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Versions: (draft-ma-cdni-metadata) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 RFC 8006

Network Working Group                                   B. Niven-Jenkins
Internet-Draft                                                 R. Murray
Intended status: Standards Track                Velocix (Alcatel-Lucent)
Expires: March 1, 2017                                      M. Caulfield
                                                           Cisco Systems
                                                                   K. Ma
                                                                Ericsson
                                                         August 28, 2016


                      CDN Interconnection Metadata
                      draft-ietf-cdni-metadata-21

Abstract

   The Content Delivery Networks 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.

Requirements Language

   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 RFC 2119 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

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

   This Internet-Draft will expire on March 1, 2017.





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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 BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
     1.2.  Supported Metadata Capabilities . . . . . . . . . . . . .   5
   2.  Design Principles . . . . . . . . . . . . . . . . . . . . . .   6
   3.  CDNI Metadata object model  . . . . . . . . . . . . . . . . .   7
     3.1.  HostIndex, HostMatch, HostMetadata, PathMatch,
           PatternMatch and PathMetadata objects . . . . . . . . . .   8
     3.2.  Generic CDNI Metadata Objects . . . . . . . . . . . . . .  10
     3.3.  Metadata Inheritance and Override . . . . . . . . . . . .  13
   4.  CDNI Metadata objects . . . . . . . . . . . . . . . . . . . .  14
     4.1.  Definitions of the CDNI structural metadata objects . . .  15
       4.1.1.  HostIndex . . . . . . . . . . . . . . . . . . . . . .  15
       4.1.2.  HostMatch . . . . . . . . . . . . . . . . . . . . . .  15
       4.1.3.  HostMetadata  . . . . . . . . . . . . . . . . . . . .  17
       4.1.4.  PathMatch . . . . . . . . . . . . . . . . . . . . . .  18
       4.1.5.  PatternMatch  . . . . . . . . . . . . . . . . . . . .  19
       4.1.6.  PathMetadata  . . . . . . . . . . . . . . . . . . . .  20
       4.1.7.  GenericMetadata . . . . . . . . . . . . . . . . . . .  21
     4.2.  Definitions of the initial set of CDNI Generic Metadata
           objects . . . . . . . . . . . . . . . . . . . . . . . . .  23
       4.2.1.  SourceMetadata  . . . . . . . . . . . . . . . . . . .  23
         4.2.1.1.  Source  . . . . . . . . . . . . . . . . . . . . .  24
       4.2.2.  LocationACL Metadata  . . . . . . . . . . . . . . . .  25
         4.2.2.1.  LocationRule  . . . . . . . . . . . . . . . . . .  27
         4.2.2.2.  Footprint . . . . . . . . . . . . . . . . . . . .  27
       4.2.3.  TimeWindowACL . . . . . . . . . . . . . . . . . . . .  29
         4.2.3.1.  TimeWindowRule  . . . . . . . . . . . . . . . . .  30
         4.2.3.2.  TimeWindow  . . . . . . . . . . . . . . . . . . .  31
       4.2.4.  ProtocolACL Metadata  . . . . . . . . . . . . . . . .  31
         4.2.4.1.  ProtocolRule  . . . . . . . . . . . . . . . . . .  32
       4.2.5.  DeliveryAuthorization Metadata  . . . . . . . . . . .  33



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       4.2.6.  Cache . . . . . . . . . . . . . . . . . . . . . . . .  34
       4.2.7.  Auth  . . . . . . . . . . . . . . . . . . . . . . . .  36
       4.2.8.  Grouping  . . . . . . . . . . . . . . . . . . . . . .  37
     4.3.  CDNI Metadata Simple Data Type Descriptions . . . . . . .  37
       4.3.1.  Link  . . . . . . . . . . . . . . . . . . . . . . . .  37
         4.3.1.1.  Link Loop Prevention  . . . . . . . . . . . . . .  39
       4.3.2.  Protocol  . . . . . . . . . . . . . . . . . . . . . .  39
       4.3.3.  Endpoint  . . . . . . . . . . . . . . . . . . . . . .  39
       4.3.4.  Time  . . . . . . . . . . . . . . . . . . . . . . . .  40
       4.3.5.  IPv4CIDR  . . . . . . . . . . . . . . . . . . . . . .  40
       4.3.6.  IPv6CIDR  . . . . . . . . . . . . . . . . . . . . . .  40
       4.3.7.  ASN . . . . . . . . . . . . . . . . . . . . . . . . .  41
       4.3.8.  CountryCode . . . . . . . . . . . . . . . . . . . . .  41
   5.  CDNI Metadata Capabilities  . . . . . . . . . . . . . . . . .  41
   6.  CDNI Metadata interface . . . . . . . . . . . . . . . . . . .  42
     6.1.  Transport . . . . . . . . . . . . . . . . . . . . . . . .  42
     6.2.  Retrieval of CDNI Metadata resources  . . . . . . . . . .  43
     6.3.  Bootstrapping . . . . . . . . . . . . . . . . . . . . . .  44
     6.4.  Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  44
     6.5.  Extensibility . . . . . . . . . . . . . . . . . . . . . .  45
     6.6.  Metadata Enforcement  . . . . . . . . . . . . . . . . . .  46
     6.7.  Metadata Conflicts  . . . . . . . . . . . . . . . . . . .  46
     6.8.  Versioning  . . . . . . . . . . . . . . . . . . . . . . .  47
     6.9.  Media Types . . . . . . . . . . . . . . . . . . . . . . .  48
     6.10. Complete CDNI Metadata Example  . . . . . . . . . . . . .  48
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  52
     7.1.  CDNI Payload Types  . . . . . . . . . . . . . . . . . . .  52
       7.1.1.  CDNI MI HostIndex Payload Type  . . . . . . . . . . .  53
       7.1.2.  CDNI MI HostMatch Payload Type  . . . . . . . . . . .  53
       7.1.3.  CDNI MI HostMetadata Payload Type . . . . . . . . . .  54
       7.1.4.  CDNI MI PathMatch Payload Type  . . . . . . . . . . .  54
       7.1.5.  CDNI MI PatternMatch Payload Type . . . . . . . . . .  54
       7.1.6.  CDNI MI PathMetadata Payload Type . . . . . . . . . .  54
       7.1.7.  CDNI MI SourceMetadata Payload Type . . . . . . . . .  54
       7.1.8.  CDNI MI Source Payload Type . . . . . . . . . . . . .  55
       7.1.9.  CDNI MI LocationACL Payload Type  . . . . . . . . . .  55
       7.1.10. CDNI MI LocationRule Payload Type . . . . . . . . . .  55
       7.1.11. CDNI MI Footprint Payload Type  . . . . . . . . . . .  55
       7.1.12. CDNI MI TimeWindowACL Payload Type  . . . . . . . . .  55
       7.1.13. CDNI MI TimeWindowRule Payload Type . . . . . . . . .  56
       7.1.14. CDNI MI TimeWindow Payload Type . . . . . . . . . . .  56
       7.1.15. CDNI MI ProtocolACL Payload Type  . . . . . . . . . .  56
       7.1.16. CDNI MI ProtocolRule Payload Type . . . . . . . . . .  56
       7.1.17. CDNI MI DeliveryAuthorization Payload Type  . . . . .  56
       7.1.18. CDNI MI Cache Payload Type  . . . . . . . . . . . . .  57
       7.1.19. CDNI MI Auth Payload Type . . . . . . . . . . . . . .  57
       7.1.20. CDNI MI Grouping Payload Type . . . . . . . . . . . .  57
     7.2.  CDNI Metadata Footprint Types Registry  . . . . . . . . .  57



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     7.3.  CDNI Metadata Protocol Types Registry . . . . . . . . . .  58
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  58
     8.1.  Authentication and Integrity  . . . . . . . . . . . . . .  59
     8.2.  Confidentiality and Privacy . . . . . . . . . . . . . . .  59
     8.3.  Securing the CDNI Metadata interface  . . . . . . . . . .  60
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  60
   10. Contributing Authors  . . . . . . . . . . . . . . . . . . . .  60
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  61
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  61
     11.2.  Informative References . . . . . . . . . . . . . . . . .  63
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  64

1.  Introduction

   Content Delivery Networks Interconnection (CDNI) [RFC6707] enables a
   downstream Content Delivery Network (dCDN) to service content
   requests on behalf of an upstream CDN (uCDN).

   The CDNI metadata interface is discussed in [RFC7336] along with four
   other interfaces that can be used to compose a CDNI solution (CDNI
   Control interface, CDNI Request Routing Redirection interface, CDNI
   Footprint & Capabilities Advertisement interface and CDNI Logging
   interface).  [RFC7336] describes each interface and the relationships
   between them.  The requirements for the CDNI metadata interface are
   specified in [RFC7337].

   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 an uCDN, in accordance with the
   policies defined by the uCDN.

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

   o  Redirection requests received over the CDNI Request Routing
      Redirection interface [I-D.ietf-cdni-redirection].

   o  Content requests received directly from User Agents.

   Specifically, this document specifies:

   o  A data structure for mapping content requests and redirection
      requests to CDNI metadata objects (Section 3 and Section 4.1).

   o  An initial set of CDNI Generic metadata objects (Section 4.2).

   o  A HTTP web service for the transfer of CDNI metadata (Section 6).



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1.1.  Terminology

   This document reuses the terminology defined in [RFC6707].

   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.

   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".

1.2.  Supported Metadata Capabilities

   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 [RFC7337].

   The following high-level functionality can be configured via the CDNI
   metadata objects specified in Section 4:

   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.





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   The set of metadata specified in this document covers the initial
   capabilities above.  It is only intended to support CDN
   interconnection for the delivery of content by a dCDN using HTTP/1.1
   [RFC7230] and for a dCDN to be able to acquire content from a uCDN
   using either HTTP/1.1 or HTTP/1.1 over TLS [RFC2818].

   Supporting CDN interconnection for the delivery of content using
   unencrypted HTTP/2 [RFC7540] (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 Section 7.3.

   Delivery of content using HTTP/1.1 over TLS or HTTP/2 over TLS SHOULD
   follow the guidelines set forth in [RFC7525].  Offline configuration
   of TLS parameters between CDNs is beyond the scope of this document.

2.  Design Principles

   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 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 mappings 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 and DNS based
   redirection schemes.





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   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 [RFC7493]) and
   data transport (by leveraging HTTP [RFC7230]).

3.  CDNI Metadata object model

   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 an 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
   behaviour 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 Hostname 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



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   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.

   Section 3.1 introduces a high level description of the HostIndex,
   HostMatch, HostMetadata, PathMatch, PatternMatch and PathMetadata
   objects, and describes the relationships between them.

   Section 3.2 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.

   Section 4 describes in detail the specific CDNI metadata objects and
   properties specified by this document which can be contained within a
   CDNI GenericMetadata object.

3.1.  HostIndex, HostMatch, HostMetadata, PathMatch, PatternMatch and
      PathMetadata objects

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

   +---------+      +---------+      +------------+
   |HostIndex+-(*)->|HostMatch+-(1)->|HostMetadata+-------(*)------+
   +---------+      +---------+      +------+-----+                |
                                            |                      |
                                           (*)                     |
                                            |                      V
   --> Contains or References               V         ******************
   (1) One and only one                +---------+    *Generic Metadata*
   (*) Zero or more               +--->|PathMatch|    *     Objects    *
                                  |    +----+---++    ******************
                                  |         |   |                  ^
                                 (*)       (1) (1) +------------+  |
                                  |         |   +->|PatternMatch|  |
                                  |         V      +------------+  |
                                  |  +------------+                |
                                  +--+PathMetadata+-------(*)------+
                                     +------------+

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





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   A HostIndex object (see Section 4.1.1) contains an array of HostMatch
   objects (see Section 4.1.2) 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.

   The HostIndex links Hostnames (and/or IP addresses) to HostMetadata
   objects (see Section 4.1.3) 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
   Section 4.1.7) 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
   Section 4.1.6), via PathMatch objects (see Section 4.1.4).  PathMatch
   objects define patterns, contained inside PatternMatch objects (see
   Section 4.1.5), to match against the requested URI path.
   PatternMatch objects contain the pattern strings and flags that
   describe the URI path that a PathMatch applies to.  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
   which 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 which 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 which apply to that
   URI path.  It could also contain a PathMatch object for



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   "example.com/movies/hd/*" which would reference the corresponding
   PathMetadata object for the "example.com/movies/hd/" path prefix.

   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)

3.2.  Generic CDNI Metadata Objects

   The HostMetadata and PathMetadata objects contain other CDNI metadata
   objects that contain properties which 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.

   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 to another CDN without
   modification.  For example, in the cascaded CDN case, a transit CDN
   (tCDN) could pass through "mandatory-to-enforce" metadata to a dCDN.



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   For metadata which 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 transit CDN.  However,
   for metadata which 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, 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 transit CDN.  A CDN MUST NOT attempt to use metadata that has
   been marked as "incomprehensible" by a uCDN.

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

   Table 2 describes the action to be taken by a transit CDN (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:






















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   +-------+-------+------------+--------------------------------------+
   | 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

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















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   +-------+--------+--------------+-----------------------------------+
   | 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 incomprehensible.          |
   | False | False  | False        | Can serve.                        |
   | False | True   | False        | Can serve but MUST NOT            |
   |       |        |              | interpret/apply any metadata      |
   |       |        |              | marked 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

3.3.  Metadata Inheritance and Override

   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
   HostMetadata for the host "example.com" contains GenericMetadata
   objects of type LocationACL and TimeWindowACL, while a PathMetadata
   object which 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/".




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   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.

4.  CDNI Metadata objects

   Section 4.1 provides the definitions of each metadata object type
   introduced in Section 3.  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.

   Section 4.2 provides the definitions for a base set of core metadata
   objects which 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
   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.

   Section 6.5 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 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
   need in order to express the policies required by the content they
   are describing.  See Section 6.4 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, e.g., a HostMatch
   property object without a host to match against does not make sense,




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   therefore, the host property is mandatory-to-specify inside a
   HostMatch object.

4.1.  Definitions of the CDNI structural metadata objects

   Each of the sub-sections below describe the structural objects
   introduced in Section 3.1.

4.1.1.  HostIndex

   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 which 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.

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

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

4.1.2.  HostMatch

   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.



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      Property: host

         Description: Hostname or IP address and optional port to match
         against the requested host, i.e., the [RFC3986] host and port.
         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 Section 3.2.2
         of [RFC3986].  IPv6 addresses MUST be encoded in one of the
         IPv6 address formats specified in [RFC5952] although receivers
         MUST support all IPv6 address formats specified in [RFC4291].
         Hostnames MUST conform to the Domain Name System (DNS) syntax
         defined in [RFC1034] and [RFC1123].  Internationalized Domain
         Names (IDN) must first be transformed to the the A-label form
         [RFC5890] as per [RFC5891].

         Type: Endpoint

         Mandatory-to-Specify: Yes.

      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" : {
       <Properties of embedded HostMetadata object>
     }
   }

   Example HostMatch object referencing (via a Link object, see
   Section 4.3.1) a HostMetadata object:









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

4.1.3.  HostMetadata

   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.

      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.

   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:













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   {
     "metadata": [
       {
         <Properties of 1st embedded GenericMetadata object>
       },
       {
         <Properties of 2nd embedded GenericMetadata object>
       },

    ...

       {
         <Properties of Nth embedded GenericMetadata object>
       }
     ],
     "paths": [
       {
         <Properties of embedded PathMatch object>
       }
     ]
   }

4.1.4.  PathMatch

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

      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.




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   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": "https://metadata.ucdn.example/host1234/pathDCE"
     }
   }

4.1.5.  PatternMatch

   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 [RFC3986] path-absolute.  The pattern can contain
         the wildcards * and ?, where * matches any sequence of
         [RFC3986] pchar or "/" characters (including the empty string)
         and ? matches exactly one [RFC3986] pchar character.  The three
         literals $, * and ? MUST be escaped as $$, $* and $? (where $
         is the designated escape character).  All other characters are
         treated as literals.

         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
         [RFC3986].

         Type: Boolean

         Mandatory-to-Specify: No.  Default is case-insensitive match.

   Example PatternMatch object that matches the case-sensitive URI path
   pattern "/movies/*".  All query parameters will be ignored when



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   matching URIs requested from surrogates by content clients against
   this path pattern:

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

   Example PatternMatch object that matches the case-sensitive URI path
   pattern "/movies/*".  Only the query parameter "sessionid" will be
   evaluated when matching URIs requested from surrogates by content
   clients against this path pattern:

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

4.1.6.  PathMetadata

   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.

      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.



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         Type: Array of PathMatch objects

         Mandatory-to-Specify: No.

   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": [
       {
         <Properties of 1st embedded GenericMetadata object>
       },
       {
         <Properties of 2nd embedded GenericMetadata object>
       },

    ...

       {
         <Properties of Nth embedded GenericMetadata object>
       }
     ],
     "paths": [
       {
         <Properties of embedded PathMatch object>
       }
     ]
   }

4.1.7.  GenericMetadata

   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 [RFC7736] of the
         object contained in the generic-metadata-value property (see
         Table 4).

         Mandatory-to-Specify: Yes.

      Property: generic-metadata-value




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         Description: CDNI metadata object.

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

         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 allow transparent
         redistribution (i.e., a value of True).

      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):







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

4.2.  Definitions of the initial set of CDNI Generic Metadata objects

   The objects defined below are intended to be used in the
   GenericMetadata object generic-metadata-value field as defined in
   Section 4.1.7 and their generic-metadata-type property MUST be set to
   the appropriate CDNI Payload Type as defined in Table 4.

4.2.1.  SourceMetadata

   Source metadata provides the dCDN with information about content
   acquisition, i.e., how to contact an 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 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.

         Type: Array of Source objects (see Section 4.2.1.1)

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












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   {
     "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"
           }
         ]
       }
   }

4.2.1.1.  Source

   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 in preference order within a
   SourceMetadata object, and then for each preference ranked Source
   object, 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.

         Type: Auth (see Section 4.2.7)

         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.,




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         the list is not in preference order (e.g., a pool of servers
         behind a load balancer).

         Type: Array of Endpoint objects (See Section 4.3.3)

         Mandatory-to-Specify: Yes.

      Property: protocol

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

         Type: Protocol (see Section 4.3.2)

         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"
   }

4.2.2.  LocationACL Metadata

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

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

   Although the LocationACL, TimeWindowACL (see Section 4.2.3), and
   ProtocolACL (see Section 4.2.4) are independent GenericMetadata
   objects, they can provide conflicting information to a dCDN, e.g., a
   content request which is simultaneously allowed based on the
   LocationACL and denied based on the TimeWindowACL.  The dCDN MUST use



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   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: Access control list which allows or denies
         (blocks) delivery based on the User Agent's location.

         Type: Array of LocationRule objects (see Section 4.2.2.1)

         Mandatory-to-Specify: No.  Default is 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":
       {
       }
   }

   Example LocationACL object (which contains a LocationRule object
   which itself 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"]
               }
             ]
           }
         ]
       }
   }








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4.2.2.1.  LocationRule

   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 Section 4.2.2.2)

         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.

   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"]
       }
     ]
   }

4.2.2.2.  Footprint

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

      Property: footprint-type

         Description: Registered footprint type (see Section 7.2).  The
         footprint types specified by this document are: "ipv4cidr"
         (IPv4CIDR, see Section 4.3.5), "ipv6cidr" (IPv6CIDR, see
         Section 4.3.6), "asn" (Autonomous System Number, see




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         Section 4.3.7) and "countrycode" (Country Code, see
         Section 4.3.8).

         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 CountryCode), 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.

   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:






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

4.2.3.  TimeWindowACL

   TimeWindowACL metadata defines time-based restrictions.

   A TimeWindowACL which 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 matches the current time, then the result is an
   action of deny.

   Although the LocationACL (see Section 4.2.2), TimeWindowACL, and
   ProtocolACL (see Section 4.2.4) are independent GenericMetadata
   objects, they can provide conflicting information to a dCDN, e.g., a
   content request which 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: Access control list which allows or denies
         (blocks) delivery based on the time of a User Agent's request.

         Type: Array of TimeWindowRule objects (see Section 4.2.3.1)

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

   Example TimeWIndowACL object (which contains a TimeWindowRule object
   which itself 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:











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

4.2.3.1.  TimeWindowRule

   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 Section 4.2.3.2)

         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:








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

4.2.3.2.  TimeWindow

   A TimeWindow object describes a time range which can be applied by an
   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 Section 4.3.4)

         Mandatory-to-Specify: Yes.

      Property: end

         Description: The end time of the window.

         Type: Time (see Section 4.3.4)

         Mandatory-to-Specify: Yes.

   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
   }

4.2.4.  ProtocolACL Metadata

   ProtocolACL metadata defines delivery protocol restrictions.

   A ProtocolACL which 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



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   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 protocol matches the request
   protocol, then the result is an action of deny.

   Although the LocationACL, TimeWindowACL, and ProtocolACL are
   independent GenericMetadata objects, they can provide conflicting
   information to a dCDN, e.g., a content request which 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: Description: Access control list which allows or
         denies (blocks) delivery based on delivery protocol.

         Type: Array of ProtocolRule objects (see Section 4.2.4.1)

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

   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"]
           }
         ]
       }
   }

4.2.4.1.  ProtocolRule

   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.




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         Type: Array of Protocols (see Section 4.3.2)

         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 ProtocolRule object)
   that allows the dCDN to deliver content using HTTP/1.1:

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

4.2.5.  DeliveryAuthorization Metadata

   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 of the
         authorization methods in the list is satisfied for that
         request.

         Type: Array of Auth objects (see Section 4.2.7)

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

   Example DeliveryAuthorization object (which contains an Auth object):












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

4.2.6.  Cache

   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
   [RFC7234].  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.

      Property: exclude-path-pattern

         Description: A pattern for matching against the URI path, i.e.,
         against the [RFC3986] path-absolute.  The pattern can contain
         the wildcards * and ?, where * matches any sequence of
         [RFC3986] pchar or "/" characters (including the empty string)
         and ? matches exactly one [RFC3986] 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 Section 4.1.5 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



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         Description: Allows a Surrogate to specify the URI query string
         parameters [RFC3986] 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 String

         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": []
     }
   }

   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:









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

4.2.7.  Auth

   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
   [I-D.ietf-cdni-uri-signing]).  The GenericMetadata which contain 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 [RFC7736] 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.

         Type: GenericMetadata Object

         Mandatory-to-Specify: Yes.

   Example Auth object:













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   {
     "generic-metadata-type": "MI.Auth",
     "generic-metadata-value":
     {
       "auth-type": <CDNI Payload Type of this Auth object>,
       "auth-value":
         {
           <Properties of this Auth object>
         }
     }
   }

4.2.8.  Grouping

   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 an empty string.

   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"
     }
   }

4.3.  CDNI Metadata Simple Data Type Descriptions

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

4.3.1.  Link

   A Link object can be used in place of any of the objects or
   properties described above.  Link objects can be used to avoid
   duplication if the same metadata information is repeated within the



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   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": "https://metadata.ucdn.example/hostmatch1234"
   }

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










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   {
     "hosts": [
       {
         <Properties of embedded HostMatch object>
       },
       {
         "href": "https://metadata.ucdn.example/hostmatch1234"
       }
     ]
   }

4.3.1.1.  Link Loop Prevention

   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.  For GenericMetadata
   objects, type checks will prevent self references; however, incorrect
   linking can result in circular references for structural metadtata
   objects, specifically, PathMatch and PathMetadata objects Figure 1.
   To prevent the circular references, CDNI metadata clients SHOULD
   verify that no duplicate Links occur for PathMatch or PathMetadata
   objects.

4.3.2.  Protocol

   Protocol objects are used to specify registered protocols for content
   acquisition or delivery (see Section 7.3).

   Type: String

   Example:

   "http/1.1"

4.3.3.  Endpoint

   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 Section 3.2.2 of [RFC3986].  IPv6
   addresses MUST be encoded in one of the IPv6 address formats
   specified in [RFC5952] although receivers MUST support all IPv6
   address formats specified in [RFC4291].  Hostnames MUST conform to
   the Domain Name System (DNS) syntax defined in [RFC1034] and
   [RFC1123].  Internationalized Domain Names (IDN) must first be
   transformed to the A-label form [RFC5890] as per [RFC5891].




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   Type: String

   Example Hostname:

   "metadata.ucdn.example"

   Example IPv4 address:

   "192.0.2.1"

   Example IPv6 address (with port number):

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

4.3.4.  Time

   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) [POSIX].

   Type: Integer

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

   946717200

4.3.5.  IPv4CIDR

   An IPv4address CIDR block encoded as specified by the 'IPv4address'
   rule in Section 3.2.2 of [RFC3986] 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 IPv4 CIDR:

   "192.0.2.0/24"

4.3.6.  IPv6CIDR

   An IPv6address CIDR block encoded in one of the IPv6 address formats
   specified in [RFC5952] 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



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   Example IPv6 CIDR:

   "2001:db8::/32"

4.3.7.  ASN

   An Autonomous System Number encoded as a string consisting of the
   characters "as" (in lowercase) followed by the Autonomous System
   number [RFC6793].

   Type: String

   Example ASN:

   "as64496"

4.3.8.  CountryCode

   An ISO 3166-1 alpha-2 code [ISO3166-1] in lowercase.

   Type: String

   Example Country Code representing the USA:

   "us"

5.  CDNI Metadata Capabilities

   CDNI metadata is used to convey information pertaining to content
   delivery from uCDN to dCDN.  For optional metadata, it can be useful
   for the uCDN to know if the dCDN supports the underlying
   functionality described by the metadata, prior to delegating any
   content requests to the dCDN.  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 which might be assigned optional values,
   it could be useful for the uCDN to know which values a dCDN supports,
   prior to delegating any content requests to that dCDN.  If the
   optional value assigned to a given piece of content's metadata is not
   supported by 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 and Capabilities Interface (FCI) provides a means
   of advertising capabilities from dCDN to uCDN [RFC7336].  Support for
   optional metadata types and values can be advertised using the FCI.




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6.  CDNI Metadata interface

   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
   either:

   o  Dynamically as required by the dCDN to process received requests.
      For example in response to a query from an uCDN over the CDNI
      Request Routing Redirection interface (RI)
      [I-D.ietf-cdni-redirection] or in response to receiving a request
      for content from a User Agent.  Or;

   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
      [I-D.ietf-cdni-control-triggers].

   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
   Section 3 and Section 4).

   To retrieve CDNI metadata, a CDNI metadata client (i.e., a client in
   the dCDN) first makes a HTTP GET request for the URI of the HostIndex
   which provides the CDNI metadata client with an array of Hostnames
   for which the uCDN can delegate content delivery to the dCDN.  The
   CDNI metadata client can then obtain any other CDNI metadata objects
   by making a HTTP GET requests for any linked metadata objects it
   requires.

   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.  Therefore 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.

6.1.  Transport

   The CDNI metadata interface uses HTTP as the underlying protocol
   transport [RFC7230].




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   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 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.

6.2.  Retrieval of CDNI Metadata resources

   In the general case, a CDNI metadata server makes CDNI metadata
   objects available via a unique URIs and thus, in order to retrieve
   CDNI metadata, a CDNI metadata client first makes a 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 a 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-patterns in any PathMatch
   objects listed in the HostMetadata object).  If any PathMetadata are
   found to match (and are linked rather than embedded), the CDNI
   metadata client makes another GET request for the PathMetadata.  Each
   PathMetadata object can also include references to yet 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 an uCDN or the content request from a User Agent.



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   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 a 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 should be used to handle a
   particular User Agent request.

   When application level 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) and therefore dCDNs will have to apply local policy when
   deciding which uCDN's metadata to apply.

6.3.  Bootstrapping

   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.

6.4.  Encoding

   CDNI metadata objects MUST be encoded as I-JSON objects [RFC7493]
   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



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   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.

6.5.  Extensibility

   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 Section 4.1.7 specifies a type field and a type-
   specific value field that allows any metadata to be included in
   either the HostMetadata or PathMetadata arrays.

   As with the initial GenericMetadata types defined in Section 4.2,
   future GenericMetadata types MUST specify the information necessary
   for constructing and decoding the GenericMetadata object.

   Any document which defines a new GenericMetadata type MUST:

   1.  Specify and register the CDNI Payload Type [RFC7736] 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 Section 4.3.1).

   3.  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
       example of a use case to which it applies including an example
       encoded in I-JSON.

   5.  Describe the security and privacy consequences, for both the
       user-agent and the CDN, 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.



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6.6.  Metadata Enforcement

   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 mis-
   communication, mis-configuration, 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.

6.7.  Metadata Conflicts

   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
   "mandatory-to-enforce", it could be ambiguous which metadata should
   be applied, especially if the functionality of the metadata overlap.

   As described in Section 3.3, 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 metadata 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.



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6.8.  Versioning

   The version of CDNI metadata objects is conveyed inside the CDNI
   Payload Type that is included in either the HTTP Content-Type header,
   for example: "Content-Type: application/cdni; ptype=MI.HostIndex",
   when retrieved via a link, or in the link type (Section 4.3.1),
   generic-metadata-type (Section 4.1.7), or auth-type (Section 4.2.7)
   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, e.g., MI.HostIndex.v2, MI.HostIndex.v3, etc.

   Except when referenced by a Link object, nested metadata objects
   (i.e., structural metadata below the HostIndex; Source objects;
   Location, TimeWindow, and Protocol Rule objects; and 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, generic metadata, 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, which each 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 MI.HostIndex.v2 and MI.HostMatch.v2, respectively.  Similarly, if
   a new MI.TimeWindowRule.v2 object was required, the outer
   MI.TimeWindowACL object would need to be revised, e.g., to
   MI.TimeWindowACL.v2; the MI.TimeWindowRule.v2 object, though, 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.








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6.9.  Media Types

   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 Type 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

6.10.  Complete CDNI Metadata Example

   A dCDN requests the HostIndex and receive the following object with a
   CDNI payload type of "MI.HostIndex":












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

   If the incoming request has a Host header with "video.example.com"
   then the dCDN would fetch the HostMetadata object from
   "https://metadata.ucdn.example/host1234" 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"
             }
           ]
         }
       },
       {
         "generic-metadata-type": "MI.LocationACL",
         "generic-metadata-value": {
           "locations": [
             {
               "footprints": [
                 {



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                   "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"
             }
           ]
         }
       }
     ],
     "paths": [
       {
         "path-pattern": {
           "pattern": "/video/trailers/*"
         },
         "path-metadata": {
           "type": "MI.PathMetadata",
           "href": "https://metadata.ucdn.example/host1234/pathABC"
         }
       },
       {
         "path-pattern": {
           "pattern": "/video/movies/*"



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         },
         "path-metadata": {
           "type": "MI.PathMetadata",
           "href": "https://metadata.ucdn.example/host1234/pathDEF"
         }
       }
     ]
   }

   Suppose the path of the requested resource matches the "/video/
   movies/*" pattern, the next metadata requested would be for
   "https://metadata.ucdn.example/host1234/pathDCE" with an expected
   CDNI payload type of "MI.PathMetadata":

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

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
















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   {
     "metadata": [
       {
         "generic-metadata-type": "MI.TimeWindowACL",
         "generic-metadata-value": {
           "times": [
             "windows": [
               {
                 "start": "1213948800",
                 "end": "1327393200"
               }
             ],
             "action": "allow"
           ]
         }
       }
     ]
   }

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

7.  IANA Considerations

7.1.  CDNI Payload Types

   This document requests the registration of the following CDNI Payload
   Types under the IANA CDNI Payload Type registry:






















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

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]

7.1.1.  CDNI MI HostIndex Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.1.1

7.1.2.  CDNI MI HostMatch Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.1.2






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7.1.3.  CDNI MI HostMetadata Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.1.3

7.1.4.  CDNI MI PathMatch Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.1.4

7.1.5.  CDNI MI PatternMatch Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.1.5

7.1.6.  CDNI MI PathMetadata Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.1.6

7.1.7.  CDNI MI SourceMetadata Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.1






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7.1.8.  CDNI MI Source Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.1.1

7.1.9.  CDNI MI LocationACL Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.2

7.1.10.  CDNI MI LocationRule Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.2.1

7.1.11.  CDNI MI Footprint Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.2.2

7.1.12.  CDNI MI TimeWindowACL Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.3






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7.1.13.  CDNI MI TimeWindowRule Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.3.1

7.1.14.  CDNI MI TimeWindow Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.3.2

7.1.15.  CDNI MI ProtocolACL Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.4

7.1.16.  CDNI MI ProtocolRule Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.4.1

7.1.17.  CDNI MI DeliveryAuthorization Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.5





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7.1.18.  CDNI MI Cache Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.6

7.1.19.  CDNI MI Auth Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.7

7.1.20.  CDNI MI Grouping Payload Type

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

   Interface: MI/FCI

   Encoding: see Section 4.2.8

7.2.  CDNI Metadata Footprint Types Registry

   The IANA is requested to create a new "CDNI Metadata Footprint Types"
   subregistry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" registry.  The "CDNI Metadata Footprint Types" namespace
   defines the valid Footprint object type values used by the Footprint
   object in Section 4.2.2.2.  Additions to the Footprint type namespace
   conform to the "Specification Required" policy as defined in
   [RFC5226].  The designated expert will verify that new type
   definitions do not duplicate existing type definitions 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 Footprint Registry values:









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    +----------------+-------------------------------+---------------+
    | Footprint Type | Description                   | Specification |
    +----------------+-------------------------------+---------------+
    | ipv4cidr       | IPv4 CIDR address block       | RFCthis       |
    | ipv6cidr       | IPv6 CIDR address block       | RFCthis       |
    | asn            | Autonomous System (AS) Number | RFCthis       |
    | countrycode    | ISO 3166-1 alpha-2 code       | RFCthis       |
    +----------------+-------------------------------+---------------+

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]

7.3.  CDNI Metadata Protocol Types Registry

   The IANA is requested to create a new "CDNI Metadata Protocol Types"
   subregistry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" registry.  The "CDNI Metadata Protocol Types" namespace
   defines the valid Protocol object values in Section 4.3.2, used by
   the SourceMetadata and ProtocolACL objects.  Additions to the
   Protocol namespace conform to the "Specification Required" policy as
   defined in [RFC5226], 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   | RFCthis       | RFC7230        |
   |           | Protocol -- HTTP/1.1 |               |                |
   | https/1.1 | HTTP/1.1 Over TLS    | RFCthis       | RFC7230,       |
   |           |                      |               | RFC2818        |
   +-----------+----------------------+---------------+----------------+

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]

8.  Security Considerations








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8.1.  Authentication and Integrity

   A malicious metadata server, proxy server, or attacker, impersonating
   an authentic uCDN 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, and substitute legitimate content with
      malware or slanderous alternate 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(s).

   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
   Section 8.3).

8.2.  Confidentiality and Privacy

   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.

   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.



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   An implementation of the CDNI metadata interface MUST use strong
   encryption to prevent unauthorized interception or monitoring of
   metadata (see Section 8.3).

8.3.  Securing the CDNI Metadata interface

   An implementation of the CDNI metadata interface MUST support TLS
   transport as per [RFC2818] and [RFC7230].

   TLS MUST be used by the server-side (dCDN) and the client-side (uCDN)
   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:

   o  The dCDN and uCDN to authenticate each other.

   and, once they have mutually authenticated each other, it allows:

   o  The dCDN and uCDN to authorize each other (to ensure 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 [RFC7525] MUST be
   followed.

9.  Acknowledgements

   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.

10.  Contributing Authors

   [RFC Editor Note: Please move the contents of this section to the
   Authors' Addresses section prior to publication as an RFC.]




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   Grant Watson
   Velocix (Alcatel-Lucent)
   3 Ely Road
   Milton, Cambridge  CB24 6AA
   UK

   Email: gwatson@velocix.com

   Kent Leung
   Cisco Systems
   3625 Cisco Way
   San Jose, 95134
   USA

   Email: kleung@cisco.com

11.  References

11.1.  Normative References

   [ISO3166-1]
              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.

   [POSIX]    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.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <http://www.rfc-editor.org/info/rfc1034>.

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

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.







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

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <http://www.rfc-editor.org/info/rfc4291>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

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

   [RFC5891]  Klensin, J., "Internationalized Domain Names in
              Applications (IDNA): Protocol", RFC 5891,
              DOI 10.17487/RFC5891, August 2010,
              <http://www.rfc-editor.org/info/rfc5891>.

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

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

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

   [RFC7493]  Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
              DOI 10.17487/RFC7493, March 2015,
              <http://www.rfc-editor.org/info/rfc7493>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <http://www.rfc-editor.org/info/rfc7525>.



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11.2.  Informative References

   [I-D.ietf-cdni-control-triggers]
              Murray, R. and B. Niven-Jenkins, "CDNI Control Interface /
              Triggers", draft-ietf-cdni-control-triggers-15 (work in
              progress), May 2016.

   [I-D.ietf-cdni-redirection]
              Niven-Jenkins, B. and R. Brandenburg, "Request Routing
              Redirection interface for CDN Interconnection", draft-
              ietf-cdni-redirection-20 (work in progress), August 2016.

   [I-D.ietf-cdni-uri-signing]
              Leung, K., Faucheur, F., Brandenburg, R., Downey, B., and
              M. Fisher, "URI Signing for CDN Interconnection (CDNI)",
              draft-ietf-cdni-uri-signing-09 (work in progress), June
              2016.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,
              <http://www.rfc-editor.org/info/rfc2818>.

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

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

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

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

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





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

Authors' Addresses

   Ben Niven-Jenkins
   Velocix (Alcatel-Lucent)
   3 Ely Road
   Milton, Cambridge  CB24 6AA
   UK

   Email: ben@velocix.com


   Rob Murray
   Velocix (Alcatel-Lucent)
   3 Ely Road
   Milton, Cambridge  CB24 6AA
   UK

   Email: rmurray@velocix.com


   Matt Caulfield
   Cisco Systems
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   USA

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


   Kevin J. Ma
   Ericsson
   43 Nagog Park
   Acton, MA  01720
   USA

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









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