CDN Interconnection Metadata

Content Delivery Networks Interconnection (CDNI) enables a downstream Content Delivery Network (dCDN) to service content requests on behalf of an upstream CDN (uCDN). The CDNI metadata interface is discussed in along with four other interfaces that can be used to compose a CDNI solution (CDNI Control interface, CDNI Request Routing Redirection interface, CDNI Footprint & Capabilities Advertisement interface and CDNI Logging interface). describes each interface and the relationships between them. The requirements for the CDNI metadata interface are specified in . 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 an uCDN, in accordance with the policies defined by the uCDN. This document defines the CDNI metadata interface which enables a dCDN to obtain CDNI metadata from an uCDN so that the dCDN can properly process and respond to: Redirection requests received over the CDNI Request Routing Redirection interface . Content requests received directly from User Agents. Specifically, this document specifies: A data structure for mapping content requests and redirection requests to CDNI metadata objects ( and ). An initial set of CDNI Generic metadata objects (). A HTTP web service for the transfer of CDNI metadata ().

This document reuses the terminology defined in . Additionally, the following terms are used throughout this document and are defined as follows: Object - a collection of properties. 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".

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 . The following high-level functionality can be configured via the CDNI metadata objects specified in : Acquisition Source: Metadata for allowing a dCDN to fetch content from a uCDN. Delivery Access Control: Metadata for restricting (or permitting) access to content based on any of the following factors: Location Time Window Delivery Protocol Delivery Authorization: Metadata for authorizing dCDN user agent requests. 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 CDN interconnection for the delivery of content by a dCDN using HTTP/1.1 and for a dCDN to be able to acquire content from a uCDN using either HTTP/1.1 or HTTP/1.1 over TLS . Supporting CDN interconnection for the delivery of content using unencrypted HTTP/2 (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 . Delivery of content using HTTP/1.1 over TLS or HTTP/2 over TLS SHOULD follow the guidelines set forth in . Offline configuration of TLS parameters between CDNs is beyond the scope of this document.

The CDNI metadata interface was designed to achieve the following objectives: Cacheability of CDNI metadata objects; Deterministic mapping from redirection requests and content requests to CDNI metadata properties; Support for DNS redirection as well as application-specific redirection (for example HTTP redirection); Minimal duplication of CDNI metadata; and Leveraging of existing protocols. Cacheability can decrease the latency of acquiring metadata while maintaining its freshness, and 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 mappings 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 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 ) and data transport (by leveraging HTTP ).

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 an 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 behaviour 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 Hostname 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. introduces a high level description of the HostIndex, HostMatch, HostMetadata, PathMatch, PatternMatch and PathMetadata objects, and describes the relationships between them. 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. describes in detail the specific CDNI metadata objects and properties specified by this document which can be contained within a CDNI GenericMetadata object.

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

|HostMatch+-(1)->|HostMetadata+-------(*)------+ +---------+ +---------+ +------+-----+ | | | (*) | | V --> Contains or References V ****************** (1) One and only one +---------+ *Generic Metadata* (*) Zero or more +--->|PathMatch| * Objects * | +----+---++ ****************** | | | ^ (*) (1) (1) +------------+ | | | +->|PatternMatch| | | V +------------+ | | +------------+ | +--+PathMetadata+-------(*)------+ +------------+ ]]> A HostIndex object (see ) contains an array of HostMatch objects (see ) 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 ) 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 ) 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 ), via PathMatch objects (see ). PathMatch objects define patterns, contained inside PatternMatch objects (see ), to match against the requested URI path. PatternMatch objects contain the pattern strings and flags that describe the URI path that a PathMatch applies to. 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 which 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 which 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 which 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 are also represented in tabular format in below. Data Object Objects it contains or references HostIndex 0 or more HostMatch objects. HostMatch 1 HostMetadata object. HostMetadata 0 or more PathMatch objects. 0 or more GenericMetadata objects. PathMatch 1 PatternMatch object. 1 PathMetadata object. PatternMatch Does not contain or reference any other objects. PathMetadata 0 or more PathMatch objects. 0 or more GenericMetadata objects.

The HostMetadata and PathMetadata objects contain other CDNI metadata objects that contain properties which describe how User Agent requests for content should be processed, for example where to acquire the content 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 to another CDN without modification. For example, in the cascaded CDN case, a transit CDN (tCDN) could pass through "mandatory-to-enforce" metadata to a dCDN. For metadata which 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 transit CDN. However, for metadata which 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, 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 transit CDN. A CDN MUST NOT attempt to use metadata that has been marked as "incomprehensible" by a uCDN. Transit CDNs MUST NOT change the value of "mandatory-to-enforce" or "safe-to-redistribute" when propagating metadata to a dCDN. Although a transit CDN can set the value of "incomprehensible" to true, a transit CDN MUST NOT change the value of "incomprehensible" from true to false. describes the action to be taken by a transit CDN (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: MtE StR Metadata Understood by tCDN Action False True True Can serve and redistribute. False True False Can serve and redistribute. False False False Can serve. MUST set "incomprehensible" to True when redistributing. False False True Can serve. Can redistribute after transforming the metadata (if the CDN knows how to do so safely), otherwise MUST set "incomprehensible" to True when redistributing. True True True Can serve and redistribute. True True False MUST NOT serve but can redistribute. True False True Can serve. Can redistribute after transforming the metadata (if the CDN knows how to do so safely), otherwise MUST set "incomprehensible" to True when redistributing. True False False MUST NOT serve. MUST set "incomprehensible" to True when redistributing. describes the action to be taken by a dCDN for the different combinations of "mandatory-to-enforce" (MtE) and "incomprehensible" (Incomp) properties, when the dCDN either does or does not understand the metadata in question: MtE Incomp Metadata Understood by dCDN Action False False True Can serve. False True True Can serve but MUST NOT interpret/apply any metadata marked incomprehensible. False False False Can serve. False True False Can serve but MUST NOT interpret/apply any metadata marked incomprehensible. True False True Can serve. True True True MUST NOT serve. True False False MUST NOT serve. True True False MUST NOT serve.

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 type LocationACL and TimeWindowACL, while a PathMetadata object which applies to "example.com/movies/*" defines an alternate GenericMetadata object of type TimeWindowACL, then: the TimeWindowACL defined in the PathMetadata would override the TimeWindowACL defined in the HostMetadata for all User Agent requests for content under "example.com/movies/", and 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.

provides the definitions of each metadata object type introduced in . 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. provides the definitions for a base set of core metadata objects which 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 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. 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 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 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, e.g., 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.

Each of the sub-sections below describe the structural objects introduced in .

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 which 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:

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

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. 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 . IPv6 addresses MUST be encoded in one of the IPv6 address formats specified in although receivers MUST support all IPv6 address formats specified in . Hostnames MUST conform to the Domain Name System (DNS) syntax defined in and . Internationalized Domain Names (IDN) must first be transformed to the IDNA encoding as per . 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:

} } ]]> Example HostMatch object referencing (via a Link object, see ) a HostMetadata object:

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. 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:

}, { }, ... { } ], "paths": [ { } ] }]]>

A PathMatch object contains PatternMatch object with a path to match against a resource's URI path, as well as a PathMetadata object with GenericMetadata to apply if the resource's URI path matches the pattern within the PatternMatch object. Property: path-pattern Description: Pattern to match against the requested resource's URI path, i.e., against the path-absolute. 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):

A PatternMatch object contains the pattern string and flags that describe the pattern expression. Property: pattern Description: A pattern for string matching. The pattern can contain the wildcards * and ?, where * matches any sequence of characters (including the empty string) and ? matches exactly one character. The three literals $, * and ? should be escaped as $$, $* and $? (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 . Type: Boolean Mandatory-to-Specify: No. Default is case-insensitive match. Property: ignore-query-string Description: Array of query parameters which should be ignored when searching for a pattern match. Matching against query parameters to ignore MUST be case-insensitive. If all query parameters should be ignored then the list MUST be empty. Type: Array of String Mandatory-to-Specify: No. Default is to include query strings when matching. Example PatternMatch object that matches the case-sensitive URI path pattern "/movies/*". All query parameters will be ignored when matching URIs requested from surrogates by content clients against this path pattern:

Example PatternMatch object that matches the case-sensitive URI path pattern "/movies/*". The query parameter "sessionid" will be ignored when matching URIs requested from surrogates by content clients against this path pattern:

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. 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.

}, { }, ... { } ], "paths": [ { } ] }]]>

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 of the object contained in the generic-metadata-value property (see ). Mandatory-to-Specify: Yes. Property: generic-metadata-value Description: CDNI metadata object. Type: Format/Type is defined by the value of generic-metadata-type property above. Note: generic-metadata-values MUST NOT name any properties "href" (see ). 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 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):

, "generic-metadata-value": { } }]]>

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

Source metadata provides the dCDN with information about content acquisition, i.e., how to contact an uCDN Surrogate or an Origin Server to obtain the content to be served. The sources are not necessarily the actual Origin Servers operated by the CSP but might be a set of Surrogates in the uCDN. Property: sources Description: Sources from which the dCDN can acquire content, listed in order of preference. Type: Array of Source objects (see ) Mandatory-to-Specify: No. Default is to use static configuration, out-of-band from the 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:

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 in preference order within a SourceMetadata object, and then for each preference ranked Source object, 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 ) 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 in preference order (e.g., a pool of servers behind a load balancer). Type: Array of Endpoint objects (See ) Mandatory-to-Specify: Yes. Property: protocol Description: Network retrieval protocol to use when requesting content from this source. Type: Protocol (see ) 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:

LocationACL metadata defines which locations a User Agent needs to be in, in order to be able to receive the associated content. A LocationACL which 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 matches the User Agent's location, then the result is an action of deny. Although the LocationACL, TimeWindowACL (see ), and ProtocolACL (see ) are independent GenericMetadata objects, they can provide conflicting information to a dCDN, e.g., a content request which 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: Access control list which allows or denies (blocks) delivery based on the User Agent's location. Type: Array of LocationRule objects (see ) Mandatory-to-Specify: No. Default is allow all locations. Example LocationACL object that allows the dCDN to deliver content to any location/IP address:

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

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 ) 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:

A Footprint object describes the footprint to which a LocationRule can be applied to, e.g., an IPv4 address range or a geographic location. Property: footprint-type Description: Registered footprint type (see ). The footprint types specified by this document are: "ipv4cidr" (IPv4CIDR, see ), "ipv6cidr" (IPv6CIDR, see ), "asn" (Autonomous System Number, see ) and "countrycode" (Country Code, see ). 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 CountryCode), 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:

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

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

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

TimeWindowACL metadata defines time-based restrictions. A TimeWindowACL which 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 matches the current time, then the result is an action of deny. Although the LocationACL (see ), TimeWindowACL, and ProtocolACL (see ) are independent GenericMetadata objects, they can provide conflicting information to a dCDN, e.g., a content request which 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: Access control list which allows or denies (blocks) delivery based on the time of a User Agent's request. Type: Array of TimeWindowRule objects (see ) Mandatory-to-Specify: No. Default is allow all time windows. Example TimeWIndowACL object (which contains a TimeWindowRule object which itself 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:

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 ) 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:

A TimeWindow object describes a time range which can be applied by an 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 ) Mandatory-to-Specify: Yes. Property: end Description: The end time of the window. Type: Time (see ) 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:

ProtocolACL metadata defines delivery protocol restrictions. A ProtocolACL which 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 protocol matches the request protocol, then the result is an action of deny. Although the LocationACL, TimeWindowACL, and ProtocolACL are independent GenericMetadata objects, they can provide conflicting information to a dCDN, e.g., a content request which 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: Description: Access control list which allows or denies (blocks) delivery based on delivery protocol. Type: Array of ProtocolRule objects (see ) Mandatory-to-Specify: No. Default is allow all protocols. Example ProtocolACL object (which contains a ProtocolRule object) that only allows the dCDN to deliver content using HTTP/1.1:

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 Protocols (see ) 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 ProtocolRule object) that allows the dCDN to deliver content using HTTP/1.1:

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 of the authorization methods in the list is satisfied for that request. Type: Array of Auth objects (see ) Mandatory-to-Specify: No. Default is no authorization required. Example DeliveryAuthorization object (which contains an Auth object):

, "auth-value": { } } ] } }]]>

A Cache object describes the cache control parameters to be applied to the content by intermediate caches. Property: ignore-query-string Description: Allows a Surrogate to ignore URI query string parameters when comparing the requested URI against the URIs in its cache for equivalence. Matching query parameters to ignore MUST be case-insensitive. Each query parameter to ignore is specified in the list. If all query parameters should be ignored, then the list MUST be specified and MUST be empty. Type: Array of String Mandatory-to-Specify: No. Default is to consider query string parameters when comparing URIs. Example Cache object that instructs the dCDN to ignore all query parameters:

Example Cache object that instructs the dCDN to ignore the (case-insensitive) query parameters named "sessionid" and "random":

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 ). The GenericMetadata which contain 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 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:

, "auth-value": { } } } ]]>

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 an empty string. Example Grouping object that specifies a Content Collection Identifier for the content associated with the Grouping object's parent HostMetadata and PathMetadata:

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

A Link object can be used in place of any of the objects or properties 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 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:

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

}, { "href": "https://metadata.ucdn.example/hostmatch1234" } ] } ]]>

Protocol objects are used to specify registered protocols for content acquisition or delivery (see ). Type: String Example:

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 . IPv6 addresses MUST be encoded in one of the IPv6 address formats specified in although receivers MUST support all IPv6 address formats specified in . Hostnames MUST conform to the Domain Name System (DNS) syntax defined in and . Internationalized Domain Names (IDN) must first be transformed to the IDNA encoding as per . Type: String Example Hostname:

Example IPv4 address:

Example IPv6 address (with port number):

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) . Type: Integer Example Time representing 09:00:00 01/01/2000 UTC:

An IPv4address CIDR block encoded as specified by the 'IPv4address' rule in Section 3.2.2 of 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 IPv4 CIDR:

An IPv6address CIDR block encoded in one of the IPv6 address formats specified in 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 IPv6 CIDR:

An Autonomous System Number encoded as a string consisting of the characters "as" (in lowercase) followed by the Autonomous System number . Type: String Example ASN:

An ISO 3166-1 alpha-2 code in lowercase. Type: String Example Country Code representing the USA:

CDNI metadata is used to convey information pertaining to content delivery from uCDN to dCDN. For optional metadata, it can be useful for the uCDN to know if the dCDN supports the underlying functionality described by the metadata, prior to delegating any content requests to the dCDN. 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 which might be assigned optional values, it could be useful for the uCDN to know which values a dCDN supports, prior to delegating any content requests to that dCDN. 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 and Capabilities Interface (FCI) provides a means of advertising capabilities from dCDN to uCDN . Support for optional metadata types and values can be advertised using the FCI.

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 either: Dynamically as required by the dCDN to process received requests. For example in response to a query from an uCDN over the CDNI Request Routing Redirection interface (RI) or in response to receiving a request for content from a User Agent. Or; 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 . 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 and ). To retrieve CDNI metadata, a CDNI metadata client (i.e., a client in the dCDN) first makes a HTTP GET request for the URI of the HostIndex which provides the CDNI metadata client with an array of Hostnames for which the uCDN can delegate content delivery to the dCDN. The CDNI metadata client can then obtain any other CDNI metadata objects by making a HTTP GET requests for any linked metadata objects it requires. 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. Therefore 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.

The CDNI metadata interface uses HTTP as the underlying protocol transport . The HTTP Method in the request defines the operation the request would like to perform. 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 ETag to enable validation of cached versions of returned resources. The CDNI metadata interface specified in this document is a read-only interface. A server implementation of the CDNI metadata interface MUST reject attempts by a CDNI metadata client to update the CDNI metadata, including all requests with HTTP Method PUT, POST or DELETE. 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.

In the general case, a CDNI metadata server makes CDNI metadata objects available via a unique URIs and thus, in order to retrieve CDNI metadata, a CDNI metadata client first makes a 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 a 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-patterns in any PathMatch objects listed in the HostMetadata object). If any PathMetadata are found to match (and are linked rather than embedded), the CDNI metadata client makes another GET request for the PathMetadata. Each PathMetadata object can also include references to yet 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 an 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 a 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 should be used to handle a particular User Agent request. When application level redirection (e.g., HTTP 302 redirects) is being used between CDNs, it is expected that the 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) and therefore dCDNs will have to apply local policy when deciding which uCDN's metadata to apply.

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.

CDNI metadata objects MUST be encoded as I-JSON objects containing a dictionary of (key,value) pairs where the keys are the property names and the values are the associated property values. The keys of the dictionary are the names of the properties associated with the object and are therefore dependent on the specific object 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.

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 specifies a type field and a type-specific value field that allows any metadata to be included in either the HostMetadata or PathMetadata arrays. As with the initial GenericMetadata types defined in , future GenericMetadata types MUST specify the information necessary for constructing and decoding the GenericMetadata object. Any document which defines a new GenericMetadata type MUST: Specify and register the CDNI Payload Type used to identify the new GenericMetadata type being specified. 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 ). Define a name, description, type, and whether or not the property is mandatory-to-specify. Describe the semantics of the new type including its purpose and example of a use case to which it applies including an example encoded in I-JSON. Describe the security and privacy consequences, for both the user-agent and the CDN, of the new GenericMetadata object. 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.

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 mis-communication, mis-configuration, 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.

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 which metadata should be applied, especially if the functionality of the metadata overlap. As described in , metadata override only applies to metadata objects of the same exact type found in HostMetadata and nested PathMetadata structures. The CDNI metadata interface does not support enforcement of dependencies between different metadata types. It is the responsibility of the CSP and the CDN operators to ensure that metadata assigned to a given 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.

The version of CDNI metadata objects is conveyed inside the CDNI Payload Type that is included in either the HTTP Content-Type header, for example: "Content-Type: application/cdni; ptype=MI.HostIndex", when retrieved via a link, or in the link type (), generic-metadata-type (), or auth-type () 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, e.g., MI.HostIndex.v2, MI.HostIndex.v3, etc. In some cases, structural metadata may be included without explicit type designation. [Ed. Note: There are a couple options here: 1) require that all structural metadata is referenced via link, so that the link type is present, or 2) require that all structural metadata be versioned together, so that one can always tell the version of an embedded structural object based on the version of the outer-most structural object, referenced in the Content-Type.] 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.

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.". lists the CDNI Payload Type for the metadata objects (resources) specified in this document. Data Object CDNI Payload Type HostIndex MI.HostIndex HostMatch MI.HostMatch HostMetadata MI.HostMetadata PathMatch MI.PathMatch PatternMatch MI.PatternMatch PathMetadata MI.PathMetadata SourceMetadata MI.SourceMetadata Source MI.Source LocationACL MI.LocationACL LocationRule MI.LocationRule Footprint MI.Footprint TimeWindowACL MI.TimeWindowACL TimeWindowRule MI.TimeWindowRule TimeWindow MI.TimeWindow ProtocolACL MI.ProtocolACL ProtocolRule MI.ProtocolRule DeliveryAuthorization MI.DeliveryAuthorization Cache MI.Cache Auth MI.Auth Grouping MI.Grouping

A dCDN requests the HostIndex and receive the following object with a CDNI payload type of "MI.HostIndex":

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":

Suppose the path of the requested resource matches the "/video/movies/*" pattern, the next metadata requested would be for "https://metadata.ucdn.example/host1234/pathDCE" with an expected CDNI payload type of "MI.PathMetadata":

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 CDNI payload type "MI.PathMetadata":

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

This document requests the registration of the following CDNI Payload Types under the IANA CDNI Payload Type registry: Payload Type Specification MI.HostIndex RFCthis MI.HostMatch RFCthis MI.HostMetadata RFCthis MI.PathMatch RFCthis MI.PatternMatch RFCthis MI.PathMetadata RFCthis MI.SourceMetadata RFCthis MI.Source RFCthis MI.LocationACL RFCthis MI.LocationRule RFCthis MI.Footprint RFCthis MI.TimeWindowACL RFCthis MI.TimeWindowRule RFCthis MI.TimeWindow RFCthis MI.ProtocolACL RFCthis MI.ProtocolRule RFCthis MI.DeliveryAuthorization RFCthis MI.Cache RFCthis MI.Auth RFCthis MI.Grouping RFCthis [RFC Editor: Please replace RFCthis with the published RFC number for this document.]

Purpose: The purpose of this payload type is to distinguish HostIndex MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish HostMatch MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish HostMetadata MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish PathMatch MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish PatternMatch MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish PathMetadata MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish SourceMetadata MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish Source MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish LocationACL MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish LocationRule MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish Footprint MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish TimeWindowACL MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish TimeWindowRule MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish TimeWindow MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish ProtocolACL MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish ProtocolRule MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish DeliveryAuthorization MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish Cache MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish Auth MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish Grouping MI objects (and any associated capability advertisement) Interface: MI/FCI Encoding: see

The IANA is requested to create a new "CDNI Metadata Footprint Types" subregistry in the "Content Delivery Networks Interconnection (CDNI) Parameters" registry. The "CDNI Metadata Footprint Types" namespace defines the valid Footprint object type values used by the Footprint object in . Additions to the Footprint type namespace conform to the "Specification Required" policy as defined in . 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 Footprint Registry values: Footprint Type Description Specification ipv4cidr IPv4 CIDR address block RFCthis ipv6cidr IPv6 CIDR address block RFCthis asn Autonomous System (AS) Number RFCthis countrycode ISO 3166-1 alpha-2 code RFCthis [RFC Editor: Please replace RFCthis with the published RFC number for this document.]

The IANA is requested to create a new "CDNI Metadata Protocol Types" subregistry in the "Content Delivery Networks Interconnection (CDNI) Parameters" registry. The "CDNI Metadata Protocol Types" namespace defines the valid Protocol object values in , used by the SourceMetadata and ProtocolACL objects. Additions to the Protocol namespace conform to the "Specification Required" policy as defined in , 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: Protocol Type Description Type Specification Protocol Specifications http/1.1 Hypertext Transfer Protocol -- HTTP/1.1 RFCthis RFC7230 https/1.1 HTTP/1.1 Over TLS RFCthis RFC7230, RFC2818 [RFC Editor: Please replace RFCthis with the published RFC number for this document.]

A malicious metadata server, proxy server, or attacker, impersonating an authentic uCDN metadata interface without being detected, could provide false metadata to a dCDN that either: Denies service for one or more pieces of content to one or more User Agents; Directs dCDNs to contact malicious origin servers instead of the actual origin servers, and substitute legitimate content with malware or slanderous alternate content; or 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(s). 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 ).

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 ).

An implementation of the CDNI metadata interface MUST support TLS transport as per and . TLS MUST be used by the server-side (dCDN) and the client-side (uCDN) 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. and, once they have mutually authenticated each other, it allows: The dCDN and uCDN to authorize each other (to ensure they are transmitting/receiving CDNI metadata requests and responses from an authorized CDN); CDNI metadata interface requests and responses to be transmitted with confidentiality; and 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 MUST be followed.

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.

[RFC Editor Note: Please move the contents of this section to the Authors' Addresses section prior to publication as an RFC.]