]> Qwilt

6, Ha'harash Hod HaSharon 4524079 Israel nir@apache.org

Qwilt

6, Ha'harash Hod HaSharon 4524079 Israel ori.finkelman.ietf@gmail.com

Verizon

13100 Columbia Pike Silver Spring MD 20904 USA sanjay.mishra@verizon.com

Qwilt

275 Shoreline Dr Ste 510 Redwood City CA 94065 USA jayrobertson@acm.org

Viasat

1295 Beacon street Unit 249 Brookline MA 02446 USA alan.arolovitch@gmail.com

This document obsoletes RFC8007. The document describes the part of Content Delivery Network Interconnection (CDNI) Control interface that allows a CDN to trigger activity in an interconnected CDN that is configured to deliver content on its behalf. The upstream CDN MAY use this mechanism to request that the downstream CDN pre-position metadata or content as well as request that it invalidate or purge metadata or content. The upstream CDN MAY monitor the status of activity that it has triggered in the downstream CDN.

introduces the problem scope for Content Delivery Network Interconnection (CDNI) and lists the four categories of interfaces that may be used to compose a CDNI solution (Control, Metadata, Request Routing, and Logging). expands on the information provided in and describes each of the interfaces and the relationships between them in more detail. The CDNI Control Interface / Triggers 1st edition , deprecated by this document, describes the "CI/T" interface -- "CDNI Control interface / Triggers". It does not consider those parts of the Control interface that relate to configuration, bootstrapping, or authentication of CDN Interconnect interfaces. Section 4 of identifies the requirements specific to the CI/T interface; requirements applicable to the CI/T interface are CI-1 to CI-6. This document is a second edition of the CDNI Control Interface / Triggers, which defines a new version, "v2", of the interface objects. The new objects replace the trigger interface's main objects, the "ci-trigger-command" object and its matching "ci-trigger-status" object, and improve the interface's flexibility and extensibility. The document also provides a Trigger Extension mechanism that MAY be used to provide further instruction on the trigger execution. Additionally, this second edition includes cascaded CDN error propagation for improved trigger execution monitoring. Note that the trigger interface mechanism itself is not changed by this new edition. outlines the model for the CI/T interface at a high level. describes the trigger attributes used for specifying the trigger's targets and for controlling the trigger's execution. describes collections of Trigger Status Resources. defines the web service provided by the downstream CDN. lists properties of CI/T Commands and Status Resources. describes the Trigger's Spec object. describes the Trigger's Extensions object. describes the FCI capabilities objects used to inform on the supported CI/T-related capabilities. contains example messages.

This document reuses the terminology defined in and uses "uCDN" and "dCDN" as shorthand for "upstream CDN" and "downstream CDN", respectively. Additionally, the following terms are used throughout this document and are defined as follows: HLS - HTTP Live Streaming DASH - Dynamic Adaptive Streaming Over HTTP MSS - Microsoft Smooth Streaming The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

A CI/T Command, sent from the uCDN to the dCDN, is a request for the dCDN to do some work (an "action") relating to data associated with content requests originating from the uCDN. Two of CI/T Commands exist: CI/T Create Trigger Command and CI/T Modify Trigger Command. The CI/T Modify Command can be used to request cancellation and/or modification of an earlier CI/T Trigger Command. A CI/T Trigger Action is of one of the following: preposition - used to instruct the dCDN to fetch metadata from the uCDN or content from any origin including the uCDN. invalidate - used to instruct the dCDN to revalidate specific metadata or content before reusing it. purge - used to instruct the dCDN to delete specific metadata or content. Note that additional CI/T Trigger Actions can be defined and registered in the future. The CI/T interface is a web service offered by the dCDN. It allows CI/T Commands to be issued and triggered activity to be tracked. The CI/T interface builds on top of HTTP/1.1 . References to URLs in this document relate to HTTP/HTTPS URIs, as defined in Section 4.2 of . When the dCDN accepts a CI/T Command, it creates a resource describing the status of the triggered activity -- a Trigger Status Resource. The uCDN can poll Trigger Status Resources to monitor progress. The dCDN maintains at least one collection of Trigger Status Resources for each uCDN. Each uCDN only has access to its own collections, the locations of which are shared when CDNI is established. To trigger activity in the dCDN, the uCDN POSTs a CI/T Command to the collection of Trigger Status Resources. If the dCDN accepts the CI/T Command, it creates a new Trigger Status Resource and returns its location to the uCDN. To monitor progress, the uCDN can GET the Trigger Status Resource. To request cancellation of a CI/T Trigger Command, the uCDN can POST to the collection of Trigger Status Resources or simply DELETE the Trigger Status Resource. Note that the version of the CI/T Command objects POSTed by the uCDN MUST match the version of CI/T Status Resource objects generated and reported by the dCDN. Thus, sending a "ci-trigger-command" object as the command generates a "ci-trigger-status" structured resource to be reported, while sending a "ci-trigger-command.trigger.v2" object generates a "ci-trigger-status.v2" object. In addition to the collection of all Trigger Status Resources for the uCDN, the dCDN can maintain filtered views of that collection. These filtered views are defined in and include collections of Trigger Status Resources filtered by Trigger Status or Trigger Label. These collections provide a mechanism for polling the status of multiple jobs. Figure 1 is an example showing the basic message flow used by the uCDN to trigger activity in the dCDN and for the uCDN to discover the status of that activity. Only successful triggering is shown. Examples of the messages are shown in .

[ ]--+ | [ ] | (2) | (3) HTTP 201 Response [ ]<-+ [ ] <-------------------------------------------------- [ ] | Loc: https://dcdn.example.com/triggers/uCDN/123 | | | . . . . . . . . . | | | (4) GET https://dcdn.example.com/triggers/uCDN/123 | [ ] --------------------------------------------------> [ ] | [ ] | (5) HTTP 200 Trigger Status Resource [ ] [ ] <-------------------------------------------------- [ ] | | | | ]]>

The steps in Figure 1 are as follows: The uCDN triggers action in the dCDN by POSTing a CI/T Command to a collection of Trigger Status Resources -- "https://dcdn.example.com/triggers/uCDN". This URL was given to the uCDN when the CI/T interface was established. The dCDN authenticates the request, validates the CI/T Command, and, if it accepts the request, creates a new Trigger Status Resource. The dCDN responds to the uCDN with an HTTP 201 response status and the location of the Trigger Status Resource. The uCDN MAY query, possibly repeatedly, the Trigger Status Resource in the dCDN. The dCDN responds to each query with the Trigger Status Resource, describing the progress or results of the CI/T Trigger Command. The remainder of this document describes the messages, Trigger Status Resources, and collections of Trigger Status Resources in more detail.

Timing of the execution of CI/T Commands is under the dCDN's control, including its start time and pacing of the activity in the network. Instructions regarding this timing may be included in the trigger using one of the Trigger Extension Objects defined in , such as and . CI/T "invalidate" and "purge" commands MUST be applied to all data acquired before the command was accepted by the dCDN. The dCDN SHOULD NOT apply CI/T "invalidate" and "purge" commands to data acquired after the CI/T Command was accepted, but this may not always be achievable, so the uCDN cannot count on that. If the uCDN wishes to invalidate or purge content and then immediately pre-position replacement content at the same URLs, it SHOULD ensure that the dCDN has completed the invalidate/purge before initiating the pre-positioning. Otherwise, there is a risk that the dCDN pre-positions the new content, then immediately invalidates or purges it (as a result of the two uCDN requests running in parallel). Because the CI/T Command timing is under the dCDN's control, the dCDN implementation can choose whether to apply CI/T "invalidate" and "purge" commands to content acquisition that has already started when the command is received.

Each CI/T Command can operate on multiple metadata and content elements, usually referred to by their URLs. These elements are targeted by specifying both their subject (i.e., "metadata" or "content") as well as specification method (e.g., URL Regexes) and value. Multiple representations of an HTTP resource may share the same URL. CI/T Trigger Commands that invalidate or purge metadata or content apply to all resource representations with matching URLs.

In a network of interconnected CDNs, a single uCDN will originate a given item of metadata and associated content. It would possibly distribute that metadata and content to more than one dCDN, which in turn distributes that metadata and content to additional CDNs located further downstream. An intermediate CDN is a dCDN that passes on CDNI Metadata and content to dCDNs located further downstream. A "diamond" configuration is one where a dCDN can acquire metadata and content originated in one uCDN from that uCDN itself and an intermediate CDN, or via more than one intermediate CDN. CI/T Commands originating in the single source uCDN affect metadata and content in all dCDNs; however, in a diamond configuration, it may not be possible for the dCDN to determine from which uCDN it acquired content. In this case, a dCDN MUST allow each uCDN from which it may have acquired the content to act upon that content using CI/T Commands. In all other cases, a dCDN MUST reject CI/T Commands from a uCDN that attempts to act on another uCDN's content by using, for example, responding with an HTTP 403 ("Forbidden"). Security considerations are discussed further in . The diamond configuration may lead to inefficient interactions, but the interactions are otherwise harmless. For example: When the uCDN issues an "invalidate" CI/T Command, a dCDN will receive that command from multiple directly connected uCDNs. The dCDN may schedule multiple such commands separately, and the last scheduled command may affect content already revalidated following execution of the "invalidate" command that was scheduled first. If one of a dCDN's directly connected uCDNs loses its rights to distribute content, it may issue a CI/T "purge" command. That purge may affect content the dCDN could retain because it's distributed by another directly connected uCDN. But, that content can be reacquired by the dCDN from the remaining uCDN. When the uCDN originating an item of content issues a CI/T purge followed by a pre-position, two directly connected uCDNs will pass those commands to a dCDN. That dCDN implementation need not merge those operations or notice the repetition, in which case the purge issued by one uCDN will be completed before the other. The first uCDN to finish its purge may then forward the "preposition" trigger, and content pre-positioned as a result might be affected by the still-running purge issued by the other uCDN. However, the dCDN will reacquire that content as needed, or when it's asked to pre-position the content by the second uCDN. A dCDN implementation could avoid this interaction by knowing which uCDN it acquired the content from, or it could minimize the consequences by recording the time at which the "invalidate"/"purge" command was received and not applying it to content acquired after that time.

Possible states for a Trigger Status Resource are defined in . The CI/T Trigger Command MUST NOT be reported as "complete" until all operations have been completed successfully. The reasons for failure, and URLs or patterns affected, SHOULD be enumerated in the Trigger Status Resource. For more details, see . If a dCDN is also acting as a uCDN in a cascade, it MUST forward CI/T Commands to any dCDNs that may be affected. The CI/T Trigger Command MUST NOT be reported as "complete" in a CDN until it is "complete" in all of its dCDNs. If a CI/T Trigger Command is reported as "processed" in any dCDN, intermediate CDNs MUST NOT report "complete"; instead, they MUST also report "processed". A CI/T Command MAY be reported as "failed" as soon as it fails in a CDN or any of its dCDNs. A cancelled CI/T Trigger Command MUST be reported as "cancelling" until it has been reported as "cancelled", "complete", or "failed" by all dCDNs in a cascade.

The following attributes define the trigger execution.

Trigger Action is used in a Trigger Specification to describe trigger actions. It was initially referred to in as "Trigger Type". All trigger actions MUST be registered in the IANA "CDNI CI/T Trigger Types" registry (see ). A dCDN receiving a request containing a trigger action that it does not recognize or does not support MUST reject the request by creating a Trigger Status Resource with "failed" status and the "errors" array containing an Error.v2 Description with error "eunsupported" (see ). The following trigger actions are defined by this document: JSON String Description preposition A request for the dCDN to acquire metadata or content. invalidate A request for the dCDN to invalidate metadata or content. After servicing this request, the dCDN will not use the specified data without first revalidating it using, for example, an "If-None-Match" HTTP request. The dCDN need not erase the associated data. purge A request for the dCDN to erase metadata or content. After servicing the request, the specified data MUST NOT be held on the dCDN (the dCDN should reacquire the metadata or content from the uCDN if it needs it).

The CDNI Control Interface / Triggers 1st edition defines a set of properties and objects used by the trigger commands in order to specify the targets upon which the trigger is applied. This document modifies the trigger interface objects so it has a list of trigger specs. Such structure improves the interface's extensibility and flexibility. Furthermore, the document defines a generic trigger spec object that acts as a wrapper for managing individual CDNI trigger specs in an opaque manner, allowing future extension of the interface. All trigger specs MUST be registered in the IANA "CDNI CI/T Trigger Specs" registry (see ). A dCDN receiving a request containing a trigger spec that it does not recognize or does not support MUST reject the request by creating a Trigger Status Resource with "failed" status and the "errors" array containing an Error.v2 Description with error "espec" (see ). This document also defines an initial set of trigger spec objects and registers them in the IANA "CDNI CI/T Trigger Specs" registry: JSON String Description urls Allowing the specification of trigger targets via URLs. ccids Allowing the specification of trigger targets via CCIDs content grouping, as defined in section 4.2.8 . uri-pattern-match Allowing the specification of trigger targets via URI patterns. uri-regex-match Allowing the specification of trigger targets via regexes matching their URI, as defined in . content-objectlist Allowing the specification of trigger targets via an object list and an object list type.

Because the scope of the trigger may relate to either metadata as well as content, the "trigger spec object" also specifies the trigger's target subject (i.e., metadata or content) against which to match. All trigger subjects MUST be registered in the IANA "CDNI CI/T Trigger Subjects" registry (see ). A dCDN receiving a request containing a trigger subject that it does not recognize or does not support MUST reject the request by creating a Trigger Status Resource with "failed" status and the "errors" array containing an Error.v2 Description with error "esubject" (see ). This document also defines an initial set of trigger subject values and registers them in the IANA "CDNI CI/T Trigger Subjects" registry: JSON String Description metadata Indicating the trigger target specification refers to Metadata object, as defined at . content Indicating the trigger target specification refers to client facing content.

Each CI/T Command usually refers to the targets by the target URLs, using a "urls" trigger spec object or some aggregating spec such as the "url-regex-match". If content URLs are transformed by an intermediate CDN in a cascade, that intermediate CDN MUST similarly transform URLs in CI/T Commands it passes to its dCDN. When processing Trigger Specifications, CDNs MUST ignore the URL scheme (HTTP or HTTPS) in comparing URLs. For example, for a CI/T "invalidate" or "purge" command, content MUST be invalidated or purged regardless of the protocol clients used to request it.

The CDNI Control Interface / Triggers 1st edition defines a set of properties and objects used by the trigger commands. This 2nd edition defines an extension mechanism to the triggers interface that enables applications to add instructions for finer control over the trigger execution, for example indicating a time window in which to execute the trigger. This document specifies a generic trigger extension object wrapper for managing individual CDNI trigger extensions in an opaque manner. All trigger extensions are optional, and it is thus the responsibility of the extension specification to define a consistent default behavior for the case the extension is not present. All trigger extensions MUST be registered in the IANA "CDNI CI/T Trigger Extensions" registry (see ). This document also defines an initial set of trigger extension objects and registers them in the IANA "CDNI CI/T Trigger Extensions" registry: JSON String Description location-policy Allowing the control over the locations in which the trigger is executed. time-policy Allowing the scheduling of a trigger to run in a specific time window. Example use cases Pre-position with cache location policy Purge content with cache location policy Pre-position at a specific time Purge by content acquisition time (e.g., purge all content acquired in the past X hours)

As described in , Trigger Status Resources exist in the dCDN to report the status of activity triggered by each uCDN. A collection of Trigger Status Resources is a resource that contains a reference to each Trigger Status Resource in that collection. Note that the collection may refer to Trigger Status Resources of triggers from several versions of CI/T objects, i.e., a subsequent call for the retrieval of the relevant trigger status may provide objects of various MIME media types: ci-trigger-status as defined in , ci-trigger-status.v2 defined in this document, or objects of future CI/T objects versions, based on the CI/T command version used for the creation of the trigger. The dCDN MUST make a collection of a uCDN's Trigger Status Resources available to that uCDN. This collection includes all of the Trigger Status Resources created for CI/T Commands from the uCDN that have been accepted by the dCDN and have not yet been deleted by the uCDN or expired and removed by the dCDN (as described in ). Trigger Status Resources belonging to a uCDN MUST NOT be visible to any other CDN. The dCDN could, for example, achieve this by offering different collection URLs to each uCDN and by filtering the response based on the uCDN with which the HTTP client is associated. To trigger an activity in a dCDN or to cancel a triggered activity, the uCDN POSTs a CI/T Command to the dCDN's collection of the uCDN's Trigger Status Resources. To allow the uCDN to check the status of multiple jobs in a single request, the dCDN MAY also maintain collections representing filtered views of the collection of all Trigger Status Resources. These filtered collections are "optional-to-implement", but if they are implemented, the dCDN MUST include links to them in the collection of all Trigger Status Resources.

dCDN MAY provide filtered collections per Trigger Status. If implemented, dCDN SHOULD provide a separate filtered collection for every Trigger Status, and advertise these collections in the collection of all Trigger Resources.

dCDN MAY provide filtered collections per Trigger Label, as specified by uCDN in . If implemented, dCDN SHOULD provide a separate filtered collection for every unique Trigger Label, and advertise these collections in the collection of all Trigger Resources.

This section describes an interface to enable a uCDN to trigger activity in a dCDN. The CI/T interface builds on top of HTTP, so dCDNs may make use of any HTTP feature when implementing the CI/T interface. For example, a dCDN SHOULD make use of HTTP's caching mechanisms to indicate that a requested response/representation has not been modified, reducing the uCDN's processing needed to determine whether the status of triggered activity has changed. dCDNs MAY implement separate CI/T interfaces per , i.e. one CI/T interface for trigger operations on metadata and another for operations on content. In this case, dCDN MUST advertise separate interface endpoints via . All dCDNs implementing CI/T MUST support the HTTP GET, HEAD, POST, and DELETE methods as defined in . The only representation specified in this document is JSON . It MUST be supported by the uCDN and by the dCDN. The URL of the dCDN's collection of all Trigger Status Resources needs to be either discovered by or configured in the uCDN. The mechanism for discovery of that URL is outside the scope of this document. CI/T Commands are POSTed to the dCDN's collection of all Trigger Status Resources. If a CI/T Trigger Command is accepted by the dCDN, the dCDN creates a new Trigger Status Resource and returns its URI to the uCDN in an HTTP 201 response. The triggered activity can then be monitored by the uCDN using that resource and the collections described in . The URI of each Trigger Status Resource is returned to the uCDN when it is created, and URIs of all Trigger Status Resources are listed in the dCDN's collection of all Trigger Status Resources. This means all Trigger Status Resources can be discovered by the uCDN, so dCDNs are free to assign whatever structure they desire to the URIs for CI/T resources. Therefore, uCDNs MUST NOT make any assumptions regarding the structure of CI/T URIs or the mapping between CI/T objects and their associated URIs. The URIs used in the examples in this document are purely illustrative and are not intended to impose a definitive structure on CI/T interface implementations.

To issue a CI/T Command, the uCDN makes an HTTP POST to the dCDN's collection of all of the uCDN's Trigger Status Resources. The request body of that POST is a CI/T Command, as described in . The dCDN validates the CI/T Command. If the command is malformed or the uCDN does not have sufficient access rights, the dCDN MUST either respond with an appropriate 4xx HTTP error code and not create a Trigger Status Resource or create a "failed" Trigger Status Resource containing an appropriate Error.v2 Description. When a CI/T Trigger Command is accepted, the dCDN MUST create a new Trigger Status Resource that will convey a specification of the CI/T Command and its current status. The HTTP response to the uCDN MUST have status code 201 and MUST convey the URI of the Trigger Status Resource in the Location header field . The HTTP response SHOULD include the content of the newly created Trigger Status Resource. This is particularly important in cases where the CI/T Trigger Command has been completed immediately. Once a Trigger Status Resource has been created, the dCDN MUST NOT reuse its URI, even after that Trigger Status Resource has been removed. The dCDN SHOULD track and report on the progress of CI/T Trigger Commands using a Trigger Status Resource (). If the dCDN is not able to do that, it MUST indicate that it has accepted the request but will not be providing further status updates. To do this, it sets the status of the Trigger Status Resource to "processed". In this case, CI/T processing should continue as for a "complete" request, so the Trigger Status Resource MUST be added to the dCDN's collection of complete Trigger Status Resources. The dCDN SHOULD also provide an estimated completion time for the request by using the "etime" property of the Trigger Status Resource. This will allow the uCDN to schedule pre-positioning after an earlier delete of the same URLs is expected to have finished. If the dCDN can track the execution of CI/T Commands and a CI/T Command is queued by the dCDN for later action, the "status" property of the Trigger Status Resource MUST be "pending". Once processing has started, the status MUST be "active". Finally, once the CI/T Command is complete, the status MUST be set to "complete" or "failed". A CI/T Trigger Command may result in no activity in the dCDN if, for example, it is an "invalidate" or "purge" request for data the dCDN has not yet acquired, or a "preposition" request for data that it has already acquired and that is still valid. In this case, the status of the Trigger Status Resource MUST be "processed" or "complete", and the Trigger Status Resource MUST be added to the dCDN's collection of complete Trigger Status Resources. Once created, Trigger Status Resources can be cancelled or deleted by the uCDN, but not modified. The dCDN MUST reject PUT and POST requests from the uCDN to Trigger Status Resources by responding with an appropriate HTTP status code -- for example, 405 ("Method Not Allowed").

The uCDN can request modification of an existing Trigger Command by issuing CI/T Modify Trigger Command. Allowed modifications include an update of the Trigger Command specification and change of state. dCDN MAY accept the request to update specification when the trigger has "pending" status, i.e. the trigger has not been acted upon yet. dCDN MAY accept the trigger status change request as long as: the requested state is "cancelled" the trigger has either "pending" or "active" status before the request Modification of existing triggers is useful for uCDN to correct an error in trigger specification or trigger extension(s) that may govern when the Trigger Command is to be executed. The dCDN MUST respond to the CI/T Modify Trigger Command appropriately. For example, HTTP status code 200 ("OK") should be returned if the modification has been processed, 202 ("Accepted") if the command has been accepted but the modification is not fully complete yet, 404 ("Not Found") when the Trigger Status Resource does not exist, 409 ("Conflict") when the Trigger Status Resource is in a state that doesn't allow the requested modification, 501 ("Not Implemented") if modification is not supported by the dCDN or an appropriate 4xx HTTP error code in case of a malformed request.

The uCDN has two ways to check the progress of CI/T Commands it has issued to the dCDN, as described in Sections and . To allow the uCDN to check for changes in the status of a Trigger Status Resource or collection of Trigger Status Resources without refetching the whole resource or collection, the dCDN SHOULD include entity-tags (ETags) for the uCDN to use as cache validators, as defined in . The dCDN SHOULD use the cache control headers for responses to GETs for Trigger Status Resources and Collections to indicate the frequency at which it recommends that the uCDN should poll for change.

The uCDN can fetch the collection of its Trigger Status Resources or filtered views of that collection. This makes it possible to poll the status of all CI/T Trigger Commands in a single request. If the dCDN moves a Trigger Status Resource from the active to the completed collection, the uCDN can fetch the result of that activity. When polling in this way, the uCDN SHOULD use HTTP ETags to monitor for change, rather than repeatedly fetching the whole collection. An example of this is given in .

If dCDN advertises support for extended status, uCDN MAY request the extended Trigger Collection, which embeds all Trigger Status resources in the collection itself, in addition to a list of Trigger Status resource URLs. This support includes all types of Trigger Status Resources Collections, including filtered collections. uCDN SHOULD request the extended Trigger Collection view by passing the query string parameter "status=extended" when requesting a Trigger Status Resource Collection. dCDN SHOULD appropriately respond to the request for extended status with HTTP Status 200 ("OK") when such request can be satisfied, with error code 501 ("Not Implemented") if the capability has not been implemented or advertised, and 400 ("Bad Request") in case of an unrecognized query parameters.

The uCDN has a URI provided by the dCDN for each Trigger Status Resource it has created. It may fetch that Trigger Status Resource at any time. This can be used to retrieve progress information and to fetch the result of the CI/T Command. When polling in this way, the uCDN SHOULD use HTTP ETags to monitor for change, rather than repeatedly fetching the Trigger Status Resource.

The uCDN can request cancellation of a trigger by issuing CI/T Modify Trigger Command to the specific trigger's Trigger Status Resource URL and setting the "desired-status" field to "cancelled". The dCDN is required to accept and respond to the CI/T Modify Command, but the actual cancellation of a CI/T Trigger Command is optional-to-implement. The dCDN MUST respond to the CI/T Modify Command appropriately -- for example, with HTTP status code 200 ("OK") if the cancellation has been processed and the CI/T Command is inactive, 202 ("Accepted") if the command has been accepted but the CI/T Command remains active, 404 ("Not Found") when the Trigger Status Resource does not exist, or 501 ("Not Implemented") if cancellation is not supported by the dCDN. If cancellation of a "pending" Trigger Status Resource is accepted by the dCDN, the dCDN SHOULD NOT start the processing of that activity. Requesting a cancellation of a trigger using a CI/T Modify Command for a "pending" Trigger Status Resource does not, however, guarantee that the corresponding activity will not be started, because the uCDN cannot control the timing of that activity. Processing could, for example, start after the POST is sent by the uCDN but before that request is processed by the dCDN. If cancellation of an "active" or "processed" Trigger Status Resource is accepted by the dCDN, the dCDN SHOULD stop processing the CI/T Command. However, as with the cancellation of a "pending" CI/T Command, the dCDN does not guarantee this. If the CI/T Command cannot be stopped immediately, the status in the corresponding Trigger Status Resource MUST be set to "cancelling", and the Trigger Status Resource MUST remain in the collection of Trigger Status Resources for active CI/T Commands. If processing is stopped before normal completion, the status value in the Trigger Status Resource MUST be set to "cancelled", and the Trigger Status Resource MUST be included in the collection of failed CI/T Trigger Commands. Cancellation of a "complete" or "failed" Trigger Status Resource requires no processing in the dCDN. Its status MUST NOT be changed to "cancelled".

The uCDN can delete Trigger Status Resources at any time using the HTTP DELETE method. As defined in the CDNI Control Interface / Triggers 1st edition , the effect is similar to cancellation, but no Trigger Status Resource remains afterwards. Note that in cases where the trigger's status before the deletion is not a terminal status (i.e., "completed", "failed" or "cancelled"), the uCDN would not have the ability to further monitor the cancellation process and the final status of the trigger. For this reason, it is recommended that the trigger is cancelled (see ) before trigger deletion and deletion is only used on triggers with a terminal status. Once deleted, the references to a Trigger Status Resource MUST be removed from all Trigger Status Resource collections. Subsequent requests to GET the deleted Trigger Status Resource SHOULD be rejected by the dCDN with an HTTP error. If a "pending" Trigger Status Resource is deleted, the dCDN SHOULD NOT start the processing of that activity. Deleting a "pending" Trigger Status Resource does not, however, guarantee that it has not started, because the uCDN cannot control the timing of that activity. Processing may, for example, start after the DELETE is sent by the uCDN but before that request is processed by the dCDN. If an "active" or "processed" Trigger Status Resource is deleted, the dCDN SHOULD stop processing the CI/T Command. However, as with deletion of a "pending" Trigger Status Resource, the dCDN does not guarantee this. Deletion of a "complete" or "failed" Trigger Status Resource requires no processing in the dCDN other than deletion of the Trigger Status Resource.

The dCDN can choose to automatically delete Trigger Status Resources sometime after they become "complete", "processed", "failed", or "cancelled". In this case, the dCDN will remove the Trigger Status Resource and respond to subsequent requests for it with an HTTP error. If the dCDN does remove Trigger Status Resources automatically, it MUST report the length of time after which it will do so, using a property of the collection of all Trigger Status Resources. It is RECOMMENDED that Trigger Status Resources are not automatically deleted by the dCDN for at least 24 hours after they become "complete", "processed", "failed", or "cancelled". To ensure that it can get the status of its Trigger Status Resources for completed and failed CI/T Commands, it is RECOMMENDED that the uCDN polling interval is less than the time after which records for completed activity will be deleted.

Given three CDNs, A, B, and C, if CDNs B and C delegate delivery of CDN A's content to each other, CDN A's CI/T Commands could be passed between CDNs B and C in a loop. More complex networks of CDNs could contain similar loops involving more hops. To prevent and detect such CI/T loops, each CDN uses a CDN Provider ID (PID) to uniquely identify itself. In every CI/T Command it originates or cascades, each CDN MUST append an array element containing its CDN PID to a JSON array under an entry named "cdn-path". When receiving CI/T Commands, a dCDN MUST check the cdn-path and reject any CI/T Command that already contains its own CDN PID in the cdn-path. Transit CDNs MUST check the cdn-path and not cascade the CI/T Command to dCDNs that are already listed in the cdn-path. The CDN PID consists of the two characters "AS" followed by the CDN provider's Autonomous System number , then a colon (":") and an additional qualifier that is used to guarantee uniqueness in case a particular AS has multiple independent CDNs deployed -- for example, "AS64496:0". If the CDN provider has multiple ASes, the same AS number SHOULD be used in all messages from that CDN provider, unless there are multiple distinct CDNs. If the CDNI Request Routing Redirection interface (RI) described in is implemented by the dCDN, the CI/T interface and the RI SHOULD use the same CDN PID.

A dCDN can signal rejection of a CI/T Command using HTTP status codes -- for example, 400 ("Bad Request") if the request is malformed, or 403 ("Forbidden") or 404 ("Not Found") if the uCDN does not have permission to issue CI/T Commands or it is trying to act on another CDN's data. If any part of the CI/T Trigger Command fails, the trigger SHOULD be reported as "failed" once its activity is complete or if no further errors will be reported. The "errors" property in the Trigger Status Resource will be used to enumerate which actions failed and the reasons for failure, and can be present while the Trigger Status Resource is still "pending" or "active" if the CI/T Trigger Command is still running for some URLs or patterns in the Trigger Specification. Once a request has been accepted, processing errors are reported in the Trigger Status Resource using a list of Error.v2 Descriptions. Each Error.v2 Description is used to report errors against one or more of the URLs or patterns in the Trigger Specification. If a Surrogate affected by a CI/T Trigger Command is offline in the dCDN or the dCDN is unable to pass a CI/T Command on to any of its cascaded dCDNs: If the CI/T Command is abandoned by the dCDN, the dCDN SHOULD report an error. A CI/T "invalidate" command may be reported as "complete" when Surrogates that may have the data are offline. In this case, Surrogates MUST NOT use the affected data without first revalidating it when they are back online. CI/T "preposition" and "purge" commands can be reported as "processed" if affected caches are offline and the activity will complete when they return to service. Otherwise, the dCDN SHOULD keep the Trigger Status Resource in state "pending" or "active" until either the CI/T Command is acted upon or the uCDN chooses to cancel it.

This subsection explains the mechanism for enabling the uCDN to trace an error back to the dCDN in which it occurred. CDNI triggers may be propagated over a chain of downstream CDNs. For example, an upstream CDN A (uCDN-A) that is delegating to a downstream CDN B (dCDN-B) and dCDN-B is delegating to a downstream CDN C (dCDN-C). Triggers sent from uCDN-A to dCDN-B may be redistributed from dCDN-B to dCDN-C, and errors can occur anywhere along the path. Therefore, it might be essential for uCDN-A that sets the trigger, to be able to trace back an error to the downstream CDN where it occurred. This document adds a mechanism to propagate the PID of the dCDN where the fault occurred, back to the uCDN by adding the PID to the error.v2 description. When dCDN-B propagates a trigger further to the downstream dCDN-C, it MUST also propagate back the errors received in the trigger status resource from dCDN-C by adding them to the errors array in its own status resource to be sent back to the originating uCDN-A. While propagating back the errors dCDN-B MAY also specify the dCDN-C PID, indicating to which CDN the error specifically relates. The trigger originating upstream CDN then receives an array built of the errors that occurred in all the CDNs along the execution path, where each error MAY carry its own CDN identifier. below is an example showing the message flow used by uCDN-A to trigger activity in the dCDN-B, followed by dCDN-C, as well as the discovery of the status of that activity, including the Error Propagation.

[ ]--+ | | [ ] | (2) | | [ ]<-+ | | (3) HTTP 201 Response. [ ] | |<----------------------------[ ] | | Loc: [ ] | | https://dcdn-b.example.com [ ] (4) POST | | /triggers/uCDN-A/123 [ ] https://dcdn-c.example.com | | [ ] /triggers/dCDN-B | (5) | [ ]--------------------------->[ ]--+ | | [ ] | | | [ ]<-+ | | (6) HTTP 201 Response. [ ] | [ ]<---------------------------[ ] | | Loc: | | | https://dcdn-c.example.com | | | /triggers/dCDN-B/456 | | | | | [ ]--+ | | [ ] | (7.1) | | [ ]<-+ [ ]--+ | | (7.2) [ ] | | | [ ]<-+ | | | . . . . . . . . . | | (8) GET | | | https://dcdn-c.example.com | | | /triggers/dCDN-B/456 | | [ ]--------------------------->[ ] | | [ ] | | (9) HTTP 200 [ ] | | Trigger Status Resource [ ] | [ ]<---------------------------[ ] | | | . . . . . . . . . | (10) GET | | | https://dcdn-b.example.com | | | /triggers/uCDN-A/123 | | [ ]--------------------------->[ ] | | [ ] | | (11) HTTP 200 [ ] | | Trigger Status Resource [ ] | [ ]<---------------------------[ ] | ]]>

The steps in are as follows: The uCDN-A triggers an action in the dCDN-B by POSTing a CI/T Command to a collection of Trigger Status Resources "https://dcdn-b.example.com/triggers/uCDN-A". This URL was given to the uCDN-A when the CI/T interface was established. The dCDN-B authenticates the request, validates the CI/T Command, and, if it accepts the request, creates a new Trigger Status Resource. The dCDN-B responds to the uCDN-A with an HTTP 201 response status and the location of the Trigger Status Resource. The dCDN-B triggers the action in the dCDN-C by POSTing a CI/T Command to a collection of Trigger Status Resources "https://dcdn-c.example.com/triggers/dCDN-B". This URL was given to the dCDN-B when the CI/T interface was established. The dCDN-C authenticates the request, validates the CI/T Command, and, if it accepts the request, creates a new Trigger Status Resource. The dCDN-C responds to the dCDN-B with an HTTP 201 response status and the location of the Trigger Status Resource. The dCDN-C acts upon the CI/T Command. However, the command fails at dCDN-C as, for example, the Trigger Specification contains an "action type" that is not supported by dCDN-C. dCDN-C's action is depicted by 7.2 in the diagram, while 7.1 shows dCDN-B acting on its own command. The dCDN-B queries, possibly repeatedly, the Trigger Status Resource in dCDN-C. The dCDN-C responds with the Trigger Status Resource, describing the progress or results of the CI/T Trigger Command. In the described flow, the returned Status is "failed", with an Error.v2 Description Object holding "eunsupported" Error Code reflecting the status response. The uCDN-A queries, possibly repeatedly, the Trigger Status Resource in dCDN-B. The dCDN-B responds with the Trigger Status Resource, describing the progress or results of the CI/T Trigger Command. In the flow described above, the returned Status is "failed", and the "eunsupported" error received in the trigger status resource from dCDN-C is propagated along with dCDN-C PID by adding it to the errors array in dCDN-B's own status resource to be sent back to the originating uCDN-A.

The CI/T Create Trigger Command, CI/T Modify Trigger Command, Trigger Status Resources, and Trigger Collections, as well as their properties, are encoded using JSON, as defined in Sections , , , and , respectively. They MUST use the MIME media type "application/cdni", with parameter "ptype" values as defined below and in . Names in JSON are case-sensitive. The names and literal values specified in the present document MUST always use lowercase. JSON types, including "object", "array", "number", and "string", are defined in . Unrecognized name/value pairs in JSON objects SHOULD NOT be treated as an error by either the uCDN or dCDN. They SHOULD be ignored during processing and passed on by the dCDN to any further dCDNs in a cascade.

The top-level objects defined by the CI/T interface are described in this section. The encoding of values used by these objects is described in .

CI/T Create Trigger Command, which is used to create a new trigger, MUST use a MIME media type of "application/cdni; ptype=ci-trigger-command.create.v2". A CI/T Create Trigger Command is encoded as a JSON object containing the following name/value pairs: Description: A specification of the trigger action and a set of targets upon which to act. Value: A Trigger.v2 Specification, as defined in . Mandatory: Yes. Description: The CDN PIDs of CDNs that have already issued the CI/T Command to their dCDNs. Value: A non-empty JSON array of JSON strings, where each string is a CDN PID as defined in . Mandatory: No.

CI/T Modify Command, which is used to modify an existing trigger, MUST use a MIME media type of "application/cdni; ptype=ci-trigger-command.modify.v2". A CI/T Modify Trigger Command is encoded as a JSON object containing the following name/value pairs: Description: An updated specification of the trigger action and a set of targets upon which to act. Value: A Trigger.v2 Specification, as defined in . Mandatory: No, but at least one of "specs" and "desired-status" should be set. Description: The target status for an existing trigger as defined in Value: JSON string. Mandatory: No, but at least one of "specs" and "desired-status" should be set.

Trigger Status Resources MUST use a MIME media type of "application/cdni; ptype=ci-trigger-status.v2". A Trigger Status Resource is encoded as a JSON object containing the following name/value pairs: Description: The Trigger Specification POSTed in the body of the CI/T Command. Note that this need not be a byte-for-byte copy. For example, in the JSON representation the dCDN may re-serialize the information differently. Value: A Trigger.v2 Specification, as defined in . Mandatory: Yes. Description: The time at which the CI/T Command was received by the dCDN. The time is determined by the dCDN; there is no requirement to synchronize clocks between interconnected CDNs. Value: Absolute Time, as defined in . Mandatory: Yes. Description: The time at which the Trigger Status Resource was last modified. The time is determined by the dCDN; there is no requirement to synchronize clocks between interconnected CDNs. Value: Absolute Time, as defined in . Mandatory: Yes. Description: The estimate of the time at which the dCDN expects to complete the activity. Time is determined by the dCDN; there is no requirement to synchronize clocks between interconnected CDNs. Value: Absolute Time, as defined in . Mandatory: No. Description: Current status of the triggered activity. Value: Trigger Status, as defined in . Mandatory: Yes. Description: A human-readable explanation for the object status. Value: A JSON string, the human-readable status reason. Mandatory: No. Description: Descriptions of errors that have occurred while processing a Trigger Command. Value: An array of Error.v2 Descriptions, as defined in . An empty array is allowed and is equivalent to omitting "errors" from the object. Mandatory: No. Description: List of objects derived by dCDN when processing a Trigger Command. Value: An array of ObjectList objects. dCDN SHOULD provide the list of objects it used as input for processing of Trigger Command with , provided that dCDN advertised support for extended status. An empty array is allowed and is equivalent to omitting "objects" from the Trigger Status. This field is intended to provide the list of all objects used in processing. The objects that failed to process SHOULD be specified using the Error.v2 Description resource. Mandatory: No.

Trigger Collections MUST use a MIME media type of "application/cdni; ptype=ci-trigger-collection". A Trigger Collection is encoded as a JSON object containing the following name/value pairs: Description: Links to Trigger Status Resources in the collection. Value: A JSON array of zero or more URLs, represented as JSON strings. Mandatory: Yes. Description: The length of time for which the dCDN guarantees to keep a completed Trigger Status Resource. After this time, the dCDN SHOULD delete the Trigger Status Resource and all references to it from collections. Value: A JSON number, which must be a positive integer, representing time in seconds. Mandatory: Yes, in the collection of all Trigger Status Resources if the dCDN deletes stale entries. If the property is present in the filtered collections, it MUST have the same value as in the collection of all Trigger Status Resources. Description: Array of all objects. Value: An array of JSON-encoded FilteredCollectionStatusLink objects. Mandatory: Mandatory in the collection of all Trigger Status Resources, if the dCDN implements the filtered collections. Otherwise, optional. Description: Array of all objects. Value: An array of JSON-encoded FilteredCollectionLabelLink objects. Mandatory: Mandatory in the collection of all Trigger Status Resources, if the dCDN implements the filtered collections. Otherwise, optional. Description: Array of all Trigger Status objects in the collection. Should be returned only when an extended trigger collection view is requested as described in . Value: An array of JSON-encoded Trigger Status objects. Mandatory: No. The "all-triggers" SHOULD only be used by dCDN that supports and advertises the appropriate extended status for trigger collections (see for details). Description: The CDN PID of the dCDN. Value: A JSON string, the dCDN's CDN PID, as defined in . Mandatory: Only in the collection of all Trigger Status Resources, if the dCDN implements the filtered collections. Optional in the filtered collections (the uCDN can always find the dCDN's cdn-id in the collection of all Trigger Status Resources, but the dCDN can choose to repeat that information in its implementation of filtered collections).

The Filtered Collections by Status Link object represents a link to a filtered collection per . It is encoded as a JSON object containing the following name/value pairs: Description: Trigger Status matching the filtered collection. Value: A Trigger Status, as defined in . Mandatory: Yes. Description: Filtered collection URL corresponding to the status. Value: A URL represented as a JSON string. Mandatory: Yes.

The Filtered Collections by Label Link object represents a link to a filtered collection per . It is encoded as a JSON object containing the following name/value pairs: Description: Trigger Label matching the filtered collection. Value: A Trigger Label, as defined in . Mandatory: Yes. Description: Filtered collection URL corresponding to the label. Value: A URL represented as a JSON string. Mandatory: Yes.

This section defines the values that can appear in the top-level objects described in and their encodings.

A Trigger.v2 Specification is encoded as a JSON object containing the following name/value pairs: An unrecognized name/value pair in the Trigger Specification object contained in a CI/T Command SHOULD be preserved in the Trigger Specification of any Trigger Status Resource it creates. Note that the preferred method for extending the CI/T capabilities is by defining new related trigger specs and/or trigger extensions, rather than adding new properties to the Trigger.v2 object. Description: Defines the type of the CI/T Trigger Action. Value: Trigger Action Type, as defined in . Mandatory: Yes. Description: Array of trigger specs representing the trigger's targets. Value: Array of GenericTriggerSpec objects (see ). Mandatory: Yes. Furthermore, the list MUST NOT be empty. Description: Array of trigger extensions. Value: Array of GenericTriggerExtension objects (see ). Mandatory: No. The default is no extensions. Description: Array of trigger labels. Value: Array of Trigger Labels (see ). Mandatory: No. The default is no labels.

A "trigger.v2" object, as defined in , includes an array of trigger spec objects. Each trigger spec object contains properties that are used as trigger target selection directives for the dCDN when executing the trigger command, e.g., content URLs or metadata URI patterns. Each such CDNI Trigger Spec is a specialization of a CDNI GenericTriggerSpec object. The GenericTriggerSpec object abstracts the basic information required for trigger distribution from the specifics of any given property (i.e., property semantics, enforcement options, etc.). The semantics of the Trigger Specs list is additive, i.e., the trigger applies to any object matching one of the listed specs.

A GenericSpecObject object is a wrapper for managing individual CDNI Trigger specs in an opaque manner. It is encoded as a JSON object containing the following name/value pairs: Description: Case-insensitive CDNI Trigger subject. Value: String containing the type of the subject matching the generic-trigger-spec-value property, such as "content" or "metadata" as defined in . Mandatory: Yes. Description: Case-insensitive CDNI Trigger spec type. Value: String containing the spec type of the object contained in the generic-trigger-spec-value property (see table in ). Mandatory: Yes. Description: A CDNI Trigger spec object. Value: Defined by the value of the generic-trigger-spec-type property. Mandatory: Yes. The structure of a JSON serialized GenericTriggerSpec object, containing a specific trigger spec is illustrated below:

, "generic-trigger-spec-value": { }, "generic-trigger-spec-subject": } ]]>

A "trigger.v2" object, as defined in includes an optional array of trigger extension objects. A trigger extension contains properties that are used as directives for the dCDN when executing the trigger command, e.g., location policies, time policies, and so on. Each such CDNI Trigger extension is a specialization of a CDNI GenericTriggerExtension object. The GenericTriggerExtension object abstracts the basic information required for trigger distribution from the specifics of any given property (i.e., property semantics, enforcement options, etc.). All trigger extensions are optional, and it is thus the responsibility of the extension specification to define a consistent default behavior for extensions supported by a dCDN when not specified by the uCDN.

The trigger enforcement options concept is in accordance with the metadata enforcement options as defined in Section 3.2 of . The GenericTriggerExtension 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 execute the trigger command. If the extension is not mandatory-to-enforce, then that GenericTriggerExtension object can be safely ignored and the trigger command can be processed in accordance with the rest of the CDNI Trigger spec. Although a CDN MUST NOT execute a trigger command if a mandatory-to-enforce extension cannot be enforced, it could still be safe to redistribute that trigger (the "safe-to-redistribute" property) to another CDN without modification. For example, in the cascaded CDN case, a transit CDN (tCDN) could convey mandatory-to-enforce trigger extension to a dCDN. For a trigger extension that does not require customization or translation (i.e., trigger extension that is safe-to-redistribute), the data representation received off the wire MAY be stored and redistributed without being understood or supported by the tCDN. However, for trigger extension that requires translation, transparent redistribution of the uCDN trigger values might not be appropriate. Certain trigger extensions can be safely, though perhaps not optimally, redistributed unmodified. For example, pre-position command might be executed in suboptimal times for some geographies if transparently redistributed, but it might still work. Redistribution safety MUST be specified for each GenericTriggerExtension listed. If a CDN does not understand or support a given GenericTriggerExtension object that is not safe-to-redistribute, the CDN MUST set the "incomprehensible" flag to true for that GenericTriggerExtension object before redistributing it. The "incomprehensible" flag signals to a dCDN that trigger metadata was not properly transformed by the tCDN. A CDN MUST NOT attempt to execute a trigger with an extension that has been marked as "incomprehensible" by a uCDN. tCDNs MUST NOT change the value of mandatory-to-enforce or safe-to-redistribute when propagating a trigger to a dCDN. Although a tCDN can set the value of "incomprehensible" to true, a tCDN MUST NOT change the value of "incomprehensible" from true to false. describes the action to be taken by a tCDN for the different combinations of mandatory-to-enforce ("MtE") and safe-to-redistribute ("StR") properties when the tCDN either does or does not understand the trigger extension object in question: MtE StR Extension object understood by tCDN Trigger action False True True Can execute and redistribute. False True False Can execute and redistribute. False False False Can execute. MUST set "incomprehensible" to true when redistributing. False False True Can execute. Can redistribute after transforming the trigger extension (if the CDN knows how to do so safely); otherwise, MUST set "incomprehensible" to true when redistributing. True True True Can execute and redistribute. True True False MUST NOT execute but can redistribute. True False True Can execute. Can redistribute after transforming the trigger extension (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 and "incomprehensible" ("Incomp") properties, when the dCDN either does or does not understand the trigger extension object in question: MtE Incomp Extension object understood by dCDN Trigger action False False True Can execute. False True True Can execute but MUST NOT interpret/apply any trigger extension marked as "incomprehensible". False False False Can execute. False True False Can execute but MUST NOT interpret/apply any trigger extension marked as "incomprehensible". True False True Can execute. True True True MUST NOT execute. True False False MUST NOT execute. True True False MUST NOT execute.

A GenericTriggerExtension object is a wrapper for managing individual CDNI Trigger extensions in an opaque manner. It is encoded as a JSON object containing the following name/value pairs: Description: Case-insensitive CDNI Trigger extension object type. Value: String containing the CDNI Extension Type of the object contained in the "generic-trigger-extension-value" property (see table in ). Mandatory: Yes. Description: CDNI Trigger extension object. Value: Defined by the value of the "generic-trigger-extension-type" property above. Mandatory: Yes. Description: Flag identifying whether or not the enforcement of this trigger extension is mandatory. Value: Boolean. Mandatory: No. The default is to treat the trigger extension as mandatory to enforce (i.e., a value of True) Description: Flag identifying whether or not this trigger extension can be safely redistributed without modification, even if the CDN fails to understand the extension. Value: Boolean. Mandatory: No. The default is to allow transparent redistribution (i.e., a value of True). Description: Flag identifying whether or not any CDN in the chain of delegation has failed to understand and/or failed to properly transform this trigger extension object. Note: This flag only applies to trigger extension objects whose "safe-to-redistribute" property has a value of False. Value: Boolean. Mandatory: No. The default is comprehensible (i.e., a value of False). The structure of a JSON serialized GenericTriggerExtension object containing a specific trigger extension object is illustrated below:

, "generic-trigger-extension-value": { }, "mandatory-to-enforce": , "safe-to-redistribute": , "incomprehensible": } ]]>

A JSON number, seconds since the UNIX epoch (00:00:00 UTC on 1 January 1970).

An Error.v2 Description is used to report the failure of a CI/T Command or failure in the activity it triggered. It is encoded as a JSON object with the following name/value pairs: Value: Error Code, as defined in . Mandatory: Yes. Description: A human-readable description of the error. Value: A JSON string, the human-readable description. Mandatory: No. Description: Array of trigger spec objects from the corresponding "specs" array at the Trigger Specification. Only those specs to which the error applies are listed. Value: Array Trigger Specifications, as defined in , where each spec object MUST be exactly as they appear in the request. Mandatory: Yes. Description: Array of trigger extension objects copied from the corresponding "extensions" array from the Trigger Specification. Only those extensions to which the error applies are included, but those extensions MUST be exactly as they appear in the request. Value: Array of GenericTriggerExtension objects, where each extension object is copied from the "extensions" array values in the Trigger Specification. Mandatory: No. The "extensions" array SHOULD be used only if the error relates to extension objects. Property omission should be interpreted as "the error is not related to any extension". Description: The CDN PID of the CDN where the error occurred. The "cdn-id" property is used by the originating uCDN or by the propagating dCDN in order to distinguish in which CDN the error occurred. Value: A non-empty JSON string, where the string is a CDN PID as defined in Section Mandatory: Yes. The dCDN may use its own CDN PID if it does not want to expose the CDN PIDs of dCDNs. Description: List of objects that failed to be processed during execution of a Trigger Command. Value: An array of ObjectList objects. dCDN SHOULD provide the list of objects that it failed to process during execution of a Trigger Command with , provided that dCDN advertised support for extended status. Mandatory: No. An empty array is allowed and is equivalent to omitting "objects" from the Error.v2 Description. Example of a JSON serialized Error.v2 Description object reporting a malformed object list :

Example of a JSON serialized Error.v2 Description object reporting an unsupported extension object:

", "specs": [ { "trigger-subject": "content", "generic-trigger-spec-type": "urls", "generic-trigger-spec-value": { "urls": [ "https://www.example.com/a/b/c/1", "https://www.example.com/a/b/c/2" ] } } ], "extensions": [ { "generic-trigger-extension-type": , "generic-trigger-extension-value": { } } ], "cdn": "AS64500:0" } ] } ]]>

Trigger Status describes the current status of the triggered activity. It MUST be one of the JSON strings in the following table: JSON String Description pending The CI/T Trigger Command has not yet been acted upon. active The CI/T Trigger Command is currently being acted upon. complete The CI/T Trigger Command completed successfully. processed The CI/T Trigger Command has been accepted, and no further status update will be made (can be used in cases where completion cannot be confirmed). failed The CI/T Trigger Command could not be completed. cancelling Processing of the CI/T Trigger Command is still in progress, but the CI/T Trigger Command has been cancelled by the uCDN. cancelled The CI/T Trigger Command was cancelled by the uCDN. Along with the Trigger Status, the Trigger Status Resource object includes a Status Reason property, allowing the dCDN to provide additional information for the trigger status. For example, the dCDN may indicate that the trigger status is "pending" due to one of the execution prerequisites not being fulfilled. Such a prerequisite may be specified via one of the extensions.

This type is used by the dCDN to report failures in trigger processing. All Error Codes MUST be registered in the IANA "CDNI CI/T Error Codes" registry (see ). Unknown Error Codes MUST be treated as fatal errors, and the request MUST NOT be automatically retried without modification. The following Error Codes are defined by this document and MUST be supported by an implementation of the CI/T interface utilizing the ci-trigger-command.trigger.v2 and the ci-trigger-status.v2 objects. [RFC Editor: Please replace RFCthis with the published RFC number for this document.] Error Code Description Registration emeta The dCDN was unable to acquire and/or is not in possession of metadata required to fulfill the request. RFCthis econtent The dCDN was unable to acquire content (CI/T "preposition" commands only). RFCthis eperm The uCDN does not have permission to issue the CI/T Command (for example, the data is owned by another CDN). RFCthis ereject The dCDN is not willing to fulfill the CI/T Command (for example, a "preposition" request for content at a time when the dCDN would not accept Request Routing requests from the uCDN). RFCthis ecdn An internal error in the dCDN or one of its dCDNs. RFCthis ecancelled The uCDN cancelled the request. RFCthis eunsupported The Trigger Specification contained an "action type" that is not supported by the dCDN. No action was taken by the dCDN other than to create a Trigger Status Resource in state "failed". RFCthis espec An error occurred while parsing a generic trigger spec, or that the specific trigger spec is not supported by the CDN. RFCthis esubject An error occurred while parsing a trigger subject, or that the specific trigger subject is not supported by the CDN. RFCthis eextension An error occurred while parsing a generic trigger extension, or that the specific extension is not supported by the CDN. RFCthis

This type is used by uCDN to indicate how to interpret URLs referenced by trigger specs that use URLs, such as , , and . One option for uCDN to use in Trigger Commands is published URLs, which are used by end users. When using this URL type, uCDN MUST provide configuration metadata objects related to these URLs before creating a trigger option referencing these URLs. When this is not the case, dCDN MUST return the error code "emeta". When processing published URLs in "preposition" Trigger Action, dCDN MUST invoke processing of metadata objects it would have invoked in content acquisition to satisfy an end-user request, e.g. SourceMetadata (see Section 4.2.1 of . Another type of URL in common use is a private URL, which is based on cache keys that are dynamically constructed via lightweight processing of various properties of the HTTP request and/or response. As an example, an origin might specify a cache key as a value returned in a specific HTTP response header. As an example, uCDN may prefer to use such private URLs in "purge" or "invalidate" Trigger Actions to simplify processing. dCDNs implementing the CI/T Interface MUST support the "published" URL type. dCDN MAY support the additional "private" URL type. In this case, dCDN SHOULD advertise the private URL type support via FCI using . If the private URL is not supported by dCDN, it SHOULD reject the Trigger Command using "eunsupported" Error Code. If both URL types are supported by dCDN, uCDN MUST use only one URL type in each Trigger Command. The following URL types are defined by this document and MUST be supported by the implementation of the CI/T interface: [RFC Editor: Please replace RFCthis with the published RFC number for this document.] URL Type Description Registration published Published URL used by end users to access content RFCthis private Private URLs used by dCDN to look up content objects in cache RFCthis

ObjectList is a metadata object describing lists of objects that can be used in the context of CI/T v2 trigger spec, trigger status resources and other contexts as required. The ObjectList object can either embed the lists of objects or point to external URL(s) that hold such lists. ObjectList allows the specification of an object list type, providing instructions on the interpretation of the object list format. ObjectLists MAY be recursive, i.e. including references to secondary manifests, including references to HLS, MPEG-DASH or MSS manifests as well as additional JSON-encoded ObjectLists, etc. The party consuming the object list MUST parse all recursions based on the object list type property. When doing so, the consuming party should also detect potential loops when the descendant ObjectList points back to the parent ObjectList. In the case of uCDN accessing ObjectList objects referencing external URLs published by dCDN, both parties should comply with the CI/T interface security requirements (see for details). When dCDN accesses external URLs referenced by ObjectLists supplied by uCDN, for example as part of Trigger Spec, the dCDN MUST match these URLs with source metadata objects, published by uCDN, such as SourceMetadata objects specified in Section 4.2.1 of , and use these metadata objects for content acquisition if a match was found. ObjectLists MAY combine regular objects and secondary ObjectLists in the same object. Please note that when embedding non-JSON object lists directly in ObjectList, absolute URLs MUST be provided at all times and the text SHOULD be encoded in accordance with the JSON grammar specification , including explicit newline encoding. When the uCDN accesses ObjectList metadata resources published by the uCDN, the same interface authentication and authorization requirements would apply, as when accessing the interface itself. ObjectList is encoded as an array of per-object records in JSON format as follows: External HLS manifest:

External object list in text format:

List of external manifests and objects of mixed types:

Embedded JSON-encoded object list:

Embedded HLS manifest:

The ObjectList properties are as follows: Description: List of objects in one of the recognized formats. Value: JSON String. Mandatory: No. Either "data" or "href" MUST be set. Description: URL pointing to an external object list or object in one of the recognized formats. Value: A URL represented as a JSON String Mandatory: No. Either "data" or "href" MUST be set. Description: Object list type to be used when parsing and interpreting this object list. By default, each record in the list is assumed to represent an object that does not require additional processing. Value: ObjectListType (see ). Mandatory: Yes.

ObjectListType objects are used to specify the registered type of ObjectList objects (see ), used in Trigger Spec, Trigger Status and Error.v2 Description objects. The following table defines the initial ObjectListType JSON string values JSON string Description Specification Protocol Specification hls HTTP Live Streaming RFCthis RFC 8216 mss Microsoft Smooth Streaming RFCthis MSS dash Dynamic Adaptive Streaming over HTTP (MPEG-DASH) RFCthis MPEG-DASH json JSON serialized object list RFCthis JSON text Object list in text format RFCthis Text [RFC Editor: Please replace RFCthis with the published RFC number for this document.]

This ObjectList type specifies a collection of objects encoded in JSON format, where each entry is encoded as an ObjectEntry object. The entries in the JSON object list MAY have an object list type specified, allowing for a recursive object list structure.

The text object list type specifies a collection of files in text encoding, each line specifying an object URI.Unlike the JSON object list, the text-based object list will not support a recursive object list structure and every object specified in it SHOULD be downloaded without additional processing.

ObjectEntry is a metadata object describing an object and its associated metadata, to be used in JSON-encoded ObjectList objects. The following is an example of JSON serialized ObjectEntry objects: The ObjectEntry properties are as follows: Description: Object URL Value: A URL represented as a JSON string. Mandatory: Yes. Description: ObjectList type to be used when processing this object. By default, ObjectEntry object is assumed to represent an object and does not require additional processing. Value: ObjectListType (see ). Mandatory: No. Description: Object size, in bytes. Can be used to decide to download the object based on size. For example, dCDN may ignore objects that are too small or too large. Value: Integer. Mandatory: No.

A JSON string. Labels SHOULD be unique per trigger.

The objects defined below are intended to be used in the GenericTriggerSpec object's generic-trigger-spec-value field as defined in Section . As such all these trigger specs are registered in the IANA "CDNI CI/T Trigger Specs" registry (see ).

The "urls" spec type allows the uCDN to manage uCDN content or metadata objects held by the dCDN based on the objects' URLs. The URLs spec is encoded as a JSON object containing the following name/value pairs: Description: An array of URLs over which the trigger MUST be executed. Value: A JSON array of URLs represented as JSON strings. Mandatory: Yes. Description: Type of URL used. Value: URL Type as defined in . Mandatory: No. When omitted or empty, "published" URL type is assumed. Below is an example of a JSON serialized URLs spec object, matching the metadata at metadata.example.com/a/b/c.

The "ccids" spec type allows the uCDN to specify the Content Collection IDentifier (CCID) of content to which the trigger applies. The CCID is a grouping of content as defined by . The "ccids" spec type is valid only for the content spec subject (see ). CCIDs spec is encoded as a JSON object containing the following name/value pairs: Description: An array of Content Collection IDentifiers over which the trigger MUST be executed. Value: A JSON array of strings, where each string is a Content Collection IDentifier. Mandatory: Yes.

The "uri-pattern-match" spec type allows the uCDN to manage uCDN content or metadata objects held by the dCDN based on the objects' URI pattern. The value is a UriPatternMatch object, as defined in .

A UriPatternMatch consists of a string pattern to match against a URI, and flags describing the type of match. It is encoded as a JSON object containing the following name/value pairs: Description: A pattern for URI matching. Value: A JSON string representing the pattern. The pattern can contain the wildcards "*" and "?", where "*" matches any sequence of pchar 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. Mandatory: Yes. Description: Flag indicating whether or not case-sensitive matching should be used. Value: One of the JSON values "true" (the matching is case sensitive) or "false" (the matching is case insensitive). Mandatory: No; default is "false", i.e., a case-insensitive match. Description: Flag indicating whether to include the query part of the URI when compared against the pattern. Value: One of the JSON values "true" (the full URI, including the query part, should be compared against the given pattern) or "false" (the query part of the URI should be dropped before comparison with the given pattern). Mandatory: No; default is "false". The query part of the URI should be dropped before comparison with the given pattern. Description: Type of URLs to match. Value: URL Type as defined in . Mandatory: No. When omitted or empty, "published" URL type is assumed. Example of case-sensitive prefix match against "https://www.example.com/trailers/":

The "uri-regex-match" spec type allows the uCDN to manage content or metadata objects held by the dCDN based on the objects' URI regex.

A RegexMatch consists of a regular expression string a URI is matched against, and flags describing the type of match. It is encoded as a JSON object with the following properties: Description: A regular expression for URI matching. Value: A regular expression to match against the URI, i.e., against the path-absolute and the query string parameters . The regular expression string MUST be compatible with POSIX Section 9 Extended Regular Expressions. This regular expression MUST be evaluated in the POSIX locale (POSIX Section 7.2). Note: Because '\' has a special meaning in JSON as the escape character within JSON strings, the regular expression character '\' MUST be escaped as '\\'. Mandatory: Yes. Description: Flag indicating whether or not case-sensitive matching should be used. Value: JSON boolean. Either "true" (the matching is case-sensitive) or "false" (the matching is case insensitive). Mandatory: No; default is "false", i.e., a case-insensitive match. Description: Flag indicating whether to include the query part of the URI when compared against the regex. Value: JSON Boolean. Either "true" (the full URI, including the query part, should be compared against the regex) or "false" (the query part of the URI should be dropped before comparison with the given regex). Mandatory: No; default is "false". The query part of the URI MUST be dropped before comparison with the given regex. This makes the regular expression simpler and safer for cases in which the query parameters are not relevant for the match. Description: Type of URLs to match against. Value: URL Type as defined in . Mandatory: No. When omitted or empty, "published" URL type is assumed. Example of a case-sensitive, no query parameters, regex match against:

This regex matches URLs of the domain "video.example.com" where the path structure is /(single lower case letter)/(name-of-title)/(single digit between 1 to 7)/(index.m3u8 or a 3 digit number with ts extension). For example:

The "objectlist" spec type allows the uCDN to manage content held by the dCDN based on structured object lists. The Object List spec type is valid only for the content spec subject (see ). An object list is encoded as an ObjectList object.

The objects defined below are intended to be used in the GenericTriggerExtension object's generic-trigger-extension-value field as defined in , and their generic-trigger-extension-type property MUST be set to the appropriate Extension Type as defined in .

A content operation may be relevant for a specific geographical region or need to be excluded from a specific region. In this case, the trigger should be applied only to parts of the network that are either "included" or "not excluded" by the location policy. Note that the restrictions here are on the cache location rather than the client location. The LocationPolicy object defines which CDN or cache locations for which the trigger command is relevant. Example use cases: Pre-position: Certain contracts allow for pre-positioning or availability of contracts in all regions except for certain excluded regions in the world, including caches. For example, some content cannot ever knowingly touch servers in a specific country, including cached content. Therefore, these regions MUST be excluded from a pre-positioning operation. Purge: In certain cases, content may have been located on servers in regions where the content must not reside. In such cases, a purge operation to remove content specifically from that region is required. Object specification: Description: An Access List that allows or denies (blocks) the trigger execution per cache location. Value: Array of LocationRule objects (see Section 4.2.2.1 of ). Mandatory: Yes. Description: Type of URL used in the ObjectList(s). Value: URL Type as defined in . Mandatory: No. When omitted or empty, the "published" URL type is assumed. If a location policy object is not listed within the trigger command, the default behavior is to execute the trigger in all available caches and locations of the dCDN. The trigger command is allowed, or denied, for a specific cache location according to the action of the first location whose footprint matches that cache's location. If two or more footprints overlap, the first footprint that matches against the cache's location determines the action a CDN MUST take. If the "locations" property is an empty list or if none of the listed footprints match the location of a specific cache location, then the result is equivalent to a "deny" action. The following is an example of a JSON serialized generic trigger extension object containing a location policy object that allows the trigger execution in the US but blocks its execution in Canada:

A uCDN may wish to perform content management operations on the dCDN on a specific schedule. The TimePolicy extension allows the uCDN to instruct the dCDN to execute the trigger command in a desired time window. For example, a content provider that wishes to pre-populate a new episode at off-peak time so that it would be ready on caches at prime time when the episode is released for viewing. A scheduled operation enables the uCDN to direct the dCDN in what time frame to execute the trigger. A uCDN may wish to schedule a trigger such that the dCDN will execute it in local time, as it is measured in each region. For example, a uCDN may wish the dCDN to pull the content at off-peak hours, between 2AM-4AM, however, as a CDN is distributed across multiple time zones, the UTC definition of 2AM depends on the actual location. We define two alternatives for localized scheduling: Regional schedule: When used in conjunction with the Location Policy defined in , the uCDN can trigger separate commands for different geographical regions, for each region using a different schedule. This allows the uCDN to control the execution time per region. Local Time schedule: We introduce a "local time" version for Internet timestamps that follows the notation for local time as defined in Section 4.2.2 of . When local time is used, that dCDN SHOULD execute the triggers at different absolute times, according to the local time of each execution location. Object specification: Description: A UNIX epoch time window in which the trigger SHOULD be executed. Value: TimeWindow object using UNIX epoch timestamps (see Section 4.2.3.2 of ). Mandatory: No, but exactly one of "unixEpochWindow" or "utcWindow" MUST be present. Description: A UTC time window in which the trigger SHOULD be executed. Value: UTCWindow object as defined in . Mandatory: No, but exactly one of "unixEpochWindow" or "utcWindow" MUST be present. If a time policy object is not listed within the trigger command, the default behavior is to execute the trigger in a time frame most suitable to the dCDN taking under consideration other constraints and / or obligations. Example of a JSON serialized generic trigger extension object containing a time policy object that schedules the trigger execution to a window between 09:00 01/01/2000 UTC and 17:00 01/01/2000 UTC, using the "unix-time-window" property:

A UTCWindow object describes a time range in UTC or UTC and a zone offset that can be applied by a TimePolicy. It is encoded as a JSON object containing the following name/value pairs: Description: The start time of the window. Value: Internet date and time as defined in . Mandatory: No. but at least one of "start" or "end" MUST be present and non-empty. Description: The end time of the window. Value: Internet date and time as defined in . Mandatory: No. but at least one of "start" or "end" MUST be present and non-empty. Example JSON serialized UTCWindow object that describes a time window from 02:30 01/01/2000 UTC to 04:30 01/01/2000 UTC:

Example JSON serialized UTCWindow object that describes a time window in New York time zone offset UTC-05:00 from 02:30 01/01/2000 to 04:30 01/01/2000:

Unless specified otherwise, dCDN is at liberty to decide how to choose trigger commands for execution from all pending commands, whether to process trigger commands sequentially or in parallel, immediately upon acceptance, or with a delay in batches. A uCDN may wish to control trigger processing in more detail, including the order of execution, dependencies, and concurrency. Example use cases: Priority: uCDN may have multiple trigger commands in "pending" and/or "active" mode. For example, trigger commands with policy constraints, a large number of content objects affected, or other dCDN business logic may take a long time to execute. uCDN may wish to prescribe the order in which dCDN picks up its trigger commands for execution from the "pending" queue, by indicating a relative priority of each trigger. The priority would affect the selection of trigger commands specific to the requesting uCDN. dCDN may separately prioritize triggers from multiple uCDNs subject to its business logic. Multiple priority-related use cases exist: uCDN needs to introduce an urgent "purge" or "invalidate" trigger into an existing queue of trigger commands to correct wrong versions of content objects published by it uCDN needs to indicate which content objects should be prepositioned, purged or invalidated first, for example prepositioning newer released content before prepositioning updates to an existing catalog Pre-requisite: In some cases, uCDN may wish to indicate what trigger commands should be processed and completed before another trigger command is processed. For example, uCDN may want to rectify incorrectly published content by purging content objects and then prepositioning them again. In this case, uCDN may want the preposition trigger command to be processed only after the purge trigger command has been processed because concurrent processing of these triggers may cause the new version of these content objects to be purged. Alternatively, uCDN may wish to condition the execution of purge or invalidation triggers upon the completion or cancellation of long-running preposition triggers to avoid race conditions that would result from processing these in parallel. The prerequisite requirement implies that a previous trigger reaches one of the following states: "complete" or "processed" for successful completion "failed" for failed processing "cancelled" for completion of cancellation Urgency: uCDN may wish to indicate that dCDN should process a trigger command without delay. This requirement is separate and additional to priority, as priority indicates the order in which triggers should be processed, yet does not prescribe how soon each trigger should be executed. dCDN MAY reject such requests for urgent processing using "ereject" error code. This can happen due to dCDN internal business logic (e.g. batch-driven purge and invalidation), or due to dependencies on other triggers that could not be completed by dCDN immediately. In such a case uCDN should either modify the request by removing prerequisites or cancel such pending triggers before re-trying the request. uCDN may combine multiple options in the same trigger command. dCDN should consider the following when processing such commands: dCDN MUST reject triggers that are dependent on other pending triggers with lower priority to prevent deadlocks. When introducing an urgent trigger uCDN SHOULD indicate a priority that is equal to or higher than the highest priority among the pending triggers that belong to the same uCDN. dCDN MUST reject urgent triggers that have lower priority than other pending triggers of the same uCDN. dCDN MUST reject an urgent trigger that has pending triggers as its prerequisite. dCDN MAY reject an urgent trigger that has triggers in an "active" or "cancelling" state as its prerequisite, such as when such triggers are deemed to take a long time to complete or cancel. When combining ExtensionPolicy with , TimePolicy governs the time window when the trigger can execute, while ExecutionPolicy controls the order of trigger execution within their respective windows. The following error conditions should be considered by dCDN: When a trigger is marked urgent, but its TimePolicy extension doesn't allow immediate processing, it should be rejected by dCDN. When a trigger has a TimePolicy extension and is also dependent on another trigger with a TimePolicy extension, that specifies an execution window (directly or via a chain of dependency) that doesn't start until after the depending trigger's execution window ends, such a trigger should be rejected. The ExtensionPolicy extension is encoded as a JSON object containing the following name/value pairs: Description: Relative weight of the trigger. When picking a trigger for execution from all pending triggers posted by each uCDN, the dCDN MUST choose the trigger with the highest priority first. Value: Integer from -100 to 100. Mandatory: No. The value defaults to zero if omitted. Description: Links to Trigger Status Resources that the current Trigger Command depends on. Indicates which triggers should fully finish processing before starting execution of the current trigger. The triggers need to be in one of the following states to be considered finished: "complete", "processed", "failed" or "cancelled". Value: A JSON array of zero or more URLs, represented as JSON strings. Mandatory: No. In case of a missing or an empty list, no dependencies are assumed. Description: Indicates whether the trigger should be immediately moved to the "active" state upon acceptance. In the absence of this flag, the dCDN is at liberty to choose the time for trigger execution, e.g., batch processing. Value: Boolean. Mandatory: No. The default is to handle the Trigger Command as not urgent. The following is an example of a JSON serialized generic extension trigger object containing an execution policy object that specifies trigger priority of 100, marks Trigger Command as urgent and makes the Trigger Command execution dependent on the completion of the previous Trigger Commands:

This section covers the FCI objects required for the advertisement of the specs, extensions, and properties introduced in this document.

The CI/T trigger endpoint capability object is used to advertise one or more CI/T interface endpoints along with CI/T interface versions supported by these endpoints. The capability type is "FCI.CITEndpoints". Version 1, as originally defined in , is the default if this capability is not explicitly declared. A CI/T Endpoints capability object is encoded as an array of JSON objects containing the following name/value pairs: Description: CI/T endpoint URI Value: A URL represented as a JSON string. Mandatory: Yes. Description: A list of CI/T versions supported by the trigger endpoint. Value: An array of JSON strings. Mandatory: Yes. Description: Array of trigger subjects supported by the trigger endpoint. Value: An array of Strings containing the type of the subject matching the generic-trigger-spec-value property, such as "content" or "metadata" as defined in . Mandatory: No. A missing or empty "trigger-subject" list means that all trigger subjects are supported by the endpoint. dCDN SHOULD advertise only one endpoint for every trigger subject and CI/T interface version pair. If more than one interface endpoint supports the same trigger subject and CI/T interface version (e.g. CI/T version 2 interface for content objects), uCDN SHOULD be able to use any of the advertised CI/T interface endpoints interchangeably.

The following shows an example of CI/T Endpoints Capability object serialization for a dCDN that supports versions 2 and 2.1 of the CI/T interface.

] }, { "capability-type": "FCI.CITEndpoints", "capability-value": { "trigger-endpoint-uri": "https://dcdn.example.com/cache-management/", "trigger-versions": [ "2", "2.1" ], "trigger-subjects": "content" }, "footprints": [ ] } ] } ]]>

The CI/T supports several trigger actions for different trigger subjects as defined in and . Additional actions, as well as subjects, may be defined in the future. The Trigger Scope capability object is used to indicate support for a Trigger Action for a subject. It further specifies the Trigger Generic Spec types that may be used for selecting the targets the triggers are applied on, along with the supported Trigger Generic Extension types. The "trigger-scope-capability" object matches the "FCI.CITScope" capability type and is encoded as a JSON object containing the following name/value pairs: Description: The supported CDNI CI/T Trigger Action. Value: A string corresponding to an entry from the "CDNI CI/T Trigger Types" registry , which corresponds to a CDNI CI/T Trigger Action. Mandatory: Yes. Description: The supported CDNI CI/T Trigger Subject. Value: A string corresponding to an entry from the "CDNI CI/T Trigger Subjects" registry , which corresponds to a CDNI CI/T Trigger Subject. Mandatory: Yes. Description: A list of supported CDNI CI/T GenericSpecObject types for Trigger Action and Subject. Value: List of strings corresponding to entries from the "CDNI CI/T Trigger Specs" registry , which corresponds to a CDNI CI/T GenericSpecObject objects. Mandatory: No. The default, in case of a missing or an empty list, MUST be interpreted as "no GenericExtensionObject types are supported". A non-empty list MUST be interpreted as containing "the only GenericExtensionObject types that are supported". Description: A list of supported CDNI CI/T GenericExtensionObject types for Trigger Action and Subject. Value: List of strings corresponding to entries from the "CDNI CI/T Trigger Extension" registry , which corresponds to a CDNI CI/T GenericExtensionObject object. Mandatory: No. The default, in case of a missing or an empty list, MUST be interpreted as "no GenericExtensionObject types are supported". A non-empty list MUST be interpreted as containing "the only GenericExtensionObject types that are supported".

The following shows an example of a JSON serialized CI/T Trigger Scope Capability object serialization for a dCDN that supports the preposition and invalidation of content, using "urls" and "ccids" Generic Spec types, with "time-policy" but only for the "preposition" action. Note that in this example, purge is not supported, and no actions involving metadata are supported either.

] } ] } ]]>

Given an object list being supported by the dCDN, the CI/T Object List Type capability object is used to indicate support for one or more Object List types listed in by the type property of the "ObjectList" object. The capability type is "FCI.CITObjectListType". Description: A list of supported ObjectList types. Value: An array of . Mandatory: No. In case of a missing or an empty list, MUST be interpreted as no ObjectList types are supported.

The following shows an example of a JSON serialized CI/T Object List Type Capability object serialization for a dCDN that supports "hls" and "dash".

] } ] } ]]>

The CI/T Private URL capability object is used to indicate support for operations on private URLs (see for details). The capability type is "FCI.CITPrivateUrlType". Description: Indicate whether private URL type is supported by dCDN. Value: Boolean. Mandatory: No. In case of missing or an empty attribtue, MUST be interpreted as no support for private URLs.

The following shows an example of a JSON serialized CI/T Private URL Type Capability object serialization for a dCDN that supports the private URL type in URL-based trigger spec types.

] } ] } ]]>

CI/T Extended Trigger Status Capability object is used to indicate support for extended trigger status. The extended trigger status is returned upon uCDN request and includes: "objects" attribute in Trigger Status object "objects" attribute in Error.v2 Description object "all-triggers" attribute in Trigger Collections object The capability type is "FCI.CITExtendedStatus". Description: List of CI/T objects that support extended attributes. Value: An array of JSON strings listing CI/T objects. Mandatory: No. By default, in case of a missing or an empty list, no extended attribute objects are supported.

The following shows an example of a JSON serialized CI/T Extended Status Type Capability object serialization for a dCDN that supports extended status in Trigger Status, Error.v2 Description and Trigger Collections objects.

] } ] } ]]>

The following subsections provide examples of different CI/T objects encoded as JSON. The discovery of the CI/T interface is out of scope of this document. In an implementation, all CI/T URLs are under the control of the dCDN. The uCDN MUST NOT attempt to ascribe any meaning to individual elements of the path. In examples in this section, the URL "https://dcdn.example.com/triggers" is used as the location of the collection of all Trigger Status Resources, and the CDN PID of the uCDN is "AS64496:1".

Examples of the uCDN triggering activity in the dCDN:

Below is an example of a CI/T "preposition" command -- a POST to the collection of all Trigger Status Resources. Note that pattern-based specs like "UriPatternMatch" and "UrisRegexMatch" are not allowed in a pre-position Trigger Specification, where the dCDN has to have a clear list of objects to obtain.

Below is an example of a CI/T "invalidate" command -- another POST to the collection of all Trigger Status Resources. This instructs the dCDN to revalidate the content at "https://www.example.com/a/index.html", as well as any metadata and content whose URLs are prefixed by "https://metadata.example.com/a/b/" using case-insensitive matching, and "https://www.example.com/a/b/" using case-sensitive matching, respectively.

In the following example, a CI/T "invalidate" command uses the Regex property to specify the range of content objects for invalidation, the command is rejected by the dCDN due to regex complexity, and an appropriate error is reflected in the status response.

} } ]]>

In the following example, a CI/T "preposition" command uses the ObjectList property to specify the full media library of a specific content. The command fails due to object list parse error and an appropriate error is reflected in the status response.

} } ]]>

Once Trigger Status Resources have been created, the uCDN can check their status as shown in the following examples.

The uCDN can fetch the collection of all Trigger Status Resources it has created that have not yet been deleted, removed or expired. After the creation of the "preposition" and "invalidate" triggers shown above, this collection might look as follows:

The filtered collections are also available to the uCDN. Before the dCDN starts processing the two CI/T Trigger Commands shown above, both will appear in the collection of pending triggers. For example:

At this point, if no other Trigger Status Resources had been created, the other filtered views would be empty. For example:

The Trigger Status Resources can also be examined for details about individual CI/T Trigger Commands. For example, for the CI/T "preposition" and "invalidate" commands from previous examples:

The uCDN SHOULD use the ETags of collections or Trigger Status Resources when polling for changes in status, as shown in the following examples:

When the CI/T Trigger Command is complete, the contents of the filtered collections will be updated along with their ETags. For example, when the two example CI/T Trigger Commands are complete, the collections of pending and complete Trigger Status Resources might look like:

The uCDN can delete completed and failed Trigger Status Resources to reduce the size of the collections, as described in . For example, to delete the "preposition" request from earlier examples:

This would, for example, cause the collection of completed Trigger Status Resources shown in the example above, to be updated to:

In the following example, a CI/T "preposition" command is using two extensions to control the way the trigger is executed. In this example, the receiving dCDN, identified as "AS64500:0", does not support the first extension in the extensions array. dCDN "AS64500:0" further distributes this trigger to another downstream CDN that is identified as "AS64501:0", which does not support the second extension in the extensions array. The error is propagated from "AS64501:0" to "AS64500:0" and the errors.v2 array reflects both errors.

", "error": "eextension", "cdn": "AS64500:0" }, { "extensions": [ { "generic-trigger-extension-type": "time-policy", "generic-trigger-extension-value": { "unix-time-window": { "start": 946717200, "end": 946746000 } }, "mandatory-to-enforce": true, "safe-to-redistribute": true } ], "description": "unrecognized extension ", "error": "eextension", "cdn": "AS64501:0" } ], "ctime": 1462351690, "etime": 1462351698, "mtime": 1462351690, "status": "failed", "trigger": { } } ]]>

All references to RFC 8007 in the IANA registries should be replaced with references to this document, apart from references associated with the following registrations: Payload Type Specification ci-trigger-command RFC 8007 ci-trigger-status RFC 8007 ci-trigger-collection RFC 8007 The IANA is requested to register the following new Payload Types in the "CDNI Payload Types" registry defined by , for use with the "application/cdni" MIME media type. Payload Type Specification ci-trigger-command.trigger.v2 RFCthis ci-trigger-command.cancel RFCthis ci-trigger-status.v2 RFCthis FCI.CITObjectsVersion RFCthis FCI.CITScope RFCthis FCI.CITObjectListType RFCthis [RFC Editor: Please replace RFCthis with the published RFC number for this document.]

Purpose: The purpose of this payload type is to distinguish version 2 of the CI/T trigger command object (and any associated capability advertisement) Interface: CI/T Encoding: see

Purpose: The purpose of this payload type is to distinguish the CI/T modify command object (and any associated capability advertisement) Interface: CI/T Encoding: see

Purpose: The purpose of this payload type is to distinguish version 2 of the CI/T status resource response object (and any associated capability advertisement) Interface: CI/T Encoding: see

Purpose: The purpose of this payload type is to distinguish FCI advertisement objects for CI/T Endpoints objects Interface: FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish FCI advertisement objects for CI/T Trigger Scope Interface: FCI Encoding: see

Purpose: The purpose of this payload type is to distinguish FCI advertisement objects for CI/T Object List Type objects Interface: FCI Encoding: see

In the IANA was requested to create a new "CDNI CI/T Trigger Types" registry under the "Content Delivery Network Interconnection (CDNI) Parameters" registry group. Additions to the "CDNI CI/T Trigger Types" registry are made via the RFC Required policy as defined in . In this second edition of the interface, trigger types are referred to as "trigger actions". The "Trigger Types" registry is used for action definitions. Furthermore, this document, and specifically , reuses the definition of "trigger types" as defined in as trigger actions, and provide their specifications, with no modification compared to .

The IANA is requested to create a new "CDNI CI/T Trigger Specs" registry in the "Content Delivery Networks Interconnection (CDNI) Parameters" registry group. The "CDNI CI/T Trigger Specs" namespace defines the valid trigger targets' spec values in , used by the Trigger Spec object. Additions to the "CDNI CI/T Trigger Specs" registry are made via the RFC Required policy as defined in . The initial contents of the "CDNI CI/T Trigger Specs" registry comprise the names and descriptions listed in , with this document acting as the specification.

The IANA is requested to create a new "CDNI CI/T Trigger Subjects" registry in the "Content Delivery Networks Interconnection (CDNI) Parameters" registry group. The "CDNI CI/T Trigger Subjects" namespace defines the valid trigger targets' subject values in , used by the Trigger Spec object. Additions to the "CDNI CI/T Trigger Subjects" registry are made via the RFC Required policy as defined in . The initial contents of the "CDNI CI/T Trigger Subjects" registry comprise the names and descriptions listed in , with this document acting as the specification.

The IANA is requested to create a new "CDNI CI/T Object List Types" registry in the "Content Delivery Networks Interconnection (CDNI) Parameters" registry group. The "CDNI CI/T Object List Types" namespace defines the valid object list type values in , used by the Object List object. Additions to the "CDNI CI/T Object List Types" registry are made via the RFC Required policy as defined in . The initial contents of the "CDNI CI/T Object List Types" registry comprise the names and descriptions listed in , with this document acting as the specification.

The IANA is requested to create a new "CDNI CI/T Trigger Extensions" registry in the "Content Delivery Networks Interconnection (CDNI) Parameters" registry group. The "CDNI CI/T Trigger Extensions" namespace defines the valid trigger targets' extension values in , used by the Trigger Spec object. Additions to the "CDNI CI/T Trigger Extensions" registry are made via the RFC Required policy as defined in . The initial contents of the "CDNI CI/T Trigger Extensions" registry comprise the names and descriptions listed in , with this document acting as the specification.

In the IANA was requested to create a new "CDNI CI/T Error Codes" registry under the "Content Delivery Network Interconnection (CDNI) Parameters" registry group. Additions to the "CDNI CI/T Error Codes" registry are made via the Specification Required policy as defined in . The Designated Expert will verify that new Error Code registrations do not duplicate existing Error Code definitions (in name or functionality), prevent gratuitous additions to the namespace, and prevent any additions to the namespace that would impair the interoperability of CDNI implementations. In this second edition of the interface, we list and repeat the definition of the Error Codes from - acting as the entities specification with no modification compared to . Additionally, the IANA is requested to register three additional error codes, "espec", "esubject" and "eextension", with specification as defined in .

The IANA is requested to create a new "CDNI CI/T URL types" registry in the "Content Delivery Networks Interconnection (CDNI) Parameters" registry group. The "CDNI CI/T URL Types" namespace defines the valid URL type values in , used by , , and . The initial contents of the "CDNI CI/T Trigger Extensions" registry comprise the names and descriptions listed in , with this document acting as the specification.

The CI/T interface provides a mechanism to allow a uCDN to generate requests into the dCDN and to inspect its own CI/T requests and their current states. The CI/T interface does not allow access to, or modification of, the uCDN or dCDN metadata relating to content delivery or to the content itself. It can only control the presence of that metadata in the dCDN, and the processing work and network utilization involved in ensuring that presence. By examining "preposition" requests to a dCDN, and correctly interpreting content and metadata URLs, an attacker could learn the uCDN's or content owner's predictions for future content popularity. By examining "invalidate" or "purge" requests, an attacker could learn about changes in the content owner's catalog. By injecting CI/T Commands, an attacker or a misbehaving uCDN would generate work in the dCDN and uCDN as they process those requests. So would a man-in-the-middle attacker modify valid CI/T Commands generated by the uCDN. In both cases, that would decrease the dCDN's caching efficiency by causing it to unnecessarily acquire or reacquire content metadata and/or content. A dCDN implementation of CI/T MUST restrict the actions of a uCDN to the data corresponding to that uCDN. Failure to do so would allow uCDNs to detrimentally affect each other's efficiency by generating unnecessary acquisition or reacquisition load. An origin that chooses to delegate its delivery to a CDN is trusting that CDN to deliver content on its behalf; the interconnection of CDNs is an extension of that trust to dCDNs. That trust relationship is a commercial arrangement, outside the scope of the CDNI protocols. So, while a malicious CDN could deliberately generate load on a dCDN using the CI/T interface, the protocol does not otherwise attempt to address malicious behavior between interconnected CDNs.

A CI/T implementation MUST support Transport Layer Security (TLS) transport for HTTP (HTTPS) as per . TLS MUST be used by the server side (dCDN) and the client side (uCDN) of the CI/T interface, including the authentication of the remote end, unless alternate methods are used to ensure the security of the information in the CI/T 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 CI/T interface allows the dCDN and the uCDN to authenticate each other using the TLS client authentication and TLS server authentication. Once the dCDN and the uCDN have mutually authenticated each other, TLS allows: The dCDN and the uCDN to authorize each other (to ensure that they are receiving CI/T Commands from, or reporting status to, an authorized CDN). CDNI commands and responses to be transmitted with confidentiality. Protection of the integrity of CDNI commands and responses. When TLS is used, the general TLS usage guidance in MUST be followed. The mechanisms for access control are dCDN-specific and are not standardized as part of this CI/T specification. HTTP requests that attempt to access or operate on CI/T data belonging to another CDN MUST be rejected using, for example, HTTP 403 ("Forbidden") or 404 ("Not Found"). This is intended to prevent unauthorized users from generating unnecessary load in dCDNs or uCDNs due to revalidation, reacquisition, or unnecessary acquisition. When deploying a network of interconnected CDNs, the possible inefficiencies related to the diamond configuration discussed in should be considered.

This document does not define a specific mechanism to protect against Denial-of-Service (DoS) attacks on the CI/T interface. However, CI/T endpoints can be protected against DoS attacks through the use of TLS transport and/or via mechanisms outside the scope of the CI/T interface, such as firewalling or the use of Virtual Private Networks (VPNs). Depending on the implementation, triggered activity may consume significant processing and bandwidth in the dCDN. A malicious or faulty uCDN could use this to generate unnecessary load in the dCDN. The dCDN should consider mechanisms to avoid overload -- for example, by rate-limiting acceptance or processing of CI/T Commands, or by performing batch processing.

The CI/T protocol does not carry any information about individual end users of a CDN; there are no privacy concerns for end users. The CI/T protocol does carry information that could be considered commercially sensitive by CDN operators and content owners. The use of mutually authenticated TLS to establish a secure session for the transport of CI/T data, as discussed in , provides confidentiality while the CI/T data is in transit and prevents parties other than the authorized dCDN from gaining access to that data. The dCDN MUST ensure that it only exposes CI/T data related to a uCDN to clients it has authenticated as belonging to that uCDN.

&RFC1930; &RFC2119; &RFC3339; &RFC3986; &RFC8126; &RFC8259; &RFC8006; &RFC8007; &RFC8174; &RFC9110; &RFC9112; &RFC9325; &RFC6707; &RFC7336; &RFC7337; &RFC7736; &RFC7975; &RFC8216; ISO Microsoft ISO ECMA International

The authors thank Kevin Ma for his input, and Carsten Bormann for his review and formalization of the JSON data.