Internet DRAFT - draft-finkelman-cdni-triggers-sva-extensions
draft-finkelman-cdni-triggers-sva-extensions
Network Working Group O. Finkelman
Internet-Draft Qwilt
Intended status: Standards Track S. Mishra
Expires: April 25, 2019 Verizon
October 22, 2018
CDNI Control Triggers Interface Extensions
draft-finkelman-cdni-triggers-sva-extensions-01
Abstract
The Open Caching working group of the Streaming Video Alliance is
focused on the delegation of video delivery request from commercial
CDNs to a caching layer at the ISP. In that aspect, Open Caching is
a specific use case of CDNI, where the commercial CDN is the upstream
CDN (uCDN) and the ISP caching layer is the downstream CDN (dCDN).
The extensions specified in this document to the CDNI CI/T interface
are derived from requirements raised by Open Caching but are
applicable to CDNI use cases in general.
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 https://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 April 25, 2019.
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Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Interfaces Extensions Overview . . . . . . . . . . . . . . . 4
2.1. CDNI Control Interface / Triggers Extensions . . . . . . 4
2.1.1. CI/T Objects . . . . . . . . . . . . . . . . . . . . 4
2.1.2. Trigger Specification . . . . . . . . . . . . . . . . 4
2.1.3. Content Selection . . . . . . . . . . . . . . . . . . 4
2.1.4. Trigger Extensibility . . . . . . . . . . . . . . . . 5
2.1.5. Error Propagation . . . . . . . . . . . . . . . . . . 5
2.2. CDNI Footprint and Capabilities Interface Extensions . . 6
3. CI/T Version 2 . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. CI/T Objects V2 . . . . . . . . . . . . . . . . . . . . . 6
3.2. Properties of CI/T Version 2 objects . . . . . . . . . . 9
3.2.1. Trigger Specification Version 2 . . . . . . . . . . . 9
3.2.2. RegexMatch . . . . . . . . . . . . . . . . . . . . . 10
3.2.3. Playlist . . . . . . . . . . . . . . . . . . . . . . 12
3.2.4. MediaProtocol . . . . . . . . . . . . . . . . . . . . 13
3.2.5. CI/T Trigger Extensions . . . . . . . . . . . . . . . 13
3.2.5.1. Enforcement Options . . . . . . . . . . . . . . . 13
3.2.5.2. GenericExtensionObject . . . . . . . . . . . . . 16
3.2.6. Error Description Version 2 . . . . . . . . . . . . . 18
3.2.7. Error codes . . . . . . . . . . . . . . . . . . . . . 19
4. Trigger Extension Objects . . . . . . . . . . . . . . . . . . 19
4.1. LocationPolicy extension . . . . . . . . . . . . . . . . 19
4.2. TimePolicy Extension . . . . . . . . . . . . . . . . . . 21
5. Footprint and Capabilities . . . . . . . . . . . . . . . . . 23
5.1. CI/T Versions Capability Object . . . . . . . . . . . . . 23
5.1.1. CI/T Versions Capability Object Serialization . . . . 24
5.2. CI/T Playlist Protocol Capability Object . . . . . . . . 24
5.2.1. CI/T Playlist Protocol Capability Object
Serialization . . . . . . . . . . . . . . . . . . . . 24
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5.3. CI/T Trigger Extension Capability Object . . . . . . . . 25
5.3.1. CI/T Trigger Extension Capability Object
Serialization . . . . . . . . . . . . . . . . . . . . 25
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
6.1. CDNI Payload Types . . . . . . . . . . . . . . . . . . . 26
6.1.1. CDNI ci-trigger-command.v2 Payload Type . . . . . . . 26
6.1.2. CDNI ci-trigger-status.v2 Payload Type . . . . . . . 27
6.1.3. CDNI CI/T LocationPolicy Trigger Extension Type . . . 27
6.1.4. CDNI CI/T TimePolicy Trigger Extension Type . . . . . 27
6.1.5. CDNI FCI CI/T Versions Payload Type . . . . . . . . . 27
6.1.6. CDNI FCI CI/T Playlist Protocol Payload Type . . . . 27
6.1.7. CDNI FCI CI/T Extension Objects Payload Type . . . . 28
6.2. CDNI CI/T Trigger Error Codes types . . . . . . . . . . . 28
6.3. CDNI Media protocol types . . . . . . . . . . . . . . . . 28
7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 29
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1. Normative References . . . . . . . . . . . . . . . . . . 30
10.2. Informative References . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction
This document defines the objects and extensions required for
granular content management operations. For that purpose it extends
CDNI Control Interface/Triggers [RFC8007]. The basic operations are
the ones defined in the RFC (i.e. purge, invalidate, pre-position).
For consistency, this document follows the CDNI notation of uCDN (the
commercial CDN) and dCDN (the ISP caching layer). When using the
term CP in this document we refer to a video content provider.
The CDNI metadata interface is described in [RFC8006].
The CDNI footprint and capability interface is described in
[RFC8008].
The CDNI control interface / triggers is described in [RFC8007].
1.1. Terminology
This document reuses the terminology defined in [RFC6707], [RFC8006],
[RFC8007], and [RFC8008].
Additionally, the following terms are used throughout this document
and are defined as follows:
o HLS - HTTP Live Streaming
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o DASH - Dynamic Adaptive Streaming Over HTTP
o MSS - Microsoft Smooth Streaming
2. Interfaces Extensions Overview
This document defines extensions for the CDNI Control Interface /
Triggers [RFC8007] and defines FCI objects as per the CDNI Footprint
and Capabilities Interface [RFC8008].
2.1. CDNI Control Interface / Triggers Extensions
2.1.1. CI/T Objects
This document specifies version 2 of the CI/T objects in order to
support version 2 of the Trigger Specification as required below in
Section 2.1.2.
2.1.2. Trigger Specification
This document specifies version 2 of the Trigger Specification which
is an enhancement of the Trigger Specification that includes all
properties as defined in section 5.2.1 of [RFC8007] as well as the
additional properties required by the use cases listed below in
Section 2.1.3 and Section 2.1.4.
2.1.3. Content Selection
The trigger specification as defined in section 5.2.1 of [RFC8007]
provides means to select content objects by matching a full content
URL or patterns with wildcards. This document specifies two
additional selection options.
o Regular Expression - Using regex a uCDN can create more complex
rules to select the content objects for the cases of invalidation
and purge. For example, purging specific content within a
specific directory path.
o Content Playlist - Using video playlist files, a uCDN can trigger
an operation that will be applied to a collection of distinct
media files in a format that is natural for a streaming video
content provider. A playlist may have several formats,
specifically HTTP Live Streaming (HLS) *.m3u8 manifest [RFC8216],
Microsoft Smooth Streaming (MSS) *.ismc client manifest [MSS], and
Dynamic Adaptive Streaming over HTTP (DASH) *.mpd file [ISO/IEC
23009-1:2014] [MPEG-DASH].
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2.1.4. Trigger Extensibility
The CDNI Control Interface / Triggers [RFC8007] defines a set of
objects used by the trigger commands. In order to have better
control and finer granularity, we define a mechanism for generic
trigger extension object wrapper for managing individual CDNI trigger
extensions in an opaque manner, as well as an initial set of trigger
extension objects.
This document also registers CDNI Payload Types [RFC7736] under the
namespace CIT for the initial set of trigger extension types:
o CIT.LocationPolicy (for controlling the locations in which the
trigger is executed)
o CIT.TimePolicy (for scheduling a trigger to run in a specific time
window)
Example use cases
o Pre-position with cache location policy
o Purge content with cache location policy
o Pre-position at a specific time
o Purge by content acquisition time (e.g. purge all content acquired
in the past X hours)
2.1.5. Error Propagation
As triggers may be propagated over a chain of downstream CDNs and
since, in some cases, triggers may be redistributed from dCDN-A to
dCDN-B even if dCDN-A does not understand a specific extension, it is
essential for the uCDN that sets the trigger to be able to trace back
and error to the downstream where it occurred. This document
specifies version 2 of the Error Description which is an enhancement
of the Error Description as defined in section 5.2.6 of [RFC8007] and
that includes all the original properties as well as the additional
property "cdn" which is an identifier for the faulty CDN. When a
downstream dCDN-A propagates a trigger to another downstream dCDN-B,
it MUST also propagate back the errors received in the trigger status
resource from dCDN-B. This makes sure that the trigger originating
upstream CDN will receive an array of errors that occurred in all the
CDNs along the execution path, each error carrying its own CDN
identifier.
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2.2. CDNI Footprint and Capabilities Interface Extensions
Extending the trigger mechanism with optional properties requires the
ability for the dCDN to advertise which optional properties it
supports.
The CDNI Footprint and Capabilities Interface [RFC8008] enables the
dCDN to advertise the capabilities it supports across different
footprints. This document introduces FCI objects to support the
advertisement of these optional properties.
Example use cases
o Trigger types: Advertise which trigger types are supported by the
dCDN. CDNI defines three trigger types (purge, invalidate, pre-
position), but it does not necessarily mean that all dCDNs support
all of them. The uCDN may prefer to work only with dCDN that
support what the uCDN needs.
o Content selection rule types: Advertise which selection types are
supported. For example, if adding content regex as a means to
match on content URLs, not all dCDN would support it. For
playlist mapping, advertise which types and versions of protocols
are supported, e.g. HLS.vX/DASH.vY/MSS.vX, DASH templates. Note
that the version string or schema are protocol specific.
o Trigger extensions: Advertise which trigger extensions object
types are supported by the dCDN.
3. CI/T Version 2
[RFC8007] does not define a version number and versioning scheme.
We, therefore, designate the interface and objects as defined in
section 5 of [RFC8007] as version 1. The following sections define
version 2 of the CI/T objects and their properties as extensions of
version 1.
3.1. CI/T Objects V2
Version 2 of the CI/T interface requires the support of the following
objects:
o CI/T Commands v2: A trigger command request using the payload type
ci-trigger-command.v2. Version 2 MUST only use "trigger.v2"
objects as defined in Section 3.2.1, instead of "trigger" objects.
All other properties of the trigger command v2 are as defined in
section 5.1.1 of [RFC8007].
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o Trigger Status Resource v2: A trigger status resource response
using the payload type ci-trigger-status.v2. Version 2 MUST only
use "trigger.v2" objects as defined in Section 3.2.1, instead of a
"trigger" object, as well as "errors.v2" objects as defined in
Section 3.2.6, instead of a "errors" object All other properties
of the trigger status v2 are as defined in section 5.1.2 of
[RFC8007]. The errors array "errors.v2" is a list of all errors
that occurred in any of the downstream CDNs along the execution
path. When a downstream CDN, dCDN-A, propagates a trigger to
another downstream CDN, dCDN-B, it MUST also propagated back all
errors reported by dCDN-B in the trigger status resource and add
them to its own trigger status resource.
o Trigger Collections: The payload type ci-trigger-collection is
used with no changes and as defined in 5.1.3 of [RFC8007].
Usage example of version 2 of trigger command
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REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: triggers.dcdn.example.com
Accept: */*
Content-Type: application/cdni; ptype=ci-trigger-command.v2
{
"trigger.v2": { <properties of a trigger.v2 object> },
"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.v2
Location: https://triggers.dcdn.example.com/triggers/0
Server: example-server/0.1
{
"errors.v2": [ { <properties of 1st error.v2 object> },
...,
{ <properties of Nth error.v2 object> }
],
"ctime": 1462351690,
"etime": 1462351698,
"mtime": 1462351690,
"status": "pending",
"trigger.v2": { <properties of a trigger.v2 object> }
}
Usage example of version 2 of trigger status for the trigger created
in the above trigger command example:
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REQUEST:
GET /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: triggers.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.v2
{
"errors.v2": [ { <properties of 1st error.v2 object> },
...,
{ <properties of Nth error.v2 object> }
],
"ctime": 1462351690,
"etime": 1462351698,
"mtime": 1462351690,
"status": "pending",
"trigger.v2": { <properties of a trigger.v2 object> }
}
3.2. Properties of CI/T Version 2 objects
This section defines the values that can appear in the top-level
objects described in Section 3.1, and their encodings.
3.2.1. Trigger Specification Version 2
Version 2 of the Trigger Specification adds the following properties
on top of the existing properties of the trigger specification
defined in section 5.2.1 of [RFC8007].
Property: content.regexs
Description: Regexs of content URLs to which the CI/T trigger
command applies.
Type: A JSON array of RegexMatch objects (see Section 3.2.2).
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Mandatory: No, but at least one of "metadata.*" or "content.*"
MUST be present and non-empty.
Property: content.playlists
Description: Playlists of content the CI/T trigger command
applies to.
Type: A JSON array of Playlist objects (see Section 3.2.3).
Mandatory: No, but at least one of "metadata.*" or "content.*"
MUST be present and non-empty.
Property: extensions
Description: Array of trigger extension data.
Type: Array of GenericTriggerExtension objects (see
Section 3.2.5.2).
Mandatory-to-Specify: No. The default is no extensions.
Example of an invalidation trigger.v2 with a list of regex objects, a
list of playlist objects, and extensions:
{
"trigger.v2": {
"type": "invalidate",
"content.regexs": [ <list of RegexMatch objects> ],
"content.playlists": [ <list of Playlist objects> ],
"extensions": [ <list of GenericTriggerExtension objects ]
},
"cdn-path": [ "AS64496:1" ]
}
3.2.2. RegexMatch
A RegexMatch consists of a regular expression string a URI is matched
against, and flags describing the type of match. It is encoded as a
JSON object with following properties:
Property: regex
Description: A regular expression for URI matching.
Type: A regular expression to match against the URI, i.e
against the path-absolute and the query string parameters
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[RFC3986]. The regular expression string MUST be compatible
with PCRE [PCRE841].
Note: Because '\' has special meaning in JSON [RFC8259] as the
escape character within JSON strings, the regular expression
character '\' MUST be escaped as '\\'.
Mandatory: Yes.
Property: case-sensitive
Description: Flag indicating whether or not case-sensitive
matching should be used.
Type: JSON boolean. Either "true" (the matching is case
sensitive) or "false" (the matching is case insensitive).
Mandatory: No; default is case-insensitive match (i.e., a value
of "false").
Property: match-query-string
Description: Flag indicating whether to include the query part
of the URI when comparing against the regex.
Type: JSON boolean. Either "true" (the full URI, including the
query part, should be compared against the regex) or "false"
(the query part of the URI should be dropped before comparison
with the given regex).
Mandatory: No; default is "false". The query part of the URI
MUST be dropped before comparison with the given regex. This
makes the regular expression simpler and safer for cases in
which the query parameters are not relevant for the match.
Example of a case sensitive, no query parameters, regex match
against:
"^(https:\/\/video\.example\.com)\/([a-z])\/movie1\/([1-7])\/*(index.
m3u8|\d{3}.ts)$".
This regex matches URLs of domain video.example.com where the path
structure is /(single lower case letter)/(name-of-title)/(single
digit between 1 to 7)/(index.m3u8 or a 3 digit number with ts
extension). For example: https://video.example.com/d/movie1/5/
index.m3u8 or https://video.example.com/k/movie1/4/013.ts.
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{
"regex": "^(https:\\/\\/video\\.example\\.com)\\/([a-z])\\/movie1\
\/([1-7])\\/*(index.m3u8|\\d{3}.ts)$",
"case-sensitive": true,
"match-query-string": false
}
3.2.3. Playlist
A Playlist consists of a full URL and a media protocol identifier.
An implementation that supports a specific playlist media protocol
MUST be able to parse playlist files of that protocol type and
extract, possibly recursively, the URLs to all media objects and/or
sub playlist files, and apply the trigger to each one of them
separately.
Playlist is encoded as a JSON object with following properties:
Property: playlist
Description: A URL to the playlist file.
Type: A URL represented as a JSON string.
Mandatory: Yes.
Property: media-protocol
Description: Media protocol to be when parsing and interpreting
this playlist.
Type: MediaProtocol (see Section 3.2.4).
Mandatory: Yes.
Example of a HLS playlist:
{
"playlist": "https://www.example.com/hls/title/index.m3u8",
"media-protocol": "hls"
}
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3.2.4. MediaProtocol
Media Protocol objects are used to specify registered type of media
protocol (see Section 6.3) used for protocol related operations like
pre-position according to playlist.
Type: JSON string
Example:
"dash"
3.2.5. CI/T Trigger Extensions
A "trigger.v2" object, as defined in Section 3.2.1 includes an
optional array of trigger extension objects. A trigger extension
contain properties that are used as directives for dCDN when
executing the trigger command -- for example, location policies, time
policies and so on. Each such CDNI Trigger extension is a
specialization of a CDNI GenericTriggerExtension object. The
GenericTriggerExtension object abstracts the basic information
required for trigger distribution from the specifics of any given
property (i.e., property semantics, enforcement options, etc.). All
trigger extensions are optional, and it is thus the responsibility of
the extension specification to define a consistent default behavior
for the case the extension is not present.
3.2.5.1. Enforcement Options
The trigger enforcement options concept is in accordance with the
metadata enforcement options as defined in section 3.2 of [RFC8006].
The GenericTriggerExtension object defines the properties contained
within it as well as whether or not the properties are "mandatory-to-
enforce". If the dCDN does not understand or support a mandatory-to-
enforce property, the dCDN MUST NOT execute the trigger command. If
the extension is not mandatory-to-enforce, then that
GenericTriggerExtension object can be safely ignored and the trigger
command can be processed in accordance with the rest of the CDNI
Trigger spec.
Although a CDN MUST NOT execute a trigger command if a mandatory-to-
enforce extension cannot be enforced, it could still be safe to
redistribute that trigger (the "safe-to-redistribute" property) to
another CDN without modification. For example, in the cascaded CDN
case, a transit CDN (tCDN) could convey mandatory-to-enforce trigger
extension to a dCDN. For a trigger extension that does not require
customization or translation (i.e., trigger extension that is safe-
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to-redistribute), the data representation received off the wire MAY
be stored and redistributed without being understood or supported by
the tCDN. However, for trigger extension that requires translation,
transparent redistribution of the uCDN trigger values might not be
appropriate. Certain triggers extensions can be safely, though
perhaps not optimally, redistributed unmodified. For example, pre-
position command might be executed in suboptimal times for some
geographies if transparently redistributed, but it might still work.
Redistribution safety MUST be specified for each
GenericTriggerExtension property. If a CDN does not understand or
support a given GenericTriggerExtension property that is not safe-to-
redistribute, the CDN MUST set the "incomprehensible" flag to true
for that GenericTriggerExtension object before redistributing it.
The "incomprehensible" flag signals to a dCDN that trigger metadata
was not properly transformed by the tCDN. A CDN MUST NOT attempt to
execute a trigger that has been marked as "incomprehensible" by a
uCDN.
tCDNs MUST NOT change the value of mandatory-to-enforce or safe-to-
redistribute when propagating a trigger to a dCDN. Although a tCDN
can set the value of "incomprehensible" to true, a tCDN MUST NOT
change the value of "incomprehensible" from true to false.
Table 1 describes the action to be taken by a tCDN for the different
combinations of mandatory-to-enforce ("MtE") and safe-to-redistribute
("StR") properties when the tCDN either does or does not understand
the trigger extension object in question:
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+-------+-------+------------+--------------------------------------+
| MtE | StR | Extension | Trigger action |
| | | object | |
| | | understood | |
| | | by tCDN | |
+-------+-------+------------+--------------------------------------+
| False | True | True | Can execute and redistribute. |
| False | True | False | Can execute and redistribute. |
| False | False | False | Can execute. MUST set |
| | | | "incomprehensible" to true when |
| | | | redistributing. |
| False | False | True | Can execute. Can redistribute after |
| | | | transforming the trigger extension |
| | | | (if the CDN knows how to do so |
| | | | safely); otherwise, MUST set |
| | | | "incomprehensible" to true when |
| | | | redistributing. |
| True | True | True | Can execute and redistribute. |
| True | True | False | MUST NOT execute but can |
| | | | redistribute.. |
| True | False | True | Can execute. Can redistribute after |
| | | | transforming the trigger extension |
| | | | (if the CDN knows how to do so |
| | | | safely); otherwise, MUST set |
| | | | "incomprehensible" to true when |
| | | | redistributing. |
| True | False | False | MUST NOT serve. MUST set |
| | | | "incomprehensible" to true when |
| | | | redistributing. |
+-------+-------+------------+--------------------------------------+
Table 1: Action to be taken by a tCDN for the different combinations
of MtE and StR properties
Table 2 describes the action to be taken by a tCDN for the different
combinations of mandatory-to-enforce and "incomprehensible"
("Incomp") properties, when the dCDN either does or does not
understand the trigger extension object in question:
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+-------+--------+---------------+----------------------------------+
| MtE | Incomp | Extension | Trigger action |
| | | object | |
| | | understood by | |
| | | dCDN | |
+-------+--------+---------------+----------------------------------+
| False | False | True | Can execute. |
| False | True | True | Can execute but MUST NOT |
| | | | interpret/apply any trigger |
| | | | extension marked as |
| | | | "incomprehensible". |
| False | False | False | Can execute. |
| False | True | False | Can execute but MUST NOT |
| | | | interpret/apply any trigger |
| | | | extension marked as |
| | | | "incomprehensible". |
| True | False | True | Can execute. |
| True | True | True | MUST NOT execute. |
| True | False | False | MUST NOT execute. |
| True | True | False | MUST NOT execute. |
+-------+--------+---------------+----------------------------------+
Table 2: Action to be taken by a dCDN for the different combinations
of MtE and Incomp properties
3.2.5.2. GenericExtensionObject
A GenericTriggerExtension object is a wrapper for managing individual
CDNI Trigger extensions in an opaque manner.
Property: generic-trigger-extension-type
Description: Case-insensitive CDNI Trigger extension object
type.
Type: String containing the CDNI Payload Type [RFC7736] of the
object contained in the generic-trigger-extension-value
property (see table in Section 6.1).
Mandatory-to-Specify: Yes.
Property: generic-trigger-extension-value
Description: CDNI Trigger extension object.
Type: Format/Type is defined by the value of the generic-
trigger-extension-type property above.
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Mandatory-to-Specify: Yes.
Property: mandatory-to-enforce
Description: Flag identifying whether or not the enforcement of
this trigger extension is mandatory.
Type: Boolean
Mandatory-to-Specify: No. Default is to treat the trigger
extension as mandatory-to-enforce (i.e., a value of True).
Property: safe-to-redistribute
Description: Flag identifying whether or not this trigger
extension can be safely redistributed without modification.
Type: Boolean
Mandatory-to-Specify: No. Default is to allow transparent
redistribution (i.e., a value of True).
Property: incomprehensible
Description: Flag identifying whether or not any CDN in the
chain of delegation has failed to understand and/or failed to
properly transform this trigger extension object. Note: This
flag only applies to trigger extension objects whose safe-to-
redistribute property has a value of False.
Type: Boolean
Mandatory-to-Specify: No. Default is comprehensible (i.e., a
value of False).
Example of a GenericTriggerExtension containing a specific trigger
extension object:
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{
"generic-trigger-extension-type":
<Type of this trigger extension object>,
"generic-trigger-extension-value":
{
<properties of this trigger extension object>
},
"mandatory-to-enforce": true,
"safe-to-redistribute": true,
"incomprehensible": false
}
3.2.6. Error Description Version 2
Version 2 of the Error Description adds the "cdn" property on top of
the existing properties of the trigger Error Description as defined
in section 5.2.6 of [RFC8007]. The "cdn" property identifies the CDN
in which the error have occurred.
Property: cdn
Description: The CDN PID of the CDN where the error occurred.
Type: A non-empty JSON string, where the string is a CDN PID as
defined in section 4.6 of [RFC8007].
Mandatory: Yes.
Example of an errors.v2 with a an error of unsupported location
policy extension object:
{
"errors.v2": [
{
"content.urls": [
"https://newsite.example.com/index.html"
],
"description": "unrecoginzed extension type CIT.LocationPolicy",
"error": "eunsupported",
"cdn": "AS64496:1"
},
]
}
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3.2.7. Error codes
This document adds the error code "eextension" to the error codes
table defined in section 5.2.6 of [RFC8007]. This error code
designates that an error occurred while parsing a generic trigger
extension, or that the specific extension is not supported by the
CDN. A CDN that fails to parse or execute a generic extension object
MUST report it using the "errors.v2" array within the trigger status
resource, while setting the error code to "eextension" and providing
an appropriate description. The "eextension" error code is a
registered type of "CDNI CI/T Trigger Error Codes" (see Section 6.2).
4. Trigger Extension Objects
The objects defined below are intended to be used in the
GenericTriggerExtension object's generic-trigger-extension-value
field as defined in section Section 3.2.5.2, and their generic-
trigger-extension-type property MUST be set to the appropriate CDNI
Payload Type as defined in Section 6.1 .
4.1. LocationPolicy extension
A content operation may be relevant for a specific geographical
region, or need to be excluded from a specific region. In this case,
the trigger should be applied only to parts of the network that are
either "included" or "not excluded" by the location policy. Note
that the restrictions here are on the cache location rather than the
client location.
The LocationPolicy object defines which CDN or cache locations for
which the trigger command is relevant.
Example use cases:
o Pre-position: Certain contracts allow for pre-positioning or
availability of contract in all regions except for certain
excluded regions in the world, including caches. For example,
some content cannot ever knowingly touch servers in a specific
country, including cached content. Therefore, these regions MUST
be excluded from a pre-positioning operation.
o Purge: In certain cases, content may have been located on servers
in regions where the content must not reside. In such cases a
purge operation to remove content specifically from that region,
is required.
Object specification
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Property: locations
Description: An Access List that allows or denies (blocks) the
trigger execution per cache location.
Type: Array of LocationRule objects (see Section 4.2.2.1 of
[RFC8006])
Mandatory-to-Specify: Yes.
If a location policy object is not listed within the trigger command,
the default behavior is to execute the trigger in all available
caches and locations of the dCDN.
The trigger command is allowed, or denied, for a specific cache
location according to the action of the first location whose
footprint matches against that cache's location. If two or more
footprints overlap, the first footprint that matches against the
cache's location determines the action a CDN MUST take. If the
"locations" property is an empty list or if none of the listed
footprints match the location of a specific cache location, then the
result is equivalent to a "deny" action.
The following is an example of pre-position trigger specification
with a trigger-extensions array including a location policy that
allows the trigger execution in the US but blocks its execution in
Canada:
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{
"trigger": {
"type": "preposition",
"content.urls": [
"https://www.example.com/a/b/c/1",
"https://www.example.com/a/b/c/2"
],
"extensions": [
{
"generic-trigger-extension-type": "CIT.LocationPolicy",
"generic-trigger-extension-value":
{
"locations": [
{
"action": "allow",
"footprints": [
{
"footprint-type": "countrycode",
"footprint-value": ["us"]
}
]
},
{
"action": "deny",
"footprints": [
{
"footprint-type": "countrycode",
"footprint-value": ["ca"]
}
]
}
]
},
"mandatory-to-enforce": true,
"safe-to-redistribute": true,
"incomprehensible": false
}
]
},
"cdn-path": [ "AS64496:1" ]
}
4.2. TimePolicy Extension
A uCDN may wish to perform content management operations on the dCDN
in a specific schedule. The TimePolicy extensions allows the uCDN to
instruct the dCDN to execute the trigger command in a desired time
window.
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Example use cases
* Pre-position: A content provider wishes to pre-populate a new
episode at off-peak time so that it would be ready on caches
(for example home caches) at prime time when the episode is
released for viewing. A scheduled operation enables the uCDN
to direct the dCDN in what time frame to execute the trigger.
The time values are in UNIX epoch.
* Regional schedule: When used in combination with the Location
Policy defined in Section 4.1, the uCDN can trigger separate
commands for different geographical regions, for each region
using a different schedule. This allows the uCDN to control
the execution time per region and, for example, direct the dCDN
to execute at off-peak hours, as they are defined per region.
Object specification
Property: window
Description: A time frame in which the trigger should be
executed.
Type: TimeWindow object (see Section 4.2.3.2 of [RFC8006])
Mandatory-to-Specify: Yes.
If a time policy object is not listed within the trigger command, the
default behavior is to execute the trigger in a time frame most
suitable to the dCDN taking under consideration other constrains and
/ or obligations.
Example of trigger specification with a scheduled time window between
09:00 01/01/2000 UTC and 17:00 01/01/2000 UTC:
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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",
"content.urls": [
"https://www.example.com/a/b/c/1",
"https://www.example.com/a/b/c/2"
],
"extensions": [
{
"generic-trigger-extension-type": "CIT.TimePolicy",
"generic-trigger-extension-value":
{
"window": {
"start": 946717200,
"end": 946746000
}
}
"mandatory-to-enforce": true,
"safe-to-redistribute": true,
"incomprehensible": false
}
],
},
"cdn-path": [ "AS64496:1" ]
}
5. Footprint and Capabilities
This section covers the FCI objects required for advertisement of the
extensions and properties introduced in this document.
5.1. CI/T Versions Capability Object
The CI/T versions capability object is used to indicate support for
one or more CI/T objects versions. Note that the default version as
originally defined in [RFC8007] MUST be implicitly supported
regardless of the versions listed in this capability object.
Property: versions
Description: A list of version numbers.
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Type: An array of JSON strings
Mandatory-to-Specify: No. The default is version 1. A missing
or an empty versions list means that only version 1 of the
interface and objects is supported.
5.1.1. CI/T Versions Capability Object Serialization
The following shows an example of CI/T Versions Capability object
serialization for a dCDN that supports versions 2 and 2.1 of the CI/T
interface.
{
"capabilities": [
{
"capability-type": "FCI.TriggerVersion",
"capability-value": {
"versions": [ "1", "2", "2.1" ]
},
"footprints": [
<Footprint objects>
]
}
]
}
5.2. CI/T Playlist Protocol Capability Object
The CI/T Playlist Protocol capability object is used to indicate
support for one or more MediaProtocols listed in Section 6.3 by the
playlists property of the "trigger.v2" object.
Property: media-protocols
Description: A list of media protocols.
Type: A list of MediaProtocol (from the CDNI Triggers media
protocol types Section 6.3)
Mandatory-to-Specify: No. The default, in case of a missing or
an empty list, is none supported.
5.2.1. CI/T Playlist Protocol Capability Object Serialization
The following shows an example of CI/T Playlist Protocol Capability
object serialization for a dCDN that supports "hls" and "dash".
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{
"capabilities": [
{
"capability-type": "FCI.TriggerPlaylistProtocol",
"capability-value": {
"media-protocols": ["hls", "dash"]
},
"footprints": [
<Footprint objects>
]
}
]
}
5.3. CI/T Trigger Extension Capability Object
The CI/T Generic Extension capability object is used to indicate
support for one or more GenericExtensionObject types.
Property: trigger-extension
Description: A list of supported CDNI CI/T
GenericExtensionObject types.
Type: List of strings corresponding to entries from the "CDNI
Payload Types" registry [RFC7736] that are under the CIT
namespace, and that correspond to CDNI CI/T
GenericExtensionObject objects.
Mandatory-to-Specify: No. The default, in case of a missing or
an empty list, MUST be interpreted as "no
GenericExtensionObject types are supported". A non-empty list
MUST be interpreted as containing "the only
GenericExtensionObject types that are supported".
5.3.1. CI/T Trigger Extension Capability Object Serialization
The following shows an example of CI/T Trigger Extension Capability
object serialization for a dCDN that supports the
"CIT.LocationPolicy" and the "CIT.TimePolicy" objects.
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{
"capabilities": [
{
"capability-type": "FCI.TriggerGenericExtension",
"capability-value": {
"trigger-extension": ["CIT.LocationPolicy", "CIT.TimePolicy"]
},
"footprints": [
<Footprint objects>
]
}
]
}
6. IANA Considerations
6.1. CDNI Payload Types
This document requests the registration of the following CDNI Payload
Types under the IANA CDNI Payload Type registry defined in [RFC7736]:
+-----------------------------+---------------+
| Payload Type | Specification |
+-----------------------------+---------------+
| ci-trigger-command.v2 | RFCthis |
| ci-trigger-status.v2 | RFCthis |
| CIT.LocationPolicy | RFCthis |
| CIT.TimePolicy | RFCthis |
| FCI.TriggerVersion | RFCthis |
| FCI.TriggerPlaylistProtocol | RFCthis |
| FCI.TriggerGenericExtension | RFCthis |
+-----------------------------+---------------+
[RFC Editor: Please replace RFCthis with the published RFC number for
this document.]
6.1.1. CDNI ci-trigger-command.v2 Payload Type
Purpose: The purpose of this payload type is to distinguish version 2
of the CI/T command (and any associated capability advertisement)
Interface: CI/T
Encoding: see Section 3.1
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6.1.2. CDNI ci-trigger-status.v2 Payload Type
Purpose: The purpose of this payload type is to distinguish version 2
of the CI/T status resource response (and any associated capability
advertisement)
Interface: CI/T
Encoding: see Section 3.1
6.1.3. CDNI CI/T LocationPolicy Trigger Extension Type
Purpose: The purpose of this Trigger Extension type is to distinguish
LocationPolicy CIT Trigger Extension objects.
Interface: CI/T
Encoding: see Section 4.1
6.1.4. CDNI CI/T TimePolicy Trigger Extension Type
Purpose: The purpose of this Trigger Extension type is to distinguish
TimePolicy CI/T Trigger Extension objects.
Interface: CI/T
Encoding: see Section 4.2
6.1.5. CDNI FCI CI/T Versions Payload Type
Purpose: The purpose of this payload type is to distinguish FCI
advertisement objects for CI/T Triggers Versions objects
Interface: FCI
Encoding: see Section 5.1.1
6.1.6. CDNI FCI CI/T Playlist Protocol Payload Type
Purpose: The purpose of this payload type is to distinguish FCI
advertisement objects for CI/T Playlist Protocol objects
Interface: FCI
Encoding: see Section 5.2.1
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6.1.7. CDNI FCI CI/T Extension Objects Payload Type
Purpose: The purpose of this payload type is to distinguish FCI
advertisement objects for CI/T Extension objects
Interface: FCI
Encoding: see Section 5.3.1
6.2. CDNI CI/T Trigger Error Codes types
The IANA is requested to update the "CDNI CI/T Error Codes"
subregistry (defined in section 7.3 of [RFC8007] and located at
<https://www.iana.org/assignments/cdni-parameters>) with the
following registration:
+------------+-----------------------------------+------------------+
| Error Code | Description | Specification |
+------------+-----------------------------------+------------------+
| eextension | The dCDN failed to parse a | Section Section |
| | generic extension object, or does | 3.2.7 of this |
| | not support this extension. | document. |
+------------+-----------------------------------+------------------+
6.3. CDNI Media protocol types
The IANA is requested to create a new "CDNI MediaProtocol Types"
subregistry in the "Content Delivery Networks Interconnection (CDNI)
Parameters" registry. The "CDNI Media Protocol Types" namespace
defines the valid Media Protocol object values in
Section Section 3.2.4, used by the Playlist object. Additions to the
MediaProtocol namespace conform to the "Specification Required"
policy as defined in section 4.6 of [RFC8126], where the
specification defines the MediaProtocol Type and the protocol to
which it is associated. The designated expert will verify that new
protocol definitions do not duplicate existing protocol definitions
and prevent gratuitous additions to the namespace.
The following table defines the initial MediaProtocol values
corresponding to the HLS, MSS, and DASH protocols:
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+---------------+-------------------+---------------+---------------+
| MediaProtocol | Description | Specification | Protocol |
| Type | | | Specification |
+---------------+-------------------+---------------+---------------+
| hls | HTTP Live | RFCthis | RFC 8216 |
| | Streaming | | [RFC8216] |
| mss | Microsoft Smooth | RFCthis | MSS [MSS] |
| | Streaming | | |
| dash | Dynamic Adaptive | RFCthis | MPEG-DASH |
| | Streaming over | | [MPEG-DASH] |
| | HTTP (MPEG-DASH) | | |
+---------------+-------------------+---------------+---------------+
[RFC Editor: Please replace RFCthis with the published RFC number for
this document.]
7. Security Considerations
All security considerations listed in section 8 of [RFC8007] and
section 7 of [RFC8008] apply to this document as well.
This document defines the capability to use regular expression within
the trigger spec for more granular content selection. The usage of
regex introduced the risk of regex complexity attacks, a.k.a ReDos
attacks. An attacker may be able to craft a regular expression that
can exhaust server resources and may take exponential time in in the
worst case. An implementation MUST protect itself by at least accept
triggers only from an authenticated party over a secured connection.
An implementation SHOULD also protect itself by using secure
programing techniques and decline trigger commands that use
potentially risky regex, such techniques are readily available in
secure programming literature and are beyond the scope of this
document.
8. Acknowledgments
TBD
9. Contributors
The authors would like to thank all members of the "Streaming Video
Alliance" (SVA) Open Caching Working Group for their contribution in
support of this document.
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10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC8006] Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
"Content Delivery Network Interconnection (CDNI)
Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
<https://www.rfc-editor.org/info/rfc8006>.
[RFC8007] Murray, R. and B. Niven-Jenkins, "Content Delivery Network
Interconnection (CDNI) Control Interface / Triggers",
RFC 8007, DOI 10.17487/RFC8007, December 2016,
<https://www.rfc-editor.org/info/rfc8007>.
[RFC8008] Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
R., and K. Ma, "Content Delivery Network Interconnection
(CDNI) Request Routing: Footprint and Capabilities
Semantics", RFC 8008, DOI 10.17487/RFC8008, December 2016,
<https://www.rfc-editor.org/info/rfc8008>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
10.2. Informative References
[MPEG-DASH]
ISO, "Information technology -- Dynamic adaptive streaming
over HTTP (DASH) -- Part 1: Media presentation description
and segment format", ISO/IEC 23009-1:2014, Edition 2, 05
2014, <http://www.iso.org/standard/65274.html>.
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[MSS] Microsoft, "[MS-SSTR]: Smooth Streaming Protocol",
Protocol Revision 8.0, September 2017,
<https://msdn.microsoft.com/en-us/library/ff469518.aspx>.
[PCRE841] Hazel, P., "Perl Compatible Regular Expressions",
Version 8.41, July 2017, <http://www.pcre.org/>.
[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, DOI 10.17487/RFC6707, September
2012, <https://www.rfc-editor.org/info/rfc6707>.
[RFC7736] Ma, K., "Content Delivery Network Interconnection (CDNI)
Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
December 2015, <https://www.rfc-editor.org/info/rfc7736>.
[RFC8216] Pantos, R., Ed. and W. May, "HTTP Live Streaming",
RFC 8216, DOI 10.17487/RFC8216, August 2017,
<https://www.rfc-editor.org/info/rfc8216>.
Authors' Addresses
Ori Finkelman
Qwilt
6, Ha'harash
Hod HaSharon 4524079
Israel
Phone: +972-72-2221647
Email: orif@qwilt.com
Sanjay Mishra
Verizon
13100 Columbia Pike
Silver Spring, MD 20904
USA
Email: sanjay.mishra@verizon.com
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