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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: January 3, 2015                                    M. Caulfield
                                                                K. Leung
                                                           Cisco Systems
                                                                   K. Ma
                                                                Ericsson
                                                            July 2, 2014


                      CDN Interconnection Metadata
                      draft-ietf-cdni-metadata-07

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 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 January 3, 2015.





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Copyright Notice

   Copyright (c) 2014 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
     1.2.  Supported Metadata Capabilities . . . . . . . . . . . . .   4
   2.  Design Principles . . . . . . . . . . . . . . . . . . . . . .   5
   3.  CDNI Metadata Data Model  . . . . . . . . . . . . . . . . . .   6
     3.1.  HostIndex, HostMetadata and PathMetadata objects  . . . .   7
     3.2.  Generic CDNI Metadata Object Properties . . . . . . . . .  11
     3.3.  Metadata Inheritance and Override . . . . . . . . . . . .  14
   4.  Encoding-Independent CDNI Metadata Object Descriptions  . . .  15
     4.1.  Descriptions of the CDNI Structural Metadata Objects  . .  16
       4.1.1.  HostIndex . . . . . . . . . . . . . . . . . . . . . .  16
       4.1.2.  HostMatch . . . . . . . . . . . . . . . . . . . . . .  16
       4.1.3.  HostMetadata  . . . . . . . . . . . . . . . . . . . .  17
       4.1.4.  PathMatch . . . . . . . . . . . . . . . . . . . . . .  17
       4.1.5.  PathMetadata  . . . . . . . . . . . . . . . . . . . .  18
       4.1.6.  PatternMatch  . . . . . . . . . . . . . . . . . . . .  18
       4.1.7.  GenericMetadata . . . . . . . . . . . . . . . . . . .  19
     4.2.  Description of the CDNI Generic Metadata Objects  . . . .  20
       4.2.1.  Source Metadata . . . . . . . . . . . . . . . . . . .  20
         4.2.1.1.  Source  . . . . . . . . . . . . . . . . . . . . .  21
       4.2.2.  LocationACL Metadata  . . . . . . . . . . . . . . . .  21
         4.2.2.1.  LocationRule  . . . . . . . . . . . . . . . . . .  22
         4.2.2.2.  Footprint . . . . . . . . . . . . . . . . . . . .  22
       4.2.3.  TimeWindowACL Metadata  . . . . . . . . . . . . . . .  23
         4.2.3.1.  TimeWindowRule  . . . . . . . . . . . . . . . . .  23
         4.2.3.2.  TimeWindow  . . . . . . . . . . . . . . . . . . .  24
       4.2.4.  ProtocolACL Metadata  . . . . . . . . . . . . . . . .  24
         4.2.4.1.  ProtocolRule  . . . . . . . . . . . . . . . . . .  24
       4.2.5.  Authorization Metadata  . . . . . . . . . . . . . . .  25
       4.2.6.  Auth  . . . . . . . . . . . . . . . . . . . . . . . .  25
         4.2.6.1.  Credentials Auth Type . . . . . . . . . . . . . .  26



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       4.2.7.  Cache . . . . . . . . . . . . . . . . . . . . . . . .  26
       4.2.8.  Grouping  . . . . . . . . . . . . . . . . . . . . . .  26
     4.3.  CDNI Metadata Simple Data Type Descriptions . . . . . . .  27
       4.3.1.  Link  . . . . . . . . . . . . . . . . . . . . . . . .  27
       4.3.2.  Protocol  . . . . . . . . . . . . . . . . . . . . . .  28
       4.3.3.  Endpoint  . . . . . . . . . . . . . . . . . . . . . .  28
       4.3.4.  URI . . . . . . . . . . . . . . . . . . . . . . . . .  28
       4.3.5.  Time  . . . . . . . . . . . . . . . . . . . . . . . .  28
   5.  CDNI Metadata Capabilities  . . . . . . . . . . . . . . . . .  28
     5.1.  Protocol ACL Capabilities . . . . . . . . . . . . . . . .  29
     5.2.  Authorization Metadata Capabilities . . . . . . . . . . .  29
   6.  CDNI Metadata interface . . . . . . . . . . . . . . . . . . .  29
     6.1.  Transport . . . . . . . . . . . . . . . . . . . . . . . .  30
     6.2.  Retrieval of CDNI Metadata resources  . . . . . . . . . .  31
     6.3.  Bootstrapping . . . . . . . . . . . . . . . . . . . . . .  32
     6.4.  Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  32
       6.4.1.  MIME Media Types  . . . . . . . . . . . . . . . . . .  33
       6.4.2.  JSON Encoding of Objects  . . . . . . . . . . . . . .  33
         6.4.2.1.  Encoded CDNI Metadata Example . . . . . . . . . .  34
     6.5.  Extensibility . . . . . . . . . . . . . . . . . . . . . .  38
       6.5.1.  Metadata Enforcement  . . . . . . . . . . . . . . . .  38
       6.5.2.  Metadata Override . . . . . . . . . . . . . . . . . .  39
     6.6.  Versioning  . . . . . . . . . . . . . . . . . . . . . . .  39
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  40
     7.1.  GenericMetadata Type Registry . . . . . . . . . . . . . .  40
       7.1.1.  GenericMetadata Sub-Registries  . . . . . . . . . . .  42
         7.1.1.1.  Footprint Sub-Registry  . . . . . . . . . . . . .  42
         7.1.1.2.  Protocol Sub-Registry . . . . . . . . . . . . . .  42
         7.1.1.3.  Authentication Sub-Registry . . . . . . . . . . .  43
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  44
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  44
   10. Contributing Authors  . . . . . . . . . . . . . . . . . . . .  44
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  45
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  45
     11.2.  Informative References . . . . . . . . . . . . . . . . .  45
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  46

1.  Introduction

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

   The CDNI Metadata interface is discussed in [I-D.ietf-cdni-framework]
   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).  [I-D.ietf-cdni-framework] describes each



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   interface, and the relationships between them.  The requirements for
   the CDNI metadata interface are specified in
   [I-D.ietf-cdni-requirements].

   The CDNI metadata associated with a piece of content (or with a set
   of content) 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.

   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
      Redirection interface.

   o  Content requests received directly from User Agents.

   Specifically, this document specifies:

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

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

   o  A 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.

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 [I-D.ietf-cdni-requirements].





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   The following high-level functionality is configured via the metadata
   described 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 allow for future additions to this list.

   This document supports HTTPv1.1 for delivery and both HTTPv1.1 and
   HTTPv1.1. over TLS for acquisition.  All metadata is described in a
   protocol-agnostic manner.

   Supporting unencrypted HTTPv2.0 for delivery (or unencrypted HTTPv2.0
   or HTTPv2.0 over TLS for acquisition) only requires the registration
   of these protocol names in the CDNI Metadata Protocol Sub-Registry.

   Supporting HTTPv1.1 over TLS or HTTPv2.0 over TLS for delivery
   requires specifying additional metadata objects to carry the
   properties required to establish a TLS session, for example metadata
   to describe the certificate to present 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.





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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.  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
   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 content from an upstream
   CDN, authorize access to content, 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 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 is processing User Agent requests for



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   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
   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.

   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 and PathMetadata objects

   A HostIndex object contains (or references) 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 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 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



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   up the requested Hostname (or IP address) against the HostMatch
   entries in the HostIndex, from there it can find HostMetadata which
   describes properties for a host and PathMetadata which may override
   those properties for given URI paths within the host.

   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+-------(*)------+
   +---------+      +---------+      +------+-----+                |
                                            |                      |
                                           (*)                     |
                                            |                      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)

   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)

   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 (or IP    |
   |                 | address) to match against a requested host, and |
   |                 | contains (or references) a HostMetadata object  |
   |                 | which contains (or references) 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 (inside a  |



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   |                 | PatternMatch object which PathMatch object      |
   |                 | contains or references) 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.   |
   |                 | For example, a PathMatch object may include a   |
   |                 | PatternMatch object containing a pattern for    |
   |                 | the path "/movies/*" and may reference a        |
   |                 | PathMetadata object which contains (or          |
   |                 | references) the CDNI Metadata for content with  |
   |                 | that path.                                      |
   | PatternMatch    | A PatternMatch object contains the pattern      |
   |                 | string and flags that describe the URI path     |
   |                 | that a PathMatch applies to.                    |
   | PathMetadata    | A PathMetadata object contains (or references)  |
   |                 | the CDNI GenericMetadata objects for content    |
   |                 | served with the associated URI path (defined in |
   |                 | a PathMatch object). A PathMetadata object may  |
   |                 | also contain (or reference) 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 (or           |
   |                 | references) 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, but   |
   |                 | SHOULD NOT contain references to other CDNI     |
   |                 | Metadata objects. The member objects of a       |
   |                 | specific CDNI Metadata object MAY be referenced |
   |                 | by the GenericMetadata object.                  |
   +-----------------+-------------------------------------------------+





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      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 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 may pass through
   "mandatory-to-enforce" metadata to a downstream CDN.  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
   which requires translation, transparent redistribution of the uCDN
   Metadata values may 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 may 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 property 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



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   by the transit CDN.  A CDN MUST NOT attempt to use metadata that has
   been marked as "incomprehensible" by a uCDN.

   [[Editors' Note: Do we need to clarify what is meant by
   "Redistribution safety MUST be specified"?  In Section 4.1.7
   (GenericMetadata) we say that StR is not Mandatory-to-Specify and
   defaults to StR=True.  A strict interpretation of "MUST be specified"
   could be that StR is Mandatory-to-Specify and could lead to dCDNs
   rejecting requests/metadata that leave it out as the default applies
   which would be an issue for interop.  Maybe change first sentence to
   "If a GenericMetadata object cannot be redistributed safely then it
   MUST be marked as not safe-to-redistribute (i.e.  Safe-to-
   redistribute is set to False).]]

   Transit CDNs MUST NOT change the value of "mandatory-to-enforce" or
   "safe-to-redistribute" when propogating 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.

   [[Editors' Note: Should a transit CDN be allowed to change the value
   of "mandatory-to-enforce" or "safe-to-redistribute"?  Changing MtE
   from false to true should be safe from an enforcement perspective as
   it makes delivery more restrictive?  Changing StR may be ok,
   depending upon what the metadata is (e.g., perhaps URL rewrite is
   only needed in certain cases and the transit CDN is the one to make
   that decision)?  For simplicity, prohibiting transit CDNs from
   changing MtE or StR seems like the simplest approach.]]

   The following table describes the action to be taken by a transit CDN
   (tCDN) for the different "mandatory-to-enforce" (MtE) and "safe-to-
   redistribute" (StR) cases, when the tCDN either does or does not
   understand the metadata in question:


















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   +-------+-------+------------+--------------------------------------+
   | MtE   | StR   | Metadata   | Actions allowed                      |
   |       |       | Understood |                                      |
   +-------+-------+------------+--------------------------------------+
   | False | True  | True       | Can serve and redistribute.          |
   | False | True  | False      | Can serve and redistribute.          |
   | False | False | False      | Can serve but MUST set               |
   |       |       |            | "incomprehensible" to True when      |
   |       |       |            | redistributing.                      |
   | False | False | True       | Can serve. Can redistribute either   |
   |       |       |            | by transforming not StR metadata (if |
   |       |       |            | the CDN know how to do so safely),   |
   |       |       |            | otherwise MUST set                   |
   |       |       |            | "incomprehensible" to True when      |
   |       |       |            | redistributing.                      |
   | True  | True  | True       | Can serve and can redistribute.      |
   | True  | True  | False      | MUST NOT serve but can redistribute. |
   | True  | False | True       | Can serve and can redistribute.      |
   | True  | False | False      | MUST NOT serve. MUST set             |
   |       |       |            | "incomprehensible" to True when      |
   |       |       |            | redistributing.                      |
   +-------+-------+------------+--------------------------------------+

   The following table describes the action to be taken by a dCDN for
   the different "mandatory-to-enforce" (MtE), "safe-to-redistribute"
   (StR) and "incomprehensible" (Inc) cases, when the dCDN either does
   or does not understand the metadata in question:

   +-------+-------+------------+------------------+-------------------+
   | MtE   | StR   | Metadata   | Incomprehensible | Actions allowed   |
   |       |       | Understood |                  |                   |
   +-------+-------+------------+------------------+-------------------+
   | False | True  | True       | False            | Can serve.        |
   | False | True  | True       | True             | Can serve but     |
   |       |       |            |                  | MUST NOT          |
   |       |       |            |                  | interpret/apply   |
   |       |       |            |                  | any metadata      |
   |       |       |            |                  | marked            |
   |       |       |            |                  | incomprehensible. |
   | False | True  | False      | False            | Can serve.        |
   | False | True  | False      | True             | Can serve but     |
   |       |       |            |                  | MUST NOT          |
   |       |       |            |                  | interpret/apply   |
   |       |       |            |                  | any metadata      |
   |       |       |            |                  | marked            |
   |       |       |            |                  | incomprehensible. |
   | False | False | True       | False            | Can serve.        |
   | False | False | True       | True             | Can serve but     |



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

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



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   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".

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 a base set of core metadata
   objects which may be contained within a GenericMetadata object.
   These objects are described as property objects as they define the
   structure, semantics, and enforcement options for specific properties
   of the metadata being described.  Property objects govern how User
   Agent requests for content are handled.  Property objects may be
   composed of or contain references to other property sub-objects (i.e.
   property objects contained within or referenced by the property
   object that refers to that property sub-object).  In those cases the
   value of the property sub-objects can be either a complete serialized
   representation of the sub-object, or a Link object that contains a
   URI and relationship 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 metadata
   objects specified in this document with additional standards based or
   vendor specific property objects that may be defined in the future in
   separate documents.

   Downstream CDNs 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, which
   may restrict the content which that 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 the content they are describing requires.

   Note: In the following sections, the term "mandatory-to-specify" is
   used to convey which property sub-objects MUST be specified for a
   given structural or property object.  When mandatory-to-specify is
   set to true on a sub-object, it implies that if the property object



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   containing that property sub-object is specified, then the mandatory-
   to-specify property sub-object MUST also be specified, e.g., a
   HostMatch property object without a host to match against does not
   make sense, therefore, the host is mandatory-to-specify inside a
   HostMatch property object.

4.1.  Descriptions of the CDNI Structural Metadata Objects

   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 (or references) 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 or
   references a HostMetadata object 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



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         Mandatory-to-Specify: Yes.

4.1.3.  HostMetadata

   The HostMetadata object contains (or references) 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.  Path patterns (PathMatch
         objects) MUST be evaluated in the order they appear and the
         first PathMatch object that matches the content request being
         process is applied.

         Type: List of PathMatch objects

         Mandatory-to-Specify: No.

4.1.4.  PathMatch

   The PathMatch object contains (or references) 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.




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         Type: PathMetadata

         Mandatory-to-Specify: Yes.

4.1.5.  PathMetadata

   A PathMetadata object contains (or reference) the CDNI Metadata
   properties for content served with the associated URI path (defined
   in a PathMatch object) and possibly children PathMatch objects.

   Note that if DNS-based redirection is employed, then any metadata at
   the PathMetadata level or below will be inaccessible at request
   routing time because only the content request hostname is available
   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 \?. All other characters are treated as
         literals.

         Type: String

         Mandatory-to-Specify: Yes.



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      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.  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 an abstraction for managing individual
   CDNI Metadata properties in an opaque manner.

      Property: generic-metadata-type

         Description: CDNI Metadata property object type.

         Type: String

         Mandatory-to-Specify: Yes.

      Property: generic-metadata-value

         Description: CDNI Metadata property 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



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         Mandatory-to-Specify: No.  Default is to treat metadata as
         mandatory to enforce.

      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.

4.2.  Description of the CDNI Generic Metadata Objects

   The property 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 Media Type as defined in [[REF]].

   [[Editors' note: We don't specify media types for the Generic
   Metadata object we define anywhere.  Need to do that - at a minimum
   in the IANA section, but should we introduce/explain them elsewhere
   in the document too?]]

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.

   Endpoints within a source should be treated as equivalent/equal so
   one can specify a list of sources in preference order and for each
   source/preference rank one can specify a list of endpoints that are
   equivalent, e.g. a pool of servers that are not behind a load
   balancer.

      Property: sources

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

         Type: List of Source objects

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



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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.
         If multiple endpoints are specified they are all equal, i.e.
         the list is not in preference order, for example a pool of
         servers behind a load balancer.

         Type: List of EndPoint objects

         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.

   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



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   none of the listed footprints matches the User Agent's location then
   the result is an action of deny.

      Property: locations

         Description: Description: Access control list which allows or
         blocks 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 Footprint 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

   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: footprint-type

         Description: Registered footprint type (see Section 7.1.1.1).

         Type: String

         Mandatory-to-Specify: Yes.




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      Property: footprint-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: Description: Access control list which allows or
         blocks 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: windows

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

         Type: List of TimeWindow objects

         Mandatory-to-Specify: Yes.

      Property: action

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

         Type: Enumeration [allow|deny]

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








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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: Description: Access control list which allows or
         blocks 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.

      Property: protocols

         Description: List of protocols to which the rule applies.

         Type: List of protocol objects

         Mandatory-to-Specify: Yes.



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      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.

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: auth-type

         Description: Registered Auth type (see Section 7.1.1.3).

         Type: String

         Mandatory-to-Specify: Yes.

      Property: auth-value

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

         Type: String

         Mandatory-to-Specify: Yes.







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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.

         Type: List of String

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

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.



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         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 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.

         Type: URI

         Mandatory-to-Specify: Yes

      Property: metadata-object-type

         Description: The type of the object being referenced.

         Type: String

         Mandatory-to-Specify: No








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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

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].

   Type: String

4.3.4.  URI

   A URI as specified in [RFC3986].

   Type: String

4.3.5.  Time

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

   Type: Integer

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 the
   uCDN is likely to 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 the dCDN
   supports, prior to delegating any content requests to the 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




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   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)
   [I-D.ietf-cdni-framework] 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.

   This section describes the capabilities advertisement requirements
   for the metadata defined in this document.

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

   The Authorization object contains a list of Auth values.  The dCDN
   MUST advertise in its FCI capabilities which authorization types it
   supports.

   The definition of the corresponding capabilities and the protocol
   used to advertise them are outside the scope of this document and are
   expected to be specified as part of the CDNI Footprint and
   Capabilities Interface.

6.  CDNI Metadata interface

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





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   The interface can be used by a Downstream CDN to retrieve CDNI
   Metadata objects either

   o  Dynamically as required by the Downstream CDN to process received
      requests.  For example in response to a query from an Upstream CDN
      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 RESTful 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 Data Model (as described in
   Section 3 through Section 4).

   To retrieve CDNI metadata, a CDNI Metadata client (i.e. a client in
   the dCDN) first makes a HTTP GET request for the URI of the HostIndex
   which provides the CDNI Metadata client with a list of Hostnames for
   which the upstream CDN may delegate content delivery to the
   downstream CDN.  The CDNI Metadata client can then obtain any other
   CDNI Metadata objects by making a HTTP GET requests for any linked
   Metadats 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 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.

   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



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   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.  An 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.

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.

   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 needs to determine which upstream CDN'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 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 configured in, or discovered by, 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.

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 within a property of an
      addressable object.

   In the descriptions of objects we use the term "X contains Y" to mean
   that Y is either directly embedded in X or 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 made
   separately addressable.






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6.4.1.  MIME Media Types

   All MIME types for CDNI Metadata objects are prefixed with
   "application/cdni.".  The MIME type for each object then contains the
   object name of that object as defined by this document.  The object
   type name is followed by ".v" and the version number of the object
   type (e.g. ".v1").  Finally, the encoding type "+json" is appended.
   Table 3 3 lists a few examples of the MIME Media Type for some object
   (resource) that are retrievable through the CDNI Metadata interface.

         +--------------+---------------------------------------+
         | Data Object  | MIME Media Type                       |
         +--------------+---------------------------------------+
         | HostIndex    | application/cdni.HostIndex.v1+json    |
         | HostMatch    | application/cdni.HostMatch.v1+json    |
         | HostMetadata | application/cdni.HostMetadata.v1+json |
         | PathMatch    | application/cdni.PathMatch.v1+json    |
         | PathMetadata | application/cdni.PathMetadata.v1+json |
         | Source       | application/cdni.Source.v1+json       |
         | LocationACL  | application/cdni.LocationACL.v1+json  |
         | LocationRule | application/cdni.LocationRule.v1+json |
         +--------------+---------------------------------------+

        Table 3: Example MIME Media Types for CDNI Metadata objects

6.4.2.  JSON Encoding of Objects

   A CDNI Metadata objects is encoded as a JSON object 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
   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.  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 specified for each object type, the
   keys defined below may be present in any object.

      Key: base





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         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 response MUST be
         absolute URLs.

         Type: URI

         Mandatory: No

      Key: _links

         Description: The links from this object to other addressable
         objects.  Any property whose value is an object may be replaced
         by a link to an object with the same type as the property it
         replaces.  The keys of the _links dictionary are the names of
         the properties being replaced.  The values of the dictionary
         are Link objects with href set to the URI of the object and
         type set to the MIME type of the object being replaced.

         Type: Dictionary object of Link objects

         Mandatory: Yes

6.4.2.1.  Encoded CDNI Metadata Example

   [[Editor's Note: We need to double-check that the example(s) below
   are correct and use the latest property names/values/structures
   defined in the document.]]

   A downstream CDN may request the HostIndex and receive the following
   object of type "application/cdni.HostIndex.v1+json":




















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

   If the incoming request has a Host header with "video.example.com"
   then the downstream CDN would fetch the next metadata object from
   "http://metadata.ucdn.example/host1234" expecting a MIME type of
   "application/cdni.HostMetadata.v1+json":

{
  "metadata": [
    {
      "generic-metadata-type": "application/cdni.SourceMetadata.v1+json",
      "generic-metadata-value": {
        "sources": [
          {
            "_links": {
              "auth": {
                "auth-type": "application/cdni.Auth.v1+json",
                "href": "http://metadata.ucdn.example/auth1234"
              }
            },
            "endpoint": "acq1.ucdn.example",
            "protocol": "ftp"
          },
          {
            "_links": {
              "auth": {
                "auth-type": "application/cdni.Auth.v1+json",



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                "href": "http://metadata.ucdn.example/auth1234"
              }
            },
            "endpoint": "acq2.ucdn.example",
            "protocol": "http"
          }
        ]
      }
    },
    {
      "generic-metadata-type": "application/cdni.LocationACL.v1+json",
      "generic-metadata-value": {
        "locations": [
          {
            "locations": [
              {
                "footprint-type": "IPv4CIDR",
                "footprint-value": "192.168.0.0/16"
              }
            ],
            "action": "deny"
          }
        ]
      }
    },
    {
      "generic-metadata-type": "application/cdni.ProtocolACL.v1+json",
      "generic-metadata-value": {
        "protocols": [
          {
            "protocols": [
              "ftp"
            ],
            "action": "deny"
          }
        ]
      }
    }
  ],
  "paths": [
    {
      "path-pattern": {
        "pattern": "/video/trailers/*"
      },
      "_links": {
        "path-metadata": {
          "type": "application/cdni.PathMetadata.v1+json",
          "href": "http://metadata.ucdn.example/host1234/pathABC"



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        }
      }
    },
    {
      "path-pattern": {
        "pattern": "/video/movies/*"
      },
      "_links": {
        "path-metadata": {
          "type": "application/cdni.PathMetadata.v1+json",
          "href": "http://metadata.ucdn.example/host1234/pathDCE"
        }
      }
    }
  ]
}

   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 type
   of "application/cdni.PathMetadata.v1+json":

   {
     "metadata": [],
     "paths": [
       {
         "path-pattern": {
           "pattern": "/videos/movies/hd/*"
         },
         "_links": {
           "pathmetadata": {
             "type": "application/cdni.PathMetadata.v1+json",
             "href":
               "http://metadata.ucdn.example/host1234/pathABC/path123"
           }
         }
       }
     ]
   }

   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/host1234/movies/hd" with MIME type
   "application/cdni.PathMetadata.v1+json":






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{
  "metadata": [
    {
      "generic-metadata-type": "application/cdni.TimeWindowACL.v1+json",
      "generic-metadata-value": {
        "times": [
          "windows": [
            {
              "start": "1213948800",
              "end": "1327393200"
            }
          ],
          "action": "allow"
        ]
      }
    }
  ]
}

6.5.  Extensibility

   The set of property Metadata may be extended with additional
   (standards based or vendor specific) 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.  It is expected that additional property Metadata will be
   defined in the future and that the documents defining those property
   Metadata will be registered in the CDNI GenericMetadata Types
   registry Section 7.1.

   Note: Identification, within the type name defined for a property
   Metadata object, of the organization that defined the extension
   property Metadata decreases the possibility of property Metadata type
   collisions.

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 the cases where the uCDN supports Metadata that the dCDN does not,
   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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   Any specification which defines a new GenericMetadata Type MUST also
   define whether or not the new metadata is "mandatory-to-enforce" and
   whether or not it is "safe-to-distribute".

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

6.5.2.  Metadata Override

   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, vendor1.Auth, and
   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 conveyed inside
   the MIME-Type that is included in 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 containing the version
   number of the object.  HTTP requests sent to a metadata server SHOULD



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   include an Accept header with the MIME-type (which includes the
   version) of the expected object.  Metadata clients can specify
   multiple MIME-types in the Accept header, for example if a metadata
   client is capable of processing two different versions of the same
   type of object (defined by different MIME-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.HostIndex.v1+json".

   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 MUST specify the version number which it describes.
   For example: "application/cdni.Location.v1+json".

7.  IANA Considerations

   This document requests the registration of the prefix "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

   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
   the "CDNI GenericMetadata Types" namespace.  The namespace shall be
   split into two partitions: standard and optional.

   The standard namespace partition is intended to contain mandatory to
   implement capabilities and conforms to the "IETF Review" policy as
   defined in [RFC5226].  The registry contains the generic metadata
   type name, the RFC number of the specification defining the metadata
   type, the version number of the GenericMetadata set to which the
   standard capability applies, and boolean values indicating whether or
   not the new type is considered "mandatory-to-enforce" or "safe-to-
   redistribute" (as defined in Section 4.1.7).

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










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        +----------------+---------------+---------+------+------+
        | Type name      | Specification | Version | MTE  | STR  |
        +----------------+---------------+---------+------+------+
        | SourceMetadata | RFCthis       | 1       | true | true |
        | LocationACL    | RFCthis       | 1       | true | true |
        | TimeWindowACL  | RFCthis       | 1       | true | true |
        | ProtocolACL    | RFCthis       | 1       | true | true |
        | Auth           | RFCthis       | 1       | true | true |
        | Cache          | RFCthis       | 1       | true | true |
        | Grouping       | RFCthis       | 1       | true | true |
        +----------------+---------------+---------+------+------+

   The initial MI version number is set to 1.  All of the initial
   GenericMetadata types are considered mandatory to implement for
   version 1.  The version field should be incremented when new
   GenericMetadata type sets are added to the registry.

   The "optional" namespace partition conforms to the "Expert Review"
   policy as defined in [RFC5226].  The expert review is intended to
   prevent namespace hoarding and to prevent the definition of redundant
   GenericMetadata types.  Vendors defining new GenericMetadata types
   which conflict with existing GenericMetadata types follow the
   guidelines for the "Specification Required" policy as defined in
   [RFC5226].  The Version field in the registry is set to "-1"
   (negative one) for non-standard GenericMetadata types.

   As with the initial GenericMetadata types defined in Section 4.2,
   future GenericMetadata type registrations will specify the
   information necessary for constructing and decoding the
   GenericMetadata object.  This information includes the list of
   properties contained within the GenericMetadata object, and for each
   property, the specification should include a description, a type, and
   whether or not the given property is mandatory to specify.

   Any document which defines a new GenericMetadata has to:

   1.  Allocate a new type in the GenericMetadata Type Registry
       (Section 7).  Generic Metadata types should be descriptive and
       may be hierarchnical to support aggregating groups of properties
       for the purpose of readability and for avoiding conflicts between
       vendor defined extensions.  A dotted alpha-numeric notation is
       suggested for human readability.

   2.  Define the set of properties associated with the new type.

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




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   4.  Specify whether or not the new type is "mandatory-to-enforce" (vs
       optional-to-enforce).

   5.  Describe the semantics of the new type including its purpose and
       example of a use case to which it applies.

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

   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 "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   | Description                         | Specification |
   +-------------+-------------------------------------+---------------+
   | IPv4CIDR    | IPv4 address block using slash      | RFCthis       |
   |             | prefix length notation (e.g.,       |               |
   |             | 192.168.0.16/28). Single IP         |               |
   |             | addresses can be expressed as /32.  |               |
   | IPv6CIDR    | IPv6 address block using slash      | RFCthis       |
   |             | prefix length notation (e.g.,       |               |
   |             | fc80::0010/124). Single IP          |               |
   |             | addresses can be expressed as /128. |               |
   | ASN         | Autonomous System (AS) Number       | RFCthis       |
   | CountryCode | ISO 3166-1 alpha-2 code             | RFCthis       |
   +-------------+-------------------------------------+---------------+

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 conform to
   the "Expert Review" policy as defined in [RFC5226].  The expert
   review should verify that new type definitions do not duplicate



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   existing type definitions and prevent gratuitous additions to the
   namespace.

   The following table defines the initial Protocol values:

   +----------+----------------+---------------------------------------+
   | Protocol | Description    | Specification                         |
   +----------+----------------+---------------------------------------+
   | HTTP     | Hypertext      | RFC2616                               |
   |          | Transfer       |                                       |
   |          | Protocol --    |                                       |
   |          | HTTP/1.1       |                                       |
   | HTTPS    | HTTP Over TLS  | RFC2818                               |
   | RTSP     | Real Time      | RFC2326                               |
   |          | Streaming      |                                       |
   |          | Protocol       |                                       |
   | RTMP     | Real-Time      | http://www.adobe.com/devnet/rtmp.html |
   |          | Messaging      |                                       |
   |          | Protocol       |                                       |
   | FTP      | FILE TRANSFER  | RFC959                                |
   |          | PROTOCOL       |                                       |
   | SFTP     | SSH File       | N/A                                   |
   |          | Transfer       |                                       |
   |          | Protocol       |                                       |
   | SCP      | Secure Copy    | N/A                                   |
   | fasp     | Aspera fast,   | N/A                                   |
   |          | adaptive,      |                                       |
   |          | secure         |                                       |
   |          | protocol       |                                       |
   +----------+----------------+---------------------------------------+

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
   Auth namespace 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:










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   +-------------+-------------------------------------+---------------+
   | Type name   | Description                         | Specification |
   +-------------+-------------------------------------+---------------+
   | credentials | Simple username and password        | RFCthis       |
   |             | 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

   The authors would like to thank David Ferguson and Francois Le
   Faucheur 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





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11.  References

11.1.  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.

11.2.  Informative References

   [I-D.ietf-cdni-framework]
              Peterson, L., Davie, B., and R. Brandenburg, "Framework
              for CDN Interconnection", draft-ietf-cdni-framework-14
              (work in progress), June 2014.

   [I-D.ietf-cdni-redirection]
              Niven-Jenkins, B. and R. Brandenburg, "Request Routing
              Redirection Interface for CDN Interconnection", draft-
              ietf-cdni-redirection-02 (work in progress), April 2014.

   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements", draft-ietf-cdni-
              requirements-17 (work in progress), January 2014.

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

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



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

Authors' Addresses

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

   Email: ben@velocix.com


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

   Email: rmurray@velocix.com


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

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


   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
   Ericsson
   43 Nagog Park
   Acton, MA  01720
   USA

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











































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