One document matched: draft-ietf-cdni-control-triggers-09.xml
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<rfc category="std" docName="draft-ietf-cdni-control-triggers-09"
ipr="trust200902">
<front>
<title abbrev="CDN Interconnect Triggers">CDNI Control Interface /
Triggers</title>
<author fullname="Rob Murray" initials="R" surname="Murray">
<organization>Velocix (Alcatel-Lucent)</organization>
<address>
<postal>
<street>3 Ely Road</street>
<city>Milton</city>
<region>Cambridge</region>
<code>CB24 6DD</code>
<country>UK</country>
</postal>
<email>rob.murray@alcatel-lucent.com</email>
</address>
</author>
<author fullname="Ben Niven-Jenkins" initials="B" surname="Niven-Jenkins">
<organization>Velocix (Alcatel-Lucent)</organization>
<address>
<postal>
<street>3 Ely Road</street>
<city>Milton</city>
<region>Cambridge</region>
<code>CB24 6DD</code>
<country>UK</country>
</postal>
<email>ben.niven-jenkins@alcatel-lucent.com</email>
</address>
</author>
<date day="16" month="October" year="2015"/>
<abstract>
<t>This document describes the part of the CDN Interconnection 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 invalidates or purges metadata or
content. The upstream CDN can monitor the status of activity that it has
triggered in the downstream CDN.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t><xref target="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).</t>
<t><xref target="RFC7336"/> expands on the information provided in <xref
target="RFC6707"/> and describes each of the interfaces and the
relationships between them in more detail.</t>
<t>This document describes the "CI/T" interface, "CDNI Control interface
/ Triggers". It does not consider those parts of the control interface
that relate to configuration, bootstrapping or authentication of CDN
Interconnect interfaces. Section 4 of <xref target="RFC7337"/>
identifies the requirements specific to the CI interface, requirements
applicable to the CI/T interface are CI-1 to CI-6.</t>
<t><list style="symbols">
<t><xref target="model-for-triggers"/> outlines the model for the
CI/T Interface at a high level.</t>
<t><xref target="collections-of-triggers"/> describes collections of
Trigger Status Resources.</t>
<t><xref target="trigger-interface"/> defines the web service
provided by the dCDN.</t>
<t><xref target="properties-of-triggers"/> lists properties of CI/T
Commands and Status Resources.</t>
<t><xref target="examples"/> contains example messages.</t>
</list></t>
<section anchor="terminology" title="Terminology">
<t>This document reuses the terminology defined in <xref
target="RFC6707"/>.</t>
</section>
</section>
<section anchor="model-for-triggers" title="Model for CDNI Triggers">
<t>A CI/T Command, sent from the uCDN to the dCDN, is a request for the
dCDN to do some work relating to data associated with content requests
originating from the uCDN.</t>
<t>There are two types of CI/T Command, CI/T Trigger Commands and CI/T
Cancel Commands. The CI/T Cancel Command can be used to request
cancellation of an earlier CI/T Trigger Command. A CI/T Trigger Command
is of one of the following types:</t>
<t><list style="symbols">
<t>preposition - used to instruct the dCDN to fetch metadata from
the uCDN, or content from any origin including the uCDN.</t>
<t>invalidate - used to instruct the dCDN to revalidate specific
metadata or content before re-using it.</t>
<t>purge - used to instruct the dCDN to delete specific metadata or
content.</t>
</list></t>
<t>The CI/T interface is a web service offered by the dCDN. It allows
CI/T commands to be issued, and triggered activity to be tracked. When
the dCDN accepts a CI/T Command it creates a resource describing status
of the triggered activity, a Trigger Status Resource. The uCDN can poll
Trigger Status Resources to monitor progress.</t>
<t>The dCDN maintains at least one collection of Trigger Status
Resources for each uCDN. Each uCDN only has access to its own
collections, the locations of which are shared when CDN interconnection
is established.</t>
<t>To trigger activity in the dCDN, the uCDN POSTs a CI/T Command to the
collection of Trigger Status Resources. If the dCDN accepts the CI/T
Command, it creates a new Trigger Status Resource and returns its
location to the uCDN. To monitor progress, the uCDN can GET the Trigger
Status Resource. To request cancellation of a CI/T Trigger Command the
uCDN can POST to the collection of Trigger Status Resources, or simply
DELETE the Trigger Status Resource.</t>
<t>In addition to the collection of all Trigger Status Resources for the
uCDN, the dCDN can maintain filtered views of that collection. These
filtered views are defined in <xref target="collections-of-triggers"/>
and include collections of Trigger Status Resources corresponding to
active and completed CI/T Trigger Commands. These collections provide a
mechanism for polling the status of multiple jobs.</t>
<t><xref target="high-level-trigger-flow"/> is an example showing the
basic message flow used by the uCDN to trigger activity in the dCDN, and
for the uCDN to discover the status of that activity. Only successful
triggering is shown. Examples of the messages are given in <xref
target="examples"/>.</t>
<figure anchor="high-level-trigger-flow"
title="Basic CDNI Message Flow for Triggers">
<artwork><![CDATA[ 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 [ ]
[ ] <-------------------------------------------------- [ ]
| |
| |
]]></artwork>
</figure>
<t>The steps in <xref target="high-level-trigger-flow"/> are:</t>
<t><list style="numbers">
<t>The uCDN triggers action in the dCDN by posting a CI/T Command to
a collection of Trigger Status Resources,
"http://dcdn.example.com/triggers/uCDN". The URL of this was given
to the uCDN when the CI/T interface was established.</t>
<t>The dCDN authenticates the request, validates the CI/T Command
and, if it accepts the request, creates a new Trigger Status
Resource.</t>
<t>The dCDN responds to the uCDN with an HTTP 201 response status,
and the location of the Trigger Status Resource.</t>
<t>The uCDN can poll, possibly repeatedly, the Trigger Status
Resource in the dCDN.</t>
<t>The dCDN responds with the Trigger Status Resource, describing
progress or results of the CI/T Trigger Command.</t>
</list></t>
<t>The remainder of this document describes the messages, Trigger Status
Resources, and collections of Trigger Status Resources in more
detail.</t>
<section title="Timing of Triggered Activity">
<t>Timing of the execution of CI/T Commands is under the dCDN's
control, including its start-time and pacing of the activity in the
network.</t>
<t>CI/T invalidate and purge commands MUST be applied to all data
acquired before the command was accepted by the dCDN. The dCDN SHOULD
NOT apply CI/T invalidate and purge commands to data acquired after
the CI/T Command was accepted, but this may not always be achievable
so the uCDN cannot count on that.</t>
<t>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, there is a risk that the dCDN pre-positions
the new content, then immediately invalidates or purges it (as a
result of the two uCDN requests running in parallel).</t>
<t>Because the CI/T Command timing is under the dCDN's control, the
dCDN implementation can choose whether to apply CI/T invalidate and
purge commands to content acquisition that has already started when
the command is received.</t>
</section>
<section title="Scope of Triggered Activity">
<t>Each CI/T Command can operate on multiple metadata and content
URLs.</t>
<t>Multiple representations of an HTTP resource may share the same
URL. CI/T Trigger Commands that invalidate or purge metadata or
content apply to all resource representations with matching URLs.</t>
<t>The dCDN MUST reject CI/T Commands from a uCDN that act on another
uCDN's data. Security considerations are discussed further in section
<xref target="Security"/>.</t>
</section>
<section title="Trigger Results">
<t>Possible states for a Trigger Status Resource are defined in
section <xref target="trigger-status"/>.</t>
<t>The CI/T Trigger Command MUST NOT be reported as 'complete' until
all actions have been completed successfully. The reasons for failure,
and URLs or Patterns affected, SHOULD be enumerated in the Trigger
Status Resource. For more detail, see section <xref
target="error-handling"/>.</t>
<t>If a dCDN is also acting as a uCDN in a cascade, it MUST forward
CI/T Commands to any downstream CDNs that may be affected. The CI/T
Trigger Command MUST NOT be reported as 'complete' in a CDN until it
is 'complete' in all of its downstream CDNs. If a CI/T Trigger Command
is reported as 'processed' in any dCDN, intermediate CDNs MUST NOT
report 'complete', instead they must also report 'processed'. A CI/T
Command MAY be reported as 'failed' as soon as it fails in a CDN or in
any of its downstream CDNs. A cancelled CI/T Trigger Command MUST be
reported as 'cancelling' until it has been reported as 'cancelled',
'complete', or 'failed' by all dCDNs in a cascade.</t>
</section>
</section>
<section anchor="collections-of-triggers"
title="Collections of Trigger Status Resources">
<t>As described in <xref target="model-for-triggers"/>, Trigger Status
Resources exist in the dCDN to report the status of activity triggered
by each uCDN.</t>
<t>A collection of Trigger Status Resources is a resource that contains
a reference to each Trigger Status Resource in that collection.</t>
<t>The dCDN MUST make a collection of a uCDN's Trigger Status Resources
available to that uCDN. This collection includes all of the Trigger
Status Resources created for CI/T Commands from the uCDN that have been
accepted by the dCDN, and have not yet been deleted by the uCDN, or
expired and removed by the dCDN (as described in section <xref
target="deleting-triggers"/>). Trigger Status Resources belonging to a
uCDN MUST NOT be visible to any other CDN. The dCDN could, for example,
achieve this by offering different collection URLs to each uCDN, and/or
by filtering the response based on the uCDN with which the HTTP client
is associated.</t>
<t>To trigger activity in a dCDN, or to cancel triggered activity, the
uCDN POSTs a CI/T Command to the dCDN's collection of the uCDN's Trigger
Status Resources.</t>
<t>In order to allow the uCDN to check the 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. These
filtered collections are optional-to-implement but, if implemented, the
dCDN MUST include links to them in the collection of all Trigger Status
Resources. The filtered collections are:<list style="symbols">
<t>Pending - Trigger Status Resources for CI/T Trigger Commands that
have been accepted, but not yet acted upon.</t>
<t>Active - Trigger Status Resources for CI/T Trigger Commands that
are currently being processed in the dCDN.</t>
<t>Complete - Trigger Status Resources representing activity that
completed successfully, and 'processed' CI/T Trigger Commands for
which no further status updates will be made by the dCDN.</t>
<t>Failed - Trigger Status Resources representing CI/T Commands that
failes or were cancelled by the uCDN.</t>
</list></t>
</section>
<section anchor="trigger-interface" title="CDNI Trigger Interface">
<t>This section describes an interface to enable an upstream CDN to
trigger activity in a downstream CDN.</t>
<t>The CI/T interface builds on top of HTTP, so dCDNs may make use of
any HTTP feature when implementing the CI/T interface. For example, a
dCDN SHOULD make use of HTTP's caching mechanisms to indicate that a
requested response/representation has not been modified, reducing the
uCDN's processing needed to determine whether the status of triggered
activity has changed.</t>
<t>All dCDNs implementing CI/T MUST support the HTTP GET, HEAD, POST and
DELETE methods as defined in <xref target="RFC7231"/>.</t>
<t>The only representation specified in this document is JSON, <xref
target="RFC7159"/>. It MUST be supported by the uCDN and by the
dCDN.</t>
<t>The URL of the dCDN's collection of all Trigger Status Resources
needs to be either discovered by, or configured in, the uCDN. The
mechanism for discovery of that URL is outside the scope of this
document.</t>
<t>CI/T Commands are POSTed to the dCDN's collection of all Trigger
Status Resources. If a CI/T Trigger Command is accepted by the dCDN, the
dCDN creates a new Trigger Status Resource and returns its URI to the
uCDN in an HTTP 201 response. The triggered activity can then be
monitored by the uCDN using that resource and the collections described
in <xref target="collections-of-triggers"/>.</t>
<t>The URI of each Trigger Status Resource is returned to the uCDN when
it is created, and URIs of all Trigger Status Resources are listed in
the dCDN's collection of all Trigger Status Resources. This means all
Trigger Status Resources can be discovered by the uCDN, so dCDNs are
free to assign whatever structure they desire to the URIs for CI/T
resources. Therefore uCDNs MUST NOT make any assumptions regarding the
structure of CI/T URIs or the mapping between CI/T objects and their
associated URIs. URIs present in the examples in this document are
purely illustrative and are not intended to impose a definitive
structure on CI/T interface implementations.</t>
<section title="Creating Triggers">
<t>To issue a CI/T Command, the uCDN makes an HTTP POST to the dCDN's
collection of all of the uCDN's Trigger Status Resources. The request
body of that POST is a CI/T Command, as described in <xref
target="properties-of-trigger-commands"/>.</t>
<t>The dCDN validates the CI/T Command, if it is malformed or the uCDN
does not have sufficient access rights it MUST either respond with an
appropriate 4xx HTTP error code and a Trigger Status Resource MUST NOT
be created on the dCDN, or create a 'failed' Trigger Status Resource
containing an appropriate error description.</t>
<t>When a CI/T Trigger Command is accepted, the uCDN MUST create a new
Trigger Status Resource which will convey a specification of the CI/T
Command and its current status. The HTTP response to the dCDN MUST
have status code 201 and MUST convey the URI of the Trigger Status
Resource in the Location header field. The HTTP response SHOULD
include the content of the newly created Trigger Status Resource, this
is recommended particularly in cases where the CI/T Trigger Command
has completed immediately.</t>
<t>Once a Trigger Status Resource has been created the dCDN MUST NOT
re-use its URI, even after that Trigger Status Resource has been
removed.</t>
<t>The dCDN SHOULD track and report on progress of CI/T Trigger
Commands. If the dCDN is not able to do that, it MUST indicate that it
has accepted the request but will not be providing further status
updates. To do this, it sets the "status" of the Trigger Status
Resource to "processed". In this case, CI/T processing should continue
as for a "complete" request, so the Trigger Status Resource MUST be
added to the dCDN's collection of Complete Trigger Status Resources.
The dCDN SHOULD also provide an estimated completion time for the
request, by using the "etime" property of the Trigger Status Resource.
This will allow the uCDN to schedule prepositioning after an earlier
delete of the same URLs is expected to have finished.</t>
<t>If the dCDN is able to track the execution of CI/T Commands and a
CI/T Command is queued by the dCDN for later action, the "status"
property of the Trigger Status Resource MUST be "pending". Once
processing has started the "status" MUST be "active". Finally, once
the CI/T Command is complete, the status MUST be set to "complete" or
"failed".</t>
<t>A CI/T Trigger Command may result in no activity in the dCDN if,
for example, it is an invalidate or purge request for data the dCDN
has not yet acquired, or a 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 Trigger Status Resources.</t>
<t>Once created, Trigger Status Resources can be cancelled or deleted
by the uCDN, but not modified. The dCDN MUST reject PUT and POST
requests from the uCDN to Trigger Status Resources by responding with
an appropriate HTTP status code, for example 405 "Method Not
Allowed".</t>
</section>
<section title="Checking Status">
<t>The uCDN has two ways to check progress of CI/T Commands it has
issued to the dCDN, described in sections <xref
target="polling-collections"/> and <xref
target="polling-trigger-status-resources"/>.</t>
<t>To check for change in status of a Trigger Status Resource or
collection of Trigger Status Resources without re-fetching the whole
Resource or Collection, Entity Tags SHOULD be included by the dCDN for
the uCDN to use as cache validators, as defined in <xref
target="RFC7232"/>.</t>
<t>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 the uCDN should poll for change.</t>
<section anchor="polling-collections"
title="Polling Trigger Status Resource collections">
<t>The uCDN can fetch the collection of its Trigger Status
Resources, or filtered views of that collection.</t>
<t>This makes it possible to poll status of all CI/T Trigger
Commands in a single request. If the dCDN moves a Trigger Status
Resource from the Active to the Completed collection, the uCDN can
fetch the result of that activity.</t>
<t>When polling in this way, the uCDN SHOULD use HTTP Entity Tags to
monitor for change, rather than repeatedly fetching the whole
collection. An example of this is given in section <xref
target="polling-for-change"/>.</t>
</section>
<section anchor="polling-trigger-status-resources"
title="Polling Trigger Status Resources">
<t>The uCDN has a URI provided by the dCDN for each Trigger Status
Resource it has created, it may fetch that Trigger Status Resource
at any time.</t>
<t>This can be used to retrieve progress information, and to fetch
the result of the CI/T Command.</t>
<t>When polling in this way, the uCDN SHOULD use HTTP Entity Tags to
monitor for change, rather than repeatedly fetching the Trigger
Status Resource.</t>
</section>
</section>
<section anchor="cancelling-triggers" title="Cancelling Triggers">
<t>The uCDN can request cancellation of a CI/T Trigger Command by
POSTing a CI/T Cancel Command to the collection of all Trigger Status
Resources.</t>
<t>Cancellation of a CI/T Trigger Command is optional-to-implement in
the dCDN.</t>
<t>The dCDN MUST respond to the CI/T Cancel Command appropriately, for
example with HTTP status code 200 "OK" if the cancellation has been
processed and the CI/T Command is inactive, 202 "Accepted" if the
command has been accepted but the CI/T Command remains active, or 501
"Not Implemented" if cancellation is not supported by the dCDN.</t>
<t>If cancellation of a "pending" Trigger Status Resource is accepted
by the dCDN, the dCDN SHOULD NOT start processing of that activity.
Issuing a CT/T cancel command for a "pending" Trigger Status Resource
does not however guarantee that the corresponding activity will not be
started, because the uCDN cannot control the timing of that activity.
Processing could, for example, start after the POST is sent by the
uCDN but before that request is processed by the dCDN.</t>
<t>If cancellation of an "active" or "processed" Trigger Status
Resource is accepted by the dCDN, the dCDN SHOULD stop processing the
CI/T Command. However, as with cancellation of a "pending" CI/T
Command, the dCDN does not guarantee this.</t>
<t>If the CI/T Command cannot be stopped immediately, the status in
the corresponding Trigger Status Resource MUST be set to "cancelling",
and the Trigger Status Resource MUST remain in the collection of
Trigger Status Resources for active CI/T Commands. If processing is
stopped before normal completion, the status value in the Trigger
Status Resource MUST be set to "cancelled", and the Trigger Status
Resource MUST be included in the collection of failed CT/T Trigger
Commands.</t>
<t>Cancellation of a "complete" or "failed" Trigger Status Resource
requires no processing in the dCDN, its status MUST NOT be changed to
"cancelled".</t>
</section>
<section anchor="deleting-triggers" title="Deleting Triggers">
<t>The uCDN can delete Trigger Status Resources at any time, using the
HTTP DELETE method. The effect is similar to cancellation, but no
Trigger Status Resource remains afterwards.</t>
<t>Once deleted, the references to a Trigger Status Resource MUST be
removed from all Trigger Status Resource collections. Subsequent
requests to GET the deleted Trigger Status Resource SHOULD be rejected
by the dCDN with an HTTP error.</t>
<t>If a "pending" Trigger Status Resource is deleted, the dCDN SHOULD
NOT start processing of that activity. Deleting a "pending" Trigger
Status Resource does not however guarantee that it has not started
because the uCDN cannot control the timing of that activity.
Processing may, for example, start after the DELETE is sent by the
uCDN but before that request is processed by the dCDN.</t>
<t>If an "active" or "processed" Trigger Status Resource is deleted,
the dCDN SHOULD stop processing the CI/T Command. However, as with
deletion of a "pending" Trigger Status Resource, the dCDN does not
guarantee this.</t>
<t>Deletion of a "complete" or "failed" Trigger Status Resource
requires no processing in the dCDN other than deletion of the Trigger
Status Resource.</t>
</section>
<section title="Expiry of Trigger Status Resources">
<t>The dCDN can choose to automatically delete Trigger Status
Resources some time after they become "complete", "processed",
"failed" or "cancelled". In this case, the dCDN will remove the
Trigger Status Resource and respond to subsequent requests for it with
an HTTP error.</t>
<t>If the dCDN performs this housekeeping, it MUST have reported the
length of time after which completed Trigger Status Resources will be
deleted via a property of the collection of all Trigger Status
Resources. It is RECOMMENDED that Trigger Status Resources are not
automatically deleted by the dCDN for at least 24 hours after they
become "complete", "processed", "failed" or "cancelled".</t>
<t>To ensure it is able to get the status of its Trigger Status
Resources for completed and failed CI/T Commands, it is RECOMMENDED
that the uCDN polling interval is less than the time after which
records for completed activity will be deleted.</t>
</section>
<section anchor="loops" title="Loop Detection and Prevention">
<t>Given three CDNs, A, B and C. If CDNs B and C delegate delivery of
CDN A's content to each other, CDN A's CI/T Commands could be passed
between CDNs B and C in a loop. More complex networks of CDNs could
contain similar loops involving more hops.</t>
<t>In order to prevent and detect such CI/T loops, each CDN uses a CDN
Provider ID to uniquely identify itself. In every CI/T Command it
originates or cascades, each CDN MUST append an array element
containing its CDN Provider ID to a JSON array under an entry named
"cdn-path". When receiving CI/T Commands a dCDN MUST check the
cdn-path and reject any CI/T Command which already contains its own
CDN Provider ID in the cdn-path. Transit CDNs MUST check the cdn-path
and not cascade the CI/T Command to dCDNs that are already listed in
cdn-path.</t>
<t>The CDN Provider Id consists of the two characters "AS" followed by
the CDN Provider's Autonomous System number, then a colon (':') and an
additional qualifier that is used to guarantee uniqueness in case a
particular AS has multiple independent CDNs deployed. For example
"AS64496:0".</t>
<t>If the CDN provider has multiple Autonomous Systems, the same AS
number SHOULD be used in all messages from that CDN provider, unless
there are multiple distinct CDNs.</t>
<t>If the RI interface described in <xref
target="I-D.ietf-cdni-redirection"/> is implemented by the dCDN, the
CI/T and RI interfaces SHOULD use the same CDN Provider Id.</t>
</section>
<section anchor="error-handling" title="Error Handling">
<t>A dCDN can signal rejection of a CI/T Command using HTTP status
codes. For example, 400 if the request is malformed, or 403 or 404 if
the uCDN does not have permission to issue CI/T Commands or it is
trying to act on another CDN's data.</t>
<t>If any part of the CI/T Trigger Command fails, the trigger SHOULD
be reported as "failed" once its activity is complete or if no further
errors will be reported. The "errors" property in the Trigger Status
Resource will be used to enumerate which actions failed and the
reasons for failure, and can be present while the Trigger Status
Resource is still "pending" or "active", if the CI/T Trigger Command
is still running for some URLs or Patterns in the Trigger
Specification.</t>
<t>Once a request has been accepted, processing errors are reported in
the Trigger Status Resource using a list of Error Descriptions. Each
Error Description is used to report errors against one or more of the
URLs or Patterns in the Trigger Specification.</t>
<t>If a surrogate affected by a CI/T Trigger Command is offline in the
dCDN, or the dCDN is unable to pass a CI/T Command on to any of its
cascaded dCDNs:<list style="symbols">
<t>If the CI/T Command is abandoned by the dCDN, the dCDN SHOULD
report an error.</t>
<t>A CI/T "invalidate" command may be reported as "complete" when
surrogates that may have the data are offline. In this case,
surrogates MUST NOT use the affected data without first
revalidating it when they are back online.</t>
<t>CI/T "preposition" and "purge" commands can be reported as
"processed" if affected caches are offline and the activity will
complete when they return to service.</t>
<t>Otherwise, the dCDN SHOULD keep the Trigger Status Resource in
state "pending" or "active" until the CI/T Command is acted upon,
or the uCDN chooses to cancel it.</t>
</list></t>
</section>
<section anchor="content-urls" title="Content URLs">
<t>Therefore, if content URLs are transformed by an intermediate CDN
in a cascade, that intermediate CDN MUST transform URLs in CI/T
Commands it passes to its dCDN.</t>
<t>When processing Trigger Specifications, CDNs MUST ignore the URL
scheme (http or https) in comparing URLs. For example, for a CI/T
invalidate or purge command, content MUST be invalidated or purged
regardless of the protocol clients use to request it.</t>
</section>
</section>
<section anchor="properties-of-triggers"
title="CI/T Object Properties and Encoding">
<t>CI/T Commands, Trigger Status Resources and Trigger Collections and
their properties are encoded using JSON, as defined in sections <xref
target="properties-of-trigger-commands"/>, <xref
target="properties-of-trigger-specs"/>, and <xref
target="properties-of-trigger-resources"/>. They MUST use the MIME Media
Type 'application/cdni', with parameter 'ptype' values as defined below
and in <xref target="media-types"/>.</t>
<t>Names in JSON are case sensitive. The names and literal values
specified in the present document MUST always use lower-case.</t>
<t>JSON types, including 'object', 'array', 'number' and 'string' are
defined in <xref target="RFC7159"/>.</t>
<t>Unrecognised name/value pairs in JSON objects SHOULD NOT be treated
as an error by either the uCDN or dCDN. They SHOULD be ignored in the
processing, and passed on by dCDN to any further dCDNs in a cascade.</t>
<section anchor="cit-objects" title="CI/T Objects">
<t>The top-level objects defined by the CI/T interface are described
in this section.</t>
<t>The encoding of values used by these objects is described in <xref
target="properties-of-objects"/>.</t>
<section anchor="properties-of-trigger-commands" title="CI/T Commands">
<t>CI/T Commands MUST use a MIME Media Type of 'application/cdni;
ptype=ci-trigger-command'.</t>
<t>A CI/T Command is encoded as a JSON object containing the
following name/value pairs.</t>
<t><list style="empty">
<t>Name: trigger<list style="empty">
<t>Description: A specification of the trigger type, and a
set of data to act upon.</t>
<t>Value: A Trigger Specification, as defined in <xref
target="properties-of-trigger-specs"/>.</t>
<t>Mandatory: No, but exactly one of "trigger" or "cancel"
MUST be present in a CI/T Command.</t>
</list></t>
</list><list style="empty">
<t>Name: cancel<list style="empty">
<t>Description: The URLs of Trigger Status Resources for
CI/T Trigger Commands that the uCDN wants to cancel.</t>
<t>Value: A non-empty JSON array of URLs represented as JSON
strings.</t>
<t>Mandatory: No, but exactly one of "trigger" or "cancel"
MUST be present in a CI/T Command.</t>
</list></t>
</list><list style="empty">
<t>Name: cdn-path<list style="empty">
<t>Description: The CDN Provider Identifiers of CDNs that
have already accepted the CI/T Command.</t>
<t>Value: A non-empty JSON array of JSON strings, where each
string is a CDN Provider Identifier as defined in <xref
target="loops"/>.</t>
<t>Mandatory: Yes.</t>
</list></t>
</list></t>
</section>
<section anchor="properties-of-trigger-resources"
title="Trigger Status Resource">
<t>Trigger Status Resources MUST use a MIME Media Type of
'application/cdni; ptype=ci-trigger-status'.</t>
<t>A Trigger Status Resource is encoded as a JSON object containing
the following name/value pairs.<list style="empty">
<t>Name: trigger<list style="empty">
<t>Description: The Trigger Specification posted in the body
of the CI/T Command. Note that this need not be a
byte-for-byte copy. For example, in the JSON representation
the dCDN may re-serialise the information differently.</t>
<t>Value: A Trigger Specification, as defined in <xref
target="properties-of-trigger-specs"/>.</t>
<t>Mandatory: Yes</t>
</list></t>
</list></t>
<t><list style="empty">
<t>Name: ctime<list style="empty">
<t>Description: Time at which the CI/T Command was received
by the dCDN. Time is determined by the dCDN, there is no
requirement to synchronise clocks between interconnected
CDNs.</t>
<t>Value: Absolute Time, as defined in <xref
target="absolute-time"/>.</t>
<t>Mandatory: Yes</t>
</list></t>
</list></t>
<t><list style="empty">
<t>Name: mtime<list style="empty">
<t>Description: Time at which the Trigger Status Resource
was last modified. Time is determined by the dCDN, there is
no requirement to synchronise clocks between interconnected
CDNs.</t>
<t>Value: Absolute Time, as defined in <xref
target="absolute-time"/>.</t>
<t>Mandatory: Yes</t>
</list></t>
</list><list style="empty">
<t>Name: etime<list style="empty">
<t>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.</t>
<t>Value: Absolute Time, as defined in <xref
target="absolute-time"/>.</t>
<t>Mandatory: No</t>
</list></t>
</list></t>
<t><list style="empty">
<t>Name: status<list style="empty">
<t>Description: Current status of the triggered
activity.</t>
<t>Value: Trigger Status, as defined in <xref
target="trigger-status"/>.</t>
<t>Mandatory: Yes</t>
</list></t>
</list></t>
<t><list style="empty">
<t>Name: errors<list style="empty">
<t>Description: Descriptions of errors that have occurred
while processing a Trigger Command.</t>
<t>Value: An array of Error Description, as defined in <xref
target="properties-of-errordesc"/>. An empty array is
allowed, and equivalent to omitting "errors" from the
object.</t>
<t>Mandatory: No.</t>
</list></t>
</list></t>
</section>
<section anchor="properties-of-trigger-collections"
title="Trigger Collection">
<t>Trigger Collections MUST use a MIME Media Type of
'application/cdni; ptype=ci-trigger-collection'.</t>
<t>A Trigger Collection is encoded as a JSON object containing the
following name/value pairs.</t>
<t><list style="empty">
<t>Name: triggers<list style="empty">
<t>Description: Links to Trigger Status Resources in the
collection.</t>
<t>Value: A JSON array of zero or more URLs, represented as
JSON strings.</t>
<t>Mandatory: Yes</t>
</list></t>
</list><list style="empty">
<t>Name: staleresourcetime<list style="empty">
<t>Description: The length of time for which the dCDN
guarantees to keep a completed Trigger Status Resource.
After this time, the dCDN SHOULD delete the Trigger Status
Resource and all references to it from collections.</t>
<t>Value: A JSON number, which must be a positive integer,
representing time in seconds.</t>
<t>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.</t>
</list></t>
</list><list style="empty">
<t>Names: coll-all, coll-pending, coll-active, coll-complete,
coll-failed<list style="empty">
<t>Description: Link to a Trigger Collection.</t>
<t>Value: A URL represented as a JSON string.</t>
<t>Mandatory: Links to all of the filtered collections are
mandatory in the collection of all Trigger Status Resources,
if the dCDN implements the filtered collections. Otherwise,
optional.</t>
</list></t>
</list><list style="empty">
<t>Name: cdn-id<list style="empty">
<t>Description: The CDN Provider Identifier of the dCDN.</t>
<t>Value: A JSON string, the dCDN's CDN Provider Identifier,
as defined in <xref target="loops"/>.</t>
<t>Mandatory: Only in the collection of all Trigger Status
Resources, if the dCDN implements the filtered collections.
Optional in the filtered collections (the uCDN can always
find the dCDN's cdn-id in the collection of all Trigger
Status Resources, but the dCDN can choose to repeat that
information in its implementation of filtered
collections).</t>
</list></t>
</list></t>
</section>
</section>
<section anchor="properties-of-objects"
title="Properties of CI/T Objects">
<t>This section defines the values that can appear in the top level
objects described in <xref target="cit-objects"/>, and their
encodings.</t>
<section anchor="properties-of-trigger-specs"
title="Trigger Specification">
<t>A Trigger Collection is encoded as a JSON object containing the
following name/value pairs.</t>
<t>An unrecognised name/value pair in the Trigger Specification
object contained in a CI/T Command SHOULD be preserved in the
Trigger Specification of any Trigger Status Resource it creates.</t>
<t><list style="empty">
<t>Name: type<list style="empty">
<t>Description: This property defines the type of the CI/T
Trigger Command.</t>
<t>Value: Trigger Type, as defined in <xref
target="trigger-type"/>.</t>
<t>Mandatory: Yes</t>
</list></t>
</list></t>
<t><list style="empty">
<t>Name: metadata.urls<list style="empty">
<t>Description: The uCDN URLs of the metadata the CI/T
Trigger Command applies to.</t>
<t>Value: A JSON array of URLs represented as JSON
strings.</t>
<t>Mandatory: No, but at least one of 'metadata.*' or
'content.*' MUST be present and non-empty.</t>
</list></t>
</list><list style="empty">
<t>Name: content.urls<list style="empty">
<t>Description: URLs of content the CI/T Trigger Command
applies to, see <xref target="content-urls"/>.</t>
<t>Value: A JSON array of URLs represented as JSON
strings.</t>
<t>Mandatory: No, but at least one of 'metadata.*' or
'content.*' MUST be present and non-empty.</t>
</list></t>
</list><list style="empty">
<t>Name: content.ccid<list style="empty">
<t>Description: The Content Collection Identifier of content
the trigger applies to. The 'ccid' is a grouping of content,
as defined by <xref target="I-D.ietf-cdni-metadata"/>.</t>
<t>Value: A JSON array of strings, where each string is a
Content Collection Identifier.</t>
<t>Mandatory: No, but at least one of 'metadata.*' or
'content.*' MUST be present and non-empty.</t>
</list></t>
</list><list style="empty">
<t>Name: metadata.patterns<list style="empty">
<t>Description: The metadata the trigger applies to.</t>
<t>Value: A JSON array of Pattern Match, as defined in <xref
target="pattern-match"/>.</t>
<t>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.</t>
</list></t>
</list><list style="empty">
<t>Name: content.patterns<list style="empty">
<t>Description: The content data the trigger applies to.</t>
<t>Value: A JSON array of Pattern Match, as defined in <xref
target="pattern-match"/>.</t>
<t>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.</t>
</list></t>
</list></t>
</section>
<section anchor="trigger-type" title="Trigger Type">
<t>Trigger Type is used in a Trigger Specification to describe
trigger action. It MUST be one of the JSON strings in the following
table:</t>
<texttable>
<ttcol>JSON String</ttcol>
<ttcol>Description</ttcol>
<c>preposition</c>
<c>A request for the dCDN to acquire metadata or content.</c>
<c>invalidate</c>
<c>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.</c>
<c>purge</c>
<c>A request for the dCDN to erase metadata or content. After
servicing the request, the specified data MUST NOT be held on the
dCDN (the dCDN should re-acquire the metadata or content from uCDN
if it needs it).</c>
</texttable>
</section>
<section anchor="trigger-status" title="Trigger Status">
<t>This describes the current status of a Trigger. It MUST be one of
the JSON strings in the following table:</t>
<texttable>
<ttcol>JSON String</ttcol>
<ttcol>Description</ttcol>
<c>pending</c>
<c>The CI/T Trigger Command has not yet been acted upon.</c>
<c>active</c>
<c>The CI/T Trigger Command is currently being acted upon.</c>
<c>complete</c>
<c>The CI/T Trigger Command completed successfully.</c>
<c>processed</c>
<c>The CI/T Trigger Command has been accepted and no further
status update will be made (can be used in cases where completion
cannot be confirmed).</c>
<c>failed</c>
<c>The CI/T Trigger Command could not be completed.</c>
<c>cancelling</c>
<c>Processing of the CI/T Trigger Command is still in progress,
but the CI/T Trigger Command has been cancelled by the uCDN.</c>
<c>cancelled</c>
<c>The CI/T Trigger Command was cancelled by the uCDN.</c>
</texttable>
</section>
<section anchor="pattern-match" title="PatternMatch">
<t>A Pattern Match consists of a string pattern to match, and flags
describing the type of match.</t>
<t>It is encoded as a JSON object with the following name/value
pairs:</t>
<t><list style="empty">
<t>Name: pattern<list style="empty">
<t>Description: A pattern for string matching.</t>
<t>Value: A JSON string representing the pattern. 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 "\?".</t>
<t>Mandatory: Yes.</t>
</list>Name: case-sensitive<list style="empty">
<t>Description: Flag indicating whether or not
case-sensitive matching should be used.</t>
<t>Value: One of the JSON values 'true' or 'false'.</t>
<t>Mandatory: No, default is case-insensitive match.</t>
</list>Name: match-query-string<list style="empty">
<t>Description: Flag indicating whether or not the query
string should be included in the pattern match.</t>
<t>Value: One of the JSON values 'true' or 'false'.</t>
<t>Mandatory: No, default is not to include the query string
in the pattern match.</t>
</list></t>
</list>Example of case-sensitive prefix match against
"http://www.example.com/trailers/":</t>
<figure>
<artwork><![CDATA[{
"pattern": "http://www.example.com/trailers/*",
"case-sensitive": true
}]]></artwork>
</figure>
</section>
<section anchor="absolute-time" title="Absolute Time">
<t>A JSON number, seconds since the UNIX epoch.</t>
</section>
<section anchor="properties-of-errordesc" title="Error Description">
<t>An Error Description is used to report failure of a CI/T Command,
or in the activity it triggered. It is encoded as a JSON object with
the following name/value pairs:<list style="empty">
<t>Name: error<list style="empty">
<t>Value: Error Code, as defined in <xref
target="error-codes"/>.</t>
<t>Mandatory: Yes.</t>
</list></t>
</list><list style="empty">
<t>Names: metadata.urls, content.urls, metadata.patterns,
content.patterns<list style="empty">
<t>Description: Metadata and content references copied from
the Trigger Specification. Only those URLs and patterns to
which the error applies are 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://content.example.com/a" and
"http://content.example.com/b", the dCDN must not generalise
its error report to Pattern
"http://content.example.com/*".)</t>
<t>Value: A JSON array of JSON strings, where each string is
copied from a 'content.*' or 'metadata.*' value in the
corresponding Trigger Specification.</t>
<t>Mandatory: At least one of these name/value pairs is
mandatory in each Error Description object.</t>
</list></t>
</list><list style="empty">
<t>Name: description<list style="empty">
<t>Description: A human-readable description of the
error.</t>
<t>Value: A JSON string, the human-readable description.</t>
<t>Mandatory: No.</t>
</list></t>
</list></t>
</section>
<section anchor="error-codes" title="Error Code">
<t>This type is used by the dCDN to report failures in trigger
processing.</t>
<texttable>
<ttcol>Error Code</ttcol>
<ttcol>Description</ttcol>
<c>emeta</c>
<c>The dCDN was unable to acquire metadata required to fulfil the
request.</c>
<c>econtent</c>
<c>The dCDN was unable to acquire content (CT/T preposition
commands only).</c>
<c>eperm</c>
<c>The uCDN does not have permission to issue the CI/T Command
(for example, the data is owned by another CDN).</c>
<c>ereject</c>
<c>The dCDN is not willing to fulfil the CI/T Command (for
example, a preposition request for content at a time when the dCDN
would not accept Request Routing requests from the uCDN).</c>
<c>ecdn</c>
<c>An internal error in the dCDN or one of its downstream
CDNs.</c>
<c>ecancelled</c>
<c>The uCDN cancelled the request.</c>
</texttable>
</section>
</section>
<section anchor="json-formalization"
title="Formalization of the JSON Data">
<t>The JSON data described in this document has been formalised using
CDDL <xref target="I-D.greevenbosch-appsawg-cbor-cddl"/> as
follows:</t>
<figure>
<artwork><![CDATA[CIT-object = CIT-command / Trigger-Status-Resource / Trigger-Collection
CIT-command ; use media type application/cdni; ptype=ci-trigger-command
= {
? trigger: Triggerspec
? cancel: [* URI]
cdn-path: [* Cdn-PID]
}
Trigger-Status-Resource ; application/cdni; ptype=ci-trigger-status
= {
trigger: Triggerspec
ctime: Absolute-Time
mtime: Absolute-Time
? etime: Absolute-Time
status: Trigger-Status
? errors: [* Error-Description]
}
Trigger-Collection ; application/cdni; ptype=ci-trigger-collection
= {
triggers: [* URI]
? staleresourcetime: int ; time in seconds
? coll-all: URI
? coll-pending: URI
? coll-active: URI
? coll-complete: URI
? coll-failed: URI
? cdn-id: Cdn-PID
}
Triggerspec = { ; 5.2.1
type: Trigger-Type
? metadata.urls: [* URI]
? content.urls: [* URI]
? content.ccid: [* Ccid]
? metadata.patterns: [* Pattern-Match]
? content.patterns: [* Pattern-Match]
}
Trigger-Type = "preposition" / "invalidate" / "purge" ; 5.2.2
Trigger-Status = "pending" / "active" / "complete" / "processed"
/ "failed" / "cancelling" / "cancelled" ; 5.2.3
Pattern-Match = { ; 5.2.4
pattern: tstr
? case-sensitive: bool
? match-query-string: bool
}
Absolute-Time = number ; seconds since UNIX epoch, 5.2.5
Error-Description = { ; 5.2.6
error: Error-Code
? metadata.urls: [* URI]
? content.urls: [* URI]
? metadata.patterns: [* Pattern-Match]
? content.patterns: [* Pattern-Match]
? description: tstr
}
Error-Code = "emeta" / "econtent" / "eperm" / "ereject"
/ "ecdn" / "ecancelled" ; 5.2.7
Ccid = tstr ; see I-D.ietf-cdni-metadata
Cdn-PID = tstr .regexp "AS[0-9]+:[0-9]+"
URI = tstr
]]></artwork>
</figure>
</section>
</section>
<section anchor="examples" title="Examples">
<t>The following sections provide examples of different CI/T objects
encoded as JSON.</t>
<t>Discovery of the triggers interface is out of scope of this document.
In an implementation, all CI/T URLs are under the control of the dCDN.
The uCDN MUST NOT attempt to ascribe any meaning to individual elements
of the path.</t>
<t>In examples in this section, the URL
'http://dcdn.example.com/triggers' is used as the location of the
collection of all Trigger Status Resources, and the CDN Provider Id of
uCDN is "AS64496:1".</t>
<section title="Creating Triggers">
<t>Examples of the uCDN triggering activity in the dCDN:</t>
<section title="Preposition">
<t>An example of a CI/T preposition command, a POST to the
collection of all Trigger Status Resources.</t>
<t>Note that "metadata.patterns" and "content.patterns" are not
allowed in a preposition Trigger Specification.</t>
<figure>
<artwork><![CDATA[REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/cdni; ptype=ci-trigger-command
Content-Length: 347
{
"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"
]
},
"cdn-path" : [ "AS64496:1" ]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Sun, 31 Aug 2014 09:53:18 GMT
Content-Length: 472
Content-Type: application/cdni; ptype=ci-trigger-status
Location: http://dcdn.example.com/triggers/0
Server: example-server/0.1
{
"ctime": 1409478798,
"etime": 1409478806,
"mtime": 1409478798,
"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"
}
}]]></artwork>
</figure>
</section>
<section title="Invalidate">
<t>An example of a CI/T invalidate command, another POST to the
collection of all Trigger Status Resources. 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/" using case-insensitive matching,
and "http://www.example.com/a/b/" respectively, using case-sensitive
matching.</t>
<figure>
<artwork><![CDATA[REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/cdni; ptype=ci-trigger-command
Content-Length: 384
{
"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
}
]
},
"cdn-path" : [ "AS64496:1" ]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Length: 551
Content-Type: application/cdni; ptype=ci-trigger-status
Location: http://dcdn.example.com/triggers/1
Server: example-server/0.1
{
"ctime": 1409478799,
"etime": 1409478807,
"mtime": 1409478799,
"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"
}
}]]></artwork>
</figure>
</section>
</section>
<section title="Examining Trigger Status">
<t>Once Trigger Status Resources have been created, the uCDN can check
their status as shown in these examples.</t>
<section title="Collection of All Triggers">
<t>The uCDN can fetch the collection of all Trigger Status Resources
it has created that 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:</t>
<figure>
<artwork><![CDATA[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: 347
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "-6516741166528256414"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"cdn-id": "AS64496:0",
"coll-active": "/triggers/active",
"coll-complete": "/triggers/complete",
"coll-failed": "/triggers/failed",
"coll-pending": "/triggers/pending",
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}]]></artwork>
</figure>
</section>
<section title="Filtered Collections of Trigger Status Resources">
<t>The filtered collections are also available to the uCDN. Before
the dCDN starts processing the two CI/T Trigger Commands shown
above, both will appear in the collection of Pending Triggers, for
example:</t>
<figure>
<artwork><![CDATA[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: 153
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "5012053611544832286"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}]]></artwork>
</figure>
<t/>
<t>At this point, if no other Trigger Status Resources had been
created, the other filtered views would be empty. For example:</t>
<figure>
<artwork><![CDATA[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: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "2986340333785000363"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": []
}]]></artwork>
</figure>
<t/>
</section>
<section title="Individual Trigger Status Resources">
<t>The Trigger Status Resources can also be examined for detail
about individual CI/T Trigger Commands. For example, for the CI/T
"preposition" and "invalidate" commands from previous examples:</t>
<figure>
<artwork><![CDATA[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: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "-4765587034697674779"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1409478798,
"etime": 1409478806,
"mtime": 1409478798,
"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"
}
}]]></artwork>
</figure>
<t/>
<figure>
<artwork><![CDATA[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: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "-7657333837290433420"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1409478799,
"etime": 1409478807,
"mtime": 1409478799,
"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"
}
}]]></artwork>
</figure>
</section>
<section anchor="polling-for-change" title="Polling for Change">
<t>The uCDN SHOULD use the Entity Tags of collections or Trigger
Status Resources when polling for change in status, as shown in the
following examples:</t>
<figure>
<artwork><![CDATA[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: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "5012053611544832286"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection]]></artwork>
</figure>
<figure>
<artwork><![CDATA[REQUEST:
GET /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
If-None-Match: "-4765587034697674779"
RESPONSE:
HTTP/1.1 304 Not Modified
Content-Length: 0
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "-4765587034697674779"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-status]]></artwork>
</figure>
<t/>
<t>When the CI/T Trigger Command is complete, the contents of the
filtered collections will be updated along with their Entity Tags.
For example, when the two example CI/T Trigger Commands are
complete, the collections of pending and complete Trigger Status
Resources might look like:</t>
<figure>
<artwork><![CDATA[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/1.1 200 OK
Content-Length: 56
Expires: Sun, 31 Aug 2014 09:54:29 GMT
Server: example-server/0.1
Etag: "-4471185573414616962"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:29 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": []
}]]></artwork>
</figure>
<t/>
<figure>
<artwork><![CDATA[REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
If-None-Match: "2986340333785000363"
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 153
Expires: Sun, 31 Aug 2014 09:54:30 GMT
Server: example-server/0.1
Etag: "-1508172875796647067"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:30 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}]]></artwork>
</figure>
</section>
<section title="Deleting Trigger Status Resources">
<t>The dCDN can delete completed and failed Trigger Status Resources
to reduce the size of the collections. For example, to delete the
"preposition" request from earlier examples:</t>
<figure>
<artwork><![CDATA[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: Sun, 31 Aug 2014 09:53:30 GMT
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Server: example-server/0.1]]></artwork>
</figure>
<t/>
<t>This would, for example, cause the collection of completed
Trigger Status Resources shown in the example above to be updated
to:</t>
<figure>
<artwork><![CDATA[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: Sun, 31 Aug 2014 09:54:30 GMT
Server: example-server/0.1
Etag: "-1842390246836476263"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:30 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/1"
]
}]]></artwork>
</figure>
</section>
<section title="Error Reporting">
<t>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:</t>
<figure>
<artwork><![CDATA[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: Sun, 31 Aug 2014 09:54:38 GMT
Server: example-server/0.1
Etag: "-3893590191073700822"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:38 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1409478810,
"errors": [
{
"content.urls": [
"http://newsite.example.com/index.html"
],
"description":
"No HostIndex entry found for newsite.example.com",
"error": "emeta"
}
],
"etime": 1409478818,
"mtime": 1409478814,
"status": "active",
"trigger": {
"content.urls": [
"http://newsite.example.com/index.html"
],
"type": "preposition"
}
}]]></artwork>
</figure>
</section>
</section>
</section>
<section title="IANA Considerations">
<section anchor="media-types"
title="CDNI Payload Type Parameter Registrations">
<t>The IANA is requested to register the following new Payload Types
in the CDNI Payload Type Parameter registry defined by <xref
target="I-D.ietf-cdni-media-type"/>, for use with the
'application/cdni' MIME media type.</t>
<t>RFC Editor Note: Please replace references to [RFCthis] below with
this document's RFC number before publication.</t>
<texttable>
<ttcol>Payload Type</ttcol>
<ttcol>Specification</ttcol>
<c>ci-trigger-command</c>
<c>[RFCthis]</c>
<c>ci-trigger-status</c>
<c>[RFCthis]</c>
<c>ci-trigger-collection</c>
<c>[RFCthis]</c>
</texttable>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>The CI/T interface provides a mechanism to allow a uCDN to generate
requests into the dCDN and to inspect its own CI/T requests and their
current state. The CI/T interface does not allow access to or
modification of the uCDN or dCDN metadata relating to content delivery,
or to the content itself. It can only control the presence of that
metadata in the dCDN, and the processing work and network utilisation
involved in ensuring that presence.</t>
<t>By examining pre-positioning requests to a dCDN, and correctly
interpreting content and metadata URLs, an attacker could learn the uCDN
or content owner's predictions for future content popularity. By
examining invalidate or purge requests, an attacker could learn about
changes in the content owner's catalogue.</t>
<t>By injecting CI/T commands an attacker, or a misbehaving uCDN, would
generate work in the dCDN and uCDN as they process those requests. And
so would a man in the middle attacker modifying valid CI/T commands
generated by the uCDN. In both cases, that would decrease the dCDN
caching efficiency by causing it to unnecessarily acquire or re-acquire
content metadata and/or content.</t>
<t>A dCDN implementation of CI/T MUST restrict the actions of a uCDN to
the data corresponding to that uCDN. Failure to do so would allow uCDNs
to detrimentally affect each other's efficiency by generating
unnecessary acquisition or re-acquisition load.</t>
<section anchor="tls"
title="Authentication, Authorization, Confidentiality, Integrity Protection">
<t>A CI/T implementation MUST support TLS transport for HTTP (https)
as per <xref target="RFC2818"/> and <xref target="RFC7230"/>.</t>
<t>The use of TLS for transport of the CI/T interface allows:<list
style="symbols">
<t>The dCDN and the uCDN to authenticate each other.</t>
</list></t>
<t>And, once they have mutually authenticated each other, it
allows:<list style="symbols">
<t>The dCDN and the uCDN to authorize each other (to ensure they
are receiving CI/T Commands from, or reporting status to, an
authorized CDN).</t>
<t>CDNI commands and responses to be transmitted with
confidentiality.</t>
<t>Protection of the integrity of CDNI commands and responses.</t>
</list></t>
<t>In an environment where any such protection is required, mutually
authenticated encrypted transport MUST be used to ensure
confidentiality of the CI/T information. To that end, TLS MUST be used
by CI/T, including authentication of the remote end.</t>
<t>When TLS is used, the general TLS usage guidance in <xref
target="RFC7525"/> MUST be followed.</t>
<t>HTTP requests that attempt to access or operate on CI/T data
belonging to another CDN MUST be rejected using, for example, HTTP
"403 Forbidden" or "404 Not Found". This is intended to prevent
unauthorised users from generating unnecessary load in dCDN or uCDN
due to revalidation, reacquisition, or unnecessary acquisition.</t>
<t>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, the dCDN MUST allow each uCDN from which the
content could have been acquired to act upon that content using CI/T
Commands.</t>
</section>
<section title="Denial of Service">
<t>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).</t>
<t>Depending on the implementation, triggered activity may consume
significant processing and bandwidth in the dCDN. A malicious or
faulty uCDN could use this to generate unnecessary load in the dCDN.
The dCDN should consider mechanisms to avoid overload, for example by
rate-limiting acceptance or processing of CI/T Commands, or batching
up its processing.</t>
</section>
<section title="Privacy">
<t>The CI/T protocol does not carry any information about individual
End Users of a CDN, there are no privacy concerns for End Users.</t>
<t>The CI/T protocol does carry information which could be considered
commercially sensitive by CDN operators and content owners. The use of
mutually authenticated TLS to establish a secure session for the
transport of CI/T data, as discussed in <xref target="tls"/>, provides
confidentiality while the CI/T data is in transit, and prevents
parties other party than the authorised dCDN from gaining access to
that data. The dCDN MUST ensure that it only exposes CI/T data related
to a uCDN to clients it has authenticated as belonging to that
uCDN.</t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors thank Kevin Ma for his input, and Carsten Bormann for his
review and formalization of the JSON data.</t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc2119;
&rfc7159;
&rfc7230;
&rfc7231;
&rfc7232;
&rfc7525;
</references>
<references title="Informative References">
&rfc2818;
&rfc6707;
&rfc7336;
&rfc7337;
&I-D.draft-ietf-cdni-media-type;
&I-D.draft-ietf-cdni-metadata;
&I-D.draft-ietf-cdni-redirection;
&I-D.draft-greevenbosch-appsawg-cbor-cddl;
</references>
</back>
</rfc>
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