Internet DRAFT - draft-cjlmw-cdni-metadata
draft-cjlmw-cdni-metadata
Network Working Group B. Niven-Jenkins
Internet-Draft R. Murray
Intended status: Standards Track G. Watson
Expires: January 10, 2013 Velocix (Alcatel-Lucent)
M. Caulfield
K. Leung
Cisco Systems
July 9, 2012
CDN Interconnect Metadata
draft-cjlmw-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
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 10, 2013.
Copyright Notice
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Design Principles . . . . . . . . . . . . . . . . . . . . . . 5
3. CDNI Metadata Data Model . . . . . . . . . . . . . . . . . . . 5
3.1. HostIndex, HostMetdata & PathMetadata objects . . . . . . 6
3.2. Remaining CDNI Metadata objects . . . . . . . . . . . . . 9
3.3. Metadata Inheritance . . . . . . . . . . . . . . . . . . . 12
4. Encoding-Independent CDNI Metadata Object Descriptions . . . . 12
4.1. CDNI Metadata Data Object Descriptions . . . . . . . . . . 12
4.1.1. HostIndex . . . . . . . . . . . . . . . . . . . . . . 13
4.1.2. HostMatch . . . . . . . . . . . . . . . . . . . . . . 13
4.1.3. HostMetadata . . . . . . . . . . . . . . . . . . . . . 13
4.1.4. Acquisition . . . . . . . . . . . . . . . . . . . . . 14
4.1.5. Delivery . . . . . . . . . . . . . . . . . . . . . . . 14
4.1.6. PathMatch . . . . . . . . . . . . . . . . . . . . . . 15
4.1.7. PathMetadata . . . . . . . . . . . . . . . . . . . . . 15
4.1.8. ACL . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1.9. ACLRule . . . . . . . . . . . . . . . . . . . . . . . 16
4.1.10. TimeWindow . . . . . . . . . . . . . . . . . . . . . . 16
4.1.11. Location . . . . . . . . . . . . . . . . . . . . . . . 17
4.1.12. Source . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1.13. Auth . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1.14. Link . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.2. CDNI Metadata Simple Data Type Descriptions . . . . . . . 19
4.2.1. Protocol . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.2. Endpoint . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.3. IPRange . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.4. Pattern . . . . . . . . . . . . . . . . . . . . . . . 20
4.2.5. PatternFlags . . . . . . . . . . . . . . . . . . . . . 20
4.2.6. URI . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.2.7. Time . . . . . . . . . . . . . . . . . . . . . . . . . 20
5. CDNI Metadata interface . . . . . . . . . . . . . . . . . . . 21
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5.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2. Retrieval of CDNI Metadata resources . . . . . . . . . . . 22
5.3. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 23
5.4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.4.1. MIME Media Types . . . . . . . . . . . . . . . . . . . 23
5.4.2. JSON Encoding of Objects . . . . . . . . . . . . . . . 24
5.4.2.1. JSON Example . . . . . . . . . . . . . . . . . . . 25
5.4.3. XML Encoding of Objects . . . . . . . . . . . . . . . 27
5.4.3.1. XML Example . . . . . . . . . . . . . . . . . . . 28
5.5. Extensibility . . . . . . . . . . . . . . . . . . . . . . 30
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
7. Security Considerations . . . . . . . . . . . . . . . . . . . 31
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.1. Normative References . . . . . . . . . . . . . . . . . . . 31
9.2. Informative References . . . . . . . . . . . . . . . . . . 31
Appendix A. Relationship to the CDNI Requirements . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
CDNI enables a downstream CDN to service content requests on behalf
of an upstream CDN. In the simplest use case, a content request
received by the downstream CDN provides sufficient information for
sending a response. More complex use cases require additional
context, i.e. metadata. 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 4.1 through
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
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o Property - a key / value pair where the key is a property name and
the value is the property value (possibly an object)
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 authoritative
hostname of the content and subsequently on the resource path of the
content. The data model associates a set of CDNI Metadata properties
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with a Hostname to form a default set of metadata properties for
content delivered for that Hostname. That default set of metadata
properties can be overridden by properties that apply to specific
paths within a URI.
Different Hostnames and URI paths will 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 on
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 remaining CDNI
Metadata objects and describes the relationships between those
objects as well as the relationships of those objects to HostMetadata
and PathMetadata objects.
Section 4.1 describes the specific properties of each object in more
detail.
3.1. HostIndex, HostMetdata & PathMetadata objects
A HostIndex object contains a list of Hostnames 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
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order to deliver the requested content.
The HostIndex links end-user facing Hostnames to HostMetadata
objects, which contain (or reference) the default CDNI Metadata
required to serve content for that Hostname. When looking up CDNI
Metadata, the downstream CDN looks up the requested Hostname in the
HostIndex, from there it can find HostMetadata which describes
delivery rules for a Hostname and PathMetadata which may override
those rules for given URI paths within the Hostname.
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| *Other Metadata Objects*
| +---------+ ************************
| | ^
| V |
| +------------+ |
+--|PathMetadata+----------------+
+------------+
Key: ----> = References
Figure 1: Relationships between the HostIndex, HostMetadata &
PathMetadata CDNI Metadata Objects
The table below describes the HostIndex, HostMetadata and
PathMetadata objects in more detail.
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+--------------+----------------------------------------------------+
| Data Object | Description |
+--------------+----------------------------------------------------+
| HostIndex | A HostIndex object lists the Hostnames 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 properties to be applied when a |
| | content request matches against the hostname. |
| HostMetadata | A HostMetadata object contains (or references) the |
| | default CDNI Metadata properties for content |
| | served from that hostname, i.e. the CDNI Metadata |
| | properties 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 properties for |
| | those specific URI paths. |
| 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 properties to be |
| | applied when a content request matches against the |
| | defined URI path pattern. |
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| PathMetadata | A PathMetadata object contains the CDNI Metadata |
| | properties 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. |
+--------------+----------------------------------------------------+
Table 1: HostIndex, HostMetadata and PathMetadata CDNI Metadata
Objects
3.2. Remaining CDNI Metadata objects
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. The properties
associated with the processing of User Agent requests fall into two
categories, Delivery and Acquisition. Delivery properties, such as
Location based restrictions, are contained or referenced within a
Delivery object. Acquisition properties, such as which Origin Server
to use to acquire the content, are contained or referenced within an
Acquisition Object. Delivery and Acquisition objects contain or
reference other CDNI Metadata objects to define the properties and
rules which should be applied when processing requests for content.
In some cases the rules that should be applied are complex but also
likely to be reusable and repeated across many HostMetadata or
PathMetadata objects.
The relationships between the HostMetadata and PathMetadata objects
and the other CDNI Metadata objects (Delivery object, Acquisition
object, etc.) required for CDNI request routing and delivery are
illustrated in Figure 2.
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+-------------+ +----------------+
+--------------+ +--> | Acquisition | -----> | Source |
| HostMetadata | | +-------------+ +----------------+
| - or - | ---+
| PathMetadata | | +-------------+ +----------------+
+--------------+ +--> | Delivery | --+--> | TimeWindow ACL |
+-------------+ | +----------------+
|
| +----------------+
+--> | Location ACL* |
| +----------------+
|
| +----------------+
+--> | Auth |
+----------------+
*example ACL
+----------------+ +----------------+
| Location ACL | = | ACL |
+----------------+ +----------------+
|
v
+----------------+
| ACL Rules |
+----------------+
|
v
+----------------+
| Location |
+----------------+
Key: ----> = References
Figure 2: Relationships between HostMetadata and PathMetadata and the
other CDNI Metadata Objects
The table below describes the remaining CDNI Metadata objects that
were not defined in Section 3.1.
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+-------------+-----------------------------------------------------+
| Data Object | Description |
+-------------+-----------------------------------------------------+
| Acquisition | Container object for metadata that applies to |
| | content acquisition. |
| Delivery | Container object for metadata that applies to |
| | content delivery. |
| Source | Information needed by a dCDN to acquire content. |
| | For example the host to contact, the protocol to |
| | use for acquisition and any authentication and |
| | authorization methods that should be used. |
| ACL | Contains or references a list of ACLRules that are |
| | used to define any delivery restrictions that must |
| | be applied e.g. Location restrictions or Time |
| | based restrictions. |
| ACLRule | Contains or references a list of objects which |
| | define to what the restrictions should be applied |
| | e.g. an ACLRule may reference a Location Object if |
| | a location based ACL is required. |
| TimeWindow | Start and end time used to specify windows of |
| | availability or unavailability for the content. |
| Location | Geographic or network location identified by |
| | country code, BGP AS number, or subnet to which |
| | content may (or may not) be delivered. |
| Auth | Method and credentials for authentication and |
| | authorization including URI-signing, token-base, |
| | etc. |
+-------------+-----------------------------------------------------+
Table 2: Content Distribution Metadata Data Objects
The relationships in Figure 1 and Figure 2 are summarised in Table 3
below and the properties of each object are described in Section 4.1.
+--------------+----------------------------------------------------+
| Data Object | Objects it References |
+--------------+----------------------------------------------------+
| HostIndex | 0 or more HostMetadata objects. |
| HostMetadata | 0 or more PathMatch objects. 0 or 1 Delivery |
| | objects. 0 or 1 Acquisition objects. |
| PathMatch | 1 PathMetadata object. |
| PathMetadata | 0 or more PathMatch objects. 0 or 1 Delivery |
| | objects. 0 or 1 Acquisition objects. |
| Acquisition | 0 or more Source objects. |
| Delivery | 0 or more ACL objects. 0 or more Auth objects. |
| ACL | 0 or more ACLRule objects. |
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| ACLRule | 0 or more Location objects or 0 or more TimeWindow |
| | objects. |
+--------------+----------------------------------------------------+
Table 3: Relationships between CDNI Metadata Objects
3.3. Metadata Inheritance
In the data model, a HostMetadata object may contain (or reference)
multiple PathMetadata objects. Each PathMetadata object may in turn
contain (or reference) other PathMetadata objects. These
relationships form a tree.
The tree of HostMetadata objects and PathMetadata objects forms an
inheritance tree. Each node in the tree inherits the property values
set by its parent.
In the tree, a child may override any property value which has been
set by its parent. If a HostMetadata object sets the value of a
property, that value may be overridden by a PathMetadata object (the
child of the HostMetadata object). If a PathMetadata object contains
(or references) other PathMetadata objects as children, then those
children PathMetadata objects may override the property values set by
the parent PathMetadata object.
If a child node overrides the value of a list, then the entire list
is replaced with the value set by the child node. If a child node
overrides the value of an object, then the whole object is replaced
with the value set by the child node.
4. Encoding-Independent CDNI Metadata Object Descriptions
This section provides the definitions of each object type declared in
Section 3. The definition of each object contains an unordered set
of properties. The type of some properties is another CDNI Metadata
object and 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
describes a URI and relationship that can be dereferenced to retrieve
the CDNI Metadata object that should be used as the value of that
property.
4.1. CDNI Metadata Data Object Descriptions
Each of the sub-sections below describes the properties associated
with the data 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. 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
Type: List of HostMatch
Mandatory: Yes.
4.1.2. HostMatch
The HostMatch object contains a hostname to match against and a
metadata object to apply if a match is found.
Property: hostname
Description: String to match against the requested host.
Type: String
Mandatory: Yes
Property: hostmetadata
Description: CDNI Metadata to apply when delivering content
that matches this pattern.
Type: HostMetadata
Mandatory: 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: acquisition
Description: Container for content acquisition related
metadata.
Type: Acquisition
Mandatory: No. No default.
Property: delivery
Description: Container for content delivery related metadata.
Type: Delivery
Mandatory: No. No default.
Property: paths
Description: Path specific rules. First match applies.
Type: List of PathMatch
Mandatory: No. Default apply the properties defined in this
HostMetadata object to all paths.
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Property: hostname
Description: The end-user facing Hostname for this HostMetadata
object.
Type: Hostname
Mandatory: Yes.
4.1.4. Acquisition
Metadata which 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: No. Defaults to empty list.
4.1.5. Delivery
Metadata related to content delivery, e.g. delivery restrictions or
content authorization methods.
Property: locations
Description: Access control list which applies restrictions to
delivery based on client location.
Type: ACL
Mandatory: No. Defaults is allow all locations.
Property: times
Description: Access control list which applies restrictions to
delivery based on request time.
Type: ACL
Mandatory: No. Defaults is allow all times.
Property: auth
Description: Options for authenticating content requests. All
options in the list are equally valid.
Type: List of Auth
Mandatory: No. Defaults is no auth.
Property: protocol
Description: The delivery protocol to be used for content
requests that match this HostMetadata object.
Type: protocol
Mandatory: Yes.
Property: active
Description: Enable or disable delivery from this host.
Type: boolean
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Mandatory: No. Default yes.
4.1.6. PathMatch
The PathMatch object contains an expression to match against and a
metadata object to apply if a match is found.
Property: pattern
Description: String to match against the requested path, i.e.
against the [RFC3986] path-absolute.
Type: Pattern
Mandatory: Yes
Property: patternflags
Description: Flags to control the pattern match.
Type: List of PatternFlags
Mandatory: No. Default Case-sensitive infix matching.
Property: pathmetadata
Description: CDNI Metadata to apply when delivering content
that matches this pattern.
Type: PathMetadata
Mandatory: Yes
4.1.7. 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.
PathMetadata objects may contain any of the properties of a
HostMetadata object with the following exceptions:
o PathMetadata objects MUST NOT contain a hostname property.
o PathMetadata objects MUST NOT contain a protocol property.
o The presence of an sources property is OPTIONAL.
4.1.8. ACL
An ACL object contains or references a list of ACLRule objects which
define a set of restrictions to apply to content delivery e.g.
Location restrictions. An ACL may reference or contain ACLRules
referencing or containing Location or TimeWindow objects but not
both.
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Property: aclrules
Description:
Type: List of ACLRule
Mandatory: No. Default no rules.
4.1.9. ACLRule
An ACLRule contains or references a list of either TimeWindow or
Location objects. ACLRule objects are used to construct ACL to apply
restrictions to content delivery.
Note: Although both the allow and deny properties are optional, one
and only one of them MUST be present in an ACLRule. An ACLRule must
also only refer to one of Location or TimeWindow but not both and
should only refer to the objects relevant to the ACL type as defined
by Delivery Metadata i.e. a Delivery Metadata object with an ACL with
relationship of LocationACL must not reference TimeWindow objects
further down in the Metadata hierarchy.
Property: allow
Description: List of either Locations (Location ACL) or Time
Windows (TimeWindow ACL) which must be allowed.
Type: List of Location or TimeWindow
Mandatory: No. Default implicit Allow.
Property: deny
Description: List of either Locations (Location ACL) or Time
Windows (TimeWindow ACL) which must be denied.
Type: List of Location or TimeWindow
Mandatory: No. Default implicit Deny.
4.1.10. TimeWindow
A TimeWindow object describes a time range which may be applied by an
ACLRule, e.g. Start 09:00AM 01/01/2000 End 17:00PM 01/01/2000.
Property: start
Description: The start time of the window.
Type: Time
Mandatory: Yes
Property: end
Description: The end time of the window.
Type: Time
Mandatory: Yes
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4.1.11. 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.
Property: iprange
Description: A set of IP Addresses.
Type: List of IPRange.
Mandatory: 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.]
4.1.12. 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: No. Default is no authentication.
Property: endpoints
Description: Origins from which the dCDN can acquire content.
Type: List of EndPoint
Mandatory: Yes.
Property: protocol
Description: Protocol to use for content acquisition.
Type: Protocol
Mandatory: Yes.
4.1.13. 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.
Property: type
Description: A string containing the authentication type "url-
signing", "url-token", "http-basic", or "http-digest". The
type dictates which optional fields are present and valid in
the rest of the object. The "url-signing" type refers to URL
signing authentication. The "url-token" type refers to token-
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based authentication. The "basic" and "digest" types refer to
HTTP Basic and Digest access authentication.
Type: String
Mandatory: Yes.
Property: algo
Description: A string containing the signature algorithm (e.g.
"md5", "sha-1", etc.).
Type: String
Mandatory: Yes, if type is "url-signing".
Property: symmetric
Description: A boolean if true, URL signing uses symmetric
keys, otherwise asymmetric.
Type: boolean
Mandatory: Yes, if type is "url-signing".
Property: key
Description: A hex-encoded number containing the public key for
verifying signatures, only valid if "symmetric" field is set to
false.
Type: boolean
Mandatory: Yes, if type is "url-signing".
Property: username
Description: A string containing the username for "basic" and
"digest" types.
Type: String
Mandatory: Yes, if type is "basic" or "digest".
Property: password
Description: A string containing the password for "basic" and
"digest" types.
Type: String
Mandatory: Yes, if type is "basic" or "digest".
4.1.14. 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
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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
4.2. CDNI Metadata Simple Data Type Descriptions
This section describes the simpler data types that are used for
properties of CDNI Metadata objects.
4.2.1. 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:
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.]
4.2.2. Endpoint
A hostname (with optional port) or an IP address (with optional
port).
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].
4.2.3. IPRange
One of:
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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].
4.2.4. Pattern
A pattern for string matching paths. The string may contain the
wildcards * and ?.
o * matches any sequence of characters (including the empty string).
o ? matches exactly one character.
Escaping: The three literals \ , * and ? should be escaped as \\, \*
and \?
4.2.5. PatternFlags
A set of flags indicating how a pattern match is made. The flags
are:
o Case-insensitive - Perform a case insensitive match (absence
indicates case-sensitive match).
o Prefix - Match against the start of the string (absence indicates
that a match may start anywhere in the string).
o Suffix - Match against the end of the string (absence indicates
that a match may end anywhere in the string).
Absence of both Prefix and Suffix results in a match against any part
of the string (infix).
4.2.6. URI
A URI as specified in [RFC3986].
4.2.7. 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 4.1).
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 Hosts (along with
their public facing 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 metadata should
handle a particular User Agent request.
In the case of where 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
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redirected a particular request from information contained in the
received request (e.g. via 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.
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 advertise 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 4 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 4: 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 of the object, the following three
additional 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":
{
"host": [
{
"hostname": "video.example.com",
"links": [
{
"rel": "hostmetadata",
"type": "HostMetadata",
"href": "http://metadata.ucdn.com/video"
}
]
},
{
"hostname": "images.example.com",
"links": [
{
"rel": "hostmetadata",
"type": "HostMetadata",
"href": "http://metadata.ucdn.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.com/video" expecting a MIME type of
"application/cdni.HostMetadata+json":
{
"hostname": "video.example.com",
"acquisition": {
"source": [
{
"links": [{
"rel": "auth",
"type": "Auth",
"href": "http://metadata.ucdn.com/auth1234"
}],
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"endpoint": "acq1.ucdn.com",
"protocol": "ftp"
},
{
"links": [{
"rel": "auth",
"type": "Auth",
"href": "http://metadata.ucdn.com/auth1234"
}],
"endpoint": "acq2.ucdn.com",
"protocol": "http"
}
]
},
"delivery": {
"location": {
"aclrule": {
"deny": { "iprange": "192.168.0.0/16" }
}
},
"auth": {
},
"protocol": "http",
"active": "true"
},
"path": [
{
"pattern": "/videos/trailers/*",
"patternflags": "prefix",
"links": [{
"rel": "pathmetadata",
"type": "PathMetadata",
"href": "http://metadata.ucdn.com/videos/trailers"
}]
},
{
"pattern": "/videos/movies/*",
"patternflags": "prefix",
"links": [{
"rel": "pathmetadata",
"type": "PathMetadata",
"href": "http://metadata.ucdn.com/videos/movies"
}]
}
]
}
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Suppose the path of the requested resource matches the "/video/
movies/*" pattern, the next metadata requested would be for
"http://metadata.ucdn.com/video/movies" with an expected type of
"application/cdni.PathMetadata":
{
"delivery": {
"auth": {
}
},
"path": {
"pattern": "/videos/movies/hd/*",
"patternflags": "prefix",
"links": [{
"rel": "pathmetadata",
"type": "PathMetadata",
"href": "http://metadata.ucdn.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.com/videos/movies/hd"
with MIME type "application/cdni.PathMetadata":
{
"delivery": {
"time": {
"aclrule": {
"allow": {
"start": "1213948800",
"end": "1327393200"
}
}
}
}
}
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
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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+json":
<HostIndex>
<host>
<hostname>video.example.com</hostname>
<link rel="hostmetadata" type="HostMetadata"
href="http://metadata.ucdn.com/video"/>
</host>
<host>
<hostname>images.example.com</hostname>
<link rel="hostmetadata" type="HostMetadata"
href="http://metadata.ucdn.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.com/video" expecting a MIME type of
"application/cdni.HostMetadata+json":
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<HostMetadata>
<hostname>video.example.com</hostname>
<acquisition>
<source>
<link rel="auth" type="Auth"
href="http://metadata.ucdn.com/auth1234"/>
<endpoint>acq1.ucdn.com</endpoint>
<protocol>ftp</protocol>
</source>
<source>
<link rel="auth" type="Auth"
href="http://metadata.ucdn.com/auth1234"/>
<endpoint>acq2.ucdn.com</endpoint>
<protocol>http</protocol>
</source>
</acquisition>
<delivery>
<location>
<aclrule>
<deny>
<iprange>192.168.0.0/16</iprange>
</deny>
</aclrule>
</location>
<auth></auth>
<protocol>http</protocol>
<active>true</active>
</delivery>
<path>
<pattern>/videos/trailers/*</pattern>
<patternflags>prefix</patternflags>
<link rel="pathmetadata" type="PathMetadata"
href="http://metadata.ucdn.com/videos/trailers"/>
</path>
<path>
<pattern>/videos/movies/*</pattern>
<patternflags>prefix</patternflags>
<link rel="pathmetadata" type="PathMetadata"
href="http://metadata.ucdn.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.com/video/movies" with an expected type of
"application/cdni.PathMetadata":
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<PathMetadata>
<delivery>
<auth></auth>
</delivery>
<path>
<pattern>/videos/movies/hd/*</pattern>
<patternflags>prefix</patternflags>
<link rel="pathmetadata" type="PathMetadata"
href="http://metadata.ucdn.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.com/videos/movies/hd"
with MIME type "application/cdni.PathMetadata":
<PathMetadata>
<delivery>
<time>
<aclrule>
<allow>
<start>1213948800</start>
<end>1327393200</end>
</allow>
</aclrule>
</time>
</delivery>
</PathMetadata>
5.5. Extensibility
The set of metadata properties may be extended with proprietary and /
or custom properties. New properties may be added to any existing
object.
The names of such properties MUST begin with an "x-" prefix. If a
property is vendor specific, then "x-vendor-" SHOULD be used as the
name prefix, where the "vendor" string is replaced by the name of the
vendor.
The values of new properties MAY include an "ignorable" property with
a boolean type. If "ignorable" is set to true, then request routers
and surrogates in any interconnected CDN MAY safely ignore the new
property. If "ignorable" is set to false, then a CDN which does not
understand the property MUST NOT service a request for the
corresponding content.
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6. IANA Considerations
This document requests the registration of the "application/cdni"
MIME type.
7. Security Considerations
The CDNI Metadata Interface is expected to be secured as a function
of the transport protocol (e.g. HTTP authentication).
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.
A malicious metadata client could request metadata for a piece of
content from an upstream CDN. However, given the current set of
metadata properties, no useful information would be compromised.
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.
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[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]
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-
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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.
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
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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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