Internet DRAFT - draft-ietf-cdni-control-triggers
draft-ietf-cdni-control-triggers
Network Working Group R. Murray
Internet-Draft B. Niven-Jenkins
Intended status: Standards Track Nokia
Expires: November 20, 2016 May 19, 2016
CDNI Control Interface / Triggers
draft-ietf-cdni-control-triggers-15
Abstract
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.
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 November 20, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Model for CDNI Triggers . . . . . . . . . . . . . . . . . . . 4
2.1. Timing of Triggered Activity . . . . . . . . . . . . . . 6
2.2. Scope of Triggered Activity . . . . . . . . . . . . . . . 6
2.2.1. Multiple Interconnected CDNs . . . . . . . . . . . . 7
2.3. Trigger Results . . . . . . . . . . . . . . . . . . . . . 8
3. Collections of Trigger Status Resources . . . . . . . . . . . 8
4. CDNI Trigger Interface . . . . . . . . . . . . . . . . . . . 9
4.1. Creating Triggers . . . . . . . . . . . . . . . . . . . . 10
4.2. Checking Status . . . . . . . . . . . . . . . . . . . . . 11
4.2.1. Polling Trigger Status Resource collections . . . . . 12
4.2.2. Polling Trigger Status Resources . . . . . . . . . . 12
4.3. Cancelling Triggers . . . . . . . . . . . . . . . . . . . 12
4.4. Deleting Triggers . . . . . . . . . . . . . . . . . . . . 13
4.5. Expiry of Trigger Status Resources . . . . . . . . . . . 14
4.6. Loop Detection and Prevention . . . . . . . . . . . . . . 14
4.7. Error Handling . . . . . . . . . . . . . . . . . . . . . 15
4.8. Content URLs . . . . . . . . . . . . . . . . . . . . . . 16
5. CI/T Object Properties and Encoding . . . . . . . . . . . . . 16
5.1. CI/T Objects . . . . . . . . . . . . . . . . . . . . . . 16
5.1.1. CI/T Commands . . . . . . . . . . . . . . . . . . . . 16
5.1.2. Trigger Status Resource . . . . . . . . . . . . . . . 17
5.1.3. Trigger Collection . . . . . . . . . . . . . . . . . 19
5.2. Properties of CI/T Objects . . . . . . . . . . . . . . . 20
5.2.1. Trigger Specification . . . . . . . . . . . . . . . . 20
5.2.2. Trigger Type . . . . . . . . . . . . . . . . . . . . 21
5.2.3. Trigger Status . . . . . . . . . . . . . . . . . . . 22
5.2.4. PatternMatch . . . . . . . . . . . . . . . . . . . . 23
5.2.5. Absolute Time . . . . . . . . . . . . . . . . . . . . 24
5.2.6. Error Description . . . . . . . . . . . . . . . . . . 24
5.2.7. Error Code . . . . . . . . . . . . . . . . . . . . . 25
6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6.1. Creating Triggers . . . . . . . . . . . . . . . . . . . . 26
6.1.1. Preposition . . . . . . . . . . . . . . . . . . . . . 26
6.1.2. Invalidate . . . . . . . . . . . . . . . . . . . . . 28
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6.2. Examining Trigger Status . . . . . . . . . . . . . . . . 29
6.2.1. Collection of All Triggers . . . . . . . . . . . . . 29
6.2.2. Filtered Collections of Trigger Status Resources . . 30
6.2.3. Individual Trigger Status Resources . . . . . . . . . 32
6.2.4. Polling for Change . . . . . . . . . . . . . . . . . 34
6.2.5. Deleting Trigger Status Resources . . . . . . . . . . 37
6.2.6. Error Reporting . . . . . . . . . . . . . . . . . . . 38
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
7.1. CDNI Payload Type Parameter Registrations . . . . . . . . 40
7.2. CDNI CI/T Trigger Types Registry . . . . . . . . . . . . 40
7.3. CDNI CI/T Error Codes Registry . . . . . . . . . . . . . 40
8. Security Considerations . . . . . . . . . . . . . . . . . . . 41
8.1. Authentication, Authorization, Confidentiality, Integrity
Protection . . . . . . . . . . . . . . . . . . . . . . . 41
8.2. Denial of Service . . . . . . . . . . . . . . . . . . . . 42
8.3. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 43
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 43
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
10.1. Normative References . . . . . . . . . . . . . . . . . . 43
10.2. Informative References . . . . . . . . . . . . . . . . . 44
Appendix A. Formalization of the JSON Data . . . . . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46
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).
[RFC7336] 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. Section 4 of
[RFC7337] identifies the requirements specific to the CI interface,
requirements applicable to the CI/T interface are CI-1 to CI-6.
o Section 2 outlines the model for the CI/T Interface at a high
level.
o Section 3 describes collections of Trigger Status Resources.
o Section 4 defines the web service provided by the dCDN.
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o Section 5 lists properties of CI/T Commands and Status Resources.
o Section 6 contains example messages.
1.1. Terminology
This document reuses the terminology defined in [RFC6707] and uses
"uCDN" and "dCDN" as shorthand for "Upstream CDN" and "Downstream
CDN", respectively.
2. Model for CDNI Triggers
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.
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:
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
CI/T commands to be issued, and triggered activity to be tracked.
The CI/T interface builds on top of HTTP/1.1 [RFC7230]. References
to URL in this document relate to http/https URIs, as defined in
[RFC7230] section 2.7.
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.
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.
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
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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.
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 Section 3 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.
Figure 1 is an example showing the basic message flow used by the
uCDN to trigger activity in the dCDN, and for the uCDN to discover
the status of that activity. Only successful triggering is shown.
Examples of the messages are given in Section 6.
uCDN dCDN
| (1) POST https://dcdn.example.com/triggers/uCDN |
[ ] --------------------------------------------------> [ ]--+
| [ ] | (2)
| (3) HTTP 201 Response [ ]<-+
[ ] <-------------------------------------------------- [ ]
| Loc: https://dcdn.example.com/triggers/uCDN/123 |
| |
. . .
. . .
. . .
| |
| (4) GET https://dcdn.example.com/triggers/uCDN/123 |
[ ] --------------------------------------------------> [ ]
| [ ]
| (5) HTTP 200 Trigger Status Resource [ ]
[ ] <-------------------------------------------------- [ ]
| |
| |
Figure 1: Basic CDNI Message Flow for Triggers
The steps in Figure 1 are:
1. The uCDN triggers action in the dCDN by posting a CI/T Command to
a collection of Trigger Status Resources,
"https://dcdn.example.com/triggers/uCDN". The URL of this was
given to the uCDN when the CI/T interface was established.
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2. The dCDN authenticates the request, validates the CI/T Command
and, if it accepts the request, creates a new Trigger Status
Resource.
3. The dCDN responds to the uCDN with an HTTP 201 response status,
and the location of the Trigger Status Resource.
4. The uCDN can poll, possibly repeatedly, the Trigger Status
Resource in the dCDN.
5. The dCDN responds with the Trigger Status Resource, describing
progress or results of the CI/T Trigger Command.
The remainder of this document describes the messages, Trigger Status
Resources, and collections of Trigger Status Resources in more
detail.
2.1. Timing of Triggered Activity
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.
CI/T invalidate and purge commands MUST be applied to all data
acquired before the command was accepted by the dCDN. The dCDN
SHOULD NOT apply CI/T invalidate and purge commands to data acquired
after the CI/T Command was accepted, but this may not always be
achievable so the uCDN cannot count on that.
If the uCDN wishes to invalidate or purge content 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).
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.
2.2. Scope of Triggered Activity
Each CI/T Command can operate on multiple metadata and content URLs.
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.
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2.2.1. Multiple Interconnected CDNs
In a network of interconnected CDNs a single uCDN will originate a
given item of metadata and associated content, it may distribute that
metadata and content to more than one dCDN, which may in-turn
distribute that metadata and content to further-downstream CDNs.
An intermediate CDN is a dCDN that passes on CDNI metadata and
content to further-downstream dCDNs.
A diamond configuration is one where a dCDN can acquire metadata and
content originated in one uCDN from that uCDN itself and an
intermediate CDN, or via more than one intermediate CDN.
CI/T commands originating in the single source uCDN affect metadata
and content in all dCDNs but, in a diamond configuration, it may not
be possible for the dCDN to determine which uCDN it acquired content
from. In this case a dCDN MUST allow each uCDN from which it may
have acquired the content to act upon that content using CI/T
Commands.
In all other cases, a dCDN MUST reject CI/T Commands from a uCDN that
act on another uCDN's data using, for example, HTTP "403 Forbidden".
Security considerations are discussed further in Section 8.
The diamond configuration may lead to inefficient interactions, but
the interactions are otherwise harmless. For example:
o When the uCDN issues an invalidate CI/T command, a dCDN will
receive that command from multiple directly connected uCDNs. The
dCDN may schedule multiple those commands separately, and the last
may affect content already revalidated following execution of the
invalidate command scheduled first.
o If one of a dCDN's directly-connected uCDNs loses its rights to
distribute content, it may issue a CI/T purge command. That purge
may affect content the dCDN could retain because it's distributed
by another directly-connected uCDN. But, that content can be re-
acquired by the dCDN from the remaining uCDN.
o When the uCDN originating an item of content issues a CI/T purge
followed by a preposition - two directly connected uCDNs will pass
those commands to a dCDN. That dCDN implementation need not merge
those operations, or notice the repetition. In which case the
purge issued by one uCDN will complete before the other. The
first uCDN to finish its purge may then forward the preposition
trigger, and content pre-positioned as a result might be affected
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by the still-running purge issued by the other uCDN. However, the
dCDN will re-acquire that content as needed, or when it's asked to
pre-position the content by the second uCDN. A dCDN
implementation could avoid this interaction by knowing which uCDN
it acquired the content from, or it could minimize the
consequences by recording the time at which the invalidate/purge
command was received and not applying it to content acquired after
that time.
2.3. Trigger Results
Possible states for a Trigger Status Resource are defined in section
Section 5.2.3.
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 Section 4.7.
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.
3. Collections of Trigger Status Resources
As described in Section 2, Trigger Status Resources exist in the dCDN
to report the status of activity triggered by each uCDN.
A collection of Trigger Status Resources is a resource that contains
a reference to each Trigger Status Resource in that collection.
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
Section 4.4). Trigger Status Resources belonging to a uCDN MUST NOT
be visible to any other CDN. The dCDN could, for example, achieve
this by offering different collection URLs to each uCDN, and by
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filtering the response based on the uCDN with which the HTTP client
is associated.
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.
In order to allow the uCDN to check the status of multiple jobs in a
single request, the dCDN MAY also maintain collections representing
filtered views of the collection of all Trigger Status Resources.
These filtered collections are optional-to-implement but, if
implemented, the dCDN MUST include links to them in the collection of
all Trigger Status Resources. The filtered collections are:
o Pending - Trigger Status Resources for CI/T Trigger Commands that
have been accepted, but not yet acted upon.
o Active - Trigger Status Resources for CI/T Trigger Commands that
are currently being processed in the dCDN.
o 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.
o Failed - Trigger Status Resources representing CI/T Commands that
failed or were cancelled by the uCDN.
4. CDNI Trigger Interface
This section describes an interface to enable an upstream CDN to
trigger activity in a downstream CDN.
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.
All dCDNs 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]. It MUST be supported by the uCDN and by the dCDN.
The URL of the dCDN's collection of all Trigger Status Resources
needs to be either discovered by, or configured in, the uCDN. The
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mechanism for discovery of that URL is outside the scope of this
document.
CI/T Commands are POSTed to the dCDN's collection of all Trigger
Status Resources. If a CI/T Trigger Command is accepted by the dCDN,
the dCDN creates a new Trigger Status Resource and returns its URI to
the uCDN in an HTTP 201 response. The triggered activity can then be
monitored by the uCDN using that resource and the collections
described in Section 3.
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.
4.1. Creating Triggers
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
Section 5.1.1.
The dCDN validates the CI/T Command. If the command is malformed or
the uCDN does not have sufficient access rights, the dCDN MUST either
respond with an appropriate 4xx HTTP error code and not create a
Trigger Status Resource, or create a 'failed' Trigger Status Resource
containing an appropriate error description.
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 particularly important in cases where the CI/T Trigger
Command has completed immediately.
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.
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The dCDN SHOULD track and report on progress of CI/T Trigger Commands
using a Trigger Status Resource, Section 5.1.2. 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.
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".
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 pre-position 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.
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".
4.2. Checking Status
The uCDN has two ways to check progress of CI/T Commands it has
issued to the dCDN, described in sections Section 4.2.1 and
Section 4.2.2.
To allow the uCDN 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, the dCDN SHOULD include
Entity Tags for the uCDN to use as cache validators, as defined in
[RFC7232].
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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.
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 CI/T Trigger Commands in
a single request. If the dCDN moves a Trigger Status Resource from
the Active to the Completed collection, the uCDN can fetch the result
of that activity.
When polling in this way, the uCDN SHOULD use HTTP Entity Tags to
monitor for change, rather than repeatedly fetching the whole
collection. An example of this is given in section Section 6.2.4.
4.2.2. Polling Trigger Status Resources
The uCDN has a URI provided by the dCDN for each Trigger Status
Resource it has created, it may fetch that Trigger Status Resource at
any time.
This can be used to retrieve progress information, and to fetch the
result of the CI/T Command.
When polling in this way, the uCDN SHOULD use HTTP Entity Tags to
monitor for change, rather than repeatedly fetching the Trigger
Status Resource.
4.3. Cancelling Triggers
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.
The dCDN is required to accept and respond to the CI/T Cancel
Command, but the actual cancellation of a CI/T Trigger Command is
optional-to-implement.
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.
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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.
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.
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.
Cancellation of a "complete" or "failed" Trigger Status Resource
requires no processing in the dCDN. Its status MUST NOT be changed
to "cancelled".
4.4. Deleting Triggers
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.
Once deleted, the references to a Trigger Status Resource MUST be
removed from all Trigger Status Resource collections. Subsequent
requests to GET the deleted Trigger Status Resource SHOULD be
rejected by the dCDN with an HTTP error.
If a "pending" Trigger Status Resource is deleted, the dCDN SHOULD
NOT start processing of that activity. Deleting a "pending" Trigger
Status Resource does not however guarantee that it has not started
because the uCDN cannot control the timing of that activity.
Processing may, for example, start after the DELETE is sent by the
uCDN but before that request is processed by the dCDN.
If an "active" or "processed" Trigger Status Resource is deleted, the
dCDN SHOULD stop processing the CI/T Command. However, as with
deletion of a "pending" Trigger Status Resource, the dCDN does not
guarantee this.
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Deletion of a "complete" or "failed" Trigger Status Resource requires
no processing in the dCDN other than deletion of the Trigger Status
Resource.
4.5. Expiry of Trigger Status Resources
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.
If the dCDN does remove Trigger Status Resources automatically, it
MUST report the length of time after which it will do so, using a
property of the collection of all Trigger Status Resources. It is
RECOMMENDED that Trigger Status Resources are not automatically
deleted by the dCDN for at least 24 hours after they become
"complete", "processed", "failed" or "cancelled".
To ensure 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.
4.6. Loop Detection and Prevention
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.
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.
The CDN Provider Id consists of the two characters "AS" followed by
the CDN Provider's Autonomous System number [RFC1930], 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".
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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.
If the RI interface described in [I-D.ietf-cdni-redirection] is
implemented by the dCDN, the CI/T and RI interfaces SHOULD use the
same CDN Provider Id.
4.7. Error Handling
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.
If any part of the CI/T Trigger Command fails, the trigger SHOULD be
reported as "failed" once its activity is complete or if no further
errors will be reported. The "errors" property in the Trigger Status
Resource will be used to enumerate which actions failed and the
reasons for failure, and can be present while the Trigger Status
Resource is still "pending" or "active", if the CI/T Trigger Command
is still running for some URLs or Patterns in the Trigger
Specification.
Once a request has been accepted, processing errors are reported in
the Trigger Status Resource using a list of Error Descriptions. Each
Error Description is used to report errors against one or more of the
URLs or Patterns in the Trigger Specification.
If a surrogate affected by a CI/T Trigger Command is offline in the
dCDN, or the dCDN is unable to pass a CI/T Command on to any of its
cascaded dCDNs:
o If the CI/T Command is abandoned by the dCDN, the dCDN SHOULD
report an error.
o 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.
o 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.
o 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.
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4.8. Content URLs
If content URLs are transformed by an intermediate CDN in a cascade,
that intermediate CDN MUST similarly transform URLs in CI/T Commands
it passes to its dCDN.
When processing Trigger Specifications, CDNs MUST ignore the URL
scheme (http or https) in comparing URLs. For example, for a CI/T
invalidate or purge command, content MUST be invalidated or purged
regardless of the protocol clients use to request it.
5. CI/T Object Properties and Encoding
The CI/T Commands, Trigger Status Resources and Trigger Collections
and their properties are encoded using JSON, as defined in sections
Section 5.1.1, Section 5.2.1, and Section 5.1.2. They MUST use the
MIME Media Type 'application/cdni', with parameter 'ptype' values as
defined below and in Section 7.1.
Names in JSON are case sensitive. The names and literal values
specified in the present document MUST always use lower-case.
JSON types, including 'object', 'array', 'number' and 'string' are
defined in [RFC7159].
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.
5.1. CI/T Objects
The top-level objects defined by the CI/T interface are described in
this section.
The encoding of values used by these objects is described in
Section 5.2.
5.1.1. CI/T Commands
CI/T Commands MUST use a MIME Media Type of 'application/cdni;
ptype=ci-trigger-command'.
A CI/T Command is encoded as a JSON object containing the following
name/value pairs.
Name: trigger
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Description: A specification of the trigger type, and a set of
data to act upon.
Value: A Trigger Specification, as defined in Section 5.2.1.
Mandatory: No, but exactly one of "trigger" or "cancel" MUST be
present in a CI/T Command.
Name: cancel
Description: The URLs of Trigger Status Resources for CI/T
Trigger Commands that the uCDN wants to cancel.
Value: A non-empty JSON array of URLs represented as JSON
strings.
Mandatory: No, but exactly one of "trigger" or "cancel" MUST be
present in a CI/T Command.
Name: cdn-path
Description: The CDN Provider Identifiers of CDNs that have
already issued the CI/T Command to their dCDNs.
Value: A non-empty JSON array of JSON strings, where each
string is a CDN Provider Identifier as defined in Section 4.6.
Mandatory: Yes.
5.1.2. Trigger Status Resource
Trigger Status Resources MUST use a MIME Media Type of 'application/
cdni; ptype=ci-trigger-status'.
A Trigger Status Resource is encoded as a JSON object containing the
following name/value pairs.
Name: trigger
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.
Value: A Trigger Specification, as defined in Section 5.2.1.
Mandatory: Yes
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Name: ctime
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.
Value: Absolute Time, as defined in Section 5.2.5.
Mandatory: Yes
Name: mtime
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.
Value: Absolute Time, as defined in Section 5.2.5.
Mandatory: Yes
Name: 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.
Value: Absolute Time, as defined in Section 5.2.5.
Mandatory: No
Name: status
Description: Current status of the triggered activity.
Value: Trigger Status, as defined in Section 5.2.3.
Mandatory: Yes
Name: errors
Description: Descriptions of errors that have occurred while
processing a Trigger Command.
Value: An array of Error Description, as defined in
Section 5.2.6. An empty array is allowed, and equivalent to
omitting "errors" from the object.
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Mandatory: No.
5.1.3. Trigger Collection
Trigger Collections MUST use a MIME Media Type of 'application/cdni;
ptype=ci-trigger-collection'.
A Trigger Collection is encoded as a JSON object containing the
following name/value pairs.
Name: triggers
Description: Links to Trigger Status Resources in the
collection.
Value: A JSON array of zero or more URLs, represented as JSON
strings.
Mandatory: Yes
Name: staleresourcetime
Description: The length of time for which the dCDN guarantees
to keep a completed Trigger Status Resource. After this time,
the dCDN SHOULD delete the Trigger Status Resource and all
references to it from collections.
Value: A JSON number, which must be a positive integer,
representing time in seconds.
Mandatory: Yes, in the collection of all Trigger Status
Resources if the dCDN deletes stale entries. If the property
is present in the filtered collections, it MUST have the same
value as in the collection of all Trigger Status Resources.
Names: coll-all, coll-pending, coll-active, coll-complete, coll-
failed
Description: Link to a Trigger Collection.
Value: A URL represented as a JSON string.
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.
Name: cdn-id
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Description: The CDN Provider Identifier of the dCDN.
Value: A JSON string, the dCDN's CDN Provider Identifier, as
defined in Section 4.6.
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).
5.2. Properties of CI/T Objects
This section defines the values that can appear in the top level
objects described in Section 5.1, and their encodings.
5.2.1. Trigger Specification
A Trigger Collection is encoded as a JSON object containing the
following name/value pairs.
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.
Name: type
Description: This property defines the type of the CI/T Trigger
Command.
Value: Trigger Type, as defined in Section 5.2.2.
Mandatory: Yes
Name: metadata.urls
Description: The uCDN URLs of the metadata the CI/T Trigger
Command applies to.
Value: A JSON array of URLs represented as JSON strings.
Mandatory: No, but at least one of 'metadata.*' or 'content.*'
MUST be present and non-empty.
Name: content.urls
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Description: URLs of content the CI/T Trigger Command applies
to, see Section 4.8.
Value: A JSON array of URLs represented as JSON strings.
Mandatory: No, but at least one of 'metadata.*' or 'content.*'
MUST be present and non-empty.
Name: content.ccid
Description: The Content Collection Identifier of content the
trigger applies to. The 'ccid' is a grouping of content, as
defined by [I-D.ietf-cdni-metadata].
Value: A JSON array of strings, where each string is a Content
Collection Identifier.
Mandatory: No, but at least one of 'metadata.*' or 'content.*'
MUST be present and non-empty.
Name: metadata.patterns
Description: The metadata the trigger applies to.
Value: A JSON array of Pattern Match, as defined in
Section 5.2.4.
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.
Name: content.patterns
Description: The content data the trigger applies to.
Value: A JSON array of Pattern Match, as defined in
Section 5.2.4.
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.
5.2.2. Trigger Type
Trigger Type is used in a Trigger Specification to describe trigger
action.
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All trigger types MUST be registered in the IANA CI/T Trigger Types
registry (see Section 7.2).
A dCDN receiving a request containing a trigger type it does not
recognise or does not support MUST reject the request by creating a
Trigger Status Resource with status to "failed" and the "errors"
array containing an Error Description with error "eunsupported".
The following trigger types are defined by this document:
+-------------+-----------------------------------------------------+
| JSON String | Description |
+-------------+-----------------------------------------------------+
| preposition | A request for the dCDN to acquire metadata or |
| | content. |
| invalidate | A request for the dCDN to invalidate metadata or |
| | content. After servicing this request the dCDN will |
| | not use the specified data without first re- |
| | validating it using, for example, an "If-None- |
| | Match" HTTP request. The dCDN need not erase the |
| | associated data. |
| purge | A request for the dCDN to erase metadata or |
| | content. After servicing the request, the specified |
| | data MUST NOT be held on the dCDN (the dCDN should |
| | re-acquire the metadata or content from uCDN if it |
| | needs it). |
+-------------+-----------------------------------------------------+
5.2.3. Trigger Status
This describes the current status of a Trigger. It MUST be one of
the JSON strings in the following table:
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+------------+------------------------------------------------------+
| JSON | Description |
| String | |
+------------+------------------------------------------------------+
| pending | The CI/T Trigger Command has not yet been acted |
| | upon. |
| active | The CI/T Trigger Command is currently being acted |
| | upon. |
| complete | The CI/T Trigger Command completed successfully. |
| processed | The CI/T Trigger Command has been accepted and no |
| | further status update will be made (can be used in |
| | cases where completion cannot be confirmed). |
| failed | The CI/T Trigger Command could not be completed. |
| cancelling | Processing of the CI/T Trigger Command is still in |
| | progress, but the CI/T Trigger Command has been |
| | cancelled by the uCDN. |
| cancelled | The CI/T Trigger Command was cancelled by the uCDN. |
+------------+------------------------------------------------------+
5.2.4. PatternMatch
A Pattern Match consists of a string pattern to match against a URI,
and flags describing the type of match.
It is encoded as a JSON object with the following name/value pairs:
Name: pattern
Description: A pattern for URI matching.
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 "\?".
Mandatory: Yes.
Name: case-sensitive
Description: Flag indicating whether or not case-sensitive
matching should be used.
Value: One of the JSON values 'true' (the matching is case-
sensitive) or 'false' (the matching is case-insensitive).
Mandatory: No, default is case-insensitive match.
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Name: match-query-string
Description: Flag indicating whether or not the query part of
the URI should be included in the pattern match.
Value: One of the JSON values 'true' (the full URI including
the query part should be compared against the given pattern),
or 'false' (the query part of the URI should be dropped before
comparison with the given pattern).
Mandatory: No, default is 'false', the query part of the URI
should be dropped before comparison with the given pattern.
Example of case-sensitive prefix match against
"https://www.example.com/trailers/":
{
"pattern": "https://www.example.com/trailers/*",
"case-sensitive": true
}
5.2.5. Absolute Time
A JSON number, seconds since the UNIX epoch, 00:00:00 UTC on 1
January 1970.
5.2.6. Error Description
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:
Name: error
Value: Error Code, as defined in Section 5.2.7.
Mandatory: Yes.
Names: metadata.urls, content.urls, metadata.patterns,
content.patterns
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 "https://content.example.com/a"
and "https://content.example.com/b", the dCDN must not
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generalise its error report to Pattern
"https://content.example.com/*".)
Value: A JSON array of JSON strings, where each string is
copied from a 'content.*' or 'metadata.*' value in the
corresponding Trigger Specification.
Mandatory: At least one of these name/value pairs is mandatory
in each Error Description object.
Name: description
Description: A human-readable description of the error.
Value: A JSON string, the human-readable description.
Mandatory: No.
5.2.7. Error Code
This type is used by the dCDN to report failures in trigger
processing. All error codes MUST be registered in the IANA CI/T
Error Codes registry (see Section 7.3). Unknown error codes MUST be
treated as fatal errors, and the request MUST NOT be automatically
retried without modification.
The following error codes are defined by this document, and MUST be
supported by an implementation of the CI/T interface.
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+--------------+----------------------------------------------------+
| Error Code | Description |
+--------------+----------------------------------------------------+
| emeta | The dCDN was unable to acquire metadata required |
| | to fulfil the request. |
| econtent | The dCDN was unable to acquire content (CT/T |
| | preposition commands only). |
| eperm | The uCDN does not have permission to issue the |
| | CI/T Command (for example, the data is owned by |
| | another CDN). |
| ereject | 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). |
| ecdn | An internal error in the dCDN or one of its |
| | downstream CDNs. |
| ecancelled | The uCDN cancelled the request. |
| eunsupported | The Trigger Specification contained a "type" that |
| | is not supported by the dCDN. No action was taken |
| | bythe dCDN other than to create a Trigger Status |
| | Resource in state "failed". |
+--------------+----------------------------------------------------+
6. Examples
The following sections provide examples of different CI/T objects
encoded as JSON.
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.
In examples in this section, the URL 'https://dcdn.example.com/
triggers' is used as the location of the collection of all Trigger
Status Resources, and the CDN Provider Id of uCDN is "AS64496:1".
6.1. Creating Triggers
Examples of the uCDN triggering activity in the dCDN:
6.1.1. Preposition
An example of a CI/T preposition command, a POST to the collection of
all Trigger Status Resources.
Note that "metadata.patterns" and "content.patterns" are not allowed
in a preposition Trigger Specification.
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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: 352
{
"trigger" : {
"type": "preposition",
"metadata.urls" : [ "https://metadata.example.com/a/b/c" ],
"content.urls" : [
"https://www.example.com/a/b/c/1",
"https://www.example.com/a/b/c/2",
"https://www.example.com/a/b/c/3",
"https://www.example.com/a/b/c/4"
]
},
"cdn-path" : [ "AS64496:1" ]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Wed, 04 May 2016 08:48:10 GMT
Content-Length: 467
Content-Type: application/cdni; ptype=ci-trigger-status
Location: https://dcdn.example.com/triggers/0
Server: example-server/0.1
{
"ctime": 1462351690,
"etime": 1462351698,
"mtime": 1462351690,
"status": "pending",
"trigger": {
"content.urls": [
"https://www.example.com/a/b/c/1",
"https://www.example.com/a/b/c/2",
"https://www.example.com/a/b/c/3",
"https://www.example.com/a/b/c/4"
],
"metadata.urls": [
"https://metadata.example.com/a/b/c"
],
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"type": "preposition"
}
}
6.1.2. Invalidate
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 "https://www.example.com/a/index.html",
as well as any metadata and content whose URLs are prefixed by
"https://metadata.example.com/a/b/" using case-insensitive matching,
and "https://www.example.com/a/b/" respectively, using case-sensitive
matching.
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: 387
{
"trigger" : {
"type": "invalidate",
"metadata.patterns" : [
{ "pattern" : "https://metadata.example.com/a/b/*" }
],
"content.urls" : [ "https://www.example.com/a/index.html" ],
"content.patterns" : [
{ "pattern" : "https://www.example.com/a/b/*",
"case-sensitive" : true
}
]
},
"cdn-path" : [ "AS64496:1" ]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Wed, 04 May 2016 08:48:11 GMT
Content-Length: 545
Content-Type: application/cdni; ptype=ci-trigger-status
Location: https://dcdn.example.com/triggers/1
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Server: example-server/0.1
{
"ctime": 1462351691,
"etime": 1462351699,
"mtime": 1462351691,
"status": "pending",
"trigger": {
"content.patterns": [
{
"case-sensitive": true,
"pattern": "https://www.example.com/a/b/*"
}
],
"content.urls": [
"https://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern": "https://metadata.example.com/a/b/*"
}
],
"type": "invalidate"
}
}
6.2. Examining Trigger Status
Once Trigger Status Resources have been created, the uCDN can check
their status as shown in these examples.
6.2.1. Collection of All Triggers
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:
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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: 341
Expires: Wed, 04 May 2016 08:49:11 GMT
Server: example-server/0.1
ETag: "-936094426920308378"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:11 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": [
"https://dcdn.example.com/triggers/0",
"https://dcdn.example.com/triggers/1"
]
}
6.2.2. Filtered Collections of Trigger Status Resources
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:
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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: 152
Expires: Wed, 04 May 2016 08:49:11 GMT
Server: example-server/0.1
ETag: "4331492443626270781"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:11 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"https://dcdn.example.com/triggers/0",
"https://dcdn.example.com/triggers/1"
]
}
At this point, if no other Trigger Status Resources had been created,
the other filtered views 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: 54
Expires: Wed, 04 May 2016 08:49:11 GMT
Server: example-server/0.1
ETag: "7958041393922269003"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:11 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": []
}
6.2.3. Individual Trigger Status Resources
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:
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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: 467
Expires: Wed, 04 May 2016 08:49:10 GMT
Server: example-server/0.1
ETag: "6990548174277557683"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:10 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1462351690,
"etime": 1462351698,
"mtime": 1462351690,
"status": "pending",
"trigger": {
"content.urls": [
"https://www.example.com/a/b/c/1",
"https://www.example.com/a/b/c/2",
"https://www.example.com/a/b/c/3",
"https://www.example.com/a/b/c/4"
],
"metadata.urls": [
"https://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: 545
Expires: Wed, 04 May 2016 08:49:11 GMT
Server: example-server/0.1
ETag: "-554385204989405469"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:11 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1462351691,
"etime": 1462351699,
"mtime": 1462351691,
"status": "pending",
"trigger": {
"content.patterns": [
{
"case-sensitive": true,
"pattern": "https://www.example.com/a/b/*"
}
],
"content.urls": [
"https://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern": "https://metadata.example.com/a/b/*"
}
],
"type": "invalidate"
}
}
6.2.4. Polling for Change
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:
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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: "4331492443626270781"
RESPONSE:
HTTP/1.1 304 Not Modified
Content-Length: 0
Expires: Wed, 04 May 2016 08:49:11 GMT
Server: example-server/0.1
ETag: "4331492443626270781"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:11 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
REQUEST:
GET /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
If-None-Match: "6990548174277557683"
RESPONSE:
HTTP/1.1 304 Not Modified
Content-Length: 0
Expires: Wed, 04 May 2016 08:49:10 GMT
Server: example-server/0.1
ETag: "6990548174277557683"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:10 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
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:
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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: 54
Expires: Wed, 04 May 2016 08:49:15 GMT
Server: example-server/0.1
ETag: "1337503181677633762"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:15 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"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: 152
Expires: Wed, 04 May 2016 08:49:22 GMT
Server: example-server/0.1
ETag: "4481489539378529796"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:22 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"https://dcdn.example.com/triggers/0",
"https://dcdn.example.com/triggers/1"
]
}
6.2.5. Deleting Trigger Status Resources
The uCDN can delete completed and failed Trigger Status Resources to
reduce the size of the collections, as described in Section 4.4. For
example, to delete the "preposition" request from earlier examples:
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, 04 May 2016 08:48:22 GMT
Content-Length: 0
Content-Type: text/html; charset=UTF-8
Server: example-server/0.1
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This would, for example, cause the collection of completed Trigger
Status Resources 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: 105
Expires: Wed, 04 May 2016 08:49:22 GMT
Server: example-server/0.1
ETag: "-6938620031669085677"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:22 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"https://dcdn.example.com/triggers/1"
]
}
6.2.6. Error Reporting
In this example the uCDN has requested prepositioning of
"https://newsite.example.com/index.html", but the dCDN was unable to
locate metadata for that site:
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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: 486
Expires: Wed, 04 May 2016 08:49:26 GMT
Server: example-server/0.1
ETag: "5182824839919043757"
Cache-Control: max-age=60
Date: Wed, 04 May 2016 08:48:26 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1462351702,
"errors": [
{
"content.urls": [
"https://newsite.example.com/index.html"
],
"description": "newsite.example.com not in HostIndex",
"error": "emeta"
}
],
"etime": 1462351710,
"mtime": 1462351706,
"status": "active",
"trigger": {
"content.urls": [
"https://newsite.example.com/index.html"
],
"type": "preposition"
}
}
7. IANA Considerations
[RFC Editor Note: Please replace references to [RFCthis] in this
section with this document's RFC number before publication.]
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7.1. CDNI Payload Type Parameter Registrations
The IANA is requested to register the following new Payload Types in
the CDNI Payload Type Parameter registry defined by [RFC7736], for
use with the 'application/cdni' MIME media type.
+-----------------------+---------------+
| Payload Type | Specification |
+-----------------------+---------------+
| ci-trigger-command | [RFCthis] |
| ci-trigger-status | [RFCthis] |
| ci-trigger-collection | [RFCthis] |
+-----------------------+---------------+
7.2. CDNI CI/T Trigger Types Registry
The IANA is requested to create a new "CDNI CI/T Trigger Types"
subregistry under the "Content Delivery Networks Interconnection
(CDNI) Parameters" registry.
Additions to the CDNI CI/T Error Code Registry will be made via "RFC
Required" as defined in [RFC5226].
The initial contents of the CDNI CI/T Trigger Types Registry comprise
the names and descriptions listed in section Section 5.2.2 of this
document, with this document acting as the specification.
7.3. CDNI CI/T Error Codes Registry
The IANA is requested to create a new "CDNI CI/T Error Codes"
subregistry under the "Content Delivery Networks Interconnection
(CDNI) Parameters" registry.
Additions to the CDNI CI/T Error Codes Registry will be made via
"Specification Required" as defined in [RFC5226]. The Designated
Expert will verify that new error code registrations do not duplicate
existing error code definitions (in name or functionality), prevent
gratuitous additions to the namespace, and prevent any additions to
the namespace that would impair the interoperability of CDNI
implementations.
The initial contents of the CDNI CI/T Error Codes Registry comprise
the names and descriptions of the Error Codes listed in Section 5.2.7
of this document, with this document acting as the specification.
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8. Security Considerations
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.
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.
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.
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.
An origin that chooses to delegate its delivery to a CDN is trusting
that CDN to deliver content on its behalf, CDN-interconnection is an
extension of that trust to downstream CDNs. That trust relationship
is a commercial arrangement, outside the scope of the CDNi protocols.
So, while a malicious CDN could deliberately generate load on a dCDN
using the CI/T, the protocol does not otherwise attempt to address
malicious behaviour between interconnected CDNs.
8.1. Authentication, Authorization, Confidentiality, Integrity
Protection
A CI/T implementation MUST support TLS transport for HTTP (https) as
per [RFC2818] and [RFC7230].
TLS MUST be used by the server-side (dCDN) and the client-side (uCDN)
of the CI/T interface, including authentication of the remote end,
unless alternate methods are used for ensuring the security of the
information in the CI/T interface requests and responses (such as
setting up an IPsec tunnel between the two CDNs or using a physically
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secured internal network between two CDNs that are owned by the same
corporate entity).
The use of TLS for transport of the CI/T interface allows:
o The dCDN and the uCDN to authenticate each other using TLS client
auth and TLS server auth.
And, once they have mutually authenticated each other, it allows:
o 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).
o CDNI commands and responses to be transmitted with
confidentiality.
o Protection of the integrity of CDNI commands and responses.
When TLS is used, the general TLS usage guidance in [RFC7525] MUST be
followed.
The mechanisms for access control are dCDN-specific, not standardised
as part of this CI/T specification.
HTTP requests that attempt to access or operate on CI/T data
belonging to another CDN MUST be rejected using, for example, HTTP
"403 Forbidden" or "404 Not Found". This is intended to prevent
unauthorised users from generating unnecessary load in dCDN or uCDN
due to revalidation, reacquisition, or unnecessary acquisition.
When deploying a network of interconnected CDNs, the possible
inefficiencies related to the "diamond" configuration discussed in
Section 2.2.1 should be considered.
8.2. 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).
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
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rate-limiting acceptance or processing of CI/T Commands, or batching
up its processing.
8.3. Privacy
The CI/T protocol does not carry any information about individual End
Users of a CDN, there are no privacy concerns for End Users.
The CI/T protocol does carry information 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 Section 8.1, provides
confidentiality while the CI/T data is in transit, and prevents
parties other 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.
9. Acknowledgements
The authors thank Kevin Ma for his input, and Carsten Bormann for his
review and formalization of the JSON data.
10. References
10.1. Normative References
[I-D.ietf-cdni-metadata]
Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
"CDN Interconnection Metadata", draft-ietf-cdni-
metadata-16 (work in progress), April 2016.
[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
selection, and registration of an Autonomous System (AS)",
BCP 6, RFC 1930, DOI 10.17487/RFC1930, March 1996,
<http://www.rfc-editor.org/info/rfc1930>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
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[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, September 2012.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, March 2014.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230, June
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.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, May 2015.
10.2. Informative References
[I-D.greevenbosch-appsawg-cbor-cddl]
Vigano, C. and H. Birkholz, "CBOR data definition language
(CDDL): a notational convention to express CBOR data
structures", draft-greevenbosch-appsawg-cbor-cddl-08 (work
in progress), March 2016.
[I-D.ietf-cdni-redirection]
Niven-Jenkins, B. and R. Brandenburg, "Request Routing
Redirection interface for CDN Interconnection", draft-
ietf-cdni-redirection-18 (work in progress), April 2016.
[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg,
"Framework for Content Distribution Network
Interconnection (CDNI)", RFC 7336, August 2014.
[RFC7337] Leung, K. and Y. Lee, "Content Distribution Network
Interconnection (CDNI) Requirements", RFC 7337, August
2014.
[RFC7736] Ma, K., "Content Delivery Network Interconnection (CDNI)
Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
December 2015, <http://www.rfc-editor.org/info/rfc7736>.
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Appendix A. Formalization of the JSON Data
This appendix is non-normative.
The JSON data described in this document has been formalised using
CDDL [I-D.greevenbosch-appsawg-cbor-cddl] as follows:
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
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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
Authors' Addresses
Rob Murray
Nokia
3 Ely Road
Milton, Cambridge CB24 6DD
UK
Email: rob.murray@nokia.com
Ben Niven-Jenkins
Nokia
3 Ely Road
Milton, Cambridge CB24 6DD
UK
Email: ben.niven-jenkins@nokia.com
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