| Network Working Group | R. Murray |
| Internet-Draft | B. Niven-Jenkins |
| Intended status: Standards Track | Velocix (Alcatel-Lucent) |
| Expires: April 18, 2016 | October 16, 2015 |
CDNI Control Interface / Triggers
draft-ietf-cdni-control-triggers-09
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.
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].
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 April 18, 2016.
Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved.
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[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.
This document reuses the terminology defined in [RFC6707].
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:
The CI/T interface is a web service offered by the dCDN. It allows CI/T commands to be issued, and triggered activity to be tracked. When the dCDN accepts a CI/T Command it creates a resource describing status of the triggered activity, a Trigger Status Resource. The uCDN can poll Trigger Status Resources to monitor progress.
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 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 http://dcdn.example.com/triggers/uCDN |
[ ] --------------------------------------------------> [ ]--+
| [ ] | (2)
| (3) HTTP 201 Response [ ]<-+
[ ] <-------------------------------------------------- [ ]
| Loc: http://dcdn.example.com/triggers/uCDN/123 |
| |
. . .
. . .
. . .
| |
| (4) GET http://dcdn.example.com/triggers/uCDN/123 |
[ ] --------------------------------------------------> [ ]
| [ ]
| (5) HTTP 200 Trigger Status Resource [ ]
[ ] <-------------------------------------------------- [ ]
| |
| |
Figure 1: Basic CDNI Message Flow for Triggers
The steps in Figure 1 are:
The remainder of this document describes the messages, Trigger Status Resources, and collections of Trigger Status Resources in more detail.
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.
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.
The dCDN MUST reject CI/T Commands from a uCDN that act on another uCDN's data. Security considerations are discussed further in section Section 8.
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.
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/or by 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 SHOULD also maintain collections representing filtered views of the collection of all Trigger Status Resources. These filtered collections are optional-to-implement but, if implemented, the dCDN MUST include links to them in the collection of all Trigger Status Resources. The filtered collections are:
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 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.
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 it is malformed or the uCDN does not have sufficient access rights it MUST either respond with an appropriate 4xx HTTP error code and a Trigger Status Resource MUST NOT be created on the dCDN, or create a 'failed' Trigger Status Resource containing an appropriate error description.
When a CI/T Trigger Command is accepted, the uCDN MUST create a new Trigger Status Resource which will convey a specification of the CI/T Command and its current status. The HTTP response to the dCDN MUST have status code 201 and MUST convey the URI of the Trigger Status Resource in the Location header field. The HTTP response SHOULD include the content of the newly created Trigger Status Resource, this is recommended particularly in cases where the CI/T Trigger Command has completed immediately.
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.
The dCDN SHOULD track and report on progress of CI/T Trigger Commands. If the dCDN is not able to do that, it MUST indicate that it has accepted the request but will not be providing further status updates. To do this, it sets the "status" of the Trigger Status Resource to "processed". In this case, CI/T processing should continue as for a "complete" request, so the Trigger Status Resource MUST be added to the dCDN's collection of Complete Trigger Status Resources. The dCDN SHOULD also provide an estimated completion time for the request, by using the "etime" property of the Trigger Status Resource. This will allow the uCDN to schedule prepositioning after an earlier delete of the same URLs is expected to have finished.
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 prepopulate request for data it has already acquired and which is still valid. In this case, the "status" of the Trigger Status Resource MUST be "processed" or "complete", and the Trigger Status Resource MUST be added to the dCDN's collection of Complete Trigger Status Resources.
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".
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 check for change in status of a Trigger Status Resource or collection of Trigger Status Resources without re-fetching the whole Resource or Collection, Entity Tags SHOULD be included by the dCDN for the uCDN to use as cache validators, as defined in [RFC7232].
The dCDN SHOULD use the cache control headers for responses to GETs for Trigger Status Resources and Collections to indicate the frequency at which it recommends the uCDN should poll for change.
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.
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.
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.
Cancellation of a CI/T Trigger Command is optional-to-implement in the dCDN.
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.
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".
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.
Deletion of a "complete" or "failed" Trigger Status Resource requires no processing in the dCDN other than deletion of the Trigger Status Resource.
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 performs this housekeeping, it MUST have reported the length of time after which completed Trigger Status Resources will be deleted via a property of the collection of all Trigger Status Resources. It is RECOMMENDED that Trigger Status Resources are not automatically deleted by the dCDN for at least 24 hours after they become "complete", "processed", "failed" or "cancelled".
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.
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, 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".
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.
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:
Therefore, if content URLs are transformed by an intermediate CDN in a cascade, that intermediate CDN MUST transform URLs in CI/T Commands it passes to its dCDN.
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.
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.
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.
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.
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.
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.
This section defines the values that can appear in the top level objects described in Section 5.1, and their encodings.
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.
Trigger Type is used in a Trigger Specification to describe trigger action. It MUST be one of the JSON strings in the following table:
| 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). |
This describes the current status of a Trigger. It MUST be one of the JSON strings in the following table:
| JSON String | Description |
|---|---|
| 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. |
A Pattern Match consists of a string pattern to match, and flags describing the type of match.
It is encoded as a JSON object with the following name/value pairs:
Name: case-sensitive
Name: match-query-string
Example of case-sensitive prefix match against "http://www.example.com/trailers/":
{
"pattern": "http://www.example.com/trailers/*",
"case-sensitive": true
}
A JSON number, seconds since the UNIX epoch.
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:
This type is used by the dCDN to report failures in trigger processing.
| 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. |
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
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
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 'http://dcdn.example.com/triggers' is used as the location of the collection of all Trigger Status Resources, and the CDN Provider Id of uCDN is "AS64496:1".
Examples of the uCDN triggering activity in the dCDN:
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.
REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/cdni; ptype=ci-trigger-command
Content-Length: 347
{
"trigger" : {
"type": "preposition",
"metadata.urls" : [ "http://metadata.example.com/a/b/c" ],
"content.urls" : [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
]
},
"cdn-path" : [ "AS64496:1" ]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Sun, 31 Aug 2014 09:53:18 GMT
Content-Length: 472
Content-Type: application/cdni; ptype=ci-trigger-status
Location: http://dcdn.example.com/triggers/0
Server: example-server/0.1
{
"ctime": 1409478798,
"etime": 1409478806,
"mtime": 1409478798,
"status": "pending",
"trigger": {
"content.urls": [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
],
"metadata.urls": [
"http://metadata.example.com/a/b/c"
],
"type": "preposition"
}
}
An example of a CI/T invalidate command, another POST to the collection of all Trigger Status Resources. This instructs the dCDN to re-validate the content at "http://www.example.com/a/index.html", as well as any metadata and content whose URLs are prefixed by "http://metadata.example.com/a/b/" using case-insensitive matching, and "http://www.example.com/a/b/" respectively, using case-sensitive matching.
REQUEST:
POST /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
Content-Type: application/cdni; ptype=ci-trigger-command
Content-Length: 384
{
"trigger" : {
"type": "invalidate",
"metadata.patterns" : [
{ "pattern" : "http://metadata.example.com/a/b/*" }
],
"content.urls" : [ "http://www.example.com/a/index.html" ],
"content.patterns" : [
{ "pattern" : "http://www.example.com/a/b/*",
"case-sensitive" : true
}
]
},
"cdn-path" : [ "AS64496:1" ]
}
RESPONSE:
HTTP/1.1 201 Created
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Length: 551
Content-Type: application/cdni; ptype=ci-trigger-status
Location: http://dcdn.example.com/triggers/1
Server: example-server/0.1
{
"ctime": 1409478799,
"etime": 1409478807,
"mtime": 1409478799,
"status": "pending",
"trigger": {
"content.patterns": [
{
"case-sensitive": true,
"pattern": "http://www.example.com/a/b/*"
}
],
"content.urls": [
"http://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern": "http://metadata.example.com/a/b/*"
}
],
"type": "invalidate"
}
}
Once Trigger Status Resources have been created, the uCDN can check their status as shown in these examples.
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:
REQUEST:
GET /triggers HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 347
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "-6516741166528256414"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"cdn-id": "AS64496:0",
"coll-active": "/triggers/active",
"coll-complete": "/triggers/complete",
"coll-failed": "/triggers/failed",
"coll-pending": "/triggers/pending",
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}
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:
REQUEST:
GET /triggers/pending HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 153
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "5012053611544832286"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}
At this point, if no other Trigger Status Resources had been created, the other filtered views would be empty. For example:
REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 56
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "2986340333785000363"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": []
}
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:
REQUEST:
GET /triggers/0 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 472
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "-4765587034697674779"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1409478798,
"etime": 1409478806,
"mtime": 1409478798,
"status": "pending",
"trigger": {
"content.urls": [
"http://www.example.com/a/b/c/1",
"http://www.example.com/a/b/c/2",
"http://www.example.com/a/b/c/3",
"http://www.example.com/a/b/c/4"
],
"metadata.urls": [
"http://metadata.example.com/a/b/c"
],
"type": "preposition"
}
}
REQUEST:
GET /triggers/1 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 551
Expires: Sun, 31 Aug 2014 09:54:19 GMT
Server: example-server/0.1
Etag: "-7657333837290433420"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:19 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1409478799,
"etime": 1409478807,
"mtime": 1409478799,
"status": "pending",
"trigger": {
"content.patterns": [
{
"case-sensitive": true,
"pattern": "http://www.example.com/a/b/*"
}
],
"content.urls": [
"http://www.example.com/a/index.html"
],
"metadata.patterns": [
{
"pattern": "http://metadata.example.com/a/b/*"
}
],
"type": "invalidate"
}
}
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:
REQUEST: GET /triggers/pending HTTP/1.1 User-Agent: example-user-agent/0.1 Host: dcdn.example.com Accept: */* If-None-Match: "5012053611544832286" RESPONSE: HTTP/1.1 304 Not Modified Content-Length: 0 Expires: Sun, 31 Aug 2014 09:54:19 GMT Server: example-server/0.1 Etag: "5012053611544832286" Cache-Control: max-age=60 Date: Sun, 31 Aug 2014 09:53:19 GMT Content-Type: application/cdni; ptype=ci-trigger-collection
REQUEST: GET /triggers/0 HTTP/1.1 User-Agent: example-user-agent/0.1 Host: dcdn.example.com Accept: */* If-None-Match: "-4765587034697674779" RESPONSE: HTTP/1.1 304 Not Modified Content-Length: 0 Expires: Sun, 31 Aug 2014 09:54:19 GMT Server: example-server/0.1 Etag: "-4765587034697674779" Cache-Control: max-age=60 Date: Sun, 31 Aug 2014 09:53:19 GMT Content-Type: application/cdni; ptype=ci-trigger-status
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:
REQUEST:
GET /triggers/pending HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
If-None-Match: "5012053611544832286"
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 56
Expires: Sun, 31 Aug 2014 09:54:29 GMT
Server: example-server/0.1
Etag: "-4471185573414616962"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:29 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": []
}
REQUEST:
GET /triggers/complete HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
If-None-Match: "2986340333785000363"
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 153
Expires: Sun, 31 Aug 2014 09:54:30 GMT
Server: example-server/0.1
Etag: "-1508172875796647067"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:30 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/0",
"http://dcdn.example.com/triggers/1"
]
}
The dCDN can delete completed and failed Trigger Status Resources to reduce the size of the collections. For example, to delete the "preposition" request from earlier examples:
REQUEST: DELETE /triggers/0 HTTP/1.1 User-Agent: example-user-agent/0.1 Host: dcdn.example.com Accept: */* RESPONSE: HTTP/1.1 204 No Content Date: Sun, 31 Aug 2014 09:53:30 GMT Content-Length: 0 Content-Type: text/html; charset=UTF-8 Server: example-server/0.1
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: 106
Expires: Sun, 31 Aug 2014 09:54:30 GMT
Server: example-server/0.1
Etag: "-1842390246836476263"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:30 GMT
Content-Type: application/cdni; ptype=ci-trigger-collection
{
"staleresourcetime": 86400,
"triggers": [
"http://dcdn.example.com/triggers/1"
]
}
In this example the uCDN has requested prepositioning of "http://newsite.example.com/index.html", but the dCDN was unable to locate metadata for that site:
REQUEST:
GET /triggers/2 HTTP/1.1
User-Agent: example-user-agent/0.1
Host: dcdn.example.com
Accept: */*
RESPONSE:
HTTP/1.1 200 OK
Content-Length: 505
Expires: Sun, 31 Aug 2014 09:54:38 GMT
Server: example-server/0.1
Etag: "-3893590191073700822"
Cache-Control: max-age=60
Date: Sun, 31 Aug 2014 09:53:38 GMT
Content-Type: application/cdni; ptype=ci-trigger-status
{
"ctime": 1409478810,
"errors": [
{
"content.urls": [
"http://newsite.example.com/index.html"
],
"description":
"No HostIndex entry found for newsite.example.com",
"error": "emeta"
}
],
"etime": 1409478818,
"mtime": 1409478814,
"status": "active",
"trigger": {
"content.urls": [
"http://newsite.example.com/index.html"
],
"type": "preposition"
}
}
The IANA is requested to register the following new Payload Types in the CDNI Payload Type Parameter registry defined by [I-D.ietf-cdni-media-type], for use with the 'application/cdni' MIME media type.
RFC Editor Note: Please replace references to [RFCthis] below with this document's RFC number before publication.
| Payload Type | Specification |
|---|---|
| ci-trigger-command | [RFCthis] |
| ci-trigger-status | [RFCthis] |
| ci-trigger-collection | [RFCthis] |
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.
A CI/T implementation MUST support TLS transport for HTTP (https) as per [RFC2818] and [RFC7230].
The use of TLS for transport of the CI/T interface allows:
And, once they have mutually authenticated each other, it allows:
In an environment where any such protection is required, mutually authenticated encrypted transport MUST be used to ensure confidentiality of the CI/T information. To that end, TLS MUST be used by CI/T, including authentication of the remote end.
When TLS is used, the general TLS usage guidance in [RFC7525] MUST be followed.
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.
Note that in a "diamond" configuration, where one uCDN's content can be acquired via more than one directly-connected uCDN, it may not be possible for the dCDN to determine from which uCDN it acquired content. In this case, the dCDN MUST allow each uCDN from which the content could have been acquired to act upon that content using CI/T Commands.
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 rate-limiting acceptance or processing of CI/T Commands, or batching up its processing.
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 party than the authorised dCDN from gaining access to that data. The dCDN MUST ensure that it only exposes CI/T data related to a uCDN to clients it has authenticated as belonging to that uCDN.
The authors thank Kevin Ma for his input, and Carsten Bormann for his review and formalization of the JSON data.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC7159] | Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014. |
| [RFC7230] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014. |
| [RFC7231] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014. |
| [RFC7232] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests", RFC 7232, DOI 10.17487/RFC7232, 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, DOI 10.17487/RFC7525, May 2015. |
| [I-D.greevenbosch-appsawg-cbor-cddl] | Vigano, C. and H. Birkholz, "CBOR data definition language: a notational convention to express CBOR data structures.", Internet-Draft draft-greevenbosch-appsawg-cbor-cddl-06, July 2015. |
| [I-D.ietf-cdni-media-type] | Ma, K., "CDNI Media Type Registration", Internet-Draft draft-ietf-cdni-media-type-06, October 2015. |
| [I-D.ietf-cdni-metadata] | Niven-Jenkins, B., Murray, R., Caulfield, M. and K. Ma, "CDN Interconnection Metadata", Internet-Draft draft-ietf-cdni-metadata-11, July 2015. |
| [I-D.ietf-cdni-redirection] | Niven-Jenkins, B. and R. Brandenburg, "Request Routing Redirection Interface for CDN Interconnection", Internet-Draft draft-ietf-cdni-redirection-13, October 2015. |
| [RFC2818] | Rescorla, E., "HTTP Over TLS", RFC 2818, DOI 10.17487/RFC2818, May 2000. |
| [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. |
| [RFC7336] | Peterson, L., Davie, B. and R. van Brandenburg, "Framework for Content Distribution Network Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336, August 2014. |
| [RFC7337] | Leung, K. and Y. Lee, "Content Distribution Network Interconnection (CDNI) Requirements", RFC 7337, DOI 10.17487/RFC7337, August 2014. |