RFC 8006
Content Delivery Network Interconnection (CDNI) Metadata
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
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.
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
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 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: 9467172004.3.5. 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. Country Code
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.
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