CDN Interconnect Metadata
draft-ietf-cdni-metadata-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8006.
|
|
|---|---|---|---|
| Authors | Ben Niven-Jenkins , Rob Murray , Grant Watson , Matt Caulfield , Kent Leung , Kevin J. Ma | ||
| Last updated | 2012-12-18 (Latest revision 2012-10-02) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 8006 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Martin Stiemerling | ||
| Send notices to | cdni-chairs@tools.ietf.org, draft-ietf-cdni-metadata@tools.ietf.org |
draft-ietf-cdni-metadata-00
Network Working Group B. Niven-Jenkins
Internet-Draft R. Murray
Intended status: Standards Track G. Watson
Expires: April 5, 2013 Velocix (Alcatel-Lucent)
M. Caulfield
K. Leung
Cisco Systems
K. Ma
Azuki Systems, Inc.
October 2, 2012
CDN Interconnect Metadata
draft-ietf-cdni-metadata-00
Abstract
The CDNI Metadata Interface enables interconnected CDNs to exchange
content distribution metadata in order to enable content acquisition
and delivery. The CDNI metadata associated with a piece of content
provides a downstream CDN with sufficient information for the
downstream CDN to service content requests on behalf of an upstream
CDN. This document describes both the core set of CDNI metadata and
the protocol for exchanging that metadata.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 5, 2013.
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Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Design Principles . . . . . . . . . . . . . . . . . . . . . . 5
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 . . . . . . . . . . . . . . . . . . . 10
3.4. Metadata Naming . . . . . . . . . . . . . . . . . . . . . 10
4. Encoding-Independent CDNI Metadata Object Descriptions . . . . 11
4.1. CDNI Metadata Structural Object Descriptions . . . . . . . 11
4.1.1. HostIndex . . . . . . . . . . . . . . . . . . . . . . 11
4.1.2. HostMatch . . . . . . . . . . . . . . . . . . . . . . 12
4.1.3. HostMetadata . . . . . . . . . . . . . . . . . . . . . 12
4.1.4. PathMatch . . . . . . . . . . . . . . . . . . . . . . 12
4.1.5. PathMetadata . . . . . . . . . . . . . . . . . . . . . 13
4.1.6. PatternMatch . . . . . . . . . . . . . . . . . . . . . 13
4.1.7. GenericMetadata . . . . . . . . . . . . . . . . . . . 14
4.2. CDNI Metadata Property Object Descriptions . . . . . . . . 14
4.2.1. Source Metadata . . . . . . . . . . . . . . . . . . . 14
4.2.1.1. Source . . . . . . . . . . . . . . . . . . . . . . 14
4.2.2. LocationACL Metadata . . . . . . . . . . . . . . . . . 15
4.2.2.1. LocationRule . . . . . . . . . . . . . . . . . . . 15
4.2.2.2. Location . . . . . . . . . . . . . . . . . . . . . 15
4.2.3. TimeWindowACL Metadata . . . . . . . . . . . . . . . . 16
4.2.3.1. TimeWindowRule . . . . . . . . . . . . . . . . . . 16
4.2.3.2. TimeWindow . . . . . . . . . . . . . . . . . . . . 16
4.2.4. ProtocolACL Metadata . . . . . . . . . . . . . . . . . 17
4.2.4.1. ProtocolRule . . . . . . . . . . . . . . . . . . . 17
4.2.5. Authorization Metadata . . . . . . . . . . . . . . . . 17
4.2.6. Auth . . . . . . . . . . . . . . . . . . . . . . . . . 17
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4.3. CDNI Metadata Simple Data Type Descriptions . . . . . . . 18
4.3.1. Link . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.2. Protocol . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.3. Endpoint . . . . . . . . . . . . . . . . . . . . . . . 19
4.3.4. IPRange . . . . . . . . . . . . . . . . . . . . . . . 19
4.3.5. URI . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3.6. Time . . . . . . . . . . . . . . . . . . . . . . . . . 19
5. CDNI Metadata interface . . . . . . . . . . . . . . . . . . . 20
5.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 20
5.2. Retrieval of CDNI Metadata resources . . . . . . . . . . . 21
5.3. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 22
5.4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.4.1. MIME Media Types . . . . . . . . . . . . . . . . . . . 22
5.4.2. JSON Encoding of Objects . . . . . . . . . . . . . . . 23
5.4.2.1. JSON Example . . . . . . . . . . . . . . . . . . . 24
5.4.3. XML Encoding of Objects . . . . . . . . . . . . . . . 27
5.4.3.1. XML Example . . . . . . . . . . . . . . . . . . . 27
5.5. Extensibility . . . . . . . . . . . . . . . . . . . . . . 30
5.5.1. Metadata Enforcement . . . . . . . . . . . . . . . . . 30
5.5.2. Metadata Override . . . . . . . . . . . . . . . . . . 31
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
7. Security Considerations . . . . . . . . . . . . . . . . . . . 31
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.1. Normative References . . . . . . . . . . . . . . . . . . . 32
9.2. Informative References . . . . . . . . . . . . . . . . . . 32
Appendix A. Relationship to the CDNI Requirements . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
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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
[I-D.ietf-cdni-problem-statement] along with three other interfaces
that may be used to compose a CDNI solution (Control, Request Routing
and Logging). [I-D.davie-cdni-framework] expands on the information
provided in [I-D.ietf-cdni-problem-statement] 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 5).
1.1. Terminology
This document reuses the terminology defined in
[I-D.ietf-cdni-problem-statement].
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.
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2. Design Principles
The proposed CDNI Metadata Interface aims to achieve the following
design principles:
1. Cacheability of CDNI metadata objects
2. Deterministic mapping from content requests to CDNI metadata
properties
3. Support for DNS redirection as well as application-specific
redirection (for example HTTP redirection)
4. Minimal duplication of CDNI metadata
5. Leverage existing protocols
Cacheability improves the latency of acquiring metadata and therefore
improves the latency of serving content requests. The CDNI Metadata
Interface uses HTTP to achieve cacheability.
Deterministic mappings from content requests to metadata properties
eliminates ambiguity and ensures that the same 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
content requests to metadata properties. Metadata properties
describe how to acquire, authorize, and deliver content from a
downstream CDN. The data model relies on the assumption that these
metadata properties may be aggregated based on the hostname of the
content and subsequently on the resource path of the content. The
data model associates a set of CDNI Metadata properties with a
Hostname to form a default set of metadata properties for content
delivered for that Hostname. That default set of metadata properties
can be overridden by properties that apply to specific paths within a
URI.
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Different Hostnames and URI paths will contain 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.
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)
that 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
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objects via HostMatch objects. HostMetadata objects contain (or
reference) the default CDNI Metadata required to serve content for
that host. When looking up CDNI Metadata, the downstream CDN looks
up the requested Hostname (or IP address) in the HostIndex, from
there it can find HostMetadata which describes delivery rules for a
host and PathMetadata which may override those rules for given URI
paths within the host.
As well as containing the default CDNI Metadata for the specified
Hostname, HostMetadata and PathMetadata objects may also contain
PathMatch objects which in turn contain PathMetadata objects.
PathMatch objects override the CDNI Metadata in the HostMetadata
object or one or more preceding PathMetadata objects with more
specific CDNI Metadata that applies to content requests matching the
pattern defined in that PathMatch object.
For the purposes of retrieving CDNI Metadata all other required CDNI
Metadata objects and their properties are discoverable from the
appropriate HostMetadata, PathMatch and PathMetadata objects for the
requested content.
The relationships between the HostIndex, HostMatch, HostMetadata,
PathMatch and PathMetadata objects are described in Figure 1.
+---------+ +---------+ +------------+
|HostIndex+---->|HostMatch|---->|HostMetadata+----------------+
+---------+ +---------+ +------+-----+ |
| |
V V
+---------+ **************************
+--->|PathMatch| *Generic Metadata Objects*
| +---------+ **************************
| | ^
| V |
| +------------+ |
+--|PathMetadata+----------------+
+------------+
Key: ----> = References
Figure 1: Relationships between the HostIndex, HostMetadata &
PathMetadata CDNI Metadata Objects
The relationships in Figure 1 are summarised in Table 1 below.
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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 the Hostnames (and/or |
| | IP addresses) that an upstream CDN can provide |
| | CDNI Metadata for and the URIs to use for |
| | retrieving that CDNI Metadata. For example, if |
| | "example.com" is a content provider, the |
| | HostIndex object may include an entry for |
| | "example.com" with the URI of the associated |
| | HostMetadata object. These hostnames are |
| | contained inside a list of 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 |
| | content request matches against the hostname. |
| 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. |
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| PathMatch | A PathMatch object defines a pattern to match |
| | against the requested path, and contains or |
| | references a PathMetadata object which contains |
| | (or references) the CDNI Metadata objects to be |
| | applied when a content request matches against |
| | the defined URI path pattern. |
| PathMetadata | A PathMetadata object contains the CDNI |
| | GenericMetadata objects for content served with |
| | 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 property objects which define the |
| | specific policies and attributes needed to |
| | properly deliver the associated content. |
+-----------------+-------------------------------------------------+
Table 2: HostIndex, HostMetadata and PathMetadata CDNI Metadata
Objects
3.2. Generic CDNI Metadata Object Properties
The HostMetadata and PathMetadata objects contain or can reference
other CDNI Metadata objects that contain properties which describe
how User Agent requests for content should be processed, for example
where to acquire the content, authorization rules that should be
applied, delivery location restrictions and so on. Each such CDNI
Metadata object is a specialization of a CDNI GenericMetadata object.
The GenericMetadata object abstracts the basic information required
for Metadata override and opaque Metadata distribution, from the
specifics of any given property (e.g., property semantics,
enforcement options, serialization rules, etc.).
The GenericMetadata object defines the type of properties contained
within it as well as whether or not the properties are mandatory to
enforce. If the dCDN does not understand or support the property
type and the property type is mandatory to enforce, the dCDN MUST NOT
serve the content to the User Agent. If the dCDN does not understand
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or support the property type it is also not going to be able to
properly deserialize and reserialize the Metadata for cascaded
distribution.
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 for 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
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. 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, 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. For example:
ext.vendor1.featurex
ext.vendor1.featurey
ext.vendor2.featurex
Metadata types defined by this document are not hierarchical.
[Ed. It is intended that Metadata capability advertisements will
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allow either individual Metadata names or Metadata bundle identifiers
to be used. Need to have a procedure for defining and distributing
bundle information to be used in Metadata capability advertisement.]
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.
4.1.1. HostIndex
The HostIndex object is the entry point into the CDNI Metadata
hierarchy. An incoming content request is matched against the list
of hosts to find the HostMatch object which applies to the request.
Property: hosts
Description: List of HostMatch objects.
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Type: List of HostMatch
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 references 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
Description: List of host related metadata.
Type: List of GenericMetadata
Mandatory-to-Specify: Yes.
Property: paths
Description: Path specific rules. First match applies.
Type: List of PathMatch
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
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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
Description: List of path related metadata.
Type: List of GenericMetadata
Mandatory-to-Specify: Yes.
Property: paths
Description: Path specific rules. First match applies.
Type: List of PathMatch
Mandatory-to-Specify: No.
4.1.6. PatternMatch
A PatternMatch object contains the pattern string and flags that
describe the PathMatch expression.
Property: pattern
Description: >A pattern for string matching. The pattern may
contain the wildcards * and ?, where * matches any sequence of
characters (including the empty string) and ? matches exactly
one character. The three literals \ , * and ? should be
escaped as \\, \* and \?
Type: String
Mandatory-to-Specify: Yes.
Property: case-sensitive
Description: Flag indicating whether or not case-sensitive
matching should be used.
Type: Boolean
Mandatory-to-Specify: No. Default is case-insensitive match.
Property: match-query-string
Description: Flag indicating whether or not the query string
should be included in the pattern match.
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Type: Boolean
Mandatory-to-Specify: No. Default is not to include query
strings when matching.
4.1.7. GenericMetadata
A GenericMetadata object is a abstraction for managing individual
CDNI Metadata properties in an opaque manner.
Property: type
Description: CDNI Metadata property object type.
Type: String
Mandatory-to-Specify: Yes.
Property: value
Description: CDNI Metadata property object.
Type: matches the type property above
Mandatory-to-Specify: Yes.
Property: mandatory-to-enforce
Description: Flag identifying whether or not the enforcement of
the property Metadata is required.
Type: Boolean
Mandatory-to-Specify: Yes.
Property: safe-to-redistribute
Description: Flag identifying whether or not the the property
Metadata may be safely redistributed without modification.
Type: Boolean
Mandatory-to-Specify: No. Default is allow transparent
redistribution.
4.2. CDNI Metadata Property Object Descriptions
4.2.1. Source Metadata
Source Metadata provides the dCDN information about content
acquisition e.g. how to contact an uCDN Surrogate or an Origin
Server. 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.
Type: List of Source
Mandatory-to-Specify: No.
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
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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
Mandatory-to-Specify: Yes.
Property: protocol
Description: Protocol to use for content acquisition.
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
Mandatory-to-Specify: No. Default is allow all locations.
4.2.2.1. LocationRule
A LocationRule contains or references a list of Location objects.
LocationRule objects are used to construct a LocationACL to apply
restrictions to content delivery.
Property: locations
Description: List of locations to which the rule applies.
Type: List of Location
Mandatory-to-Specify: Yes.
Property: action
Description: Defines whether the rule specifies locations to
allow or deny.
Type: Enumeration [allow|deny]
Mandatory-to-Specify: Yes.
4.2.2.2. Location
A Location object describes a Location which may be applied by an
ACLRule, e.g. a Location may be an IPv4 address range or a geographic
location.
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Property: iprange
Description: A set of IP Addresses.
Type: List of IPRange.
Mandatory-to-Specify: Yes.
[Ed: Location as specified above only supports the Class 1a names
described in [I-D.jenkins-cdni-names]. Need to add support for Class
1b names to a later version.]
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
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.
TimeWindowRule objects are used to construct a TimeWindowACL to apply
restrictions to content delivery.
Property: times
Description: List of time windows to which the rule applies.
Type: List of TimeWindow
Mandatory-to-Specify: Yes.
Property: action
Description: Defines whether the rule specifies time windows to
allow or deny.
Type: Enumeration [allow|deny]
Mandatory-to-Specify: Yes.
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
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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
Mandatory-to-Specify: No. Default is allow all protocols.
4.2.4.1. ProtocolRule
A ProtocolRule contains or references a list of Protocol objects.
ProtocolRule objects are used to construct a ProtocolACL to apply
restrictions to content delivery.
Property: protocols
Description: List of protocols to which the rule applies.
Type: List of protocol
Mandatory-to-Specify: Yes.
Property: action
Description: Defines whether the rule specifies protocols to
allow or deny.
Type: Enumeration [allow|deny]
Mandatory-to-Specify: Yes.
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
Mandatory-to-Specify: No. Default is no authorization
required.
4.2.6. Auth
An Auth object defines authentication and authorization methods to be
used during content delivery and content acquisition, e.g. methods
such as tokenization and URL Signing.
[Ed. Need to synchronize authentication configuration with CDNI URL
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signing draft definitions.]
[Ed. Need to consider how to separate protocol specific method
configuration (e.g., HTTP basic/digest authentication), which must
match the HostMatch protocol, from protocol agnostic method
configurations (e.g., URL signing/tokenization).]
4.3. CDNI Metadata Simple Data Type Descriptions
This section describes the simpler data types that are used for
properties of CDNI Metadata objects.
4.3.1. Link
A link object may be used in place of any of the objects described
above. Links can be used to avoid duplication if the same metadata
information is repeated within the metadata tree. When a link
replaces an object, its href property is set to the URI of the
resource, its rel property is set to the name of the property it is
replacing, and its type property is set to the type of the object it
is replacing.
Property: href
Description: The URI of the of the addressable object being
referenced.
Type: URI
Mandatory: Yes
Property: rel
Description: The Relationship between the referring object and
the object it is referencing.
Type: String
Mandatory: Yes
Property: type
Description: The type of the object being referenced.
Type: String
Mandatory: Yes
4.3.2. Protocol
This type only appears in Links. Links with this type are not
machine readable but rather represent particular feature sets of a
protocol defined in a specification and implemented in code. The URI
contained in the link needs to be defined for each delivery protocol
with an associated interoperable feature set.
The following examples are illustrative:
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o http://url.cdni.ietf.example/protocol/delivery/http/rfcABCD
o http://url.cdni.ietf.example/protocol/delivery/rtmp/rfcEFGH
o http://url.vendorY.ietf.example/protocol/delivery/rtmp/releaseP.Q
[Editor's Note: It may be more appropriate to use the 'tag' URI
scheme [RFC4151] for these URIs.]
4.3.3. Endpoint
A hostname (with optional port) or an IP address (with optional
port).
Note: All implementations MUST support IPv4 addresses encoded as
specified by the 'IPv4address' rule in Section 3.2.2 of [RFC3986] and
MUST support all IPv6 address formats specified in [RFC4291]. Server
implementations SHOULD use IPv6 address formats specified in
[RFC5952].
4.3.4. IPRange
One of:
o A range of consecutive IP addresses (IPv4 or IPv6) expressed as
Address1-Address2 which does not have to be to power of two
aligned, for example the range 192.0.2.1-192.0.2.10 is valid. The
first Address in the range MUST be 'lower' than the final address
in the range.
o A valid IP subnet (IPv4 or IPv6) expressed using CIDR notation.
o A single IP address (IPv4 or IPv6).
Note: Client implementations MUST support IPv4 addresses encoded as
specified by the 'IPv4address' rule in Section 3.2.2 of [RFC3986] and
MUST support all IPv6 address formats specified in [RFC4291]. Server
implementations SHOULD use IPv6 address formats specified in
[RFC5952].
4.3.5. URI
A URI as specified in [RFC3986].
4.3.6. Time
A time value expressed in seconds since Unix epoch in the UTC
timezone.
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5. 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.
The CDNI Metadata interface is built on the principles of RESTful web
services. This means that requests and responses over the interface
are built around the transfer of representations of hyperlinked
resources. A resource in the context of the CDNI Metadata interface
is any object in the Data Model (as described in Section 3 through
Section 4).
In the general case a CDNI Metadata server makes each instance of an
addressable CDNI Metadata object available via a unique URI that
returns a representation of that instance of that CDNI Metadata
object. When an object needs to reference another addressable CDNI
Metadata object (for example a HostIndex object referencing a
HostMetadata object) it does so by including a link to the referenced
object.
CDNI Metadata servers are free to assign whatever structure they
desire to the URIs for CDNI Metadata objects and CDNI Metadata
clients MUST NOT make any assumptions regarding the structure of CDNI
Metadata URIs or the mapping between CDNI Metadata objects and their
associated URIs. Therefore any URIs present in the examples below
are purely illustrative and are not intended impose a definitive
structure on CDNI Metadata interface implementations.
5.1. 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
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response body SHOULD include an ETag to enable validation of cached
versions of returned resources.
The CDNI Metadata interface specified in this document is a read-only
interface. Therefore support for other HTTP methods such as PUT,
POST and DELETE etc. is not specified. 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.
5.2. 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 that the
upstream CDN may delegate 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 HostIndex). The CDNI
metadata client then makes a GET request for the URI specified in the
href key of that Host's entry in the HostIndex.
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, 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
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the URI in case of HTTP redirection across CDNs). 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 sufficient information
carried in the DNS request from User Agents to determine the upstream
CDN that redirected a particular request and therefore downstream
CDNs may have to apply local policy when deciding which upstream
CDN's metadata to apply.
5.3. 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 via the
CDNI Control interface. An upstream CDN would provide the URI of the
HostIndex object to the downstream CDN via the CDNI Control
Interface.
5.4. Encoding
Object are resources that may be:
o Addressable, where the object is a resource that may be retrieved
or referenced via its own URI.
o Embedded, where the object is contained (or inlined) within a
property of an addressable object.
In the descriptions of objects we use the term "X contains Y" to mean
either Y is directly embedded in X or that Y is linked to by X. It is
generally a deployment choice for the uCDN implementation to decide
when and which CDNI Metadata objects to embed and which are
separately addressable.
5.4.1. MIME Media Types
All MIME types are prefixed with "application/cdni." The MIME type
for each object matches the type name of that object as defined by
this document.Table 3 lists a few examples of the MIME Media Type for
each object (resource) that is retrievable through the CDNI Metadata
interface. The MIME type suffix depends on the metadata encoding,
either "+xml" or "+json".
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+--------------+-------------------------------+
| Data Object | MIME Media Type |
+--------------+-------------------------------+
| HostIndex | application/cdni.HostIndex |
| HostMatch | application/cdni.HostMatch |
| HostMetadata | application/cdni.HostMetadata |
| PathMatch | application/cdni.PathMatch |
| PathMetadata | application/cdni.PathMetadata |
+--------------+-------------------------------+
Table 3: MIME Media Types for CDNI Metadata resources
See http://www.iana.org/assignments/media-types/index.html for
reference.
5.4.2. JSON Encoding of Objects
One possible encoding for a CDNI Metadata object is a JSON object
containing a dictionary of (key,value) pairs where the keys are the
property names and the values are the associated property values.
The keys of the dictionary are the names of the properties associated
with the object and are therefore dependent on the specific object
being encoded (i.e. dependent on the MIME Media Type of the returned
resource). Likewise, the values associated with each key are
dependent on the specific object being encoded (i.e. dependent on the
MIME Media Type of the returned resource).
Dictionary keys in JSON are case sensitive and therefore any
dictionary key defined by this document (for example the names of
CDNI Metadata object properties) MUST always 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.
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Type: List of Link
Mandatory: Yes
5.4.2.1. JSON Example
A downstream CDN may request the HostIndex and receive the following
object of type "application/cdni.HostIndex+json":
{
"hosts": [
{
"host": "video.example.com",
"links": [
{
"rel": "host-metadata",
"type": "application/cdni.HostMetadata",
"href": "http://metadata.example.ucdn.com/video"
}
]
},
{
"host": "images.example.com",
"links": [
{
"rel": "host-metadata",
"type": "application/cdni.HostMetadata",
"href": "http://metadata.ucdn.example.com/images"
}
]
}
]
}
If the incoming request has a Host header with "video.example.com"
then the downstream CDN would fetch from the next metadata object
from "http://metadata.ucdn.example.com/video" expecting a MIME type
of "application/cdni.HostMetadata+json":
{
"metadata": [
{
"type": "application/cdni.SourceMetadata",
"value": {
"sources": [
{
"links": [{
"rel": "auth",
"type": "application/cdni.Auth",
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"href": "http://metadata.ucdn.example.com/auth1234"
}],
"endpoint": "acq1.ucdn.example.com",
"protocol": "ftp"
},
{
"links": [{
"rel": "auth",
"type": "application/cdni.Auth",
"href": "http://metadata.ucdn.example.com/auth1234"
}],
"endpoint": "acq2.ucdn.example.com",
"protocol": "http"
}
]
}
},
{
"type": "application/cdni.LocationACL",
"value": {
"locations": [
{
"locations": [
{ "iprange": "192.168.0.0/16" }
],
"action": "deny"
}
]
}
},
{
"type": "application/cdni.ProtocolACL",
"value": {
"protocols": [
{
"protocols": [
"ftp"
],
"action": "deny"
}
]
}
}
],
"paths": [
{
"path-pattern": {
"pattern": "/videos/trailers/*"
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},
"links": [{
"rel": "path-metadata",
"type": "application/cdni.PathMetadata",
"href": "http://metadata.ucdn.example.com/videos/trailers"
}]
},
{
"path-pattern": {
"pattern": "/videos/movies/*"
},
"links": [{
"rel": "pathmetadata",
"type": "application/cdni.PathMetadata",
"href": "http://metadata.ucdn.example.com/videos/movies"
}]
}
]
}
Suppose the path of the requested resource matches the "/video/
movies/*" pattern, the next metadata requested would be for
"http://metadata.ucdn.example.com/video/movies" with an expected type
of "application/cdni.PathMetadata":
{
"metadata": [],
"paths": [
{
"path-pattern": {
"pattern": "/videos/movies/hd/*"
},
"links": [{
"rel": "pathmetadata",
"type": "application/cdni.PathMetadata",
"href": "http://metadata.ucdn.example.com/videos/movies/hd"
}]
}
]
}
Finally, if the path of the requested resource also matches the
"/videos/movies/hd/*" pattern, the downstream CDN would also fetch
the following object from
"http://metadata.ucdn.example.com/videos/movies/hd" with MIME type
"application/cdni.PathMetadata":
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{
"metadata": [
{
"type": "application/cdni.TimeWindowACL",
"value": {
"times": [
"times": [
{
"start": "1213948800",
"end": "1327393200"
}
],
"type": "allow"
]
}
}
]
}
5.4.3. XML Encoding of Objects
Another possible encoding for a CDNI Metadata object is an XML
document containing elements with tag names which match property
names and values which match the associated property values.
Tag names of elements 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 element are
dependent on the specific object being encoded (i.e. dependent on the
MIME Media Type of the returned resource).
Lists are encoded by repeating the singular form of a property name.
For example the "hosts" property is a list of "HostMatch" objects.
This list would be encoded as multiple "host" elements.
Link objects are a special case. If a Link object replaces a
property then a "link" element replaces the expected element. The
properties of the Link object are encoded as XML attributes. The
type attribute is set to the MIME type of the target object. The
href attribute is set to the URI of the target object. The rel
attribute is set to the name of the element being replaced.
5.4.3.1. XML Example
A downstream CDN may request the HostIndex and receive the following
object of type "application/cdni.HostIndex+xml":
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<HostIndex>
<host>
<host>video.example.com</host>
<link rel="host-metadata" type="application/cdni.HostMetadata"
href="http://metadata.ucdn.example.com/video"/>
</host>
<host>
<host>images.example.com</host>
<link rel="host-metadata" type="application/cdni.HostMetadata"
href="http://metadata.ucdn.example.com/images"/>
</host>
</HostIndex>
If the incoming request has a Host header with "video.example.com"
then the downstream CDN would fetch from the next metadata object
from "http://metadata.ucdn.example.com/video" expecting a MIME type
of "application/cdni.HostMetadata+xml":
<HostMetadata>
<metadata>
<type>application/cdni.SourceMetadata</type>
<value>
<sources>
<link rel="auth" type="application/cdni.Auth"
href="http://metadata.ucdn.example.com/auth1234"/>
<endpoint>acq1.ucdn.example.com</endpoint>
<protocol>ftp</protocol>
</source>
<source>
<link rel="auth" type="application/cdni.Auth"
href="http://metadata.ucdn.example.com/auth1234"/>
<endpoint>acq2.ucdn.example.com</endpoint>
<protocol>http</protocol>
</source>
</value>
</metadata>
<metadata>
<type>application/cdni.LocationACL</type>
<value>
<location>
<location>
<iprange>192.168.0.0/16</iprange>
</location>
<action>deny</type>
</location>
</value>
</metadata>
<metadata>
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<type>application/cdni.ProtocolACL</type>
<value>
<protocol>
<protocol>ftp</protocol>
<action>deny</action>
</protocol>
</value>
</metadata>
<path>
<path-pattern>
<pattern>/videos/trailers/*"</pattern>
</path-pattern>
<link rel="path-metadata" type="application/cdni.PathMetadata"
href="http://metadata.ucdn.example.com/videos/trailers"/>
</path>
<path>
<path-pattern>
<pattern>/videos/movies/*"</pattern>
</path-pattern>
<link rel="path-metadata" type="application/cdni.PathMetadata"
href="http://metadata.ucdn.example.com/videos/movies"/>
</path>
</HostMetadata>
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":
<PathMetadata>
<path>
<path-pattern>
<pattern>/videos/movies/hd/*</pattern>
</path-pattern>
<link rel="path-metadata" type="application/cdni.PathMetadata"
href="http://metadata.ucdn.example.com/videos/movies/hd"/>
</path>
</PathMetadata>
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":
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<PathMetadata>
<metadata>
<type>application/cdni.TimeWindowACL</type>
<value>
<time>
<time>
<start>1213948800</start>
<end>1327393200</end>
</time>
<type>allow</type>
</time>
</metadata>
</PathMetadata>
5.5. Extensibility
The set of property Metadata may be extended with proprietary and/or
custom property Metadata. The GenericMetadata object defined in
Section 4.1.7 allows any Metadata property to be included in either
the HostMetadata or PathMetadata lists. As described in Section 3.4,
it is suggested that proprietary and/or custom property Metadata be
identified by the "ext." prefix in an appropriately descriptive type
which conveys the organization defining the property Metadata and the
function of the property Metadata.
Note: Identification of the property Metadata defining organization
in the property Metadata type decreases the possibility of property
Metadata type collision.
5.5.1. 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.
Note: Ideally, uCDNs would not delegate content requests to a dCDN
which does not support the 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). The dCDN
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MUST evaluate all Metadata associated with content requests and
reject any requests where "mandatory-to-enforce" Metadata associated
with the content cannot be enforced.
5.5.2. 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, ext.vendor1.Auth, and
ext.vendor2.Auth) all override an existing Metadata (e.g., cdni.Auth)
and all are marked as "mandatory-to-enforce", it may be ambiguous
which Metadata should be applied, especially if the functionality of
the Metadata conflict.
As described in Section 3.3, Metadata override only applies to
Metadata objects of the same exact type, found in HostMetadata and
nested PathMetadata structures. The CDNI Metadata interface does not
support enforcement of dependencies between different Metadata types.
It is the responsibility of the CSP and the CDN operators to ensure
that Metadata assigned to a given content asset 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. IANA Considerations
This document requests the registration of the "application/cdni"
MIME type.
[Ed. Need to consider a registry for Metadata type identifiers.]
7. Security Considerations
The CDNI Metadata Interface is expected to be secured as a function
of the transport protocol (e.g. HTTP authentication, HTTPS, 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
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CDN to a malicious origin server instead of the actual origin server.
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.
8. Acknowledgements
The authors would like to thank David Ferguson and Francois le
Faucheur for their valuable comments and input to this document.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010.
9.2. Informative References
[I-D.davie-cdni-framework]
Davie, B. and L. Peterson, "Framework for CDN
Interconnection", draft-davie-cdni-framework-00 (work in
progress), July 2011.
[I-D.ietf-cdni-problem-statement]
Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", draft-ietf-cdni-problem-statement-03 (work in
progress), January 2012.
[I-D.ietf-cdni-requirements]
Leung, K. and Y. Lee, "Content Distribution Network
Interconnection (CDNI) Requirements",
draft-ietf-cdni-requirements-02 (work in progress),
December 2011.
[I-D.zyp-json-schema]
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Zyp, K. and G. Court, "A JSON Media Type for Describing
the Structure and Meaning of JSON Documents",
draft-zyp-json-schema-03 (work in progress),
November 2010.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4151] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme",
RFC 4151, October 2005.
[RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
Syndication Format", RFC 4287, December 2005.
[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. The
following paragraphs describe notable exceptions.
Requirements related to pre-positioning of metadata are not met
directly by this document. 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-13 relating to feedback from the downstream CDN to
the upstream CDN with respect to metadata is not directly supported
by the pull-based interface described in this document. As an
alternative, the downstream CDN may use the CDNI Logging interface to
convey error conditions related to 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.
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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
Kent Leung
Cisco Systems
3625 Cisco Way
San Jose 95134
USA
Phone: +1 408 526 5030
Email: kleung@cisco.com
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Kevin J. Ma
Azuki Systems, Inc.
43 Nagog Park
Acton, MA 01720
USA
Phone: +1 978-844-5100
Email: kevin.ma@azukisystems.com
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