CDNI Edge Control Metadata
draft-ietf-cdni-edge-control-metadata-01
| Document | Type | Active Internet-Draft (cdni WG) | |
|---|---|---|---|
| Authors | Alfonso Silóniz , Glenn Goldstein | ||
| Last updated | 2024-04-24 | ||
| Replaces | draft-siloniz-cdni-edge-control-metadata | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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draft-ietf-cdni-edge-control-metadata-01
Content Delivery Networks Interconnection A. Siloniz
Internet-Draft Telefonica
Intended status: Standards Track G. Goldstein
Expires: 26 October 2024 Lumen Technologies
24 April 2024
CDNI Edge Control Metadata
draft-ietf-cdni-edge-control-metadata-01
Abstract
This specification defines configuration metadata objects related to
controlling edge access to resources via content delivery networks
(CDNs) and Open Caching systems. Configuring Cross-Origin Resource
Sharing (CORS) access rules and the dynamic generation of CORS
headers is a key feature of typical configurations, as are the
ability to define response body compression rules and client
connection timeouts.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 October 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 2
3. MI.CrossoriginPolicy . . . . . . . . . . . . . . . . . . . . 3
3.1. MI.AccessControlAllowOrigin . . . . . . . . . . . . . . . 6
3.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 7
4. MI.AllowCompress . . . . . . . . . . . . . . . . . . . . . . 8
5. MI.ClientConnectionControl . . . . . . . . . . . . . . . . . 9
6. Informative Examples . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8.1. CDNI Payload Types . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
10. Normative References . . . . . . . . . . . . . . . . . . . . 12
11. Informative References . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
CDNs typically require a set of configuration metadata to provide
directives for the processing of responses downstream (at the edge
and in the user agent). This document specifies GenericMetadata
objects to meet those requirements, defining edge processing rules
such as Cross-Origin Resource Sharing (CORS) handling, response
compressions, and client connection failures.
2. Requirements
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 [RFC2119].
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3. MI.CrossoriginPolicy
Delegation of traffic between CDNs over an Open Caching node (OCN)
based on Hypertext Transfer Protocol (HTTP) redirection changes the
domain name in the client requests. This represents a cross-origin
request that must be managed appropriately using CORS headers in the
responses.
The dynamic generation of CORS headers is typical in modern HTTP
request processing and avoids CORS validation forwarded to the CDN
origin servers, particularly with the preflight OPTIONS requests.
The CDN Interconnection (CDNI) metadata model requires extensions to
specify how a CDN or Open Caching node should generate and evaluate
these headers.
Required capabilities:
* Set a default value for CORS response headers independent of the
origin request header value.
* Match the origin request header with a list of valid values to
return or not return the CORS response headers.
* Set a list of custom headers that can be exposed to the client
(expose headers).
* Support preflight requests using the OPTIONS method, including
custom header validation, expose headers, and methods.
* Support credentials validation within CORS.
Simple CORS requests are those where both HTTP method and headers in
the request don't require a preflight request. The user agent (UA)
request can include an Origin header set to a URL domain of the
webpage from which the User Agent made it. Depending on the metadata
configuration, the logic to apply by the Open Caching node is:
* Validation of the origin header - Metadata can include a list of
valid domains to validate the request origin header. If it does
not match, the CORS header MUST NOT be included in the response.
* WIldcard usage - Depending on the configuration, the resultant
CORS header to include in the response will be the same as the
request origin header, or a wildcard.
* If no validation of request is included in the origin header, set
a default value for CORS response headers independent of the
origin request header value.
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When a UA makes a request that includes a method or headers that
require a CORS preflight request, the UA will first use the OPTIONS
method to the resource, including the origin header. If CORS is
enabled and the request passes the origin validation, the dCDN SHOULD
respond with the set of headers that indicate what is permitted for
that resource, including one or more of the following:
* Allowed methods
* Allowed credentials
* Allowed request headers
* Maximum age that the OPTIONS request is valid
* Headers that can be exposed to the client
If the returned headers allow the UA browser to provide access to the
resource, the UA will then request the resource with the proper HTTP
method (GET, PUT, POST, etc)
When an upstream CDN (uCDN) configures any of those advanced
parameters, it is requesting the dCDN to generate synthetic responses
to OPTIONS requests. Therefore, no conditional request is performed
to the uCDN origin, and typically to inject the proper CORS headers
in the response to the resource access. The uCDN SHOULD configure
these values taking that into account. If some of the advanced
parameters are empty, the dCDN would not send the corresponding
header into its response to the UA request.
In cases where the uCDN only configures the
MI.AccessControlAllowOrigin subobject, the dCDN will not generate
synthetic responses to OPTIONS requests. Instead, the dCDN will
forward tothe uCDN every OPTIONS request to obtain the response.
MI.CrossoriginPolicy is a GenericMetadata object that allows
configuring dynamically generated CORS headers.
Property: allow-origin
* Description: Validation of simple CORS requests.
* Type: Object MI.AccessControlAllowOrigin (Section 3.1)
* Mandatory-to-Specify: Yes
Property: expose-headers
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* Description: A list of values the dCDN will include in the Access-
Control-Expose-Headers response header to a preflight request.
* Type: Array of strings
* Mandatory-to-Specify: No. If not specified, the default behavior
is to not add the header in the response
Property: allow-methods
* Description: A list of values the OCN will include in the Access-
Control-Allow-Methods response header to a preflight request.
* Type: Array of strings
* Mandatory-to-Specify: No. If not specified, the default behavior
is to not add the header in the response
Property: allow-headers
* Description: A list of values the OCN will include in the Access-
Control-Allow-Headers response header to a preflight request.
* Type: Array of strings
* Mandatory-to-Specify: No. If not specified, the default behavior
is to not add the header in the response
Property: allow-credentials
* Description: The value the OCN will include in the Access-Control-
Allow-Credentials response header to a preflight request.
* Type: Boolean
* Mandatory-to-Specify: No. If not specified, the default behavior
is to not add the header in the response
Property: max-age
* Description: The value the OCN will include in the Access-Control-
Max-Age response header to a preflight request.
* Type: Integer
* Mandatory-to-Specify: No. If not specified, the default behavior
is to not add the header in the response
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Property: no-origin-response-headers
* Description: In the case of a request that has no Origin field,
return this set of headers with the response.
* Type: Array of MI.HTTPHeader objects, defined in Processing Stages
Metadata [SVTA2032].
* Mandatory-to-Specify: No. If not specified, the default behavior
is to not add any CORS response headers
Property: preflight-only
* Description: Setting this flag to "True" the dCDN will only
generate synthetic responses to OPTIONS requests with proper CORS
response headers
* Type: Boolean
* Mandatory-to-Specify: No. The default is "False", so CORS
response headers logic will be injected for all HTTP methods
3.1. MI.AccessControlAllowOrigin
The MI.AccessControlAllowOrigin object has the following properties:
Property: allow-list
* Description: List of valid expressions that will be used to match
the request Origin header. The Origin header is an HTTP
extension. Its value is a version of the Referer header that does
not reveal a path in some specific requests and used for cross-
origin requests. Permitted values for the Origin header are of
the form schema://host[:port] as defined in Sections 3.1, 3.2.2
and 3.2.3 of [RFC3986]
* Type: Array of Strings. Each string represents a pattern for
matching against the Origin header. The pattern can contain the
wildcards "*" and "?", where "*" matches any sequence of pchar
[RFC3986] or "/" characters (including the empty string) and "?"
matches exactly one pchar character. The three literals "$", "*",
and "?" MUST be escaped as "$$", "$*", and "$?" (where "$" is the
designated escape character). All other characters are treated as
literals
* Mandatory-to-Specify: Yes
Property: wildcard-return
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* Description: If "True", the OCN will include a wildcard (*) in the
Access-Control-Allow-Origin response header. If "False", the dcdn
MUST reflect the request origin header in the Access-Control-
Allow-Origin response header.
* Type: Boolean
* Mandatory-to-Specify: Yes
3.2. Examples
The examples below demonstrate how to configure response headers
dynamically for CORS validation.
The following is an example of a simple CORS validation
configuration:
{
"generic-metadata-type": "MI.CrossoriginPolicy",
"generic-metadata-value": {
"allow-origin": {
"allow-list": [
{
"pattern": "*"
}
],
"wildcard-return": true
}
}
}
Figure 1
The following is an example of validation of a preflight request when
some of the headers included in the subsequent object request are not
included in the CORS specification safelist:
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{
"generic-metadata-type": "MI.CrossoriginPolicy",
"generic-metadata-value": {
"allow-origin": {
"allow-list": [
{
"pattern": "*://sourcepage.example.com"
},
"wildcard-return": false
},
"allow-methods": [ "GET", "POST" ],
"allow-credentials": true,
"allow-headers": [ "X-PINGOTHER", "Content-Type" ],
"expose-headers": [ "X-User", "Authorization" ],
"max-age": 3600,
"no-origin-response-headers": false,
"preflight-only": false
}
}
}
Figure 2
4. MI.AllowCompress
Downstream CDNs often have the ability to compress HTTP response
bodies in cases where the client has declared that it can accept
compressed responses (via an Accept-Encoding header), but the source/
origin has returned an uncompressed response.
The specific compression algorithm used by the dCDN is negotiated by
the client's Accept-Encoding header according to [RFC9110] (including
"q=" preferences) and the compression capabilities available on the
dCDN.
In addition, HeaderTransform allows the uCDN to normalize, or modify,
the Accept-Encoding header to allow for fine-grain control over the
selection of the compression algorithm (e.g., gzip, compress,
deflate, br, etc.).
MI.AllowCompress is a new GenericMetadata object that allows the dCDN
to compress content before sending it to the client.
Property: allow-compress
* Description: If set to "True", the dCDN SHOULD try to compress the
response to the client based on the Accept-Encoding request
header.
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* Type: Boolean.
* Mandatory-to-Specify: No. The default is "false".
The following examples illustrate the use of MI.AllowCompress in the
context of the Processing Stages Model that allowed for metadata to
be applied conditionally based on evaluation of HTTP request headers.
See the Processing Stages Metadata Specification [SVTA2032] and
Metadata Model Expression Language (MEL) Specification [SVTA2031]
The following is an example of the usage of MI.AllowCompress:
{
"generic-metadata-type": "MI.AllowCompress",
"generic-metadata-value": {
"allow-compress": true
}
}
Figure 3
More examples can be found in the Informative Examples (Section 6)
section.
5. MI.ClientConnectionControl
Configuration metadata is required to define how connections against
a client are maintained by a dCDN. In some use cases, like video
streaming or other critical object delivery, UA applications
connection to the cache server must be in control to have the best
user experience possible. This metadata allows a uCDN to accommodate
device-specific constraints and performance optimization. A dCDN can
also benefit from this configuration metadata to meet its security
and resource consumption requirements.
MI.ClientConnectionControl is a new GenericMetadata object that
specifies how a dCDN SHOULD manage its connections to UAs.
Property: connection-keep-alive-time-ms
* Description: Specifies the time, in milliseconds, to keep an idle
connection open.
* Type: Integer
* Mandatory-to-Specify: No. When not specified, a default value
selected by the dCDN will be used.
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The following example shows how a connection setup and a keep alive
timeout can be set for client connections to a dCDN:
{
"generic-metadata-type": "MI.ClientConnectionControl",
"generic-metadata-value": {
"connection-keep-alive-time-ms": 3
}
}
Figure 4
6. Informative Examples
The following is an example of an MI.AllowCompress in the context of
the Processing Stages Model (see the Processing Stages Metadata
Specification [SVTA2032]) that allows compression for requests to
objects to the dCDN with extension *.m3u8:
{
"generic-metadata-type": "MI.StageRules",
"generic-metadata-value": {
"match": {
"expression": "req.h.uri *= '*.m3u8'"
},
"stage-metadata": {
"generic-metadata": [
{
"generic-metadata-type": "MI.AllowCompress",
"generic-metadata-value": {
"allow-compress": true
}
}
]
}
}
}
Figure 5
The following is an example of an MI.AllowCompress that allows
compression in the edge by the dCDN based on the client's Accept-
Encoding header:
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{
"generic-metadata-type": "MI.StageRules",
"generic-metadata-value": {
"match": {
"expression": "req.h.accept-encoding *= '*gzip*'"
},
"stage-metadata": {
"generic-metadata": [
{
"generic-metadata-type": "MI.AllowCompress",
"generic-metadata-value": {
"allow-compress": true
}
}
]
}
}
}
Figure 6
7. Security Considerations
The FCI and MI objects defined in the present document are
transferred via the interfaces defined in CDNI [RFC8006] which
describes how to secure these interfaces protecting integrity and
confidentiality while ensuring the authenticity of the dCDN and uCDN.
8. IANA Considerations
8.1. CDNI Payload Types
This document requests the registration of the following entries
under the "CDNI Payload Types" registry hosted by IANA:
+-----------------------------+---------------+
| Payload Type | Specification |
+-----------------------------+---------------+
| MI.CrossoriginPolicy | RFCthis |
+-----------------------------+---------------+
| MI.AccessControlAllowOrigin | RFCthis |
+-----------------------------+---------------+
| MI.AllowCompress | RFCthis |
+-----------------------------+---------------+
| MI.ClientConnectionControl | RFCthis |
+-----------------------------+---------------+
Table 1: CDNI Payload Types
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[RFC Editor: Please replace RFCthis with the published RFC number for
this document.]
9. Acknowledgements
The authors would like to express their gratitude to the members of
the Streaming Video Technology Alliance [SVTA] Open Caching Working
Group for their guidance / contribution / reviews ...)
Particulary the following people contribute in one or other way to
the content of this draft:
* Guillaume Bichot (Broadpeak)
* Christoph Neumann (Broadpeak)
* Chris Lemmons (Comcast)
* Pankaj Chaudhari (Disney Streaming)
* Robert Colantuoni (Disney Streaming)
* Will Power (Lumen)
* Rajeev RK (picoNETS)
* Shmuel Asafi (Qwilt)
* Yoav Gressel (Qwilt)
* Nir Sopher (Qwilt)
* Arnon Warshavsky (Qwilt)
* Eric Klein (Sirius XM)
* Francisco Cano Hila (Telefonica)
* Ben Rosenblum (Vecima)
10. 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>.
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[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>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
11. Informative References
[SVTA] SVTA, "Streaming Video Technology Alliance Home Page",
<https://www.svta.org>.
[SVTA2031] SVTA, "Metadata Expression Language (MEL)",
<https://svta.org/documents/SVTA2031>.
[SVTA2032] SVTA, "Processing Stages Metadata Specification",
<https://svta.org/documents/SVTA2032>.
Authors' Addresses
Alfonso Siloniz
Telefonica
Spain
Email: alfonsosiloniz@gmail.com
Glenn Goldstein
Lumen Technologies
United States of America
Email: glenng1215@gmail.com
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