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.

  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 extracted from this document must
  include Revised BSD License text as described in Section 4.e of the
  Trust Legal Provisions and are provided without warranty as described
  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: [email protected]


  Sanjay Mishra
  Verizon
  13100 Columbia Pike
  Silver Spring, MD 20904
  United States of America
  Email: [email protected]

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