Content Delivery Networks Interconnection G. Bichot
Internet-Draft Broadpeak
Intended status: Standards Track A. Siloniz
Expires: 29 August 2025 Telefonica
G. Goldstein
Lumen Technologies
25 February 2025
CDNI Delivery Metadata
draft-bichot-delivery-metadata-02
Abstract
This specification adds to the core set of configuration metadata
defined in RFC8006, providing delivery metadata to define traffic
types, request delegation behavior for downstream CDN (dCDN) node
selection, and request routing modes of traffic delegation.
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Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 2
3. MI.OcnSelection . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. MI.OcnDelivery . . . . . . . . . . . . . . . . . . . . . 5
4. MI.RequestRouting . . . . . . . . . . . . . . . . . . . . . . 6
5. MI.TrafficType . . . . . . . . . . . . . . . . . . . . . . . 7
6. MI.MediaServiceDescription . . . . . . . . . . . . . . . . . 8
7. Capabilities Advertisements . . . . . . . . . . . . . . . . . 10
7.1. FCI.OcnSelection . . . . . . . . . . . . . . . . . . . . 10
7.2. FCI.RequestRouting . . . . . . . . . . . . . . . . . . . 11
7.3. FCI.MulticastDelivery . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9.1. CDNI Payload Types . . . . . . . . . . . . . . . . . . . 14
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
11. Normative References . . . . . . . . . . . . . . . . . . . . 15
12. Informative References . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
This specification introduces a set of GenericMetadata objects that
guide content delivery. This includes traffic types and service
descriptions, dCDN node selection directives, and request routing
metadata. For background on the Open Caching standards and
interactions between upstream content delivery networks (uCDNs) and
downstream content delivery networks (dCDNs) that these configuration
settings impact, refer to the Open Caching Request Routing Functional
Specification [SVTA2007]
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.OcnSelection
Configuration metadata is required to permit several levels of
downstream Open Caching node (OCN) selection policies. For example,
in a mobile network, several physical locations are possible (i.e.,
candidates) for hosting the OCN that will take charge in the
delegation for the uCDN. This is the case when the cache is
virtualized and deployed dynamically. Depending on the OCN selection
policy, which may be a cost driver, the dCDN may attempt to favor
certain types of caches at the edge, for example.
The available types of OpenCaching nodes are announced by the dCDN
using the FCI.OCNSelection object. The possible types of downstream
nodes are not predefined and might for instance be linked to the
network characteristics such as "EDGE" or "average latency< 10ms"
(i.e., the property ocn-type can be one of these values). The dCDN
can select the node types using the ocn-type property. The uCDN can
also configure the delivery type using the ocn-delivery property, and
specify for instance whether to use MABR (multicast ABR) over a
satellite link or HAS (HTTP Adaptive Streaming) over a cellular
network. The default OCN selection policy is "best-effort", i.e.,
the dCDN tries its best to fulfill the requested policy without
providing guarantees.
For more details on Open Caching node selection, refer to the Open
Casting specification [SVTA2065] and Open Caching Request Routing
Functional Specification [SVTA2007]
MI.OcnSelection is a new GenericMetadata object that allows the uCDN
to indicate a preference to the dCDN, in terms of OCN selection.
Property: ocn-delivery
* Description: Instructs the dCDN to perform delegation operations
for a particular medium and/or a transport arrangement.
* Type: MI.OcnDelivery object
* Mandatory-to-Specify: No. At least one of the two properties,
ocn-type or ocn-delivery, MUST be present.
Property: ocn-type
* Description: Instructs the dCDN to perform delegation operations
for the type of downstream nodes.
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* Type: A string corresponding to one of the node types announced by
the dCDN through the CDNI Footprint & Capabilities Interface
(FCI). Examples include: "HOME" or "EDGE".
* Mandatory-to-Specify: No. At least one of the two properties,
ocn-type or ocn-delivery, MUST be present.
Property: ocn-selection
* Description: Enforces the selection of OCNs, considering the ocn-
type and/or the ocn-delivery properties.
* Type: String. One of "attempt-or-failed", "attempt-or-
besteffort", or "best-effort". For either of the first two
values, the delegation MUST be attempted according to the ocn-type
and/or the ocn-delivery properties. If this is not possible, it
is considered as an error and either fails (configuration failure)
or the dCDN continues with a best-effort procedure. The "best-
effort" value instructs the dCDN to try its best to fulfill the
requested ocn-selection policy with no guarantees. See the Open
Casting specification [SVTA2065] for more explanation related to
the multicast delivery scenario.
* Mandatory-to-Specify: No. The value "best-effort" is the default
OCN selection policy. This property makes sense only when dealing
with multicast delivery:
MI.OcnDelivery.ocn-medium="SATELLITE" and/or (MI.OcnDelivery.ocn-
transport"="MULTICAST" or MI.OcnDelivery.ocn-transport"="MABR")
Property: multicast-mode
* Description: Permits to enforce the dCDN operation mode when
dealing with multicast delivery in addition to unicast delivery
(ocn-selection = "attempt-or-besteffort").
* Type: String. For more insights, please read the Open Casting
specification [SVTA2065].
- "automatic-popular": this (default) mode makes the dCDN always
trying to multicast the most popular content.
- "on-demand" : this mode makes the selection of live content
events to be multicasted controlled by the uCDN through a
dedicated API (see .
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* Mandatory-to-Specify: No. The value "automatic-popular" is the
default multicast mode. This property makes sense only when
dealing with multicast delivery:
MI.OcnDelivery.ocn-medium="SATELLITE" and/or (MI.OcnDelivery.ocn-
transport"="MULTICAST" or MI.OcnDelivery.ocn-transport"="MABR") and
MI.OcnSelection.ocn-selection = "attempt-or-besteffort"
The following is an example of the MI.OcnSelection object:
{
"generic-metadata-type": "MI.OcnSelection",
"generic-metadata-value": {
"ocn-delivery": {
"ocn-medium": "SATELLITE",
"ocn-transport": "MABR"
},
"ocn-type": "EDGE",
"ocn-selection": "attempt-or-failed"
}
}
Figure 1
3.1. MI.OcnDelivery
MI.OcnDelivery is a subobject of MI.OcnSelection that provides
details on how the delegated content should be delivered.
Property: ocn-medium
* Description: Instructs the dCDN to perform delegation operations
for a particular medium.
* Type: String. Must be one of these values: "SATELLITE",
"CELLULAR", "BROADBAND", "TERRESTRIAL".
* Mandatory-to-Specify: No. Either the ocn-medium property or the
ocn-transport property MUST be present.
Property: ocn-transport
* Description: Instructs the dCDN to perform delegation operations
for a particular transport arrangement.
* Type: String. Must be one of these values: "MULTICAST", "MABR"
(Multicast Adaptive Bitrate), "UNICAST" or "HAS" (HTTP Adaptive
Streaming).
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* Mandatory-to-Specify: No. At least one of the two properties
(ocn-medium or ocn-transport) MUST be present.
4. MI.RequestRouting
The uCDN requires the ability to indicate whether Hypertext Transfer
Protocol (HTTP) redirect, Domain Name System (DNS) redirect, and
manifest rewrite are allowed, and indicate which is preferable. This
is REQUIRED in cases where the uCDN would like to delegate the
traffic relying on the iterative method but knows the client will not
support HTTP redirection. In that case, the uCDN needs a means to
force the dCDN to perform request routing based on DNS redirect (or
manifest rewrite).
For more details on Open Caching request routing, refer to the Open
Caching Request Routing Functional Specification [SVTA2007]
This configuration possibility is useful only if the dCDN can
advertise the mode of redirection it supports. There is an ongoing
discussion in the IETF CDNI group to understand the semantics behind
the redirection modes currently in the Footprint & Capabilities
Advertising Interface (I-DNS and I-HTTP). It is not clear whether
this indicates that the dCDN supports one or both delegation modes
(the request routing performed by the uCDN can only be based on DNS
redirect or HTTP redirect, or both), or whether it indicates that the
dCDN supports, as its own request routing mode, DNS redirect and/or
HTTP redirect. The latter is REQUIRED for this new configuration
object to be valid.
MI.RequestRouting is a new GenericMetadata object that allows the
uCDN to force the dCDN request routing mode(s) to be applied when
working in iterative redirection mode. The list of redirection modes
supported by the dCDN is advertised through the FCI.RedirectionMode
object. The list of request routing modes supported by the dCDN is
advertised through the FCI.RequestRoutingMode object documented in
the Capabilities Advertisements (Section 7) section.
Property: request-routing-modes
* Description: Instructs the dCDN to perform request routing
according to one or more preferred modes among those supported and
advertised by the dCDN through the FCI.RequestRouting object. One
must understand that forcing (instead of letting the dCDN request
router select) one particular request routing mode may trigger
some inefficiency in the request routing process.
* Type: Array of iterative request routing modes. The values are:
"DNS", "HTTP", or "MANIFEST_REWRITE".
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* Mandatory-to-Specify: No. By default, all request routing modes
supported by the dCDN can be used by the dCDN as part of its
request routing process.
The following example, illustrates the uCDN forcing the dCDN to use
DNS or HTTP as the method for request routing in case the uCDN
performs an iterative delegation (i.e., iterative redirection mode):
{
"generic-metadata-type": "MI.RequestRouting",
"generic-metadata-value": {
"request-routing-modes": [ "DNS", "HTTP" ]
}
}
Figure 2
5. MI.TrafficType
Content delivery networks often apply different infrastructure,
network routes, and internal metadata for different types of traffic.
Delivery of large static objects (such as software downloads), may,
for example, use different edge servers and network routes than video
stream delivery. In an HTTP adaptive bitrate video service, every
video title corresponds to a set of video files and descriptors
according to different video protocols, and this is independent of
the type of service (video-on-demand, live, catch-up, etc.).
The way the video service is consumed by the user agents can vary.
For instance, a segment that belongs to a video on demand (VOD) title
can be requested for every moment the content is available for the
user agents to consume, while a segment of live content will be only
requested as long as the time-shift duration is configured for that
service. Knowing those differences, a CDN or OCN provider can
implement specific strategies that will maximize performance and
thereby provide more available capacity to the upstream provider. It
should be noted that the dCDNs handling of the traffic types is
implementation-specific and not prescribed here.
MI.TrafficType metadata defines a set of descriptors that
characterize either the type or usage of the traffic, enabling CDNs
and OCNs to apply any internal configuration rules without exposing
an unnecessary number of internal details. Note that the
interpretation of these traffic types and application of rules, such
as rate limiting or delivery pacing, are implementation specific.
Property: traffic-type
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* Description: Designates the traffic type. The uCDN will use the
literal that is most representative of the traffic being
delegated.
* Type: String, one of (vod | live | object-download)
* Mandatory-to-Specify: Yes
Property: hints
* Description: Other traffic characteristics that the uCDN can
indicate to the dCDN as suggestions for service optimization.
This property accepts by default free-form unconstrained values
Some SVTA specifications may impose some well defined values as
with the Open Casting specification [SVTA2065]
* Type: Array of strings
* Mandatory-to-Specify: No
The following is an example of MI.TrafficType that designates VOD
catch-up TV viewing:
{
"generic-metadata-type": "MI.TrafficType",
"generic-metadata-value": {
"traffic-type": "vod",
"hints": [ "catch-up"]
}
}
Figure 3
6. MI.MediaServiceDescription
MI.MediaServiceDescription metadata defines a set of descriptors
associated with a media service delegated to the dCDN. This metadata
can be used by the CDN or OCN provider to implement specific
strategies that will maximize performance. Note that these
strategies are implementation specific and not specified in this
document. With knowledge of the streaming manifest URL, for example,
the dCDN MAY implement segment prefetching strategies. Furthermore,
the notion of a media service MAY allow the CDN or OCN provider to
track and monitor streaming sessions in a more comprehensive manner.
Property: manifestURL
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* Description: Path of the manifest (mpd or m3u8) file related to
this media service.
* Type: String.
* Mandatory-to-Specify: No.
Property: mediaServiceName
* Description: String describing or identifying the media service.
* Type: String.
* Mandatory-to-Specify: No.
Property: maximumBitrate
* Description: This is the maximum bitrate in bits per second (bps)
attached to the service delivery. If the service is composed with
several representations/playlists then this property bounds (i.e.
capes) the usage of all or any of the representation/playlist that
has a published bitrate, below this property's value. In
multicast, the property's value indicates the maximum bitrate
provisioned for the service whatever the
representation(s)/playlist(s) that is(are) sent (concurrently).
This property must be set according to the maximum bitrate
dedicated to the uCDN by the dCDN and published through
FCI.MulticastDelivery (limit types "ingress").In unicast, the
property's value indicates the maximum bitrate provisioned for the
service whatever the representation/playlist that is downstream.
This property must be set according to the maximum bitrate
dedicated to the uCDN by the dCDN and published through
FCI.CapacityLimit (limit type "ingress")..
* Type: integer.
* Mandatory-to-Specify: No. If not specified,the uCDN relies
entirely on the dCDN for all uCDN multicast services delivery. It
is strongly encouraged to specify a maximum bit-rate for allowing
the uCDN to operate multicast delivery for several concurrent
services involving live delivery.
The following example of MI.MediaServiceDescription pointing to the
manifest of a live channel and associates a name to this channel:
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{
"generic-metadata-type": "MI.MediaServiceDescription",
"generic-metadata-value": {
"manifestURL": "/live/channelXYZ/index.mpd",
"mediaServiceName": "ChannelXYZ",
"maximumBitRate": 5000000,
}
}
Figure 4
7. Capabilities Advertisements
This section introduces FCI objects that allow a dCDN to advertise
its specific capabilities related to the MI.OcnSelection and
MI.RequestRouting objects.
7.1. FCI.OcnSelection
This object is used by the dCDN to advertise the supported OCN types
and/or its transport arrangement, and/or the medium supported by
OCNs.
Property: ocn-delivery-list
* Description: A list of supported medium and/or transport
arrangements.
* Type: Array of MI.OcnDelivery objects that specify the allowed
combinations of medium and transport.
* Mandatory-to-Specify: No
Property: ocn-type-list
* Description: A list of supported OCN types.
* Type: Array of strings. Examples include: "HOME" or "EDGE". The
possible types are not predefined and can be freely chosen by the
dCDN.
* Mandatory-to-Specify: No
The following is an example advertising support for Satellite
Multicast Adaptive Bitrate (MABR) OCN delivery:
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{
"capabilities": [
{
"capability-type": "FCI.OcnSelection",
"generic-metadata-value": {
"ocn-delivery-list": [
{
"ocn-medium": "SATELLITE",
"ocn-transport": "MABR"
}
],
"ocn-type-list": [
"HOME",
"EDGE"
]
}
}
]
}
Figure 5
7.2. FCI.RequestRouting
This object is used by the dCDN to advertise the supported request
routing modes. This can be optionally used by the uCDN to further
select a subset of those modes when operating one of the iterative
delegation modes. See the section MI.RequestRouting (Section 4)
Property: request-routing-modes
* Description: A list of supported request routing modes by the
dCDN. This information is useful when the uCDN decides to perform
a delegation in iterative mode.
* Type: Array of strings. Values are: "DNS", "HTTP-R", or
"MANIFEST_REWRITE".
* Mandatory-to-Specify: No. If the dCDN does not advertise the
supported request routing modes, they are all supported by
default.
The following example advertises support for all the request routing
modes:
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{
"capabilities": [
{
"capability-type": "FCI.RequestRouting",
"capability-value": {
"request-routing-modes": [
"DNS",
"HTTP",
"MANIFEST_REWRITE"
]
}
}
]
}
Figure 6
7.3. FCI.MulticastDelivery
The presence of a multicast delivery capability is announced through
the FCI.OcsSelection object. This FCI.MulticastDelivery object
permits to disclose more information about the multicast delivery.
Property: capacity-limits
* Description: An array of FCI.CapacityLimit objects.
* Type: Array
* Mandatory-to-Specify: Yes
Property: traffic-types
* Description: traffic types available
* Type: An array of MI.TrafficType objects
* Mandatory-to-Specify: yes
The following example advertises support for multicast delivery.:
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{
"capabilities":
[
{
"capability-type": "FCI.MulticastDelivery",
"capability-value": {
"capacity-limits": [
{
"id": "capacity_limit_multicast",
"limit-type": "ingress",
"maximum-hard": 50000000,
"maximum-soft": 40000000,
"current": 15000000
},
{
"id": "capacity_limit_multicast",
"limit-type": "egress",
"maximum-hard": 5000000,
"maximum-soft": 4000000
}
]
“traffic-typesâ€: [
{
"traffic-type": "live",
"hints": ["catch-up"]
} ]
},
"footprints": [
{
"footprint-type": "ipv4cidr",
"footprint-value": [
"192.0.2.0/24"
]
}
]
}
]
}
Figure 7
8. Security Considerations
The FCI and MI objects defined in the this document are transferred
via the interfaces defined in CDNI [RFC8006] which describes how to
secure these interfaces by protecting integrity and confidentiality
while ensuring the authenticity of the dCDN and uCDN.
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9. IANA Considerations
9.1. 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.OcnSelection | RFCthis |
+----------------------------+---------------+
| MI.OcnDelivery | RFCthis |
+----------------------------+---------------+
| MI.RequestRouting | RFCthis |
+----------------------------+---------------+
| MI.TrafficType | RFCthis |
+----------------------------+---------------+
| MI.MediaServiceDescription | RFCthis |
+----------------------------+---------------+
| FCI.OcnSelection | RFCthis |
+----------------------------+---------------+
| FCI.RequestRouting | RFCthis |
+----------------------------+---------------+
Table 1: CDNI Payload Types
10. 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 contributions and guidance.
Particulary the following people contribute in one or other way to
the content of this draft:
* Christoph Neumann - Broadpeak
* Will Power - Lumen
* Shmuel Asafi - Qwilt
* Yoav Gressel - Qwilt
* Nir Sopher - Qwilt
* Arnon Warshavsky - Qwilt
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* Francisco Cano Hila - Telefonica
11. 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>.
[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>.
12. Informative References
[SVTA] SVTA, "Streaming Video Technology Alliance Home Page",
<https://www.svta.org>.
[SVTA2007] SVTA, "Open Caching Request Routing Functional
Specification", <https://svta.org/documents/SVTA2007>.
[SVTA2065] SVTA, "SVTA Open Casting",
<https://svta.org/documents/SVTA2065>.
[SVTA5044] SVTA, "Open Caching Implementation Guidelines",
<https://svta.org/documents/SVTA5044>.
Authors' Addresses
Guillaume Bichot
Broadpeak
France
Email: guillaume.bichot@broadpeak.tv
Alfonso Siloniz
Telefonica
Spain
Email: alfonsosiloniz@gmail.com
Glenn Goldstein
Lumen Technologies
United States of America
Email: glenng1215@gmail.com
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