RFC9388: Content Delivery Network Interconnection (CDNI) Footprint Types: Country Subdivision Code and Footprint Union
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Related keywords:
(Footprint and Capabilities Semantics)
(Request Routing)
Internet Engineering Task Force (IETF) N. Sopher
Request for Comments: 9388 Qwilt
Updates: 8008 S. Mishra
Category: Standards Track Verizon
ISSN: 2070-1721 July 2023
Content Delivery Network Interconnection (CDNI) Footprint Types: Country
Subdivision Code and Footprint Union
Abstract
Open Caching architecture is a use case of Content Delivery Network
Interconnection (CDNI) in which the commercial Content Delivery
Network (CDN) is the upstream CDN (uCDN) and the ISP caching layer
serves as the downstream CDN (dCDN). RFC 8006 defines footprint
types that are used for footprint objects as part of the Metadata
interface (MI). The footprint types are also used for the Footprint
& Capabilities Advertisement interface (FCI) as defined in RFC 8008.
This document defines two new footprint types. The first footprint
type defined is an ISO 3166-2 country subdivision code. Defining
this country subdivision code improves granularity for delegation as
compared to the ISO 3166-1 country code footprint type defined in RFC
8006. The ISO 3166-2 country subdivision code is also added as a new
entity domain type in the "ALTO Entity Domain Types" registry defined
in Section 7.4 of RFC 9241. The second footprint type defines a
footprint union to aggregate footprint objects. This allows for
additive semantics over the narrowing semantics defined in Appendix B
of RFC 8008 and therefore updates RFC 8008. The two new footprint
types are based on the requirements raised by Open Caching but are
also applicable to CDNI use cases in general.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9388.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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in the Revised BSD License.
Table of Contents
1. Introduction
1.1. Terminology
1.2. Requirements Language
2. CDNI Metadata Additional Footprint Types
2.1. CDNI Metadata "subdivisioncode" Footprint Type
2.1.1. CDNI Metadata "subdivisioncode" Data Type
2.1.1.1. CDNI Metadata "subdivisioncode" Data Type
Description
2.1.2. CDNI Metadata "subdivisioncode" Footprint Type
Description
2.2. CDNI Metadata "footprintunion" Footprint Type
2.2.1. CDNI Metadata "footprintunion" Data Type
2.2.2. CDNI Metadata "footprintunion" Footprint Type
Description
3. ALTO Property Map Service Entity
3.1. SUBDIVISIONCODE Domain
3.1.1. Entity Domain Type
3.1.2. Domain-Specific Entity Identifiers
3.1.3. Hierarchy and Inheritance
4. IANA Considerations
4.1. CDNI Metadata Footprint Types
4.2. ALTO Entity Domain Types
5. Security Considerations
6. References
6.1. Normative References
6.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction
The Streaming Video Technology Alliance [SVTA] is a global
association that works to solve streaming video challenges in an
effort to improve end-user experience and adoption. The Open Caching
Working Group [OCWG] of the SVTA is focused on the delegation of
video delivery requests from commercial Content Delivery Networks
(CDNs) to a caching layer at the ISP's network. Open Caching
architecture is a specific use case of Content Delivery Network
Interconnection (CDNI) where the commercial CDN is the upstream CDN
(uCDN) and the ISP caching layer is the downstream CDN (dCDN). The
"Open Caching Request Routing Functional Specification" [OC-RR]
defines the Request Routing process and the interfaces that are
required for its provisioning. This document defines and registers
CDNI Footprint and Capabilities objects [RFC8008] that are required
for Open Caching Request Routing.
For consistency with other CDNI documents, this document follows the
CDNI convention of using "uCDN" and "dCDN" to represent the
commercial CDN and ISP caching layer, respectively.
This document registers two CDNI Metadata footprint types
(Section 7.2 of [RFC8006]) for the defined objects:
* Country subdivision code footprint type (e.g., for a dCDN
advertising a footprint that is specific to a state in the United
States of America)
* Footprint union footprint type (for a dCDN advertising a footprint
that consists of a group built from multiple footprint types,
e.g., both IPv4 and IPv6 client subnets)
1.1. Terminology
The following terms are used throughout this document:
CDN: Content Delivery Network
Additionally, this document reuses the terminology defined in
[RFC6707], [RFC7336], [RFC8006], and [RFC8008]. Specifically, we use
the following CDNI abbreviations:
uCDN: upstream CDN (see [RFC7336])
dCDN: downstream CDN (see [RFC7336])
1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. CDNI Metadata Additional Footprint Types
Section 5 of [RFC8008] describes the Footprint & Capabilities
Advertisement interface (FCI) Capability Advertisement object, which
includes an array of CDNI footprint objects. Each such object has a
footprint type and a footprint value, as described in Section 4.2.2.2
of [RFC8006]. This document defines additional footprint types,
beyond those mentioned in [RFC8006].
2.1. CDNI Metadata "subdivisioncode" Footprint Type
Section 4.3.8 of [RFC8006] specifies the "countrycode" footprint type
for listing [ISO3166-1] alpha-2 codes. Using footprint objects of
this type, one can define an FCI Capability Advertisement object
footprint constraint that matches a specific country. This document
defines the "subdivisioncode" simple data type as well as a footprint
type, allowing the dCDN to define constraints that match geographic
areas with better granularity, specifically using the [ISO3166-2]
country subdivision codes.
2.1.1. CDNI Metadata "subdivisioncode" Data Type
The "subdivisioncode" data type specified in Section 2.1.1.1
describes a country-specific subdivision using a code as defined in
[ISO3166-2]. The data type is added to the list of data types
described in Section 4.3 of [RFC8006] that are used as properties of
CDNI Metadata objects.
2.1.1.1. CDNI Metadata "subdivisioncode" Data Type Description
An [ISO3166-2] code in lowercase. Each code consists of two parts
separated by a hyphen. As per [ISO3166-2], the first part is the
[ISO3166-1] code of the country and the second part is a string of up
to three alphanumeric characters.
Type: String
Example country subdivision codes:
* "ca-on"
* "us-ny"
2.1.2. CDNI Metadata "subdivisioncode" Footprint Type Description
The "subdivisioncode" simple data type specified in Section 2.1.1 is
added to the data types listed as footprint types in Section 4.2.2.2
of [RFC8006].
Figure 1 is an example using a footprint object of type
"subdivisioncode". The footprint object in this example creates a
constraint that matches clients in the state of either New Jersey or
New York, USA (ISO [ISO3166-2] codes "US-NJ" and "US-NY",
respectively).
{
"capabilities": [
{
"capability-type": <CDNI capability object type>,
"capability-value": <CDNI capability object>,
"footprints": [
{
"footprint-type": "subdivisioncode",
"footprint-value": ["us-nj", "us-ny"]
}
]
}
]
}
Figure 1: Illustration of Country Subdivision Code Footprint
Advertisement
2.2. CDNI Metadata "footprintunion" Footprint Type
As described in Section 5 of [RFC8008], the FCI Capability
Advertisement object includes an array of CDNI footprint objects.
Appendix B of [RFC8008] specifies the semantics for Footprint
Advertisement such that multiple footprint constraints are additive.
This implies that the advertisement of different footprint types
narrows the dCDN's candidacy cumulatively.
Sections 4.3.5 and 4.3.6 of [RFC8006] specify the "ipv4cidr" and the
"ipv6cidr" footprint types, respectively, for listing IP unscoped
address blocks. Using footprint objects of these types, one can
define FCI Capability Advertisement object footprint constraints that
match either IPv4 or IPv6 clients, but not both. This is due to the
described "narrowing" semantic of the Footprint Objects array, as
described in Appendix B of [RFC8008], that prevents the usage of
these objects together to create a footprint constraint that matches
IPv4 clients with IPv6 clients.
Figure 2 is an example attempting to create an object that matches
IPv4 clients of subnet "192.0.2.0/24" as well as IPv6 clients of
subnet "2001:db8::/32". Such a definition results in an empty list
of clients, as the constraints are additives and a client address
cannot be both IPv4 and IPv6.
{
"capabilities": [
{
"capability-type": <CDNI capability object type>,
"capability-value": <CDNI capability object>,
"footprints": [
{
"footprint-type": "ipv4cidr",
"footprint-value": ["192.0.2.0/24"]
},
{
"footprint-type": "ipv6cidr",
"footprint-value": ["2001:db8::/32"]
}
]
}
]
}
Figure 2: Example of Narrowing Semantic Illustrating
Advertisement of a Null Footprint
To overcome the described limitation and allow a list of footprint
constraints that match both IPv4 and IPv6 client subnets, this
document defines the "footprintunion" footprint type. This footprint
type allows the collection of multiple footprint-objects into a
unified object. Therefore, it resolves the above limitation and can
be particularly applicable to unify semantically related objects: for
example, an IPv4 CIDR together with an IPv6 CIDR or a country code
together with a country subdivision code.
Note: to avoid implementation complexity, a "footprintunion" MUST NOT
list any "footprintunion" as a value. As a union of unions is simply
a union, this syntactic restriction does not result with any semantic
limitation.
2.2.1. CDNI Metadata "footprintunion" Data Type
The "footprintunion" data type is based on the footprint object
already defined in Section 4.2.2.2 of [RFC8006]. The footprint value
for a "footprintunion" object is an array of footprint objects, where
the footprint objects MUST be of any footprint type other than
"footprintunion".
2.2.2. CDNI Metadata "footprintunion" Footprint Type Description
The "footprintunion" data type specified in Section 2.2.1 is added to
the data types listed as footprint types in Section 4.2.2.2 of
[RFC8006].
Figure 3 is an example using a footprint union combining both IPv4
and IPv6 client subnets.
{
"capabilities": [
{
"capability-type": <CDNI capability object type>,
"capability-value": <CDNI capability object>,
"footprints": [
{
"footprint-type": "footprintunion",
"footprint-value": [
{
"footprint-type": "ipv4cidr",
"footprint-value": ["192.0.2.0/24"]
},
{
"footprint-type": "ipv6cidr",
"footprint-value": ["2001:db8::/32"]
}
]
}
]
}
]
}
Figure 3: Example of an Advertisement of Footprint Union for
Multiple Classless Inter-Domain Routing (CIDR) Footprint Types
The footprint union also enables composing of footprint objects based
on the country code and country subdivision code. In Figure 4, we
create a constraint covering autonomous system 64496 within the USA
(ISO alpha-2 code "US" as described in [ISO3166-1]) and the Ontario
province of Canada (ISO code "CA-ON" as described in [ISO3166-2]).
{
"capabilities": [
{
"capability-type": <CDNI capability object type>,
"capability-value": <CDNI capability object>,
"footprints": [
{
"footprint-type": "asn",
"footprint-value": ["as64496"]
},
{
"footprint-type": "footprintunion",
"footprint-value": [
{
"footprint-type": "countrycode",
"footprint-value": ["us"]
},
{
"footprint-type": "subdivisioncode",
"footprint-value": ["ca-on"]
}
]
}
]
}
]
}
Figure 4: Example of an Advertisement of Footprint Union for Multiple
Geographical Footprint Types
3. ALTO Property Map Service Entity
Section 6 of [RFC9241] describes how to represent footprint objects
as entities in the ALTO property map. The approach is to represent
the footprint type as an entity domain type of the ALTO entity and
the footprint value as its domain-specific identifier. [RFC9241]
further refers to the representation of footprint objects of types
"asn" and "countrycode". Here, we extend this definition to the
"subdivisioncode" footprint type.
3.1. SUBDIVISIONCODE Domain
The SUBDIVISIONCODE domain associates property values that define
codes for the names of the principal subdivisions.
3.1.1. Entity Domain Type
The entity domain type of the SUBDIVISIONCODE domain is
"subdivisioncode" (in lowercase).
3.1.2. Domain-Specific Entity Identifiers
The entity identifier of an entity in a SUBDIVISIONCODE is encoded as
an alpha-2 [ISO3166-1] country code, followed by a separator and up
to three alphanumeric characters.
3.1.3. Hierarchy and Inheritance
There is no hierarchy or inheritance for properties associated with
country subdivision codes.
4. IANA Considerations
4.1. CDNI Metadata Footprint Types
Section 7.2 of [RFC8006] specifies the "CDNI Metadata Footprint
Types" subregistry within the "Content Delivery Network
Interconnection (CDNI) Parameters" registry.
This document registers two footprint types in that subregistry as
defined in Sections 2.1 and 2.2:
+=================+=================================+===========+
| Footprint Type | Description | Reference |
+=================+=================================+===========+
| subdivisioncode | ISO 3166-2 country subdivision | RFC 9388 |
| | code: alpha-2 country code, | |
| | followed by a hyphen-minus and | |
| | up to 3 characters from A-Z;0-9 | |
| | as a code within the country | |
+-----------------+---------------------------------+-----------+
| footprintunion | A combination of other | RFC 9388 |
| | footprint objects | |
+-----------------+---------------------------------+-----------+
Table 1: Additions to the CDNI Metadata Footprint Types
Subregistry
4.2. ALTO Entity Domain Types
Section 12.3 of [RFC9240] creates the "ALTO Entity Domain Types"
subregistry within the "Application-Layer Traffic Optimization (ALTO)
Protocol" registry.
This document registers an additional ALTO Entity Domain Type within
that subregistry:
+=================+============+=============+==========+=========+
| Identifier | Entity | Hierarchy | Media | Mapping |
| | Identifier | and | Type of | to ALTO |
| | Encoding | Inheritance | Defining | Address |
| | | | Resource | Type |
+=================+============+=============+==========+=========+
| subdivisioncode | See RFC | None | None | false |
| | 9388, | | | |
| | Section | | | |
| | 3.1.2 | | | |
+-----------------+------------+-------------+----------+---------+
Table 2: Addition to the ALTO Entity Domain Types Subregistry
5. Security Considerations
This specification is in accordance with "Content Delivery Network
Interconnection (CDNI) Metadata" and "Content Delivery Network
Interconnection (CDNI) Request Routing: Footprint and Capabilities
Semantics". As such, it is subject to the security and
confidentiality considerations as defined in Section 8 of [RFC8006]
and in Section 7 of [RFC8008], respectively.
6. References
6.1. Normative References
[ISO3166-1]
ISO, "Codes for the representation of names of countries
and their subdivisions -- Part 1: Country code",
ISO 3166-1:2020, Edition 4, August 2020,
<https://www.iso.org/standard/72482.html>.
[ISO3166-2]
ISO, "Codes for the representation of names of countries
and their subdivisions -- Part 2: Country subdivision
code", ISO 3166-2:2020, Edition 4, August 2020,
<https://www.iso.org/standard/72483.html>.
[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>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9240] Roome, W., Randriamasy, S., Yang, Y., Zhang, J., and K.
Gao, "An Extension for Application-Layer Traffic
Optimization (ALTO): Entity Property Maps", RFC 9240,
DOI 10.17487/RFC9240, July 2022,
<https://www.rfc-editor.org/info/rfc9240>.
[RFC9241] Seedorf, J., Yang, Y., Ma, K., Peterson, J., and J. Zhang,
"Content Delivery Network Interconnection (CDNI) Footprint
and Capabilities Advertisement Using Application-Layer
Traffic Optimization (ALTO)", RFC 9241,
DOI 10.17487/RFC9241, July 2022,
<https://www.rfc-editor.org/info/rfc9241>.
6.2. Informative References
[OC-RR] Finkelman, O., Ed., Zurat, B., Sahar, D., Klein, E.,
Hofmann, J., Ma, K.J., Stock, M., Mishra, S., and Y.
Gressel, "Open Caching - Request Routing Functional
Specification", Version 2.0, 15 January 2021,
<https://www.svta.org/product/open-cache-request-routing-
functional-specification/>.
[OCWG] SVTA, "Open Caching", <https://opencaching.svta.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>.
[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
"Framework for Content Distribution Network
Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
August 2014, <https://www.rfc-editor.org/info/rfc7336>.
[SVTA] SVTA, "Streaming Video Technology Alliance",
<https://www.svta.org/>.
Acknowledgements
The authors would like to express their gratitude to Ori Finkelman
and Kevin J. Ma for their guidance and reviews throughout the
development of this document. We would also like to thank all the
Area Directors for their review and feedback in improving this
document.
Authors' Addresses
Nir B. Sopher
Qwilt
6, Ha'harash
Hod HaSharon 4524079
Israel
Email: nir@apache.org
Sanjay Mishra
Verizon
13100 Columbia Pike
Silver Spring, MD 20904
United States of America
Email: sanjay.mishra@verizon.com