Stream: Internet Engineering Task Force (IETF)

RFC: 9241 Category: Standards Track Published: July 2022 ISSN: 2070-1721 Authors: J. Seedorf Y. Yang K. Ma J. Peterson J. Zhang HFT Stuttgart Yale University Ericsson NeuStar Tongji University

RFC 9241

Content Delivery Network Interconnection (CDNI) Footprint and Capabilities Advertisement Using Application-Layer Traffic Optimization (ALTO)

Abstract

The Content Delivery Networks Interconnection (CDNI) framework in RFC 6707 defines a set of protocols to interconnect CDNs to achieve multiple goals, including extending the reach of a given CDN. A CDNI Request Routing Footprint & Capabilities Advertisement interface (FCI) is needed to achieve the goals of a CDNI. RFC 8008 defines the FCI semantics and provides guidelines on the FCI protocol, but the exact protocol is not specified. This document defines a new Application-Layer Traffic Optimization (ALTO) service, called "CDNI Advertisement Service", that provides an implementation of the FCI, following the guidelines defined in RFC 8008.

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 howto provide feedback

on it may be obtained at https://www.rfc-editor.org/info/rfc9241.

Copyright Notice

Copyright (c) 2022 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 extracted from this document must include Revised BSD License text as described in Section 4e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.

Table of Contents

1. Introduction 2. Terminology and Background 2.1. Terminology 2.2. Semantics of FCI Advertisement

2.3. ALTO Background and Benefits

3. CDNI Advertisement Service 3.1. Media Type 3.2. HTTP Method 3.3. Accept Input Parameters 3.4. Capabilities 3.5. Uses 3.6. Response 3.7. Examples 3.7.1, IRD 3.7.2. A Basic Example 3.7.3. Incremental Updates 4. CDNI Advertisement Service Using ALTO Network Map 4.1. Network Map Footprint Type: altopid 4.2. Examples 4.2.1. ALTO Network Map for CDNI Advertisements 4.2.2. ALTO PID Footprints in CDNI Advertisements 4.2.3. Incremental Updates 5. Filtered CDNI Advertisement Using CDNI Capabilities 5.1. Media Type

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5.2. HTTP Method 5.3. Accept Input Parameters 5.4. Capabilities 5.5. Uses 5.6. Response 5.7. Examples 5.7.1. ABasic Example

5.7.2. Incremental Updates

6. Query Footprint Properties Using ALTO Property Map Service 6.1. Representing Footprint Objects as Property Map Entities 6.1.1. ASN Domain 6.1.2. COUNTRYCODE Domain

6.2. Representing CDNI Capabilities as Property Map Entity Properties 6.2.1. Defining Information Resource Media Type for Property Type cdni-capabilities

6.2.2. Intended Semantics of Property Type cdni-capabilities

6.3. Examples 6.3.1. Property Map 6.3.2. Filtered Property Map

6.3.3. Incremental Updates

7. IANA Considerations 7.1. application/alto-cdni*json Media Type 7.2. application/alto-cdnifilter+json Media Type 7.3. CDNI Metadata Footprint Types Registry 7.4. ALTO Entity Domain Types Registry 7.5. ALTO Entity Property Types Registry

8. Security Considerations 9. References 9.1. Normative References

9.2. Informative References

Acknowledgments

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Contributors

Authors' Addresses

1. Introduction

The ability to interconnect multiple content delivery networks (CDNs) has many benefits, including increased coverage, capability, and reliability. The Content Delivery Networks Interconnection (CDNI) framework [RFC6707] defines four interfaces to interconnect CDNs: (1) the CDNI Request Routing Interface, (2) the CDNI Metadata Interface, (3) the CDNI Logging Interface, and (4) the CDNI Control Interface.

Among these four interfaces, the CDNI Request Routing Interface provides key functions, as specified in [RFC6707]:

The CDNI Request Routing interface enables a Request Routing function in an Upstream CDN to query a Request Routing function in a Downstream CDN to determine if the Downstream CDN is able (and willing) to accept the delegated Content Request. It also allows the Downstream CDN to control what should be returned to the User Agent in the redirection message by the upstream Request Routing function.

At a high level, therefore, the scope of the CDNI Request Routing Interface contains two main tasks: (1) determining if the (CDN (downstream CDN) is willing to accept a delegated Content Request and (2) redirecting the Content Request coming from a uCDN (upstream CDN) to the proper entry point or entity in the dCDN.

Correspondingly, the Request Routing Interface is broadly divided into two functionalities: (1) the CDNI Footprint & Capabilities Advertisement interface (FCI) defined in [RFC8008] and (2) the CDNI Request Routing Redirection interface (RI) defined in [RFC7975]. This document focuses on the first functionality (CDNI FCI).

Specifically, CDNI FCI allows both an Advertisement from a dCDN to a uCDN (push) and a query from a uCDN to a dCDN (pull) so that the uCDN knows whether it can redirect a particular user request to that dCDN.

A key component in defining the CDNI FCI is defining the objects that describe the footprints and capabilities of a dCDN. Such objects are already specified in Section 5 of [RFC8008]. However, no protocolis defined to transport and update such objects between a uCDN and a dCDN.

To define such a protocol, this document specifies an extension of the Application-Layer Traffic Optimization (ALTO) Protocol [RFC7285] by introducing a new ALTO service called "CDNI Advertisement Service".

Section 2.3 discusses the benefits in using ALTO as a transport protocol.

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2. Terminology and Background

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.

The design of CDNI FCI transport using ALTO assumes an understanding of both FCI semantics and ALTO. Hence, this document starts with a non-normative review of both.

2.1. Terminology

The document uses the CDNI terms defined in [RFC6707], [RFC8006], and [RFC8008]. Also, the document uses the ALTO terms defined in [RFC7285] and [RFC9240]. This document uses the following abbreviations:

ALTO: Application-Layer Traffic Optimization

ASN: | Autonomous System Number

CDN: Content Delivery Network

CDNI: CDN Interconnection

dCDN: Downstream CDN

FCI: CDNI FCI, CDNI Request Routing Footprint & Capabilities Advertisement interface IRD: Information Resource Directory in ALTO

PID: Provider-defined Identifier in ALTO

uCDN: Upstream CDN

2.2. Semantics of FCI Advertisement

[RFC8008] defines the semantics of CDNI FCI, provides guidance on what footprint and capabilities mean in a CDNI context, and specifies the requirements on the CDNI FCI transport protocol. The definitions in [RFC8008] depend on [RFC8006]. Below is a non-normative review of key related points of [RFC8008] and [RFC8006]. For detailed information and normative specification, the reader should refer to these two RFCs.

e Multiple types of mandatory-to-implement footprints (i.e., "ipv4cidr", "ipv6cidr", "asn", and "countrycode") are defined in [RFC8006]. A "set of IP prefixes" can contain both full IP addresses (i.e., a /32 for IPv4 or a /128 for IPv6) and IP prefixes with an arbitrary prefix length. There must also be support for multiple IP address versions, i.e., IPv4 and IPv6, in such a footprint.

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* Multiple initial types of capabilities are defined in [RFC8008] including (1) Delivery Protocol, (2) Acquisition Protocol, (3) Redirection Mode, (4) capabilities related to CDNI Logging, and (5) capabilities related to CDNI Metadata. They are required in all cases and, therefore, considered as mandatory-to-implement capabilities for all CDNI FCI implementations.

* Footprint and capabilities are defined together and cannot be interpreted independently from each other. Specifically, [RFC8008] integrates footprint and capabilities with an approach of "capabilities with footprint restrictions", by expressing capabilities on a per footprint basis.

* Specifically, for all mandatory-to-implement footprint types, footprints can be viewed as constraints for delegating requests to a dCDN: a dCDN footprint advertisement tells the uCDN the limitations for delegating a request to the dCDN. For IP prefixes or Autonomous System Numbers (ASNS), the footprint signals to the uCDN that it should consider the dCDN a candidate only if the IP address of the Request Routing source falls within the prefix set or ASN, respectively. The CDNI specifications do not define how a given uCDN determines what address ranges are in a particular ASN. Similarly, for country codes, a uCDN should only consider the dCDN a candidate if it covers the country of the Request Routing source. The CDNI specifications do not define how a given uCDN determines the country of the Request Routing source. Different types of footprint constraints can be combined together to narrow the dCDN candidacy, i.e., the uCDN should consider the dCDN a candidate only if the request routing source satisfies all the types of footprint constraints in the advertisement.

* Given that a large part of Footprint and Capabilities Advertisement may happen in contractual agreements, the semantics of CDNI Footprint and Capabilities Advertisement refers to answering the following question: what exactly still needs to be advertised by the CDNI FCP? For instance, updates about temporal failures of part of a footprint can be useful information to convey via the CDNI FCI. Such information would provide updates on information previously agreed to in contracts between the participating CDNs. In other words, the CDNI FCI is a means for a dCDN to provide changes and updates regarding a footprint and/or capabilities that it has previously agreed to serve in a contract with a uCDN. Hence, server push and incremental encoding will be necessary techniques.

2.3. ALTO Background and Benefits

Application-Layer Traffic Optimization (ALTO) [RFC7285] defines an approach for conveying network-layer (topology) information to "guide" the resource provider selection process in distributed applications that can choose among several candidate resources providers to retrieve a given resource. Usually, it is assumed that an ALTO server conveys information that these applications cannot measure or have difficulty measuring themselves [RFC5693].

Originally, ALTO was motivated by optimizing cross-ISP traffic generated by peer-to-peer applications [RFC5693]. However, ALTO can also be used for improving the Request Routing in CDNs. In particular, Section 5 of [RFC7971] explicitly mentions ALTO as a candidate protocol to improve the selection of a CDN surrogate or origin.

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The following reasons make ALTO a suitable candidate protocol for dCDN selection as part of CDNI Request Routing and, in particular, for an FCI protocol:

* Application-Layer-oriented: ALTO is a protocol specifically designed to improve application- layer traffic (and application-layer connections among hosts on the Internet) by providing additional information to applications that these applications could not easily retrieve themselves. This matches the need of CDNI, where a uCDN wants to improve application-layer CDN request routing by using information (provided by a dCDN) that the uCDN could not easily obtain otherwise. Hence, ALTO can help a uCDN to select a proper dCDN by first providing dCDNs' capabilities as well as footprints (see Section 3) and then providing costs of surrogates in a dCDN by ALTO cost maps.

* Security: The identification between uCDNs and dCDNs is an important requirement (see Section 8). ALTO maps can be signed and hence provide inherent origin protection. Please see Section 15.1.2 of [RFC7285] for detailed protection strategies.

* RESTful design: The ALTO Protocol has undergone extensive revisions in order to provide a RESTful design regarding the client-server interaction specified by the protocol. It is flexible and extensible enough to handle existing and potential future data formats defined by CDNI. It can provide the consistent client-server interaction model for other existing CDNI interfaces or potential future extensions and therefore reduce the learning cost for both users and developers, although they are not in the scope of this document. A CDNI FCI interface based on ALTO would inherit this RESTful design. Please see Section 3.

* Error handling: The ALTO Protocol provides extensive error handling in the whole request and response process (see Section 8.5 of [RFC7285]). A CDNI FCI interface based on ALTO would inherit this extensive error-handling framework. Please see Section 5.

* Map Service: The semantics of an ALTO network map is an exact match for the needed information to convey a footprint by a dCDN, in particular, if such a footprint is being expressed by IP prefix ranges. Please see Section 4.

* Filtered Map Service: The ALTO map filtering service would allow a uCDN to query only for parts of an ALTO map. For example, the ALTO filtered property Map Service can enable a uCDN to query properties of a part of footprints efficiently. Please see Section 6.

* Server-initiated notifications and incremental updates: When the footprint or the capabilities of a dCDN change (i.e., unexpectedly from the perspective of a uCDN), server- initiated notifications would enable a dCDN to inform a uCDN about such changes directly. Consider the case where due to failure -- part of the footprint of the dCDN is not functioning, ie. the CDN cannot serve content to such clients with reasonable QoS. Without server- initiated notifications, the uCDN might still use a recent network and cost map from the dCDN and therefore redirect requests to the dCDN that it cannot serve. Similarly, the possibility for incremental updates would enable efficient conveyance of the aforementioned (or similar) status changes by the dCDN to the uCDN. The newest design of ALTO supports server-pushed incremental updates [RFC8895].

* Content availability on hosts: A dCDN might want to express CDN capabilities in terms of certain content types (e.g., codecs and/or formats, or content from certain content providers). ALTO Entity Property Map [RFC9240] would enable a dCDN to make such

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information available to a uCDN. This would enable a uCDN to assess whether a dCDN has the capabilities for a given type of content requested.

* Resource availability on hosts or links: The capabilities on links (e.g, maximum bandwidth) or caches (e.g. average load) might be useful information for a uCDN for optimized dCDN selection. For instance, if a uCDN receives a streaming request for content with a certain bitrate, it needs to know if it is likely that a dCDN can fulfill such stringent application-level requirements (i.e., can be expected to have enough consistent bandwidth) before it redirects the request. In general, if ALTO could convey such information via ALTO Entity Property Map [RFC9240], it would enable more sophisticated means for dCDN selection with ALTO. The ALTO Path Vector extension [ALTO-PATH-VECTOR] is designed to allow ALTO clients to query information such as capacity regions for a given set of flows.

3. CDNI Advertisement Service

The ALTO Protocol relies upon the ALTO information service framework, which consists of multiple services. All ALTO services are "provided through a common transport protocol; messaging structure and encoding; and transaction model" [RFC7285]. The ALTO Protocol specification defines multiple initial services, e.g., the ALTO Network Map Service and Cost Map Service.

This document defines a new ALTO service, called "CDNI Advertisement Service", which conveys JSON [RFC8259] objects of media type "application/alto-cdni+json". These JSON objects are used to transport BaseAdvertisementObject objects defined in [RFC8008]. This document specifies how to transport such BaseAdvertisementObject objects via the ALTO Protocol with the ALTO CDNI Advertisement Service. Similar to other ALTO services, this document defines the ALTO information resource for the CDNI Advertisement Service as follows.

Note that the encoding of BaseAdvertisementObject reuses the one defined in [RFC8008] and therefore also follows the recommendations of I-JSON (Internet JSON) [RFC7493], which is required by [RFC8008].

3.1. Media Type

The media type of the CDNI Advertisement resource is "application/alto-cdni*json" (see Section 7).

3.2. HTTP Method A CDNI Advertisement resource is requested using the HTTP GET method.

3.3. Accept Input Parameters

There are no applicable Accept Input parameters.

3.4. Capabilities

There are no applicable capabilities.

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3.5. Uses

The "uses" field MUST NOT appear unless the CDNI Advertisement resource depends on other ALTO information resources. If the CDNI Advertisement resource has dependent resources, the resource IDs of its dependent resources MUST be included into the "uses" field. This document only defines one potential dependent resource for the CDNI Advertisement resource. See Section 4 for details of when and how to use it. Future documents may extend the CDNI Advertisement resource and allow other dependent resources.

3.6. Response

The "meta" field of a CDNI Advertisement response MUST include the "vtag" field defined in Section 10.3 of [RFC7285]. This field provides the version of the retrieved CDNI FCI resource.

If a CDNI Advertisement response depends on other ALTO information resources, it MUST include the "dependent-vtags" field, whose value is an array to indicate the version tags of the resources used, where each resource is specified in "uses" of its Information Resource Directory (IRD) entry.

The data component of an ALTO CDNI Advertisement response is named "cdni-advertisement", which is a JSON object of type CDNIAdvertisementData:

object ( CDNIAdvertisementData cdni-advertisement; ) InfoResourceCDNIAdvertisement : ResponseEntityBase;

object ( BaseAdvertisementObject capabilities-with-footprints«0..*»; } CDNIAdvertisementData;

Specifically, a CDNIAdvertisementData object is a JSON object that includes only one property named "capabilities-with-footprints", whose value is an array of BaseAdvertisementObject objects. It provides capabilities with footprint restrictions for the uCDN to decide the dCDN selection. If the value of this property is an empty array, it means the corresponding dCDN cannot provide any mandatory-to-implement CDNI capabilities for any footprints.

The syntax and semantics of BaseAdvertisementObject are well defined in Section 5.1 of [RFC8008]. A BaseAdvertisementObject object includes multiple properties, including "capability- type", "capability-value", and "footprints", where "footprints" are defined in Section 4.2.2.2 of [RFC8006].

An equivalent specification in the ALTO-style notation (see Section 8.2 of [RFC7285]) creates a self- contained description of the BaseAdvertisementObject. As mentioned above, the normative specification of BaseAdvertisementObject is in [RFC8008].

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object ( JSONString capability-type; JSONValue capability-value; Footprint footprints«0..*»; ) BaseAdvertisementObject;

object { JSONString footprint-type; JSONString footprint-value<1..*>; ) Footprint;

For each BaseAdvertisementObject, the ALTO client MUST interpret "footprints" appearing multiple times as if they appeared only once. If "footprints" in a BaseAdvertisementObject is null or empty or does not appear, the ALTO client MUST understand that the capabilities in this BaseAdvertisementObject have the "global" coverage, i.e., the corresponding dCDN can provide them for any Request Routing source.

Note: Further optimization of BaseAdvertisementObjects to effectively provide the advertisement of capabilities with footprint restrictions is certainly possible. For example, these two examples below both describe that the dCDN can provide capabilities ["http/1.1", "https/1.1"] for the same footprints. However, the latter one is smaller in its size.

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EXAMPLE 1 {

"meta: es "cdni-advertisement": { "capabilities-with-footprints": |

( "capability-type": "FCI.DeliveryProtocol", "capability-value"': { "delivery-protocols": | hitit p belio ] k; “footprints: <Footprint objects> ] Vi { "capability-type": "FCI.DeliveryProtocol", "capability-value": { "delivery-protocols": [ hetens i be "footprints": [ <Footprint objects> ] } ] } } EXAMPLE 2 { "meta": {...}, "cdni-advertisement": { "capabilities-with-footprints": | "capability-type": "FCI.DeliveryProtocol", "capability-value": 4 "delivery-protocols": [ "https. DEED ] js "footprints": [ «Footprint objects» ] } ] } }

Since such optimizations are not required for the basic interconnection of CDNs, the specifics of such mechanisms are outside the scope of this document.

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This document only requires the ALTO server to provide the initial FCI-specific CDNI Payload Types defined in [RFC8008] as the mandatory-to-implement CDNI capabilities.

3.7. Examples

3.7.1. IRD

Below is the IRD of a simple, example ALTO server. The server provides both base ALTO information resources (e.g., network maps) and CDNI FCI-related information resources (e.g., CDNI Advertisement resources), demonstrating a single, integrated environment.

Specifically, the IRD announces nine information resources as follows:

* two network maps, * one CDNI Advertisement resource without dependency, * one CDNI Advertisement resource depending on a network map, e one filtered CDNI Advertisement resource to be defined in Section 5, * one property map including "cdni-capabilities" as its entity property, * one filtered property map including "cdni-capabilities" and "pid" as its entity properties, and * two update stream services: ° one for updating CDNI Advertisement resources, ° one for updating property maps

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GET /directory HTTP/1.1 Host: alto.example.com Accept: application/alto-directory+json, application/alto-error+json

HTTP/1.1 200 OK Content-Length: 3531 Content-Type: application/alto-directory+json

( "meta": ( "default-alto-network-map": "my-default-network-map"

"resources": { "my-default-network-map": ( "uri": "https://alto.example.com/networkmap", "media-type": "“application/alto-networkmap+json"

}

ny-eu-netmap": { "uri": "https://alto.example.com/myeunetmap", "media-type": "application/alto-networkmap*json"

je

"my-default-cdnifci"': { "uri": "https://alto.example.com/cdnifci", "media-type": "application/alto-cdni-json"

jm

"my-cdnifci-with-pid-footprints": ( "uri": "https://alto.example.com/networkcdnifci", "media-type": "“application/alto-cdni+json", "uses": [ "my-eu-netmap" ]

js

"my-filtered-cdnifci": { "uri": "https://alto.example.com/cdnifci/filtered", "media-type": "“application/alto-cdni+json", "accepts": "application/alto-cdnifilter-json"

"cdnifci-property-map": {

"uri": "https://alto.example.com/propmap/full/cdnifci",

"media-type": "application/alto-propmap-*json",

"uses": [ "my-default-cdni" ],

"capabilities": {

"mappings": { "ipv4": [ "my-default-cdni.cdni-capabilities" ], "ipv6": [ "my-default-cdni.cdni-capabilities" ], "countrycode": [ "my-default-cdni.cdni-capabilities" ],

"asn": [ "my-default-cdni.cdni-capabilities" ]

} } "filtered-cdnifci-property-map": { "uri": "https://alto.example.com/propmap/lookup/cdnifci-pid", "media-type": "“application/alto-propmap+json", "accepts": "application/alto-propmapparams-*json", "uses": [ "my-default-cdni", "my-default-network-map" ],

"capabilities": { "mappings": { "ipv4": [ "my-default-cdni.cdni-capabilities",

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"my-default-network-map.pid" ], "ipv6": [ "my-default-cdni.cdni-capabilities", "my-default-network-map.pid" ], "countrycode": [ "my-default-cdni.cdni-capabilities" ], "asn": [ "my-default-cdni.cdni-capabilities" ]

}

"update-my-cdni-fci"': { "uri": "https://alto.example.com/updates/cdnifci", "media-type": "text/event-stream", "accepts": "application/alto-updatestreamparams-*json", "uses": [ "my-default-network-map", "my-eu-netmap", "my-default-cdnifci', "my-filtered-cdnifci", "my-cdnifci-with-pid-footprints"

"capabilities": {

"incremental-change-media-types": { "my-default-network-map": "application/json-patch+json", "my-eu-netmap": "“application/json-patch+json", "my-default-cdnifci': "application/merge-patch-json,application/json-patch-*json", "my-filtered-cdnifci": "application/merge-patch-json,application/json-patch-*json", "my-cdnifci-with-pid-footprints": "application/merge-patch-json,application/json-patch-*json"

} yi “update-my-props": { "uri": "https://alto.example.com/updates/properties", "media-type": "text/event-stream", uses]

"cdnifci-property-map", "filtered-cdnifci-property-map"

"capabilities": { "incremental-change-media-types": { "cdnifci-property-map": "application/merge-patch-json,application/json-patch-*json", "filtered-cdnifci-property-map": "application/merge-patch-json,application/json-patch-*json"

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3.7.2. A Basic Example

This basic example demonstrates a simple CDNI Advertisement resource, which does not depend on other resources. There are three BaseAdvertisementObjects in this resource and these objects' capabilities are "http/1.1" delivery protocol, ["http/1.1", "https/1.1"] delivery protocol, and "https/ 1.1" acquisition protocol, respectively.

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GET /cdnifci HTTP/1.1 Host: alto.example.com Accept: application/alto-cdnit+json, application/alto-error+json

HTTP/1.1 200 OK Content-Length: 1411 Content-Type: application/alto-cdni+json

( "meta": ( "vtag": { "resource-id': "my-default-cdnifci", "tag': "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785" }

dni-advertisement": { "capabilities-with-footprints": [

( "capability-type": "FCI.DeliveryProtocol", "capability-value"': { "delivery-protocols": | antepi ] ae "footprints": [ "footprint-type": "ipv4cidr', "footprint-value": [ "192.0.2.0/24" ] js ( "footprint-type": "ipv6cidr', "footprint-value": [ "2001:db8::/32" ] } ] te "capability-type": "FCI.DeliveryProtocol", "capability-value"': { "delivery-protocols": | i ep ea dei A Sa e shtepi rii ] "footprints": [ "footprint-type": "ipv4cidr', "footprint-value": [ "198.51.100.0/24" ] ] }, { "capability-type": "FCI.AcquisitionProtocol", "capability-value"': { "acquisition-protocols": | NEED SUITS ra

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"footprints": [

"footprint-type": "ipv4cidr', "footprint-value": [ "203.0.113.0/24" ]

3.7.3. Incremental Updates

A benefit of using ALTO to provide CDNI Advertisement resources is that such resources can be updated using ALTO incremental updates [RFC8895]. Below is an example that also shows the benefit of having both JSON merge patch and JSON patch to encode updates.

At first, an ALTO client requests updates for "my-default-cdnifci", and the ALTO server returns the "control-uri" followed by the full CDNI Advertisement response. Then when there is a change in the "delivery-protocols" in that "http/1.1" is removed (from ["http/1.1", "https/1.1"] to only "https/ 1.1") due to maintenance of the "http/1.1" clusters, the ALTO server regenerates the new CDNI Advertisement resource and pushes the full replacement to the ALTO client. Later on, the ALTO server notifies the ALTO client that "192.0.2.0/24" is added into the "ipv4" footprint object for delivery protocol "https/1.1" by sending the change encoded by JSON patch to the ALTO client.

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POST /updates/cdnifci HTTP/1.1

Host: alto.example.com

Accept: text/event-stream, application/alto-error+json Content-Type: application/alto-updatestreamparams+json Content-Length: 94

"add": { "my-cdnifci-stream": { "resource-id': "my-default-cdnifci" i

}

HTTP/1.1 200 OK Connection: keep-alive Content-Type: text/event-stream

event: application/alto-updatestreamcontrol+json data: ("control-uri": data: "https://alto.example.com/updates/streams/3141592653589" }

event: application/alto-cdni+json, my-cdnifci-stream

data: { ... full CDNI Advertisement resource ... } event: application/alto-cdni+json, my-cdnifci-stream data:

data: "meta": {

data: "vtag":

data: "tag": "dasdfal0ce8b059740bddsfasd8eb1d47853716" data: }

data: },

data: "cdni-advertisement": {

data: "capabilities-with-footprints": |

data:

data: "capability-type": "FCI.DeliveryProtocol", data: "capability-value": {

data: "delivery-protocols": |

data: „hititp SA

data:

data: ho

data: "footprints": [

data: ( "footprint-type": "ipv4cidr",

data: "footprint-value": [ "203.0.113.0/24" ] data: )

data: ]

data:

data: ( ... other CDNI advertisement object ... } data: ]

data: )

data: )

event: application/json-patch*json,my-cdnifci-stream data:

data: ( "op": "replace",

data: "path": "/meta/vtag/tag",

data: "value": "a10ce8b059740b0b2e3f8eb1d4785acd42231bfe"

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data: X

data: ( "op': "add",

data: "path": "/cdni-advertisement/capabilities-with-footprints /0/footprints/0/footprint-value/-",

data: "value": "192.0.2.0/24"

data: )

data: |]

4. CDNI Advertisement Service Using ALTO Network Map

4.1. Network Map Footprint Type: altopid

The ALTO Protocol defines a concept called Provider-defined Identifier (PID) to represent a group of IPv4 or IPv6 addresses to which can be applied the same management policy. The PID is an

alternative to the predefined CDNI footprint types (i.e., "ipv4cidr", "ipv6cidr", "asn", and "countrycode").

To leverage this concept, this document defines a new CDNI Footprint Type called "altopid". A CDNI Advertisement resource can depend on an ALTO network map resource and use "altopid" footprints to compress its CDNI Footprint Payload.

Specifically, the "altopid" footprint type indicates that the corresponding footprint value is a list of PIDNames as defined in [RFC7285]. These PIDNames are references of PIDs in a network map resource. Hence a CDNI Advertisement resource using "altopid" footprints depends on a network map. For such a CDNI Advertisement resource, the resource ID of its dependent network map MUST be included in the "uses" field of its IRD entry, and the "dependent-vtags" field with a reference to this network map MUST be included in its response (see the example in Section 4.2.2).

4.2. Examples

The following examples use the same IRD given in Section 3.7.1.

4.2.1. ALTO Network Map for CDNI Advertisements

Below provides a sample network map whose resource ID is "my-eu-netmap". This map is referenced by the CDNI Advertisement example in Section 4.2.2.

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GET /myeunetmap HTTP/1.1 Host: alto.example.com Accept: application/alto-networkmap+json, application/alto-error+json

HTTP/1.1 200 OK Content-Length: 344 Content-Type: application/alto-networkmap+json

( "meta": l "vtag" [ { "resource-id": "my-eu-netmap Bats CE: "3ee2cb7e8363d91ab71b9b34cbf764436315542e" ] "network-map" : { "south-france" : { "ipv4": [ "192.0.2.0/24", "198.51.100.0/25" ], "ipv6": [ "2001:db8::/32" ] "germany": "ipv4": [ "203.0.113.0/24" ] } }

4.2.2. ALTO PID Footprints in CDNI Advertisements

This example shows a CDNI Advertisement resource that depends on a network map described in Section 4.2.1.

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GET /networkcdnifci HTTP/1.1 Host: alto.example.com

July 2022

Accept: application/alto-cdnit+json, application/alto-error+json

HTTP/1.1 200 OK Content-Length: 736 Content-Type: application/alto-cdni+json

( "meta": ( "dependent-vtags": | "resource-id': "my-eu-netmap", "tag': "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" ] le "cdni-advertisement": { "capabilities-with-footprints": | ( "capability-type": "FCI.DeliveryProtocol", "capability-value": | "https/1.1" |], "footprints": [ ( "footprint-type": "altopid", "footprint-value": [ "south-france" ] ] 15 ( "capability-type": "FCI.AcquisitionProtocol", "capability-value": [ "https/1.1" ], "footprints": [ { "footprint-type": "altopid", "footprint-value": [ "germany", "south-france" ] } ] } i

4.2.3. Incremental Updates

]

In this example, the ALTO client is interested in changes of "my-cdnifci-with-pid-footprints" and its dependent network map "my-eu-netmap". Considering two changes, the first one is to change footprints of the "https/1.1" delivery protocol capability, and the second one is to remove the "south-france" PID from the footprints of the "https/1.1" acquisition protocol capability.

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POST /updates/cdnifci HTTP/1.1

Host: alto.example.com

Accept: text/event-stream, application/alto-error+json Content-Type: application/alto-updatestreamparams+json Content-Length: 185

"add": { "my-eu-netmap-stream": { "resource-id': "my-eu-netmap"

"my-netmap-cdnifci-stream': { "resource-id': "my-cdnifci-with-pid-footprints"

} }

HTTP/1.1 200 OK Connection: keep-alive Content-Type: text/event-stream

event: application/alto-updatestreamcontrol+json data: ("control-uri": data: "https://alto.example.com/updates/streams/3141592653590" }

event: application/alto-networkmap+json, my-eu-netmap-stream

data: ( ... full Network Map of my-eu-netmap

event: application/alto-cdnifci+json,my-netmap-cdnifci-stream data: ( ... full CDNI Advertisement resource ... )

event: application/json-patch-*json,my-netmap-cdnifci-stream data:

data: { "op": "replace",

data: "path": "/meta/vtag/tag",

data: "value": "dasdfa10ce8b059740bddsfasd8eb1d47853716" data: M

data: (op ad di,

data: „pată;

data: "/cdni-advertisement/capabilities-with-footprints /0/footprints/0/footprint-value/-",

data: "value": "germany"

data: )

data: ]

event: application/json-patch-*json,my-netmap-cdnifci-stream data:

data: ( "op": "replace",

data: "path": "/meta/vtag/tag",

data: "value": "a10ce8b059740b0b2e3f8eb1d4785acd42231bfe" data: js

data: { "op": "remove",

data: spat

data: "/cdni-advertisement/capabilities-with-footprints /1/footprints/0/footprint-value/1"

data: )

data: ]

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5. Filtered CDNI Advertisement Using CDNI Capabilities

Sections 3 and 4 describe the CDNI Advertisement Service that can be used to enable a uCDN to get capabilities with footprint restrictions from dCDNs. However, since always getting full CDNI Advertisement resources from dCDNs is inefficient, this document introduces a new service named "Filtered CDNI Advertisement Service" to allow a client to filter a CDNI Advertisement resource using a client-given set of CDNI capabilities. For each entry of the CDNI Advertisement response, an entry will only be returned to the client if it contains at least one of the client-given CDNI capabilities. The relationship between a filtered CDNI Advertisement resource and a CDNI Advertisement resource is similar to the relationship between a filtered network/cost map and a network/cost map.

5.1. Media Type

A filtered CDNI Advertisement resource uses the same media type defined for the CDNI Advertisement resource in Section 3.1: "application/alto-cdni*json".

5.2. HTTP Method A filtered CDNI Advertisement resource is requested using the HTTP POST method.

5.3. Accept Input Parameters

The input parameters for a filtered CDNI Advertisement resource are supplied in the entity body ofthe POST request. This document specifies the input parameters with a data format indicated by the media type "application/alto-cdnifilter*json", which is a JSON object of type RegFilteredCDNIAdvertisement where:

object ( JSONString capability-type; JSONValue capability-value; } CDNICapability;

object (

CDNICapability cdni-capabilities«0..*»; ) RegFilteredCDNIAdvertisement;

with fields:

capability-type: The same as Base Advertisement Object's "capability-type" defined in Section 5.1 of [RFC8008].

capability-value: Thesame as Base Advertisement Object's "capability-value" defined in Section 5.1 of [RFC8008].

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cdni-capabilities: A list of CDNI capabilities defined in Section 5.1 of [RFC8008] for which footprints are to be returned. If this list is empty, the ALTO server MUST interpret it as a request for the full CDNI Advertisement resource. The ALTO server MUST interpret entries appearing in this list multiple times as if they appeared only once. If the ALTO server does not define any footprints for a CDNI capability, it MUST omit this capability from the response.

5.4. Capabilities

There are no applicable capabilities.

5.5. Uses

The same rules as for the "uses" field of the CDNI Advertisement resource apply (see Section 3.5).

5.6. Response

If the request is invalid, the response MUST indicate an error using ALTO Protocol error handling specified in Section 8.5 of [RFC7285].

Specifically, a filtered CDNI Advertisement request is invalid if:

* the value of "capability-type" is null; e the value of "capability-value" is null; or e the value of "capability-value" is inconsistent with "capability-type".

When a request is invalid, the ALTO server MUST return an "E INVALID FIELD. VALUF" error defined in Section 8.5.2 of [RFC7285], and the "value" field of the error message SHOULD indicate this CDNI capability.

The ALTO server returns a filtered CDNI Advertisement resource for a valid request. The format of a filtered CDNI Advertisement resource is the same as a full CDNI Advertisement resource (see Section 3.6).

The returned filtered CDNI Advertisement resource MUST contain all the BaseAdvertisementObject objects satisfying the following condition: the CDNI capability object of each included BaseAdvertisementObject object MUST follow two constraints:

* The "cdni-capabilities" field of the input includes a CDNI capability object X having the same "capability-type" as it.

* All the mandatory properties in its "capability-value" is a superset of mandatory properties in "capability-value" of X semantically.

See Section 5.7.1 for a concrete example.

The version tag included in the "vtag" field of the response MUST correspond to the full CDNI Advertisement resource from which the filtered CDNI Advertisement resource is provided. This ensures that a single, canonical version tag is used independently of any filtering that is requested by an ALTO client.

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5.7. Examples

The following examples use the same IRD example as in Section 3.7.1.

5.7.1. A Basic Example

This example filters the full CDNI Advertisement resource in Section 3.7.2 by selecting only the "http/1.1" delivery protocol capability. Only the second BaseAdvertisementObject in the full resource will be returned because the second object's capability is "http/1.1" and "https/1.1" delivery protocols, which is the superset of "https/1.1" delivery protocol.

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POST /cdnifci/filtered HTTP/1.1

Host: alto.example.com

Accept: application/alto-cdni+json Content-Type: application/cdnifilter+json Content-Length: 176

"cdni-capabilities": |

"capability-type": "FCI.DeliveryProtocol", "capability-value": "delivery-protocols": [ "https/1.1" ] } i ] }

HTTP/1.1 200 OK Content-Length: 570 Content-Type: application/alto-cdni+json

( "meta": ( "vtag": { "resource-id': "my-filtered-cdnifci", "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785" ya "cdni-advertisement": { "capabilities-with-footprints": [ { "capability-type": "FCI.DeliveryProtocol", "capability-value": { "delivery-protocols": [ “https i aia heto Neal ] ign "Footprints: | "footprint-type": "ipv4cidr', "footprint-value": [ "198.51.100.0/24" ] } ] } ] } }

5.7.2. Incremental Updates

In this example, the ALTO client only cares about the updates of one advertisement object for delivery protocol capability whose value includes "https/1.1". Thus, it adds its limitation of capabilities in "input" field of the POST request.

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POST /updates/cdnifci HTTP/1.1

Host: fcialtoupdate.example.com

Accept: text/event-stream, application/alto-error+json Content-Type: application/alto-updatestreamparams+json Content-Length: 346

"add": { "my-filtered-fci-stream": { "resource-id': "my-filtered-cdnifci', SITYD pet ET

"cdni-capabilities": |

"capability-type": "FCI.DeliveryProtocol", "capability-value"': 4 "delivery-protocols": | "https/1.1" ]

HTTP/1.1 200 OK Connection: keep-alive Content-Type: text/event-stream

event: application/alto-updatestreamcontrol+json data: ("control-uri": data: "https://alto.example.com/updates/streams/3141592653590" }

event: application/alto-cdni-json,my-filtered-fci-stream data: ( ... filtered CDNI Advertisement resource ... )

event: application/json-patch*json,my-filtered-fci-stream

data:

data: {

data: "op": "replace",

data: "path": "/meta/vtag/tag",

data: "value": "a10ce8b059740b0b2e3f8eb1d4785acd42231bfe" data: je

data: ( "op': "add",

data: "path":

data: "/cdni-advertisement/capabilities-with-footprints /0/footprints/0/footprint-value/-",

data: "value": "192.0.2.0/24"

data: )

data i]

6. Query Footprint Properties Using ALTO Property Map Service

Besides the requirement of retrieving footprints of given capabilities, another common requirement for uCDN is to query CDNI capabilities of given footprints.

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Considering each footprint as an entity with properties including CDNI capabilities, a natural way to satisfy this requirement is to use the ALTO property map as defined in [RFC9240]. This section describes how ALTO clients look up properties for individual footprints. First, it describes how to represent footprint objects as entities in the ALTO property map. Then it describes how to represent footprint capabilities as entity properties in the ALTO property map. Finally, it provides examples of the full property map and the filtered property map supporting CDNI capabilities, and their incremental updates.

6.1. Representing Footprint Objects as Property Map Entities

A footprint object has two properties: "footprint-type" and "footprint-value". A "footprint-value" is an array of footprint values conforming to the specification associated with the registered footprint type ("ipv4cidr", "ipv6cidr", "asn", "countrycode", and "altopid"). Considering each ALTO entity defined in [RFC9240] also has two properties: entity domain type and domain-specific identifier, a straightforward approach to represent a footprint as an ALTO entity is to represent its "footprint-type" as an entity domain type, and its footprint value as a domain-specific

identifier. Each existing footprint type can be represented as an entity domain type as follows:

* According to [RFC9240], "ipv4" and "ipv6" are two predefined entity domain types, which can be used to represent "ipv4cidr" and "ipv6cidr" footprints respectively. Note that both "ipv4" and "ipv6" domains can include not only hierarchical addresses but also individual addresses. Therefore, a "ipv4cidr" or "ipv6cidr" footprint with the longest prefix can also be represented by an individual address entity. When the uCDN receives a property map with individual addresses in an "ipv4" or "ipv6" domain, it can translate them as corresponding "ipv4cidr" or "ipv6cidr" footprints with the longest prefix.

* "pid" is also a predefined entity domain type, which can be used to represent "altopid" footprints. Note that "pid" is a resource-specific entity domain. To represent an "altopid" footprint, the specifying information resource of the corresponding "pid" entity domain MUST be the dependent network map used by the CDNI Advertisement resource providing this "altopid" footprint.

* However, no existing entity domain type can represent "asn" and "countrycode" footprints. To represent footprint-type "asn" and "countrycode", this document registers two new entity domains in Section 7 in addition to the ones in [RFC9240].

Here is an example of representing a footprint object of "ipv4cidr" type as a set of "ipv4" entities in the ALTO property map. The representation of the footprint object of "ipv6cidr" type is similar.

{ "footprint-type": "ipv4cidr', "footprint-value": ["192.0.2.0/24", "198.51.100.0/24"] ) --» "ipv4:192.0.2.0/24", "ipv4:198.51.100.0/24"

And here is an example of the corresponding footprint object of "ipv4cidr" type represented by an individual address in an "ipv4" domain in the ALTO property map. The translation of the entities in an "ipv6" domain is similar.

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"ipv4:203.0.113.100" --> { "footprint-type": "ipv4cidr', "footprint-value": ["203.0.113.100/32"]

6.1.1. ASN Domain

The ASN domain associates property values with Autonomous Systems in the Internet.

6.1.1.1. Entity Domain Type The entity domain type of the ASN domain is "asn" (in lowercase).

6.1.1.2. Domain-Specific Entity Identifiers

The entity identifier of an entity in an ASN domain MUST be encoded as a string consisting of the characters "as" (in lowercase) followed by the ASN [RFC6793] as a decimal number without leading zeros.

6.1.1.3. Hierarchy and Inheritance There is no hierarchy or inheritance for properties associated with ASN.

6.1.2. COUNTRYCODE Domain The COUNTRYCODE domain associates property values with countries.

6.1.2.1. Entity Domain Type The entity domain type of the COUNTRYCODE domain is "countrycode" (in lowercase).

6.1.2.2. Domain-Specific Entity Identifiers

The entity id