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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                               G. Watson
Expires: April 24, 2014                         Velocix (Alcatel-Lucent)
                                                            M. Caulfield
                                                                K. Leung
                                                           Cisco Systems
                                                                   K. Ma
                                                     Azuki Systems, Inc.
                                                        October 21, 2013


                       CDN Interconnect Metadata
                      draft-ietf-cdni-metadata-03

Abstract

   The CDNI Metadata Interface enables interconnected 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 the core 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 24, 2014.




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Copyright Notice

   Copyright (c) 2013 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Design Principles . . . . . . . . . . . . . . . . . . . . . .   4
   3.  CDNI Metadata Data Model  . . . . . . . . . . . . . . . . . .   5
     3.1.  HostIndex, HostMetadata & PathMetadata objects  . . . . .   6
     3.2.  Generic CDNI Metadata Object Properties . . . . . . . . .   9
     3.3.  Metadata Inheritance and Override . . . . . . . . . . . .  10
     3.4.  Metadata Naming . . . . . . . . . . . . . . . . . . . . .  10
   4.  Encoding-Independent CDNI Metadata Object Descriptions  . . .  11
     4.1.  CDNI Metadata Structural Object Descriptions  . . . . . .  11
       4.1.1.  HostIndex . . . . . . . . . . . . . . . . . . . . . .  12
       4.1.2.  HostMatch . . . . . . . . . . . . . . . . . . . . . .  12
       4.1.3.  HostMetadata  . . . . . . . . . . . . . . . . . . . .  13
       4.1.4.  PathMatch . . . . . . . . . . . . . . . . . . . . . .  13
       4.1.5.  PathMetadata  . . . . . . . . . . . . . . . . . . . .  14
       4.1.6.  PatternMatch  . . . . . . . . . . . . . . . . . . . .  14
       4.1.7.  GenericMetadata . . . . . . . . . . . . . . . . . . .  15
     4.2.  CDNI Metadata Property Object Descriptions  . . . . . . .  16
       4.2.1.  Source Metadata . . . . . . . . . . . . . . . . . . .  16
         4.2.1.1.  Source  . . . . . . . . . . . . . . . . . . . . .  16
       4.2.2.  LocationACL Metadata  . . . . . . . . . . . . . . . .  17
         4.2.2.1.  LocationRule  . . . . . . . . . . . . . . . . . .  17
         4.2.2.2.  Footprint . . . . . . . . . . . . . . . . . . . .  17
       4.2.3.  TimeWindowACL Metadata  . . . . . . . . . . . . . . .  18
         4.2.3.1.  TimeWindowRule  . . . . . . . . . . . . . . . . .  18
         4.2.3.2.  TimeWindow  . . . . . . . . . . . . . . . . . . .  19
       4.2.4.  ProtocolACL Metadata  . . . . . . . . . . . . . . . .  19
         4.2.4.1.  ProtocolRule  . . . . . . . . . . . . . . . . . .  19
       4.2.5.  Authorization Metadata  . . . . . . . . . . . . . . .  20
       4.2.6.  Auth  . . . . . . . . . . . . . . . . . . . . . . . .  20
         4.2.6.1.  Credentials Auth Type . . . . . . . . . . . . . .  21



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       4.2.7.  Cache . . . . . . . . . . . . . . . . . . . . . . . .  21
       4.2.8.  Grouping  . . . . . . . . . . . . . . . . . . . . . .  22
     4.3.  CDNI Metadata Simple Data Type Descriptions . . . . . . .  22
       4.3.1.  Link  . . . . . . . . . . . . . . . . . . . . . . . .  22
       4.3.2.  Protocol  . . . . . . . . . . . . . . . . . . . . . .  23
       4.3.3.  Endpoint  . . . . . . . . . . . . . . . . . . . . . .  23
       4.3.4.  URI . . . . . . . . . . . . . . . . . . . . . . . . .  23
       4.3.5.  Time  . . . . . . . . . . . . . . . . . . . . . . . .  23
   5.  CDNI Metadata Capabilities  . . . . . . . . . . . . . . . . .  24
     5.1.  Protocol ACL Capabilities . . . . . . . . . . . . . . . .  24
     5.2.  Authorization Metadata Capabilities . . . . . . . . . . .  24
   6.  CDNI Metadata interface . . . . . . . . . . . . . . . . . . .  25
     6.1.  Transport . . . . . . . . . . . . . . . . . . . . . . . .  25
     6.2.  Retrieval of CDNI Metadata resources  . . . . . . . . . .  26
     6.3.  Bootstrapping . . . . . . . . . . . . . . . . . . . . . .  27
     6.4.  Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  28
       6.4.1.  MIME Media Types  . . . . . . . . . . . . . . . . . .  28
       6.4.2.  JSON Encoding of Objects  . . . . . . . . . . . . . .  28
         6.4.2.1.  JSON Example  . . . . . . . . . . . . . . . . . .  29
     6.5.  Extensibility . . . . . . . . . . . . . . . . . . . . . .  33
       6.5.1.  Metadata Enforcement  . . . . . . . . . . . . . . . .  33
       6.5.2.  Metadata Override . . . . . . . . . . . . . . . . . .  33
     6.6.  Versioning  . . . . . . . . . . . . . . . . . . . . . . .  34
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  34
     7.1.  GenericMetadata Type Registry . . . . . . . . . . . . . .  34
       7.1.1.  GenericMetadata Sub-Registries  . . . . . . . . . . .  35
         7.1.1.1.  Footprint Sub-Registry  . . . . . . . . . . . . .  35
         7.1.1.2.  Protocol Sub-Registry . . . . . . . . . . . . . .  36
         7.1.1.3.  Authentication Sub-Registry . . . . . . . . . . .  37
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  37
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  37
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  38
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  38
     10.2.  Informative References . . . . . . . . . . . . . . . . .  38
   Appendix A.  Relationship to the CDNI Requirements  . . . . . . .  39
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  39

1.  Introduction

   CDNI enables a downstream CDN to service content requests on behalf
   of an upstream CDN.  The CDNI metadata associated with a piece of
   content (or with a set of contents) provides a downstream CDN with
   sufficient information for servicing content requests on behalf of an
   upstream CDN in accordance with the policies defined by the upstream
   CDN.

   The CDNI Metadata Interface is introduced by [RFC6707] along with
   three other interfaces that may be used to compose a CDNI solution



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   (Control, Request Routing and Logging).  [I-D.ietf-cdni-framework]
   expands on the information provided in [RFC6707] and describes each
   interface, and the relationships between them, in more detail.  The
   requirements for the CDNI metadata interface are specified in
   [I-D.ietf-cdni-requirements].

   This document focuses on the CDNI Metadata interface which enables a
   downstream CDN to obtain CDNI Metadata from an upstream CDN so that
   the downstream CDN can properly process and respond to:

   o  Redirection Requests received over the CDNI Request Routing
      protocol.

   o  Content Requests received directly from User Agents.

   Specifically this document proposes:

   o  A data structure for mapping content requests to CDNI Metadata
      properties (Section 3).

   o  An initial set of CDNI Metadata properties (Section 4.2).

   o  A RESTful 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 an object.

2.  Design Principles

   The proposed CDNI Metadata Interface was designed to achieve the
   following objectives:

   1.  Cacheability of CDNI metadata objects

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





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

   4.  Minimal duplication of CDNI metadata

   5.  Leverage existing protocols

   Cacheability improves the latency of acquiring metadata while
   maintaining its freshness and therefore improves the latency of
   serving content requests.  The CDNI Metadata Interface uses HTTP to
   achieve cacheability.

   Deterministic mappings from content to metadata properties eliminates
   ambiguity and ensures that policies are applied consistently by all
   downstream CDNs.

   Support for both HTTP and DNS redirection ensures that the CDNI
   Metadata Interface can be used for HTTP and DNS redirection and also
   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 (e.g. XML, JSON) and data transport
   (e.g. HTTP).

3.  CDNI Metadata Data Model

   The CDNI Metadata Model describes a data structure for mapping
   redirection requests and content requests to metadata properties.
   Metadata properties describe how to acquire, authorize, and deliver
   content from a downstream CDN.  The data 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 of
   the content.  The data model associates a set of CDNI Metadata
   properties with a Hostname to form a default set of metadata
   properties for content delivered for 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 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



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   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
   be retrieved by a dCDN once, even if it is referenced by the CDNI
   Metadata of multiple Hostnames.

   Section 3.1 introduces a high level description of the HostIndex,
   HostMetadata 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 which may be contained within a CDNI GenericMetadata
   object.

3.1.  HostIndex, HostMetadata & PathMetadata objects

   A HostIndex object contains a list of Hostnames (and/or IP addresses)
   for which content requests may be delegated to the downstream CDN.
   The HostIndex is the starting point for accessing the uCDN's CDNI
   Metadata data store.  It enables surrogates in 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 via HostMatch objects.  HostMetadata objects contain (or
   reference) the default CDNI Metadata required to serve content for
   that host.  When looking up CDNI Metadata, the downstream CDN looks
   up the requested Hostname (or IP address) in the HostIndex, from
   there it can find HostMetadata which describes properties for a host



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   and PathMetadata which may override those properties for given URI
   paths within the host.

   As well as containing the default CDNI Metadata for the specified
   Hostname, HostMetadata and PathMetadata objects may also contain
   PathMatch objects which in turn contain PathMetadata objects.
   PathMatch objects override the CDNI Metadata in the HostMetadata
   object or one or more preceding PathMetadata objects with more
   specific CDNI Metadata that applies to content requests matching the
   pattern defined in that PathMatch object.

   For the purposes of retrieving CDNI Metadata all other required CDNI
   Metadata objects and their properties are discoverable from the
   appropriate HostMetadata, PathMatch and PathMetadata objects for the
   requested content.

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

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

   Key: ----> = References

       Figure 1: Relationships between the HostIndex, HostMetadata &
                    PathMetadata CDNI Metadata Objects

   The relationships in Figure 1 are summarised in Table 1 below.

   +--------------------+----------------------------------------------+
   | Data Object        | Objects it References                        |
   +--------------------+----------------------------------------------+
   | HostIndex          | 0 or more HostMatch objects.                 |



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   | HostMatch          | 1 HostMetadata object.                       |
   | HostMetadata       | 0 or more PathMatch objects. 0 or more       |
   |                    | GenericMetadata objects.                     |
   | PathMatch          | 1 PathMetadata object.                       |
   | PathMetadata       | 0 or more PathMatch objects. 0 or more       |
   |                    | GenericMetadata objects.                     |
   +--------------------+----------------------------------------------+

           Table 1: Relationships between CDNI Metadata Objects

   The table below describes the HostIndex, HostMetadata and
   PathMetadata objects in more detail.

   +-----------------+-------------------------------------------------+
   | Data Object     | Description                                     |
   +-----------------+-------------------------------------------------+
   | HostIndex       | A HostIndex object lists HostMatch objects      |
   | HostMatch       | A HostMatch object defines a hostname to match  |
   |                 | against a requested host, and contains or       |
   |                 | references a HostMetadata object which contains |
   |                 | CDNI Metadata objects to be applied when a      |
   |                 | request matches against the hostname. 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.                 |
   | HostMetadata    | A HostMetadata object contains (or references)  |
   |                 | the default CDNI Metadata objects for content   |
   |                 | served from that host, i.e. the CDNI Metadata   |
   |                 | objects for content requests that do not match  |
   |                 | any of the PathMatch objects contained or       |
   |                 | referenced by that HostMetadata object. For     |
   |                 | example, a HostMetadata object may describe the |
   |                 | metadata properties which apply to              |
   |                 | "example.com" and may contain PathMatches for   |
   |                 | "example.com/movies/*" and                      |
   |                 | "example.com/music/*" which reference           |
   |                 | corresponding PathMetadata objects that contain |
   |                 | the CDNI Metadata objects for those more        |
   |                 | specific URI paths.                             |
   | PathMatch       | A PathMatch object defines a pattern to match   |
   |                 | against the requested URI path, and contains or |
   |                 | references a PathMetadata object which contains |
   |                 | (or references) the CDNI Metadata objects to be |
   |                 | applied when a content request matches against  |
   |                 | the defined URI path pattern.                   |
   | PathMetadata    | A PathMetadata object contains the CDNI         |
   |                 | GenericMetadata objects for content served with |



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   |                 | the associated URI path (defined in a 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. For example, the PathMetadata object  |
   |                 | which applies to "example.com/movies/*" may     |
   |                 | describe CDNI Metadata which apply to that      |
   |                 | resource path and may contain a PathMatch       |
   |                 | object for "example.com/movies/hd/*" which      |
   |                 | would reference the corresponding PathMetadata  |
   |                 | object for the "example.com/movies/hd/" path    |
   |                 | prefix.                                         |
   | GenericMetadata | A GenericMetadata object contains individual    |
   |                 | CDNI Metadata objects which define the specific |
   |                 | policies and attributes needed to properly      |
   |                 | deliver the associated content.                 |
   +-----------------+-------------------------------------------------+

      Table 2: HostIndex, HostMetadata and PathMetadata CDNI Metadata
                                  Objects

3.2.  Generic CDNI Metadata Object Properties

   The HostMetadata and PathMetadata objects contain or can reference
   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, authorization rules that should be
   applied, delivery location 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 opaque 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 it is also not going to be able to
   properly propagate the Metadata for cascaded distribution.  If the
   dCDN does not understand or support the property type and the
   property type is not mandatory to enforce, then the GenericMetadata
   object may be safely ignored.

   Although a CDN cannot serve content to a User Agent if a mandatory
   property cannot be enforced, it may be safe to redistribute that



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   metadata to another CDN without modification.  For example, in the
   cascaded CDN case, a transit CDN may pass through mandatory-to-
   enforce metadata to the delivery CDN.  For Metadata which does not
   require customization, 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 which require
   translations, transparent redistribution of the uCDN Metadata values
   may not be appropriate.  Certain Metadata may be safely, though
   possibly not optimially, redistributed unmodified, e.g., source
   acquisition address may not be optimal if transparently
   redistributed, but may still work.  Redistribution safety MUST be
   specified for each GenericMetadata.

3.3.  Metadata Inheritance and Override

   In the data model, a HostMetadata object may contain (or reference)
   multiple PathMetadata objects (via PathMatch objects).  Each
   PathMetadata object may in turn contain (or reference) 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:

      the TimeWindowACL defined in the PathMetadata would override the
      TimeWindowACL defined in the HostMetadata

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

   The PathMetadata defined TimeWindowACL would override the
   TimeWindowACL defined in the HostMetadata for all User Agent requests
   for movies.

3.4.  Metadata Naming








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   GenericMetadata objects are identified by their type.  The type
   SHOULD be descriptive, and MAY be hierarchical to support aggregating
   groups of properties for the purpose of readability and for avoiding
   name conflicts between vendor extensions.  A dotted alpha-numeric
   notation is suggested for human readability.

   Metadata types defined by this document are not hierarchical.

   Examples of GenericMetadata object type names:

      LocationACL

      ext.vendor1.featurex

      ext.vendor1.featurey

      ext.vendor2.featurex

4.  Encoding-Independent CDNI Metadata Object Descriptions

   Section 4.1 provides the definitions of each object type declared in
   Section 3.  These objects are described as structural objects as they
   provide the structure for the inheritance tree and identifying which
   specific properties apply to a given User Agent content request.

   Section 4.2 provides the definitions for the set of core metadata
   objects which may be contained within a GenericMetadata object.
   These objects are described as property objects as they define the
   semantics, enforcement options, and serialization rules for specific
   properties.  These properties govern how User Agent requests for
   content are handled.  Property objects may be composed of or contain
   references to other objects.  In those cases the value of the
   property can be either an object of that type (the object is
   embedded) or a Link object that contains a URI and relationship that
   can be dereferenced to retrieve the CDNI Metadata object that
   represents the value of that property.

   Note: In the following sections, the term "mandatory-to-specify" is
   used to convey which objects or properties must be specified for a
   given parent object or property.  When mandatory-to-specify is set to
   true, it implies that if the parent object is specified, then the
   defined object or property MUST also be specified, e.g., a HostMatch
   object without a host to match against does not make sense,
   therefore, the host is mandatory-to-specify inside a parent HostMatch
   object.

4.1.  CDNI Metadata Structural Object Descriptions




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   Each of the sub-sections below describe the structural objects
   defined in Table 2.

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 matched against the hostname inside of each of the
   listed HostMatch objects to find the HostMatch object which applies
   to the request.

      Property: hosts

         Description: List of HostMatch objects, in priority order.

         Type: List of HostMatch objects

         Mandatory-to-Specify: Yes.

4.1.2.  HostMatch

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

      Property: host

         Description: String (hostname or IP address) to match against
         the requested host.

         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.









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4.1.3.  HostMetadata

   The HostMetadata object contains both Metadata that applies to
   content requests for a particular host and a list of pattern matches
   for finding more specific Metadata based on the resource path in a
   content request.

      Property: metadata

         Description: List of host related metadata.

         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.

4.1.4.  PathMatch

   The PathMatch object contains an expression given as a PatternMatch
   object to match against a resource URI path and Metadata objects to
   apply if a match is found.

      Property: path-pattern

         Description: Pattern to match against the requested 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 this pattern.

         Type: PathMetadata

         Mandatory-to-Specify: Yes.





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4.1.5.  PathMetadata

   A PathMetadata object contains the CDNI Metadata properties for
   content served with the associated URI path (defined in a PathMatch
   object).  Note that if CDNI metadata is used as an input to CDNI
   request routing and DNS-based redirection is employed, then any
   metadata at the PathMetadata level or below will be inaccessible at
   request routing time.

      Property: metadata

         Description: List of path related metadata.

         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.

4.1.6.  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 \?

         Type: String

         Mandatory-to-Specify: Yes.

      Property: case-sensitive

         Description: Flag indicating whether or not case-sensitive
         matching should be used.

         Type: Boolean



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         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.  If all query parameters
         should be ignored then the list MUST be empty.

         Type: List of String

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

4.1.7.  GenericMetadata

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

      Property: type

         Description: CDNI Metadata property object type.

         Type: String

         Mandatory-to-Specify: Yes.

      Property: value

         Description: CDNI Metadata property object.

         Type: matches the 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: Yes.

      Property: safe-to-redistribute

         Description: Flag identifying whether or not the property
         Metadata may be safely redistributed without modification.




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         Type: Boolean

         Mandatory-to-Specify: No.  Default is allow transparent
         redistribution.

4.2.  CDNI Metadata Property Object Descriptions

4.2.1.  Source Metadata

   Source Metadata provides the dCDN information about content
   acquisition e.g. 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 priority order.

         Type: List of Source objects

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

4.2.1.1.  Source

   A Source object describes the Source which should 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.

      Property: auth

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

         Type: Auth

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

      Property: endpoints

         Description: Origins from which the dCDN can acquire content.

         Type: List of EndPoint objects




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         Mandatory-to-Specify: Yes.

      Property: protocol

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

         Type: Protocol

         Mandatory-to-Specify: Yes.

4.2.2.  LocationACL Metadata

   LocationACL Metadata defines location-based restrictions.

      Property: locations

         Description: Access control list which applies restrictions to
         delivery based on client location.

         Type: List of LocationRule objects

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

4.2.2.1.  LocationRule

   A LocationRule contains or references a list of Location objects and
   the corresponding action.

      Property: footprints

         Description: List of footprints to which the rule applies.

         Type: List of Footprint objects

         Mandatory-to-Specify: Yes.

      Property: action

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

         Type: Enumeration [allow|deny]

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

4.2.2.2.  Footprint




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

      Property: type

         Description: Registered footprint type (see Section 7.1.1.1).

         Type: String

         Mandatory-to-Specify: Yes.

      Property: value

         Description: Footprint object conforming to the specification
         associated with the registered footprint type.

         Type: String

         Mandatory-to-Specify: Yes.

4.2.3.  TimeWindowACL Metadata

   TimeWindowACL Metadata defines time-based restrictions.

      Property: times

         Description: Access control list which applies restrictions to
         delivery based on request time.

         Type: List of TimeWindowRule objects

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

4.2.3.1.  TimeWindowRule

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

      Property: times

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

         Type: List of TimeWindow objects

         Mandatory-to-Specify: Yes.

      Property: action



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

         Type: Enumeration [allow|deny]

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

4.2.3.2.  TimeWindow

   A TimeWindow object describes a time range which may be applied by an
   ACLRule, e.g. Start 09:00AM 01/01/2000 UTC End 17:00PM 01/01/2000
   UTC.

      Property: start

         Description: The start time of the window.

         Type: Time

         Mandatory-to-Specify: Yes.

      Property: end

         Description: The end time of the window.

         Type: Time

         Mandatory-to-Specify: Yes.

4.2.4.  ProtocolACL Metadata

   ProtocolACL Metadata defines delivery protocol restrictions.

      Property: protocols

         Description: Access control list which applies restrictions to
         delivery based on delivery protocol.

         Type: List of ProtocolRule objects

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

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.




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      Property: protocols

         Description: List of protocols to which the rule applies.

         Type: List of protocol objects

         Mandatory-to-Specify: Yes.

      Property: action

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

         Type: Enumeration [allow|deny]+

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

      Property: direction

         Description: Defines whether the ProtocolRule specifies
         protocols for acquisition or delivery.

         Type: Enumeration [acquisition|delivery]

         Mandatory-to-Specify: No.  Default is to apply the rule to both
         acquisition and delivery.

4.2.5.  Authorization Metadata

   Authorization Metadata define content authorization methods.

      Property: methods

         Description: Options for authenticating content requests.  All
         options in the list are equally valid.

         Type: List of Auth objects

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

4.2.6.  Auth

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

      Property: type




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         Description: Registered Auth type (see Section 7.1.1.3).

         Type: String

         Mandatory-to-Specify: Yes.

      Property: value

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

         Type: String

         Mandatory-to-Specify: Yes.

4.2.6.1.  Credentials Auth Type

   Credentials Auth is a type of Auth object with type "credentials"
   (see Section 7.1.1.3).  The CredentialsAuth object contains the
   following properties:

      Property: username

         Description: Identification of user.

         Type: String

         Mandatory-to-Specify: Yes.

      Property: password

         Description: Password for user identified by username property.

         Type: String

         Mandatory-to-Specify: Yes.

4.2.7.  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 cache to ignore URI query string
         parameters while comparing URIs for equivalence.  Each query
         parameter to ignore is specified in the list.  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 consider query string
         parameters when comparing URIs or to rely on other properties
         of the Cache object.

4.2.8.  Grouping

   A Grouping object identifies a large group of content to which this
   content 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.

      Property: sid

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

         Type: String

         Mandatory-to-Specify: No.  Default is an empty string.

4.3.  CDNI Metadata Simple Data Type Descriptions

   This section describes the simpler 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.  Links can be used to avoid duplication
   if the same metadata information is repeated within the metadata
   tree.  When a link replaces an object, its href property is set to
   the URI of the resource, its rel property is set to the name of the
   property it is replacing, and its type property is set to the type of
   the object it is replacing.

      Property: href

         Description: The URI of the of the addressable object being
         referenced.



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         Type: URI

         Mandatory-to-Specify: Yes

      Property: rel

         Description: The Relationship between the referring object and
         the object it is referencing.

         Type: String

         Mandatory-to-Specify: Yes

      Property: type

         Description: The type of the object being referenced.

         Type: String

         Mandatory-to-Specify: Yes

4.3.2.  Protocol

   Protocol objects are used to specify registered protocols for content
   acquisition or delivery (see Section 7.1.1.2).

   Type: String

   Mandatory-to-Specify: Yes

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] and
   MUST support all IPv6 address formats specified in [RFC4291].  Server
   implementations SHOULD use IPv6 address formats specified in
   [RFC5952].

4.3.4.  URI

   A URI as specified in [RFC3986].

4.3.5.  Time





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   A time value expressed in seconds since Unix epoch in the UTC
   timezone.

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 metadata, prior to
   delegating any content requests to the dCDN.  If optional-to-
   implement metadata is mandatory-to-enforce and the dCDN does not
   support it, any delegated requests for that content will fail, so
   there is no reason to delegate those requests.  Likewise, for any
   metadata which may be assigned optional values, it may be useful for
   the uCDN to know which values the dCDN supports, prior to delegating
   any content requests to the dCDN.  If a 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 there is likely
   no reason to delegate those requests.

   The CDNI Footprint and Capabilities Interface 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 capabilities interface.  This section describes the
   capabilities advertisement requirements for the metadata defined in
   Section 4.2

5.1.  Protocol ACL Capabilities

   The ProtoclACL object contains a list of Protocol values.  The dCDN
   MUST advertise which delivery protocols it supports so that the uCDN
   knows what type of content requests it can redirect to the dCDN.  If
   the dCDN does not support a given acquisition or delivery protocol,
   the uCDN should not delegate requests requiring those protocols to
   the dCDN as the dCDN will not be able to properly acquire or deliver
   the content.

   ProtocolRules are defined for either acquisition or delivery.  For
   some CDNs, certain combinations of acquisition and delivery protocols
   may not make sense (e.g., RTSP acquisition for HTTP delivery), while
   other CDNs may support customized protocol adaptation.  ProtocolACL
   capabilities are not intended to define which combinations of
   protocols should be used.  ProtocolACL capabilties are only intended
   to describe which protocols the dCDN does or does not support.
   Protocol combination restrictions are specified in the metadata
   itself and associated with specific groups of content assets.

5.2.  Authorization Metadata Capabilities




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   The Authorization object contains a list of Auth values.  The dCDN
   MUST advertise which authorization algorithms it supports so that the
   uCDN knows what type of content requests it can redirect to the dCDN.
   If the dCDN does not support a given authorization algorithm, the
   uCDN should not delegate requests requiring that algorithm to the
   dCDN as the dCDN will not be able to properly acquire the content or
   enforce delivery restrictions.

6.  CDNI Metadata interface

   This section specifies an interface to enable a Downstream CDN to
   retrieve CDNI Metadata objects from an Upstream CDN.

   The interface can be used by a Downstream CDN to retrieve CDNI
   Metadata objects either dynamically as required by the Downstream CDN
   to process received requests (for example in response to receiving a
   CDNI Request Routing request from an Upstream CDN or in response to
   receiving a request for content from a User Agent) or in advance of
   being required (for example in case of prepositioned CDNI Metadata
   acquisition).

   The CDNI Metadata interface is built on the principles of RESTful web
   services.  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 Data Model (as described in Section 3 through
   Section 4).

   In the general case a CDNI Metadata server makes each instance of an
   addressable CDNI Metadata object available via a unique URI that
   returns a representation of that instance of that CDNI Metadata
   object.  When an object needs to reference another addressable CDNI
   Metadata object (for example a HostIndex object referencing a
   HostMetadata object) it does so by including a link to the referenced
   object.

   CDNI Metadata servers 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 below
   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.



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   The HTTP Method in the request defines the operation the request
   would like to perform.  Servers implementing 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.  Server implementations of
   this interface SHOULD reject all methods other than GET and HEAD.

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

6.2.  Retrieval of CDNI Metadata resources

   In the general case a CDNI Metadata server makes each instance of an
   addressable CDNI Metadata object available via a unique URI 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 upstream CDN may delegate content delivery to the downstream CDN.

   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 in the HostMatch).  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.











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   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.  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 PathMetadata recursively.

   Where a downstream CDN is interconnected with multiple upstream CDNs,
   the downstream CDN must decide which upstream CDN's CDNI metadata
   should be used to handle a particular User Agent request.

   When application level redirection (e.g. HTTP 302 redirects) is being
   used between CDNs, it is expected that the downstream CDN will be
   able to determine the upstream CDN that redirected a particular
   request from information contained in the received request (e.g. via
   the URI).  With knowledge of which upstream CDN routed the request,
   the downstream CDN can choose the correct metadata server 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 upstream CDN that redirected a particular request (e.g. when
   content from a given host is redirected to a given downstream CDN by
   more than one upstream CDN) and therefore downstream CDNs may have to
   apply local policy when deciding which upstream CDN's metadata to
   apply.

6.3.  Bootstrapping

   The URI for the HostIndex object of a given upstream CDN needs to be
   either discovered by or configured in the downstream CDN.  All other
   objects/resources are then discoverable from the HostIndex object by
   following the links in the HostIndex object and the referenced
   HostMetadata and PathMetadata objects.

   If the URI for the HostIndex object is not manually configured in the
   downstream CDN then the HostIndex URI could be discovered.  A
   mechanism allowing the downstream CDN to discover the URI of the
   HostIndex is outside the scope of this document.









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6.4.  Encoding

   Object are resources that may be:

   o  Addressable, where the object is a resource that may be retrieved
      or referenced via its own URI.

   o  Embedded, where the object is contained (or inlined) within a
      property of an addressable object.

   In the descriptions of objects we use the term "X contains Y" to mean
   either Y is directly embedded in X or that Y is linked to by X. It is
   generally a deployment choice for the uCDN implementation to decide
   when and which CDNI Metadata objects to embed and which are
   separately addressable.

6.4.1.  MIME Media Types

   All MIME types are prefixed with "application/cdni."  The MIME type
   for each object matches the type name of that object as defined by
   this document.  Table 3 lists a few examples of the MIME Media Type
   for each object (resource) that is retrievable through the CDNI
   Metadata interface.

             +--------------+-------------------------------+
             | Data Object  | MIME Media Type               |
             +--------------+-------------------------------+
             | HostIndex    | application/cdni.HostIndex    |
             | HostMatch    | application/cdni.HostMatch    |
             | HostMetadata | application/cdni.HostMetadata |
             | PathMatch    | application/cdni.PathMatch    |
             | PathMetadata | application/cdni.PathMetadata |
             +--------------+-------------------------------+

        Table 3: Example MIME Media Types for CDNI Metadata objects

   See http://www.iana.org/assignments/media-types/index.html for
   reference.

6.4.2.  JSON Encoding of Objects

   CDNI Metadata objects are encoded as JSON objects 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 MIME Media Type of the returned



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   resource).  Likewise, the values associated with each key are
   dependent on the specific object being encoded (i.e. dependent on the
   MIME Media Type of the returned resource).

   Dictionary keys in JSON are case sensitive and therefore by
   convention any dictionary key defined by this document (for example
   the names of CDNI Metadata object properties) MUST be represented in
   lowercase.

   In addition to the properties specific to each object type, the keys
   defined below may be present in any object.

      Key: base

         Description: Provides a prefix for any relative URLs in the
         object.  This is similar to the XML base tag [XML-BASE].  If
         absent, all URLs in the remainder of the document must be
         absolute URLs.

         Type: URI

         Mandatory: No

      Key: links

         Description: The links of this object to other addressable
         objects.  Any property may be replaced by a link to an object
         with the same type as the property it replaces.

         Type: List of Link objects

         Mandatory: Yes

6.4.2.1.  JSON Example

   A downstream CDN may request the HostIndex and receive the following
   object of type "application/cdni.HostIndex+json":

   {
     "hosts": [
       {
         "host": "video.example.com",
         "links": [
           {
             "rel": "host-metadata",
             "type": "application/cdni.HostMetadata",
             "href": "http://metadata.example.ucdn.com/video"
           }



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         ]
       },
       {
         "host": "images.example.com",
         "links": [
           {
             "rel": "host-metadata",
             "type": "application/cdni.HostMetadata",
             "href": "http://metadata.ucdn.example.com/images"
           }
         ]
       }
     ]
   }


   If the incoming request has a Host header with "video.example.com"
   then the downstream CDN would fetch from the next metadata object
   from "http://metadata.ucdn.example.com/video" expecting a MIME type
   of "application/cdni.HostMetadata+json":

   {
     "metadata": [
       {
         "type": "application/cdni.SourceMetadata",
         "value": {
           "sources": [
             {
               "links": [{
                 "rel": "auth",
                 "type": "application/cdni.Auth",
                 "href": "http://metadata.ucdn.example.com/auth1234"
               }],
               "endpoint": "acq1.ucdn.example.com",
               "protocol": "ftp"
             },
             {
               "links": [{
                 "rel": "auth",
                 "type": "application/cdni.Auth",
                 "href": "http://metadata.ucdn.example.com/auth1234"
               }],
               "endpoint": "acq2.ucdn.example.com",
               "protocol": "http"
             }
           ]
         }
       },



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       {
         "type": "application/cdni.LocationACL",
         "value": {
           "locations": [
             {
               "locations": [
                 { "iprange": "192.168.0.0/16" }
               ],
               "action": "deny"
             }
           ]
         }
       },
       {
         "type": "application/cdni.ProtocolACL",
         "value": {
           "protocols": [
             {
               "protocols": [
                 "ftp"
               ],
               "action": "deny"
             }
           ]
         }
       }
     ],
     "paths": [
       {
         "path-pattern": {
           "pattern": "/videos/trailers/*"
         },
         "links": [{
           "rel": "path-metadata",
           "type": "application/cdni.PathMetadata",
           "href": "http://metadata.ucdn.example.com/videos/trailers"
         }]
       },
       {
         "path-pattern": {
           "pattern": "/videos/movies/*"
         },
         "links": [{
           "rel": "pathmetadata",
           "type": "application/cdni.PathMetadata",
           "href": "http://metadata.ucdn.example.com/videos/movies"
         }]
       }



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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.com/video/movies" with an expected type of
   "application/cdni.PathMetadata":

   {
     "metadata": [],
     "paths": [
       {
         "path-pattern": {
           "pattern": "/videos/movies/hd/*"
         },
         "links": [{
           "rel": "pathmetadata",
           "type": "application/cdni.PathMetadata",
           "href": "http://metadata.ucdn.example.com/videos/movies/hd"
         }]
       }
     ]
   }


   Finally, if the path of the requested resource also matches the "/
   videos/movies/hd/*" pattern, the downstream CDN would also fetch the
   following object from "http://metadata.ucdn.example.com/videos/movies
   /hd" with MIME type "application/cdni.PathMetadata":

   {
     "metadata": [
       {
         "type": "application/cdni.TimeWindowACL",
         "value": {
           "times": [
             "times": [
               {
                 "start": "1213948800",
                 "end": "1327393200"
               }
             ],
             "type": "allow"
           ]
         }
       }
     ]



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   }


6.5.  Extensibility

   The set of property Metadata may be extended with proprietary and/or
   custom property Metadata.  The GenericMetadata object defined in
   Section 4.1.7 allows any Metadata property to be included in either
   the HostMetadata or PathMetadata lists.  As described in Section 3.4,
   any proprietary and/or custom property Metadata SHOULD be identified
   by the "ext." prefix in an appropriately descriptive type which
   conveys the organization defining the property Metadata and the
   function of the property Metadata.

   Note: Identification of the property Metadata defining organization
   in the property Metadata type decreases the possibility of property
   Metadata type collision.  The fully-qualified domain name of the
   organization in reverse order may be used for this purpose.

6.5.1.  Metadata Enforcement

   At any given time, the set of property Metadata supported by the uCDN
   may not match the set of property Metadata supported by the dCDN.
   The uCDN may or may not know which property Metadata the dCDN
   supports.  In cases where the uCDN supports Metadata that the dCDN
   does not, the dCDN MUST be aware of any Metadata marked as
   "mandatory-to-enforce".  If a CDN does not understand or is unable to
   perform the functions associated with any "mandatory-to-enforce"
   Metadata, the CDN MUST NOT service any requests for the corresponding
   content.

   Any standard which defines a new GenericMetadata Type SHOULD also
   define whether or not the new metadata is mandatory-to-enforce.

   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 evaluate all Metadata
   associated with content requests and reject any requests where
   "mandatory-to-enforce" Metadata associated with the content cannot be
   enforced.

6.5.2.  Metadata Override




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   It is possible that new Metadata definitions may obsolete or override
   existing property Metadata (e.g., a future revision of the CDNI
   Metadata interface may redefine the Auth Metadata or a custom vendor
   extension may implement an alternate Auth Metadata option).  If
   multiple Metadata (e.g., cdni.v2.Auth, ext.vendor1.Auth, and
   ext.vendor2.Auth) all override an existing Metadata (e.g., cdni.Auth)
   and all are marked as "mandatory-to-enforce", it may be ambiguous
   which Metadata should be applied, especially if the functionality of
   the Metadata conflict.

   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.

6.6.  Versioning

   The version of CDNI Metadata Structural objects is specified by the
   HTTP Content-Type header.  Upon responding to a request for an
   object, a metadata server MUST include a Content-Type header with the
   MIME-type and verison number of the object.  HTTP requests sent to a
   metadata server SHOULD include an Accept header with the MIME-type
   and version of the expected object.  Unless stated otherwise, the
   verison of each object defined by this document is version 1.  For
   example: "Content-Type: application/cdni.HostIndex.v1":.

   GenericMetadata objects include a "type" property which specifies the
   MIME-type of the GenericMetadata value.  This MIME-type should also
   include a version.  Any document which defines a new type of
   GenericMetadata should specify the version number which it describes.
   For example: "application/cdni.Location.v1".

7.  IANA Considerations

   This document requests the registration of the "application/cdni"
   MIME Media Type under the IANA MIME Media Type registry (http://
   www.iana.org/assignments/media-types/index.html).

7.1.  GenericMetadata Type Registry




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   CDNI Metadata is distributed as a list of GenericMetadata objects
   which specify a type field and a type-specific value field, as
   described in Section 4.1.7.  In order to prevent namespace collisions
   for GenericMetadata object types a new IANA registry is requested for
   "CDNI GenericMetadata Types" namespace.  The namespace shall be split
   into two partitions: standard and vendor defined.  As described in
   Section 4.1.7 and Section 6.5, the vendor defined namespace partition
   SHOULD use a namespace prefix of "ext.", while the standard namespace
   partition MUST NOT.

   The standard namespace partition MUST conform to the "RFC Required"
   policy as defined in [RFC5226].  The vendor defined namespace
   partition should be further partitioned into vendor specific
   partitions with the prefix "ext.vendor_name.".  The vendor defined
   partition SHOULD conform to the "Expert Review" policy as defined in
   [RFC5226].  The expert review is simply to prevent namespace
   hoarding.  The vendor specific partitions MAY conform to the "First
   Come First Served" policy as defined in [RFC5226], however, vendors
   defining new GenericMetadata types which conflict with other
   GenericMetadata types SHOULD follow the guidelines for the
   "Specification Required" policy as defined in [RFC5226].

   The following table defines the initial values for the standard
   partition:

                    +----------------+---------------+
                    | type name      | Specification |
                    +----------------+---------------+
                    | SourceMetadata | RFCthis       |
                    | LocationACL    | RFCthis       |
                    | TimeWindowACL  | RFCthis       |
                    | ProtocolACL    | RFCthis       |
                    | Auth           | RFCthis       |
                    | Cache          | RFCthis       |
                    | Grouping       | RFCthis       |
                    +----------------+---------------+


7.1.1.  GenericMetadata Sub-Registries

   Some of the initial standard GenericMetadata objects contain
   enumerated types which require registration (i.e., LocationACL
   footprint types, ProtocolACL protocols, and Auth protocols).  The
   following sections define the initial values for these
   GenericMetadata type sub-registries.

7.1.1.1.  Footprint Sub-Registry




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   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 MUST
   conform to the "Expert Review" policy as defined in [RFC5226].  The
   expert review should 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 type values:

   +---------------+---------------------------------------------------+
   | type name     | definition                                        |
   +---------------+---------------------------------------------------+
   | IPv4          | Single IPv4 address                               |
   | IPv6          | Single IPv6 address                               |
   | IPv4Range     | List of contiguous IPv4 addresses denoted by a    |
   |               | start address and an end address separated by a   |
   |               | dash (e.g., 192.168.0.1-192.168.0.20), inclusive. |
   | IPv6Range     | List of contiguous IPv6 addresses denoted by a    |
   |               | start address and an end address separated by a   |
   |               | dash (e.g., fc80::0001-fc80::0014), inclusive.    |
   | IPv4CIDR      | IPv4 address block using slash prefix length      |
   |               | notation (e.g., 192.168.0.16/28).                 |
   | IPv6CIDR      | IPv6 address block using slash prefix length      |
   |               | notation (e.g., fc80::0010/124).                  |
   | ASN           | Autonomous System (AS) Number                     |
   | CountryCode   | ISO 3166-1 alpha-2 code                           |
   | DVDRegion     | DVD Region code (i.e., integer in the range 0-6). |
   +---------------+---------------------------------------------------+


7.1.1.2.  Protocol Sub-Registry

   The "CDNI Metadata Protocols" namespace defines the valid Protocol
   object values in Section 4.3.2, used by the SourceMetadata and
   ProtocolACL objects.  Additions to the Protocol namespace MUST
   conform to the "Expert Review" policy as defined in [RFC5226].  The
   expert review should verify that new type definitions do not
   duplicate existing type definitions and prevent gratuitous additions
   to the namespace.

   The following table defines the initial Protocol values:

                      +---------------+------------+
                      | protocol name | definition |
                      +---------------+------------+
                      | HTTP          | TBD        |
                      | HTTPS         | TBD        |



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                      | RTSP          | TBD        |
                      | RTMP          | TBD        |
                      +---------------+------------+


7.1.1.3.  Authentication Sub-Registry

   The "CDNI Metadata Auth" namespace defines the valid Auth object
   types used by the Auth object in Section 4.2.6.  Additions to the
   Footprint type namespace MUST conform to the "Expert Review" policy
   as defined in [RFC5226].  The expert review should verify that new
   type definitions do not duplicate existing type definitions and
   prevent gratuitous additions to the namespace.

   The following table defines the initial Auth type values:

   +------------------+------------------------------------------------+
   | type name        | definition                                     |
   +------------------+------------------------------------------------+
   | credentials      | Simple username and password authentication as |
   |                  | defined by Section 4.2.6.1.                    |
   +------------------+------------------------------------------------+


8.  Security Considerations

   The CDNI Metadata Interface is expected to be secured as a function
   of the transport protocol (e.g. HTTP authentication [RFC2617], HTTPS
   [RFC2818], or inter-domain IPSec).

   If a malicious metadata server is contacted by a downstream CDN, the
   malicious server may provide metadata to the downstream CDN which
   denies service for any piece of content to any user agent.  The
   malicious server may also provide metadata which directs a downstream
   CDN to a malicious origin server instead of the actual origin server.
   The dCDN is expected to authenticate the server to prevent this
   situation (e.g. by using HTTPS and validating the server's
   certificate).

   A malicious metadata client could request metadata for a piece of
   content from an upstream CDN.  The metadata information may then be
   used to glean information regarding the uCDN or to contact an
   upstream origin server.  The uCDN is expected to authenticate client
   requests to prevent this situation.

9.  Acknowledgements





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   The authors would like to thank David Ferguson and Francois le
   Faucheur for their valuable comments and input to this document.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
              Leach, P., Luotonen, A., and L. Stewart, "HTTP
              Authentication: Basic and Digest Access Authentication",
              RFC 2617, June 1999.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952, August 2010.

10.2.  Informative References

   [I-D.ietf-cdni-framework]
              Peterson, L. and B. Davie, "Framework for CDN
              Interconnection", draft-ietf-cdni-framework-03 (work in
              progress), February 2013.

   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements", draft-ietf-cdni-
              requirements-05 (work in progress), February 2013.

   [I-D.zyp-json-schema]
              Zyp, K. and G. Court, "A JSON Media Type for Describing
              the Structure and Meaning of JSON Documents", draft-zyp-
              json-schema-03 (work in progress), November 2010.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.




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   [RFC4151]  Kindberg, T. and S. Hawke, "The 'tag' URI Scheme", RFC
              4151, October 2005.

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, December 2005.

   [RFC6707]  Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", RFC 6707, September 2012.

   [XML-BASE]
              Marsh, J., Ed. and R. Tobin, Ed., "XML Base (Second
              Edition) - http://www.w3.org/TR/xmlbase/", January 2009.

Appendix A.  Relationship to the CDNI Requirements

   Section 6 of [I-D.ietf-cdni-requirements] lists the requirements for
   the CDNI Metadata Distribution interface.  This section outlines
   which of those requirements are met by the CDNI Metadata interface
   specified in this document.

   All metadata requirements are met either directly or indirectly by
   the CDNI Metadata Interface described in this document, with the
   clarifications or exceptions described in the following paragraphs.

   Requirements related to pre-positioning of metadata are met by this
   document on the assumption that other CDNI Interfaces are to be used
   by the upstream CDN to trigger the pre-positioning of metadata by the
   downstream CDN via the CDNI Metadata Interface.  Triggering metadata
   pre-positioning is beyond the scope of the CDNI Metadata interface.
   However, the interface as described by this document supports pulling
   metadata on-demand for the purpose of pre-positioning.

   Requirement META-7 relating to modification of metadata by the
   upstream CDN is met both by allowing timeouts on the cacheability of
   metadata objects and by allowing other CDNI interfaces to initiate a
   refetch or purge of metadata.

   Requirement META-18 relating to surrogate cache behavior parameters
   is supported via extensibility.  However, the example parameters in
   META-18 are not described in this document.

Authors' Addresses








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   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


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

   Email: gwatson@velocix.com


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

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


   Kent Leung
   Cisco Systems
   3625 Cisco Way
   San Jose  95134
   USA

   Phone: +1 408 526 5030
   Email: kleung@cisco.com






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   Kevin J. Ma
   Azuki Systems, Inc.
   43 Nagog Park
   Acton, MA  01720
   USA

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











































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