Network Working Group B. Niven-Jenkins
Internet-Draft R. Murray
Intended status: Standards Track G. Watson
Expires: August 18, 2014 Velocix (Alcatel-Lucent)
M. Caulfield
K. Leung
Cisco Systems
K. Ma
Azuki Systems, Inc.
February 14, 2014
CDN Interconnect Metadata
draft-ietf-cdni-metadata-06
Abstract
The CDNI Metadata Interface enables interconnected CDNs to exchange
content distribution metadata in order to enable content acquisition
and delivery. The CDNI metadata associated with a piece of content
provides a downstream CDN with sufficient information for the
downstream CDN to service content requests on behalf of an upstream
CDN. This document describes both the core set of CDNI metadata and
the protocol for exchanging that metadata.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 18, 2014.
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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
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Design Principles . . . . . . . . . . . . . . . . . . . . . . 4
3. CDNI Metadata Data Model . . . . . . . . . . . . . . . . . . 5
3.1. HostIndex, HostMetadata & PathMetadata objects . . . . . 6
3.2. Generic CDNI Metadata Object Properties . . . . . . . . . 9
3.3. Metadata Inheritance and Override . . . . . . . . . . . . 10
3.4. Metadata Naming . . . . . . . . . . . . . . . . . . . . . 11
4. Encoding-Independent CDNI Metadata Object Descriptions . . . 11
4.1. CDNI Metadata Structural Object Descriptions . . . . . . 11
4.1.1. HostIndex . . . . . . . . . . . . . . . . . . . . . . 12
4.1.2. HostMatch . . . . . . . . . . . . . . . . . . . . . . 12
4.1.3. HostMetadata . . . . . . . . . . . . . . . . . . . . 12
4.1.4. PathMatch . . . . . . . . . . . . . . . . . . . . . . 13
4.1.5. PathMetadata . . . . . . . . . . . . . . . . . . . . 13
4.1.6. PatternMatch . . . . . . . . . . . . . . . . . . . . 14
4.1.7. GenericMetadata . . . . . . . . . . . . . . . . . . . 15
4.2. CDNI Metadata Property Object Descriptions . . . . . . . 16
4.2.1. Source Metadata . . . . . . . . . . . . . . . . . . . 16
4.2.1.1. Source . . . . . . . . . . . . . . . . . . . . . 16
4.2.2. LocationACL Metadata . . . . . . . . . . . . . . . . 17
4.2.2.1. LocationRule . . . . . . . . . . . . . . . . . . 17
4.2.2.2. Footprint . . . . . . . . . . . . . . . . . . . . 18
4.2.3. TimeWindowACL Metadata . . . . . . . . . . . . . . . 18
4.2.3.1. TimeWindowRule . . . . . . . . . . . . . . . . . 18
4.2.3.2. TimeWindow . . . . . . . . . . . . . . . . . . . 19
4.2.4. ProtocolACL Metadata . . . . . . . . . . . . . . . . 19
4.2.4.1. ProtocolRule . . . . . . . . . . . . . . . . . . 20
4.2.5. Authorization Metadata . . . . . . . . . . . . . . . 20
4.2.6. Auth . . . . . . . . . . . . . . . . . . . . . . . . 21
4.2.6.1. Credentials Auth Type . . . . . . . . . . . . . . 21
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4.2.7. Cache . . . . . . . . . . . . . . . . . . . . . . . . 22
4.2.8. Grouping . . . . . . . . . . . . . . . . . . . . . . 22
4.3. CDNI Metadata Simple Data Type Descriptions . . . . . . . 22
4.3.1. Link . . . . . . . . . . . . . . . . . . . . . . . . 23
4.3.2. Protocol . . . . . . . . . . . . . . . . . . . . . . 23
4.3.3. Endpoint . . . . . . . . . . . . . . . . . . . . . . 23
4.3.4. URI . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.3.5. Time . . . . . . . . . . . . . . . . . . . . . . . . 24
5. CDNI Metadata Capabilities . . . . . . . . . . . . . . . . . 24
5.1. Protocol ACL Capabilities . . . . . . . . . . . . . . . . 24
5.2. Authorization Metadata Capabilities . . . . . . . . . . . 25
6. CDNI Metadata interface . . . . . . . . . . . . . . . . . . . 25
6.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 26
6.2. Retrieval of CDNI Metadata resources . . . . . . . . . . 26
6.3. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 27
6.4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . 27
6.4.1. MIME Media Types . . . . . . . . . . . . . . . . . . 28
6.4.2. JSON Encoding of Objects . . . . . . . . . . . . . . 28
6.4.2.1. JSON Example . . . . . . . . . . . . . . . . . . 29
6.5. Extensibility . . . . . . . . . . . . . . . . . . . . . . 33
6.5.1. Metadata Enforcement . . . . . . . . . . . . . . . . 33
6.5.2. Metadata Override . . . . . . . . . . . . . . . . . . 34
6.6. Versioning . . . . . . . . . . . . . . . . . . . . . . . 34
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
7.1. GenericMetadata Type Registry . . . . . . . . . . . . . . 35
7.1.1. GenericMetadata Sub-Registries . . . . . . . . . . . 36
7.1.1.1. Footprint Sub-Registry . . . . . . . . . . . . . 36
7.1.1.2. Protocol Sub-Registry . . . . . . . . . . . . . . 37
7.1.1.3. Authentication Sub-Registry . . . . . . . . . . . 38
8. Security Considerations . . . . . . . . . . . . . . . . . . . 39
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 39
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 39
10.1. Normative References . . . . . . . . . . . . . . . . . . 39
10.2. Informative References . . . . . . . . . . . . . . . . . 40
Appendix A. Relationship to the CDNI Requirements . . . . . . . 40
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction
CDNI enables a downstream CDN to service content requests on behalf
of an upstream CDN. The CDNI metadata associated with a piece of
content (or with a set of contents) provides a downstream CDN with
sufficient information for servicing content requests on behalf of an
upstream CDN in accordance with the policies defined by the upstream
CDN.
The CDNI Metadata Interface is introduced by [RFC6707] along with
three other interfaces that may be used to compose a CDNI solution
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(Control, Request Routing and Logging). [I-D.ietf-cdni-framework]
expands on the information provided in [RFC6707] and describes each
interface, and the relationships between them, in more detail. The
requirements for the CDNI metadata interface are specified in
[I-D.ietf-cdni-requirements].
This document focuses on the CDNI Metadata interface which enables a
downstream CDN to obtain CDNI Metadata from an upstream CDN so that
the downstream CDN can properly process and respond to:
o Redirection Requests received over the CDNI Request Routing
protocol.
o Content Requests received directly from User Agents.
Specifically, this document proposes:
o A data structure for mapping content requests to CDNI Metadata
properties (Section 3).
o An initial set of CDNI Metadata properties (Section 4.2).
o A RESTful web service for the transfer of CDNI Metadata
(Section 6).
1.1. Terminology
This document reuses the terminology defined in [RFC6707].
Additionally, the following terms are used throughout this document
and are defined as follows:
o Object - a collection of properties
o Property - a key and value pair where the key is a property name
and the value is the property value or an object.
2. Design Principles
The proposed CDNI Metadata Interface was designed to achieve the
following objectives:
1. Cacheability of CDNI metadata objects
2. Deterministic mapping from redirection and content requests to
CDNI metadata properties
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3. Support for DNS redirection as well as application-specific
redirection (for example HTTP redirection)
4. Minimal duplication of CDNI metadata
5. Leverage existing protocols
Cacheability improves the latency of acquiring metadata while
maintaining its freshness and therefore improves the latency of
serving content requests. The CDNI Metadata Interface uses HTTP to
achieve cacheability.
Deterministic mappings from content to metadata properties eliminates
ambiguity and ensures that policies are applied consistently by all
downstream CDNs.
Support for both HTTP and DNS redirection ensures that the CDNI
Metadata Interface can be used for HTTP and DNS redirection and also
meets the same design principles for both HTTP and DNS based
redirection schemes.
Minimal duplication of CDNI metadata provides space efficiency on
storage in the CDNs, on caches in the network, and across the network
between CDNs.
Leveraging existing protocols avoids reinventing common mechanisms
such as data structure encoding (e.g. XML, JSON) and data transport
(e.g. HTTP).
3. CDNI Metadata Data Model
The CDNI Metadata Model describes a data structure for mapping
redirection requests and content requests to metadata properties.
Metadata properties describe how to acquire 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
content at that Hostname or URI path. As a result of this structure,
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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 by a dCDN once, even if it is referenced by the CDNI
Metadata of multiple Hostnames.
Section 3.1 introduces a high level description of the HostIndex,
HostMetadata and PathMetadata objects and describes the relationships
between those objects.
Section 3.2 introduces a high level description of the CDNI
GenericMetadata object which represents the level at which CDNI
Metadata override occurs between HostMetadata and PathMetadata
objects.
Section 4 describes in detail the specific CDNI Metadata objects and
properties which may be contained within a CDNI GenericMetadata
object.
3.1. HostIndex, HostMetadata & PathMetadata objects
A HostIndex object contains a list of Hostnames (and/or IP addresses)
for which content requests may be delegated to the downstream CDN.
The HostIndex is the starting point for accessing the uCDN's CDNI
Metadata data store. It enables surrogates in the dCDN to
deterministically discover, on receipt of a User Agent request for
content, which other CDNI Metadata objects it requires in order to
deliver the requested content.
The HostIndex links Hostnames (and/or IP addresses) to HostMetadata
objects via HostMatch objects. HostMetadata objects contain (or
reference) the default CDNI Metadata required to serve content for
that host. When looking up CDNI Metadata, the downstream CDN looks
up the requested Hostname (or IP address) in the HostIndex, from
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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.
Besides containing the default CDNI Metadata for the specified
Hostname, HostMetadata and PathMetadata objects may also contain
PathMatch objects which in turn contain PathMetadata objects.
PathMatch objects override the CDNI Metadata in the HostMetadata
object or one or more preceding PathMetadata objects with more
specific CDNI Metadata that applies to content requests matching the
pattern defined in that PathMatch object.
For the purposes of retrieving CDNI Metadata all other required CDNI
Metadata objects and their properties are discoverable from the
appropriate HostMetadata, PathMatch and PathMetadata objects for the
requested content.
The relationships between the HostIndex, HostMatch, HostMetadata,
PathMatch and PathMetadata objects are described in Figure 1.
+---------+ +---------+ +------------+
|HostIndex+-(*)->|HostMatch|-(1)->|HostMetadata+-------(*)------+
+---------+ +---------+ +------+-----+ |
| |
(*) |
| |
--> References V V
(1) One and only one +---------+ **************************
(*) Zero or more +--->|PathMatch| *Generic Metadata Objects*
| +---------+ **************************
| | ^
(*) (1) |
| | |
| V |
| +------------+ |
+--|PathMetadata+-------(*)------+
+------------+
Figure 1: Relationships between the HostIndex, HostMetadata &
PathMetadata CDNI Metadata Objects
The relationships in Figure 1 are summarised in Table 1 below.
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+--------------+----------------------------------------------------+
| Data Object | Objects it References |
+--------------+----------------------------------------------------+
| HostIndex | 0 or more HostMatch objects. |
| HostMatch | 1 HostMetadata object. |
| HostMetadata | 0 or more PathMatch objects. 0 or more |
| | GenericMetadata objects. |
| PathMatch | 1 PathMetadata object. |
| PathMetadata | 0 or more PathMatch objects. 0 or more |
| | GenericMetadata objects. |
+--------------+----------------------------------------------------+
Table 1: Relationships between CDNI Metadata Objects
The table below describes the HostIndex, HostMetadata and
PathMetadata objects in more detail.
+-----------------+-------------------------------------------------+
| Data Object | Description |
+-----------------+-------------------------------------------------+
| HostIndex | A HostIndex object lists HostMatch objects |
| HostMatch | A HostMatch object defines a hostname to match |
| | against a requested host, and contains or |
| | references a HostMetadata object which contains |
| | CDNI Metadata objects to be applied when a |
| | request matches against the hostname. For |
| | example, if "example.com" is a content |
| | provider, a HostMatch object may include an |
| | entry for "example.com" with the URI of the |
| | associated HostMetadata object. |
| HostMetadata | A HostMetadata object contains (or references) |
| | the default CDNI Metadata objects for content |
| | served from that host, i.e. the CDNI Metadata |
| | objects for content requests that do not match |
| | any of the PathMatch objects contained or |
| | referenced by that HostMetadata object. For |
| | example, a HostMetadata object may describe the |
| | metadata properties which apply to |
| | "example.com" and may contain PathMatches for |
| | "example.com/movies/*" and |
| | "example.com/music/*" which reference |
| | corresponding PathMetadata objects that contain |
| | the CDNI Metadata objects for those more |
| | specific URI paths. |
| PathMatch | A PathMatch object defines a pattern to match |
| | against the requested URI path, and contains or |
| | references a PathMetadata object which contains |
| | (or references) the CDNI Metadata objects to be |
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| | applied when a content request matches against |
| | the defined URI path pattern. For example, a |
| | PathMatch object may include a pattern for the |
| | path "/movies/*" and may reference a |
| | PathMetadata object which contains the CDNI |
| | Metadata for content with that path. |
| PathMetadata | A PathMetadata object contains the CDNI |
| | GenericMetadata objects for content served with |
| | the associated URI path (defined in a PathMatch |
| | object). A PathMetadata object may also contain |
| | PathMatch objects in order to recursively |
| | define more specific URI paths that require |
| | different (e.g. more specific) CDNI Metadata to |
| | this one. For example, the PathMetadata object |
| | which applies to "example.com/movies/*" may |
| | describe CDNI Metadata which apply to that |
| | resource path and may contain a PathMatch |
| | object for "example.com/movies/hd/*" which |
| | would reference the corresponding PathMetadata |
| | object for the "example.com/movies/hd/" path |
| | prefix. |
| GenericMetadata | A GenericMetadata object contains individual |
| | CDNI Metadata objects which define the specific |
| | policies and attributes needed to properly |
| | deliver the associated content. For example, a |
| | GenericMetadata object may describe the source |
| | from which a CDN may acquire a piece of |
| | content. |
+-----------------+-------------------------------------------------+
Table 2: HostIndex, HostMetadata and PathMetadata CDNI Metadata
Objects
3.2. Generic CDNI Metadata Object Properties
The HostMetadata and PathMetadata objects contain or can reference
other CDNI Metadata objects that contain properties which describe
how User Agent requests for content should be processed, for example
where to acquire the content, authorization rules that should be
applied, delivery location restrictions and so on. Each such CDNI
Metadata object is a specialization of a CDNI GenericMetadata object.
The GenericMetadata object abstracts the basic information required
for Metadata override and 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
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enforce. If the dCDN does not understand or support the property
type and the property type is mandatory to enforce, the dCDN MUST NOT
serve the content to the User Agent. If the dCDN does not understand
or support the property type it is also not going to be able to
properly propagate the Metadata for cascaded distribution. If the
dCDN does not understand or support the property type and the
property type is not mandatory to enforce, then the GenericMetadata
object may be safely ignored.
Although a CDN cannot serve content to a User Agent if a mandatory
property cannot be enforced, it may be safe to redistribute that
metadata to another CDN without modification. For example, in the
cascaded CDN case, a transit CDN may pass through mandatory-to-
enforce metadata to the delivery CDN. For Metadata which does not
require customization, the data representation received off the wire
MAY be stored and redistributed without being natively understood or
supported by the transit CDN. However, for Metadata which require
translations, transparent redistribution of the uCDN Metadata values
may not be appropriate. Certain Metadata may be safely, though
possibly not optimially, redistributed unmodified, e.g., source
acquisition address may not be optimal if transparently
redistributed, but may still work. Redistribution safety MUST be
specified for each GenericMetadata.
3.3. Metadata Inheritance and Override
In the data model, a HostMetadata object may contain (or reference)
multiple PathMetadata objects (via PathMatch objects). Each
PathMetadata object may in turn contain (or reference) other
PathMetadata objects. HostMetadata and PathMetadata objects form an
inheritance tree where each node in the tree inherits or overrides
the property values set by its parent.
GenericMetadata objects of a given type override all GenericMetadata
objects of the same type previously defined by any parent object in
the tree. GenericMetadata objects of a given type previously defined
by a parent object in the tree are inherited when no object of the
same type is defined by the child object. For example, if
HostMetadata for the host "example.com" contains GenericMetadata
objects of type LocationACL and TimeWindowACL, while a PathMetadata
object which applies to "example.com/movies/*" defines an alternate
GenericMetadata object of type TimeWindowACL, then:
the TimeWindowACL defined in the PathMetadata would override the
TimeWindowACL defined in the HostMetadata
the LocationACL defined in the HostMetadata would be inherited for
all User Agent requests for content under "example.com/movies".
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The PathMetadata defined TimeWindowACL would override the
TimeWindowACL defined in the HostMetadata for all User Agent requests
for movies.
3.4. Metadata Naming
GenericMetadata objects are identified by their type. The type
SHOULD be descriptive, and MAY be hierarchical to support aggregating
groups of properties for the purpose of readability and for avoiding
name conflicts between vendor extensions. A dotted alpha-numeric
notation is suggested for human readability.
Metadata types defined by this document are not hierarchical.
4. Encoding-Independent CDNI Metadata Object Descriptions
Section 4.1 provides the definitions of each object type declared in
Section 3. These objects are described as structural objects as they
provide the structure for the inheritance tree and identifying which
specific properties apply to a given User Agent content request.
Section 4.2 provides the definitions for the set of core metadata
objects which may be contained within a GenericMetadata object.
These objects are described as property objects as they define the
semantics, enforcement options, and serialization rules for specific
properties. These properties govern how User Agent requests for
content are handled. Property objects may be composed of or contain
references to other objects. In those cases the value of the
property can be either an object of that type (the object is
embedded) or a Link object that contains a URI and relationship that
can be dereferenced to retrieve the CDNI Metadata object that
represents the value of that property.
Note: In the following sections, the term "mandatory-to-specify" is
used to convey which objects or properties must be specified for a
given parent object or property. When mandatory-to-specify is set to
true, it implies that if the parent object is specified, then the
defined object or property MUST also be specified, e.g., a HostMatch
object without a host to match against does not make sense,
therefore, the host is mandatory-to-specify inside a parent HostMatch
object.
4.1. CDNI Metadata Structural Object Descriptions
Each of the sub-sections below describe the structural objects
defined in Table 2.
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4.1.1. HostIndex
The HostIndex object is the entry point into the CDNI Metadata
hierarchy. It contains a list of HostMatch objects. An incoming
content request is matched against the hostname inside of each of the
listed HostMatch objects to find the HostMatch object which applies
to the request.
Property: hosts
Description: List of HostMatch objects, in priority order.
Type: List of HostMatch objects
Mandatory-to-Specify: Yes.
4.1.2. HostMatch
The HostMatch object contains a hostname or IP address to match
against content requests. The HostMatch object also contains a
reference to Metadata objects to apply if a match is found.
Property: host
Description: String (hostname or IP address) to match against
the requested host.
Type: String
Mandatory-to-Specify: Yes.
Property: host-metadata
Description: CDNI Metadata to apply when delivering content
that matches this host.
Type: HostMetadata
Mandatory-to-Specify: Yes.
4.1.3. HostMetadata
The HostMetadata object contains both Metadata that applies to
content requests for a particular host and a list of pattern matches
for finding more specific Metadata based on the resource path in a
content request.
Property: metadata
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Description: List of host related metadata.
Type: List of GenericMetadata objects
Mandatory-to-Specify: Yes.
Property: paths
Description: Path specific rules. First match applies.
Type: List of PathMatch objects
Mandatory-to-Specify: No.
4.1.4. PathMatch
The PathMatch object contains an expression given as a PatternMatch
object to match against a resource URI path and Metadata objects to
apply if a match is found.
Property: path-pattern
Description: Pattern to match against the requested path, i.e.
against the [RFC3986] path-absolute.
Type: PatternMatch
Mandatory-to-Specify: Yes.
Property: path-metadata
Description: CDNI Metadata to apply when delivering content
that matches this pattern.
Type: PathMetadata
Mandatory-to-Specify: Yes.
4.1.5. PathMetadata
A PathMetadata object contains the CDNI Metadata properties for
content served with the associated URI path (defined in a PathMatch
object). Note that if CDNI metadata is used as an input to CDNI
request routing and DNS-based redirection is employed, then any
metadata at the PathMetadata level or below will be inaccessible at
request routing time.
Property: metadata
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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.
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
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Mandatory-to-Specify: No. Default is to include query strings
when matching.
4.1.7. GenericMetadata
A GenericMetadata object is a abstraction for managing individual
CDNI Metadata properties in an opaque manner.
Property: type
Description: CDNI Metadata property object type.
Type: String
Mandatory-to-Specify: Yes.
Property: value
Description: CDNI Metadata property object.
Type: matches the type property above
Mandatory-to-Specify: Yes.
Property: mandatory-to-enforce
Description: Flag identifying whether or not the enforcement of
the property Metadata is required.
Type: Boolean
Mandatory-to-Specify: 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.
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4.2. CDNI Metadata Property Object Descriptions
The property objects defined below are intended to be used in the
GenericMetadata object value field as defined in Section 4.1.7. All
of the objects defined below are considered both mandatory to enforce
and safe to redistribute.
4.2.1. Source Metadata
Source Metadata provides the dCDN information about content
acquisition e.g. how to contact an uCDN Surrogate or an Origin Server
to obtain the content to be served. The sources are not necessarily
the actual Origin Servers operated by the CSP but might be a set of
Surrogates in the uCDN.
Property: sources
Description: Sources from which the dCDN can acquire content,
listed in priority order.
Type: List of Source objects
Mandatory-to-Specify: No. Default is to use static
configuration, out of band of the metadata interface.
4.2.1.1. Source
A Source object describes the Source which should be used by the dCDN
for content acquisition, e.g. a Surrogate within the uCDN or an
alternate Origin Server, the protocol to be used and any
authentication method.
Property: auth
Description: Authentication method to use when requesting
content from this source.
Type: Auth
Mandatory-to-Specify: No. Default is no authentication is
required.
Property: endpoints
Description: Origins from which the dCDN can acquire content.
Type: List of EndPoint objects
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Mandatory-to-Specify: Yes.
Property: protocol
Description: Network retrieval protocol to use when requesting
content from this source.
Type: Protocol
Mandatory-to-Specify: Yes.
4.2.2. LocationACL Metadata
LocationACL Metadata defines location-based restrictions.
Property: locations
Description: Access control list which applies restrictions to
delivery based on client location.
Type: List of LocationRule objects
Mandatory-to-Specify: No. Default is allow all locations.
4.2.2.1. LocationRule
A LocationRule contains or references a list of 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.
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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: type
Description: Registered footprint type (see Section 7.1.1.1).
Type: String
Mandatory-to-Specify: Yes.
Property: value
Description: Footprint object conforming to the specification
associated with the registered footprint type.
Type: String
Mandatory-to-Specify: Yes.
4.2.3. TimeWindowACL Metadata
TimeWindowACL Metadata defines time-based restrictions.
Property: times
Description: Access control list which applies restrictions to
delivery based on request time.
Type: List of TimeWindowRule objects
Mandatory-to-Specify: No. Default is allow all time windows.
4.2.3.1. TimeWindowRule
A TimeWindowRule contains or references a list of TimeWindow objects
and the corresponding action.
Property: times
Description: List of time windows to which the rule applies.
Type: List of TimeWindow objects
Mandatory-to-Specify: Yes.
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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.
4.2.3.2. TimeWindow
A TimeWindow object describes a time range which may be applied by an
ACLRule, e.g. Start 09:00AM 01/01/2000 UTC End 17:00PM 01/01/2000
UTC.
Property: start
Description: The start time of the window.
Type: Time
Mandatory-to-Specify: Yes.
Property: end
Description: The end time of the window.
Type: Time
Mandatory-to-Specify: Yes.
4.2.4. ProtocolACL Metadata
ProtocolACL Metadata defines delivery protocol restrictions.
Property: protocols
Description: Access control list which applies restrictions to
delivery based on delivery protocol.
Type: List of ProtocolRule objects
Mandatory-to-Specify: No. Default is allow all protocols.
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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.
Property: action
Description: Defines whether the rule specifies protocols to
allow or deny.
Type: Enumeration [allow|deny]+
Mandatory-to-Specify: No. Default is allow all protocols.
Property: direction
Description: Defines whether the ProtocolRule specifies
protocols for acquisition or delivery.
Type: Enumeration [acquisition|delivery]
Mandatory-to-Specify: No. Default is to apply the rule to both
acquisition and delivery.
4.2.5. Authorization Metadata
Authorization Metadata define content authorization methods.
Property: methods
Description: Options for authenticating content requests. All
options in the list are equally valid.
Type: List of Auth objects
Mandatory-to-Specify: No. Default is no authorization
required.
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4.2.6. Auth
An Auth object defines authentication and authorization methods to be
used during content delivery and content acquisition.
Property: type
Description: Registered Auth type (see Section 7.1.1.3).
Type: String
Mandatory-to-Specify: Yes.
Property: value
Description: Auth object conforming to the specification
associated with the registered Auth type.
Type: String
Mandatory-to-Specify: Yes.
4.2.6.1. Credentials Auth Type
Credentials Auth is a type of Auth object with type "credentials"
(see Section 7.1.1.3). The CredentialsAuth object contains the
following properties:
Property: username
Description: Identification of user.
Type: String
Mandatory-to-Specify: Yes.
Property: password
Description: Password for user identified by username property.
Type: String
Mandatory-to-Specify: Yes.
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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 or to rely on other properties
of the Cache object.
4.2.8. Grouping
A Grouping object identifies a large group of content to which this
content belongs.
Property: ccid
Description: Content Collection identifier for an application-
specific purpose such as logging.
Type: String
Mandatory-to-Specify: No. Default is an empty string.
Property: sid
Description: Session identifier for an application-specific
purpose such as logging.
Type: String
Mandatory-to-Specify: No. Default is an empty string.
4.3. CDNI Metadata Simple Data Type Descriptions
This section describes the simpler data types that are used for
properties of CDNI Metadata objects.
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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: type
Description: The type of the object being referenced.
Type: String
Mandatory-to-Specify: No
4.3.2. Protocol
Protocol objects are used to specify registered protocols for content
acquisition or delivery (see Section 7.1.1.2).
Type: String
Mandatory-to-Specify: Yes
4.3.3. Endpoint
A hostname (with optional port) or an IP address (with optional
port).
Note: All implementations MUST support IPv4 addresses encoded as
specified by the 'IPv4address' rule in Section 3.2.2 of [RFC3986] and
MUST support all IPv6 address formats specified in [RFC4291]. Server
implementations SHOULD use IPv6 address formats specified in
[RFC5952].
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4.3.4. URI
A URI as specified in [RFC3986].
4.3.5. Time
A time value expressed in seconds since Unix epoch in the UTC
timezone.
5. CDNI Metadata Capabilities
CDNI Metadata is used to convey information pertaining to content
delivery from uCDN to dCDN. For optional metadata, it may be useful
for the uCDN to know if the dCDN supports the metadata, prior to
delegating any content requests to the dCDN. If optional-to-
implement metadata is mandatory-to-enforce and the dCDN does not
support it, any delegated requests for that content will fail, so
there is no reason to delegate those requests. Likewise, for any
metadata which may be assigned optional values, it may be useful for
the uCDN to know which values the dCDN supports, prior to delegating
any content requests to the dCDN. If a the optional value assigned
to a given piece of content's metadata is not supported by the dCDN,
any delegated requests for that content may fail, so there is likely
no reason to delegate those requests.
The CDNI Footprint and Capabilities Interface provides a means of
advertising capabilities from dCDN to uCDN. Support for optional
metadata and support for optional metadata values may be advertised
using the capabilities interface. This section describes the
capabilities advertisement requirements for the metadata defined in
Section 4.2
5.1. Protocol ACL Capabilities
The ProtoclACL object contains a list of Protocol values. The dCDN
MUST advertise which delivery protocols it supports so that the uCDN
knows what type of content requests it can redirect to the dCDN. If
the dCDN does not support a given acquisition or delivery protocol,
the uCDN should not delegate requests requiring those protocols to
the dCDN as the dCDN will not be able to properly acquire or deliver
the content.
ProtocolRules are defined for either acquisition or delivery. For
some CDNs, certain combinations of acquisition and delivery protocols
may not make sense (e.g., RTSP acquisition for HTTP delivery), while
other CDNs may support customized protocol adaptation. ProtocolACL
capabilities are not intended to define which combinations of
protocols should be used. ProtocolACL capabilties are only intended
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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 which authorization algorithms it supports so that the
uCDN knows what type of content requests it can redirect to the dCDN.
If the dCDN does not support a given authorization algorithm, the
uCDN should not delegate requests requiring that algorithm to the
dCDN as the dCDN will not be able to properly acquire the content or
enforce delivery restrictions.
6. CDNI Metadata interface
This section specifies an interface to enable a Downstream CDN to
retrieve CDNI Metadata objects from an Upstream CDN.
The interface can be used by a Downstream CDN to retrieve CDNI
Metadata objects either dynamically as required by the Downstream CDN
to process received requests (for example in response to receiving a
CDNI Request Routing request from an Upstream CDN or in response to
receiving a request for content from a User Agent) or in advance of
being required (for example in case of prepositioned CDNI Metadata
acquisition).
The CDNI Metadata interface is built on the principles of RESTful web
services. This means that requests and responses over the interface
are built around the transfer of representations of hyperlinked
resources. A resource in the context of the CDNI Metadata interface
is any object in the Data Model (as described in Section 3 through
Section 4).
In the general case a CDNI Metadata server makes each instance of an
addressable CDNI Metadata object available via a unique URI that
returns a representation of that instance of that CDNI Metadata
object. When an object needs to reference another addressable CDNI
Metadata object (for example a HostIndex object referencing a
HostMetadata object) it does so by including a link to the referenced
object.
CDNI Metadata servers are free to assign whatever structure they
desire to the URIs for CDNI Metadata objects and CDNI Metadata
clients MUST NOT make any assumptions regarding the structure of CDNI
Metadata URIs or the mapping between CDNI Metadata objects and their
associated URIs. Therefore any URIs present in the examples below
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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. Servers implementing the CDNI Metadata
interface MUST support the HTTP GET and HEAD methods.
The corresponding HTTP Response returns the status of the operation
in the HTTP Status Code and returns the current representation of the
resource (if appropriate) in the Response Body. HTTP Responses from
servers implementing the CDNI Metadata interface that contain a
response body SHOULD include an ETag to enable validation of cached
versions of returned resources.
The CDNI Metadata interface specified in this document is a read-only
interface. Therefore support for other HTTP methods such as PUT,
POST and DELETE etc. is not specified. Server implementations of
this interface SHOULD reject all methods other than GET and HEAD.
As the CDNI Metadata interface builds on top of HTTP, CDNI Metadata
servers may make use of any HTTP feature when implementing the CDNI
Metadata interface, for example a CDNI Metadata server may make use
of HTTP's caching mechanisms to indicate that the returned response/
representation can be reused without re-contacting the CDNI Metadata
server.
6.2. Retrieval of CDNI Metadata resources
In the general case a CDNI Metadata server makes each instance of an
addressable CDNI Metadata object available via a unique URI and
therefore in order to retrieve CDNI Metadata, a CDNI Metadata client
first makes a HTTP GET request for the URI of the HostIndex which
provides the CDNI Metadata client with a list of Hostnames for which
the upstream CDN may delegate content delivery to the downstream CDN.
In order to retrieve the CDNI Metadata for a particular request the
CDNI Metadata client processes the received HostIndex object and
finds the corresponding HostMetadata entry (by matching the hostname
in the request against the hostnames in the HostMatch). If the
HostMetadata is linked (rather than embedded), the CDNI metadata
client then makes a GET request for the URI specified in the href
property of the Link object which points to the HostMetadata object
itself.
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In order to retrieve the most specific metadata for a particular
request, the CDNI metadata client inspects the HostMetadata for
references to more specific PathMetadata objects. If any
PathMetadata match the request (and are linked rather than embedded),
the CDNI metadata client makes another GET request for the
PathMetadata. Each PathMetadata object may also include references
to yet more specific metadata. If this is the case, the CDNI
metadata client continues requesting PathMetadata recursively.
Where a downstream CDN is interconnected with multiple upstream CDNs,
the downstream CDN must decide which upstream CDN's CDNI metadata
should be used to handle a particular User Agent request.
When application level redirection (e.g. HTTP 302 redirects) is being
used between CDNs, it is expected that the downstream CDN will be
able to determine the upstream CDN that redirected a particular
request from information contained in the received request (e.g. via
the URI). With knowledge of which upstream CDN routed the request,
the downstream CDN can choose the correct metadata server from which
to obtain the HostIndex. Note that the HostIndex served by each uCDN
may be unique.
In the case of DNS redirection there is not always sufficient
information carried in the DNS request from User Agents to determine
the upstream CDN that redirected a particular request (e.g. when
content from a given host is redirected to a given downstream CDN by
more than one upstream CDN) and therefore downstream CDNs may have to
apply local policy when deciding which upstream CDN's metadata to
apply.
6.3. Bootstrapping
The URI for the HostIndex object of a given upstream CDN needs to be
either discovered by or configured in the downstream CDN. All other
objects/resources are then discoverable from the HostIndex object by
following the links in the HostIndex object and the referenced
HostMetadata and PathMetadata objects.
If the URI for the HostIndex object is not manually configured in the
downstream CDN then the HostIndex URI could be discovered. A
mechanism allowing the downstream CDN to discover the URI of the
HostIndex is outside the scope of this document.
6.4. Encoding
Object are resources that may be:
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o Addressable, where the object is a resource that may be retrieved
or referenced via its own URI.
o Embedded, where the object is contained (or inlined) within a
property of an addressable object.
In the descriptions of objects we use the term "X contains Y" to mean
either Y is directly embedded in X or that Y is linked to by X. It
is generally a deployment choice for the uCDN implementation to
decide when and which CDNI Metadata objects to embed and which are
separately addressable.
6.4.1. MIME Media Types
All MIME types are prefixed with "application/cdni." The MIME type
for each object matches the type name of that object as defined by
this document. 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 lists a few examples of
the MIME Media Type for each object (resource) that is retrievable
through the CDNI Metadata interface.
+--------------+---------------------------------------+
| Data Object | MIME Media Type |
+--------------+---------------------------------------+
| HostIndex | application/cdni.HostIndex.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
See http://www.iana.org/assignments/media-types/index.html for
reference.
6.4.2. JSON Encoding of Objects
CDNI Metadata objects are encoded as JSON objects containing a
dictionary of (key,value) pairs where the keys are the property names
and the values are the associated property values.
The keys of the dictionary are the names of the properties associated
with the object and are therefore dependent on the specific object
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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 and therefore by
convention any dictionary key defined by this document (for example
the names of CDNI Metadata object properties) MUST be represented in
lowercase.
In addition to the properties specific to each object type, the keys
defined below may be present in any object.
Key: base
Description: Provides a prefix for any relative URLs in the
object. This is similar to the XML base tag [XML-BASE]. If
absent, all URLs in the remainder of the document must be
absolute URLs.
Type: URI
Mandatory: No
Key: _links
Description: The links of this object to other addressable
objects. Any property may be replaced by a link to an object
with the same type as the property it replaces. 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. JSON Example
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.example.ucdn.com/video"
}
}
},
{
"host": "images.example.com",
"_links": {
"host-metadata" : {
"type": "application/cdni.HostMetadata.v1+json",
"href": "http://metadata.example.ucdn.com/images"
}
}
}
]
}
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.com/video" expecting a MIME type of
"application/cdni.HostMetadata.v1+json":
{
"metadata": [
{
"type": "application/cdni.SourceMetadata.v1+json",
"value": {
"sources": [
{
"_links": {
"auth": {
"type": "application/cdni.Auth.v1+json",
"href": "http://metadata.ucdn.example.com/auth1234"
}
},
"endpoint": "acq1.ucdn.example.com",
"protocol": "ftp"
},
{
"_links": {
"auth": {
"type": "application/cdni.Auth.v1+json",
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"href": "http://metadata.ucdn.example.com/auth1234"
}
},
"endpoint": "acq2.ucdn.example.com",
"protocol": "http"
}
]
}
},
{
"type": "application/cdni.LocationACL.v1+json",
"value": {
"locations": [
{
"locations": [
{ "iprange": "192.168.0.0/16" }
],
"action": "deny"
}
]
}
},
{
"type": "application/cdni.ProtocolACL.v1+json",
"value": {
"protocols": [
{
"protocols": [
"ftp"
],
"action": "deny"
}
]
}
}
],
"paths": [
{
"path-pattern": {
"pattern": "/videos/trailers/*"
},
"_links": {
"path-metadata": {
"type": "application/cdni.PathMetadata.v1+json",
"href": "http://metadata.ucdn.example.com/videos/trailers"
}
}
},
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{
"path-pattern": {
"pattern": "/videos/movies/*"
},
"_links": {
"pathmetadata": {
"type": "application/cdni.PathMetadata.v1+json",
"href": "http://metadata.ucdn.example.com/videos/movies"
}
}
}
]
}
Suppose the path of the requested resource matches the "/video/movies
/*" pattern, the next metadata requested would be for "http://
metadata.ucdn.example.com/video/movies" with an expected type of
"application/cdni.PathMetadata.v1+json":
{
"metadata": [],
"paths": [
{
"path-pattern": {
"pattern": "/videos/movies/hd/*"
},
"_links": {
"pathmetadata": {
"type": "application/cdni.PathMetadata.v1+json",
"href": "http://metadata.ucdn.example.com/videos/movies/hd"
}
}
}
]
}
Finally, if the path of the requested resource also matches the "/
videos/movies/hd/*" pattern, the downstream CDN would also fetch the
following object from "http://metadata.ucdn.example.com/videos/movies
/hd" with MIME type "application/cdni.PathMetadata.v1+json":
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{
"metadata": [
{
"type": "application/cdni.TimeWindowACL.v1+json",
"value": {
"times": [
"times": [
{
"start": "1213948800",
"end": "1327393200"
}
],
"type": "allow"
]
}
}
]
}
6.5. Extensibility
The set of property Metadata may be extended with proprietary and/or
custom property Metadata. The GenericMetadata object defined in
Section 4.1.7 allows any Metadata property to be included in either
the HostMetadata or PathMetadata lists.
Note: Identification of the property Metadata defining organization
in the property Metadata type decreases the possibility of property
Metadata type collision. The fully-qualified domain name of the
organization in reverse order may be used for this purpose.
6.5.1. Metadata Enforcement
At any given time, the set of property Metadata supported by the uCDN
may not match the set of property Metadata supported by the dCDN.
The uCDN may or may not know which property Metadata the dCDN
supports. In cases where the uCDN supports Metadata that the dCDN
does not, the dCDN MUST be aware of any Metadata marked as
"mandatory-to-enforce". If a CDN does not understand or is unable to
perform the functions associated with any "mandatory-to-enforce"
Metadata, the CDN MUST NOT service any requests for the corresponding
content.
Any standard which defines a new GenericMetadata Type MUST also
define whether or not the new metadata is mandatory-to-enforce.
Note: Ideally, uCDNs would not delegate content requests to a dCDN
which does not support the mandatory-to-enforce Metadata associated
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with the content being requested. However, even if the uCDN has a
priori knowledge of the Metadata supported by the dCDN (e.g., via the
CDNI capabilities interface or through out-of-band negotiation
between CDN operators) Metadata support may fluctuate or be
inconsistent (e.g., due to mis-communication, mis-configuration, or
temporary outage). Thus, the dCDN MUST evaluate all Metadata
associated with content requests and reject any requests where
"mandatory-to-enforce" Metadata associated with the content cannot be
enforced.
6.5.2. Metadata Override
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 specified by the
HTTP Content-Type header. Upon responding to a request for an
object, a metadata server MUST include a Content-Type header with the
MIME-type and version number of the object. HTTP requests sent to a
metadata server SHOULD include an Accept header with the MIME-type
and version of the expected object. Unless stated otherwise, the
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
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include a version. Any document which defines a new type of
GenericMetadata should specify the version number which it describes.
For example: "application/cdni.Location.v1+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
"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:
+----------------+---------------+---------+------+------+
| 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.
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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 type MUST:
1. Allocate a new type in the GenericMetadata Type Registry
(Section 7).
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.
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
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existing type definitions and prevent gratuitous additions to the
namespace.
The following table defines the initial Footprint type values:
+-------------+-------------------------------------+---------------+
| Type name | Description | Specification |
+-------------+-------------------------------------+---------------+
| IPv4 | Single IPv4 address | RFCthis |
| IPv6 | Single IPv6 address | RFCthis |
| IPv4Range | List of contiguous IPv4 addresses | RFCthis |
| | denoted by a start address and an | |
| | end address separated by a dash | |
| | (e.g., 192.168.0.1-192.168.0.20), | |
| | inclusive. | |
| IPv6Range | List of contiguous IPv6 addresses | RFCthis |
| | denoted by a start address and an | |
| | end address separated by a dash | |
| | (e.g., fc80::0001-fc80::0014), | |
| | inclusive. | |
| IPv4CIDR | IPv4 address block using slash | RFCthis |
| | prefix length notation (e.g., | |
| | 192.168.0.16/28). | |
| IPv6CIDR | IPv6 address block using slash | RFCthis |
| | prefix length notation (e.g., | |
| | fc80::0010/124). | |
| ASN | Autonomous System (AS) Number | RFCthis |
| CountryCode | ISO 3166-1 alpha-2 code | RFCthis |
| DVDRegion | DVD Region code (i.e., integer in | RFCthis |
| | the range 0-6). | |
+-------------+-------------------------------------+---------------+
7.1.1.2. Protocol Sub-Registry
The "CDNI Metadata Protocols" namespace defines the valid Protocol
object values in Section 4.3.2, used by the SourceMetadata and
ProtocolACL objects. Additions to the Protocol namespace conform to
the "Expert Review" policy as defined in [RFC5226]. The expert
review should verify that new type definitions do not duplicate
existing type definitions and prevent gratuitous additions to the
namespace.
The following table defines the initial Protocol values:
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+----------+----------------+---------------------------------------+
| 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:
+-------------+-------------------------------------+---------------+
| Type name | Description | Specification |
+-------------+-------------------------------------+---------------+
| credentials | Simple username and password | RFCthis |
| | authentication as defined by | |
| | Section 4.2.6.1. | |
+-------------+-------------------------------------+---------------+
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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. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
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[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010.
10.2. Informative References
[I-D.ietf-cdni-framework]
Peterson, L., Davie, B., and R. Brandenburg, "Framework
for CDN Interconnection", draft-ietf-cdni-framework-09
(work in progress), January 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.
[XML-BASE]
Marsh, J., Ed. and R. Tobin, Ed., "XML Base (Second
Edition) - http://www.w3.org/TR/xmlbase/", January 2009.
Appendix A. Relationship to the CDNI Requirements
Section 6 of [I-D.ietf-cdni-requirements] lists the requirements for
the CDNI Metadata Distribution interface. This section outlines
which of those requirements are met by the CDNI Metadata interface
specified in this document.
All metadata requirements are met either directly or indirectly by
the CDNI Metadata Interface described in this document, with the
clarifications or exceptions described in the following paragraphs.
Requirements related to pre-positioning of metadata are met by this
document on the assumption that other CDNI Interfaces are to be used
by the upstream CDN to trigger the pre-positioning of metadata by the
downstream CDN via the CDNI Metadata Interface. Triggering metadata
pre-positioning is beyond the scope of the CDNI Metadata interface.
However, the interface as described by this document supports pulling
metadata on-demand for the purpose of pre-positioning.
Requirement META-7 relating to modification of metadata by the
upstream CDN is met both by allowing timeouts on the cacheability of
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metadata objects and by allowing other CDNI interfaces to initiate a
refetch or purge of metadata.
Requirement META-18 relating to surrogate cache behavior parameters
is supported via extensibility. However, the example parameters in
META-18 are not described in this document.
Authors' Addresses
Ben Niven-Jenkins
Velocix (Alcatel-Lucent)
3 Ely Road
Milton, Cambridge CB24 6AA
UK
Email: ben@velocix.com
Rob Murray
Velocix (Alcatel-Lucent)
3 Ely Road
Milton, Cambridge CB24 6AA
UK
Email: rmurray@velocix.com
Grant Watson
Velocix (Alcatel-Lucent)
3 Ely Road
Milton, Cambridge CB24 6AA
UK
Email: gwatson@velocix.com
Matt Caulfield
Cisco Systems
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Phone: +1 978 936 9307
Email: mcaulfie@cisco.com
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Kent Leung
Cisco Systems
3625 Cisco Way
San Jose 95134
USA
Phone: +1 408 526 5030
Email: kleung@cisco.com
Kevin J. Ma
Azuki Systems, Inc.
43 Nagog Park
Acton, MA 01720
USA
Phone: +1 978-844-5100
Email: kevin.ma@azukisystems.com
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