One document matched: draft-ietf-cdni-metadata-09.xml
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<rfc category="std" docName="draft-ietf-cdni-metadata-09" ipr="trust200902">
<front>
<title abbrev="CDN Interconnection Metadata">CDN Interconnection
Metadata</title>
<author fullname="Ben Niven-Jenkins" initials="B" surname="Niven-Jenkins">
<organization>Velocix (Alcatel-Lucent)</organization>
<address>
<postal>
<street>3 Ely Road</street>
<city>Milton</city>
<region>Cambridge</region>
<code>CB24 6AA</code>
<country>UK</country>
</postal>
<email>ben@velocix.com</email>
</address>
</author>
<author fullname="Rob Murray" initials="R" surname="Murray">
<organization>Velocix (Alcatel-Lucent)</organization>
<address>
<postal>
<street>3 Ely Road</street>
<city>Milton</city>
<region>Cambridge</region>
<code>CB24 6AA</code>
<country>UK</country>
</postal>
<email>rmurray@velocix.com</email>
</address>
</author>
<author fullname="Matt Caulfield" initials="M" surname="Caulfield">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>1414 Massachusetts Avenue</street>
<city>Boxborough</city>
<region>MA</region>
<code>01719</code>
<country>USA</country>
</postal>
<phone>+1 978 936 9307</phone>
<email>mcaulfie@cisco.com</email>
</address>
</author>
<author fullname="Kevin J. Ma" initials="K.J." surname="Ma">
<organization>Ericsson</organization>
<address>
<postal>
<street>43 Nagog Park</street>
<city>Acton</city>
<region>MA</region>
<code>01720</code>
<country>USA</country>
</postal>
<phone>+1 978-844-5100</phone>
<email>kevin.j.ma@ericsson.com</email>
</address>
</author>
<date/>
<abstract>
<t>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.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>Content Delivery Networks Interconnection (CDNI) (<xref
target="RFC6707"/>) enables a downstream CDN to service content requests
on behalf of an upstream CDN.</t>
<t>The CDNI Metadata interface is discussed in <xref target="RFC7336"/>
along with four other interfaces that may be used to compose a CDNI
solution (CDNI Control interface, CDNI Request Routing Redirection
interface, CDNI Footprint & Capabilities Advertisement interface and
CDNI Logging interface). <xref target="RFC7336"/> describes each
interface, and the relationships between them. The requirements for the
CDNI metadata interface are specified in <xref target="RFC7337"/>.</t>
<t>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.</t>
<t>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:</t>
<t><list style="symbols">
<t>Redirection requests received over the CDNI Request Routing
Redirection interface.</t>
<t>Content requests received directly from User Agents.</t>
</list></t>
<t>Specifically, this document specifies:</t>
<t><list style="symbols">
<t>A data structure for mapping content requests and redirection
requests to CDNI Metadata objects (<xref target="data-model"/> and
<xref target="structural-objects"/>).</t>
<t>An initial set of CDNI Generic Metadata objects (<xref
target="property-objects"/>).</t>
<t>A RESTful web service for the transfer of CDNI Metadata (<xref
target="metadata-interface"/>).</t>
</list></t>
<section anchor="terminology" title="Terminology">
<t>This document reuses the terminology defined in <xref
target="RFC6707"/>.</t>
<t>Additionally, the following terms are used throughout this document
and are defined as follows:<list style="symbols">
<t>Object - a collection of properties.</t>
<t>Property - a key and value pair where the key is a property
name and the value is the property value or an object.</t>
</list></t>
</section>
<section title="Supported Metadata Capabilities">
<t>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 <xref target="RFC7337"/>.</t>
<t>The following high-level functionality is configured via the
metadata described in <xref
target="abstract-metadata-description"/>:</t>
<t><list style="symbols">
<t>Acquisition Source: Metadata for allowing a dCDN to fetch
content from a uCDN.</t>
<t>Delivery Access Control: Metadata for restricting (or
permitting) access to content based on any of the following
factors:<list style="symbols">
<t>Location</t>
<t>Time Window</t>
<t>Delivery Protocol</t>
</list></t>
</list><list style="symbols">
<t>Delivery Authorization: Metadata for authorizing dCDN user
agent requests.</t>
<t>Cache Control: Metadata for controlling cache behavior of the
dCDN.</t>
</list></t>
<t>The metadata encoding described by this document is extensible in
order to allow for future additions to this list.</t>
<t>The set of metadata specified in this document, covering the
initial capabilities above, is only able to support CDN
interconnection for the delivery of content by a dCDN using HTTPv1.1
and for a dCDN to be able to acquire content from a uCDN using either
HTTPv1.1 or HTTPv1.1 over TLS.</t>
<t>Supporting CDN interconnection for the delivery of content using
unencrypted HTTPv2.0 (as well as for a dCDN to acquire content using
unencrypted HTTPv2.0 or HTTPv2.0 over TLS) requires the registration
of these protocol names in the CDNI Metadata Protocol Registry.</t>
<t>Supporting CDN interconnection for the delivery of content using
HTTPv1.1 over TLS or HTTPv2.0 over TLS requires specifying additional
metadata objects to carry the properties required to establish a TLS
session, for example metadata to describe the certificate to use as
part of the TLS handshake.</t>
</section>
</section>
<section title="Design Principles">
<t>The CDNI Metadata interface was designed to achieve the following
objectives:</t>
<t><list style="numbers">
<t>Cacheability of CDNI metadata objects.</t>
<t>Deterministic mapping from redirection requests and content
requests to CDNI metadata properties.</t>
<t>Support for DNS redirection as well as application-specific
redirection (for example HTTP redirection).</t>
<t>Minimal duplication of CDNI metadata.</t>
<t>Leveraging of existing protocols.</t>
</list></t>
<t>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.</t>
<t>Deterministic mappings from content to metadata properties eliminates
ambiguity and ensures that policies are applied consistently by all
downstream CDNs.</t>
<t>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.</t>
<t>Minimal duplication of CDNI metadata provides space efficiency on
storage in the CDNs, on caches in the network, and across the network
between CDNs.</t>
<t>Leveraging existing protocols avoids reinventing common mechanisms
such as data structure encoding (e.g., JSON) and data transport (e.g.,
HTTP).</t>
</section>
<section anchor="data-model" title="CDNI Metadata model">
<t>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.</t>
<t>Different Hostnames and URI paths will be associated with different
sets of CDNI Metadata properties in order to describe the required
behaviour when a dCDN surrogate is processing User Agent requests for
content at that Hostname or URI path. As a result of this structure,
significant commonality may exist between the CDNI Metadata 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.</t>
<t>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.</t>
<t><xref target="hostindex-intro"/> introduces a high level description
of the HostIndex, HostMatch, HostMetadata, PathMatch, PatternMatch and
PathMetadata objects and describes the relationships between those
objects.</t>
<t><xref target="other-objects-intro"/> 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.</t>
<t><xref target="abstract-metadata-description"/> describes in detail
the specific CDNI Metadata objects and properties which may be contained
within a CDNI GenericMetadata object.</t>
<section anchor="hostindex-intro"
title="HostIndex, HostMatch, HostMetadata, PathMatch, PatternMatch and PathMetadata objects">
<t>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.</t>
<t>The HostIndex links Hostnames (and/or IP addresses) to HostMetadata
objects via HostMatch objects. HostMetadata objects contain (or
reference) the default CDNI Metadata required to serve content for
that host. When looking up CDNI Metadata, the downstream CDN looks up
the requested Hostname (or IP address) 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.</t>
<t>HostMetadata and PathMetadata objects may also contain PathMatch
objects which in turn contain PathMetadata objects. PathMetadata
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 the PatternMatch object of that PathMatch object.</t>
<t>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.</t>
<t>The relationships between the HostIndex, HostMatch, HostMetadata,
PathMatch, PatternMatch and PathMetadata objects are described in
<xref target="metadata-model-figure-top"/>.</t>
<figure anchor="metadata-model-figure-top"
title="Relationships between CDNI Metadata Objects (Diagram Representation)">
<artwork><![CDATA[
+---------+ +---------+ +------------+
|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+-------(*)------+
+------------+
]]></artwork>
</figure>
<t>The relationships in <xref target="metadata-model-figure-top"/> are
also represented in tabular format in <xref
target="metadata-model-table"/> below.</t>
<texttable anchor="metadata-model-table"
title="Relationships between CDNI Metadata Objects (Table Representation)">
<ttcol>Data Object</ttcol>
<ttcol>Objects it contains or references</ttcol>
<c>HostIndex</c>
<c>0 or more HostMatch objects.</c>
<c>HostMatch</c>
<c>1 HostMetadata object.</c>
<c>HostMetadata</c>
<c>0 or more PathMatch objects. 0 or more GenericMetadata
objects.</c>
<c>PathMatch</c>
<c>1 PatternMatch object. 1 PathMetadata object.</c>
<c>PatternMatch</c>
<c>Does not contain or reference any other objects.</c>
<c>PathMetadata</c>
<c>0 or more PathMatch objects. 0 or more GenericMetadata
objects.</c>
</texttable>
<t>The table below describes the HostIndex, HostMatch, HostMetadata,
PathMatch, PatternMatch and PathMetadata objects in more detail.</t>
<texttable anchor="hostindex-objects-table"
title="HostIndex, HostMatch, HostMetadata, PathMatch, PatternMatch and PathMetadata CDNI Metadata Objects">
<ttcol>Data Object</ttcol>
<ttcol>Description</ttcol>
<c>HostIndex</c>
<c>A HostIndex object lists HostMatch objects</c>
<c>HostMatch</c>
<c>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.</c>
<c>HostMetadata</c>
<c>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 in turn
reference corresponding PathMetadata objects that contain the CDNI
Metadata objects for those more specific URI paths.</c>
<c>PathMatch</c>
<c>A PathMatch object defines a pattern (inside a PatternMatch
object which the 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.</c>
<c>PatternMatch</c>
<c>A PatternMatch object contains the pattern string and flags that
describe the URI path that a PathMatch applies to.</c>
<c>PathMetadata</c>
<c>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 URI 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.</c>
<c>GenericMetadata</c>
<c>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.</c>
</texttable>
<t/>
</section>
<section anchor="other-objects-intro"
title="Generic CDNI Metadata Object Properties">
<t>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.).</t>
<t>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.</t>
<t>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 might not be appropriate. Certain Metadata may be
safely, though possibly not optimally, redistributed unmodified. For
example, source acquisition address may not be optimal if
transparently redistributed, but might still work.</t>
<t>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 by the transit CDN. A CDN MUST NOT attempt to use
metadata that has been marked as "incomprehensible" by a uCDN.</t>
<t>Transit CDNs MUST NOT change the value of "mandatory-to-enforce" or
"safe-to-redistribute" when propagating metadata to a dCDN. Although a
transit CDN may set the value of "incomprehensible" to true, a transit
CDN MUST NOT change the value of "incomprehensible" from true to
false.</t>
<t>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:</t>
<texttable>
<ttcol>MtE</ttcol>
<ttcol>StR</ttcol>
<ttcol>Metadata Understood</ttcol>
<ttcol>Actions</ttcol>
<c>False</c>
<c>True</c>
<c>True</c>
<c>Can serve and redistribute.</c>
<c>False</c>
<c>True</c>
<c>False</c>
<c>Can serve and redistribute.</c>
<c>False</c>
<c>False</c>
<c>False</c>
<c>Can serve. MUST set "incomprehensible" to True when
redistributing.</c>
<c>False</c>
<c>False</c>
<c>True</c>
<c>Can serve. Can redistribute either by transforming not StR
metadata (if the CDN knows how to do so safely), otherwise MUST set
"incomprehensible" to True when redistributing.</c>
<c>True</c>
<c>True</c>
<c>True</c>
<c>Can serve and redistribute.</c>
<c>True</c>
<c>True</c>
<c>False</c>
<c>MUST NOT serve but can redistribute.</c>
<c>True</c>
<c>False</c>
<c>True</c>
<c>Can serve and redistribute.</c>
<c>True</c>
<c>False</c>
<c>False</c>
<c>MUST NOT serve. MUST set "incomprehensible" to True when
redistributing.</c>
</texttable>
<t>The following table describes the action to be taken by a dCDN for
the different "mandatory-to-enforce" (MtE) and "incomprehensible"
(Incomp) cases, when the dCDN either does or does not understand the
metadata in question:</t>
<texttable>
<ttcol>MtE</ttcol>
<ttcol>Metadata Understood</ttcol>
<ttcol>Incomp</ttcol>
<ttcol>Actions</ttcol>
<c>False</c>
<c>True</c>
<c>False</c>
<c>Can serve.</c>
<c>False</c>
<c>True</c>
<c>True</c>
<c>Can serve but MUST NOT interpret/apply any metadata marked
incomprehensible.</c>
<c>False</c>
<c>False</c>
<c>False</c>
<c>Can serve.</c>
<c>False</c>
<c>False</c>
<c>True</c>
<c>Can serve but MUST NOT interpret/apply any metadata marked
incomprehensible.</c>
<c>True</c>
<c>True</c>
<c>False</c>
<c>Can serve.</c>
<c>True</c>
<c>True</c>
<c>True</c>
<c>MUST NOT serve.</c>
<c>True</c>
<c>False</c>
<c>False</c>
<c>MUST NOT serve.</c>
<c>True</c>
<c>False</c>
<c>True</c>
<c>MUST NOT serve.</c>
</texttable>
<t/>
</section>
<section anchor="metadata-inheritance"
title="Metadata Inheritance and Override">
<t>In the Metadata 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.</t>
<t>GenericMetadata objects of a given type override all
GenericMetadata objects of the same type previously defined by any
parent object in the tree. GenericMetadata objects of a given type
previously defined by a parent object in the tree are inherited when
no object of the same type is defined by the child object. For
example, if HostMetadata for the host "example.com" contains
GenericMetadata objects of type LocationACL and TimeWindowACL, while a
PathMetadata object which applies to "example.com/movies/*" defines an
alternate GenericMetadata object of type TimeWindowACL, then: <list
style="symbols">
<t>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</t>
<t>the LocationACL defined in the HostMetadata would be inherited
for all User Agent requests for content under
"example.com/movies/".</t>
<t>A single HostMetadata or PathMetadata object SHOULD NOT contain
multiple GenericMetadata objects of the same type. If a list of
GenericMetadata contains objects of duplicate types, the receiver
MUST ignore all but the first object of each type.</t>
</list></t>
<t/>
</section>
</section>
<section anchor="abstract-metadata-description"
title="Encoding-Independent CDNI Metadata Object Descriptions">
<t><xref target="structural-objects"/> provides the definitions of each
metadata object type declared in <xref target="data-model"/>. These
metadata objects are described as structural objects as they provide the
structure for the inheritance tree and identify which specific
properties apply to a given User Agent content request.</t>
<t><xref target="property-objects"/> provides the definitions for a base
set of core metadata objects which may be contained within a
GenericMetadata object. These metadata 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 that can be dereferenced to retrieve the
complete serialized representation of the property sub-object.</t>
<t><xref target="extensibility"/> 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.</t>
<t>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, though that
may restrict the content that a given dCDN can serve. uCDNs as
generators of CDNI Metadata only need to support generating the CDNI
metadata that they need in order to express the policies and treatment
required by the content they are describing.</t>
<t>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 specified as
"Yes" by this document for an individual property or sub-object, it
means that if the property object containing that property or sub-object
is included in a metadata response, then the mandatory-to-specify
property or sub-object MUST also be included (directly or by reference)
in the response, e.g., a HostMatch property object without a host to
match against does not make sense, therefore, the host is
mandatory-to-specify inside a HostMatch property object.</t>
<section anchor="structural-objects"
title="Descriptions of the CDNI Structural Metadata Objects">
<t>Each of the sub-sections below describe the structural objects
defined in <xref target="hostindex-objects-table"/>.</t>
<section anchor="HostIndex" title="HostIndex">
<t>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 checked against the hostname (or IP
address) specified by each of the listed HostMatch objects to find
the HostMatch object which applies to the request.</t>
<t><list style="empty">
<t>Property: hosts<list style="empty">
<t>Description: List of HostMatch objects. Hosts (HostMatch
objects) MUST be evaluated in the order they appear and the
first HostMatch object that matches the content request
being processed MUST be used.</t>
<t>Type: List of HostMatch objects</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
</section>
<section anchor="HostMatch" title="HostMatch">
<t>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.</t>
<t><list style="empty">
<t>Property: host<list style="empty">
<t>Description: String (hostname or IP address) to match
against the requested host. In order for a hostname or IP
address in a content request to match the hostname or IP
address in the host property the value when converted to
lowercase in the content request MUST be identical to the
value of the host property when converted to lowercase.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: host-metadata<list style="empty">
<t>Description: CDNI Metadata to apply when delivering
content that matches this host.</t>
<t>Type: HostMetadata</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
</section>
<section anchor="HostMetadata" title="HostMetadata">
<t>A HostMetadata object contains (or references) the CDNI Metadata
properties for content served for a particular host (defined in the
HostMatch object) and possibly child PathMatch objects.</t>
<t><list style="empty">
<t>Property: metadata<list style="empty">
<t>Description: List of host related metadata.</t>
<t>Type: List of GenericMetadata objects</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: paths<list style="empty">
<t>Description: Path specific rules. Path patterns
(PathMatch objects) MUST be evaluated in the order they
appear and the first PathMatch object that matches the
content request being processed MUST be used.</t>
<t>Type: List of PathMatch objects</t>
<t>Mandatory-to-Specify: No.</t>
</list></t>
</list></t>
</section>
<section anchor="PathMatch" title="PathMatch">
<t>The PathMatch object contains (or references) an expression given
as a PatternMatch object to match against a resource URI path and
contains or references a PathMetadata object to apply if a match is
found.</t>
<t><list style="empty">
<t>Property: path-pattern<list style="empty">
<t>Description: Pattern to match against the requested path,
i.e., against the <xref target="RFC3986"/>
path-absolute.</t>
<t>Type: PatternMatch</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: path-metadata<list style="empty">
<t>Description: CDNI Metadata to apply when delivering
content that matches this path.</t>
<t>Type: PathMetadata</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
</section>
<section title="PatternMatch">
<t>A PatternMatch object contains the pattern string and flags that
describe the PathMatch expression.</t>
<t><list style="empty">
<t>Property: pattern<list style="empty">
<t>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.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: case-sensitive<list style="empty">
<t>Description: Flag indicating whether or not
case-sensitive matching should be used.</t>
<t>Type: Boolean</t>
<t>Mandatory-to-Specify: No. Default is case-insensitive
match.</t>
</list></t>
</list> <list style="empty">
<t>Property: ignore-query-string<list style="empty">
<t>Description: List of query parameters which should be
ignored when searching for a pattern match. Matching against
query parameters to ignore MUST be case-insensitive. If all
query parameters should be ignored then the list MUST be
empty.</t>
<t>Type: List of String</t>
<t>Mandatory-to-Specify: No. Default is to include query
strings when matching.</t>
</list></t>
</list></t>
</section>
<section anchor="PathMetadata" title="PathMetadata">
<t>A PathMetadata object contains (or references) the CDNI Metadata
properties for content served with the associated URI path (defined
in a PathMatch object) and possibly child PathMatch objects.</t>
<t>Note that if DNS-based redirection is employed, then a dCDN will
be unable to evaulate any metadata at the PathMetadata level or
below against the content redirection request at request routing
time because only the content request hostname is available at
request routing time. dCDNs SHOULD still process any metadata at the
PathMetadata level or below before responding to the redirection
request in order to detect if any unsupported metadata is specifed.
If any metadata is included that is not supported by the dCDN then
the dCDN SHOULD NOT redirect the the content redirection request to
itself in order to avoid receiving content requests that it is not
able to satisfy/serve.</t>
<t><list style="empty">
<t>Property: metadata<list style="empty">
<t>Description: List of path related metadata.</t>
<t>Type: List of GenericMetadata objects</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: paths<list style="empty">
<t>Description: Path specific rules. First match
applies.</t>
<t>Type: List of PathMatch objects</t>
<t>Mandatory-to-Specify: No.</t>
</list></t>
</list></t>
</section>
<section anchor="generic-metadata" title="GenericMetadata">
<t>A GenericMetadata object is an abstraction for managing
individual CDNI Metadata properties in an opaque manner.</t>
<t><list style="empty">
<t>Property: generic-metadata-type<list style="empty">
<t>Description: Case-insensitive CDNI Metadata property
object type.</t>
<t>Type: String containing a MIME Media Type</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: generic-metadata-value<list style="empty">
<t>Description: CDNI Metadata property object.</t>
<t>Type: Format/Type is defined by the value of
generic-metadata-type property above.</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: mandatory-to-enforce<list style="empty">
<t>Description: Flag identifying whether or not the
enforcement of the property Metadata is required.</t>
<t>Type: Boolean</t>
<t>Mandatory-to-Specify: No. Default is to treat metadata as
mandatory to enforce (i.e., a value of True).</t>
</list></t>
</list> <list style="empty">
<t>Property: safe-to-redistribute<list style="empty">
<t>Description: Flag identifying whether or not the property
Metadata may be safely redistributed without
modification.</t>
<t>Type: Boolean</t>
<t>Mandatory-to-Specify: No. Default is allow transparent
redistribution (i.e., a value of True).</t>
</list></t>
</list> <list style="empty">
<t>Property: incomprehensible<list style="empty">
<t>Description: Flag identifying whether or not any CDN in
the chain of delegation has failed to understand and/or
failed to properly transform this metadata object. Note:
This flag only applies to metadata objects whose
safe-to-redistribute property has a value of False.</t>
<t>Type: Boolean</t>
<t>Mandatory-to-Specify: No. Default is comprehensible
(i.e., a value of False).</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="property-objects"
title="Description of the CDNI Generic Metadata Objects">
<t>The property objects defined below are intended to be used in the
GenericMetadata object generic-metadata-value field as defined in
<xref target="generic-metadata"/> and their generic-metadata-type
property MUST be set to the appropriate Media Type as defined in <xref
target="metadata-media-types-table"/>.</t>
<section anchor="SourceMetadata" title="SourceMetadata">
<t>Source Metadata provides the dCDN information about content
acquisition, i.e., how to contact an uCDN Surrogate or an Origin
Server to obtain the content to be served. The sources are not
necessarily the actual Origin Servers operated by the CSP but might
be a set of Surrogates in the uCDN.</t>
<t/>
<t>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.</t>
<t><list style="empty">
<t>Property: sources<list style="empty">
<t>Description: Sources from which the dCDN can acquire
content, listed in order of preference.</t>
<t>Type: List of Source objects</t>
<t>Mandatory-to-Specify: No. Default is to use static
configuration, out-of-band from the metadata interface.</t>
</list></t>
</list></t>
<section anchor="Source" title="Source">
<t>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.</t>
<t><list style="empty">
<t>Property: acquisition-auth<list style="empty">
<t>Description: Authentication method to use when
requesting content from this source.</t>
<t>Type: Auth</t>
<t>Mandatory-to-Specify: No. Default is no authentication
required.</t>
</list></t>
</list> <list style="empty">
<t>Property: endpoints<list style="empty">
<t>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.</t>
<t>Type: List of EndPoint objects</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: protocol<list style="empty">
<t>Description: Network retrieval protocol to use when
requesting content from this source.</t>
<t>Type: Protocol</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="LocationACL" title="LocationACL Metadata">
<t>LocationACL Metadata defines location-based restrictions.</t>
<t>A LocationACL which does not include a locations property results
in an action of allow, meaning that delivery can be performed
regardless of the User Agent's location. The action from the first
footprint to match against the User Agent's location is the action a
CDN MUST take. If two or more footprints overlap, the first
footprint that matches against the User Agent's location determines
the action a CDN MUST take. If the locations property is included
but is empty, or if none of the listed footprints matches the User
Agent's location, then the result is an action of deny.</t>
<t>Although the LocationACL, TimeWindowACL, and ProtocolACL are
independent GenericMetadata objects, they may provide conflicting
information to a dCDN, e.g., a content request which is
simultaneously allowed based on the LocationACL and denied based on
the TimeWindowACL. The dCDN MUST use the logical AND of all ACLs
(where 'allow' is true and 'deny' is false) to determine whether or
not a request should be allowed. Thus, in the example given, the
request should be denied.</t>
<t><list style="empty">
<t>Property: locations<list style="empty">
<t>Description: Access control list which allows or denies
(blocks) delivery based on client location.</t>
<t>Type: List of LocationRule objects</t>
<t>Mandatory-to-Specify: No. Default is allow all
locations.</t>
</list></t>
</list></t>
<section anchor="LocationRule" title="LocationRule">
<t>A LocationRule contains or references a list of Footprint
objects and the corresponding action.</t>
<t><list style="empty">
<t>Property: footprints<list style="empty">
<t>Description: List of footprints to which the rule
applies.</t>
<t>Type: List of Footprint objects</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: action<list style="empty">
<t>Description: Defines whether the rule specifies
locations to allow or deny.</t>
<t>Type: Enumeration [allow|deny]</t>
<t>Mandatory-to-Specify: No. Default is deny.</t>
</list></t>
</list></t>
</section>
<section anchor="Footprint" title="Footprint">
<t>A Footprint object describes the footprint to which a
LocationRule may be applied to, e.g., an IPv4 address range or a
geographic location.</t>
<t><list style="empty">
<t>Property: footprint-type<list style="empty">
<t>Description: Registered footprint type. The footprint
types specified by this document are: IPv4CIDR (see <xref
target="IPv4CIDR"/>), IPv6CIDR (see <xref
target="IPv6CIDR"/>), Autonomous System Number (see <xref
target="ASN"/>) and Country Code (see <xref
target="CountryCode"/>).</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: footprint-value<list style="empty">
<t>Description: Footprint object conforming to the
specification associated with the registered footprint
type.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="TimeWindowACL" title="TimeWindowACL Metadata">
<t>TimeWindowACL Metadata defines time-based restrictions.</t>
<t>A TimeWindowACL which does not include a times property results
in an action of allow, meaning that delivery can be performed
regardless of the time of the User Agent's request. The action from
the first window to match against the current time is the action a
CDN MUST take. If two or more windows overlap, the first window that
matches against the current time determines the action a CDN MUST
take. If the times property is included but is empty, or if none of
the listed windows matches the current time, then the result is an
action of deny.</t>
<t>Although the LocationACL, TimeWindowACL, and ProtocolACL are
independent GenericMetadata objects, they may provide conflicting
information to a dCDN, e.g., a content request which is
simultaneously allowed based on the LocationACL and denied based on
the TimeWindowACL. The dCDN MUST use the logical AND of all ACLs
(where 'allow' is true and 'deny' is false) to determine whether or
not a request should be allowed. Thus, in the example given, the
request should be denied.</t>
<t><list style="empty">
<t>Property: times<list style="empty">
<t>Description: Description: Access control list which
allows or denies (blocks) delivery based on request
time.</t>
<t>Type: List of TimeWindowRule objects</t>
<t>Mandatory-to-Specify: No. Default is allow all time
windows.</t>
</list></t>
</list></t>
<section anchor="TimeWindowRule" title="TimeWindowRule">
<t>A TimeWindowRule contains or references a list of TimeWindow
objects and the corresponding action.</t>
<t><list style="empty">
<t>Property: windows<list style="empty">
<t>Description: List of time windows to which the rule
applies.</t>
<t>Type: List of TimeWindow objects</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: action<list style="empty">
<t>Description: Defines whether the rule specifies time
windows to allow or deny.</t>
<t>Type: Enumeration [allow|deny]</t>
<t>Mandatory-to-Specify: No. Default is deny.</t>
</list></t>
</list></t>
</section>
<section anchor="TimeWindow" title="TimeWindow">
<t>A TimeWindow object describes a time range which may be applied
by an TimeWindowACL, e.g., start 946717200 (i.e., 09:00AM
01/01/2000 UTC), end: 946746000 (i.e., 17:00AM 01/01/2000
UTC).</t>
<t><list style="empty">
<t>Property: start<list style="empty">
<t>Description: The start time of the window.</t>
<t>Type: Time</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: end<list style="empty">
<t>Description: The end time of the window.</t>
<t>Type: Time</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="ProtocolACL" title="ProtocolACL Metadata">
<t>ProtocolACL Metadata defines delivery protocol restrictions.</t>
<t>A ProtocolACL which does not include a protocol-acl property
results in an action of allow, meaning that delivery can be
performed regardless of the protocol of the User Agent's request.
The action from the first protocol to match against the request
protocol is the action a CDN MUST take. If two or more request
protocols overlap, the first protocol that matches thre request
protocol determines the action a CDN MUST take. If the protocol-acl
property is included but is empty, or if none of the listed protocol
matches the request protocol, then the result is an action of
deny.</t>
<t>Although the LocationACL, TimeWindowACL, and ProtocolACL are
independent GenericMetadata objects, they may provide conflicting
information to a dCDN, e.g., a content request which is
simultaneously allowed based on the ProtocolACL and denied based on
the TimeWindowACL. The dCDN MUST use the logical AND of all ACLs
(where 'allow' is true and 'deny' is false) to determine whether or
not a request should be allowed. Thus, in the example given, the
request should be denied.</t>
<t><list style="empty">
<t>Property: protocol-acl<list style="empty">
<t>Description: Description: Access control list which
allows or denies (blocks) delivery based on delivery
protocol.</t>
<t>Type: List of ProtocolRule objects</t>
<t>Mandatory-to-Specify: No. Default is allow all
protocols.</t>
</list></t>
</list></t>
<section anchor="ProtocolRule" title="ProtocolRule">
<t>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.</t>
<t><list style="empty">
<t>Property: protocols<list style="empty">
<t>Description: List of protocols to which the rule
applies.</t>
<t>Type: List of protocol objects</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: action<list style="empty">
<t>Description: Defines whether the rule specifies
protocols to allow or deny.</t>
<t>Type: Enumeration [allow|deny]</t>
<t>Mandatory-to-Specify: No. Default is deny.</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="DeliveryAuthorization"
title="DeliveryAuthorization Metadata">
<t>Delivery Authorization defines authorization methods for the
delivery of content to User Agents.</t>
<t><list style="empty">
<t>Property: delivery-auth-methods<list style="empty">
<t>Description: Options for authorizing content requests.
Delivery for a content request is authorized if any of the
authorization method in the list is satisfied for that
request.</t>
<t>Type: List of Auth objects</t>
<t>Mandatory-to-Specify: No. Default is no authorization
required.</t>
</list></t>
</list></t>
</section>
<section anchor="Cache" title="Cache">
<t>A Cache object describes the cache control parameters to be
applied to the content by intermediate caches.</t>
<t><list style="empty">
<t>Property: ignore-query-string<list style="empty">
<t>Description: Allows a cache to ignore URI query string
parameters while comparing URIs for equivalence. Matching
against query parameters to ignore MUST be case-insensitive.
Each query parameter to ignore is specified in the list. If
all query parameters should be ignored, then the list MUST
be specified and MUST be empty.</t>
<t>Type: List of String</t>
<t>Mandatory-to-Specify: No. Default is to consider query
string parameters when comparing URIs.</t>
</list></t>
</list></t>
</section>
<section anchor="Grouping" title="Grouping">
<t>A Grouping object identifies a large group of content to which a
given asset belongs.</t>
<t><list style="empty">
<t>Property: ccid<list style="empty">
<t>Description: Content Collection identifier for an
application-specific purpose such as logging.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: No. Default is an empty string.</t>
</list></t>
</list> <list style="empty">
<t>Property: sid<list style="empty">
<t>Description: Session identifier for an
application-specific purpose such as logging.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: No. Default is an empty string.</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="simple-data-types"
title="CDNI Metadata Simple Data Type Descriptions">
<t>This section describes the simple data types that are used for
properties of CDNI Metadata objects.</t>
<section anchor="Link" title="Link">
<t>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.</t>
<t><list style="empty">
<t>Property: href<list style="empty">
<t>Description: The URI of the addressable object being
referenced.</t>
<t>Type: URI</t>
<t>Mandatory-to-Specify: Yes</t>
</list></t>
</list> <list style="empty">
<t>Property: type<list style="empty">
<t>Description: The type of the object being referenced.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: No</t>
</list></t>
</list></t>
</section>
<section anchor="Protocol" title="Protocol">
<t>Protocol objects are used to specify registered protocols for
content acquisition or delivery (see <xref
target="ProtocolReg"/>).</t>
<t>Type: String</t>
</section>
<section title="Endpoint">
<t>A hostname (with optional port) or an IP address (with optional
port).</t>
<t>Note: All implementations MUST support IPv4 addresses encoded as
specified by the 'IPv4address' rule in Section 3.2.2 of <xref
target="RFC3986"/> and MUST support all IPv6 address formats
specified in <xref target="RFC4291"/>. Server implementations SHOULD
use IPv6 address formats specified in <xref target="RFC5952"/>.</t>
<t>Type: String</t>
</section>
<section title="URI">
<t>A URI as specified in <xref target="RFC3986"/>.</t>
<t>Type: String</t>
</section>
<section title="Time">
<t>A time value expressed in seconds since Unix epoch in the UTC
timezone.</t>
<t>Type: Integer</t>
</section>
<section anchor="Auth" title="Auth">
<t>An Auth object defines authentication and authorization methods
to be used during content acquisition and content delivery,
respectively.</t>
<t><list style="empty">
<t>Property: auth-type<list style="empty">
<t>Description: Registered Auth type (see <xref
target="CredentialAuth"/> and <xref target="AuthReg"/>).</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list> <list style="empty">
<t>Property: auth-value<list style="empty">
<t>Description: An object conforming to the specification
associated with the Registered Auth type.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
<section anchor="CredentialAuth" title="CredentialAuth Type">
<t>CredentialAuth is a Registered Auth type defining an object for
encapsulating user credentials (i.e., username and password) (see
<xref target="AuthReg"/>). The CredentialAuth object contains the
following properties:</t>
<t><list style="empty">
<t>Property: username<list style="empty">
<t>Description: Identification of user.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
<t>Property: password<list style="empty">
<t>Description: Password for user identified by username
property.</t>
<t>Type: String</t>
<t>Mandatory-to-Specify: Yes.</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="IPv4CIDR" title="IPv4CIDR">
<t>An IPv4address CIDR block encoded as specified by the
'IPv4address' rule in Section 3.2.2 of <xref target="RFC3986"/>
followed by a / followed by an unsigned integer representing the
leading bits of the routing prefix (i.e. IPv4 CIDR notation). Single
IP addresses can be expressed as /32.</t>
<t>Type: String</t>
</section>
<section anchor="IPv6CIDR" title="IPv6CIDR">
<t>An IPv6address CIDR block encoded in one of the IPv6 address
formats specified in <xref target="RFC5952"/> followed by a /
followed by an unsigned integer representing the leading bits of the
routing prefix (i.e. IPv6 CIDR notation). Single IP addresses can be
expressed as /128.</t>
<t>Type: String</t>
</section>
<section anchor="ASN" title="ASN">
<t>An Autonomous System Number encoded as a string consisting of the
characters AS (in uppercase) followed by the Autonomous System
number. For example "AS64496".</t>
<t>Type: String</t>
</section>
<section anchor="CountryCode" title="CountryCode">
<t>An ISO 3166-1 alpha-2 code <xref target="ISO3166-1"/> in
lowercase.</t>
<t>Type: String</t>
</section>
</section>
</section>
<section anchor="metadata-capabilities" title="CDNI Metadata Capabilities">
<t>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. The uCDN will likely want to avoid
delegating those requests to that dCDN. Likewise, for any metadata which
may be assigned optional values, it may be useful for the uCDN to know
which values a dCDN supports, prior to delegating any content requests
to that dCDN. If the optional value assigned to a given piece of
content's metadata is not supported by the dCDN, any delegated requests
for that content may fail, so again the uCDN is likely to want to avoid
delegating those requests to that dCDN.</t>
<t>The CDNI Footprint and Capabilities Interface (FCI) <xref
target="RFC7336"/> provides a means of advertising capabilities from
dCDN to uCDN. Support for optional metadata and support for optional
metadata values may be advertised using the FCI.</t>
</section>
<section anchor="metadata-interface" title="CDNI Metadata interface">
<t>This section specifies an interface to enable a Downstream CDN to
retrieve CDNI Metadata objects from an Upstream CDN.</t>
<t>The interface can be used by a Downstream CDN to retrieve CDNI
Metadata objects either:</t>
<t><list style="symbols">
<t>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) <xref
target="I-D.ietf-cdni-redirection"/> or in response to receiving a
request for content from a User Agent. Or;</t>
<t>In advance of being required. For example in the case of
Pre-positioned CDNI Metadata acquisition.</t>
</list></t>
<t>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 <xref
target="data-model"/> and <xref
target="abstract-metadata-description"/>).</t>
<t>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 Metadata objects it
requires.</t>
<t>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.</t>
<section title="Transport">
<t>The CDNI Metadata interface uses HTTP as the underlying protocol
transport.</t>
<t>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.</t>
<t>The corresponding HTTP Response returns the status of the operation
in the HTTP Status Code and returns the current representation of the
resource (if appropriate) in the Response Body. HTTP Responses from
servers implementing the CDNI Metadata interface that contain a
response body SHOULD include an ETag to enable validation of cached
versions of returned resources.</t>
<t>The CDNI Metadata interface specified in this document is a
read-only interface. Therefore support for other HTTP methods such as
PUT, POST and DELETE etc. is not specified. A server implementation of
the CDNI Metadata interface SHOULD reject all methods other than GET
and HEAD.</t>
<t>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.</t>
</section>
<section title="Retrieval of CDNI Metadata resources">
<t>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.</t>
<t>In order to retrieve the CDNI Metadata for a particular request the
CDNI Metadata client processes the received HostIndex object and finds
the corresponding HostMetadata entry (by matching the hostname in the
request against the hostnames listed in the HostMatch objects). If the
HostMetadata is linked (rather than embedded), the CDNI metadata
client then makes a GET request for the URI specified in the href
property of the Link object which points to the HostMetadata object
itself.</t>
<t>In order to retrieve the most specific metadata for a particular
request, the CDNI metadata client inspects the HostMetadata for
references to more specific PathMetadata objects (by matching the URI
path in the request against the path-patterns in the PathMatch). If
any PathMetadata match the request (and are linked rather than
embedded), the CDNI metadata client makes another GET request for the
PathMetadata. Each PathMetadata object may also include references to
yet more specific metadata. If this is the case, the CDNI metadata
client continues requesting PathMatch and PathMetadata objects
recursively.</t>
<t>In cases where a dCDN is not able to retrieve the entire set of
CDNI metadata associated with a User Agent request, for example
because the uCDN is uncontactable or returns an HTTP 4xx or 5xx status
in response to some or all of the dCDN's CDNI metadata requests, the
dCDN MUST NOT serve the requested content unless the dCDN has stale
versions of all the required metadata and the stale-if-error
Cache-Control extension <xref target="RFC5861"/> was included in all
previous responses that are required but cannot currently be
retrieved. The dCDN can continue to serve other content for which it
can retrieve (or for which it has fresh responses cached) all the
required metadata even if some non-applicable part of the metadata
tree is missing.</t>
<t>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.</t>
<t>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.</t>
<t>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.</t>
</section>
<section title="Bootstrapping">
<t>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.</t>
<t>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.</t>
</section>
<section title="Encoding">
<t>Objects are resources that may be:</t>
<t><list style="symbols">
<t>Addressable, where the object is a resource that may be
retrieved or referenced via its own URI.</t>
<t>Embedded, where the object is contained within a property of an
addressable object.</t>
</list></t>
<t>The descriptions of objects use the phrase "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.</t>
<section anchor="media-types" title="MIME Media Types">
<t>All MIME media types for CDNI Metadata objects are prefixed with
"application/cdni.". The MIME media 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. <xref
target="metadata-media-types-table"/> lists the MIME media type for
the metadata objects (resources) that are specified in this
document.</t>
<texttable anchor="metadata-media-types-table"
title="MIME Media Types for CDNI Metadata objects">
<ttcol>Data Object</ttcol>
<ttcol>MIME Media Type</ttcol>
<c>HostIndex</c>
<c>application/cdni.HostIndex.v1+json</c>
<c>HostMatch</c>
<c>application/cdni.HostMatch.v1+json</c>
<c>HostMetadata</c>
<c>application/cdni.HostMetadata.v1+json</c>
<c>PathMatch</c>
<c>application/cdni.PathMatch.v1+json</c>
<c>PatternMatch</c>
<c>application/cdni.PatternMatch.v1+json</c>
<c>PathMetadata</c>
<c>application/cdni.PathMetadata.v1+json</c>
<c>GenericMetadata</c>
<c>application/cdni.GenericMetadata.v1+json</c>
<c>SourceMetadata</c>
<c>application/cdni.SourceMetadata.v1+json</c>
<c>Source</c>
<c>application/cdni.Source.v1+json</c>
<c>LocationACL</c>
<c>application/cdni.LocationACL.v1+json</c>
<c>LocationRule</c>
<c>application/cdni.LocationRule.v1+json</c>
<c>Footprint</c>
<c>application/cdni.Footprint.v1+json</c>
<c>TimeWindowACL</c>
<c>application/cdni.TimeWindowACL.v1+json</c>
<c>TimeWindowRule</c>
<c>application/cdni.TimeWindowRule.v1+json</c>
<c>TimeWindow</c>
<c>application/cdni.TineWindow.v1+json</c>
<c>ProtocolACL</c>
<c>application/cdni.ProtocolACL.v1+json</c>
<c>ProtocolRule</c>
<c>application/cdni.ProtocolRule.v1+json</c>
<c>DeliveryAuthorization</c>
<c>application/ cdni.DeliveryAuthorization.v1+json</c>
<c>Cache</c>
<c>application/cdni.Cache.v1+json</c>
<c>Grouping</c>
<c>application/cdni.Grouping.v1+json</c>
<c>Auth</c>
<c>application/cdni.Auth.v1+json</c>
<c>CredentialsAuth</c>
<c>application/cdni.CredentialAuth.v1+json</c>
</texttable>
<t/>
</section>
<section title="JSON Encoding of Objects">
<t>A CDNI Metadata object 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.</t>
<t>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).</t>
<t>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.</t>
<t>In addition to the properties specified for each object type, the
keys defined below may be present in any object.</t>
<t><list style="empty">
<t>Key: base<list style="empty">
<t>Description: Provides a prefix for any relative URLs in
the object. This is similar to the XML base tag <xref
target="XML-BASE"/>. If absent, all URLs in the remainder of
the response MUST be absolute URLs.</t>
<t>Type: URI</t>
<t>Mandatory: No</t>
</list></t>
</list></t>
<t><list style="empty">
<t>Key: _links<list style="empty">
<t>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 media type of the
object being replaced.</t>
<t>Type: Dictionary object of Link objects</t>
<t>Mandatory: Yes</t>
</list></t>
</list></t>
<section title="Encoded CDNI Metadata Example">
<t>A downstream CDN may request the HostIndex and receive the
following object of type "application/cdni.HostIndex.v1+json":</t>
<figure>
<artwork><![CDATA[{
"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"
}
}
}
]
}]]></artwork>
</figure>
<t>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 media type of
"application/cdni.HostMetadata.v1+json":</t>
<figure>
<artwork><![CDATA[{
"metadata": [
{
"generic-metadata-type":
"application/cdni.SourceMetadata.v1+json",
"generic-metadata-value": {
"sources": [
{
"_links": {
"acquisition-auth": {
"auth-type": "application/cdni.Auth.v1+json",
"href": "http://metadata.ucdn.example/auth1234"
}
},
"endpoint": "acq1.ucdn.example",
"protocol": "ftp"
},
{
"_links": {
"acquisition-auth": {
"auth-type": "application/cdni.Auth.v1+json",
"href": "http://metadata.ucdn.example/auth1234"
}
},
"endpoint": "acq2.ucdn.example",
"protocol": "http"
}
]
}
},
{
"generic-metadata-type":
"application/cdni.LocationACL.v1+json",
"generic-metadata-value": {
"locations": [
{
"footprints": [
{
"footprint-type": "IPv4CIDR",
"footprint-value": "192.0.2.0/24"
}
],
"action": "deny"
}
]
}
},
{
"generic-metadata-type":
"application/cdni.ProtocolACL.v1+json",
"generic-metadata-value": {
"protocol-acl": [
{
"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"
}
}
},
{
"path-pattern": {
"pattern": "/video/movies/*"
},
"_links": {
"path-metadata": {
"type": "application/cdni.PathMetadata.v1+json",
"href": "http://metadata.ucdn.example/host1234/pathDCE"
}
}
}
]
}]]></artwork>
</figure>
<t>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":</t>
<figure>
<artwork><![CDATA[{
"metadata": [],
"paths": [
{
"path-pattern": {
"pattern": "/videos/movies/hd/*"
},
"_links": {
"pathmetadata": {
"type": "application/cdni.PathMetadata.v1+json",
"href":
"http://metadata.ucdn.example/host1234/pathABC/path123"
}
}
}
]
}]]></artwork>
</figure>
<t>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 media
type "application/cdni.PathMetadata.v1+json":</t>
<figure>
<artwork><![CDATA[{
"metadata": [
{
"generic-metadata-type":
"application/cdni.TimeWindowACL.v1+json",
"generic-metadata-value": {
"times": [
"windows": [
{
"start": "1213948800",
"end": "1327393200"
}
],
"action": "allow"
]
}
}
]
}]]></artwork>
</figure>
</section>
</section>
</section>
<section anchor="extensibility" title="Extensibility">
<t>The set of property Metadata may be extended with additional
(standards based or vendor specific) property Metadata through the
specification of new GenericMetadata objects. The GenericMetadata
object defined in <xref target="generic-metadata"/> specifies a type
field and a type-specific value field that allows any Metadata
property to be included in either the HostMetadata or PathMetadata
lists.</t>
<t>As with the initial GenericMetadata types defined in <xref
target="property-objects"/>, future GenericMetadata types MUST 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.</t>
<t>Any document which defines a new GenericMetadata type has to:</t>
<t><list style="numbers">
<t>Specify the MIME Media Type used to identify the new
GenericMetadata type being specified.</t>
<t>Define the set of properties associated with the new type.</t>
<t>For each property, define a name, description, type, and
whether or not the property is mandatory-to-specify.</t>
<t>Describe the semantics of the new type including its purpose
and example of a use case to which it applies.</t>
</list></t>
<t>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.</t>
</section>
<section title="Metadata Enforcement">
<t>At any given time, the set of GenericMetadata types supported by
the uCDN may not match the set of GenericMetadata types supported by
the dCDN.</t>
<t>In the cases where a uCDN sends Metadata containing a
GenericMetadata type that a dCDN does not support, the dCDN MUST
enforce the semantics of the "mandatory-to-enforce” property. If
a dCDN does not understand or is unable to perform the functions
associated with any "mandatory-to-enforce” Metadata, the dCDN
MUST NOT service any requests for the corresponding content.</t>
<t>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.</t>
</section>
<section title="Metadata Conflicts">
<t>It is possible that new Metadata definitions may obsolete or
conflict with 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.Auth.v2, vendor1.Auth, and vendor2.Auth)
all conflict with 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
overlap.</t>
<t>As described in <xref target="metadata-inheritance"/>, 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.</t>
<t>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.</t>
</section>
<section title="Versioning">
<t>The version of CDNI Metadata Structural objects is conveyed inside
the MIME media 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 media type containing the
version number of the object. HTTP requests sent to a metadata server
SHOULD include an Accept header with the MIME media type (which
includes the version) of the expected object. Metadata clients can
specify multiple MIME media 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 media 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".</t>
<t>GenericMetadata objects include a "type" property which specifies
the MIME media type of the GenericMetadata value. This MIME media 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".</t>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This document requests the registration of the following MIME Media
Type under the IANA MIME Media Type registry
(http://www.iana.org/assignments/media-types/index.html).<list
style="empty">
<t>application/cdni.HostIndex.v1+json</t>
<t>application/cdni.HostMatch.v1+json</t>
<t>application/cdni.HostMetadata.v1+json</t>
<t>application/cdni.PathMatch.v1+json</t>
<t>application/cdni.PatternMatch.v1+json</t>
<t>application/cdni.PathMetadata.v1+json</t>
<t>application/cdni.GenericMetadata.v1+json</t>
<t>application/cdni.SourceMetadata.v1+json</t>
<t>application/cdni.Source.v1+json</t>
<t>application/cdni.LocationACL.v1+json</t>
<t>application/cdni.LocationRule.v1+json</t>
<t>application/cdni.Footprint.v1+json</t>
<t>application/cdni.TimeWindowACL.v1+json</t>
<t>application/cdni.TimeWindowRule.v1+json</t>
<t>application/cdni.TimeWindow.v1+json</t>
<t>application/cdni.ProtocolACL.v1+json</t>
<t>application/cdni.ProtocolRule.v1+json</t>
<t>application/cdni.DeliveryAuthorization.v1+json</t>
<t>application/cdni.Cache.v1+json</t>
<t>application/cdni.Grouping.v1+json</t>
<t>application/cdni.Auth.v1+json</t>
<t>application/cdni.CredentialsAuth.v1+json</t>
</list></t>
<section anchor="FootprintReg"
title="CDNI Metadata Footprint Types Registry">
<t>The IANA is requested to create a new "CDNI Metadata Footprint
Types" registry. The "CDNI Metadata Footprint Types" namespace defines
the valid Footprint object type values used by the Footprint object in
<xref target="Footprint"/>. Additions to the Footprint type namespace
conform to the "Expert Review" policy as defined in <xref
target="RFC5226"/>. The expert reviewer should verify that new type
definitions do not duplicate existing type definitions and prevent
gratuitous additions to the namespace.</t>
<t>The following table defines the initial Footprint Registry
values:</t>
<texttable>
<ttcol align="left">Footprint Type</ttcol>
<ttcol align="left">Description</ttcol>
<ttcol align="left">Specification</ttcol>
<c>IPv4CIDR</c>
<c>IPv4 CIDR address block</c>
<c>RFCthis</c>
<c>IPv6CIDR</c>
<c>IPv6 CIDR address block</c>
<c>RFCthis</c>
<c>ASN</c>
<c>Autonomous System (AS) Number</c>
<c>RFCthis</c>
<c>CountryCode</c>
<c>ISO 3166-1 alpha-2 code</c>
<c>RFCthis</c>
</texttable>
</section>
<section anchor="ProtocolReg"
title="CDNI Metadata Protocol Types Registry">
<t>The IANA is requested to create a new "CDNI Metadata Protocol
Types" registry. The "CDNI Metadata Protocol Types" namespace defines
the valid Protocol object values in <xref target="Protocol"/>, used by
the SourceMetadata and ProtocolACL objects. Additions to the Protocol
namespace conform to the "Expert Review" policy as defined in <xref
target="RFC5226"/>. The expert review should verify that new protocol
definitions do not duplicate existing protocol definitions and prevent
gratuitous additions to the namespace.</t>
<t>The following table defines the initial Protocol values:</t>
<texttable>
<ttcol align="left">Protocol Type</ttcol>
<ttcol align="left">Description</ttcol>
<ttcol align="left">Specification</ttcol>
<c>HTTP1.1</c>
<c>Hypertext Transfer Protocol -- HTTP/1.1</c>
<c>RFC7230</c>
<c>HTTPS1.1</c>
<c>HTTP/1.1 Over TLS</c>
<c>RFC2818</c>
</texttable>
</section>
<section anchor="AuthReg" title="CDNI Metadata Auth Types Registry">
<t>The IANA is requested to create a new "CDNI Metadata Auth Types"
registry. The "CDNI Metadata Auth Type" namespace defines the valid
Auth object types used by the Auth object in <xref target="Auth"/>.
Additions to the Auth Type namespace conform to the "Expert Review"
policy as defined in <xref target="RFC5226"/>. The expert review
should verify that new type definitions do not duplicate existing type
definitions and prevent gratuitous additions to the namespace.</t>
<t>The following table defines the initial Auth type values:</t>
<texttable>
<ttcol align="left">Auth Type</ttcol>
<ttcol align="left">Description</ttcol>
<ttcol align="left">Specification</ttcol>
<c>CredentialAuth</c>
<c>Simple username and password authentication.</c>
<c>RFCthis</c>
</texttable>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t/>
<section anchor="SecurityAuthentication" title="Authentication">
<t>Unauthorized access to metadata could result in denial of service.
A malicious metadata server, proxy server or an attacker performing a
"man in the middle" attack" could provide metadata to a dCDN that
denies service for one or more pieces of content to one or more user
agents. A malicious metadata server (or an attacker performing a "Man
in the middle" attack") could modify metadata so that dCDNs are
directed to contact to malicious origin servers instead of the actual
origin servers. A malicious metadata client could continuously issue
large metadata requests to overload a uCDN's metadata server(s).</t>
<t>Unauthorized access to metadata could result in denial of service.
A malicious metadata server, proxy server or an attacker performing a
"man in the middle" attack could provide metadata to a dCDN that
either:</t>
<t><list style="symbols">
<t>Denies service for one or more pieces of content to one or more
User Agents; or</t>
<t>Directs dCDNs to contact malicious origin servers instead of
the actual origin servers.</t>
</list></t>
<t>Unauthorized access to metadata could also enable a malicious
metadata client to continuously issue large metadata requests in order
to overload a uCDN's metadata server(s).</t>
<t>Unauthorized access to metadata could result in leakage of private
information. A malicious metadata client could request metadata in
order to gain access to origin servers, as well as information
pertaining to content restrictions.</t>
<t>An implementation of the CDNI Metadata interface SHOULD use mutual
authentication to prevent unauthorized access to metadata.</t>
</section>
<section anchor="SecurityConfidentiality" title="Confidentiality">
<t>Unauthorized viewing of metadata could result in leakage of private
information. A third party could intercept metadata transactions in
order to gain access to origin servers, as well as information
pertaining to content restrictions.</t>
<t>An implementation of the CDNI Metadata interface SHOULD use strong
encryption to prevent unauthorized viewing of metadata.</t>
</section>
<section anchor="SecurityIntegrity" title="Integrity">
<t>Unauthorized modification of metadata could result in denial of
service. A malicious metadata server, proxy server or an attacker
performing a "man in the middle" attack" could modify metadata
destined to a dCDN in order to deny service for one or more pieces of
content to one or more user agents. A malicious metadata server, proxy
server or an attacker performing a "Man in the middle" attack" could
modify metadata so that dCDNs are directed to contact to malicious
origin servers instead of the actual origin servers.</t>
<t>An implementation of the CDNI Metadata interface SHOULD use strong
encryption and mutual authentication to prevent unauthorized
modification of metadata.</t>
</section>
<section anchor="SecurityPrivacy" title="Privacy">
<t>Content provider origin and policy information is conveyed through
the CDNI Metadata interface. The distribution of this information to
another CDN may introduce potential privacy concerns for some content
providers, for example because dCDNs accepting content requests for a
content provider's content may be able to obtain additional
information & usage patterns relating to the users of a content
provider's services. Content providers with such concerns can instruct
their CDN partners not to use CDN interconnects when delivering that
content provider's content.</t>
</section>
<section title="Securing the CDNI Metadata interface">
<t>An implementation of the CDNI Metadata interface MUST support TLS
transport as per <xref target="RFC2818"/> and <xref
target="RFC7230"/>. The use of TLS for transport of the CDNI Metadata
interface messages allows:</t>
<t><list style="symbols">
<t>The dCDN and uCDN to authenticate each other (to ensure they
are transmitting/receiving CDNI Metadata requests & responses
from an authenticated CDN).</t>
<t>CDNI Metadata interface requests and responses to be
transmitted with confidentiality.</t>
<t>The integrity of the CDNI Metadata interface requests and
responses to be protected during the exchange.</t>
</list></t>
<t>In an environment where any such protection is required, TLS SHOULD
be used (including authentication of the remote end) by the
server-side (uCDN) and the client-side (dCDN) of the CDNI Metadata
interface unless alternate methods are used for ensuring the
confidentiality of the information in the CDNI Metadata interface
requests and responses (such as setting up an IPsec tunnel between the
two CDNs or using a physically secured internal network between two
CDNs that are owned by the same corporate entity).</t>
<t>An implementation of the CDNI Metadata interface MUST support the
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 cipher suite (<xref
target="RFC5288"/>). An implementation of the CDNI Metadata interface
SHOULD prefer cipher suites which support perfect forward secrecy over
cipher suites that don't.</t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors would like to thank David Ferguson and Francois Le
Faucheur for their valuable comments and input to this document.</t>
</section>
<section title="Contributing Authors">
<t>[RFC Editor Note: Please move the contents of this section to the
Authors' Addresses section prior to publication as an RFC.]</t>
<figure>
<artwork><![CDATA[Grant Watson
Velocix (Alcatel-Lucent)
3 Ely Road
Milton, Cambridge CB24 6AA
UK
Email: gwatson@velocix.com
Kent Leung
Cisco Systems
3625 Cisco Way
San Jose, 95134
USA
Email: kleung@cisco.com
]]></artwork>
</figure>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119" ?>
<?rfc include="reference.RFC.5226" ?>
<?rfc include="reference.RFC.4291" ?>
<?rfc include="reference.RFC.5952" ?>
<?rfc include="reference.RFC.5288"?>
<?rfc include="reference.RFC.5861"?>
<reference anchor="ISO3166-1">
<front>
<title>https://www.iso.org/obp/ui/#search</title>
<author>
<organization/>
</author>
<date/>
</front>
</reference>
<?rfc ?>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.7337"?>
<?rfc include="reference.RFC.7336"?>
<?rfc include="reference.RFC.6707" ?>
<?rfc include="reference.RFC.3986" ?>
<?rfc include="reference.RFC.2818" ?>
<?rfc include="reference.RFC.7230" ?>
<?rfc include="reference.I-D.ietf-cdni-redirection"?>
<reference anchor="XML-BASE">
<front>
<title>XML Base (Second Edition) -
http://www.w3.org/TR/xmlbase/</title>
<author fullname="Jonathan" initials="J" role="editor"
surname="Marsh">
<organization/>
</author>
<author fullname="Richard" initials="R" role="editor"
surname="Tobin">
<organization/>
<address>
<postal>
<street/>
<city/>
<region/>
<code/>
<country/>
</postal>
<phone/>
<facsimile/>
<email/>
<uri/>
</address>
</author>
<date day="28" month="January" year="2009"/>
</front>
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-24 01:09:09 |