wdiff rfc8006v6.txt rfc8006.txt

Internet Engineering Task Force (IETF) B. Niven-Jenkins
Request for Comments: 8006 Nokia R. Murray
Category: Standards Track R. Murray Nokia
ISSN: 2070-1721 Velocix (Alcatel-Lucent) M. Caulfield
Cisco Systems
K. Ma
Ericsson
November 2016

Content Delivery Network Interconnection (CDNI) Metadata

Abstract

The Content Delivery Network Interconnection (CDNI) Metadata
interface enables interconnected Content Delivery Networks (CDNs) to
exchange content distribution metadata in order to enable content
acquisition and delivery. The CDNI Metadata associated with a piece
of content provides a downstream CDN with sufficient information for
the downstream CDN to service content requests on behalf of an
upstream CDN. This document describes both a base set of CDNI
Metadata and the protocol for exchanging that metadata.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8006.

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
1.2. Supported Metadata Capabilities . . . . . . . . . . . . . 5
2. Design Principles . . . . . . . . . . . . . . . . . . . . . . 6
3. CDNI Metadata Object Model . . . . . . . . . . . . . . . . . 7
3.1. HostIndex, HostMatch, HostMetadata, PathMatch,
PatternMatch, and PathMetadata Objects . . . . . . . . . 8
3.2. Generic CDNI Metadata Objects . . . . . . . . . . . . . . 10
3.3. Metadata Inheritance and Override . . . . . . . . . . . . 13
4. CDNI Metadata Objects . . . . . . . . . . . . . . . . . . . . 14
4.1. Definitions of the CDNI Structural Metadata Objects . . . 15
4.1.1. HostIndex . . . . . . . . . . . . . . . . . . . . . . 15
4.1.2. HostMatch . . . . . . . . . . . . . . . . . . . . . . 16
4.1.3. HostMetadata . . . . . . . . . . . . . . . . . . . . 17
4.1.4. PathMatch . . . . . . . . . . . . . . . . . . . . . . 18
4.1.5. PatternMatch . . . . . . . . . . . . . . . . . . . . 19
4.1.6. PathMetadata . . . . . . . . . . . . . . . . . . . . 20
4.1.7. GenericMetadata . . . . . . . . . . . . . . . . . . . 21
4.2. Definitions of the Initial Set of CDNI GenericMetadata
Objects . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2.1. SourceMetadata . . . . . . . . . . . . . . . . . . . 23
4.2.1.1. Source . . . . . . . . . . . . . . . . . . . . . 24
4.2.2. LocationACL Metadata . . . . . . . . . . . . . . . . 25
4.2.2.1. LocationRule . . . . . . . . . . . . . . . . . . 26
4.2.2.2. Footprint . . . . . . . . . . . . . . . . . . . . 27
4.2.3. TimeWindowACL . . . . . . . . . . . . . . . . . . . . 28
4.2.3.1. TimeWindowRule . . . . . . . . . . . . . . . . . 29
4.2.3.2. TimeWindow . . . . . . . . . . . . . . . . . . . 30
4.2.4. ProtocolACL Metadata . . . . . . . . . . . . . . . . 31
4.2.4.1. ProtocolRule . . . . . . . . . . . . . . . . . . 32
4.2.5. DeliveryAuthorization Metadata . . . . . . . . . . . 32
4.2.6. Cache . . . . . . . . . . . . . . . . . . . . . . . . 33
4.2.7. Auth . . . . . . . . . . . . . . . . . . . . . . . . 35
4.2.8. Grouping . . . . . . . . . . . . . . . . . . . . . . 36
4.3. CDNI Metadata Simple Data Type Descriptions . . . . . . . 36
4.3.1. Link . . . . . . . . . . . . . . . . . . . . . . . . 37
4.3.1.1. Link Loop Prevention . . . . . . . . . . . . . . 38
4.3.2. Protocol . . . . . . . . . . . . . . . . . . . . . . 38
4.3.3. Endpoint . . . . . . . . . . . . . . . . . . . . . . 38
4.3.4. Time . . . . . . . . . . . . . . . . . . . . . . . . 39
4.3.5. IPv4CIDR . . . . . . . . . . . . . . . . . . . . . . 39
4.3.6. IPv6CIDR . . . . . . . . . . . . . . . . . . . . . . 39
4.3.7. ASN . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.3.8. CountryCode . . . . . . . . . . . . . . . . . . . . . 40
5. CDNI Metadata Capabilities . . . . . . . . . . . . . . . . . 40
6. CDNI Metadata Interface . . . . . . . . . . . . . . . . . . . 41
6.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 41
6.2. Retrieval of CDNI Metadata Resources . . . . . . . . . . 42
6.3. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 43
6.4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . 43
6.5. Extensibility . . . . . . . . . . . . . . . . . . . . . . 44
6.6. Metadata Enforcement . . . . . . . . . . . . . . . . . . 44
6.7. Metadata Conflicts . . . . . . . . . . . . . . . . . . . 45
6.8. Versioning . . . . . . . . . . . . . . . . . . . . . . . 46
6.9. Media Types . . . . . . . . . . . . . . . . . . . . . . . 47
6.10. Complete CDNI Metadata Example . . . . . . . . . . . . . 47
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51
7.1. CDNI Payload Types . . . . . . . . . . . . . . . . . . . 51
7.1.1. CDNI MI HostIndex Payload Type . . . . . . . . . . . 52
7.1.2. CDNI MI HostMatch Payload Type . . . . . . . . . . . 52
7.1.3. CDNI MI HostMetadata Payload Type . . . . . . . . . . 52
7.1.4. CDNI MI PathMatch Payload Type . . . . . . . . . . . 53
7.1.5. CDNI MI PatternMatch Payload Type . . . . . . . . . . 53
7.1.6. CDNI MI PathMetadata Payload Type . . . . . . . . . . 53
7.1.7. CDNI MI SourceMetadata Payload Type . . . . . . . . . 53
7.1.8. CDNI MI Source Payload Type . . . . . . . . . . . . . 53
7.1.9. CDNI MI LocationACL Payload Type . . . . . . . . . . 54
7.1.10. CDNI MI LocationRule Payload Type . . . . . . . . . . 54
7.1.11. CDNI MI Footprint Payload Type . . . . . . . . . . . 54
7.1.12. CDNI MI TimeWindowACL Payload Type . . . . . . . . . 54
7.1.13. CDNI MI TimeWindowRule Payload Type . . . . . . . . . 54
7.1.14. CDNI MI TimeWindow Payload Type . . . . . . . . . . . 55
7.1.15. CDNI MI ProtocolACL Payload Type . . . . . . . . . . 55
7.1.16. CDNI MI ProtocolRule Payload Type . . . . . . . . . . 55
7.1.17. CDNI MI DeliveryAuthorization Payload Type . . . . . 55
7.1.18. CDNI MI Cache Payload Type . . . . . . . . . . . . . 55
7.1.19. CDNI MI Auth Payload Type . . . . . . . . . . . . . . 56
7.1.20. CDNI MI Grouping Payload Type . . . . . . . . . . . . 56
7.2. "CDNI Metadata Footprint Types" Registry . . . . . . . . 56
7.3. "CDNI Metadata Protocol Types" Registry . . . . . . . . . 57
8. Security Considerations . . . . . . . . . . . . . . . . . . . 57
8.1. Authentication and Integrity . . . . . . . . . . . . . . 57
8.2. Confidentiality and Privacy . . . . . . . . . . . . . . . 58
8.3. Securing the CDNI Metadata Interface . . . . . . . . . . 58
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 59
9.1. Normative References . . . . . . . . . . . . . . . . . . 59
9.2. Informative References . . . . . . . . . . . . . . . . . 61
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 62
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 62

1. Introduction

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

The CDNI Metadata interface (MI) is discussed in [RFC7336] along with
four other interfaces that can be used to compose a CDNI solution
(the CDNI Control interface, the CDNI Request Routing Redirection
interface, the CDNI Footprint & Capabilities Advertisement interface
(FCI), and the CDNI Logging interface). [RFC7336] describes each
interface and the relationships between them. The requirements for
the CDNI Metadata interface are specified in [RFC7337].

The CDNI Metadata associated with a piece of content (or with a set
of content) provides a dCDN with sufficient information for servicing
content requests on behalf of a uCDN, in accordance with the policies
defined by the uCDN.

This document defines a CDNI Metadata interface that enables a dCDN
to obtain CDNI Metadata from a uCDN so that the dCDN can properly
process and respond to:

o Redirection requests received over the CDNI Request Routing
Redirection interface [RFC7975].

o Content requests received directly from User Agents.

Specifically, this document defines:

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

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

o An HTTP web service for the transfer of CDNI Metadata (Section 6).

1.1. Terminology

This document reuses the terminology defined in [RFC6707].

Additionally, the following terms are used throughout this document
and are defined as follows:

o Object - a collection of properties.

o Property - a key and value pair where the key is a property name
and the value is the property value or another object.

This document uses the phrase "[Object] A contains [Object] B" for
simplicity when a strictly accurate phrase would be "[Object] A
contains or references (via a Link object) [Object] B".

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 [RFC2119].

1.2. Supported Metadata Capabilities

Only the metadata for a small set of initial capabilities is
specified in this document. This set provides the minimum amount of
metadata for basic CDN interoperability while still meeting the
requirements set forth by [RFC7337].

The following high-level functionality can be configured via the CDNI
Metadata objects specified in Section 4:

o Acquisition Source: Metadata for allowing a dCDN to fetch content
from a uCDN.

o Delivery Access Control: Metadata for restricting (or permitting)
access to content based on any of the following factors:

* Location

* Time window

* Delivery protocol

o Delivery Authorization: Metadata for authorizing dCDN User Agent
requests.

o Cache Control: Metadata for controlling cache behavior of the
dCDN.

The metadata encoding described by this document is extensible in
order to allow for future additions to this list.

The set of metadata specified in this document covers the initial
capabilities above. It is only intended to support CDNI for the
delivery of content by a dCDN using HTTP/1.1 [RFC7230] and for a dCDN
to be able to acquire content from a uCDN using either HTTP/1.1 or
HTTP/1.1 over Transport Layer Security (TLS) [RFC2818].

Supporting CDNI for the delivery of content using unencrypted HTTP/2
[RFC7540] (as well as for a dCDN to acquire content using unencrypted
HTTP/2 or HTTP/2 over TLS) requires the registration of these
protocol names in the "CDNI Metadata Protocol Types" registry
(Section 7.3).

Delivery of content using HTTP/1.1 over TLS or HTTP/2 over TLS SHOULD
follow the guidelines set forth in [RFC7525]. Offline configuration
of TLS parameters between CDNs is beyond the scope of this document.

2. Design Principles

The CDNI Metadata interface was designed to achieve the following
objectives:

1. Cacheability of CDNI Metadata objects;

2. Deterministic mapping from redirection requests and content
requests to CDNI Metadata properties;

3. Support for DNS redirection as well as application-specific
redirection (for example, HTTP redirection);

4. Minimal duplication of CDNI Metadata; and

5. Leveraging of existing protocols.

Cacheability can decrease the latency of acquiring metadata while
maintaining its freshness and can therefore decrease the latency of
serving content requests and redirection requests, without
sacrificing accuracy. The CDNI Metadata interface uses HTTP and its
existing caching mechanisms to achieve CDNI Metadata cacheability.

Deterministic mapping from content to metadata properties eliminates
ambiguity and ensures that policies are applied consistently by all
dCDNs.

Support for both HTTP and DNS redirection ensures that the CDNI
Metadata meets the same design principles for both HTTP-based and
DNS-based redirection schemes.

Minimal duplication of CDNI Metadata improves storage efficiency in
the CDNs.

Leveraging existing protocols avoids reinventing common mechanisms
such as data structure encoding (by leveraging I-JSON (Internet JSON)
[RFC7493]) and data transport (by leveraging HTTP [RFC7230]).

3. CDNI Metadata Object Model

The CDNI Metadata object model describes a data structure for mapping
redirection requests and content requests to metadata properties.
Metadata properties describe how to acquire content from a uCDN,
authorize access to content, and deliver content from a dCDN. The
object model relies on the assumption that these metadata properties
can be grouped based on the hostname of the content and subsequently
on the resource path (URI) of the content. The object model
associates a set of CDNI Metadata properties with a hostname to form
a default set of metadata properties for content delivered on behalf
of that hostname. That default set of metadata properties can be
overridden by properties that apply to specific paths within a URI.

Different hostnames and URI paths will be associated with different
sets of CDNI Metadata properties in order to describe the required
behavior when a dCDN Surrogate or request router is processing User
Agent requests for content at that hostname and URI path. As a
result of this structure, significant commonality could 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 grouped together into a single network or
geographic location is likely to be common for a number of different
hostnames; 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 could be applied to multiple hostnames
delivered through the CDN.

In order to enable the CDNI Metadata for a given hostname and URI
path to be decomposed into reusable sets of CDNI Metadata properties,
the CDNI Metadata interface splits the CDNI Metadata into separate
objects. Efficiency is improved by enabling a single CDNI Metadata
object (that is shared across hostnames and/or URI paths) to be
retrieved and stored by a dCDN once, even if it is referenced by the
CDNI Metadata for multiple hostnames and/or URI paths.

Important Note: Any CDNI Metadata object A that contains another CDNI
Metadata object B can include a Link object specifying a URI that can
be used to retrieve object B, instead of embedding object B within
object A. The remainder of this document uses the phrase "[Object] A
contains [Object] B" for simplicity when a strictly accurate phrase
would be "[Object] A contains or references (via a Link object)
[Object] B". It is generally a deployment choice for the uCDN
implementation to decide when to embed CDNI Metadata objects and when
to reference separate resources via Link objects.

Section 3.1 introduces a high-level description of the HostIndex,
HostMatch, HostMetadata, PathMatch, PatternMatch, and PathMetadata
objects, and describes the relationships between them.

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 specified by this document that can be contained within a
CDNI GenericMetadata object.

3.1. HostIndex, HostMatch, HostMetadata, PathMatch, PatternMatch, and
PathMetadata Objects

The relationships between the HostIndex, HostMatch, HostMetadata,
PathMatch, PatternMatch, and PathMetadata objects are described in
Figure 1.

+---------+ +---------+ +------------+
|HostIndex+-(*)->|HostMatch+-(1)->|HostMetadata+-------(*)------+
+---------+ +---------+ +------+-----+ |
| |
(*) |
| V
--> Contains or references V *****************
(1) One and only one +---------+ *GenericMetadata*
(*) Zero or more +--->|PathMatch| * Objects *
| +----+---++ *****************
| | | ^
(*) (1) (1) +------------+ |
| | +->|PatternMatch| |
| V +------------+ |
| +------------+ |
+--+PathMetadata+-------(*)------+
+------------+

Figure 1: Relationships between CDNI Metadata Objects
(Diagram Representation)

A HostIndex object (see Section 4.1.1) contains an array of HostMatch
objects (see Section 4.1.2) that contain hostnames (and/or IP
addresses) for which content requests might be delegated to the dCDN.
The HostIndex is the starting point for accessing the uCDN CDNI
Metadata data store. It enables the dCDN to deterministically
discover which CDNI Metadata objects it requires in order to deliver
a given piece of content.

The HostIndex links hostnames (and/or IP addresses) to HostMetadata
objects (see Section 4.1.3) via HostMatch objects. A HostMatch
object defines a hostname (or IP address) to match against a
requested host and contains a HostMetadata object.

HostMetadata objects contain the default GenericMetadata objects (see
Section 4.1.7) required to serve content for that host. When looking
up CDNI Metadata, the dCDN looks up the requested hostname (or IP
address) against the HostMatch entries in the HostIndex; from there,
it can find HostMetadata, which describes the default metadata
properties for each host as well as PathMetadata objects (see
Section 4.1.6), via PathMatch objects (see Section 4.1.4). PathMatch
objects define patterns, contained inside PatternMatch objects (see
Section 4.1.5), to match against the requested URI path.
PatternMatch objects contain the pattern strings and flags that
describe the URI path to which a PathMatch applies. PathMetadata
objects contain the GenericMetadata objects that apply to content
requests matching the defined URI path pattern. PathMetadata
properties override properties previously defined in HostMetadata or
less-specific PathMatch paths. PathMetadata objects can contain
additional PathMatch objects to recursively define more-specific URI
paths to which GenericMetadata properties might be applied.

A GenericMetadata object contains individual CDNI Metadata objects
that define the specific policies and attributes needed to properly
deliver the associated content. For example, a GenericMetadata
object could describe the source from which a CDN can acquire a piece
of content. The GenericMetadata object is an atomic unit that can be
referenced by HostMetadata or PathMetadata objects.

For example, if "example.com" is a content provider, a HostMatch
object could include an entry for "example.com" with the URI of the
associated HostMetadata object. The HostMetadata object for
"example.com" describes the metadata properties that apply to
"example.com" and could contain PathMatches for
"example.com/movies/*" and "example.com/music/*", which in turn
reference corresponding PathMetadata objects that contain the
properties for those more-specific URI paths. The PathMetadata
object for "example.com/movies/*" describes the properties that apply
to that URI path. It could also contain a PathMatch object for
"example.com/movies/hd/*", which would reference the corresponding
PathMetadata object for the "example.com/movies/hd/" path prefix.

The relationships in Figure 1 are also represented in tabular format
in Table 1 below.

Table 1: Relationships between CDNI Metadata Objects
(Table Representation)

3.2. Generic CDNI Metadata Objects

The HostMetadata and PathMetadata objects contain other CDNI Metadata
objects that contain properties that describe how User Agent requests
for content should be processed -- for example, where to acquire the
content from, authorization rules that should be applied,
geo-blocking restrictions, and so on. Each such CDNI Metadata object
is a specialization of a CDNI GenericMetadata object. The
GenericMetadata object abstracts the basic information required for
metadata override and metadata distribution, from the specifics of
any given property (i.e., property semantics, enforcement options,
etc.).

The GenericMetadata object defines the properties contained within it
as well as whether or not the properties are "mandatory-to-enforce".
If the dCDN does not understand or support a mandatory-to-enforce
property, the dCDN MUST NOT serve the content. If the property is
not mandatory-to-enforce, then that GenericMetadata object can be
safely ignored and the content request can be processed in accordance
with the rest of the CDNI Metadata.

Although a CDN MUST NOT serve content to a User Agent if a
mandatory-to-enforce property cannot be enforced, it could still be
safe to redistribute that metadata (the "safe-to-redistribute"
property) to another CDN without modification. For example, in the
cascaded CDN case, a transit CDN (tCDN) could convey
mandatory-to-enforce metadata to a dCDN. For metadata that does not
require customization or translation (i.e., metadata that is
safe-to-redistribute), the data representation received off the wire
MAY be stored and redistributed without being understood or supported
by the tCDN. However, for metadata that requires translation,
transparent redistribution of the uCDN metadata values might not be
appropriate. Certain metadata can be safely, though perhaps not
optimally, redistributed unmodified. For example, a source
acquisition address might not be optimal if transparently
redistributed, but it might still work.

Redistribution safety MUST be specified for each GenericMetadata
property. If a CDN does not understand or support a given
GenericMetadata property that is not safe-to-redistribute, the CDN
MUST set the "incomprehensible" flag to true for that GenericMetadata
object before redistributing the metadata. The "incomprehensible"
flag signals to a dCDN that the metadata was not properly transformed
by the tCDN. A CDN MUST NOT attempt to use metadata that has been
marked as "incomprehensible" by a uCDN.

tCDNs MUST NOT change the value of mandatory-to-enforce or
safe-to-redistribute when propagating metadata to a dCDN. Although a
tCDN can set the value of "incomprehensible" to true, a tCDN MUST NOT
change the value of "incomprehensible" from true to false.

Table 2 describes the action to be taken by a tCDN for the different
combinations of mandatory-to-enforce ("MtE") and safe-to-redistribute
("StR") properties when the tCDN either does or does not understand
the metadata in question:

Table 2: Action to Be Taken by a tCDN for the Different Combinations
of MtE and StR Properties

Table 3 describes the action to be taken by a dCDN for the different
combinations of mandatory-to-enforce and "incomprehensible" (Incomp)
properties, when the dCDN either does or does not understand the
metadata in question:

Table 3: Action to Be Taken by a dCDN for the Different Combinations
of MtE and Incomp Properties

3.3. Metadata Inheritance and Override

In the metadata object model, a HostMetadata object can contain
multiple PathMetadata objects (via PathMatch objects). Each
PathMetadata object can in turn contain other PathMetadata objects.
HostMetadata and PathMetadata objects form an inheritance tree where
each node in the tree inherits or overrides the property values set
by its parent.

GenericMetadata objects of a given type override all GenericMetadata
objects of the same type previously defined by any parent object in
the tree. GenericMetadata objects of a given type previously defined
by a parent object in the tree are inherited when no object of the
same type is defined by the child object. For example, if
HostMetadata for the host "example.com" contains GenericMetadata
objects of types LocationACL and TimeWindowACL (where "ACL" means
"Access Control List") while a PathMetadata object that applies to
"example.com/movies/*" defines an alternate GenericMetadata object of
type TimeWindowACL, then:

o The TimeWindowACL defined in the PathMetadata would override the
TimeWindowACL defined in the HostMetadata for all User Agent
requests for content under "example.com/movies/", and

o The LocationACL defined in the HostMetadata would be inherited for
all User Agent requests for content under "example.com/movies/".

A single HostMetadata or PathMetadata object MUST NOT contain
multiple GenericMetadata objects of the same type. If an array of
GenericMetadata contains objects of duplicate types, the receiver
MUST ignore all but the first object of each type.

4. CDNI Metadata Objects

Section 4.1 provides the definitions of each metadata object type
introduced in Section 3. These metadata objects are described as
structural metadata objects, as they provide the structure for host
and URI path-based inheritance and identify which GenericMetadata
objects apply to a given User Agent content request.

Section 4.2 provides the definitions for a base set of core metadata
objects that can be contained within a GenericMetadata object. These
metadata objects govern how User Agent requests for content are
handled. GenericMetadata objects can contain other GenericMetadata
objects as properties; these can be referred to as sub-objects. As
with all CDNI Metadata objects, the value of the GenericMetadata
sub-objects can be either a complete serialized representation of the
sub-object or a Link object that contains a URI that can be
dereferenced to retrieve the complete serialized representation of
the property sub-object.

Section 6.5 discusses the ability to extend the base set of
GenericMetadata objects specified in this document with additional
standards-based or vendor-specific GenericMetadata objects that might
be defined in the future in separate documents.

dCDNs and tCDNs MUST support the parsing of all CDNI Metadata objects
specified in this document. A dCDN does not have to implement the
underlying functionality represented by non-structural
GenericMetadata objects (though that might restrict the content that
a given dCDN will be able to serve). uCDNs as generators of CDNI
Metadata only need to support generating the CDNI Metadata that they
need in order to express the policies required by the content they
are describing. See Section 6.4 for more details on the specific
encoding rules for CDNI Metadata objects.

Note: In the following sections, the term "mandatory-to-specify" is
used to convey which properties MUST be included for a given
structural or GenericMetadata object. When mandatory-to-specify is
specified as "Yes" for an individual property, it means that if the
object containing that property is included in a metadata response,
then the mandatory-to-specify property MUST also be included
(directly or by reference) in the response. For example, a HostMatch
property object without a host to match against does not make sense;
therefore, the "host" property is mandatory-to-specify inside a
HostMatch object.

4.1. Definitions of the CDNI Structural Metadata Objects

The subsections below describe the structural objects introduced in
Section 3.1.

4.1.1. HostIndex

The HostIndex object is the entry point into the CDNI Metadata
hierarchy. It contains an array of HostMatch objects. An incoming
content request is checked against the hostname (or IP address)
specified by each of the listed HostMatch objects to find the
HostMatch object that applies to the request.

Property: hosts

Description: Array of HostMatch objects. Hosts (HostMatch
objects) MUST be evaluated in the order they appear, and the
first HostMatch object that matches the content request being
processed MUST be used.

Type: Array of HostMatch objects

Mandatory-to-Specify: Yes.

Example HostIndex object containing two HostMatch objects, where the
first HostMatch object is embedded and the second HostMatch object is
referenced:

{
"hosts": [
{
<Properties of embedded HostMatch object>
},
{
"type": "MI.HostMatch",
"href": "https://metadata.ucdn.example/hostmatch1234"
}
]
}

4.1.2. HostMatch

The HostMatch object contains a hostname or IP address to match
against content requests. The HostMatch object also contains a
HostMetadata object to apply if a match is found.

Property: host

Description: Hostname or IP address and optional port to match
against the requested host, i.e., the host and port as
described in [RFC3986]. In order for a hostname or IP address
in a content request to match the hostname or IP address in the
"host" property, the value from the content request when
converted to lowercase MUST be identical to the value of the
"host" property when converted to lowercase. All
implementations MUST support IPv4 addresses encoded as
specified by the "IPv4address" rule in Section 3.2.2 of
[RFC3986]. IPv6 addresses MUST be encoded in one of the IPv6
address formats specified in [RFC5952], although receivers MUST
support all IPv6 address formats specified in [RFC4291].
Hostnames MUST conform to the Domain Name System (DNS) syntax
defined in [RFC1034] and [RFC1123]. Internationalized Domain
Names (IDNs) must first be transformed to the A-label form
[RFC5890] as per [RFC5891].

Type: Endpoint

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.

Example HostMatch object with an embedded HostMetadata object:

{
"host": "video.example.com",
"host-metadata": {
<Properties of embedded HostMetadata object>
}
}
Example HostMatch object referencing (via a Link object; see
Section 4.3.1) a HostMetadata object:

{
"host": "video.example.com",
"host-metadata": {
"type": "MI.HostMetadata",
"href": "https://metadata.ucdn.example/host1234"
}
}

4.1.3. HostMetadata

A HostMetadata object contains the CDNI Metadata properties for
content served for a particular host (defined in the HostMatch
object) and possibly child PathMatch objects.

Property: metadata

Description: Array of host-related metadata.

Type: Array of GenericMetadata objects

Mandatory-to-Specify: Yes.

Property: paths

Description: Path-specific rules. Path patterns (PathMatch
objects) MUST be evaluated in the order they appear, and the
first (and only the first) PathMatch object that matches the
content request being processed MUST be used.

Type: Array of PathMatch objects

Mandatory-to-Specify: No. Default is that there are no
more-specific paths to evaluate (i.e., an empty list).

Example HostMetadata object containing a number of embedded
GenericMetadata objects that will describe the default metadata for
the host and an embedded PathMatch object that contains a path for
which metadata exists that overrides the default metadata for the
host:

{
"metadata": [
{
<Properties of first embedded GenericMetadata object>
},
{
<Properties of second embedded GenericMetadata object>
},

...

{
<Properties of Nth embedded GenericMetadata object>
}
],
"paths": [
{
<Properties of embedded PathMatch object>
}
]
}

4.1.4. PathMatch

A PathMatch object contains a PatternMatch object with a path to
match against a resource's URI path, as well as how to handle URI
query parameters. The PathMatch object also contains a PathMetadata
object with GenericMetadata to apply if the resource's URI matches
the pattern within the PatternMatch object.

Property: path-pattern

Description: Pattern to match against the requested
resource's URI.

Type: PatternMatch

Mandatory-to-Specify: Yes.

Property: path-metadata

Description: CDNI Metadata to apply when delivering content
that matches the associated PatternMatch.

Type: PathMetadata

Mandatory-to-Specify: Yes.

Example PathMatch object referencing the PathMetadata object to use
for URIs that match the case-sensitive URI path pattern "/movies/*"
(contained within an embedded PatternMatch object):

{
"path-pattern": {
"pattern": "/movies/*",
"case-sensitive": true
},
"path-metadata": {
"type": "MI.PathMetadata",
"href": "https://metadata.ucdn.example/host1234/pathDCE"
}
}

4.1.5. PatternMatch

A PatternMatch object contains the pattern string and flags that
describe the pattern expression.

Property: pattern

Type: String

Mandatory-to-Specify: Yes.

Property: case-sensitive

Description: Flag indicating whether or not case-sensitive
matching should be used. Note: Case insensitivity applies to
ALPHA characters in the URI path prior to percent-decoding
[RFC3986].

Type: Boolean

Mandatory-to-Specify: No. Default is case-insensitive match
(i.e., a value of False).

Example PatternMatch object that matches the case-sensitive URI path
pattern "/movies/*":

{
"pattern": "/movies/*",
"case-sensitive": true
}

4.1.6. PathMetadata

A PathMetadata object contains the CDNI Metadata properties for
content requests that match against the associated URI path (defined
in a PathMatch object).

Note that if DNS-based redirection is employed, then a dCDN will be
unable to evaluate any metadata at the PathMetadata level or below
because only the hostname of the content request is available at
Request Routing time. dCDNs SHOULD still process all PathMetadata
for the host before responding to the redirection request to detect
if any unsupported metadata is specified. If any metadata not
supported by the dCDN is marked as mandatory-to-enforce, the dCDN
SHOULD NOT accept the content redirection request, in order to avoid
receiving content requests that it will not be able to satisfy/serve.

Property: metadata

Description: Array of path-related metadata.

Type: Array of GenericMetadata objects

Mandatory-to-Specify: Yes.

Property: paths

Type: Array of PathMatch objects

Mandatory-to-Specify: No. Default is that there are no
more-specific paths to evaluate (i.e., an empty list).

Example PathMetadata object containing a number of embedded
GenericMetadata objects that describe the metadata to apply for the
URI path defined in the parent PathMatch object, as well as a
more-specific PathMatch object.

{
"metadata": [
{
<Properties of first embedded GenericMetadata object>
},
{
<Properties of second embedded GenericMetadata object>
},

...

{
<Properties of Nth embedded GenericMetadata object>
}
],
"paths": [
{
<Properties of embedded PathMatch object>
}
]
}

4.1.7. GenericMetadata

A GenericMetadata object is a wrapper for managing individual CDNI
Metadata properties in an opaque manner.

Property: generic-metadata-type

Description: Case-insensitive CDNI Metadata object type.

Type: String containing the CDNI Payload Type [RFC7736] of the
object contained in the generic-metadata-value property (see
Table 4).

Mandatory-to-Specify: Yes.

Property: generic-metadata-value

Description: CDNI Metadata object.

Type: Format/Type is defined by the value of the
generic-metadata-type property above.
Note: generic-metadata-values MUST NOT name any properties
"href" (see Section 4.3.1).

Mandatory-to-Specify: Yes.

Property: mandatory-to-enforce

Description: Flag identifying whether or not the enforcement of
the property metadata is required.

Type: Boolean

Mandatory-to-Specify: No. Default is to treat metadata as
mandatory-to-enforce (i.e., a value of True).

Property: safe-to-redistribute

Description: Flag identifying whether or not the property
metadata can be safely redistributed without modification.

Type: Boolean

Mandatory-to-Specify: No. Default is to allow transparent
redistribution (i.e., a value of True).

Property: incomprehensible

Description: Flag identifying whether or not any CDN in the
chain of delegation has failed to understand and/or failed to
properly transform this metadata object. Note: This flag only
applies to metadata objects whose safe-to-redistribute property
has a value of False.

Type: Boolean

Mandatory-to-Specify: No. Default is comprehensible (i.e., a
value of False).

Example GenericMetadata object containing a metadata object that
applies to the applicable URI path and/or host (within a parent
PathMetadata and/or HostMetadata object, respectively):

{
"mandatory-to-enforce": true,
"safe-to-redistribute": true,
"incomprehensible": false,
"generic-metadata-type": <CDNI Payload Type of this metadata object>,
"generic-metadata-value":
{
<Properties of this metadata object>
}
}

4.2. Definitions of the Initial Set of CDNI GenericMetadata Objects

The objects defined below are intended to be used in the
GenericMetadata object's generic-metadata-value field as defined in
Section 4.1.7, and their generic-metadata-type property MUST be set
to the appropriate CDNI Payload Type as defined in Table 4.

4.2.1. SourceMetadata

Source metadata provides the dCDN with information about content
acquisition, i.e., how to contact a uCDN Surrogate or an origin
server to obtain the content to be served. The sources are not
necessarily the actual origin servers operated by the Content Service
Provider (CSP) but might be a set of Surrogates in the uCDN.

Property: sources

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

Type: Array of Source objects (see Section 4.2.1.1)

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

Example SourceMetadata object (which contains two Source objects)
that describes which servers the dCDN should use for acquiring
content for the applicable URI path and/or host:

{
"generic-metadata-type": "MI.SourceMetadata",
"generic-metadata-value":
{
"sources": [
{
"endpoints": [
"a.service123.ucdn.example",
"b.service123.ucdn.example"
],
"protocol": "http/1.1"
},
{
"endpoints": ["origin.service123.example"],
"protocol": "http/1.1"
}
]
}
}

4.2.1.1. Source

A Source object describes the source to 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 to be used when contacting that source.

Endpoints within a Source object MUST be treated as equivalent/equal.
A uCDN can specify an array of sources, ordered by preference, within
a SourceMetadata object. Then, for each Source object ranked by
preference, a uCDN can specify an array of endpoints that are
equivalent (e.g., a pool of servers that are not behind a load
balancer).

Property: acquisition-auth

Description: Authentication method to use when requesting
content from this source.

Type: Auth (see Section 4.2.7)

Mandatory-to-Specify: No. Default is no authentication
required.

Property: endpoints

Description: Origins from which the dCDN can acquire content.
If multiple endpoints are specified, they are all equal, i.e.,
the list is not ordered by preference.

Type: Array of Endpoint objects (see Section 4.3.3)

Mandatory-to-Specify: Yes.

Property: protocol

Description: Network retrieval protocol to use when requesting
content from this source.

Type: Protocol (see Section 4.3.2)

Mandatory-to-Specify: Yes.

Example Source object that describes a pair of endpoints (servers)
the dCDN can use for acquiring content for the applicable host and/or
URI path:

{
"endpoints": [
"a.service123.ucdn.example",
"b.service123.ucdn.example"
],
"protocol": "http/1.1"
}

4.2.2. LocationACL Metadata

LocationACL metadata defines which locations a User Agent needs to be
in, in order to be able to receive the associated content.

A LocationACL that does not include a "locations" property results in
an action of "allow all", meaning that delivery can be performed
regardless of the User Agent's location; otherwise, a CDN MUST take
the action from the first footprint to match against the User Agent's
location. If two or more footprints overlap, the first footprint
that matches against the User Agent's location determines the action
a CDN MUST take. If the "locations" property is included but is
empty or if none of the listed footprints match the User Agent's
location, then the result is an action of "deny".

Although the LocationACL, TimeWindowACL (see Section 4.2.3), and
ProtocolACL (see Section 4.2.4) are independent GenericMetadata
objects, they can provide conflicting information to a dCDN, e.g., a
content request that is simultaneously allowed based on the
LocationACL and denied based on the TimeWindowACL. The dCDN MUST use
the logical AND of all ACLs (where "allow" is true and "deny" is
false) to determine whether or not a request should be allowed.

Property: locations

Description: ACL that allows or denies (blocks) delivery based
on the User Agent's location.

Type: Array of LocationRule objects (see Section 4.2.2.1)

Mandatory-to-Specify: No. Default is to allow all locations.

Example LocationACL object that allows the dCDN to deliver content to
any location / IP address:

{
"generic-metadata-type": "MI.LocationACL",
"generic-metadata-value":
{
}
}

Example LocationACL object (which contains a LocationRule object that
in turn contains a Footprint object) that only allows the dCDN to
deliver content to User Agents in the USA:

{
"generic-metadata-type": "MI.LocationACL",
"generic-metadata-value":
{
"locations": [
{
"action": "allow",
"footprints": [
{
"footprint-type": "countrycode",
"footprint-value": ["us"]
}
]
}
]
}
}

4.2.2.1. LocationRule

A LocationRule contains or references an array of Footprint objects
and the corresponding action.

Property: footprints

Description: Array of footprints to which the rule applies.

Type: Array of Footprint objects (see Section 4.2.2.2)

Mandatory-to-Specify: Yes.

Property: action

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

Type: Enumeration [allow|deny] encoded as a lowercase string
Mandatory-to-Specify: No. Default is "deny".

Example LocationRule object (which contains a Footprint object) that
allows the dCDN to deliver content to clients in the USA:

{
"action": "allow",
"footprints": [
{
"footprint-type": "countrycode",
"footprint-value": ["us"]
}
]
}

4.2.2.2. Footprint

A Footprint object describes the footprint to which a LocationRule
can be applied, e.g., an IPv4 address range or a geographic location.

Property: footprint-type

Description: Registered footprint type (see Section 7.2). The
footprint types specified by this document are "ipv4cidr"
(IPv4CIDR; see Section 4.3.5), "ipv6cidr" (IPv6CIDR; see
Section 4.3.6), "asn" (Autonomous System Number; see
Section 4.3.7), and "countrycode" (Country Code; see
Section 4.3.8).

Type: Lowercase string

Mandatory-to-Specify: Yes.

Property: footprint-value

Description: Array of footprint values conforming to the
specification associated with the registered footprint type.
Footprint values can be simple strings (e.g., IPv4CIDR,
IPv6CIDR, ASN, and Country Code); however, other Footprint
objects can be defined in the future, along with a more complex
encoding (e.g., GPS coordinate tuples).

Type: Array of footprints

Mandatory-to-Specify: Yes.

Example Footprint object describing a footprint covering the USA:

{
"footprint-type": "countrycode",
"footprint-value": ["us"]
}

Example Footprint object describing a footprint covering the IP
address ranges 192.0.2.0/24 and 198.51.100.0/24:

{
"footprint-type": "ipv4cidr",
"footprint-value": ["192.0.2.0/24", "198.51.100.0/24"]
}

Example Footprint object describing a footprint covering the IP
address ranges 2001:db8::/32:

{
"footprint-type": "ipv6cidr",
"footprint-value": ["2001:db8::/32"]
}

Example Footprint object describing a footprint covering the
autonomous system 64496:

{
"footprint-type": "asn",
"footprint-value": ["as64496"]
}

4.2.3. TimeWindowACL

TimeWindowACL metadata defines time-based restrictions.

A TimeWindowACL that does not include a "times" property results in
an action of "allow all", meaning that delivery can be performed
regardless of the time of the User Agent's request; otherwise, a CDN
MUST take the action from the first window to match against the
current time. If two or more windows overlap, the first window that
matches against the current time determines the action a CDN MUST
take. If the "times" property is included but is empty or if none of
the listed windows match the current time, then the result is an
action of "deny".

Although the LocationACL (see Section 4.2.2), TimeWindowACL, and
ProtocolACL (see Section 4.2.4) are independent GenericMetadata
objects, they can provide conflicting information to a dCDN, e.g., a
content request that is simultaneously allowed based on the
LocationACL and denied based on the TimeWindowACL. The dCDN MUST use
the logical AND of all ACLs (where "allow" is true and "deny" is
false) to determine whether or not a request should be allowed.

Property: times

Description: ACL that allows or denies (blocks) delivery based
on the time of a User Agent's request.

Type: Array of TimeWindowRule objects (see Section 4.2.3.1)

Mandatory-to-Specify: No. Default is to allow all time
windows.

Example TimeWindowACL object (which contains a TimeWindowRule object
that in turn contains a TimeWindow object) that only allows the dCDN
to deliver content to clients between 09:00 01/01/2000 UTC and 17:00
01/01/2000 UTC:

{
"generic-metadata-type": "MI.TimeWindowACL",
"generic-metadata-value":
{
"times": [
{
"action": "allow",
"windows": [
{
"start": 946717200,
"end": 946746000
}
]
}
]
}
}

4.2.3.1. TimeWindowRule

A TimeWindowRule contains or references an array of TimeWindow
objects and the corresponding action.

Property: windows

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

Type: Array of TimeWindow objects (see Section 4.2.3.2)

Mandatory-to-Specify: Yes.

Property: action

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

Type: Enumeration [allow|deny] encoded as a lowercase string

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

Example TimeWindowRule object (which contains a TimeWindow object)
that only allows the dCDN to deliver content to clients between 09:00
01/01/2000 UTC and 17:00 01/01/2000 UTC:

{
"action": "allow",
"windows": [
{
"start": 946717200,
"end": 946746000
}
]
}

4.2.3.2. TimeWindow

A TimeWindow object describes a time range that can be applied by a
TimeWindowACL, e.g., start 946717200 (i.e., 09:00 01/01/2000 UTC),
end: 946746000 (i.e., 17:00 01/01/2000 UTC).

Property: start

Description: The start time of the window.

Type: Time (see Section 4.3.4)

Mandatory-to-Specify: Yes.

Property: end

Description: The end time of the window.

Type: Time (see Section 4.3.4)

Mandatory-to-Specify: Yes.

Example TimeWindow object that describes a time window from 09:00
01/01/2000 UTC to 17:00 01/01/2000 UTC:

{
"start": 946717200,
"end": 946746000
}

4.2.4. ProtocolACL Metadata

ProtocolACL metadata defines delivery protocol restrictions.

A ProtocolACL that does not include a protocol-acl property results
in an action of "allow all", meaning that delivery can be performed
regardless of the protocol in the User Agent's request; otherwise, a
CDN MUST take the action from the first protocol to match against the
request protocol. If two or more request protocols overlap, the
first protocol that matches the request protocol determines the
action a CDN MUST take. If the protocol-acl property is included but
is empty or if none of the listed protocols match the request
protocol, then the result is an action of "deny".

Although the LocationACL (see Section 4.2.2), TimeWindowACL (see
Section 4.2.3), and ProtocolACL are independent GenericMetadata
objects, they can provide conflicting information to a dCDN, e.g., a
content request that is simultaneously allowed based on the
ProtocolACL and denied based on the TimeWindowACL. The dCDN MUST use
the logical AND of all ACLs (where "allow" is true and "deny" is
false) to determine whether or not a request should be allowed.

Property: protocol-acl

Description: ACL that allows or denies (blocks) delivery based
on delivery protocol.

Type: Array of ProtocolRule objects (see Section 4.2.4.1)

Mandatory-to-Specify: No. Default is to allow all protocols.

Example ProtocolACL object (which contains a ProtocolRule object)
that only allows the dCDN to deliver content using HTTP/1.1:

{
"generic-metadata-type": "MI.ProtocolACL",
"generic-metadata-value":
{
"protocol-acl": [
{
"action": "allow",
"protocols": ["http/1.1"]
}
]
}
}

4.2.4.1. ProtocolRule

A ProtocolRule contains or references an array of Protocol objects
and the corresponding action.

Property: protocols

Description: Array of protocols to which the rule applies.

Type: Array of Protocol objects (see Section 4.3.2)

Mandatory-to-Specify: Yes.

Property: action

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

Type: Enumeration [allow|deny] encoded as a lowercase string

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

Example ProtocolRule object (which contains a Protocol object) that
allows the dCDN to deliver content using HTTP/1.1:

{
"action": "allow",
"protocols": ["http/1.1"]
}

4.2.5. DeliveryAuthorization Metadata

Delivery authorization defines authorization methods for the delivery
of content to User Agents.

Property: delivery-auth-methods

Description: Options for authorizing content requests.
Delivery for a content request is authorized if any one of the
authorization methods in the list is satisfied for that
request.

Type: Array of Auth objects (see Section 4.2.7)

Mandatory-to-Specify: No. Default is no authorization
required.

Example DeliveryAuthorization object (which contains an Auth object):

{
"generic-metadata-type": "MI.DeliveryAuthorization",
"generic-metadata-value":
{
"delivery-auth-methods": [
{
"auth-type": <CDNI Payload Type of this Auth object>,
"auth-value":
{
<Properties of this Auth object>
}
}
]
}
}

4.2.6. Cache

A Cache object describes the cache control parameters to be applied
to the content by intermediate caches.

Cache keys are generated from the URI of the content request
[RFC7234]. In some cases, a CDN or content provider might want
certain path segments or query parameters to be excluded from the
cache key generation. The Cache object provides guidance on what
parts of the path and query string to include.

Property: exclude-path-pattern

Description: A pattern for matching against the URI path, i.e.,
against the path-absolute [RFC3986]. The pattern can contain
the wildcards "*" and "?", where "*" matches any sequence of
pchar [RFC3986] or "/" characters (including the empty string)
and "?" matches exactly one pchar character. The three
literals "$", "*", and "?" MUST be escaped as "$$", "$*", and
"$?" (where "$" is the designated escape character). All other
characters are treated as literals. Cache key generation MUST
only include the portion of the path-absolute that matches the
wildcard portions of the pattern. Note: Inconsistency between
the PatternMatch pattern (Section 4.1.5) and the
exclude-path-pattern can result in inefficient caching.

Type: String

Mandatory-to-Specify: No. Default is to use the full URI
path-absolute to generate the cache key.

Property: include-query-strings

Description: Allows a Surrogate to specify the URI query string
parameters [RFC3986] to include when comparing the requested
URI against the URIs in its cache for equivalence. Matching
query parameters MUST be case insensitive. If all query
parameters should be ignored, then the list MUST be specified
and MUST be empty. If a query parameter appears multiple times
in the query string, each instance value MUST be aggregated
prior to comparison. For consistent cache key generation,
query parameters SHOULD be evaluated in the order specified in
this array.

Type: Array of strings

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

Example Cache object that instructs the dCDN to use the full URI path
and ignore all query parameters:

{
"generic-metadata-type": "MI.Cache",
"generic-metadata-value":
{
"include-query-strings": []
}
}

Example Cache object that instructs the dCDN to exclude the "CDNX"
path prefix and only include the (case-insensitive) query parameters
named "mediaid" and "providerid":

{
"generic-metadata-type": "MI.Cache",
"generic-metadata-value":
{
"exclude-path-pattern": "/CDNX/*",
"include-query-strings": ["mediaid", "providerid"]
}
}

Example Cache object that instructs the dCDN to exclude the "CDNX"
path prefix but includes all query parameters:

{
"generic-metadata-type": "MI.Cache",
"generic-metadata-value":
{
"exclude-path-pattern": "/CDNX/*"
}
}

4.2.7. Auth

An Auth object defines authentication and authorization methods to be
used during content acquisition and content delivery, respectively.

Note: This document does not define any Auth methods. Individual
Auth methods are being defined separately (e.g., URI Signing
[CDNI-URI-SIGNING]). The GenericMetadata object that contains Auth
objects is defined herein for convenience and so as not to be
specific to any particular Auth method.

Property: auth-type

Description: Auth type (The CDNI Payload Type [RFC7736] of the
GenericMetadata object contained in the auth-value property).

Type: String

Mandatory-to-Specify: Yes.

Property: auth-value

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

Type: GenericMetadata object

Mandatory-to-Specify: Yes.

Example Auth object:

{
"generic-metadata-type": "MI.Auth",
"generic-metadata-value":
{
"auth-type": <CDNI Payload Type of this Auth object>,
"auth-value":
{
<Properties of this Auth object>
}
}
}

4.2.8. Grouping

A Grouping object identifies a group of content to which a given
asset belongs.

Property: ccid

Description: Content Collection IDentifier for an application-
specific purpose such as logging aggregation.

Type: String

Mandatory-to-Specify: No. Default is not to apply any
grouping.

Example Grouping object that specifies a Content Collection
IDentifier for the content associated with the Grouping object's
parent HostMetadata and PathMetadata:

{
"generic-metadata-type": "MI.Grouping",
"generic-metadata-value":
{
"ccid": "ABCD"
}
}

4.3. CDNI Metadata Simple Data Type Descriptions

This section describes the simple data types that are used for
properties of CDNI Metadata objects.

4.3.1. Link

A Link object can be used in place of any of the objects described
above. Link objects can be used to avoid duplication if the same
metadata information is repeated within the metadata tree. When a
Link object replaces another object, its "href" property is set to
the URI of the resource and its "type" property is set to the CDNI
Payload Type of the object it is replacing.

dCDNs can detect the presence of a Link object by detecting the
presence of a property named "href" within the object. This means
that GenericMetadata types MUST NOT contain a property named "href"
because doing so would conflict with the ability for dCDNs to detect
Link objects being used to reference a GenericMetadata object.

Property: href

Description: The URI of the addressable object being
referenced.

Type: String

Mandatory-to-Specify: Yes.

Property: type

Description: The CDNI Payload Type of the object being
referenced.

Type: String

Mandatory-to-Specify: No. If the container specifies the type
(e.g., the HostIndex object contains an array of HostMatch
objects, so a Link object in the list of HostMatch objects must
reference a HostMatch), then it is not necessary to explicitly
specify a type.

Example Link object referencing a HostMatch object:

{
"type": "MI.HostMatch",
"href": "https://metadata.ucdn.example/hostmatch1234"
}

Example Link object referencing a HostMatch object, without an
explicit type, inside a HostIndex object:

{
"hosts": [
{
<Properties of embedded HostMatch object>
},
{
"href": "https://metadata.ucdn.example/hostmatch1234"
}
]
}

4.3.1.1. Link Loop Prevention

When following a link, CDNI Metadata clients SHOULD verify that the
CDNI Payload Type of the object retrieved matches the expected CDNI
Payload Type, as indicated by the Link object or containing property.
For GenericMetadata objects, type checks will prevent self-
references; however, incorrect linking can result in circular
references for structural metadata objects, specifically PathMatch
and PathMetadata objects (Figure 1). To prevent circular references,
CDNI Metadata clients SHOULD verify that no duplicate links occur for
PathMatch or PathMetadata objects.

4.3.2. Protocol

Protocol objects are used to specify protocols (from the "CDNI
Metadata Protocol Types" registry; see Section 7.3) for content
acquisition or delivery.

Type: String

Example:

"http/1.1"

4.3.3. Endpoint

A hostname (with optional port) or an IP address (with optional
port).

All implementations MUST support IPv4 addresses encoded as specified
by the "IPv4address" rule in Section 3.2.2 of [RFC3986]. IPv6
addresses MUST be encoded in one of the IPv6 address formats
specified in [RFC5952], although receivers MUST support all IPv6
address formats specified in [RFC4291]. Hostnames MUST conform to
the Domain Name System (DNS) syntax defined in [RFC1034] and
[RFC1123]. Internationalized Domain Names (IDNs) must first be
transformed to the A-label form [RFC5890] as per [RFC5891].

Type: String

Example hostname:

"metadata.ucdn.example"

Example IPv4 address:

"192.0.2.1"

Example IPv6 address (with port number):

"[2001:db8::1]:81"

4.3.4. Time

A time value expressed in seconds since the UNIX epoch (i.e., zero
hours, zero minutes, zero seconds, on January 1, 1970) Coordinated
Universal Time (UTC) [POSIX].

Type: Integer

Example time representing 09:00:00 01/01/2000 UTC:

946717200

4.3.5. IPv4CIDR

An IPv4address Classless Inter-Domain Routing (CIDR) block encoded as
specified by the "IPv4address" rule in Section 3.2.2 of [RFC3986]
followed by a "/" followed by an unsigned integer representing the
leading bits of the routing prefix (i.e., IPv4 CIDR notation).
Single IP addresses can be expressed as /32.

Type: String

Example IPv4CIDR:

"192.0.2.0/24"

4.3.6. IPv6CIDR

An IPv6address CIDR block encoded in one of the IPv6 address formats
specified in [RFC5952] followed by a "/" followed by an unsigned
integer representing the leading bits of the routing prefix (i.e.,
IPv6 CIDR notation). Single IP addresses can be expressed as /128.

Type: String
Example IPv6CIDR:

"2001:db8::/32"

4.3.7. ASN

An ASN value encoded as a string consisting of the characters "as"
(in lowercase) followed by the ASN [RFC6793].

Type: String

Example ASN:

"as64496"

4.3.8. CountryCode

An ISO 3166-1 alpha-2 code [ISO3166-1] in lowercase.

Type: String

Example Country Code representing the USA:

"us"

5. CDNI Metadata Capabilities

CDNI Metadata is used to convey information pertaining to content
delivery from the uCDN to the dCDN. For optional metadata, it can be
useful for the uCDN to know, prior to delegating any content requests
to a given dCDN, if that dCDN supports the underlying functionality
described by the metadata. If some metadata is mandatory-to-enforce
and the dCDN does not support it, any delegated requests for content
that requires that metadata will fail. The uCDN will likely want to
avoid delegating those requests to that dCDN. Likewise, for any
metadata that might be assigned optional values, it could be useful
for the uCDN to know, prior to delegating any content requests to a
given dCDN, which values that dCDN supports. If the optional value
assigned to a given piece of content's metadata is not supported by
the dCDN, any delegated requests for that content can fail, so again
the uCDN is likely to want to avoid delegating those requests to
that dCDN.

The CDNI Footprint & Capabilities Advertisement interface (FCI)
provides a means of advertising capabilities from the dCDN to the
uCDN [RFC8008]. Support for optional metadata types and values can
be advertised using the FCI.

6. CDNI Metadata Interface

This section specifies an interface to enable a dCDN to retrieve CDNI
Metadata objects from a uCDN.

The interface can be used by a dCDN to retrieve CDNI Metadata objects
in either of two ways:

o Dynamically, as required by the dCDN to process received requests
-- for example, in response to a query from a uCDN over the CDNI
Request Routing Redirection interface (RI) [RFC7975] or in
response to receiving a request for content from a User Agent.

o In advance of being required -- for example, in the case of
pre-positioned CDNI Metadata acquisition, initiated through the
"CDNI Control interface / Triggers" (CI/T) interface [RFC8007].

The CDNI Metadata interface is built on the principles of HTTP web
services. In particular, this means that requests and responses over
the interface are built around the transfer of representations of
hyperlinked resources. A resource in the context of the CDNI
Metadata interface is any object in the object model (as described in
Sections 3 and 4).

CDNI Metadata servers (i.e., servers in the uCDN) are free to assign
whatever structure they desire to the URIs for CDNI Metadata objects,
and CDNI Metadata clients MUST NOT make any assumptions regarding the
structure of CDNI Metadata URIs or the mapping between CDNI Metadata
objects and their associated URIs. Any URIs present in the examples
in this document are purely illustrative and are not intended to
impose a definitive structure on CDNI Metadata interface
implementations.

6.1. Transport

The CDNI Metadata interface uses HTTP as the underlying protocol
transport [RFC7230].

The HTTP method in the request defines the operation the request
would like to perform. A server implementation of the CDNI Metadata
interface MUST support the HTTP GET and HEAD methods.

The corresponding HTTP response returns the status of the operation
in the HTTP status code and returns the current representation of the
resource (if appropriate) in the response body. HTTP responses that
contain a response body SHOULD include an entity-tag (ETag) to enable
validation of cached versions of returned resources.

As the CDNI Metadata interface builds on top of HTTP, CDNI Metadata
server implementations MAY make use of any HTTP feature when
implementing the CDNI Metadata interface; for example, a CDNI
Metadata server MAY make use of HTTP's caching mechanisms to indicate
that the returned response/representation can be reused without
re-contacting the CDNI Metadata server.

6.2. Retrieval of CDNI Metadata Resources

In the general case, a CDNI Metadata server makes CDNI Metadata
objects available via unique URIs; thus, in order to retrieve CDNI
Metadata, a CDNI Metadata client (i.e., a client in the dCDN) first
makes an HTTP GET request for the URI of the HostIndex, which
provides an array of hostnames for which the uCDN can delegate
content delivery to the dCDN.

In order to retrieve the CDNI Metadata for a particular request, the
CDNI Metadata client processes the received HostIndex object and
finds the corresponding HostMetadata entry (by matching the hostname
in the request against the hostnames listed in the HostMatch
objects). If the HostMetadata is linked (rather than embedded), the
CDNI Metadata client then makes an HTTP GET request for the URI
specified in the "href" property of the Link object, which points to
the HostMetadata object itself.

In order to retrieve the most specific metadata for a particular
request, the CDNI Metadata client inspects the HostMetadata for
references to more-specific PathMetadata objects (by matching the URI
path in the request against the path-pattern property items in any
PathMatch objects listed in the HostMetadata object). If a
PathMetadata object is found to match (and is linked rather than
embedded), the CDNI Metadata client makes another HTTP GET request
for the PathMetadata. Each PathMetadata object can also include
references to additional more-specific metadata. If this is the
case, the CDNI Metadata client continues requesting PathMatch and
PathMetadata objects recursively. The CDNI Metadata client repeats
this approach of processing metadata objects and retrieving (via HTTP
GETs) any linked objects until it has all the metadata objects it
requires in order to process the redirection request from the uCDN or
the content request from a User Agent.

In cases where a dCDN is not able to retrieve the entire set of CDNI
Metadata associated with a User Agent request, or it has retrieved
that metadata but it is stale according to standard HTTP caching
rules and cannot be revalidated -- for example, because the uCDN is
unreachable or returns an HTTP 4xx or 5xx status in response to some
or all of the dCDN's CDNI Metadata requests -- the dCDN MUST NOT
serve the requested content.

Where a dCDN is interconnected with multiple uCDNs, the dCDN needs to
determine which uCDN's CDNI Metadata interface should be used to
handle a particular User Agent request.

When HTTP redirection (e.g., HTTP 302 redirects) is being used
between CDNs, it is expected that the dCDN will be able to determine
the uCDN that redirected a particular request from information
contained in the received request (e.g., via the URI). With
knowledge of which uCDN routed the request, the dCDN can choose the
correct uCDN from which to obtain the HostIndex. Note that the
HostIndexes served by each uCDN can be unique.

In the case of DNS redirection, there is not always sufficient
information carried in the DNS request from User Agents to determine
the uCDN that redirected a particular request (e.g., when content
from a given host is redirected to a given dCDN by more than one
uCDN); therefore, dCDNs will have to apply local policy when deciding
which uCDN's CDNI Metadata interface to use.

6.3. Bootstrapping

The URI for the HostIndex object of a given uCDN needs to be
configured in the dCDN. All other objects/resources are then
discoverable from the HostIndex object by following any links in the
HostIndex object, and through the referenced HostMetadata and
PathMetadata objects and their GenericMetadata sub-objects.

Manual configuration of the URI for the HostIndex object is outside
the scope of this document.

6.4. Encoding

CDNI Metadata objects MUST be encoded as I-JSON objects [RFC7493]
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 CDNI Payload Type of the
returned resource). Likewise, the values associated with each
property (dictionary key) are dependent on the specific object being
encoded (i.e., dependent on the CDNI Payload Type of the returned
resource).

Dictionary keys (properties) in I-JSON are case sensitive. By
convention, any dictionary key (property) defined by this document
(for example, the names of CDNI Metadata object properties) MUST be
lowercase.

6.5. Extensibility

The set of GenericMetadata objects can be extended with additional
(standards-based or vendor-specific) metadata objects through the
specification of new GenericMetadata objects. The GenericMetadata
object defined in Section 4.1.7 specifies a type field and a type-
specific value field that allow any metadata to be included in either
the HostMetadata or PathMetadata arrays.

As with the initial GenericMetadata types defined in Section 4.2,
future GenericMetadata types MUST specify the information necessary
for constructing and decoding the GenericMetadata object.

Any document that defines a new GenericMetadata type MUST:

1. Register the CDNI Payload Type [RFC7736] used to identify the new
GenericMetadata type being specified.

2. Define the set of properties associated with the new
GenericMetadata object. GenericMetadata MUST NOT contain a
property named "href" because doing so would conflict with the
ability to detect Link objects (see Section 4.3.1).

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

4. Describe the semantics of the new type, including its purpose,
and provide a use case to which it applies, including an example
encoded in I-JSON.

5. Describe the security and privacy consequences, for both the User
Agent and the CDNs, of the new GenericMetadata object.

6. Describe any relation to, conflict with, or obsolescence of other
existing CDNI Metadata objects.

Note: In the case of vendor-specific extensions, vendor-identifying
CDNI Payload Type names will decrease the possibility of
GenericMetadata type collisions. It is RECOMMENDED that any
vendor-specific extensions use vendor-identifying CDNI Payload Type
names.

6.6. Metadata Enforcement

At any given time, the set of GenericMetadata types supported by the
uCDN might not match the set of GenericMetadata types supported by
the dCDN.

In cases where a uCDN sends metadata containing a GenericMetadata
type that a dCDN does not support, the dCDN MUST enforce the
semantics of the mandatory-to-enforce property. If a dCDN does not
understand or is unable to perform the functions associated with any
mandatory-to-enforce metadata, the dCDN MUST NOT service any requests
for the corresponding content.

Note: Ideally, uCDNs would not delegate content requests to a dCDN
that does not support the mandatory-to-enforce metadata associated
with the content being requested. However, even if the uCDN has
a priori knowledge of the metadata supported by the dCDN (e.g., via
the FCI or through out-of-band negotiation between CDN operators),
metadata support can fluctuate or be inconsistent (e.g., due to
miscommunication, misconfiguration, or temporary outage). Thus, the
dCDN MUST always evaluate all metadata associated with redirection
and content requests and reject any requests where
mandatory-to-enforce metadata associated with the content cannot be
enforced.

6.7. Metadata Conflicts

It is possible that new metadata definitions will obsolete or
conflict with existing GenericMetadata (e.g., a future revision of
the CDNI Metadata interface could redefine the Auth GenericMetadata
object or a custom vendor extension could implement an alternate Auth
metadata option). If multiple metadata (e.g., MI.Auth.v2,
vendor1.Auth, and vendor2.Auth) all conflict with an existing
GenericMetadata object (i.e., MI.Auth) and all are marked as
mandatory-to-enforce, it could be ambiguous as to which metadata
should be applied, especially in the case of overlapping
functionality.

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 GenericMetadata
types. It is the responsibility of the CSP and the CDN operators to
ensure that metadata assigned to a given piece of content do not
conflict.

Note: Because metadata is inherently ordered in HostMetadata and
PathMetadata arrays, as well as in the PathMatch hierarchy, multiple
conflicting metadata types MAY be used; however, metadata hierarchies
SHOULD ensure that independent PathMatch root objects are used to
prevent ambiguous or conflicting metadata definitions.

6.8. Versioning

The version of CDNI Metadata objects is conveyed inside the CDNI
Payload Type that is included in either (1) the HTTP Content-Type
header (for example, "Content-Type: application/cdni;
ptype=MI.HostIndex" when retrieved via a link) or (2) in the link
type (Section 4.3.1), generic-metadata-type (Section 4.1.7), or
auth-type (Section 4.2.7) properties in the JSON payload. The CDNI
Payload Type uniquely identifies the specification defining that
object, including any relation to, conflicts with, or obsolescence of
other metadata. There is no explicit version mapping requirement;
however, for ease of understanding, metadata creators SHOULD make new
versions of metadata easily visible via the CDNI Payload Type, e.g.,
by appending a version string. Note: A version string is optional on
the first version (e.g., MI.HostIndex) but could be added for
subsequent versions (MI.HostIndex.v2, MI.HostIndex.v3, etc.).

Except when referenced by a Link object, nested metadata objects
(i.e., structural metadata below the HostIndex; and Source,
LocationRule, TimeWindowRule, ProtocolRule, Footprint, and TimeWindow
objects) can be serialized into a JSON payload without explicit CDNI
Payload Type information. The type is inferred from the outer
structural metadata, GenericMetadata, or Auth object CDNI Payload
Type. To avoid ambiguity when revising nestable metadata objects,
any outer metadata object(s) MUST be reversioned and allocated new
CDNI Payload Type(s) at the same time. For example, the MI.HostIndex
object defined in this document contains an array of MI.HostMatch
objects, each of which in turn contains a MI.HostMetadata object. If
a new MI.HostMetadata.v2 object were required, the outer MI.HostIndex
and MI.HostMatch objects would need to be revised, e.g., to
MI.HostIndex.v2 and MI.HostMatch.v2, respectively. Similarly, if a
new MI.TimeWindowRule.v2 object were required, the outer
MI.TimeWindowACL object would need to be revised, e.g., to
MI.TimeWindowACL.v2; however, the MI.TimeWindowRule.v2 object could
still contain MI.TimeWindow objects, if so specified.

HTTP requests sent to a metadata server SHOULD include an Accept
header with the CDNI Payload Type of the expected object. Metadata
clients can specify multiple CDNI Payload Types in the Accept header;
for example, if a metadata client is capable of processing two
different versions of the same type of object (defined by different
CDNI Payload Types), it might decide to include both in the Accept
header.

6.9. Media Types

All CDNI Metadata objects use the media type "application/cdni". The
CDNI Payload Type for each object then contains the object name of
that object as defined by this document, prefixed with "MI.".
Table 4 lists the CDNI Payload Types for the metadata objects
(resources) specified in this document.

Table 4: CDNI Payload Types for CDNI Metadata Objects

6.10. Complete CDNI Metadata Example

A dCDN requests the HostIndex and receives the following object with
a CDNI Payload Type of "MI.HostIndex":

{
"hosts": [
{
"host": "video.example.com",
"host-metadata": {
"type": "MI.HostMetadata",
"href": "https://metadata.ucdn.example/host1234"
}
},
{
"host": "images.example.com",
"host-metadata": {
"type": "MI.HostMetadata",
"href": "https://metadata.ucdn.example/host5678"
}
}
]
}

If the incoming request has a Host header with "video.example.com",
then the dCDN would fetch the HostMetadata object from
"https://metadata.ucdn.example/host1234" expecting a CDNI Payload
Type of "MI.HostMetadata":

{
"metadata": [
{
"generic-metadata-type": "MI.SourceMetadata",
"generic-metadata-value": {
"sources": [
{
"endpoint": ["acq1.ucdn.example"],
"protocol": "http/1.1"
},
{
"endpoint": ["acq2.ucdn.example"],
"protocol": "http/1.1"
}
]
}
},
{
"generic-metadata-type": "MI.LocationACL",
"generic-metadata-value": {
"locations": [
{
"footprints": [
{
"footprint-type": "ipv4cidr",
"footprint-value": ["192.0.2.0/24"]
},
{
"footprint-type": "ipv6cidr",
"footprint-value": ["2001:db8::/32"]
},
{
"footprint-type": "countrycode",
"footprint-value": ["us"]
},
{
"footprint-type": "asn",
"footprint-value": ["as64496"]
}
],
"action": "deny"
}
]
}
},
{
"generic-metadata-type": "MI.ProtocolACL",
"generic-metadata-value": {
"protocol-acl": [
{
"protocols": [
"http/1.1"
],
"action": "allow"
}
]
}
}
],
"paths": [
{
"path-pattern": {
"pattern": "/videos/trailers/*"
},
"path-metadata": {
"type": "MI.PathMetadata",
"href": "https://metadata.ucdn.example/host1234/pathABC"
}
},
{
"path-pattern": {
"pattern": "/videos/movies/*"
},
"path-metadata": {
"type": "MI.PathMetadata",
"href": "https://metadata.ucdn.example/host1234/pathDEF"
}
}
]
}

Suppose that the path of the requested resource matches the
"/videos/movies/*" pattern; the next metadata requested would be for
"https://metadata.ucdn.example/host1234/pathDEF" with an expected
CDNI Payload Type of "MI.PathMetadata":

{
"metadata": [],
"paths": [
{
"path-pattern": {
"pattern": "/videos/movies/hd/*"
},
"path-metadata": {
"type": "MI.PathMetadata",
"href":
"https://metadata.ucdn.example/host1234/pathDEF/path123"
}
}
]
}

Finally, if the path of the requested resource also matches the
"/videos/movies/hd/*" pattern, the dCDN would also fetch the
following object from
"https://metadata.ucdn.example/host1234/pathDEF/path123" with a CDNI
Payload Type of "MI.PathMetadata":

{
"metadata": [
{
"generic-metadata-type": "MI.TimeWindowACL",
"generic-metadata-value": {
"times": [
"windows": [
{
"start": "1213948800",
"end": "1478047392"
}
],
"action": "allow"
]
}
}
]
}

The final set of metadata that applies to the requested resource
includes a SourceMetadata, a LocationACL, a ProtocolACL, and a
TimeWindowACL.

7. IANA Considerations

7.1. CDNI Payload Types

This document requests the registration of the following entries
under the "CDNI Payload Types" registry hosted by IANA:

+--------------------------+---------------+
| Payload Type | Specification |
+--------------------------+---------------+
| MI.HostIndex | RFC 8006 |
| MI.HostMatch | RFC 8006 |
| MI.HostMetadata | RFC 8006 |
| MI.PathMatch | RFC 8006 |
| MI.PatternMatch | RFC 8006 |
| MI.PathMetadata | RFC 8006 |
| MI.SourceMetadata | RFC 8006 |
| MI.Source | RFC 8006 |
| MI.LocationACL | RFC 8006 |
| MI.LocationRule | RFC 8006 |
| MI.Footprint | RFC 8006 |
| MI.TimeWindowACL | RFC 8006 |
| MI.TimeWindowRule | RFC 8006 |
| MI.TimeWindow | RFC 8006 |
| MI.ProtocolACL | RFC 8006 |
| MI.ProtocolRule | RFC 8006 |
| MI.DeliveryAuthorization | RFC 8006 |
| MI.Cache | RFC 8006 |
| MI.Auth | RFC 8006 |
| MI.Grouping | RFC 8006 |
+--------------------------+---------------+

7.1.1. CDNI MI HostIndex Payload Type

Purpose: The purpose of this Payload Type is to distinguish HostIndex
MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.1.1

7.1.2. CDNI MI HostMatch Payload Type

Purpose: The purpose of this Payload Type is to distinguish HostMatch
MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.1.2

7.1.3. CDNI MI HostMetadata Payload Type

Purpose: The purpose of this Payload Type is to distinguish
HostMetadata MI objects (and any associated capability advertisement)
Interface: MI/FCI

Encoding: see Section 4.1.3

7.1.4. CDNI MI PathMatch Payload Type

Purpose: The purpose of this Payload Type is to distinguish PathMatch
MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.1.4

7.1.5. CDNI MI PatternMatch Payload Type

Purpose: The purpose of this Payload Type is to distinguish
PatternMatch MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.1.5

7.1.6. CDNI MI PathMetadata Payload Type

Purpose: The purpose of this Payload Type is to distinguish
PathMetadata MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.1.6

7.1.7. CDNI MI SourceMetadata Payload Type

Purpose: The purpose of this Payload Type is to distinguish
SourceMetadata MI objects (and any associated capability
advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.1

7.1.8. CDNI MI Source Payload Type

Purpose: The purpose of this Payload Type is to distinguish Source MI
objects (and any associated capability advertisement)

Interface: MI/FCI
Encoding: see Section 4.2.1.1

7.1.9. CDNI MI LocationACL Payload Type

Purpose: The purpose of this Payload Type is to distinguish
LocationACL MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.2

7.1.10. CDNI MI LocationRule Payload Type

Purpose: The purpose of this Payload Type is to distinguish
LocationRule MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.2.1

7.1.11. CDNI MI Footprint Payload Type

Purpose: The purpose of this Payload Type is to distinguish Footprint
MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.2.2

7.1.12. CDNI MI TimeWindowACL Payload Type

Purpose: The purpose of this Payload Type is to distinguish
TimeWindowACL MI objects (and any associated capability
advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.3

7.1.13. CDNI MI TimeWindowRule Payload Type

Purpose: The purpose of this Payload Type is to distinguish
TimeWindowRule MI objects (and any associated capability
advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.3.1

7.1.14. CDNI MI TimeWindow Payload Type

Purpose: The purpose of this Payload Type is to distinguish
TimeWindow MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.3.2

7.1.15. CDNI MI ProtocolACL Payload Type

Purpose: The purpose of this Payload Type is to distinguish
ProtocolACL MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.4

7.1.16. CDNI MI ProtocolRule Payload Type

Purpose: The purpose of this Payload Type is to distinguish
ProtocolRule MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.4.1

7.1.17. CDNI MI DeliveryAuthorization Payload Type

Purpose: The purpose of this Payload Type is to distinguish
DeliveryAuthorization MI objects (and any associated capability
advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.5

7.1.18. CDNI MI Cache Payload Type

Purpose: The purpose of this Payload Type is to distinguish Cache MI
objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.6

7.1.19. CDNI MI Auth Payload Type

Purpose: The purpose of this Payload Type is to distinguish Auth MI
objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.7

7.1.20. CDNI MI Grouping Payload Type

Purpose: The purpose of this Payload Type is to distinguish Grouping
MI objects (and any associated capability advertisement)

Interface: MI/FCI

Encoding: see Section 4.2.8

7.2. "CDNI Metadata Footprint Types" Registry

IANA has created a new "CDNI Metadata Footprint Types" subregistry in
the "Content Delivery Network Interconnection (CDNI) Parameters"
registry. The "CDNI Metadata Footprint Types" namespace defines the
valid Footprint object type values used by the Footprint object
described in Section 4.2.2.2. Additions to the "CDNI Metadata
Footprint Types" namespace conform to the Specification Required
policy as defined in [RFC5226]. The Designated Expert will verify
that new type definitions do not duplicate existing type definitions
and prevent gratuitous additions to the namespace. New registrations
are required to provide a clear description of how to interpret new
footprint types.

The following table defines the initial values for the "CDNI Metadata
Footprint Types" registry:

+----------------+--------------------------------+---------------+
| Footprint Type | Description | Specification |
+----------------+--------------------------------+---------------+
| ipv4cidr | IPv4 CIDR address block | RFC 8006 |
| ipv6cidr | IPv6 CIDR address block | RFC 8006 |
| asn | Autonomous System Number (ASN) | RFC 8006 |
| countrycode | ISO 3166-1 alpha-2 code | RFC 8006 |
+----------------+--------------------------------+---------------+

7.3. "CDNI Metadata Protocol Types" Registry

IANA has created a new "CDNI Metadata Protocol Types" subregistry in
the "Content Delivery Network Interconnection (CDNI) Parameters"
registry. The "CDNI Metadata Protocol Types" namespace defines the
valid Protocol object values (Section 4.3.2) used by the
SourceMetadata and ProtocolACL objects. Additions to the Protocol
namespace conform to the Specification Required policy as defined in
[RFC5226], where the specification defines the Protocol Type and the
protocol to which it is associated. The Designated Expert will
verify that new protocol definitions do not duplicate existing
protocol definitions and prevent gratuitous additions to the
namespace.

The following table defines the initial Protocol values corresponding
to the HTTP and HTTPS protocols:

8. Security Considerations

8.1. Authentication and Integrity

A malicious metadata server, proxy server, or attacker impersonating
an authentic uCDN CDNI Metadata interface without being detected
could provide false metadata to a dCDN that either:

o Denies service for one or more pieces of content to one or more
User Agents;

o Directs dCDNs to contact malicious origin servers instead of the
actual origin servers, so that malware or slanderous alternate
content may be substituted for legitimate content; or

o Removes delivery restrictions (e.g., LocationACL, TimeWindowACL,
ProtocolACL, or Auth metadata), allowing access to content that
would otherwise be denied and thus possibly violating license
restrictions and incurring unwarranted delivery costs.

Unauthorized access to metadata could also enable a malicious
metadata client to continuously issue metadata requests in order to
overload a uCDN's metadata server or servers.

Unauthorized access to metadata could further result in leakage of
private information. A malicious metadata client could request
metadata in order to gain access to origin servers, as well as
information pertaining to content restrictions.

An implementation of the CDNI Metadata interface MUST use mutual
authentication and message authentication codes to prevent
unauthorized access to, and undetected modification of, metadata (see
Section 8.3).

8.2. Confidentiality and Privacy

Unauthorized viewing of metadata could result in leakage of private
information. Content provider origin and policy information is
conveyed through the CDNI Metadata interface. A third party could
intercept metadata transactions in order to gain access to origin
servers, as well as information pertaining to content restrictions
and usage patterns.

Note: The distribution of metadata by a uCDN to dCDNs could introduce
privacy concerns for some content providers, e.g., dCDNs accepting
content requests for a content provider's content might be able to
obtain additional information and usage patterns relating to the
users of a content provider's services. Content providers with
concerns about divulging information to dCDNs can instruct their uCDN
partners not to use CDNI when delivering their content.

An implementation of the CDNI Metadata interface MUST use strong
encryption to prevent unauthorized interception or monitoring of
metadata (see Section 8.3).

8.3. Securing the CDNI Metadata Interface

An implementation of the CDNI Metadata interface MUST support TLS
transport as per [RFC2818] and [RFC7230].

TLS MUST be used by the server side (uCDN) and the client side (dCDN)
of the CDNI Metadata interface, including authentication of the
remote end, unless alternate methods are used for ensuring the
security of the information in the CDNI Metadata interface requests
and responses (such as setting up an IPsec tunnel between the two
CDNs or using a physically secured internal network between two CDNs
that are owned by the same corporate entity).

The use of TLS for transport of the CDNI Metadata interface messages
allows the dCDN and uCDN to authenticate each other.

Once the dCDN and uCDN have mutually authenticated each other, TLS
allows:

o The dCDN and uCDN to authorize each other (to ensure that they are
transmitting/receiving CDNI Metadata requests and responses from
an authorized CDN);

o CDNI Metadata interface requests and responses to be transmitted
with confidentiality; and

o The integrity of the CDNI Metadata interface requests and
responses to be protected during the exchange.

When TLS is used, the general TLS usage guidance in [RFC7525] MUST be
followed.

9. References

9.1. Normative References

[ISO3166-1]
The International Organization for Standardization, "Codes
for the representation of names of countries and their
subdivisions -- Part 1: Country codes", ISO 3166-1:2013,
2013.

[POSIX] Institute of Electrical and Electronics Engineers,
"Information Technology Portable Operating System
Interface (POSIX) Part 1: System Application Program
Interface (API) [C Language]", IEEE P1003.1, 1990.

[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>.

[RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123,
DOI 10.17487/RFC1123, October 1989,
<http://www.rfc-editor.org/info/rfc1123>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.

[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.

[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.

[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010,
<http://www.rfc-editor.org/info/rfc5890>.

[RFC5891] Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891,
DOI 10.17487/RFC5891, August 2010,
<http://www.rfc-editor.org/info/rfc5891>.

[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952,
DOI 10.17487/RFC5952, August 2010,
<http://www.rfc-editor.org/info/rfc5952>.

[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, DOI 10.17487/RFC6707, September
2012, <http://www.rfc-editor.org/info/rfc6707>.

[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.

[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015,
<http://www.rfc-editor.org/info/rfc7493>.

[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.

9.2. Informative References

[CDNI-URI-SIGNING]
van Brandenburg, R., Leung, K., Sorber, P., and M. Miller,
"URI Signing for CDN Interconnection (CDNI)", Work in
Progress, draft-ietf-cdni-uri-signing-10, October 2016.

[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>.

[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793,
DOI 10.17487/RFC6793, December 2012,
<http://www.rfc-editor.org/info/rfc6793>.

[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014,
<http://www.rfc-editor.org/info/rfc7234>.

[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
"Framework for Content Distribution Network
Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
August 2014, <http://www.rfc-editor.org/info/rfc7336>.

[RFC7337] Leung, K., Ed. and Y. Lee, Ed., "Content Distribution
Network Interconnection (CDNI) Requirements", RFC 7337,
DOI 10.17487/RFC7337, August 2014,
<http://www.rfc-editor.org/info/rfc7337>.

[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.

[RFC7736] Ma, K., "Content Delivery Network Interconnection (CDNI)
Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
December 2015, <http://www.rfc-editor.org/info/rfc7736>.

[RFC7975] Niven-Jenkins, B., Ed. and R. van Brandenburg, Ed.,
"Request Routing Redirection Interface for Content
Delivery Network (CDN) Interconnection", RFC 7975,
DOI 10.17487/RFC7975, October 2016,
<http://www.rfc-editor.org/info/rfc7975>.

[RFC8007] Murray, R. and B. Niven-Jenkins, "Content Delivery Network
Interconnection (CDNI) Control Interface / Triggers",
RFC 8007, DOI 10.17487/RFC8007, November 2016,
<http://www.rfc-editor.org/info/rfc8007>.

[RFC8008] Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
R., and K. Ma, "Content Delivery Network Interconnection
(CDNI) Request Routing: Footprint and Capabilities
Semantics", RFC 8008, DOI 10.17487/RFC8008, November 2016,
<http://www.rfc-editor.org/info/rfc8008>.

Acknowledgments

The authors would like to thank David Ferguson, Francois Le Faucheur,
Jan Seedorf, and Matt Miller for their valuable comments and input to
this document.

Contributors

The authors would also like to thank Grant Watson and Kent Leung for
their contributions to this document.

Authors' Addresses

Ben Niven-Jenkins
Nokia
3 Ely Road
Milton, Cambridge CB24 6DD
United Kingdom

Email: ben.niven-jenkins@nokia.com

Rob Murray
Velocix (Alcatel-Lucent)
Nokia
3 Ely Road
Milton, Cambridge CB24 6AA 6DD
United Kingdom

Email: rmurray@velocix.com rob.murray@nokia.com
Matt Caulfield
Cisco Systems
1414 Massachusetts Avenue
Boxborough, MA 01719
United States of America

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

Kevin J. Ma
Ericsson
43 Nagog Park
Acton, MA 01720
United States of America

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