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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 8007

Network Working Group                                          R. Murray
Internet-Draft                                          B. Niven-Jenkins
Intended status: Standards Track                Velocix (Alcatel-Lucent)
Expires: October 10, 2013                                  April 8, 2013


                   CDNI Control Interface / Triggers
                  draft-ietf-cdni-control-triggers-00

Abstract

   This document describes the part of the CDN Interconnect 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 can use this mechanism to request that the downstream
   CDN pre-positions metadata or content, or that it re-validate or
   purge metadata or content.  The upstream CDN can monitor the status
   of activity that it has triggered in the downstream CDN.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 10, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal



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   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Model for CDNI Triggers  . . . . . . . . . . . . . . . . . . .  5
     2.1.  Timing of Triggered Activity . . . . . . . . . . . . . . .  7
     2.2.  Trigger Results  . . . . . . . . . . . . . . . . . . . . .  7
   3.  Collections of Trigger Status Resources  . . . . . . . . . . .  7
   4.  CDNI Trigger interface . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Creating Triggers  . . . . . . . . . . . . . . . . . . . . 10
     4.2.  Checking Status  . . . . . . . . . . . . . . . . . . . . . 11
       4.2.1.  Polling Trigger Status Resource collections  . . . . . 11
       4.2.2.  Polling Trigger Status Resources . . . . . . . . . . . 11
     4.3.  Deleting Triggers  . . . . . . . . . . . . . . . . . . . . 11
     4.4.  Expiry of Trigger Status Resources . . . . . . . . . . . . 12
     4.5.  Error Handling . . . . . . . . . . . . . . . . . . . . . . 12
   5.  Properties of Triggers . . . . . . . . . . . . . . . . . . . . 13
     5.1.  Properties of Trigger Requests . . . . . . . . . . . . . . 13
       5.1.1.  Content URLs . . . . . . . . . . . . . . . . . . . . . 14
     5.2.  Properties of Trigger Status Resources . . . . . . . . . . 14
     5.3.  Properties of ErrorDesc  . . . . . . . . . . . . . . . . . 15
     5.4.  Properties of Trigger Collections  . . . . . . . . . . . . 16
     5.5.  Trigger Resource Simple Data Type Descriptions . . . . . . 16
       5.5.1.  TriggerType  . . . . . . . . . . . . . . . . . . . . . 16
       5.5.2.  TriggerStatus  . . . . . . . . . . . . . . . . . . . . 16
       5.5.3.  URLs . . . . . . . . . . . . . . . . . . . . . . . . . 17
       5.5.4.  AbsoluteTime . . . . . . . . . . . . . . . . . . . . . 17
       5.5.5.  ErrorCode  . . . . . . . . . . . . . . . . . . . . . . 17
   6.  JSON Encoding of Objects . . . . . . . . . . . . . . . . . . . 17
     6.1.  JSON Encoding of Embedded Types  . . . . . . . . . . . . . 18
       6.1.1.  TriggerType  . . . . . . . . . . . . . . . . . . . . . 18
       6.1.2.  TriggerStatus  . . . . . . . . . . . . . . . . . . . . 18
       6.1.3.  PatternMatch . . . . . . . . . . . . . . . . . . . . . 19
       6.1.4.  ErrorDesc  . . . . . . . . . . . . . . . . . . . . . . 19
       6.1.5.  ErrorCode  . . . . . . . . . . . . . . . . . . . . . . 20
       6.1.6.  Relationship . . . . . . . . . . . . . . . . . . . . . 20
     6.2.  MIME Media Types . . . . . . . . . . . . . . . . . . . . . 20
   7.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 21



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     7.1.  Creating Triggers  . . . . . . . . . . . . . . . . . . . . 21
       7.1.1.  Preposition  . . . . . . . . . . . . . . . . . . . . . 21
       7.1.2.  Invalidate . . . . . . . . . . . . . . . . . . . . . . 23
     7.2.  Examining Trigger Status . . . . . . . . . . . . . . . . . 24
       7.2.1.  Collection of All Triggers . . . . . . . . . . . . . . 24
       7.2.2.  Filtered Collections of Triggers . . . . . . . . . . . 25
       7.2.3.  Trigger Status Resources . . . . . . . . . . . . . . . 27
       7.2.4.  Polling for Change . . . . . . . . . . . . . . . . . . 29
       7.2.5.  Cancelling or Removing a Trigger . . . . . . . . . . . 32
       7.2.6.  Error Reporting  . . . . . . . . . . . . . . . . . . . 34
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 35
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 35
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 35
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 35
     11.2. Informative References . . . . . . . . . . . . . . . . . . 35
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36


































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1.  Introduction

   [RFC6707] introduces the Problem scope for CDN Interconnection (CDNI)
   and lists the four categories of interfaces that may be used to
   compose a CDNI solution (Control, Metadata, Request Routing,
   Logging).

   [I-D.ietf-cdni-framework] expands on the information provided in
   [RFC6707] and describes each of the interfaces and the relationships
   between them in more detail.

   This draft concentrates on the "High" and "Medium" priority
   requirements for the CDNI Control Interface identified in section 4
   of [I-D.ietf-cdni-requirements], reproduced here for convenience:

      CNTL-1 [HIGH] The CDNI Control interface shall allow the Upstream
      CDN to request that the Downstream CDN (and, if cascaded CDNs are
      supported by the solution, that the potential cascaded Downstream
      CDNs) perform the following actions on an object or object set:

      *  Mark an object or set of objects and/or its CDNI metadata as
         "stale" and revalidate them before they are delivered again
      *  Delete an object or set of objects and/or its CDNI metadata
         from the CDN surrogates and any storage.  Only the object(s)
         and CDNI metadata that pertain to the requesting Upstream CDN
         are allowed to be purged.
      CNTL-2 [HIGH] The CDNI Control interface shall allow the
      Downstream CDN to report on the completion of these actions (by
      itself, and if cascaded CDNs are supported by the solution, by
      potential cascaded Downstream CDNs), in a manner appropriate for
      the action (e.g. synchronously or asynchronously).  The
      confirmation receipt should include a success or failure
      indication.  The failure indication is used if the Downstream CDN
      cannot delete the content in its storage.
      CNTL-3 [HIGH] The CDNI Control interface shall support initiation
      and control by the Upstream CDN of pre-positioned CDNI metadata
      acquisition by the Downstream CDN.
      CNTL-4 [MED] The CDNI Control interface should support initiation
      and control by the Upstream CDN of pre-positioned content
      acquisition by the Downstream CDN.
      CNTL-12 [MED] The CDNI Control interface should allow for multiple
      content items identified by a Content Collection ID to be purged
      using a single Content Purge action.

   This document describes the CI/T interface, Control Interface /
   Triggers.  It does not consider those parts of the control interface
   that relate to configuration, bootstrapping or authentication of CDN
   Interconnect interfaces.



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   o  Section 2 outlines the model for the Trigger Interface at a high
      level.
   o  Section 3 describes collections of Trigger Resources.
   o  Section 4 defines the RESTful web service provided by dCDN.
   o  Section 5 lists properties of Trigger Requests and Status
      Resources.
   o  Section 6 defines a JSON encoding for Trigger Requests and Status
      Resources.
   o  Section 7 contains example messages.

1.1.  Terminology

   This document reuses the terminology defined in [RFC6707].


2.  Model for CDNI Triggers

   A trigger, sent from uCDN to dCDN, is a request for dCDN to do some
   work relating to data originating from uCDN.

   The trigger may request action on either metadata or content, the
   following actions can be requested:

   o  preposition - used to instruct dCDN to fetch metadata from uCDN,
      or content from any origin including uCDN.
   o  invalidate - used to instruct dCDN to revalidate specific metadata
      or content before re-using it.
   o  purge - used to instruct dCDN to delete specific metadata or
      content.

   The CI/T interface is a RESTful web service offered by dCDN.  It
   allows creation and deletion of triggers, and tracking of the
   triggered activity.  When dCDN accepts a trigger it creates a
   resource describing status of the triggered activity, a Trigger
   Status Resource.  The uCDN may poll Trigger Status Resources to
   monitor progress.

   Requests to invalidate and purge metadata or content apply to all
   variants of that data with a given URI.

   The dCDN maintains a collection of Trigger Status Resources for each
   uCDN, each uCDN only has access to its own collection and the
   location of that collection is shared when CDN interconnection is
   established.

   To trigger activity in dCDN, uCDN will POST to the collection of
   Trigger Status Resources.  If dCDN accepts the trigger, it creates a
   new Trigger Status Resource and returns its location to uCDN.  To



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   monitor progress, uCDN may GET the Trigger Status Resource.  To
   cancel a trigger, or remove a trigger from the collection once its
   activity has been completed, uCDN may DELETE the Trigger Status
   Resource.

   In addition to the collection of all Trigger Status Resources for
   uCDN, uCDN shall have access to filtered views of that collection.
   These filtered views are defined in Section 3 and include collections
   of active and completed triggers.  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 dCDN, and for uCDN to discover the status
   of that activity.  Only successful triggering is shown.  Examples of
   the messages are given in Section 7.
      uCDN                                                   dCDN
       |    (1) POST http://dcdn.example.com/triggers/uCDN     |
      [ ] --------------------------------------------------> [ ]--+
       |                                                      [ ]  | (2)
       |    (3) HTTP 201 Response                             [ ]<-+
      [ ] <-------------------------------------------------- [ ]
       |     Loc: http://dcdn.example.com/triggers/uCDN/123    |
       |                                                       |
       .                           .                           .
       .                           .                           .
       .                           .                           .
       |                                                       |
       |   (4) GET http://dcdn.example.com/triggers/uCDN/123   |
      [ ] --------------------------------------------------> [ ]
       |                                                      [ ]
       |   (5) HTTP 200 Trigger Status Resource               [ ]
      [ ] <-------------------------------------------------- [ ]
       |                                                       |
       |                                                       |

              Figure 1: Basic CDNI Message Flow for Triggers

   The steps in Figure 1 are:

   1.  uCDN triggers action in dCDN by posting to a collection of
       Trigger Status Resources,
       "http://dcdn.example.com/triggers/uCDN".  The URL of this was
       given to uCDN when the trigger interface was established.
   2.  dCDN authenticates the request, validates the trigger and if it
       accepts the request, creates a new Trigger Status Resource.
   3.  dCDN responds to uCDN with an HTTP 201 response status, and the
       location of the Trigger Status Resource.




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   4.  uCDN may repeatedly poll the Trigger Status Resource in dCDN.
   5.  dCDN responds with the Trigger Status Resource, describing
       progress or results of the triggered activity.

   The remainder of this document describes the messages, Trigger Status
   Resources, and collections of Trigger Status Resources in more
   detail.

2.1.  Timing of Triggered Activity

   Timing of triggered activity is under dCDN control, including its
   start-time and pacing of the activity in the network.

   Invalidate and purge triggers MUST be applied to all data acquired
   before the trigger was created in dCDN.  The dCDN MAY apply the
   triggers to data acquired after trigger creation.

   If uCDN wishes to invalidate or purge content, then immediately
   preposition replacement content at the same URLs, it must ensure the
   dCDN has completed the invalidate/purge before initiating the
   prepositioning.  If it fails to do that and the requests overlap, and
   dCDN passes the triggers on to a further dCDN in a cascade, that CDN
   may preposition content that has not yet been invalidated/purged in
   its uCDN.

2.2.  Trigger Results

   Each Trigger Request may operate on multiple data items.  The trigger
   shall be reported as "complete" only if all actions can be completed
   successfully, otherwise it shall be reported as "failed".  The
   reasons for failure and URLs or Patterns affected shall be enumerated
   in the Trigger Status Resource.  For more detail, see section
   Section 4.5.

   If a dCDN is also acting as uCDN in a cascade, it MUST forward
   triggers to any downstream CDNs that may have data affected by the
   trigger.  The trigger MUST NOT be reported as complete in a CDN until
   it is complete in all of its downstream CDNs.  A trigger MAY be
   reported as failed as soon as it fails in a CDN or in any of its
   downstream CDNs.


3.  Collections of Trigger Status Resources

   As described in Section 2, Trigger Status Resources exist in dCDN to
   report the status of activity triggered by each uCDN.

   A collection of Trigger Status Resources is a resource that contains



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   a reference to each Trigger Status Resource in that collection.

   To trigger activity in dCDN, uCDN creates a new Trigger Status
   Resource by posting to dCDN's collection of uCDN's Trigger Status
   Resources.  The URL of each Trigger Status Resource is generated by
   the dCDN when it accepts the trigger, and returned to uCDN.  This
   immediately enables uCDN to check the status of that trigger.

   The dCDN must present a different set of Trigger Status Resources to
   each interconnected uCDN, only Trigger Status Resources belonging to
   a uCDN shall be visible to it.  The dCDN may, for example, achieve
   this by offering different collection URLs to uCDNs, or by filtering
   the response based on the client uCDN.

   The dCDN resource representing the collection of all uCDN's Trigger
   Status Resources is accessible to uCDN.  This collection lists all
   uCDN triggers that have been accepted by dCDN, and have not yet been
   deleted by uCDN or expired and removed by dCDN.

   In order to allow uCDN to check status of multiple jobs in a single
   request, dCDN shall also maintain collections representing filtered
   views of the collection of all Trigger Status Resources.  The
   filtered collections are:
   o  Pending - Trigger Status Resources for triggers that have been
      accepted, but not yet acted upon.
   o  Active - Trigger Status Resources for triggered activity that is
      currently being processed in dCDN.
   o  Complete - Trigger Status Resources representing activity that
      completed successfully.
   o  Failed - Trigger Status Resources representing activity that
      failed.


4.  CDNI Trigger interface

   This section describes an interface to enable an upstream CDN to
   trigger defined activities in a downstream CDN.  The interface is
   intended to be independent of the set of activities defined now, or
   that may be defined in future.

   The CI/T interface is built on the principles of RESTful web
   services.  Requests are made over HTTP, and the HTTP Method defines
   the operation the request would like to perform.  The corresponding
   HTTP Response returns the status of the operation in the HTTP Status
   Code and returns the current representation of the resource (if
   appropriate) in the Response Body.  HTTP Responses from servers
   implementing the CI/T interface that contain a response body SHOULD
   include an ETag to enable validation of cached versions of returned



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   resources.

   Servers implementing the CI/T interface MUST support the HTTP GET,
   HEAD, POST and DELETE methods.  The only representation specified in
   this document is JSON.

   Trigger Requests are POSTed to a URI in dCDN.  If the trigger is
   accepted by dCDN, it creates a Trigger Status Resource and returns
   its URI to dCDN in an HTTP 201 response.  The triggered activity can
   then be monitored by uCDN using that resource and the collections
   described in Section 3.

   The URI that Trigger Requests should be POSTed to needs to be either
   discovered by or configured in the upstream CDN.  Performing a GET on
   that URI retrieves a collection of the URIs of all Trigger Status
   Resources.  The URI of each Trigger Status Resource is also returned
   to uCDN when it is created.  This means all Trigger Status Resources
   can be discovered, so CI/T servers are free to assign whatever
   structure they desire to the URIs for CI/T resources.  CI/T clients
   MUST NOT make any assumptions regarding the structure of CI/T URIs or
   the mapping between CI/T objects and their associated URIs.
   Therefore any URIs present in the examples below are purely
   illustrative and are not intended to impose a definitive structure on
   CI/T interface implementations.

   The CI/T interface builds on top of HTTP, so CI/T servers may make
   use of any HTTP feature when implementing the CI/T interface.  For
   example, a CI/T server may make use of HTTP's caching mechanisms to
   indicate that the returned response/representation has not been
   modified since it was last returned, reducing the processing needed
   to determine whether the status of triggered activity has changed.

   This specification is neutral with regard to the transport below the
   HTTP layer.

   [Editor's note: It is anticipated that decisions on use of HTTPS for
   other CDNI interfaces will be adopted for Triggers.]

   Discovery of the CI/T Interface is outside the scope of this
   document.  It is anticipated that a common mechanism for discovery of
   all CDNI interfaces will be defined.

   The dCDN must ensure that activity triggered by uCDN only affects
   metadata or content originating from that uCDN.  Since only one CDN
   can be authoritative for a given item of metadata or content, this
   requirement means there cannot be any "loops" in trigger requests
   between CDNs.




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4.1.  Creating Triggers

   To create a new trigger, uCDN makes an HTTP POST to the unfiltered
   collection of its triggers.  The request body of that POST is a
   Trigger Request.

   dCDN validates and authenticates that request, if it is malformed or
   uCDN does not have sufficient access rights it MAY reject the request
   immediately.  In this case, it SHALL respond with an appropriate 4xx
   HTTP error code and no resource shall be created on dCDN.

   If the request is accepted, uCDN SHALL create a new Trigger Status
   Resource.  The HTTP response to dCDN SHALL have status code 201 and
   the URI of the Trigger Status Resource in the Location header field.
   The HTTP response MAY include the content of the newly created
   Trigger Status Resource, this is recommended particularly in cases
   where the trigger has completed immediately.

   Once a Trigger Status Resource has been created dCDN MUST NOT re-use
   its location, even after that resource has been removed through
   deletion or expiry.

   The "request" property of the Trigger Status Resource SHALL contain
   the information posted in the body of the Trigger Request.  Note that
   this need not be a byte-for-byte copy.  For example, in the JSON
   representation the dCDN may re-serialise the information differently.

   If the trigger is queued by dCDN for later action, the "status"
   property of the Trigger Status Resource SHALL be "pending".  Once
   trigger processing has started the "status" SHALL be "active".

   A trigger may result in no activity in dCDN if, for example, it is an
   invalidate or purge request for data the dCDN has not acquired, or a
   prepopulate request for data it has already acquired.  In this case,
   the "status" of the Trigger Status Resource shall be "complete" and
   the Trigger Status Resource shall be added to the dCDN collection of
   Complete Triggers.

   If dCDN is not able to track triggered activity, it MAY indicate that
   it has undertaken to complete the activity but will not report
   completion or any further errors.  To do this, it must set the
   trigger status to "complete", with an estimated completion time in
   the future ("etime" greater than "mtime").

   Once created, Trigger Status Resources may be deleted by uCDN but not
   modified.  The dCDN MUST reject PUT and POST requests from uCDN to
   Trigger Status Resources using HTTP status code 403.




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4.2.  Checking Status

   The uCDN has two ways to check progress of activity it has triggered
   in dCDN, described in the following sections.

   Because the triggers protocol is based on HTTP, Entity Tags may be
   used by the uCDN as cache validators, as defined in section 3.11 of
   [RFC2616], to check for change in status of a resource or collection
   of resources without re-fetching the whole resource or collection.

   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 uCDN should poll for change.

4.2.1.  Polling Trigger Status Resource collections

   uCDN can fetch the collection of its Trigger Status Resources, or
   filtered views of that collection.

   This makes it possible to poll status of all triggered activity in a
   single request.  If dCDN moves a Trigger Status Resource from the
   Active to the Completed collection, uCDN may chose to fetch the
   result of that activity.

   When polling in this way, uCDN may choose to use HTTP Entity Tags to
   monitor for change, rather than repeatedly fetching the whole
   collection.

4.2.2.  Polling Trigger Status Resources

   uCDN has a reference (URI provided by the dCDN) for each Trigger
   Status Resource it has created, it may fetch that resource at any
   time.

   This may be used to retrieve progress information, and to fetch the
   result of triggered activity.

4.3.  Deleting Triggers

   The uCDN MAY delete Trigger Status Resources at any time, using the
   HTTP DELETE method.

   Once deleted, the references to a Trigger Status Resource MUST be
   removed from all Trigger Status Resource collections.  Subsequent
   requests for the resource shall be handled as required by HTTP, and
   so will receive responses with status 404 or 410.

   If a "pending" Trigger Status Resource is deleted, dCDN SHOULD NOT



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   start processing of that activity.  Deleting a "pending" trigger does
   not however guarantee that it is not started because, once it has
   triggered activity, uCDN cannot control the timing of that activity.
   Processing may, for example, start after the DELETE is sent by uCDN
   and before the DELETE is processed by dCDN.

   If an "active" Trigger Status Resource is deleted, dCDN MAY stop
   processing the triggered activity.  However, as with deletion of a
   "pending" trigger, dCDN does not guarantee this.

   Deletion of a "complete" or "failed" Trigger Status Resource requires
   no processing in dCDN other than deletion of the resource.

4.4.  Expiry of Trigger Status Resources

   The dCDN MAY choose to automatically delete Trigger Status Resources
   some time after they become completed or failed.  In this case, dCDN
   will remove the resource and respond to subsequent requests for it
   with HTTP status 404 or 410.

   If dCDN performs this housekeeping, it MUST have reported the length
   of time after which completed Trigger Status Resources become stale
   via a property of the collection of all Trigger Status Resources.  It
   is recommended that Trigger Status Resources are automatically
   deleted 24 hours after they become completed or failed.

   To ensure it has access to the status of its completed and failed
   triggers, it is recommended that uCDN's polling interval is half the
   time after which records for completed activity will be considered
   stale.

4.5.  Error Handling

   A CI/T server may reject a trigger request using HTTP status codes,
   for example 400 if the request is malformed or 401 if the client does
   not have permission to create triggers or it is trying to act on
   another CDN's data.

   If any part of the trigger request fails the trigger shall 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 may be present while the trigger is still
   "pending" or "active" if the trigger is still running for some URLs
   or Patterns in the trigger request.

   Once a request has been accepted, processing errors are reported in
   the Trigger Status Resource using a list of "ErrorDesc".  Each



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   ErrorDesc is used to report errors against one or more of the URLs or
   Patterns in the trigger request.

   If a surrogate affected by a trigger is offline in dCDN, or dCDN is
   unable to pass a trigger request on to any of its affected dCDNs;
   dCDN should report an error if the request is abandoned, otherwise it
   must keep the trigger in state "pending" or "active" until it's acted
   upon or uCDN chooses to cancel it.  Or, if the request is queued and
   dCDN will not report further status, dCDN may report the trigger as
   "complete" with an "etime" in the future.

   Note that an "invalidate" trigger may be reported as "complete" when
   surrogates that may have the data are offline, if those surrogates
   will not use the affected data without first revalidating it when
   they are back online.  This does not apply to "preposition" or
   "purge" triggers.


5.  Properties of Triggers

5.1.  Properties of Trigger Requests

   Properties of Trigger Requests are defined in the following
   subsections.

      Property: type
         Description: This property defines the type of the trigger:
         Type: TriggerType
         Mandatory: Yes

      Property: metadata.urls
         Description: The uCDN URL for the metadata the trigger applies
         to.
         Type: URLs
         Mandatory: No, but at least one of 'metadata.*' or 'content.*'
         MUST be present and non-empty.
      Property: content.urls
         Description: URLs of content data the trigger applies to, see
         Section 5.1.1.
         Type: URLs
         Mandatory: No, but at least one of 'metadata.*' or 'content.*'
         MUST be present and non-empty.
      Property: content.ccid
         Description: The Content Collection IDentifier of data the
         trigger applies to.
         Type: List of strings





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         Mandatory: No, but at least one of 'metadata.*' or 'content.*'
         MUST be present and non-empty.
      Property: metadata.patterns
         Description: The metadata the trigger applies to.
         Type: List of PatternMatch
         Mandatory: No, but at least one of 'metadata.*' or 'content.*'
         MUST be present and non-empty, and metadata.patterns MUST NOT
         be present if the TriggerType is Preposition.
      Property: content.patterns
         Description: The content data the trigger applies to.
         Type: List of PatternMatch
         Mandatory: No, but at least one of 'metadata.*' or 'content.*'
         MUST be present and non-empty, and content.patterns MUST NOT be
         present if the TriggerType is Preposition.

5.1.1.  Content URLs

   To refer to content in dCDN, uCDN must present URLs in the same form
   clients will use to access content in that dCDN, after transformation
   to remove any surrogate-specific parts of a 302-redirect URL form.
   By definition, it is always possible to locate content based on URLs
   in this form.

   If content URLs are transformed by an intermediate CDN in a cascade,
   that intermediate CDN must transform URLs in trigger requests it
   passes to its dCDN.

   [Editor's note: Design for CDNI Metadata transformation, including
   discussion of URL transformation, is being undertaken as part of the
   work on the metadata interface.  The intention is to align with that
   document or make reference to it when it's complete.]

   When processing trigger requests, CDNs may ignore the URL scheme
   (http or https) in comparing URLs.  For example, for an invalidate or
   purge trigger, content may invalidated or purged regardless of the
   protocol clients use to request it.

5.2.  Properties of Trigger Status Resources

      Property: trigger
         Description: The properties of trigger request that created
         this record.
         Type: TriggerRequest
         Mandatory: Yes

      Property: ctime





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         Description: Time at which the request was received by dCDN.
         Time is local to dCDN, there is no requirement to synchronise
         clocks between interconnected CDNs.
         Type: AbsoluteTime
         Mandatory: Yes

      Property: mtime
         Description: Time at which the resource was last modified.
         Time is local to dCDN, there is no requirement to synchronise
         clocks between interconnected CDNs.
         Type: AbsoluteTime
         Mandatory: Yes
      Property: etime
         Description: Estimate of the time at which dCDN expects to
         complete the activity.  Time is local to dCDN, there is no
         requirement to synchronise clocks between interconnected CDNs.
         Type: AbsoluteTime
         Mandatory: No

      Property: status
         Description: Current status of the triggered activity.
         Type: TriggerStatus
         Mandatory: Yes

      Property: errors
         Description: List of ErrorDesc.
         Mandatory: No.

5.3.  Properties of ErrorDesc

   An ErrorDesc object is used to report failure for URLs and patterns
   in a trigger request.
      Property: error
         Type: ErrorCode.
         Mandatory: Yes.
      Description: List of metadata.urls, content.urls,
      metadata.patterns, content.patterns

         Description: Metadata and content references copied from the
         trigger request.  Only those URLs and patterns to which the
         error applies shall be included in each property, but those
         URLs and patterns shall be exactly as they appear in the
         request, dCDN must not generalise the URLs.  (For example, if
         uCDN requests prepositioning of URLs
         "http://ucdn.example.com/a" and "http://ucdn.example.com/b",
         dCDN may not generalise its error report to Pattern
         "http://ucdn.example.com/*").




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         Mandatory: At least one of these properties is mandatory in
         each ErrorDesc.
      Property: description
         Description: A String containing a human-readable description
         of the error.
         Mandatory: No.

5.4.  Properties of Trigger Collections

      Property: links
         Description: References to Trigger Status Resources in the
         collection.
         Type: List of Relationships.
         Mandatory: Yes
      Property: staleresourcetime
         Description: The length of time for which dCDN guarantees to
         keep a completed Trigger Status Resource.  After this time,
         dCDN MAY delete the resource and all references to it from
         collections.
         Type: Integer, time in seconds.
         Mandatory: Yes, in the collection of all Trigger Status
         Resources if 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.

5.5.  Trigger Resource Simple Data Type Descriptions

   This section describes the simpler data types that are used for
   properties of Trigger Status resources.

5.5.1.  TriggerType

   This type defines the type of action being triggered, permitted
   actions are:
   o  Preposition - a request for dCDN to acquire metadata or content.
   o  Invalidate - a request for dCDN to invalidate metadata or content.
      After servicing this request the dCDN will not use the specified
      data without first re-validating it using, for example, an "If-
      None-Match" HTTP request.  The dCDN need not erase the associated
      data.
   o  Purge - a request for dCDN to erase metadata or content.  After
      servicing the request, the specified data must not be held on
      dCDN.

5.5.2.  TriggerStatus

   This type describes the current status of a Trigger, possible values
   are:



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   o  Pending - the trigger has not yet been acted upon.
   o  Active - the trigger is currently being acted upon.
   o  Complete - the triggered activity completed successfully, or the
      trigger has been accepted and no further status update will be
      made.
   o  Failed - the triggered activity could not be completed.

5.5.3.  URLs

   This type describes a set of references to metadata or content, it is
   simply a list of absolute URLs.

5.5.4.  AbsoluteTime

   Times are expressed in seconds since the UNIX epoch.

5.5.5.  ErrorCode

   This type is used by dCDN to report failures in trigger processing.

   o  EMETA - dCDN was unable to acquire metadata required to fulfil the
      request.
   o  ECONTENT - dCDN was unable to acquire content (preposition
      triggers only).
   o  EPERM - uCDN does not have permission to trigger the requested
      activity (for example, the data is owned by another CDN).
   o  EREJECT - dCDN is not willing to fulfil the request (for example,
      a preposition request for content at a time when dCDN would not
      accept Request Routing requests from uCDN).
   o  ECDN - An internal error in dCDN or one of its downstream CDNs.


6.  JSON Encoding of Objects

   This encoding is based on that described in [I-D.ietf-cdni-metadata],
   but has been reproduced here while metadata work is in progress.
   Once that work is complete, the authors would look to align with the
   structure of the metadata draft and make reference to common
   definitions as appropriate.

   The encoding for a CI/T object is a JSON object containing a
   dictionary of (key,value) pairs where the keys are the property
   names, and the values are the associated property values.

   The keys of the dictionary are the names of the properties associated
   with the object and are therefore dependent on the specific object
   being encoded (i.e. dependent on the MIME Media Type of the returned
   resource).  Likewise, the values associated with each key are



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   dependent on the specific object being encoded (i.e. dependent on the
   MIME Media Type of the returned resource).

   The "trigger" property of the top level JSON object lists the
   requested action.

      Key: trigger
         Description: An object specifying the trigger type and a set of
         data to act upon.
         Type: A JSON object.
         Mandatory: Yes.

   Object keys in JSON are case sensitive and therefore any dictionary
   key defined by this document (for example the names of CI/T object
   properties) MUST always be represented in lowercase.

   In addition to the properties of an object, the following additional
   keys may be present.

      Key: base
         Description: Provides a prefix for any relative URLs in the
         object.  This is similar to the XML base tag [XML-BASE].  If
         absent, all URLs in the remainder of the document must be
         absolute URLs.
         Type: URI
         Mandatory: No

      Key: links
         Description: The relationships of this object to other
         addressable objects.
         Type: Array of Relationships.
         Mandatory: Yes

6.1.  JSON Encoding of Embedded Types

6.1.1.  TriggerType

      Key: type
         Description: One of "preposition", "invalidate" or "purge".
         Type: string

6.1.2.  TriggerStatus

      Key: status
         Description: One of "pending", "active", "failed", "complete"
         Type: string





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6.1.3.  PatternMatch

   A PatternMatch is encoded as a JSON Object containing a string to
   match and flags describing the type of match.

      Key: pattern
         Description: A pattern for string matching.  The pattern may
         contain the wildcards * and ?, where * matches any sequence of
         characters (including the empty string) and ? matches exactly
         one character.  The three literals \ , * and ? should be
         escaped as \\, \* and \?
         Type: String
         Mandatory: Yes
      Key: case-sensitive
         Description: Flag indicating whether or not case-sensitive
         matching should be used.
         Type: Boolean
         Mandatory: No, default is case-insensitive match.
      Key: match-query-string
         Description: Flag indicating whether or not the query string
         should be included in the pattern match.
         Type: Boolean
         Mandatory: No, default is not to include query.
   Example of case-sensitive prefix match against
   "http://www.example.com/trailers/":
   {
       "pattern": "http://www.example.com/trailers/*",
       "case-sensitive": true
   }

6.1.4.  ErrorDesc

   ErrorDesc shall be encoded as a JSON object with the following keys:

      Key: error
         Type: ErrorCode
         Mandatory: Yes
      Keys: metadata.urls, content.urls
         Type: Array of strings
         Mandatory: At least one of metadata.* or content.* must be
         present.
      Keys: metadata.patterns, content.patterns
         Type: Array of PatternMatch
         Mandatory: At least one of metadata.* or content.* must be
         present.
      Key: description





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         Type: String
         Mandatory: No.

6.1.5.  ErrorCode

   One of the strings "EMETA", "ECONTENT", "EPERM", "EREJECT" or "ECDN".

6.1.6.  Relationship

   JSON: A dictionary with the following keys:

   o  href - The URI of the of the addressable object being referenced.
   o  rel - The Relationship between the referring object and the object
      it is referencing.
   o  type - The MIME Media Type of the referenced object.  See
      Section 6.2 for the MIME Media Types of objects specified in this
      document.
   o  title - An optional title for the Relationship/link.

   Note: The above structure follows the pattern of atom:link in
   [RFC4287].

   Example Relationship to a CI/T Resource within a CI/T Collection:
   {
     "href": "http://triggers.cdni.example.com/trigger/12345",
     "rel": "Trigger",
     "type": "application/vnd.cdni.control.trigger.status+json"
   }

   The format of relationship values is expected to align with other
   CDNI interfaces.  For example, rather than use simple names (like
   "Trigger" in this case), there may be a namespace that allows well-
   known and proprietary values to co-exist.

6.2.  MIME Media Types

   Table 1 lists the MIME Media Type for each trigger object (resource)
   that is retrievable through the CI/T interface.

   Note: A prefix of "vnd.cdni" is used, however it is expected that a
   more appropriate prefix will be used if the CDNI WG accepts this
   document.









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   +-------------------+-----------------------------------------------+
   | Data Object       | MIME Media Type                               |
   +-------------------+-----------------------------------------------+
   | TriggerStatus     | application/                                  |
   |                   | vnd.cdni.control.trigger.status+json          |
   | TriggerCollection | application/                                  |
   |                   | vnd.cdni.control.trigger.collection+json      |
   +-------------------+-----------------------------------------------+

           Table 1: MIME Media Types for CDNI Trigger resources


7.  Examples

   The following sections provide examples of different CI/T objects
   encoded as JSON.

   No authentication is shown in the following illustrative examples, it
   is anticipated that authentication mechanisms will be aligned with
   other CDNI Interfaces as and when those mechanisms are defined.

   Discovery of the triggers interface is out of scope of this document.
   In an implementation, all URLs are under control of dCDN and the uCDN
   must not attempt to ascribe any meaning to individual elements of the
   path.  In examples in this section, the following URLs are used as
   the location of the collections of triggers:

   o  Collection of all Triggers belonging to one uCDN:
         http://dcdn.example.com/triggers
   o  Filtered collections:
         Pending: http://dcdn.example.com/triggers/pending
         Active: http://dcdn.example.com/triggers/active
         Complete: http://dcdn.example.com/triggers/complete
         Failed: http://dcdn.example.com/triggers/failed

7.1.  Creating Triggers

   Examples of uCDN triggering activity in dCDN:

7.1.1.  Preposition

   An example of a preposition request, a POST to the "AllTriggers"
   collection.

   Note that "metadata.patterns" and "content.patterns" are not allowed
   in a preposition trigger request.
   REQUEST:




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     POST /triggers HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*
     Content-Type: application/vnd.cdni.control.trigger.request+json
     Content-Length: 315

     {
       "trigger" : {
         "type": "preposition",

         "metadata.urls" : [ "http://metadata.example.com/a/b/c" ],
         "content.urls" : [
             "http://www.example.com/a/b/c/1",
             "http://www.example.com/a/b/c/2",
             "http://www.example.com/a/b/c/3",
             "http://www.example.com/a/b/c/4"
           ]
       }
     }

   RESPONSE:

     HTTP/1.1 201 Created
     Date: Sat, 23 Feb 2013 14:20:06 GMT
     Content-Length: 472
     Content-Type: application/vnd.cdni.control.trigger.status+json
     Location: http://dcdn.example.com/triggers/0
     Server: example-server/0.1

     {
         "ctime": 1361629206,
         "etime": 1361629214,
         "mtime": 1361629206,
         "status": "pending",
         "trigger": {
             "content.urls": [
                 "http://www.example.com/a/b/c/1",
                 "http://www.example.com/a/b/c/2",
                 "http://www.example.com/a/b/c/3",
                 "http://www.example.com/a/b/c/4"
             ],
             "metadata.urls": [
                 "http://metadata.example.com/a/b/c"
             ],
             "type": "preposition"
         }
     }



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7.1.2.  Invalidate

   An example of an invalidate request, another POST to the
   "AllTriggers" collection.  This instructs dCDN to re-validate the
   content at "http://www.example.com/a/index.html", as well as any
   metadata and content whose URLs are prefixed by
   "http://metadata.example.com/a/b/" and "http://www.example.com/a/b/"
   respectively, using case-insensitive matching.
   REQUEST:

     POST /triggers HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*
     Content-Type: application/vnd.cdni.control.trigger.request+json
     Content-Length: 352

     {
       "trigger" : {
         "type": "invalidate",

         "metadata.patterns" : [
             { "pattern" : "http://metadata.example.com/a/b/*" }
           ],

         "content.urls" : [ "http://www.example.com/a/index.html" ],
         "content.patterns" : [
             { "pattern" : "http://www.example.com/a/b/*",
               "case-sensitive" : true
             }
           ]
       }
     }

   RESPONSE:

     HTTP/1.1 201 Created
     Date: Sat, 23 Feb 2013 14:20:08 GMT
     Content-Length: 551
     Content-Type: application/vnd.cdni.control.trigger.status+json
     Location: http://dcdn.example.com/triggers/1
     Server: example-server/0.1

     {
         "ctime": 1361629208,
         "etime": 1361629216,
         "mtime": 1361629208,
         "status": "pending",



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         "trigger": {
             "content.patterns": [
                 {
                     "case-sensitive": true,
                     "pattern": "http://www.example.com/a/b/*"
                 }
             ],
             "content.urls": [
                 "http://www.example.com/a/index.html"
             ],
             "metadata.patterns": [
                 {
                     "pattern": "http://metadata.example.com/a/b/*"
                 }
             ],
             "type": "invalidate"
         }
     }

7.2.  Examining Trigger Status

   Once triggers have been created, uCDN can check their status as shown
   in these examples.

7.2.1.  Collection of All Triggers

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





















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REQUEST:

  GET /triggers HTTP/1.1
  User-Agent: example-user-agent/0.1
  Host: dcdn.example.com
  Accept: */*


RESPONSE:

  HTTP/1.1 200 OK
  Content-Length: 422
  Expires: Sat, 23 Feb 2013 14:21:08 GMT
  Server: example-server/0.1
  ETag: "1484827667515030767"
  Cache-Control: max-age=60
  Date: Sat, 23 Feb 2013 14:20:08 GMT
  Content-Type: application/vnd.cdni.control.trigger.collection+json

  {
      "links": [
          {
              "href": "http://dcdn.example.com/triggers/0",
              "rel": "Trigger",
              "type": "application/vnd.cdni.control.trigger.status+json"
          },
          {
              "href": "http://dcdn.example.com/triggers/1",
              "rel": "Trigger",
              "type": "application/vnd.cdni.control.trigger.status+json"
          }
      ],
      "staleresourcetime": 86400
  }

7.2.2.  Filtered Collections of Triggers

   The filtered collections are also available to uCDN.  Before dCDN
   starts processing the two triggers shown above, both will appear in
   the collection of Pending Triggers, for example:











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REQUEST:

  GET /triggers/pending HTTP/1.1
  User-Agent: example-user-agent/0.1
  Host: dcdn.example.com
  Accept: */*


RESPONSE:

  HTTP/1.1 200 OK
  Content-Length: 422
  Expires: Sat, 23 Feb 2013 14:21:09 GMT
  Server: example-server/0.1
  ETag: "-970375801048973013"
  Cache-Control: max-age=60
  Date: Sat, 23 Feb 2013 14:20:09 GMT
  Content-Type: application/vnd.cdni.control.trigger.collection+json

  {
      "links": [
          {
              "href": "http://dcdn.example.com/triggers/0",
              "rel": "Trigger",
              "type": "application/vnd.cdni.control.trigger.status+json"
          },
          {
              "href": "http://dcdn.example.com/triggers/1",
              "rel": "Trigger",
              "type": "application/vnd.cdni.control.trigger.status+json"
          }
      ],
      "staleresourcetime": 86400
  }

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














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   REQUEST:

     GET /triggers/complete HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*


   RESPONSE:

     HTTP/1.1 200 OK
     Content-Length: 53
     Expires: Sat, 23 Feb 2013 14:21:09 GMT
     Server: example-server/0.1
     ETag: "-654105208640281650"
     Cache-Control: max-age=60
     Date: Sat, 23 Feb 2013 14:20:09 GMT
     Content-Type: application/vnd.cdni.control.trigger.collection+json

     {
         "links": [],
         "staleresourcetime": 86400
     }

7.2.3.  Trigger Status Resources

   The Trigger Status Resources can also be examined for detail about
   individual triggers.  For example, for the "preposition" and
   "invalidate" triggers from previous examples:






















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   REQUEST:

     GET /triggers/0 HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*


   RESPONSE:

     HTTP/1.1 200 OK
     Content-Length: 472
     Expires: Sat, 23 Feb 2013 14:21:08 GMT
     Server: example-server/0.1
     ETag: "-7651038857765989381"
     Cache-Control: max-age=60
     Date: Sat, 23 Feb 2013 14:20:08 GMT
     Content-Type: application/vnd.cdni.control.trigger.status+json

     {
         "ctime": 1361629206,
         "etime": 1361629214,
         "mtime": 1361629206,
         "status": "pending",
         "trigger": {
             "content.urls": [
                 "http://www.example.com/a/b/c/1",
                 "http://www.example.com/a/b/c/2",
                 "http://www.example.com/a/b/c/3",
                 "http://www.example.com/a/b/c/4"
             ],
             "metadata.urls": [
                 "http://metadata.example.com/a/b/c"
             ],
             "type": "preposition"
         }
     }














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   REQUEST:

     GET /triggers/1 HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*


   RESPONSE:

     HTTP/1.1 200 OK
     Content-Length: 551
     Expires: Sat, 23 Feb 2013 14:21:09 GMT
     Server: example-server/0.1
     ETag: "-1103964172288811711"
     Cache-Control: max-age=60
     Date: Sat, 23 Feb 2013 14:20:09 GMT
     Content-Type: application/vnd.cdni.control.trigger.status+json

     {
         "ctime": 1361629208,
         "etime": 1361629216,
         "mtime": 1361629208,
         "status": "pending",
         "trigger": {
             "content.patterns": [
                 {
                     "case-sensitive": true,
                     "pattern": "http://www.example.com/a/b/*"
                 }
             ],
             "content.urls": [
                 "http://www.example.com/a/index.html"
             ],
             "metadata.patterns": [
                 {
                     "pattern": "http://metadata.example.com/a/b/*"
                 }
             ],
             "type": "invalidate"
         }
     }

7.2.4.  Polling for Change

   The uCDN may use the Entity Tags of collections or resources when
   polling for change in status, as shown in the following examples:




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   REQUEST:

     GET /triggers/pending HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*
     If-None-Match: "-970375801048973013"


   RESPONSE:

     HTTP/1.1 304 Not Modified
     Content-Length: 0
     Expires: Sat, 23 Feb 2013 14:21:09 GMT
     Server: example-server/0.1
     ETag: "-970375801048973013"
     Cache-Control: max-age=60
     Date: Sat, 23 Feb 2013 14:20:09 GMT
     Content-Type: application/vnd.cdni.control.trigger.collection+json
   REQUEST:

     GET /triggers/0 HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*
     If-None-Match: "-7651038857765989381"


   RESPONSE:

     HTTP/1.1 304 Not Modified
     Content-Length: 0
     Expires: Sat, 23 Feb 2013 14:21:08 GMT
     Server: example-server/0.1
     ETag: "-7651038857765989381"
     Cache-Control: max-age=60
     Date: Sat, 23 Feb 2013 14:20:08 GMT
     Content-Type: application/vnd.cdni.control.trigger.status+json

   When the triggered activity is complete, the contents of the filtered
   collections will be updated, along with their Entity Tags.  For
   example, when the two example triggers are complete, the collections
   of pending and complete triggers may look like:








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   REQUEST:

     GET /triggers/pending HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*
     If-None-Match: "-970375801048973013"


   RESPONSE:

     HTTP/1.1 200 OK
     Content-Length: 53
     Expires: Sat, 23 Feb 2013 14:21:13 GMT
     Server: example-server/0.1
     ETag: "-7056231826368088123"
     Cache-Control: max-age=60
     Date: Sat, 23 Feb 2013 14:20:13 GMT
     Content-Type: application/vnd.cdni.control.trigger.collection+json

     {
         "links": [],
         "staleresourcetime": 86400
     }



























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REQUEST:

  GET /triggers/complete HTTP/1.1
  User-Agent: example-user-agent/0.1
  Host: dcdn.example.com
  Accept: */*


RESPONSE:

  HTTP/1.1 200 OK
  Content-Length: 422
  Expires: Sat, 23 Feb 2013 14:21:20 GMT
  Server: example-server/0.1
  ETag: "2013095476705515794"
  Cache-Control: max-age=60
  Date: Sat, 23 Feb 2013 14:20:20 GMT
  Content-Type: application/vnd.cdni.control.trigger.collection+json

  {
      "links": [
          {
              "href": "http://dcdn.example.com/triggers/0",
              "rel": "Trigger",
              "type": "application/vnd.cdni.control.trigger.status+json"
          },
          {
              "href": "http://dcdn.example.com/triggers/1",
              "rel": "Trigger",
              "type": "application/vnd.cdni.control.trigger.status+json"
          }
      ],
      "staleresourcetime": 86400
  }

7.2.5.  Cancelling or Removing a Trigger

   To request dCDN to cancel a Trigger, uCDN may delete the Trigger
   Resource.  It may also delete completed and failed triggers to reduce
   the size of the collections.  For example, to remove the
   "preposition" request from earlier examples:










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   REQUEST:

     DELETE /triggers/0 HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*


   RESPONSE:

     HTTP/1.1 204 No Content
     Date: Sat, 23 Feb 2013 14:20:20 GMT
     Content-Length: 0
     Content-Type: text/html; charset=UTF-8
     Server: example-server/0.1

   This would, for example, cause the collection of completed triggers
   shown in the example above to be updated to:
REQUEST:

  GET /triggers/complete HTTP/1.1
  User-Agent: example-user-agent/0.1
  Host: dcdn.example.com
  Accept: */*


RESPONSE:

  HTTP/1.1 200 OK
  Content-Length: 239
  Expires: Sat, 23 Feb 2013 14:21:20 GMT
  Server: example-server/0.1
  ETag: "4257416552489354137"
  Cache-Control: max-age=60
  Date: Sat, 23 Feb 2013 14:20:20 GMT
  Content-Type: application/vnd.cdni.control.trigger.collection+json

  {
      "links": [
          {
              "href": "http://dcdn.example.com/triggers/1",
              "rel": "Trigger",
              "type": "application/vnd.cdni.control.trigger.status+json"
          }
      ],
      "staleresourcetime": 86400
  }




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7.2.6.  Error Reporting

   In this example uCDN has requested prepositioning of
   "http://newsite.example.com/index.html", but dCDN was unable to
   locate metadata for that site:
   REQUEST:

     GET /triggers/2 HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*


   RESPONSE:

     HTTP/1.1 200 OK
     Content-Length: 505
     Expires: Sat, 23 Feb 2013 14:21:28 GMT
     Server: example-server/0.1
     ETag: "2621489144226897896"
     Cache-Control: max-age=60
     Date: Sat, 23 Feb 2013 14:20:28 GMT
     Content-Type: application/vnd.cdni.control.trigger.status+json

     {
         "ctime": 1361629220,
         "errors": [
             {
                 "content.urls": [
                     "http://newsite.example.com/index.html"
                 ],
                 "description":
                   "No HostIndex entry found for newsite.example.com",
                 "error": "EMETA"
             }
         ],
         "etime": 1361629228,
         "mtime": 1361629224,
         "status": "active",
         "trigger": {
             "content.urls": [
                 "http://newsite.example.com/index.html"
             ],
             "type": "preposition"
         }
     }





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8.  IANA Considerations

   TBD.


9.  Security Considerations

   The dCDN must ensure that each uCDN only has access to its own
   Trigger Status Resources.

   It is anticipated that a common authentication mechanism will be used
   by this and other CDNI Interconnect interfaces, the mechanism must
   exist but is not identified in this document.

   The dCDN must ensure that activity triggered by uCDN only affects
   metadata or content originating from that uCDN.


10.  Acknowledgements

   TBD.


11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

11.2.  Informative References

   [I-D.ietf-cdni-framework]
              Peterson, L. and B. Davie, "Framework for CDN
              Interconnection", draft-ietf-cdni-framework-03 (work in
              progress), February 2013.

   [I-D.ietf-cdni-metadata]
              Niven-Jenkins, B., Murray, R., Watson, G., Caulfield, M.,
              Leung, K., and K. Ma, "CDN Interconnect Metadata",



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              draft-ietf-cdni-metadata-01 (work in progress),
              February 2013.

   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements",
              draft-ietf-cdni-requirements-05 (work in progress),
              February 2013.

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, December 2005.

   [RFC6707]  Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", RFC 6707, September 2012.

   [XML-BASE]
              Marsh, J., Ed. and R. Tobin, Ed., "XML Base (Second
              Edition) - http://www.w3.org/TR/xmlbase/", January 2009.


Authors' Addresses

   Rob Murray
   Velocix (Alcatel-Lucent)
   3 Ely Road
   Milton, Cambridge  CB24 6DD
   UK

   Email: rmurray@velocix.com


   Ben Niven-Jenkins
   Velocix (Alcatel-Lucent)
   3 Ely Road
   Milton, Cambridge  CB24 6DD
   UK

   Email: ben@velocix.com












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