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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: January 3, 2015                                    July 2, 2014


                   CDNI Control Interface / Triggers
                  draft-ietf-cdni-control-triggers-03

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 January 3, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   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 . . . . . . . . . . . . . . . . . . . .   9
     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  . . . . . . . . .  15
     5.3.  Properties of ErrorDesc . . . . . . . . . . . . . . . . .  16
     5.4.  Properties of Trigger Collections . . . . . . . . . . . .  17
     5.5.  Trigger Resource Simple Data Type Descriptions  . . . . .  17
       5.5.1.  TriggerType . . . . . . . . . . . . . . . . . . . . .  17
       5.5.2.  TriggerStatus . . . . . . . . . . . . . . . . . . . .  18
       5.5.3.  URLs  . . . . . . . . . . . . . . . . . . . . . . . .  18
       5.5.4.  AbsoluteTime  . . . . . . . . . . . . . . . . . . . .  18
       5.5.5.  ErrorCode . . . . . . . . . . . . . . . . . . . . . .  18
   6.  JSON Encoding of Objects  . . . . . . . . . . . . . . . . . .  19
     6.1.  JSON Encoding of Embedded Types . . . . . . . . . . . . .  20
       6.1.1.  TriggerType . . . . . . . . . . . . . . . . . . . . .  20
       6.1.2.  TriggerStatus . . . . . . . . . . . . . . . . . . . .  20
       6.1.3.  PatternMatch  . . . . . . . . . . . . . . . . . . . .  20
       6.1.4.  ErrorDesc . . . . . . . . . . . . . . . . . . . . . .  21
       6.1.5.  ErrorCode . . . . . . . . . . . . . . . . . . . . . .  22
     6.2.  MIME Media Types  . . . . . . . . . . . . . . . . . . . .  22
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  22
     7.1.  Creating Triggers . . . . . . . . . . . . . . . . . . . .  23



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       7.1.1.  Preposition . . . . . . . . . . . . . . . . . . . . .  23
       7.1.2.  Invalidate  . . . . . . . . . . . . . . . . . . . . .  24
     7.2.  Examining Trigger Status  . . . . . . . . . . . . . . . .  25
       7.2.1.  Collection of All Triggers  . . . . . . . . . . . . .  25
       7.2.2.  Filtered Collections of Triggers  . . . . . . . . . .  26
       7.2.3.  Trigger Status Resources  . . . . . . . . . . . . . .  28
       7.2.4.  Polling for Change  . . . . . . . . . . . . . . . . .  30
       7.2.5.  Cancelling or Removing a Trigger  . . . . . . . . . .  33
       7.2.6.  Error Reporting . . . . . . . . . . . . . . . . . . .  35
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  36
     8.1.  CI/T MIME Media Types . . . . . . . . . . . . . . . . . .  36
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  36
     9.1.  Authentication, Confidentiality, Integrity Protection . .  36
     9.2.  Denial of Service . . . . . . . . . . . . . . . . . . . .  37
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  37
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  37
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  37
     11.2.  Informative References . . . . . . . . . . . . . . . . .  37
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  38

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 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.  Requirements for CI/T
   are the "High" and "Medium" priority requirements for the CI
   identified in section 4 of [I-D.ietf-cdni-requirements], reproduced
   here for convenience:

      CI-1 [HIGH] The CDNI Control interface shall allow the Upstream
      CDN to request that the Downstream CDN, including downstream
      cascaded CDNs, 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.






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      CI-2 [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.

      CI-3 [MED] The CDNI Control interface should allow the Upstream
      CDN to request that the Downstream CDN, including downstream
      cascaded CDNs, mark an object or set of objects and/or its CDNI
      metadata as "stale" and revalidate them before they are delivered
      again.

      CI-4 [HIGH] The CDNI Control interface shall allow the Downstream
      CDN to report on the completion of these actions (by itself, and
      including downstream cascaded 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 along with the reason are used
      if the Downstream CDN cannot delete the content in its storage.

      CI-5 [MED] The CDNI Control interface should support initiation
      and control by the Upstream CDN of pre-positioned CDNI metadata
      acquisition by the Downstream CDN.

      CI-6 [MED] The CDNI Control interface should support initiation
      and control by the Upstream CDN of pre-positioned content
      acquisition by the Downstream CDN.

   o  Section 2 outlines the model for the CI/T Interface at a high
      level.

   o  Section 3 describes collections of Trigger Resources.

   o  Section 4 defines the web service provided by the 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].







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2.  Model for CDNI Triggers

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

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

   o  preposition - used to instruct the dCDN to fetch metadata from the
      uCDN, or content from any origin including the uCDN.

   o  invalidate - used to instruct the dCDN to revalidate specific
      metadata or content before re-using it.

   o  purge - used to instruct the dCDN to delete specific metadata or
      content.

   The CI/T interface is a web service offered by the dCDN.  It allows
   creation and deletion of triggers, and tracking of the triggered
   activity.  When the 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 the dCDN, the uCDN will POST to the collection
   of Trigger Status Resources.  If the dCDN accepts the trigger, it
   creates a new Trigger Status Resource and returns its location to the
   uCDN.  To monitor progress, the uCDN MAY GET the Trigger Status
   Resource.  To cancel a trigger, or remove a trigger from the
   collection once its activity has been completed, the uCDN MAY DELETE
   the Trigger Status Resource.

   In addition to the collection of all Trigger Status Resources for
   uCDN, uCDN has 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



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   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 the dCDN by posting to a collection of
       Trigger Status Resources, "http://dcdn.example.com/triggers/
       uCDN".  The URL of this was given to the 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 the uCDN with an HTTP 201 response status, and
       the location of the Trigger Status Resource.

   4.  uCDN may repeatedly poll the Trigger Status Resource in the 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.





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2.1.  Timing of Triggered Activity

   Timing of triggered activity is under the dCDN's 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 the dCDN.  The dCDN may apply the
   triggers to data acquired after trigger creation.

   If the uCDN wishes to invalidate or purge content, then immediately
   pre-position replacement content at the same URLs, it SHOULD ensure
   the dCDN has completed the invalidate/purge before initiating the
   prepositioning.  Otherwise, the dCDN may pre-position the new content
   then immediately invalidate or purge it (as a result of the two uCDN
   requests running in parallel).

2.2.  Trigger Results

   Each Trigger Request may operate on multiple data items.  The trigger
   MUST NOT be reported as "complete" unless all actions can be
   completed successfully, otherwise it MUST be reported as "failed" or
   "processed".  The reasons for failure and URLs or Patterns affected
   SHOULD be enumerated in the Trigger Status Resource.  For more
   detail, see section Section 4.5.

   If a dCDN is also acting as a 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
   a reference to each Trigger Status Resource in that collection.

   To trigger activity in the dCDN, the uCDN creates a new Trigger
   Status Resource by posting to the 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
   the uCDN.  This immediately enables the uCDN to check the status of
   that trigger.





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   The dCDN MUST present a different set of Trigger Status Resources to
   each interconnected uCDN.  Trigger Status Resources belonging to a
   uCDN MUST NOT be visible to any other client.  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 the uCDN's
   Trigger Status Resources is accessible to the uCDN.  This collection
   lists all of the uCDN triggers 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 section Section 4.3).

   In order to allow the uCDN to check status of multiple jobs in a
   single request, the dCDN SHOULD 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 the dCDN.

   o  Complete - Trigger Status Resources representing activity that
      completed successfully, or for which no further status updates
      will be made by the dCDN.

   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.

   CI/T 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 CI/T
   that contain a response body SHOULD include an ETag to enable
   validation of cached versions of returned resources.






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   Servers implementing CI/T MUST support the HTTP GET, HEAD, POST and
   DELETE methods as defined in [RFC7231].  The only representation
   specified in this document is JSON, [RFC7159].

   The URL of the dCDN's collections of Trigger Status Resources need to
   be either discovered by, or configured in, the uCDN.  The mechanism
   for discovery of those URLs is outside the scope of this document.

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

   The URI of each Trigger Status Resource is returned to the 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 a requested response/representation has not been
   modified, 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.

   The dCDN MUST ensure that activity triggered by the 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.

4.1.  Creating Triggers

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





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   The dCDN validates and authenticates that request, if it is malformed
   or the uCDN does not have sufficient access rights it MAY reject the
   request immediately.  In this case, it MUST respond with an
   appropriate 4xx HTTP error code and a resource MUST NOT be created on
   dCDN.

   If the request is accepted, the uCDN MUST create a new Trigger Status
   Resource.  The HTTP response to the dCDN MUST have status code 201
   and 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 recommended particularly in
   cases where the trigger has completed immediately.

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

   The "request" property of the Trigger Status Resource contains 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 dCDN is not able to track triggered activity, it MUST indicate
   that 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 Triggers.  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
   prepositioning after an earlier delete of the same URLs is expected
   to have finished.

   If the dCDN is able to track triggered activity, the trigger is
   queued by the dCDN for later action, the "status" property of the
   Trigger Status Resource MUST be "pending".  Once trigger processing
   has started the "status" MUST be "active".  Finally, once the
   triggered activity is complete, the trigger status MUST be set to
   "complete" or "failed".

   A trigger 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 prepopulate request for data it has already acquired
   and which 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
   Triggers.




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

4.2.  Checking Status

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

   To check for change in status of a resource or collection of
   resources without re-fetching the whole resource or collection,
   Entity Tags SHOULD be used by the uCDN as cache validators, as
   defined in [RFC7232].

   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

   The 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 the dCDN moves a Trigger Status Resource from the
   Active to the Completed collection, the uCDN may chose to fetch the
   result of that activity.

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

4.2.2.  Polling Trigger Status Resources

   The 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



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   requests for the resource MUST be handled as required by HTTP, and so
   will receive responses with status 404 or 410.

   If a "pending" Trigger Status Resource is deleted, the dCDN SHOULD
   NOT start processing of that activity.  Deleting a "pending" trigger
   does not however guarantee that it is 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 the
   DELETE is processed by the dCDN.

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

   Deletion of a "complete", "processed" or "failed" Trigger Status
   Resource requires no processing in the 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 "complete", "processed" or "failed".  In
   this case, the dCDN will remove the resource and respond to
   subsequent requests for it with HTTP status 404 or 410.

   If the 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 not
   automatically deleted for at least 24 hours after they become
   "complete", "processed" or "failed".

   To ensure it has access to the status of its completed and failed
   triggers, it is recommended that the 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 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



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   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
   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 the dCDN, or the
   dCDN is unable to pass a trigger request on to any of its cascaded
   dCDNs; the dCDN SHOULD report an error if the request is abandoned.
   Otherwise, it SHOULD keep the trigger in state "pending" or "active"
   until it's acted upon or the uCDN chooses to cancel it.  Or, if the
   request is queued and the dCDN will not report further status, the
   dCDN MAY report the trigger as "processed", in which case it SHOULD
   also provide an estimated completion time.

   Note that an "invalidate" trigger 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.  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.



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      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

         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 the dCDN, the 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.




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   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.

   When processing trigger requests, CDNs MUST ignore the URL scheme
   (http or https) in comparing URLs.  For example, for an invalidate or
   purge trigger, content MUST 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

         Description: Time at which the request was received by the
         dCDN.  Time is determined by the 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 determined by the dCDN, there is no requirement to
         synchronise clocks between interconnected CDNs.

         Type: AbsoluteTime

         Mandatory: Yes

      Property: etime

         Description: Estimate of the time at which the dCDN expects to
         complete the activity.  Time is determined by the dCDN, there
         is no requirement to synchronise clocks between interconnected
         CDNs.

         Type: AbsoluteTime



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         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.

      Property: 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 MUST be exactly as they appear in the
         request, the dCDN must not generalise the URLs.  (For example,
         if the uCDN requests prepositioning of URLs
         "http://ucdn.example.com/a" and "http://ucdn.example.com/b",
         the dCDN must not generalise its error report to Pattern
         "http://ucdn.example.com/*").

         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.




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         Mandatory: No.

5.4.  Properties of Trigger Collections

      Property: triggers

         Description: Links to Trigger Status Resources in the
         collection.

         Type: URLs.

         Mandatory: Yes

      Property: staleresourcetime

         Description: The length of time for which the dCDN guarantees
         to keep a completed Trigger Status Resource.  After this time,
         the 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 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.

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 the dCDN to acquire metadata or
      content.

   o  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 re-validating it using, for example,
      an "If-None-Match" HTTP request.  The dCDN need not erase the
      associated data.






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   o  Purge - a request for the 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:

   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.

   o  Processed - the trigger has been accepted and no further status
      update will be made (may be used in cases where completion cannot
      be confirmed).

   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 - the dCDN was unable to acquire metadata required to fulfil
      the request.

   o  ECONTENT - the dCDN was unable to acquire content (preposition
      triggers only).

   o  EPERM - the uCDN does not have permission to trigger the requested
      activity (for example, the data is owned by another CDN).

   o  EREJECT - the 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).





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   o  ECDN - An internal error in the dCDN or one of its downstream
      CDNs.

6.  JSON Encoding of Objects

   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
   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




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         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

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 ? MUST 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



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         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 is 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

         Type: String

         Mandatory: No.



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6.1.5.  ErrorCode

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

6.2.  MIME Media Types

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

    +-------------------+--------------------------------------------+
    | Data Object       | MIME Media Type                            |
    +-------------------+--------------------------------------------+
    | TriggerRequest    | application/cdni.ci.TriggerRequest+json    |
    | TriggerStatus     | application/cdni.ci.TriggerStatus+json     |
    | TriggerCollection | application/cdni.ci.TriggerCollection+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 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 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



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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:

     POST /triggers HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*
     Content-Type: application/cdni.ci.TriggerRequest+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: Wed, 02 Jul 2014 18:57:19 GMT
     Content-Length: 472
     Content-Type: application/cdni.ci.TriggerStatus+json
     Location: http://dcdn.example.com/triggers/0
     Server: example-server/0.1

     {
         "ctime": 1404327439,
         "etime": 1404327447,
         "mtime": 1404327439,



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         "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"
         }
     }

7.1.2.  Invalidate

   An example of an invalidate request, another POST to the
   "AllTriggers" collection.  This instructs the 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/cdni.ci.TriggerRequest+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
             }
           ]
       }



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     }

   RESPONSE:

     HTTP/1.1 201 Created
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Length: 551
     Content-Type: application/cdni.ci.TriggerStatus+json
     Location: http://dcdn.example.com/triggers/1
     Server: example-server/0.1

     {
         "ctime": 1404327440,
         "etime": 1404327448,
         "mtime": 1404327440,
         "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.  Examining Trigger Status

   Once triggers have been created, the 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: 153
     Expires: Wed, 02 Jul 2014 18:58:20 GMT
     Server: example-server/0.1
     Etag: "9179988753593038498"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Type: application/cdni.ci.TriggerCollection+json

     {
         "staleresourcetime": 86400,
         "triggers": [
             "http://dcdn.example.com/triggers/0",
             "http://dcdn.example.com/triggers/1"
         ]
     }

7.2.2.  Filtered Collections of Triggers

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



















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   RREQUEST:

     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: 153
     Expires: Wed, 02 Jul 2014 18:58:20 GMT
     Server: example-server/0.1
     Etag: "5012053611544832286"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Type: application/cdni.ci.TriggerCollection+json

     {
         "staleresourcetime": 86400,
         "triggers": [
             "http://dcdn.example.com/triggers/0",
             "http://dcdn.example.com/triggers/1"
         ]
     }

   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: 56
     Expires: Wed, 02 Jul 2014 18:58:20 GMT
     Server: example-server/0.1
     Etag: "2986340333785000363"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Type: application/cdni.ci.TriggerCollection+json

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

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: Wed, 02 Jul 2014 18:58:20 GMT
     Server: example-server/0.1
     Etag: "-3651695664007658154"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Type: application/cdni.ci.TriggerStatus+json

     {
         "ctime": 1404327439,
         "etime": 1404327447,
         "mtime": 1404327439,
         "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: Wed, 02 Jul 2014 18:58:20 GMT
     Server: example-server/0.1
     Etag: "-7664987687828084413"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Type: application/cdni.ci.TriggerStatus+json

     {
         "ctime": 1404327440,
         "etime": 1404327448,
         "mtime": 1404327440,
         "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: "5012053611544832286"


   RESPONSE:

     HTTP/1.1 304 Not Modified
     Content-Length: 0
     Expires: Wed, 02 Jul 2014 18:58:20 GMT
     Server: example-server/0.1
     Etag: "5012053611544832286"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Type: application/cdni.ci.TriggerCollection+json

   REQUEST:

     GET /triggers/0 HTTP/1.1
     User-Agent: example-user-agent/0.1
     Host: dcdn.example.com
     Accept: */*
     If-None-Match: "-3651695664007658154"


   RESPONSE:

     HTTP/1.1 304 Not Modified
     Content-Length: 0
     Expires: Wed, 02 Jul 2014 18:58:20 GMT
     Server: example-server/0.1
     Etag: "-3651695664007658154"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:20 GMT
     Content-Type: application/cdni.ci.TriggerStatus+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: */*


   RESPONSE:

     HTTP/1.1 200 OK
     Content-Length: 56
     Expires: Wed, 02 Jul 2014 18:58:24 GMT
     Server: example-server/0.1
     Etag: "-4471185573414616962"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:24 GMT
     Content-Type: application/cdni.ci.TriggerCollection+json

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




























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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: 153
     Expires: Wed, 02 Jul 2014 18:58:31 GMT
     Server: example-server/0.1
     Etag: "-1508172875796647067"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:31 GMT
     Content-Type: application/cdni.ci.TriggerCollection+json

     {
         "staleresourcetime": 86400,
         "triggers": [
             "http://dcdn.example.com/triggers/0",
             "http://dcdn.example.com/triggers/1"
         ]
     }

7.2.5.  Cancelling or Removing a Trigger

   To request the dCDN to cancel a Trigger, the 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: Wed, 02 Jul 2014 18:57:31 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: 106
     Expires: Wed, 02 Jul 2014 18:58:31 GMT
     Server: example-server/0.1
     Etag: "-1842390246836476263"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 18:57:31 GMT
     Content-Type: application/cdni.ci.TriggerCollection+json

     {
         "staleresourcetime": 86400,
         "triggers": [
             "http://dcdn.example.com/triggers/1"
         ]
     }







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7.2.6.  Error Reporting

   In this example the uCDN has requested prepositioning of
   "http://newsite.example.com/index.html", but the 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: Wed, 02 Jul 2014 19:16:48 GMT
     Server: example-server/0.1
     Etag: "-6310233270471598826"
     Cache-Control: max-age=60
     Date: Wed, 02 Jul 2014 19:15:48 GMT
     Content-Type: application/cdni.ci.TriggerStatus+json

     {
         "ctime": 1404328544,
         "errors": [
             {
                 "content.urls": [
                     "http://newsite.example.com/index.html"
                 ],
                 "description":
                     "No HostIndex entry found for newsite.example.com",
                 "error": "EMETA"
             }
         ],
         "etime": 1404328552,
         "mtime": 1404328548,
         "status": "active",
         "trigger": {
             "content.urls": [
                 "http://newsite.example.com/index.html"
             ],
             "type": "preposition"
         }
     }




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8.  IANA Considerations

8.1.  CI/T MIME Media Types

   The IANA is requested to allocate the following MIME Media Types in
   the MIME Media Types registry:

   o  application/cdni.ci.TriggerRequest

   o  application/cdni.ci.TriggerStatus

   o  application/cdni.ci.TriggerCollection

   Use of these types is specified in Section 6.2 of the present
   document.

9.  Security Considerations

9.1.  Authentication, Confidentiality, Integrity Protection

   A CI/T dCDN server implementation MUST support TLS transport for HTTP
   (https) as per [RFC2818].  The use of TLS for transport of the CI/T
   interface allows the dCDN and the uCDN to authenticate each other (to
   ensure they are receiving trigger requests from, or reporting status
   to, an authenticated CDN).

   HTTP requests that attempt to access or operate on CI/T data
   belonging to another CDN MUST be rejected using either HTTP "403
   Forbidden" or "404 Not Found".  (Note that in a "diamond"
   configuration, where one uCDN's content can be acquired via more than
   one directly-connected uCDN, it may not be possible for the dCDN to
   determine from which uCDN it acquired content.  In this case, it MUST
   allow each upstream that may have been responsible for acquisition of
   that content to act upon it using trigger requests.)

   Trigger creation requests that attempt to operate on metadata or
   content not acquired from the uCDN making the request MUST be
   rejected.  The rejection can either be signalled to dCDN using HTTP
   "403 Forbidden" or "404 Not Found", or a Trigger Status Resource can
   be created with an ErrorDesc value of EPERM for any affected URLs.

   In an environment where any such protection is required, TLS SHOULD
   be used for transport of the CI/T requests and responses, unless
   alternate methods are used for ensuring that only authorised clients
   are able to access their own data (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).  Both




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   parties of the transaction (the uCDN and the dCDN) SHOULD use mutual
   authentication.

   A CI/T implementation MUST support the
   TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 cipher suite ([RFC5288]).  An
   implementation of the CI/T Interface SHOULD prefer cipher suites
   which support perfect forward secrecy over cipher suites that don't.

9.2.  Denial of Service

   This document does not define a specific mechanism to protect against
   Denial of Service (DoS) attacks on the CI/T.  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 use of Virtual Private Networks (VPNs).

10.  Acknowledgements

   The authors thank Kevin Ma for his ongoing input.

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.

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

   [RFC7159]  Bray, T., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, March 2014.

   [RFC7231]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Semantics and Content", RFC 7231, June 2014.

   [RFC7232]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Conditional Requests", RFC 7232, June 2014.

11.2.  Informative References

   [I-D.ietf-cdni-framework]
              Peterson, L., Davie, B., and R. Brandenburg, "Framework
              for CDN Interconnection", draft-ietf-cdni-framework-14
              (work in progress), June 2014.





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   [I-D.ietf-cdni-metadata]
              Niven-Jenkins, B., Murray, R., Watson, G., Caulfield, M.,
              Leung, K., and K. Ma, "CDN Interconnect Metadata", draft-
              ietf-cdni-metadata-06 (work in progress), February 2014.

   [I-D.ietf-cdni-requirements]
              Leung, K. and Y. Lee, "Content Distribution Network
              Interconnection (CDNI) Requirements", draft-ietf-cdni-
              requirements-17 (work in progress), January 2014.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

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

   [RFC5288]  Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
              Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
              August 2008.

   [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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