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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: April 21, 2016                                     M. Caulfield
                                                           Cisco Systems
                                                                   K. Ma
                                                                Ericsson
                                                        October 19, 2015


                      CDN Interconnection Metadata
                      draft-ietf-cdni-metadata-12

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 April 21, 2016.





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Copyright Notice

   Copyright (c) 2015 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 . . . . . . . . . . . . . .  11
     3.3.  Metadata Inheritance and Override . . . . . . . . . . . .  14
   4.  CDNI Metadata objects . . . . . . . . . . . . . . . . . . . .  15
     4.1.  Definitions of the CDNI structural metadata objects . . .  16
       4.1.1.  HostIndex . . . . . . . . . . . . . . . . . . . . . .  16
       4.1.2.  HostMatch . . . . . . . . . . . . . . . . . . . . . .  17
       4.1.3.  HostMetadata  . . . . . . . . . . . . . . . . . . . .  18
       4.1.4.  PathMatch . . . . . . . . . . . . . . . . . . . . . .  19
       4.1.5.  PatternMatch  . . . . . . . . . . . . . . . . . . . .  20
       4.1.6.  PathMetadata  . . . . . . . . . . . . . . . . . . . .  21
       4.1.7.  GenericMetadata . . . . . . . . . . . . . . . . . . .  22
     4.2.  Definitions of the initial set of CDNI Generic Metadata
           objects . . . . . . . . . . . . . . . . . . . . . . . . .  24
       4.2.1.  SourceMetadata  . . . . . . . . . . . . . . . . . . .  24
         4.2.1.1.  Source  . . . . . . . . . . . . . . . . . . . . .  25
       4.2.2.  LocationACL Metadata  . . . . . . . . . . . . . . . .  26
         4.2.2.1.  LocationRule  . . . . . . . . . . . . . . . . . .  28
         4.2.2.2.  Footprint . . . . . . . . . . . . . . . . . . . .  28
       4.2.3.  TimeWindowACL . . . . . . . . . . . . . . . . . . . .  29
         4.2.3.1.  TimeWindowRule  . . . . . . . . . . . . . . . . .  30
         4.2.3.2.  TimeWindow  . . . . . . . . . . . . . . . . . . .  31
       4.2.4.  ProtocolACL Metadata  . . . . . . . . . . . . . . . .  32
         4.2.4.1.  ProtocolRule  . . . . . . . . . . . . . . . . . .  33
       4.2.5.  DeliveryAuthorization Metadata  . . . . . . . . . . .  34



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       4.2.6.  Cache . . . . . . . . . . . . . . . . . . . . . . . .  34
       4.2.7.  Auth  . . . . . . . . . . . . . . . . . . . . . . . .  35
       4.2.8.  Grouping  . . . . . . . . . . . . . . . . . . . . . .  36
     4.3.  CDNI Metadata Simple Data Type Descriptions . . . . . . .  37
       4.3.1.  Link  . . . . . . . . . . . . . . . . . . . . . . . .  37
       4.3.2.  Protocol  . . . . . . . . . . . . . . . . . . . . . .  38
       4.3.3.  Endpoint  . . . . . . . . . . . . . . . . . . . . . .  38
       4.3.4.  Time  . . . . . . . . . . . . . . . . . . . . . . . .  38
       4.3.5.  IPv4CIDR  . . . . . . . . . . . . . . . . . . . . . .  39
       4.3.6.  IPv6CIDR  . . . . . . . . . . . . . . . . . . . . . .  39
       4.3.7.  ASN . . . . . . . . . . . . . . . . . . . . . . . . .  39
       4.3.8.  CountryCode . . . . . . . . . . . . . . . . . . . . .  39
   5.  CDNI Metadata Capabilities  . . . . . . . . . . . . . . . . .  40
   6.  CDNI Metadata interface . . . . . . . . . . . . . . . . . . .  40
     6.1.  Transport . . . . . . . . . . . . . . . . . . . . . . . .  41
     6.2.  Retrieval of CDNI Metadata resources  . . . . . . . . . .  42
     6.3.  Bootstrapping . . . . . . . . . . . . . . . . . . . . . .  43
     6.4.  Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  43
     6.5.  Extensibility . . . . . . . . . . . . . . . . . . . . . .  44
     6.6.  Metadata Enforcement  . . . . . . . . . . . . . . . . . .  44
     6.7.  Metadata Conflicts  . . . . . . . . . . . . . . . . . . .  45
     6.8.  Versioning  . . . . . . . . . . . . . . . . . . . . . . .  45
     6.9.  Media Types . . . . . . . . . . . . . . . . . . . . . . .  46
     6.10. Complete CDNI Metadata Example  . . . . . . . . . . . . .  47
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  50
     7.1.  CDNI Payload Types  . . . . . . . . . . . . . . . . . . .  50
       7.1.1.  CDNI MI HostIndex Payload Type  . . . . . . . . . . .  51
       7.1.2.  CDNI MI HostMatch Payload Type  . . . . . . . . . . .  51
       7.1.3.  CDNI MI HostMetadata Payload Type . . . . . . . . . .  52
       7.1.4.  CDNI MI PathMatch Payload Type  . . . . . . . . . . .  52
       7.1.5.  CDNI MI PatternMatch Payload Type . . . . . . . . . .  52
       7.1.6.  CDNI MI PathMetadata Payload Type . . . . . . . . . .  52
       7.1.7.  CDNI MI SourceMetadata Payload Type . . . . . . . . .  52
       7.1.8.  CDNI MI Source Payload Type . . . . . . . . . . . . .  53
       7.1.9.  CDNI MI LocationACL Payload Type  . . . . . . . . . .  53
       7.1.10. CDNI MI LocationRule Payload Type . . . . . . . . . .  53
       7.1.11. CDNI MI Footprint Payload Type  . . . . . . . . . . .  53
       7.1.12. CDNI MI TimeWindowACL Payload Type  . . . . . . . . .  53
       7.1.13. CDNI MI TimeWindowRule Payload Type . . . . . . . . .  54
       7.1.14. CDNI MI TimeWindow Payload Type . . . . . . . . . . .  54
       7.1.15. CDNI MI ProtocolACL Payload Type  . . . . . . . . . .  54
       7.1.16. CDNI MI ProtocolRule Payload Type . . . . . . . . . .  54
       7.1.17. CDNI MI DeliveryAuthorization Payload Type  . . . . .  54
       7.1.18. CDNI MI Cache Payload Type  . . . . . . . . . . . . .  55
       7.1.19. CDNI MI Auth Payload Type . . . . . . . . . . . . . .  55
       7.1.20. CDNI MI Grouping Payload Type . . . . . . . . . . . .  55
     7.2.  CDNI Metadata Footprint Types Registry  . . . . . . . . .  55
     7.3.  CDNI Metadata Protocol Types Registry . . . . . . . . . .  56



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     7.4.  CDNI Metadata Auth Types Registry . . . . . . . . . . . .  56
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  57
     8.1.  Authentication  . . . . . . . . . . . . . . . . . . . . .  57
     8.2.  Confidentiality . . . . . . . . . . . . . . . . . . . . .  57
     8.3.  Integrity . . . . . . . . . . . . . . . . . . . . . . . .  58
     8.4.  Privacy . . . . . . . . . . . . . . . . . . . . . . . . .  58
     8.5.  Securing the CDNI Metadata interface  . . . . . . . . . .  58
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  59
   10. Contributing Authors  . . . . . . . . . . . . . . . . . . . .  59
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  59
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  59
     11.2.  Informative References . . . . . . . . . . . . . . . . .  60
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  61

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 may 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 focuses on 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).



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

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, covering the initial
   capabilities above, is only able to support CDN interconnection for
   the delivery of content by a dCDN using HTTPv1.1 [RFC7230] and for a
   dCDN to be able to acquire content from a uCDN using either HTTPv1.1
   or HTTPv1.1 over TLS [RFC2818].

   Supporting CDN interconnection for the delivery of content using
   unencrypted HTTPv2.0 [RFC7540] (as well as for a dCDN to acquire
   content using unencrypted HTTPv2.0 or HTTPv2.0 over TLS) requires the
   registration of these protocol names in the CDNI Metadata Protocol
   Registry.

   Supporting CDN interconnection for the delivery of content using
   HTTPv1.1 over TLS or HTTPv2.0 over TLS requires specifying additional
   metadata objects to carry the properties required to establish a TLS
   session, for example metadata to describe the certificate to use as
   part of the TLS handshake.

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.

   5.  Leveraging of existing protocols.

   Cacheability improves the latency of acquiring metadata while
   maintaining its freshness, and therefore improves 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 interface can be used for HTTP and DNS redirection and also




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   meets the same design principles for both HTTP and DNS based
   redirection schemes.

   Minimal duplication of CDNI metadata provides space efficiency on
   storage in the CDNs, on caches in the network, and across the network
   between 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
   may be aggregated 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 or URI path.  As a result
   of this structure, significant commonality may 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 treated as being grouped together into a single
   network or geographic location is likely to be common for a number of
   different Hostnames.  Another example is that 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 would
   be applied to multiple Hostnames delivered through the CDN.

   In order to enable the CDNI metadata for a given Hostname or URI Path
   to be decomposed into sets of CDNI metadata properties that can be
   reused by multiple Hostnames and URI Paths, the CDNI metadata
   interface specified in this document splits the CDNI metadata into a
   number of objects.  Efficiency is improved by enabling a single CDNI
   metadata object (that is shared across Hostname and/or URI paths) to




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   be retrieved and stored by a dCDN once, even if it is referenced by
   the CDNI metadata of multiple Hostnames or of multiple URI paths.

   Important Note: Any CDNI metadata object A that contains another CDNI
   metadata object B may, instead of including the second object B
   embedded within object A, include a Link object that contains a URI
   that can be dereferenced to retrieve the complete serialized
   representation of the second metadata object B.  The remainder of
   this document uses the phrase "[Object] A contains [Object] B" for
   simplicity when a strictly accurate phrase would be "[Object] A
   contains or references (via a Link object) [Object] B".  It is
   generally a deployment choice for the uCDN implementation to decide
   when and which CDNI metadata objects to embed and which to make
   available as 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 those objects.

   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.

















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   +---------+      +---------+      +------------+
   |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)

   A HostIndex object (see Section 4.1.1) contains a list of HostMatch
   objects (see Section 4.1.2) that contain Hostnames (and/or IP
   addresses) for which content requests may 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, on receipt of a User Agent request for content, which other
   CDNI metadata objects it requires in order to deliver the requested
   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 CDNI metadata within
   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 properties for each host as well as PathMetadata objects
   (see Section 4.1.6), via PathMatch objects (see Section 4.1.4), which
   may override those properties for given URI paths within the host.
   The CDNI metadata contained in HostMetadata objects is applied to
   content requests for which there is not more specific metadata, i.e.
   for content requests that do not match any of the PathMatch objects
   contained by that HostMetadata object and its child PathMetadata
   objects.



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   HostMetadata can also contain PathMatch objects.  PathMatch objects
   define patterns, contained inside PatternMatch objects (see
   Section 4.1.5), to match against the requested URI path, and contain
   PathMetadata objects which contain the GenericMetadata objects to be
   applied when a content request matches against the defined URI path
   pattern.  PatternMatch objects contain the pattern strings and flags
   that describe the URI path that a PathMatch applies to.

   PathMetadata objects override the CDNI metadata in the HostMetadata
   object or one or more parent PathMetadata objects with more specific
   CDNI metadata that applies to content requests matching the URI
   pattern defined in the PatternMatch object of that PathMatch object.
   A PathMetadata object may also contain PathMatch objects in order to
   recursively define more specific URI paths that require different
   (e.g., more specific) CDNI metadata to this one.

   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 may describe the source from which a CDN may acquire a piece
   of content.  The GenericMetadata object is an atomic unit that may be
   referenced by HostMetadata and/or PathMetadata objects.

   For example, if "example.com" is a content provider, a HostMatch
   object may 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 CDNI metadata
   objects for those more specific URI paths.  The PathMetadata object
   for "example.com/movies/*" describes CDNI metadata which apply to
   that URI path and could contain a PathMatch object for
   "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.













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   +--------------+----------------------------------------------------+
   | 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 (e.g., property semantics, enforcement options,
   etc.).

   The GenericMetadata object defines the type of properties contained
   within it as well as whether or not the properties are "mandatory-to-
   enforce".  If the dCDN does not understand or support the property
   type and the property type is "mandatory-to-enforce", the dCDN MUST
   NOT serve the content to the User Agent.  If the dCDN does not
   understand or support the property type and the property type is not
   "mandatory-to-enforce", then that GenericMetadata object may be
   safely ignored and the dCDN MUST process the content request 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 may be "safe-
   to-redistribute" that metadata to another CDN without modification.
   For example, in the cascaded CDN case, a transit CDN (tCDN) may pass
   through "mandatory-to-enforce" metadata to a dCDN.  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 natively
   understood or supported by the transit CDN.  However, for metadata



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   which requires translation, transparent redistribution of the uCDN
   metadata values might not be appropriate.  Certain metadata may be
   safely, though possibly not optimally, redistributed unmodified.  For
   example, source acquisition address may not be optimal if
   transparently redistributed, but might still work.

   Redistribution safety MUST be specified for each GenericMetadata.  If
   a CDN does not understand or support a given GenericMetadata property
   type and the property type is not "safe-to-redistribute", before
   redistributing the metadata, the CDN MUST set the "incomprehensible"
   flag for the GenericMetadata object that it did not understand and
   was marked as not "safe-to-redistribute".  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 may 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 either   |
   |       |       |            | by transforming not StR 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 either   |
   |       |       |            | by transforming not StR 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 may contain
   multiple PathMetadata objects (via PathMatch objects).  Each
   PathMetadata object may 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 a list 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 the
   inheritance tree and identify which specific 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
   sub-objects (i.e., GenericMetadata sub-objects contained within the
   GenericMetadata object that refers to that GenericMetadata sub-
   object).  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 may
   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 the metadata object, though
   that may restrict the content that a given dCDN can serve. uCDNs as
   generators of CDNI metadata only need to support generating the CDNI
   metadata that they need in order to express the policies and
   treatment required by the content they are describing.

   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.
   See Section 6.4 for more details of 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" by this document for an individual property, it



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   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, 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 a list 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: List 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: List 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.v1",
         "href": "http://metadata.ucdn.example/hostmatch1234"
       }
     ]
   }





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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.

      Property: host

         Description: String (Hostname or IP address) to match against
         the requested host.  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 when converted to lowercase in the content
         request MUST be identical to the value of the host property
         when converted to lowercase.  IPv4 addresses MUST be 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].

         Type: String

         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.v1",
       "href": "http://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: List of host related metadata.

         Type: List 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 PathMatch object that matches the content request being
         processed MUST be used.

         Type: List 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 a single embedded PathMatch object that will describe
   the CDNI metadata for that path which 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 a pattern within a PatternMatch object to
   match against a resource's URI path and contains a PathMetadata
   object to apply if the resource's URI path matches the pattern within
   the PatternMatch object.

      Property: path-pattern

         Description: Pattern to match against the requested resource's
         URI path, i.e., against the [RFC3986] path-absolute.

         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.v1",
         "href": "http://metadata.ucdn.example/host1234/pathDCE"
     }
   }

4.1.5.  PatternMatch

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

      Property: pattern

         Description: A pattern for string matching.  The pattern may
         contain the wildcards * and ?, where * matches any sequence of
         characters (including the empty string) and ? matches exactly
         one character.  The three literals $, * and ? should be escaped
         as $$, $* and $?. 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.

         Type: Boolean

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

      Property: ignore-query-string

         Description: List of query parameters which should be ignored
         when searching for a pattern match.  Matching against query
         parameters to ignore MUST be case-insensitive.  If all query
         parameters should be ignored then the list MUST be empty.




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         Type: List of String

         Mandatory-to-Specify: No.  Default is to include query strings
         when matching.

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

   {
     "pattern": "/movies/*",
     "case-sensitive": true,
     "ignore-query-string": []
   }

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

   {
     "pattern": "/movies/*",
     "case-sensitive": true,
     "ignore-query-string": ["sessionid"]
   }

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) and possibly child PathMatch objects.

   Note that if DNS-based redirection is employed, then a dCDN will be
   unable to evaulate any metadata at the PathMetadata level or below
   against the content redirection request at request routing time
   because only the hostname of the content request is available at
   request routing time. dCDNs SHOULD still process any metadata at the
   PathMetadata level or below before responding to the redirection
   request in order to detect if any unsupported metadata is specifed.
   If any metadata is included and marked as "mandatory-to-enforce"
   which is not supported by the dCDN then the dCDN SHOULD NOT redirect
   the the content redirection request to itself in order to avoid
   receiving content requests that it is not able to satisfy/serve.

      Property: metadata

         Description: List of path related metadata.



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         Type: List of GenericMetadata objects

         Mandatory-to-Specify: Yes.

      Property: paths

         Description: Path specific rules.  First match applies.

         Type: List 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.

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

    ...

       {
         <Properties of Nth embedded GenericMetadata 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 of the object
         contained in the generic-metadata-value property.

         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.

         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 may 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):








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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: List 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.v1"
     "generic-metadata-value":
       {
         "sources": [
           {
             "endpoints": [
               "a.service123.ucdn.example",
               "b.service123.ucdn.example"
               ],
             "protocol": "http1.1"
           },
           {
             "endpoints": ["origin.service123.example"],
             "protocol": "http1.1"
           }
         ]
       }
   }

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
   so a uCDN can specify a list of sources in preference order and for
   each source/preference rank a uCDN can specify a list 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, for example a pool of
         servers behind a load balancer.

         Type: List 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": "http1.1"
   }

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, meaning that delivery can be performed regardless
   of the User Agent's location.  The action from the first footprint to
   match against the User Agent's location is the action a CDN MUST
   take.  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 may 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: List 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.v1"
     "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.v1"
     "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 a list of Footprint objects and
   the corresponding action.

      Property: footprints

         Description: List of footprints to which the rule applies.

         Type: List 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
   may be applied to, e.g., an IPv4 address range or a geographic
   location.

      Property: footprint-type

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




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

         Type: Lowercase String

         Mandatory-to-Specify: Yes.

      Property: footprint-value

         Description: List of footprint values conforming to the
         specification associated with the registered footprint type.
         Footprint values may be simple strings (e.g., IPv4CIDR,
         IPv5CIDR, ASN, and CountryCode), however, other Footprint
         objects may be defined in the future, along with a more complex
         encoding (e.g., GPS coordinate tuples).

         Type: List 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"]
   }

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, meaning that delivery can be performed regardless of
   the time of the User Agent's request.  The action from the first
   window to match against the current time is the action a CDN MUST
   take.  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.



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   Although the LocationACL, TimeWindowACL, and ProtocolACL are
   independent GenericMetadata objects, they may 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: List 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 09:00AM 01/01/2000 UTC and
   17:00AM 01/01/2000 UTC:

   {
     "generic-metadata-type": "MI.TimeWindowACL.v1"
     "generic-metadata-value":
       {
         "times": [
           {
             "action": "allow",
             "windows": [
               {
                 "start": 946717200,
                 "end": 946746000
               }
             ]
           }
         ]
       }
   }

4.2.3.1.  TimeWindowRule

   A TimeWindowRule contains or references a list of TimeWindow objects
   and the corresponding action.

      Property: windows

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



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         Type: List 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
   09:00AM 01/01/2000 UTC and 17:00AM 01/01/2000 UTC:

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

4.2.3.2.  TimeWindow

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



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   Example TimeWIndow object that describes a time window from 09:00AM
   01/01/2000 UTC to 17:00AM 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, meaning that delivery can be performed
   regardless of the protocol of the User Agent's request.  The action
   from the first protocol to match against the request protocol is the
   action a CDN MUST take.  If two or more request protocols overlap,
   the first protocol that matches thre 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 may 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: List 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:










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   {
     "generic-metadata-type": "MI.ProtocolACL.v1"
     "generic-metadata-value":
       {
         "protocol-acl": [
           {
             "action": "allow",
             "protocols": ["http1.1"]
           }
         ]
       }
   }

4.2.4.1.  ProtocolRule

   A ProtocolRule contains or references a list of Protocol objects.
   ProtocolRule objects are used to construct a ProtocolACL to apply
   restrictions to content acquisition or delivery.

      Property: protocols

         Description: List of protocols to which the rule applies.

         Type: List 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 includes the protocol HTTP/1.1:

   {
     "action": "allow",
     "protocols": ["http1.1"]
   }








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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: List 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):

   {
     "generic-metadata-type": "MI.DeliveryAuthorization.v1"
     "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.

      Property: ignore-query-string

         Description: Allows a Surrogate to ignore URI query string
         parameters when comparing the requested URI against the URIs in
         its cache for equivalence.  Matching against query parameters
         to ignore MUST be case-insensitive.  Each query parameter to
         ignore is specified in the list.  If all query parameters




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         should be ignored, then the list MUST be specified and MUST be
         empty.

         Type: List of String

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

   Example Cache object that instructs the dCDN to ignore all query
   parameters:

   {
     "generic-metadata-type":
       "MI.Cache.v1"
     "generic-metadata-value":
     {
       "ignore-query-string": []
     }
   }

   Example Cache object that instructs the dCDN to ignore the (case-
   insensitive) query parameters named "sessionid" and "random":

   {
     "generic-metadata-type":
       "MI.Cache.v1"
     "generic-metadata-value":
     {
       "ignore-query-string": ["sessionid", "random"]
     }
   }

4.2.7.  Auth

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

      Property: auth-type

         Description: Registered Auth type (Section 7.4).

         Type: String

         Mandatory-to-Specify: Yes.

      Property: auth-value





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

         Type: GenericMetadata Object

         Mandatory-to-Specify: Yes.

   Example Auth object:

   {
     "generic-metadata-type":
       "MI.Auth.v1"
     "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 large group of content to which a
   given asset belongs.

      Property: ccid

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

         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 HostMetdata or PathMetadata:

   {
     "generic-metadata-type":
       "MI.Grouping.v1"
     "generic-metadata-value":
     {
       "ccid": "ABCD",
     }
   }



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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 may 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
   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 instead of another
   metadata 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 type of the object being referenced.

         Type: String

         Mandatory-to-Specify: No

   Example Link object referencing a HostMetadata object:

   {
     "type": "MI.HostMetadata.v1",
     "href": "http://metadata.ucdn.example/host1234"
   }







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4.3.2.  Protocol

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

   Type: String

   Example:

   "http1.1"

4.3.3.  Endpoint

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

   Note: 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].

   Type: String

   Example Hostname:

   "http://metadata.ucdn.example/host1234"

   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 Unix epoch in the UTC
   timezone.

   Type: Integer

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

   946717200





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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

   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.

   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"



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5.  CDNI Metadata Capabilities

   CDNI metadata is used to convey information pertaining to content
   delivery from uCDN to dCDN.  For optional metadata, it may 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 may be assigned optional values, it
   may 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 may
   fail, so again the uCDN is likely to want to avoid delegating those
   requests to that dCDN.

   The CDNI Footprint and Capabilities Interface (FCI) [RFC7336]
   provides a means of advertising capabilities from dCDN to uCDN.
   Support for optional metadata and support for optional metadata
   values may be advertised using the FCI.

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.

   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).





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   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 a list of Hostnames for
   which the uCDN may 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.

   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 from
   servers implementing the CDNI metadata interface that contain a
   response body SHOULD include an ETag to enable validation of cached
   versions of returned resources.

   The CDNI metadata interface specified in this document is a read-only
   interface.  Therefore support for other HTTP methods such as PUT,
   POST and DELETE etc. is not specified.  A server implementation of
   the CDNI metadata interface SHOULD reject all methods other than GET
   and HEAD.

   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.






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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 therefore in order to
   retrieve CDNI metadata, a CDNI metadata client first makes a HTTP GET
   request for the URI of the HostIndex which provides the CDNI metadata
   client with a list of Hostnames for which the uCDN may 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 the PathMatch).  If
   any PathMetadata match the request (and are linked rather than
   embedded), the CDNI metadata client makes another GET request for the
   PathMetadata.  Each PathMetadata object may 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 a redirection request from an uCDN or a content
   request from a User Agent.

   In cases where a dCDN is not able to retrieve the entire set of CDNI
   metadata associated with a User Agent request, for example because
   the uCDN is uncontactable or returns an HTTP 4xx or 5xx status in
   response to some or all of the dCDN's CDNI metadata requests, the
   dCDN MUST NOT serve the requested content unless the dCDN has stale
   versions of all the required metadata and the stale-if-error Cache-
   Control extension [RFC5861] was included in all previous responses
   that are required but cannot currently be retrieved.  The dCDN can
   continue to serve other content for which it can retrieve (or for
   which it has fresh responses cached) all the required metadata even
   if some non-applicable part of the metadata tree is missing.

   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.



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   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
   HostIndex served by each uCDN may 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 may 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 either
   configured in, or discovered by, the dCDN.  All other objects/
   resources are then discoverable from the HostIndex object by
   following any links in the HostIndex object and the referenced
   HostMetadata and PathMetadata objects and their GenericMetadata sub-
   objects.

   If the URI for the HostIndex object is not manually configured in the
   dCDN then the HostIndex URI could be discovered.  A mechanism
   allowing the dCDN to discover the URI of the HostIndex 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
   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
   represented in lowercase.




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6.5.  Extensibility

   The set of GenericMetadata objects may 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 lists.

   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 SHOULD:

   1.  Specify the CDNI Payload Type used to identify the new
       GenericMetadata type being specified.

   2.  Define the set of properties associated with the new type
       contained within the GenericMetadata object.  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.

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

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

   Note: In the case of vendor specific extensions, identification
   within the type name defined for a GenericMetadata object, of the
   organization that defined the new GenericMetadata object decreases
   the possibility of GenericMetadata type collisions.

6.6.  Metadata Enforcement

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

   In the 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.



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   Note: Ideally, uCDNs would not delegate content requests to a dCDN
   which 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
   CDNI capabilities interface or through out-of-band negotiation
   between CDN operators) metadata support may 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 requests 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 may obsolete or conflict
   with existing GenericMetadata (e.g., a future revision of the CDNI
   metadata interface may redefine the Auth GenericMetadata object or a
   custom vendor extension may 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
   (e.g., MI.Auth.v1) and all are marked as "mandatory-to-enforce", it
   may 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 content do not conflict.

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

6.8.  Versioning

   The version of CDNI metadata objects is conveyed inside the CDNI
   Payload Type that is included in the HTTP Content-Type header.  Upon
   responding to a request for an object, a CDNI metadata server MUST
   include a Content-Type header with the CDNI Payload Type containing
   the version number of the object.  HTTP requests sent to a metadata
   server SHOULD include an Accept header with the CDNI Payload Type
   (which includes the version) 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



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   different versions of the same type of object (defined by different
   CDNI Payload Types) it may decide to include both in the Accept
   header.  The version of each object defined by this document is
   version 1.  For example: "Content-Type: application/cdni;
   ptype=MI.HostIndex.v1".

   GenericMetadata objects include a "type" property which specifies the
   CDNI Payload Type of the GenericMetadata value.  This CDNI Payload
   Type should also include a version.  Any document which defines a new
   GenericMetadata type MUST specify the version number which it
   describes.  For example: "MI.Location.v1".

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 Paylod Type for the metadata objects
   (resources) that are specified in this document.

          +-----------------------+-----------------------------+
          | Data Object           | CDNI Payload Type           |
          +-----------------------+-----------------------------+
          | HostIndex             | MI.HostIndex.v1             |
          | HostMatch             | MI.HostMatch.v1             |
          | HostMetadata          | MI.HostMetadata.v1          |
          | PathMatch             | MI.PathMatch.v1             |
          | PatternMatch          | MI.PatternMatch.v1          |
          | PathMetadata          | MI.PathMetadata.v1          |
          | GenericMetadata       | MI.SourceMetadata.v1        |
          | Source                | MI.Source.v1                |
          | LocationACL           | MI.LocationACL.v1           |
          | LocationRule          | MI.LocationRule.v1          |
          | Footprint             | MI.Footprint.v1             |
          | TimeWindowACL         | MI.TimeWindowACL.v1         |
          | TimeWindowRule        | MI.TimeWindowRule.v1        |
          | TimeWindow            | MI.TineWindow.v1            |
          | ProtocolACL           | MI.ProtocolACL.v1           |
          | ProtocolRule          | MI.ProtocolRule.v1          |
          | DeliveryAuthorization | MI.DeliveryAuthorization.v1 |
          | Cache                 | MI.Cache.v1                 |
          | Auth                  | MI.Auth.v1                  |
          | Grouping              | MI.Grouping.v1              |
          +-----------------------+-----------------------------+

           Table 4: CDNI Payload Types for CDNI Metadata objects





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6.10.  Complete CDNI Metadata Example

   A dCDN may request the HostIndex and receive the following object
   with a CDNI payload type of "MI.HostIndex.v1":

   {
     "hosts": [
       {
         "host": "video.example.com",
         "host-metadata" : {
           "type": "MI.HostMetadata.v1",
           "href": "http://metadata.ucdn.example/host1234"
         }
       },
       {
         "host": "images.example.com",
         "host-metadata" : {
           "type": "MI.HostMetadata.v1",
           "href": "http://metadata.ucdn.example/host5678"
         }
       }
     ]
   }

   If the incoming request has a Host header with "video.example.com"
   then the dCDN would fetch the next metadata object from
   "http://metadata.ucdn.example/host1234" expecting a CDNI payload type
   of "MI.HostMetadata.v1":

   {
     "metadata": [
       {
         "generic-metadata-type":
           "MI.SourceMetadata.v1",
         "generic-metadata-value": {
           "sources": [
             {
               "endpoint": "acq1.ucdn.example",
               "protocol": "http1.1"
             },
             {
               "endpoint": "acq2.ucdn.example",
               "protocol": "http1.1"
             }
           ]
         }
       },
       {



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         "generic-metadata-type":
           "MI.LocationACL.v1",
         "generic-metadata-value": {
           "locations": [
             {
               "footprints": [
                 {
                   "footprint-type": "IPv4CIDR",
                   "footprint-value": "192.0.2.0/24"
                 }
               ],
               "action": "deny"
             }
           ]
         }
       },
       {
         "generic-metadata-type":
           "MI.ProtocolACL.v1",
         "generic-metadata-value": {
           "protocol-acl": [
             {
               "protocols": [
                 "http1.1"
               ],
               "action": "allow"
             }
           ]
         }
       }
     ],
     "paths": [
       {
         "path-pattern": {
           "pattern": "/video/trailers/*"
         },
         "path-metadata": {
           "type": "MI.PathMetadata.v1",
           "href": "http://metadata.ucdn.example/host1234/pathABC"
         }
       },
       {
         "path-pattern": {
           "pattern": "/video/movies/*"
         },
         "path-metadata": {
           "type": "MI.PathMetadata.v1",
           "href": "http://metadata.ucdn.example/host1234/pathDCE"



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         }
       }
     ]
   }

   Suppose the path of the requested resource matches the "/video/
   movies/*" pattern, the next metadata requested would be for
   "http://metadata.ucdn.example/host1234/movies" with an expected CDNI
   payload type of "MI.PathMetadata.v1":

   {
     "metadata": [],
     "paths": [
       {
         "path-pattern": {
           "pattern": "/videos/movies/hd/*"
         },
         "path-metadata": {
           "type": "MI.PathMetadata.v1",
           "href":
             "http://metadata.ucdn.example/host1234/pathABC/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 "http://metadata.ucdn.example/host1234/movies/
   hd" with CDNI payload type "MI.PathMetadata.v1":





















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   {
     "metadata": [
       {
         "generic-metadata-type":
           "MI.TimeWindowACL.v1",
         "generic-metadata-value": {
           "times": [
             "windows": [
               {
                 "start": "1213948800",
                 "end": "1327393200"
               }
             ],
             "action": "allow"
           ]
         }
       }
     ]
   }

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.v1             | RFCthis       |
              | MI.HostMatch.v1             | RFCthis       |
              | MI.HostMetadata.v1          | RFCthis       |
              | MI.PathMatch.v1             | RFCthis       |
              | MI.PatternMatch.v1          | RFCthis       |
              | MI.PathMetadata.v1          | RFCthis       |
              | MI.SourceMetadata.v1        | RFCthis       |
              | MI.Source.v1                | RFCthis       |
              | MI.LocationACL.v1           | RFCthis       |
              | MI.LocationRule.v1          | RFCthis       |
              | MI.Footprint.v1             | RFCthis       |
              | MI.TimeWindowACL.v1         | RFCthis       |
              | MI.TimeWindowRule.v1        | RFCthis       |
              | MI.TimeWindow.v1            | RFCthis       |
              | MI.ProtocolACL.v1           | RFCthis       |
              | MI.ProtocolRule.v1          | RFCthis       |
              | MI.DeliveryAuthorization.v1 | RFCthis       |
              | MI.Cache.v1                 | RFCthis       |
              | MI.Auth.v1                  | RFCthis       |
              | MI.Grouping.v1              | 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 capabilitiy 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 capabilitiy 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 capabilitiy
   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 capabilitiy 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 capabilitiy
   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 capabilitiy
   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 capabilitiy
   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 capabilitiy 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 capabilitiy 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 capabilitiy
   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 capabilitiy 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 capabilitiy
   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 capabilitiy
   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 capabilitiy 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 capabilitiy 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 capabilitiy
   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 capabilitiy
   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 capabilitiy 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 capabilitiy 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 capabilitiy 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"
   registry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" category.  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.

   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"
   registry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" category.  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 | Specification  |
   +----------+-----------------------+---------------+----------------+
   | http1.1  | Hypertext Transfer    | RFCthis       | RFC7230        |
   |          | Protocol -- HTTP/1.1  |               |                |
   | https1.1 | HTTP/1.1 Over TLS     | RFCthis       | RFC2818        |
   +----------+-----------------------+---------------+----------------+

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

7.4.  CDNI Metadata Auth Types Registry

   The IANA is requested to create a new "CDNI Metadata Auth Types"
   registry in the "Content Delivery Networks Interconnection (CDNI)
   Parameters" category.  The "CDNI Metadata Auth Type" namespace
   defines the valid Auth object types used by the Auth object in
   Section 4.2.7.  Additions to the Auth Type namespace conform to the



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   "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.

   The registry will initially be unpopulated:

                +-----------+-------------+---------------+
                | Auth Type | Description | Specification |
                +-----------+-------------+---------------+
                +-----------+-------------+---------------+

8.  Security Considerations

8.1.  Authentication

   Unauthorized access to metadata could result in denial of service.  A
   malicious metadata server, proxy server or an attacker performing a
   "man in the middle" attack could provide malicious metadata to a dCDN
   that either:

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

   o  Directs dCDNs to contact malicious origin servers instead of the
      actual origin servers.

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

   Unauthorized access to metadata could 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 SHOULD use mutual
   authentication to prevent unauthorized access to metadata.

8.2.  Confidentiality

   Unauthorized viewing of metadata could result in leakage of private
   information.  A third party could intercept metadata transactions in
   order to gain access to origin servers, as well as information
   pertaining to content restrictions.

   An implementation of the CDNI metadata interface SHOULD use strong
   encryption to prevent unauthorized interception of metadata.



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8.3.  Integrity

   Unauthorized modification of metadata could result in denial of
   service.  A malicious metadata server, proxy server or an attacker
   performing a "man in the middle" attack" could modify metadata
   destined to a dCDN in order to deny service for one or more pieces of
   content to one or more user agents.  A malicious metadata server,
   proxy server or an attacker performing a "Man in the middle" attack
   could modify metadata so that dCDNs are directed to contact to
   malicious origin servers instead of the actual origin servers.

   An implementation of the CDNI metadata interface SHOULD use strong
   encryption and mutual authentication to prevent unauthorized
   modification of metadata.

8.4.  Privacy

   Content provider origin and policy information is conveyed through
   the CDNI metadata interface.  The distribution of this information to
   another CDN may introduce potential privacy concerns for some content
   providers, for example because dCDNs accepting content requests for a
   content provider's content may be able to obtain additional
   information & usage patterns relating to the users of a content
   provider's services.  Content providers with such concerns can
   instruct their CDN partners not to use CDN interconnects when
   delivering that content provider's content.

8.5.  Securing the CDNI Metadata interface

   An implementation of the CDNI metadata interface MUST support TLS
   transport as per [RFC2818] and [RFC7230].  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 & responses from an
      authorized CDN).

   o  CDNI metadata interface requests and responses to be transmitted
      with confidentiality.

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





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   In an environment where any such protection is required, TLS MUST be
   used (including authentication of the remote end) by the server-side
   (uCDN) and the client-side (dCDN) of the CDNI metadata interface
   unless alternate methods are used for ensuring the confidentiality 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).

   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.]

   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]
              "https://www.iso.org/obp/ui/#search".






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   [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>.

   [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>.

   [RFC5861]  Nottingham, M., "HTTP Cache-Control Extensions for Stale
              Content", RFC 5861, DOI 10.17487/RFC5861, May 2010,
              <http://www.rfc-editor.org/info/rfc5861>.

   [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>.

   [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>.

   [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>.

11.2.  Informative References

   [I-D.ietf-cdni-redirection]
              Niven-Jenkins, B. and R. Brandenburg, "Request Routing
              Redirection Interface for CDN Interconnection", draft-
              ietf-cdni-redirection-13 (work in progress), October 2015.

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







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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>.

   [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>.

   [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>.

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

   [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>.

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




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Internet-Draft        CDN Interconnection Metadata          October 2015


   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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