   GenericMetadata property that is not safe-to-redistribute, the CDN
   MUST set the "incomprehensible" flag to true for that GenericMetadata
   object before redistributing the metadata.  The "incomprehensible"
   flag signals to a dCDN that the metadata was not properly transformed
   by the tCDN.  A CDN MUST NOT attempt to use metadata that has been
   marked as "incomprehensible" by a uCDN.

   tCDNs MUST NOT change the value of mandatory-to-enforce or
   safe-to-redistribute when propagating metadata to a dCDN.  Although a
   tCDN can set the value of "incomprehensible" to true, a tCDN MUST NOT
   change the value of "incomprehensible" from true to false.






















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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-13" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   Table 2 describes the action to be taken by a tCDN for the different
   combinations of mandatory-to-enforce ("MtE") and safe-to-redistribute
   ("StR") properties when the tCDN either does or does not understand
   the metadata in question:

   +-------+-------+------------+--------------------------------------+
   | MtE   | StR   | Metadata   | Action                               |
   |       |       | Understood |                                      |
   |       |       | by tCDN    |                                      |
   +-------+-------+------------+--------------------------------------+
   | False | True  | True       | Can serve and redistribute.          |
   |       |       |            |                                      |
   | False | True  | False      | Can serve and redistribute.          |
   |       |       |            |                                      |
   | False | False | False      | Can serve.  MUST set                 |
   |       |       |            | "incomprehensible" to true when      |
   |       |       |            | redistributing.                      |
   |       |       |            |                                      |
   | False | False | True       | Can serve.  Can redistribute after   |
   |       |       |            | transforming the metadata (if the    |
   |       |       |            | CDN knows how to do so safely);      |
   |       |       |            | otherwise, MUST set                  |
   |       |       |            | "incomprehensible" to true when      |
   |       |       |            | redistributing.                      |
   |       |       |            |                                      |
   | True  | True  | True       | Can serve and redistribute.          |
   |       |       |            |                                      |
   | True  | True  | False      | MUST NOT serve but can redistribute. |
   |       |       |            |                                      |
   | True  | False | True       | Can serve.  Can redistribute after   |
   |       |       |            | transforming the metadata (if the    |
   |       |       |            | CDN knows how to do so safely);      |
   |       |       |            | otherwise, MUST set                  |
   |       |       |            | "incomprehensible" to true when      |
   |       |       |            | redistributing.                      |
   |       |       |            |                                      |
   | True  | False | False      | MUST NOT serve.  MUST set            |
   |       |       |            | "incomprehensible" to true when      |
   |       |       |            | redistributing.                      |
   +-------+-------+------------+--------------------------------------+

               Table 2: Action to Be Taken by a tCDN for the
             Different Combinations of MtE and StR Properties








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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-14" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   Table 3 describes the action to be taken by a dCDN for the different
   combinations of mandatory-to-enforce and "incomprehensible" (Incomp)
   properties, when the dCDN either does or does not understand the
   metadata in question:

   +-------+--------+--------------+-----------------------------------+
   | MtE   | Incomp | Metadata     | Action                            |
   |       |        | Understood   |                                   |
   |       |        | by dCDN      |                                   |
   +-------+--------+--------------+-----------------------------------+
   | False | False  | True         | Can serve.                        |
   |       |        |              |                                   |
   | False | True   | True         | Can serve but MUST NOT            |
   |       |        |              | interpret/apply any metadata      |
   |       |        |              | marked as "incomprehensible".     |
   |       |        |              |                                   |
   | False | False  | False        | Can serve.                        |
   |       |        |              |                                   |
   | False | True   | False        | Can serve but MUST NOT            |
   |       |        |              | interpret/apply any metadata      |
   |       |        |              | marked as "incomprehensible".     |
   |       |        |              |                                   |
   | True  | False  | True         | Can serve.                        |
   |       |        |              |                                   |
   | True  | True   | True         | MUST NOT serve.                   |
   |       |        |              |                                   |
   | True  | False  | False        | MUST NOT serve.                   |
   |       |        |              |                                   |
   | True  | True   | False        | MUST NOT serve.                   |
   +-------+--------+--------------+-----------------------------------+

               Table 3: Action to Be Taken by a dCDN for the
            Different Combinations of MtE and Incomp Properties

<span class="h3"><a class="selflink" id="section-3.3" href="#section-3.3">3.3</a>.  Metadata Inheritance and Override</span>

   In the metadata object model, a HostMetadata object can contain
   multiple PathMetadata objects (via PathMatch objects).  Each
   PathMetadata object can in turn contain other PathMetadata objects.
   HostMetadata and PathMetadata objects form an inheritance tree where
   each node in the tree inherits or overrides the property values set
   by its parent.

   GenericMetadata objects of a given type override all GenericMetadata
   objects of the same type previously defined by any parent object in
   the tree.  GenericMetadata objects of a given type previously defined
   by a parent object in the tree are inherited when no object of the
   same type is defined by the child object.  For example, if



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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-15" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   HostMetadata for the host "example.com" contains GenericMetadata
   objects of types LocationACL and TimeWindowACL (where "ACL" means
   "Access Control List") while a PathMetadata object that applies to
   "example.com/movies/*" defines an alternate GenericMetadata object of
   type TimeWindowACL, then:

   o  The TimeWindowACL defined in the PathMetadata would override the
      TimeWindowACL defined in the HostMetadata for all User Agent
      requests for content under "example.com/movies/", and

   o  The LocationACL defined in the HostMetadata would be inherited for
      all User Agent requests for content under "example.com/movies/".

   A single HostMetadata or PathMetadata object MUST NOT contain
   multiple GenericMetadata objects of the same type.  If an array of
   GenericMetadata contains objects of duplicate types, the receiver
   MUST ignore all but the first object of each type.

<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>.  CDNI Metadata Objects</span>

   <a href="#section-4.1">Section 4.1</a> provides the definitions of each metadata object type
   introduced in <a href="#section-3">Section 3</a>.  These metadata objects are described as
   structural metadata objects, as they provide the structure for host
   and URI path-based inheritance and identify which GenericMetadata
   objects apply to a given User Agent content request.

   <a href="#section-4.2">Section 4.2</a> provides the definitions for a base set of core metadata
   objects that can be contained within a GenericMetadata object.  These
   metadata objects govern how User Agent requests for content are
   handled.  GenericMetadata objects can contain other GenericMetadata
   objects as properties; these can be referred to as sub-objects.  As
   with all CDNI Metadata objects, the value of the GenericMetadata
   sub-objects can be either a complete serialized representation of the
   sub-object or a Link object that contains a URI that can be
   dereferenced to retrieve the complete serialized representation of
   the property sub-object.

   <a href="#section-6.5">Section 6.5</a> discusses the ability to extend the base set of
   GenericMetadata objects specified in this document with additional
   standards-based or vendor-specific GenericMetadata objects that might
   be defined in the future in separate documents.

   dCDNs and tCDNs MUST support the parsing of all CDNI Metadata objects
   specified in this document.  A dCDN does not have to implement the
   underlying functionality represented by non-structural
   GenericMetadata objects (though that might restrict the content that
   a given dCDN will be able to serve).  uCDNs as generators of CDNI
   Metadata only need to support generating the CDNI Metadata that they



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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-16" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   need in order to express the policies required by the content they
   are describing.  See <a href="#section-6.4">Section 6.4</a> for more details on the specific
   encoding rules for CDNI Metadata objects.

   Note: In the following sections, the term "mandatory-to-specify" is
   used to convey which properties MUST be included for a given
   structural or GenericMetadata object.  When mandatory-to-specify is
   specified as "Yes" for an individual property, it means that if the
   object containing that property is included in a metadata response,
   then the mandatory-to-specify property MUST also be included
   (directly or by reference) in the response.  For example, a HostMatch
   property object without a host to match against does not make sense;
   therefore, the "host" property is mandatory-to-specify inside a
   HostMatch object.

<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>.  Definitions of the CDNI Structural Metadata Objects</span>

   The subsections below describe the structural objects introduced in
   <a href="#section-3.1">Section 3.1</a>.

<span class="h4"><a class="selflink" id="section-4.1.1" href="#section-4.1.1">4.1.1</a>.  HostIndex</span>

   The HostIndex object is the entry point into the CDNI Metadata
   hierarchy.  It contains an array of HostMatch objects.  An incoming
   content request is checked against the hostname (or IP address)
   specified by each of the listed HostMatch objects to find the
   HostMatch object that applies to the request.

      Property: hosts

         Description: Array of HostMatch objects.  Hosts (HostMatch
         objects) MUST be evaluated in the order they appear, and the
         first HostMatch object that matches the content request being
         processed MUST be used.

         Type: Array of HostMatch objects

         Mandatory-to-Specify: Yes.













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<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-17" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


   Example HostIndex object containing two HostMatch objects, where the
   first HostMatch object is embedded and the second HostMatch object is
   referenced:

   {
     "hosts": [
       {
         &lt;Properties of embedded HostMatch object&gt;
       },
       {
         "type": "MI.HostMatch",
         "href": "<a href="https://metadata.ucdn.example/hostmatch1234">https://metadata.ucdn.example/hostmatch1234</a>"
       }
     ]
   }

<span class="h4"><a class="selflink" id="section-4.1.2" href="#section-4.1.2">4.1.2</a>.  HostMatch</span>

   The HostMatch object contains a hostname or IP address to match
   against content requests.  The HostMatch object also contains a
   HostMetadata object to apply if a match is found.

      Property: host

         Description: Hostname or IP address and optional port to match
         against the requested host, i.e., the host and port as
         described in [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>].  In order for a hostname or IP address
         in a content request to match the hostname or IP address in the
         "host" property, the value from the content request when
         converted to lowercase MUST be identical to the value of the
         "host" property when converted to lowercase.  All
         implementations MUST support IPv4 addresses encoded as
         specified by the "IPv4address" rule in <a href="./rfc3986#section-3.2.2">Section&nbsp;3.2.2 of
         [RFC3986]</a>.  IPv6 addresses MUST be encoded in one of the IPv6
         address formats specified in [<a href="./rfc5952" title="&quot;A Recommendation for IPv6 Address Text Representation&quot;">RFC5952</a>], although receivers MUST
         support all IPv6 address formats specified in [<a href="./rfc4291" title="&quot;IP Version 6 Addressing Architecture&quot;">RFC4291</a>].
         Hostnames MUST conform to the Domain Name System (DNS) syntax
         defined in [<a href="./rfc1034" title="&quot;Domain names - concepts and facilities&quot;">RFC1034</a>] and [<a href="./rfc1123" title="&quot;Requirements for Internet Hosts - Application and Support&quot;">RFC1123</a>].  Internationalized Domain
         Names (IDNs) must first be transformed to the A-label form
         [<a href="./rfc5890" title="&quot;Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework&quot;">RFC5890</a>] as per [<a href="./rfc5891" title="&quot;Internationalized Domain Names in Applications (IDNA): Protocol&quot;">RFC5891</a>].

         Type: Endpoint

         Mandatory-to-Specify: Yes.







<span class="grey">Niven-Jenkins, et al.        Standards Track                   [Page 17]</span></pre>
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<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


      Property: host-metadata

         Description: CDNI Metadata to apply when delivering content
         that matches this host.

         Type: HostMetadata

         Mandatory-to-Specify: Yes.

   Example HostMatch object with an embedded HostMetadata object:

   {
     "host": "video.example.com",
     "host-metadata": {
       &lt;Properties of embedded HostMetadata object&gt;
     }
   }

   Example HostMatch object referencing (via a Link object; see
   <a href="#section-4.3.1">Section 4.3.1</a>) a HostMetadata object:

   {
     "host": "video.example.com",
     "host-metadata": {
       "type": "MI.HostMetadata",
       "href": "<a href="https://metadata.ucdn.example/host1234">https://metadata.ucdn.example/host1234</a>"
     }
   }

<span class="h4"><a class="selflink" id="section-4.1.3" href="#section-4.1.3">4.1.3</a>.  HostMetadata</span>

   A HostMetadata object contains the CDNI Metadata properties for
   content served for a particular host (defined in the HostMatch
   object) and possibly child PathMatch objects.

      Property: metadata

         Description: Array of host-related metadata.

         Type: Array of GenericMetadata objects

         Mandatory-to-Specify: Yes.









<span class="grey">Niven-Jenkins, et al.        Standards Track                   [Page 18]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-19" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


      Property: paths

         Description: Path-specific rules.  Path patterns (PathMatch
         objects) MUST be evaluated in the order they appear, and the
         first (and only the first) PathMatch object that matches the
         content request being processed MUST be used.

         Type: Array of PathMatch objects

         Mandatory-to-Specify: No.  Default is that there are no
         more-specific paths to evaluate (i.e., an empty list).

   Example HostMetadata object containing a number of embedded
   GenericMetadata objects that will describe the default metadata for
   the host and an embedded PathMatch object that contains a path for
   which metadata exists that overrides the default metadata for the
   host:

   {
     "metadata": [
       {
         &lt;Properties of first embedded GenericMetadata object&gt;
       },
       {
         &lt;Properties of second embedded GenericMetadata object&gt;
       },

    ...

       {
         &lt;Properties of Nth embedded GenericMetadata object&gt;
       }
     ],
     "paths": [
       {
         &lt;Properties of embedded PathMatch object&gt;
       }
     ]
   }

<span class="h4"><a class="selflink" id="section-4.1.4" href="#section-4.1.4">4.1.4</a>.  PathMatch</span>

   A PathMatch object contains a PatternMatch object with a path to
   match against a resource's URI path, as well as how to handle URI
   query parameters.  The PathMatch object also contains a PathMetadata
   object with GenericMetadata to apply if the resource's URI matches
   the pattern within the PatternMatch object.




<span class="grey">Niven-Jenkins, et al.        Standards Track                   [Page 19]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-20" ></span>
<span class="grey"><a href="./rfc8006">RFC 8006</a>              CDN Interconnection Metadata         December 2016</span>


      Property: path-pattern

         Description: Pattern to match against the requested
         resource's URI.

         Type: PatternMatch

         Mandatory-to-Specify: Yes.

      Property: path-metadata

         Description: CDNI Metadata to apply when delivering content
         that matches the associated PatternMatch.

         Type: PathMetadata

         Mandatory-to-Specify: Yes.

   Example PathMatch object referencing the PathMetadata object to use
   for URIs that match the case-sensitive URI path pattern "/movies/*"
   (contained within an embedded PatternMatch object):

   {
     "path-pattern": {
       "pattern": "/movies/*",
       "case-sensitive": true
     },
     "path-metadata": {
         "type": "MI.PathMetadata",
         "href": "<a href="https://metadata.ucdn.example/host1234/pathDCE">https://metadata.ucdn.example/host1234/pathDCE</a>"
     }
   }

<span class="h4"><a class="selflink" id="section-4.1.5" href="#section-4.1.5">4.1.5</a>.  PatternMatch</span>

   A PatternMatch object contains the pattern string and flags that
   describe the pattern expression.

      Property: pattern

         Description: A pattern for matching against the URI path, i.e.,
         against the path-absolute [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>].  The pattern can contain
         the wildcards "*" and "?", where "*" matches any sequence of
         pchar [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>] or "/" characters (including the empty string)
         and "?" matches exactly one pchar character.  The three
         literals "$", "*", and "?"  MUST be escaped as "$$", "$*", and
         "$?" (where "$" is the designated escape character).  All other
         characters are treated as literals.



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         Type: String

         Mandatory-to-Specify: Yes.

      Property: case-sensitive

         Description: Flag indicating whether or not case-sensitive
         matching should be used.  Note: Case insensitivity applies to
         ALPHA characters in the URI path prior to percent-decoding
         [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>].

         Type: Boolean

         Mandatory-to-Specify: No.  Default is case-insensitive match
         (i.e., a value of False).

   Example PatternMatch object that matches the case-sensitive URI path
   pattern "/movies/*":

   {
     "pattern": "/movies/*",
     "case-sensitive": true
   }

<span class="h4"><a class="selflink" id="section-4.1.6" href="#section-4.1.6">4.1.6</a>.  PathMetadata</span>

   A PathMetadata object contains the CDNI Metadata properties for
   content requests that match against the associated URI path (defined
   in a PathMatch object).

   Note that if DNS-based redirection is employed, then a dCDN will be
   unable to evaluate any metadata at the PathMetadata level or below
   because only the hostname of the content request is available at
   Request Routing time.  dCDNs SHOULD still process all PathMetadata
   for the host before responding to the redirection request to detect
   if any unsupported metadata is specified.  If any metadata not
   supported by the dCDN is marked as mandatory-to-enforce, the dCDN
   SHOULD NOT accept the content redirection request, in order to avoid
   receiving content requests that it will not be able to satisfy/serve.

      Property: metadata

         Description: Array of path-related metadata.

         Type: Array of GenericMetadata objects

         Mandatory-to-Specify: Yes.




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      Property: paths

         Description: Path-specific rules.  Path patterns (PathMatch
         objects) MUST be evaluated in the order they appear, and the
         first (and only the first) PathMatch object that matches the
         content request being processed MUST be used.

         Type: Array of PathMatch objects

         Mandatory-to-Specify: No.  Default is that there are no
         more-specific paths to evaluate (i.e., an empty list).

   Example PathMetadata object containing a number of embedded
   GenericMetadata objects that describe the metadata to apply for the
   URI path defined in the parent PathMatch object, as well as a
   more-specific PathMatch object.

   {
     "metadata": [
       {
         &lt;Properties of first embedded GenericMetadata object&gt;
       },
       {
         &lt;Properties of second embedded GenericMetadata object&gt;
       },

    ...

       {
         &lt;Properties of Nth embedded GenericMetadata object&gt;
       }
     ],
     "paths": [
       {
         &lt;Properties of embedded PathMatch object&gt;
       }
     ]
   }













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<span class="h4"><a class="selflink" id="section-4.1.7" href="#section-4.1.7">4.1.7</a>.  GenericMetadata</span>

   A GenericMetadata object is a wrapper for managing individual CDNI
   Metadata properties in an opaque manner.

      Property: generic-metadata-type

         Description: Case-insensitive CDNI Metadata object type.

         Type: String containing the CDNI Payload Type [<a href="./rfc7736" title="&quot;Content Delivery Network Interconnection (CDNI) Media Type Registration&quot;">RFC7736</a>] of the
         object contained in the generic-metadata-value property (see
         Table 4).

         Mandatory-to-Specify: Yes.

      Property: generic-metadata-value

         Description: CDNI Metadata object.

         Type: Format/Type is defined by the value of the
         generic-metadata-type property above.
         Note: generic-metadata-values MUST NOT name any properties
         "href" (see <a href="#section-4.3.1">Section 4.3.1</a>).

         Mandatory-to-Specify: Yes.

      Property: mandatory-to-enforce

         Description: Flag identifying whether or not the enforcement of
         the property metadata is required.

         Type: Boolean

         Mandatory-to-Specify: No.  Default is to treat metadata as
         mandatory-to-enforce (i.e., a value of True).

      Property: safe-to-redistribute

         Description: Flag identifying whether or not the property
         metadata can be safely redistributed without modification.

         Type: Boolean

         Mandatory-to-Specify: No.  Default is to allow transparent
         redistribution (i.e., a value of True).






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      Property: incomprehensible

         Description: Flag identifying whether or not any CDN in the
         chain of delegation has failed to understand and/or failed to
         properly transform this metadata object.  Note: This flag only
         applies to metadata objects whose safe-to-redistribute property
         has a value of False.

         Type: Boolean

         Mandatory-to-Specify: No.  Default is comprehensible (i.e., a
         value of False).

   Example GenericMetadata object containing a metadata object that
   applies to the applicable URI path and/or host (within a parent
   PathMetadata and/or HostMetadata object, respectively):

 {
   "mandatory-to-enforce": true,
   "safe-to-redistribute": true,
   "incomprehensible": false,
   "generic-metadata-type": &lt;CDNI Payload Type of this metadata object&gt;,
   "generic-metadata-value":
     {
       &lt;Properties of this metadata object&gt;
     }
 }

<span class="h3"><a class="selflink" id="section-4.2" href="#section-4.2">4.2</a>.  Definitions of the Initial Set of CDNI GenericMetadata Objects</span>

   The objects defined below are intended to be used in the
   GenericMetadata object's generic-metadata-value field as defined in
   <a href="#section-4.1.7">Section 4.1.7</a>, and their generic-metadata-type property MUST be set
   to the appropriate CDNI Payload Type as defined in Table 4.

<span class="h4"><a class="selflink" id="section-4.2.1" href="#section-4.2.1">4.2.1</a>.  SourceMetadata</span>

   Source metadata provides the dCDN with information about content
   acquisition, i.e., how to contact a uCDN Surrogate or an origin
   server to obtain the content to be served.  The sources are not
   necessarily the actual origin servers operated by the Content Service
   Provider (CSP) but might be a set of Surrogates in the uCDN.

      Property: sources

         Description: Sources from which the dCDN can acquire content,
         listed in order of preference.




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         Type: Array of Source objects (see <a href="#section-4.2.1.1">Section 4.2.1.1</a>)

         Mandatory-to-Specify: No.  Default is to use static
         configuration, out-of-band from the CDNI Metadata interface.

   Example SourceMetadata object (which contains two Source objects)
   that describes which servers the dCDN should use for acquiring
   content for the applicable URI path and/or host:

   {
     "generic-metadata-type": "MI.SourceMetadata",
     "generic-metadata-value":
       {
         "sources": [
           {
             "endpoints": [
               "a.service123.ucdn.example",
               "b.service123.ucdn.example"
               ],
             "protocol": "http/1.1"
           },
           {
             "endpoints": ["origin.service123.example"],
             "protocol": "http/1.1"
           }
         ]
       }
   }

<span class="h5"><a class="selflink" id="section-4.2.1.1" href="#section-4.2.1.1">4.2.1.1</a>.  Source</span>

   A Source object describes the source to be used by the dCDN for
   content acquisition (e.g., a Surrogate within the uCDN or an
   alternate origin server), the protocol to be used, and any
   authentication method to be used when contacting that source.

   Endpoints within a Source object MUST be treated as equivalent/equal.
   A uCDN can specify an array of sources, ordered by preference, within
   a SourceMetadata object.  Then, for each Source object ranked by
   preference, a uCDN can specify an array of endpoints that are
   equivalent (e.g., a pool of servers that are not behind a load
   balancer).

      Property: acquisition-auth

         Description: Authentication method to use when requesting
         content from this source.




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         Type: Auth (see <a href="#section-4.2.7">Section 4.2.7</a>)

         Mandatory-to-Specify: No.  Default is no authentication
         required.

      Property: endpoints

         Description: Origins from which the dCDN can acquire content.
         If multiple endpoints are specified, they are all equal, i.e.,
         the list is not ordered by preference.

         Type: Array of Endpoint objects (see <a href="#section-4.3.3">Section 4.3.3</a>)

         Mandatory-to-Specify: Yes.

      Property: protocol

         Description: Network retrieval protocol to use when requesting
         content from this source.

         Type: Protocol (see <a href="#section-4.3.2">Section 4.3.2</a>)

         Mandatory-to-Specify: Yes.

   Example Source object that describes a pair of endpoints (servers)
   the dCDN can use for acquiring content for the applicable host and/or
   URI path:

   {
     "endpoints": [
       "a.service123.ucdn.example",
       "b.service123.ucdn.example"
     ],
     "protocol": "http/1.1"
   }

<span class="h4"><a class="selflink" id="section-4.2.2" href="#section-4.2.2">4.2.2</a>.  LocationACL Metadata</span>

   LocationACL metadata defines which locations a User Agent needs to be
   in, in order to be able to receive the associated content.

   A LocationACL that does not include a "locations" property results in
   an action of "allow all", meaning that delivery can be performed
   regardless of the User Agent's location; otherwise, a CDN MUST take
   the action from the first footprint to match against the User Agent's
   location.  If two or more footprints overlap, the first footprint
   that matches against the User Agent's location determines the action




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   a CDN MUST take.  If the "locations" property is included but is
   empty or if none of the listed footprints match the User Agent's
   location, then the result is an action of "deny".

   Although the LocationACL, TimeWindowACL (see <a href="#section-4.2.3">Section 4.2.3</a>), and
   ProtocolACL (see <a href="#section-4.2.4">Section 4.2.4</a>) are independent GenericMetadata
   objects, they can provide conflicting information to a dCDN, e.g., a
   content request that is simultaneously allowed based on the
   LocationACL and denied based on the TimeWindowACL.  The dCDN MUST use
   the logical AND of all ACLs (where "allow" is true and "deny" is
   false) to determine whether or not a request should be allowed.

      Property: locations

         Description: ACL that allows or denies (blocks) delivery based
         on the User Agent's location.

         Type: Array of LocationRule objects (see <a href="#section-4.2.2.1">Section 4.2.2.1</a>)

         Mandatory-to-Specify: No.  Default is to allow all locations.

   Example LocationACL object that allows the dCDN to deliver content to
   any location / IP address:

   {
     "generic-metadata-type": "MI.LocationACL",
     "generic-metadata-value":
       {
       }
   }





















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   Example LocationACL object (which contains a LocationRule object that
   in turn contains a Footprint object) that only allows the dCDN to
   deliver content to User Agents in the USA:

   {
     "generic-metadata-type": "MI.LocationACL",
     "generic-metadata-value":
       {
         "locations": [
           {
             "action": "allow",
             "footprints": [
               {
                 "footprint-type": "countrycode",
                 "footprint-value": ["us"]
               }
             ]
           }
         ]
       }
   }

<span class="h5"><a class="selflink" id="section-4.2.2.1" href="#section-4.2.2.1">4.2.2.1</a>.  LocationRule</span>

   A LocationRule contains or references an array of Footprint objects
   and the corresponding action.

      Property: footprints

         Description: Array of footprints to which the rule applies.

         Type: Array of Footprint objects (see <a href="#section-4.2.2.2">Section 4.2.2.2</a>)

         Mandatory-to-Specify: Yes.

      Property: action

         Description: Defines whether the rule specifies locations to
         allow or deny.

         Type: Enumeration [allow|deny] encoded as a lowercase string

         Mandatory-to-Specify: No.  Default is "deny".








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   Example LocationRule object (which contains a Footprint object) that
   allows the dCDN to deliver content to clients in the USA:

   {
     "action": "allow",
     "footprints": [
       {
         "footprint-type": "countrycode",
         "footprint-value": ["us"]
       }
     ]
   }

<span class="h5"><a class="selflink" id="section-4.2.2.2" href="#section-4.2.2.2">4.2.2.2</a>.  Footprint</span>

   A Footprint object describes the footprint to which a LocationRule
   can be applied, e.g., an IPv4 address range or a geographic location.

      Property: footprint-type

         Description: Registered footprint type (see <a href="#section-7.2">Section 7.2</a>).  The
         footprint types specified by this document are "ipv4cidr"
         (IPv4CIDR; see <a href="#section-4.3.5">Section 4.3.5</a>), "ipv6cidr" (IPv6CIDR; see
         <a href="#section-4.3.6">Section 4.3.6</a>), "asn" (Autonomous System Number; see
         <a href="#section-4.3.7">Section 4.3.7</a>), and "countrycode" (Country Code; see
         <a href="#section-4.3.8">Section 4.3.8</a>).

         Type: Lowercase string

         Mandatory-to-Specify: Yes.

      Property: footprint-value

         Description: Array of footprint values conforming to the
         specification associated with the registered footprint type.
         Footprint values can be simple strings (e.g., IPv4CIDR,
         IPv6CIDR, ASN, and Country Code); however, other Footprint
         objects can be defined in the future, along with a more complex
         encoding (e.g., GPS coordinate tuples).

         Type: Array of footprints

         Mandatory-to-Specify: Yes.








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   Example Footprint object describing a footprint covering the USA:

   {
     "footprint-type": "countrycode",
     "footprint-value": ["us"]
   }

   Example Footprint object describing a footprint covering the IP
   address ranges 192.0.2.0/24 and 198.51.100.0/24:

   {
     "footprint-type": "ipv4cidr",
     "footprint-value": ["192.0.2.0/24", "198.51.100.0/24"]
   }

   Example Footprint object describing a footprint covering the IP
   address ranges 2001:db8::/32:

   {
     "footprint-type": "ipv6cidr",
     "footprint-value": ["2001:db8::/32"]
   }

   Example Footprint object describing a footprint covering the
   autonomous system 64496:

   {
     "footprint-type": "asn",
     "footprint-value": ["as64496"]
   }

<span class="h4"><a class="selflink" id="section-4.2.3" href="#section-4.2.3">4.2.3</a>.  TimeWindowACL</span>

   TimeWindowACL metadata defines time-based restrictions.

   A TimeWindowACL that does not include a "times" property results in
   an action of "allow all", meaning that delivery can be performed
   regardless of the time of the User Agent's request; otherwise, a CDN
   MUST take the action from the first window to match against the
   current time.  If two or more windows overlap, the first window that
   matches against the current time determines the action a CDN MUST
   take.  If the "times" property is included but is empty or if none of
   the listed windows match the current time, then the result is an
   action of "deny".

   Although the LocationACL (see <a href="#section-4.2.2">Section 4.2.2</a>), TimeWindowACL, and
   ProtocolACL (see <a href="#section-4.2.4">Section 4.2.4</a>) are independent GenericMetadata
   objects, they can provide conflicting information to a dCDN, e.g.,



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   a content request that is simultaneously allowed based on the
   LocationACL and denied based on the TimeWindowACL.  The dCDN MUST use
   the logical AND of all ACLs (where "allow" is true and "deny" is
   false) to determine whether or not a request should be allowed.

      Property: times

         Description: ACL that allows or denies (blocks) delivery based
         on the time of a User Agent's request.

         Type: Array of TimeWindowRule objects (see <a href="#section-4.2.3.1">Section 4.2.3.1</a>)

         Mandatory-to-Specify: No.  Default is to allow all time
         windows.

   Example TimeWindowACL object (which contains a TimeWindowRule object
   that in turn contains a TimeWindow object) that only allows the dCDN
   to deliver content to clients between 09:00 01/01/2000 UTC and 17:00
   01/01/2000 UTC:

   {
     "generic-metadata-type": "MI.TimeWindowACL",
     "generic-metadata-value":
       {
         "times": [
           {
             "action": "allow",
             "windows": [
               {
                 "start": 946717200,
                 "end": 946746000
               }
             ]
           }
         ]
       }
   }

<span class="h5"><a class="selflink" id="section-4.2.3.1" href="#section-4.2.3.1">4.2.3.1</a>.  TimeWindowRule</span>

   A TimeWindowRule contains or references an array of TimeWindow
   objects and the corresponding action.

      Property: windows

         Description: Array of time windows to which the rule applies.

         Type: Array of TimeWindow objects (see <a href="#section-4.2.3.2">Section 4.2.3.2</a>)



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         Mandatory-to-Specify: Yes.

      Property: action

         Description: Defines whether the rule specifies time windows to
         allow or deny.

         Type: Enumeration [allow|deny] encoded as a lowercase string

         Mandatory-to-Specify: No.  Default is "deny".

   Example TimeWindowRule object (which contains a TimeWindow object)
   that only allows the dCDN to deliver content to clients between 09:00
   01/01/2000 UTC and 17:00 01/01/2000 UTC:

   {
     "action": "allow",
     "windows": [
       {
         "start": 946717200,
         "end": 946746000
       }
     ]
   }

<span class="h5"><a class="selflink" id="section-4.2.3.2" href="#section-4.2.3.2">4.2.3.2</a>.  TimeWindow</span>

   A TimeWindow object describes a time range that can be applied by a
   TimeWindowACL, e.g., start 946717200 (i.e., 09:00 01/01/2000 UTC),
   end: 946746000 (i.e., 17:00 01/01/2000 UTC).

      Property: start

         Description: The start time of the window.

         Type: Time (see <a href="#section-4.3.4">Section 4.3.4</a>)

         Mandatory-to-Specify: Yes.

      Property: end

         Description: The end time of the window.

         Type: Time (see <a href="#section-4.3.4">Section 4.3.4</a>)

         Mandatory-to-Specify: Yes.





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   Example TimeWindow object that describes a time window from 09:00
   01/01/2000 UTC to 17:00 01/01/2000 UTC:

   {
     "start": 946717200,
     "end": 946746000
   }

<span class="h4"><a class="selflink" id="section-4.2.4" href="#section-4.2.4">4.2.4</a>.  ProtocolACL Metadata</span>

   ProtocolACL metadata defines delivery protocol restrictions.

   A ProtocolACL that does not include a protocol-acl property results
   in an action of "allow all", meaning that delivery can be performed
   regardless of the protocol in the User Agent's request; otherwise, a
   CDN MUST take the action from the first protocol to match against the
   request protocol.  If two or more request protocols overlap, the
   first protocol that matches the request protocol determines the
   action a CDN MUST take.  If the protocol-acl property is included but
   is empty or if none of the listed protocols match the request
   protocol, then the result is an action of "deny".

   Although the LocationACL (see <a href="#section-4.2.2">Section 4.2.2</a>), TimeWindowACL (see
   <a href="#section-4.2.3">Section 4.2.3</a>), and ProtocolACL are independent GenericMetadata
   objects, they can provide conflicting information to a dCDN, e.g., a
   content request that is simultaneously allowed based on the
   ProtocolACL and denied based on the TimeWindowACL.  The dCDN MUST use
   the logical AND of all ACLs (where "allow" is true and "deny" is
   false) to determine whether or not a request should be allowed.

      Property: protocol-acl

         Description: ACL that allows or denies (blocks) delivery based
         on delivery protocol.

         Type: Array of ProtocolRule objects (see <a href="#section-4.2.4.1">Section 4.2.4.1</a>)

         Mandatory-to-Specify: No.  Default is to allow all protocols.













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   Example ProtocolACL object (which contains a ProtocolRule object)
   that only allows the dCDN to deliver content using HTTP/1.1:

   {
     "generic-metadata-type": "MI.ProtocolACL",
     "generic-metadata-value":
       {
         "protocol-acl": [
           {
             "action": "allow",
             "protocols": ["http/1.1"]
           }
         ]
       }
   }

<span class="h5"><a class="selflink" id="section-4.2.4.1" href="#section-4.2.4.1">4.2.4.1</a>.  ProtocolRule</span>

   A ProtocolRule contains or references an array of Protocol objects
   and the corresponding action.

      Property: protocols

         Description: Array of protocols to which the rule applies.

         Type: Array of Protocol objects (see <a href="#section-4.3.2">Section 4.3.2</a>)

         Mandatory-to-Specify: Yes.

      Property: action

         Description: Defines whether the rule specifies protocols to
         allow or deny.

         Type: Enumeration [allow|deny] encoded as a lowercase string

         Mandatory-to-Specify: No.  Default is "deny".

   Example ProtocolRule object (which contains a Protocol object) that
   allows the dCDN to deliver content using HTTP/1.1:

   {
     "action": "allow",
     "protocols": ["http/1.1"]
   }






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<span class="h4"><a class="selflink" id="section-4.2.5" href="#section-4.2.5">4.2.5</a>.  DeliveryAuthorization Metadata</span>

   Delivery authorization defines authorization methods for the delivery
   of content to User Agents.

      Property: delivery-auth-methods

         Description: Options for authorizing content requests.
         Delivery for a content request is authorized if any one of the
         authorization methods in the list is satisfied for that
         request.

         Type: Array of Auth objects (see <a href="#section-4.2.7">Section 4.2.7</a>)

         Mandatory-to-Specify: No.  Default is no authorization
         required.

   Example DeliveryAuthorization object (which contains an Auth object):

   {
     "generic-metadata-type": "MI.DeliveryAuthorization",
     "generic-metadata-value":
       {
         "delivery-auth-methods": [
           {
             "auth-type": &lt;CDNI Payload Type of this Auth object&gt;,
             "auth-value":
             {
               &lt;Properties of this Auth object&gt;
             }
           }
         ]
       }
   }

<span class="h4"><a class="selflink" id="section-4.2.6" href="#section-4.2.6">4.2.6</a>.  Cache</span>

   A Cache object describes the cache control parameters to be applied
   to the content by intermediate caches.

   Cache keys are generated from the URI of the content request
   [<a href="./rfc7234" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Caching&quot;">RFC7234</a>].  In some cases, a CDN or content provider might want
   certain path segments or query parameters to be excluded from the
   cache key generation.  The Cache object provides guidance on what
   parts of the path and query string to include.






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      Property: exclude-path-pattern

         Description: A pattern for matching against the URI path, i.e.,
         against the path-absolute [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>].  The pattern can contain
         the wildcards "*" and "?", where "*" matches any sequence of
         pchar [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>] or "/" characters (including the empty string)
         and "?" matches exactly one pchar character.  The three
         literals "$", "*", and "?"  MUST be escaped as "$$", "$*", and
         "$?" (where "$" is the designated escape character).  All other
         characters are treated as literals.  Cache key generation MUST
         only include the portion of the path-absolute that matches the
         wildcard portions of the pattern.  Note: Inconsistency between
         the PatternMatch pattern (<a href="#section-4.1.5">Section 4.1.5</a>) and the
         exclude-path-pattern can result in inefficient caching.

         Type: String

         Mandatory-to-Specify: No.  Default is to use the full URI
         path-absolute to generate the cache key.

      Property: include-query-strings

         Description: Allows a Surrogate to specify the URI query string
         parameters [<a href="./rfc3986" title="&quot;Uniform Resource Identifier (URI): Generic Syntax&quot;">RFC3986</a>] to include when comparing the requested
         URI against the URIs in its cache for equivalence.  Matching
         query parameters MUST be case insensitive.  If all query
         parameters should be ignored, then the list MUST be specified
         and MUST be empty.  If a query parameter appears multiple times
         in the query string, each instance value MUST be aggregated
         prior to comparison.  For consistent cache key generation,
         query parameters SHOULD be evaluated in the order specified in
         this array.

         Type: Array of strings

         Mandatory-to-Specify: No.  Default is to consider all query
         string parameters when comparing URIs.

   Example Cache object that instructs the dCDN to use the full URI path
   and ignore all query parameters:

   {
     "generic-metadata-type": "MI.Cache",
     "generic-metadata-value":
     {
       "include-query-strings": []
     }
   }



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   Example Cache object that instructs the dCDN to exclude the "CDNX"
   path prefix and only include the (case-insensitive) query parameters
   named "mediaid" and "providerid":

   {
     "generic-metadata-type": "MI.Cache",
     "generic-metadata-value":
     {
       "exclude-path-pattern": "/CDNX/*",
       "include-query-strings": ["mediaid", "providerid"]
     }
   }

   Example Cache object that instructs the dCDN to exclude the "CDNX"
   path prefix but includes all query parameters:

   {
     "generic-metadata-type": "MI.Cache",
     "generic-metadata-value":
     {
       "exclude-path-pattern": "/CDNX/*"
     }
   }

<span class="h4"><a class="selflink" id="section-4.2.7" href="#section-4.2.7">4.2.7</a>.  Auth</span>

   An Auth object defines authentication and authorization methods to be
   used during content acquisition and content delivery, respectively.

   Note: This document does not define any Auth methods.  Individual
   Auth methods are being defined separately (e.g., URI Signing
   [<a href="#ref-CDNI-URI-SIGNING">CDNI-URI-SIGNING</a>]).  The GenericMetadata object that contains Auth
   objects is defined herein for convenience and so as not to be
   specific to any particular Auth method.

      Property: auth-type

         Description: Auth type (The CDNI Payload Type [<a href="./rfc7736" title="&quot;Content Delivery Network Interconnection (CDNI) Media Type Registration&quot;">RFC7736</a>] of the
         GenericMetadata object contained in the auth-value property).

         Type: String

         Mandatory-to-Specify: Yes.

      Property: auth-value

         Description: An object conforming to the specification
         associated with the Auth type.



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         Type: GenericMetadata object

         Mandatory-to-Specify: Yes.

   Example Auth object:

   {
     "generic-metadata-type": "MI.Auth",
     "generic-metadata-value":
     {
       "auth-type": &lt;CDNI Payload Type of this Auth object&gt;,
       "auth-value":
         {
           &lt;Properties of this Auth object&gt;
         }
     }
   }

<span class="h4"><a class="selflink" id="section-4.2.8" href="#section-4.2.8">4.2.8</a>.  Grouping</span>

   A Grouping object identifies a group of content to which a given
   asset belongs.

      Property: ccid

         Description: Content Collection IDentifier for an application-
         specific purpose such as logging aggregation.

         Type: String

         Mandatory-to-Specify: No.  Default is not to apply any
         grouping.

   Example Grouping object that specifies a Content Collection
   IDentifier for the content associated with the Grouping object's
   parent HostMetadata and PathMetadata:

   {
     "generic-metadata-type": "MI.Grouping",
     "generic-metadata-value":
     {
       "ccid": "ABCD"
     }
   }







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<span class="h3"><a class="selflink" id="section-4.3" href="#section-4.3">4.3</a>.  CDNI Metadata Simple Data Type Descriptions</span>

   This section describes the simple data types that are used for
   properties of CDNI Metadata objects.

<span class="h4"><a class="selflink" id="section-4.3.1" href="#section-4.3.1">4.3.1</a>.  Link</span>

   A Link object can be used in place of any of the objects described
   above.  Link objects can be used to avoid duplication if the same
   metadata information is repeated within the metadata tree.  When a
   Link object replaces another object, its "href" property is set to
   the URI of the resource and its "type" property is set to the CDNI
   Payload Type of the object it is replacing.

   dCDNs can detect the presence of a Link object by detecting the
   presence of a property named "href" within the object.  This means
   that GenericMetadata types MUST NOT contain a property named "href"
   because doing so would conflict with the ability for dCDNs to detect
   Link objects being used to reference a GenericMetadata object.

      Property: href

         Description: The URI of the addressable object being
         referenced.

         Type: String

         Mandatory-to-Specify: Yes.

      Property: type

         Description: The CDNI Payload Type of the object being
         referenced.

         Type: String

         Mandatory-to-Specify: No.  If the container specifies the type
         (e.g., the HostIndex object contains an array of HostMatch
         objects, so a Link object in the list of HostMatch objects must
         reference a HostMatch), then it is not necessary to explicitly
         specify a type.

   Example Link object referencing a HostMatch object:

   {
     "type": "MI.HostMatch",
     "href": "<a href="https://metadata.ucdn.example/hostmatch1234">https://metadata.ucdn.example/hostmatch1234</a>"
   }



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   Example Link object referencing a HostMatch object, without an
   explicit type, inside a HostIndex object:

   {
     "hosts": [
       {
         &lt;Properties of embedded HostMatch object&gt;
       },
       {
         "href": "<a href="https://metadata.ucdn.example/hostmatch1234">https://metadata.ucdn.example/hostmatch1234</a>"
       }
     ]
   }

<span class="h5"><a class="selflink" id="section-4.3.1.1" href="#section-4.3.1.1">4.3.1.1</a>.  Link Loop Prevention</span>

   When following a link, CDNI Metadata clients SHOULD verify that the
   CDNI Payload Type of the object retrieved matches the expected CDNI
   Payload Type, as indicated by the Link object or containing property.
   For GenericMetadata objects, type checks will prevent self-
   references; however, incorrect linking can result in circular
   references for structural metadata objects, specifically PathMatch
   and PathMetadata objects (Figure 1).  To prevent circular references,
   CDNI Metadata clients SHOULD verify that no duplicate links occur for
   PathMatch or PathMetadata objects.

<span class="h4"><a class="selflink" id="section-4.3.2" href="#section-4.3.2">4.3.2</a>.  Protocol</span>

   Protocol objects are used to specify protocols (from the "CDNI
   Metadata Protocol Types" registry; see <a href="#section-7.3">Section 7.3</a>) for content
   acquisition or delivery.

   Type: String

   Example:

   "http/1.1"

<span class="h4"><a class="selflink" id="section-4.3.3" href="#section-4.3.3">4.3.3</a>.  Endpoint</span>

   A hostname (with optional port) or an IP address (with optional
   port).

   All implementations MUST support IPv4 addresses encoded as specified
   by the "IPv4address" rule in <a href="./rfc3986#section-3.2.2">Section&nbsp;3.2.2 of [RFC3986]</a>.  IPv6
   addresses MUST be encoded in one of the IPv6 address formats
   specified in [<a href="./rfc5952" title="&quot;A Recommendation for IPv6 Address Text Representation&quot;">RFC5952</a>], although receivers MUST support all IPv6
   address formats specified in [<a href="./rfc4291" title="&quot;IP Version 6 Addressing Architecture&quot;">RFC4291</a>].  Hostnames MUST conform to



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   the Domain Name System (DNS) syntax defined in [<a href="./rfc1034" title="&quot;Domain names - concepts and facilities&quot;">RFC1034</a>] and
   [<a href="./rfc1123" title="&quot;Requirements for Internet Hosts - Application and Support&quot;">RFC1123</a>].  Internationalized Domain Names (IDNs) must first be
   transformed to the A-label form [<a href="./rfc5890" title="&quot;Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework&quot;">RFC5890</a>] as per [<a href="./rfc5891" title="&quot;Internationalized Domain Names in Applications (IDNA): Protocol&quot;">RFC5891</a>].

   Type: String

   Example hostname:

   "metadata.ucdn.example"

   Example IPv4 address:

   "192.0.2.1"

   Example IPv6 address (with port number):

   "[2001:db8::1]:81"

<span class="h4"><a class="selflink" id="section-4.3.4" href="#section-4.3.4">4.3.4</a>.  Time</span>

   A time value expressed in seconds since the UNIX epoch (i.e., zero
   hours, zero minutes, zero seconds, on January 1, 1970) Coordinated
   Universal Time (UTC) [<a href="#ref-POSIX" title="&quot;Information Technology Portable Operating System Interface (POSIX) Part 1: System Application Program Interface (API) [C Language]&quot;">POSIX</a>].

   Type: Integer

   Example time representing 09:00:00 01/01/2000 UTC:

   946717200

<span class="h4"><a class="selflink" id="section-4.3.5" href="#section-4.3.5">4.3.5</a>.  IPv4CIDR</span>

   An IPv4address Classless Inter-Domain Routing (CIDR) block encoded as
   specified by the "IPv4address" rule in <a href="./rfc3986#section-3.2.2">Section&nbsp;3.2.2 of [RFC3986]</a>
   followed by a "/" followed by an unsigned integer representing the
   leading bits of the routing prefix (i.e., IPv4 CIDR notation).
   Single IP addresses can be expressed as /32.

   Type: String

   Example IPv4CIDR:

   "192.0.2.0/24"








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<span class="h4"><a class="selflink" id="section-4.3.6" href="#section-4.3.6">4.3.6</a>.  IPv6CIDR</span>

   An IPv6address CIDR block encoded in one of the IPv6 address formats
   specified in [<a href="./rfc5952" title="&quot;A Recommendation for IPv6 Address Text Representation&quot;">RFC5952</a>] followed by a "/" followed by an unsigned
   integer representing the leading bits of the routing prefix (i.e.,
   IPv6 CIDR notation).  Single IP addresses can be expressed as /128.

   Type: String

   Example IPv6CIDR:

   "2001:db8::/32"

<span class="h4"><a class="selflink" id="section-4.3.7" href="#section-4.3.7">4.3.7</a>.  ASN</span>

   An ASN value encoded as a string consisting of the characters "as"
   (in lowercase) followed by the ASN [<a href="./rfc6793" title="&quot;BGP Support for Four-Octet Autonomous System (AS) Number Space&quot;">RFC6793</a>].

   Type: String

   Example ASN:

   "as64496"

<span class="h4"><a class="selflink" id="section-4.3.8" href="#section-4.3.8">4.3.8</a>.  Country Code</span>

   An ISO 3166-1 alpha-2 code [<a href="#ref-ISO3166-1">ISO3166-1</a>] in lowercase.

   Type: String

   Example Country Code representing the USA:

   "us"

<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>.  CDNI Metadata Capabilities</span>

   CDNI Metadata is used to convey information pertaining to content
   delivery from the uCDN to the dCDN.  For optional metadata, it can be
   useful for the uCDN to know, prior to delegating any content requests
   to a given dCDN, if that dCDN supports the underlying functionality
   described by the metadata.  If some metadata is mandatory-to-enforce
   and the dCDN does not support it, any delegated requests for content
   that requires that metadata will fail.  The uCDN will likely want to
   avoid delegating those requests to that dCDN.  Likewise, for any
   metadata that might be assigned optional values, it could be useful
   for the uCDN to know, prior to delegating any content requests to a
   given dCDN, which values that dCDN supports.  If the optional value
   assigned to a given piece of content's metadata is not supported by



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   the dCDN, any delegated requests for that content can fail, so again
   the uCDN is likely to want to avoid delegating those requests to
   that dCDN.

   The CDNI Footprint &amp; Capabilities Advertisement interface (FCI)
   provides a means of advertising capabilities from the dCDN to the
   uCDN [<a href="./rfc8008" title="&quot;Content Delivery Network Interconnection (CDNI) Request Routing: Footprint and Capabilities Semantics&quot;">RFC8008</a>].  Support for optional metadata types and values can
   be advertised using the FCI.

<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>.  CDNI Metadata Interface</span>

   This section specifies an interface to enable a dCDN to retrieve CDNI
   Metadata objects from a uCDN.

   The interface can be used by a dCDN to retrieve CDNI Metadata objects
   in either of two ways:

   o  Dynamically, as required by the dCDN to process received requests
      -- for example, in response to a query from a uCDN over the CDNI
      Request Routing Redirection interface (RI) [<a href="./rfc7975" title="&quot;Request Routing Redirection Interface for Content Delivery Network (CDN) Interconnection&quot;">RFC7975</a>] or in
      response to receiving a request for content from a User Agent.

   o  In advance of being required -- for example, in the case of
      pre-positioned CDNI Metadata acquisition, initiated through the
      "CDNI Control interface / Triggers" (CI/T) interface [<a href="./rfc8007" title="&quot;Content Delivery Network Interconnection (CDNI) Control Interface / Triggers&quot;">RFC8007</a>].

   The CDNI Metadata interface is built on the principles of HTTP web
   services.  In particular, this means that requests and responses over
   the interface are built around the transfer of representations of
   hyperlinked resources.  A resource in the context of the CDNI
   Metadata interface is any object in the object model (as described in
   Sections <a href="#section-3">3</a> and <a href="#section-4">4</a>).

   CDNI Metadata servers (i.e., servers in the uCDN) are free to assign
   whatever structure they desire to the URIs for CDNI Metadata objects,
   and CDNI Metadata clients MUST NOT make any assumptions regarding the
   structure of CDNI Metadata URIs or the mapping between CDNI Metadata
   objects and their associated URIs.  Any URIs present in the examples
   in this document are purely illustrative and are not intended to
   impose a definitive structure on CDNI Metadata interface
   implementations.










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<span class="h3"><a class="selflink" id="section-6.1" href="#section-6.1">6.1</a>.  Transport</span>

   The CDNI Metadata interface uses HTTP as the underlying protocol
   transport [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>].

   The HTTP method in the request defines the operation the request
   would like to perform.  A server implementation of the CDNI Metadata
   interface MUST support the HTTP GET and HEAD methods.

   The corresponding HTTP response returns the status of the operation
   in the HTTP status code and returns the current representation of the
   resource (if appropriate) in the response body.  HTTP responses that
   contain a response body SHOULD include an entity-tag (ETag) to enable
   validation of cached versions of returned resources.

   As the CDNI Metadata interface builds on top of HTTP, CDNI Metadata
   server implementations MAY make use of any HTTP feature when
   implementing the CDNI Metadata interface; for example, a CDNI
   Metadata server MAY make use of HTTP's caching mechanisms to indicate
   that the returned response/representation can be reused without
   re-contacting the CDNI Metadata server.

<span class="h3"><a class="selflink" id="section-6.2" href="#section-6.2">6.2</a>.  Retrieval of CDNI Metadata Resources</span>

   In the general case, a CDNI Metadata server makes CDNI Metadata
   objects available via unique URIs; thus, in order to retrieve CDNI
   Metadata, a CDNI Metadata client (i.e., a client in the dCDN) first
   makes an HTTP GET request for the URI of the HostIndex, which
   provides an array of hostnames for which the uCDN can delegate
   content delivery to the dCDN.

   In order to retrieve the CDNI Metadata for a particular request, the
   CDNI Metadata client processes the received HostIndex object and
   finds the corresponding HostMetadata entry (by matching the hostname
   in the request against the hostnames listed in the HostMatch
   objects).  If the HostMetadata is linked (rather than embedded), the
   CDNI Metadata client then makes an HTTP GET request for the URI
   specified in the "href" property of the Link object, which points to
   the HostMetadata object itself.

   In order to retrieve the most specific metadata for a particular
   request, the CDNI Metadata client inspects the HostMetadata for
   references to more-specific PathMetadata objects (by matching the URI
   path in the request against the path-pattern property items in any
   PathMatch objects listed in the HostMetadata object).  If a
   PathMetadata object is found to match (and is linked rather than
   embedded), the CDNI Metadata client makes another HTTP GET request
   for the PathMetadata.  Each PathMetadata object can also include



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   references to additional more-specific metadata.  If this is the
   case, the CDNI Metadata client continues requesting PathMatch and
   PathMetadata objects recursively.  The CDNI Metadata client repeats
   this approach of processing metadata objects and retrieving (via HTTP
   GETs) any linked objects until it has all the metadata objects it
   requires in order to process the redirection request from the uCDN or
   the content request from a User Agent.

   In cases where a dCDN is not able to retrieve the entire set of CDNI
   Metadata associated with a User Agent request, or it has retrieved
   that metadata but it is stale according to standard HTTP caching
   rules and cannot be revalidated -- for example, because the uCDN is
   unreachable or returns an HTTP 4xx or 5xx status in response to some
   or all of the dCDN's CDNI Metadata requests -- the dCDN MUST NOT
   serve the requested content.

   Where a dCDN is interconnected with multiple uCDNs, the dCDN needs to
   determine which uCDN's CDNI Metadata interface should be used to
   handle a particular User Agent request.

   When HTTP redirection (e.g., HTTP 302 redirects) is being used
   between CDNs, it is expected that the dCDN will be able to determine
   the uCDN that redirected a particular request from information
   contained in the received request (e.g., via the URI).  With
   knowledge of which uCDN routed the request, the dCDN can choose the
   correct uCDN from which to obtain the HostIndex.  Note that the
   HostIndexes served by each uCDN can be unique.

   In the case of DNS redirection, there is not always sufficient
   information carried in the DNS request from User Agents to determine
   the uCDN that redirected a particular request (e.g., when content
   from a given host is redirected to a given dCDN by more than one
   uCDN); therefore, dCDNs will have to apply local policy when deciding
   which uCDN's CDNI Metadata interface to use.

<span class="h3"><a class="selflink" id="section-6.3" href="#section-6.3">6.3</a>.  Bootstrapping</span>

   The URI for the HostIndex object of a given uCDN needs to be
   configured in the dCDN.  All other objects/resources are then
   discoverable from the HostIndex object by following any links in the
   HostIndex object, and through the referenced HostMetadata and
   PathMetadata objects and their GenericMetadata sub-objects.

   Manual configuration of the URI for the HostIndex object is outside
   the scope of this document.






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<span class="h3"><a class="selflink" id="section-6.4" href="#section-6.4">6.4</a>.  Encoding</span>

   CDNI Metadata objects MUST be encoded as I-JSON objects [<a href="./rfc7493" title="&quot;The I-JSON Message Format&quot;">RFC7493</a>]
   containing a dictionary of (key,value) pairs where the keys are the
   property names and the values are the associated property values.

   The keys of the dictionary are the names of the properties associated
   with the object and are therefore dependent on the specific object
   being encoded (i.e., dependent on the CDNI Payload Type of the
   returned resource).  Likewise, the values associated with each
   property (dictionary key) are dependent on the specific object being
   encoded (i.e., dependent on the CDNI Payload Type of the returned
   resource).

   Dictionary keys (properties) in I-JSON are case sensitive.  By
   convention, any dictionary key (property) defined by this document
   (for example, the names of CDNI Metadata object properties) MUST be
   lowercase.

<span class="h3"><a class="selflink" id="section-6.5" href="#section-6.5">6.5</a>.  Extensibility</span>

   The set of GenericMetadata objects can be extended with additional
   (standards-based or vendor-specific) metadata objects through the
   specification of new GenericMetadata objects.  The GenericMetadata
   object defined in <a href="#section-4.1.7">Section 4.1.7</a> specifies a type field and a type-
   specific value field that allow any metadata to be included in either
   the HostMetadata or PathMetadata arrays.

   As with the initial GenericMetadata types defined in <a href="#section-4.2">Section 4.2</a>,
   future GenericMetadata types MUST specify the information necessary
   for constructing and decoding the GenericMetadata object.

   Any document that defines a new GenericMetadata type MUST:

   1.  Register the CDNI Payload Type [<a href="./rfc7736" title="&quot;Content Delivery Network Interconnection (CDNI) Media Type Registration&quot;">RFC7736</a>] used to identify the new
       GenericMetadata type being specified.

   2.  Define the set of properties associated with the new
       GenericMetadata object.  GenericMetadata MUST NOT contain a
       property named "href" because doing so would conflict with the
       ability to detect Link objects (see <a href="#section-4.3.1">Section 4.3.1</a>).

   3.  For each property, define a name, description, type, and whether
       or not the property is mandatory-to-specify.

   4.  Describe the semantics of the new type, including its purpose,
       and provide a use case to which it applies, including an example
       encoded in I-JSON.



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   5.  Describe the security and privacy consequences, for both the User
       Agent and the CDNs, of the new GenericMetadata object.

   6.  Describe any relation to, conflict with, or obsolescence of other
       existing CDNI Metadata objects.

   Note: In the case of vendor-specific extensions, vendor-identifying
   CDNI Payload Type names will decrease the possibility of
   GenericMetadata type collisions.  It is RECOMMENDED that any
   vendor-specific extensions use vendor-identifying CDNI Payload Type
   names.

<span class="h3"><a class="selflink" id="section-6.6" href="#section-6.6">6.6</a>.  Metadata Enforcement</span>

   At any given time, the set of GenericMetadata types supported by the
   uCDN might not match the set of GenericMetadata types supported by
   the dCDN.

   In cases where a uCDN sends metadata containing a GenericMetadata
   type that a dCDN does not support, the dCDN MUST enforce the
   semantics of the mandatory-to-enforce property.  If a dCDN does not
   understand or is unable to perform the functions associated with any
   mandatory-to-enforce metadata, the dCDN MUST NOT service any requests
   for the corresponding content.

   Note: Ideally, uCDNs would not delegate content requests to a dCDN
   that does not support the mandatory-to-enforce metadata associated
   with the content being requested.  However, even if the uCDN has
   a priori knowledge of the metadata supported by the dCDN (e.g., via
   the FCI or through out-of-band negotiation between CDN operators),
   metadata support can fluctuate or be inconsistent (e.g., due to
   miscommunication, misconfiguration, or temporary outage).  Thus, the
   dCDN MUST always evaluate all metadata associated with redirection
   and content requests and reject any requests where
   mandatory-to-enforce metadata associated with the content cannot be
   enforced.

<span class="h3"><a class="selflink" id="section-6.7" href="#section-6.7">6.7</a>.  Metadata Conflicts</span>

   It is possible that new metadata definitions will obsolete or
   conflict with existing GenericMetadata (e.g., a future revision of
   the CDNI Metadata interface could redefine the Auth GenericMetadata
   object or a custom vendor extension could implement an alternate Auth
   metadata option).  If multiple metadata (e.g., MI.Auth.v2,
   vendor1.Auth, and vendor2.Auth) all conflict with an existing
   GenericMetadata object (i.e., MI.Auth) and all are marked as





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   mandatory-to-enforce, it could be ambiguous as to which metadata
   should be applied, especially in the case of overlapping
   functionality.

   As described in <a href="#section-3.3">Section 3.3</a>, metadata override only applies to
   metadata objects of the same exact type found in HostMetadata and
   nested PathMetadata structures.  The CDNI Metadata interface does not
   support enforcement of dependencies between different GenericMetadata
   types.  It is the responsibility of the CSP and the CDN operators to
   ensure that metadata assigned to a given piece of content do not
   conflict.

   Note: Because metadata is inherently ordered in HostMetadata and
   PathMetadata arrays, as well as in the PathMatch hierarchy, multiple
   conflicting metadata types MAY be used; however, metadata hierarchies
   SHOULD ensure that independent PathMatch root objects are used to
   prevent ambiguous or conflicting metadata definitions.

<span class="h3"><a class="selflink" id="section-6.8" href="#section-6.8">6.8</a>.  Versioning</span>

   The version of CDNI Metadata objects is conveyed inside the CDNI
   Payload Type that is included in either (1) the HTTP Content-Type
   header (for example, "Content-Type: application/cdni;
   ptype=MI.HostIndex" when retrieved via a link) or (2) in the link
   type (<a href="#section-4.3.1">Section 4.3.1</a>), generic-metadata-type (<a href="#section-4.1.7">Section 4.1.7</a>), or
   auth-type (<a href="#section-4.2.7">Section 4.2.7</a>) properties in the JSON payload.  The CDNI
   Payload Type uniquely identifies the specification defining that
   object, including any relation to, conflicts with, or obsolescence of
   other metadata.  There is no explicit version mapping requirement;
   however, for ease of understanding, metadata creators SHOULD make new
   versions of metadata easily visible via the CDNI Payload Type, e.g.,
   by appending a version string.  Note: A version string is optional on
   the first version (e.g., MI.HostIndex) but could be added for
   subsequent versions (MI.HostIndex.v2, MI.HostIndex.v3, etc.).

   Except when referenced by a Link object, nested metadata objects
   (i.e., structural metadata below the HostIndex; and Source,
   LocationRule, TimeWindowRule, ProtocolRule, Footprint, and TimeWindow
   objects) can be serialized into a JSON payload without explicit CDNI
   Payload Type information.  The type is inferred from the outer
   structural metadata, GenericMetadata, or Auth object CDNI Payload
   Type.  To avoid ambiguity when revising nestable metadata objects,
   any outer metadata object(s) MUST be reversioned and allocated new
   CDNI Payload Type(s) at the same time.  For example, the MI.HostIndex
   object defined in this document contains an array of MI.HostMatch
   objects, each of which in turn contains a MI.HostMetadata object.  If
   a new MI.HostMetadata.v2 object were required, the outer MI.HostIndex
   and MI.HostMatch objects would need to be revised, e.g., to



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   MI.HostIndex.v2 and MI.HostMatch.v2, respectively.  Similarly, if a
   new MI.TimeWindowRule.v2 object were required, the outer
   MI.TimeWindowACL object would need to be revised, e.g., to
   MI.TimeWindowACL.v2; however, the MI.TimeWindowRule.v2 object could
   still contain MI.TimeWindow objects, if so specified.

   HTTP requests sent to a metadata server SHOULD include an Accept
   header with the CDNI Payload Type of the expected object.  Metadata
   clients can specify multiple CDNI Payload Types in the Accept header;
   for example, if a metadata client is capable of processing two
   different versions of the same type of object (defined by different
   CDNI Payload Types), it might decide to include both in the Accept
   header.

<span class="h3"><a class="selflink" id="section-6.9" href="#section-6.9">6.9</a>.  Media Types</span>

   All CDNI Metadata objects use the media type "application/cdni".  The
   CDNI Payload Type for each object then contains the object name of
   that object as defined by this document, prefixed with "MI.".
   Table 4 lists the CDNI Payload Types for the metadata objects
   (resources) specified in this document.

           +-----------------------+--------------------------+
           | Data Object           | CDNI Payload Type        |
           +-----------------------+--------------------------+
           | HostIndex             | MI.HostIndex             |
           | HostMatch             | MI.HostMatch             |
           | HostMetadata          | MI.HostMetadata          |
           | PathMatch             | MI.PathMatch             |
           | PatternMatch          | MI.PatternMatch          |
           | PathMetadata          | MI.PathMetadata          |
           | SourceMetadata        | MI.SourceMetadata        |
           | Source                | MI.Source                |
           | LocationACL           | MI.LocationACL           |
           | LocationRule          | MI.LocationRule          |
           | Footprint             | MI.Footprint             |
           | TimeWindowACL         | MI.TimeWindowACL         |
           | TimeWindowRule        | MI.TimeWindowRule        |
           | TimeWindow            | MI.TimeWindow            |
           | ProtocolACL           | MI.ProtocolACL           |
           | ProtocolRule          | MI.ProtocolRule          |
           | DeliveryAuthorization | MI.DeliveryAuthorization |
           | Cache                 | MI.Cache                 |
           | Auth                  | MI.Auth                  |
           | Grouping              | MI.Grouping              |
           +-----------------------+--------------------------+

           Table 4: CDNI Payload Types for CDNI Metadata Objects



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<span class="h3"><a class="selflink" id="section-6.10" href="#section-6.10">6.10</a>.  Complete CDNI Metadata Example</span>

   A dCDN requests the HostIndex and receives the following object with
   a CDNI Payload Type of "MI.HostIndex":

   {
     "hosts": [
       {
         "host": "video.example.com",
         "host-metadata": {
           "type": "MI.HostMetadata",
           "href": "<a href="https://metadata.ucdn.example/host1234">https://metadata.ucdn.example/host1234</a>"
         }
       },
       {
         "host": "images.example.com",
         "host-metadata": {
           "type": "MI.HostMetadata",
           "href": "<a href="https://metadata.ucdn.example/host5678">https://metadata.ucdn.example/host5678</a>"
         }
       }
     ]
   }

   If the incoming request has a Host header with "video.example.com",
   then the dCDN would fetch the HostMetadata object from
   "<a href="https://metadata.ucdn.example/host1234">https://metadata.ucdn.example/host1234</a>" expecting a CDNI Payload
   Type of "MI.HostMetadata":

   {
     "metadata": [
       {
         "generic-metadata-type": "MI.SourceMetadata",
         "generic-metadata-value": {
           "sources": [
             {
               "endpoint": ["acq1.ucdn.example"],
               "protocol": "http/1.1"
             },
             {
               "endpoint": ["acq2.ucdn.example"],
               "protocol": "http/1.1"
             }
           ]
         }
       },





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       {
         "generic-metadata-type": "MI.LocationACL",
         "generic-metadata-value": {
           "locations": [
             {
               "footprints": [
                 {
                   "footprint-type": "ipv4cidr",
                   "footprint-value": ["192.0.2.0/24"]
                 },
                 {
                   "footprint-type": "ipv6cidr",
                   "footprint-value": ["2001:db8::/32"]
                 },
                 {
                   "footprint-type": "countrycode",
                   "footprint-value": ["us"]
                 },
                 {
                   "footprint-type": "asn",
                   "footprint-value": ["as64496"]
                 }
               ],
               "action": "deny"
             }
           ]
         }
       },
       {
         "generic-metadata-type": "MI.ProtocolACL",
         "generic-metadata-value": {
           "protocol-acl": [
             {
               "protocols": [
                 "http/1.1"
               ],
               "action": "allow"
             }
           ]
         }
       }
     ],









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     "paths": [
       {
         "path-pattern": {
           "pattern": "/videos/trailers/*"
         },
         "path-metadata": {
           "type": "MI.PathMetadata",
           "href": "<a href="https://metadata.ucdn.example/host1234/pathABC">https://metadata.ucdn.example/host1234/pathABC</a>"
         }
       },
       {
         "path-pattern": {
           "pattern": "/videos/movies/*"
         },
         "path-metadata": {
           "type": "MI.PathMetadata",
           "href": "<a href="https://metadata.ucdn.example/host1234/pathDEF">https://metadata.ucdn.example/host1234/pathDEF</a>"
         }
       }
     ]
   }

   Suppose that the path of the requested resource matches the
   "/videos/movies/*" pattern; the next metadata requested would be for
   "<a href="https://metadata.ucdn.example/host1234/pathDEF">https://metadata.ucdn.example/host1234/pathDEF</a>" with an expected
   CDNI Payload Type of "MI.PathMetadata":

   {
     "metadata": [],
     "paths": [
       {
         "path-pattern": {
           "pattern": "/videos/movies/hd/*"
         },
         "path-metadata": {
           "type": "MI.PathMetadata",
           "href":
             "<a href="https://metadata.ucdn.example/host1234/pathDEF/path123">https://metadata.ucdn.example/host1234/pathDEF/path123</a>"
         }
       }
     ]
   }









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   Finally, if the path of the requested resource also matches the
   "/videos/movies/hd/*" pattern, the dCDN would also fetch the
   following object from
   "<a href="https://metadata.ucdn.example/host1234/pathDEF/path123">https://metadata.ucdn.example/host1234/pathDEF/path123</a>" with a CDNI
   Payload Type of "MI.PathMetadata":

   {
     "metadata": [
       {
         "generic-metadata-type": "MI.TimeWindowACL",
         "generic-metadata-value": {
           "times": [
             "windows": [
               {
                 "start": "1213948800",
                 "end": "1478047392"
               }
             ],
             "action": "allow"
           ]
         }
       }
     ]
   }

   The final set of metadata that applies to the requested resource
   includes a SourceMetadata, a LocationACL, a ProtocolACL, and a
   TimeWindowACL.























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<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>.  IANA Considerations</span>

<span class="h3"><a class="selflink" id="section-7.1" href="#section-7.1">7.1</a>.  CDNI Payload Types</span>

   This document requests the registration of the following entries
   under the "CDNI Payload Types" registry hosted by IANA:

               +--------------------------+---------------+
               | Payload Type             | Specification |
               +--------------------------+---------------+
               | MI.HostIndex             | <a href="./rfc8006">RFC 8006</a>      |
               | MI.HostMatch             | <a href="./rfc8006">RFC 8006</a>      |
               | MI.HostMetadata          | <a href="./rfc8006">RFC 8006</a>      |
               | MI.PathMatch             | <a href="./rfc8006">RFC 8006</a>      |
               | MI.PatternMatch          | <a href="./rfc8006">RFC 8006</a>      |
               | MI.PathMetadata          | <a href="./rfc8006">RFC 8006</a>      |
               | MI.SourceMetadata        | <a href="./rfc8006">RFC 8006</a>      |
               | MI.Source                | <a href="./rfc8006">RFC 8006</a>      |
               | MI.LocationACL           | <a href="./rfc8006">RFC 8006</a>      |
               | MI.LocationRule          | <a href="./rfc8006">RFC 8006</a>      |
               | MI.Footprint             | <a href="./rfc8006">RFC 8006</a>      |
               | MI.TimeWindowACL         | <a href="./rfc8006">RFC 8006</a>      |
               | MI.TimeWindowRule        | <a href="./rfc8006">RFC 8006</a>      |
               | MI.TimeWindow            | <a href="./rfc8006">RFC 8006</a>      |
               | MI.ProtocolACL           | <a href="./rfc8006">RFC 8006</a>      |
               | MI.ProtocolRule          | <a href="./rfc8006">RFC 8006</a>      |
               | MI.DeliveryAuthorization | <a href="./rfc8006">RFC 8006</a>      |
               | MI.Cache                 | <a href="./rfc8006">RFC 8006</a>      |
               | MI.Auth                  | <a href="./rfc8006">RFC 8006</a>      |
               | MI.Grouping              | <a href="./rfc8006">RFC 8006</a>      |
               +--------------------------+---------------+

<span class="h4"><a class="selflink" id="section-7.1.1" href="#section-7.1.1">7.1.1</a>.  CDNI MI HostIndex Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish HostIndex
   MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.1.1">Section 4.1.1</a>











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<span class="h4"><a class="selflink" id="section-7.1.2" href="#section-7.1.2">7.1.2</a>.  CDNI MI HostMatch Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish HostMatch
   MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.1.2">Section 4.1.2</a>

<span class="h4"><a class="selflink" id="section-7.1.3" href="#section-7.1.3">7.1.3</a>.  CDNI MI HostMetadata Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   HostMetadata MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.1.3">Section 4.1.3</a>

<span class="h4"><a class="selflink" id="section-7.1.4" href="#section-7.1.4">7.1.4</a>.  CDNI MI PathMatch Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish PathMatch
   MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.1.4">Section 4.1.4</a>

<span class="h4"><a class="selflink" id="section-7.1.5" href="#section-7.1.5">7.1.5</a>.  CDNI MI PatternMatch Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   PatternMatch MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.1.5">Section 4.1.5</a>

<span class="h4"><a class="selflink" id="section-7.1.6" href="#section-7.1.6">7.1.6</a>.  CDNI MI PathMetadata Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   PathMetadata MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.1.6">Section 4.1.6</a>







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<span class="h4"><a class="selflink" id="section-7.1.7" href="#section-7.1.7">7.1.7</a>.  CDNI MI SourceMetadata Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   SourceMetadata MI objects (and any associated capability
   advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.1">Section 4.2.1</a>

<span class="h4"><a class="selflink" id="section-7.1.8" href="#section-7.1.8">7.1.8</a>.  CDNI MI Source Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish Source MI
   objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.1.1">Section 4.2.1.1</a>

<span class="h4"><a class="selflink" id="section-7.1.9" href="#section-7.1.9">7.1.9</a>.  CDNI MI LocationACL Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   LocationACL MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.2">Section 4.2.2</a>

<span class="h4"><a class="selflink" id="section-7.1.10" href="#section-7.1.10">7.1.10</a>.  CDNI MI LocationRule Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   LocationRule MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.2.1">Section 4.2.2.1</a>

<span class="h4"><a class="selflink" id="section-7.1.11" href="#section-7.1.11">7.1.11</a>.  CDNI MI Footprint Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish Footprint
   MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.2.2">Section 4.2.2.2</a>






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<span class="h4"><a class="selflink" id="section-7.1.12" href="#section-7.1.12">7.1.12</a>.  CDNI MI TimeWindowACL Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   TimeWindowACL MI objects (and any associated capability
   advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.3">Section 4.2.3</a>

<span class="h4"><a class="selflink" id="section-7.1.13" href="#section-7.1.13">7.1.13</a>.  CDNI MI TimeWindowRule Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   TimeWindowRule MI objects (and any associated capability
   advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.3.1">Section 4.2.3.1</a>

<span class="h4"><a class="selflink" id="section-7.1.14" href="#section-7.1.14">7.1.14</a>.  CDNI MI TimeWindow Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   TimeWindow MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.3.2">Section 4.2.3.2</a>

<span class="h4"><a class="selflink" id="section-7.1.15" href="#section-7.1.15">7.1.15</a>.  CDNI MI ProtocolACL Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   ProtocolACL MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.4">Section 4.2.4</a>

<span class="h4"><a class="selflink" id="section-7.1.16" href="#section-7.1.16">7.1.16</a>.  CDNI MI ProtocolRule Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   ProtocolRule MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.4.1">Section 4.2.4.1</a>





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<span class="h4"><a class="selflink" id="section-7.1.17" href="#section-7.1.17">7.1.17</a>.  CDNI MI DeliveryAuthorization Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish
   DeliveryAuthorization MI objects (and any associated capability
   advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.5">Section 4.2.5</a>

<span class="h4"><a class="selflink" id="section-7.1.18" href="#section-7.1.18">7.1.18</a>.  CDNI MI Cache Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish Cache MI
   objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.6">Section 4.2.6</a>

<span class="h4"><a class="selflink" id="section-7.1.19" href="#section-7.1.19">7.1.19</a>.  CDNI MI Auth Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish Auth MI
   objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.7">Section 4.2.7</a>

<span class="h4"><a class="selflink" id="section-7.1.20" href="#section-7.1.20">7.1.20</a>.  CDNI MI Grouping Payload Type</span>

   Purpose: The purpose of this Payload Type is to distinguish Grouping
   MI objects (and any associated capability advertisement)

   Interface: MI/FCI

   Encoding: see <a href="#section-4.2.8">Section 4.2.8</a>

<span class="h3"><a class="selflink" id="section-7.2" href="#section-7.2">7.2</a>.  "CDNI Metadata Footprint Types" Registry</span>

   IANA has created a new "CDNI Metadata Footprint Types" subregistry in
   the "Content Delivery Network Interconnection (CDNI) Parameters"
   registry.  The "CDNI Metadata Footprint Types" namespace defines the
   valid Footprint object type values used by the Footprint object
   described in <a href="#section-4.2.2.2">Section 4.2.2.2</a>.  Additions to the "CDNI Metadata
   Footprint Types" namespace conform to the Specification Required
   policy as defined in [<a href="./rfc5226" title="">RFC5226</a>].  The Designated Expert will verify
   that new type definitions do not duplicate existing type definitions




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   and prevent gratuitous additions to the namespace.  New registrations
   are required to provide a clear description of how to interpret new
   footprint types.

   The following table defines the initial values for the "CDNI Metadata
   Footprint Types" registry:

    +----------------+--------------------------------+---------------+
    | Footprint Type | Description                    | Specification |
    +----------------+--------------------------------+---------------+
    | ipv4cidr       | IPv4 CIDR address block        | <a href="./rfc8006">RFC 8006</a>      |
    | ipv6cidr       | IPv6 CIDR address block        | <a href="./rfc8006">RFC 8006</a>      |
    | asn            | Autonomous System Number (ASN) | <a href="./rfc8006">RFC 8006</a>      |
    | countrycode    | ISO 3166-1 alpha-2 code        | <a href="./rfc8006">RFC 8006</a>      |
    +----------------+--------------------------------+---------------+

<span class="h3"><a class="selflink" id="section-7.3" href="#section-7.3">7.3</a>.  "CDNI Metadata Protocol Types" Registry</span>

   IANA has created a new "CDNI Metadata Protocol Types" subregistry in
   the "Content Delivery Network Interconnection (CDNI) Parameters"
   registry.  The "CDNI Metadata Protocol Types" namespace defines the
   valid Protocol object values (<a href="#section-4.3.2">Section 4.3.2</a>) used by the
   SourceMetadata and ProtocolACL objects.  Additions to the Protocol
   namespace conform to the Specification Required policy as defined in
   [<a href="./rfc5226" title="">RFC5226</a>], where the specification defines the Protocol Type and the
   protocol to which it is associated.  The Designated Expert will
   verify that new protocol definitions do not duplicate existing
   protocol definitions and prevent gratuitous additions to the
   namespace.

   The following table defines the initial Protocol values corresponding
   to the HTTP and HTTPS protocols:

   +-----------+----------------------+---------------+----------------+
   | Protocol  | Description          | Type          | Protocol       |
   | Type      |                      | Specification | Specifications |
   +-----------+----------------------+---------------+----------------+
   | http/1.1  | Hypertext Transfer   | <a href="./rfc8006">RFC 8006</a>      | <a href="./rfc7230">RFC 7230</a>       |
   |           | Protocol -- HTTP/1.1 |               |                |
   |           |                      |               |                |
   | https/1.1 | HTTP/1.1 over TLS    | <a href="./rfc8006">RFC 8006</a>      | <a href="./rfc7230">RFC 7230</a>,      |
   |           |                      |               | <a href="./rfc2818">RFC 2818</a>       |
   +-----------+----------------------+---------------+----------------+








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<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>.  Security Considerations</span>

<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>.  Authentication and Integrity</span>

   A malicious metadata server, proxy server, or attacker impersonating
   an authentic uCDN CDNI Metadata interface without being detected
   could provide false metadata to a dCDN that either:

   o  Denies service for one or more pieces of content to one or more
      User Agents;

   o  Directs dCDNs to contact malicious origin servers instead of the
      actual origin servers, so that malware or slanderous alternate
      content may be substituted for legitimate content; or

   o  Removes delivery restrictions (e.g., LocationACL, TimeWindowACL,
      ProtocolACL, or Auth metadata), allowing access to content that
      would otherwise be denied and thus possibly violating license
      restrictions and incurring unwarranted delivery costs.

   Unauthorized access to metadata could also enable a malicious
   metadata client to continuously issue metadata requests in order to
   overload a uCDN's metadata server or servers.

   Unauthorized access to metadata could further result in leakage of
   private information.  A malicious metadata client could request
   metadata in order to gain access to origin servers, as well as
   information pertaining to content restrictions.

   An implementation of the CDNI Metadata interface MUST use mutual
   authentication and message authentication codes to prevent
   unauthorized access to, and undetected modification of, metadata (see
   <a href="#section-8.3">Section 8.3</a>).

<span class="h3"><a class="selflink" id="section-8.2" href="#section-8.2">8.2</a>.  Confidentiality and Privacy</span>

   Unauthorized viewing of metadata could result in leakage of private
   information.  Content provider origin and policy information is
   conveyed through the CDNI Metadata interface.  A third party could
   intercept metadata transactions in order to gain access to origin
   servers, as well as information pertaining to content restrictions
   and usage patterns.









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   Note: The distribution of metadata by a uCDN to dCDNs could introduce
   privacy concerns for some content providers, e.g., dCDNs accepting
   content requests for a content provider's content might be able to
   obtain additional information and usage patterns relating to the
   users of a content provider's services.  Content providers with
   concerns about divulging information to dCDNs can instruct their uCDN
   partners not to use CDNI when delivering their content.

   An implementation of the CDNI Metadata interface MUST use strong
   encryption to prevent unauthorized interception or monitoring of
   metadata (see <a href="#section-8.3">Section 8.3</a>).

<span class="h3"><a class="selflink" id="section-8.3" href="#section-8.3">8.3</a>.  Securing the CDNI Metadata Interface</span>

   An implementation of the CDNI Metadata interface MUST support TLS
   transport as per [<a href="./rfc2818" title="&quot;HTTP Over TLS&quot;">RFC2818</a>] and [<a href="./rfc7230" title="&quot;Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing&quot;">RFC7230</a>].

   TLS MUST be used by the server side (uCDN) and the client side (dCDN)
   of the CDNI Metadata interface, including authentication of the
   remote end, unless alternate methods are used for ensuring the
   security of the information in the CDNI Metadata interface requests
   and responses (such as setting up an IPsec tunnel between the two
   CDNs or using a physically secured internal network between two CDNs
   that are owned by the same corporate entity).

   The use of TLS for transport of the CDNI Metadata interface messages
   allows the dCDN and uCDN to authenticate each other.

   Once the dCDN and uCDN have mutually authenticated each other, TLS
   allows:

   o  The dCDN and uCDN to authorize each other (to ensure that they are
      transmitting/receiving CDNI Metadata requests and responses from
      an authorized CDN);

   o  CDNI Metadata interface requests and responses to be transmitted
      with confidentiality; and

   o  The integrity of the CDNI Metadata interface requests and
      responses to be protected during the exchange.

   When TLS is used, the general TLS usage guidance in [<a href="./rfc7525" title="&quot;Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)&quot;">RFC7525</a>] MUST be
   followed.








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<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>.  References</span>

<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>.  Normative References</span>

   [<a id="ref-ISO3166-1">ISO3166-1</a>]
              The International Organization for Standardization,
              "Codes for the representation of names of countries and
              their subdivisions -- Part 1: Country codes",
              ISO 3166-1:2013, 2013.

   [<a id="ref-POSIX">POSIX</a>]    Institute of Electrical and Electronics Engineers,
              "Information Technology Portable Operating System
              Interface (POSIX) Part 1: System Application Program
              Interface (API) [C Language]", IEEE P1003.1, 1990.

   [<a id="ref-RFC1034">RFC1034</a>]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, <a href="./rfc1034">RFC 1034</a>, DOI 10.17487/RFC1034, November 1987,
              &lt;<a href="http://www.rfc-editor.org/info/rfc1034">http://www.rfc-editor.org/info/rfc1034</a>&gt;.

   [<a id="ref-RFC1123">RFC1123</a>]  Braden, R., Ed., "Requirements for Internet Hosts -
              Application and Support", STD 3, <a href="./rfc1123">RFC 1123</a>,
              DOI 10.17487/RFC1123, October 1989,
              &lt;<a href="http://www.rfc-editor.org/info/rfc1123">http://www.rfc-editor.org/info/rfc1123</a>&gt;.

   [<a id="ref-RFC2119">RFC2119</a>]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>,
              DOI 10.17487/RFC2119, March 1997,
              &lt;<a href="http://www.rfc-editor.org/info/rfc2119">http://www.rfc-editor.org/info/rfc2119</a>&gt;.

   [<a id="ref-RFC3986">RFC3986</a>]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              <a href="./rfc3986">RFC 3986</a>, DOI 10.17487/RFC3986, January 2005,
              &lt;<a href="http://www.rfc-editor.org/info/rfc3986">http://www.rfc-editor.org/info/rfc3986</a>&gt;.

   [<a id="ref-RFC4291">RFC4291</a>]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", <a href="./rfc4291">RFC 4291</a>, DOI 10.17487/RFC4291,
              February 2006, &lt;<a href="http://www.rfc-editor.org/info/rfc4291">http://www.rfc-editor.org/info/rfc4291</a>&gt;.

   [<a id="ref-RFC5226">RFC5226</a>]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", <a href="https://www.rfc-editor.org/bcp/bcp26">BCP 26</a>, <a href="./rfc5226">RFC 5226</a>,
              DOI 10.17487/RFC5226, May 2008,
              &lt;<a href="http://www.rfc-editor.org/info/rfc5226">http://www.rfc-editor.org/info/rfc5226</a>&gt;.

   [<a id="ref-RFC5890">RFC5890</a>]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              <a href="./rfc5890">RFC 5890</a>, DOI 10.17487/RFC5890, August 2010,
              &lt;<a href="http://www.rfc-editor.org/info/rfc5890">http://www.rfc-editor.org/info/rfc5890</a>&gt;.




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   [<a id="ref-RFC5891">RFC5891</a>]  Klensin, J., "Internationalized Domain Names in
              Applications (IDNA): Protocol", <a href="./rfc5891">RFC 5891</a>,
              DOI 10.17487/RFC5891, August 2010,
              &lt;<a href="http://www.rfc-editor.org/info/rfc5891">http://www.rfc-editor.org/info/rfc5891</a>&gt;.

   [<a id="ref-RFC5952">RFC5952</a>]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", <a href="./rfc5952">RFC 5952</a>,
              DOI 10.17487/RFC5952, August 2010,
              &lt;<a href="http://www.rfc-editor.org/info/rfc5952">http://www.rfc-editor.org/info/rfc5952</a>&gt;.

   [<a id="ref-RFC6707">RFC6707</a>]  Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", <a href="./rfc6707">RFC 6707</a>, DOI 10.17487/RFC6707,
              September 2012, &lt;<a href="http://www.rfc-editor.org/info/rfc6707">http://www.rfc-editor.org/info/rfc6707</a>&gt;.

   [<a id="ref-RFC7230">RFC7230</a>]  Fielding, R., Ed., and J. Reschke, Ed., "Hypertext
              Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
              <a href="./rfc7230">RFC 7230</a>, DOI 10.17487/RFC7230, June 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7230">http://www.rfc-editor.org/info/rfc7230</a>&gt;.

   [<a id="ref-RFC7493">RFC7493</a>]  Bray, T., Ed., "The I-JSON Message Format", <a href="./rfc7493">RFC 7493</a>,
              DOI 10.17487/RFC7493, March 2015,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7493">http://www.rfc-editor.org/info/rfc7493</a>&gt;.

   [<a id="ref-RFC7525">RFC7525</a>]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", <a href="https://www.rfc-editor.org/bcp/bcp195">BCP 195</a>, <a href="./rfc7525">RFC 7525</a>, DOI 10.17487/RFC7525,
              May 2015, &lt;<a href="http://www.rfc-editor.org/info/rfc7525">http://www.rfc-editor.org/info/rfc7525</a>&gt;.

<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>.  Informative References</span>

   [<a id="ref-CDNI-URI-SIGNING">CDNI-URI-SIGNING</a>]
              van Brandenburg, R., Leung, K., Sorber, P., and M. Miller,
              "URI Signing for CDN Interconnection (CDNI)", Work in
              Progress, <a href="./draft-ietf-cdni-uri-signing-10">draft-ietf-cdni-uri-signing-10</a>, October 2016.

   [<a id="ref-RFC2818">RFC2818</a>]  Rescorla, E., "HTTP Over TLS", <a href="./rfc2818">RFC 2818</a>,
              DOI 10.17487/RFC2818, May 2000,
              &lt;<a href="http://www.rfc-editor.org/info/rfc2818">http://www.rfc-editor.org/info/rfc2818</a>&gt;.

   [<a id="ref-RFC6793">RFC6793</a>]  Vohra, Q. and E. Chen, "BGP Support for Four-Octet
              Autonomous System (AS) Number Space", <a href="./rfc6793">RFC 6793</a>,
              DOI 10.17487/RFC6793, December 2012,
              &lt;<a href="http://www.rfc-editor.org/info/rfc6793">http://www.rfc-editor.org/info/rfc6793</a>&gt;.






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   [<a id="ref-RFC7234">RFC7234</a>]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
              <a href="./rfc7234">RFC 7234</a>, DOI 10.17487/RFC7234, June 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7234">http://www.rfc-editor.org/info/rfc7234</a>&gt;.

   [<a id="ref-RFC7336">RFC7336</a>]  Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
              "Framework for Content Distribution Network
              Interconnection (CDNI)", <a href="./rfc7336">RFC 7336</a>, DOI 10.17487/RFC7336,
              August 2014, &lt;<a href="http://www.rfc-editor.org/info/rfc7336">http://www.rfc-editor.org/info/rfc7336</a>&gt;.

   [<a id="ref-RFC7337">RFC7337</a>]  Leung, K., Ed., and Y. Lee, Ed., "Content Distribution
              Network Interconnection (CDNI) Requirements", <a href="./rfc7337">RFC 7337</a>,
              DOI 10.17487/RFC7337, August 2014,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7337">http://www.rfc-editor.org/info/rfc7337</a>&gt;.

   [<a id="ref-RFC7540">RFC7540</a>]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", <a href="./rfc7540">RFC 7540</a>,
              DOI 10.17487/RFC7540, May 2015,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7540">http://www.rfc-editor.org/info/rfc7540</a>&gt;.

   [<a id="ref-RFC7736">RFC7736</a>]  Ma, K., "Content Delivery Network Interconnection (CDNI)
              Media Type Registration", <a href="./rfc7736">RFC 7736</a>, DOI 10.17487/RFC7736,
              December 2015, &lt;<a href="http://www.rfc-editor.org/info/rfc7736">http://www.rfc-editor.org/info/rfc7736</a>&gt;.

   [<a id="ref-RFC7975">RFC7975</a>]  Niven-Jenkins, B., Ed., and R. van Brandenburg, Ed.,
              "Request Routing Redirection Interface for Content
              Delivery Network (CDN) Interconnection", <a href="./rfc7975">RFC 7975</a>,
              DOI 10.17487/RFC7975, October 2016,
              &lt;<a href="http://www.rfc-editor.org/info/rfc7975">http://www.rfc-editor.org/info/rfc7975</a>&gt;.

   [<a id="ref-RFC8007">RFC8007</a>]  Murray, R. and B. Niven-Jenkins, "Content Delivery Network
              Interconnection (CDNI) Control Interface / Triggers",
              <a href="./rfc8007">RFC 8007</a>, DOI 10.17487/RFC8007, December 2016,
              &lt;<a href="http://www.rfc-editor.org/info/rfc8007">http://www.rfc-editor.org/info/rfc8007</a>&gt;.

   [<a id="ref-RFC8008">RFC8008</a>]  Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
              R., and K. Ma, "Content Delivery Network Interconnection
              (CDNI) Request Routing: Footprint and Capabilities
              Semantics", <a href="./rfc8008">RFC 8008</a>, DOI 10.17487/RFC8008, December 2016,
              &lt;<a href="http://www.rfc-editor.org/info/rfc8008">http://www.rfc-editor.org/info/rfc8008</a>&gt;.











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Acknowledgments

   The authors would like to thank David Ferguson, Francois Le Faucheur,
   Jan Seedorf, and Matt Miller for their valuable comments and input to
   this document.

Contributors

   The authors would also like to thank Grant Watson and Kent Leung for
   their contributions to this document.









































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Authors' Addresses

   Ben Niven-Jenkins
   Nokia
   3 Ely Road
   Milton, Cambridge  CB24 6DD
   United Kingdom

   Email: ben.niven-jenkins@nokia.com


   Rob Murray
   Nokia
   3 Ely Road
   Milton, Cambridge  CB24 6DD
   United Kingdom

   Email: rob.murray@nokia.com


   Matt Caulfield
   Cisco Systems
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   United States of America

   Phone: +1-978-936-9307
   Email: mcaulfie@cisco.com


   Kevin J. Ma
   Ericsson
   43 Nagog Park
   Acton, MA  01720
   United States of America

   Phone: +1 978-844-5100
   Email: kevin.j.ma@ericsson.com













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