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RFC 9241	CDNI FCI Using ALTO	July 2022
Seedorf, et al.	Standards Track	[Page]

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 bothFCI semantics and ALTO. Hence, this document starts with a non-normative reviewof 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 followingabbreviations:¶

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 semanticsof CDNI FCI, provides guidance on what footprint and capabilities mean in a CDNIcontext, and specifies the requirements on the CDNI FCI transport protocol. Thedefinitions in[RFC8008] depend on[RFC8006]. Below is a non-normativereview of key related points of[RFC8008] and[RFC8006]. For detailedinformation and normative specification, the reader should refer to these twoRFCs.¶

Multiple types of mandatory-to-implement footprints (i.e., "ipv4cidr", "ipv6cidr", "asn",and "countrycode") are defined in[RFC8006]. A "set of IP prefixes" cancontain both full IP addresses (i.e., a /32 for IPv4 or a /128 for IPv6) andIP prefixes with an arbitrary prefix length. There must also be support formultiple IP address versions, i.e., IPv4 and IPv6, in such a footprint.¶
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 CDNIMetadata. They are required in all cases and, therefore, considered asmandatory-to-implement capabilities for all CDNI FCI implementations.¶
Footprint and capabilities are defined together and cannot be interpretedindependently from each other. Specifically,[RFC8008] integrates footprintand capabilities with an approach of "capabilities with footprintrestrictions", by expressing capabilities on a per footprint basis.¶
Specifically, for all mandatory-to-implement footprint types, footprints canbe viewed as constraints for delegating requests to a dCDN: a dCDN footprintadvertisement tells the uCDN the limitations for delegating a request to thedCDN. For IP prefixes or Autonomous System Numbers (ASNs), the footprint signals to the uCDN that itshould consider the dCDN a candidate only if the IP address of the RequestRouting source falls within the prefix set or ASN, respectively. The CDNIspecifications do not define how a given uCDN determines what address rangesare in a particular ASN. Similarly, for country codes, a uCDN should onlyconsider the dCDN a candidate if it covers the country of the Request Routingsource. The CDNI specifications do not define how a given uCDN determines thecountry of the Request Routing source. Different types of footprintconstraints can be combined together to narrow the dCDN candidacy, i.e., theuCDN should consider the dCDN a candidate only if the request routing sourcesatisfies all the types of footprint constraints in the advertisement.¶
Given that a large part of Footprint and Capabilities Advertisement mayhappen in contractual agreements, the semantics of CDNI Footprint andCapabilities Advertisement refers to answering the following question: whatexactly still needs to be advertised by the CDNI FCI? For instance, updatesabout temporal failures of part of a footprint can be useful information toconvey via the CDNI FCI. Such information would provide updates on informationpreviously agreed to in contracts between the participating CDNs. In other words,the CDNI FCI is a means for a dCDN to provide changes and updatesregarding a footprint and/or capabilities that it has previously agreed to serve ina contract with a uCDN. Hence, server push and incrementalencoding will be necessary techniques.¶

2.3.ALTO Background and Benefits

Application-Layer Traffic Optimization (ALTO)[RFC7285] defines an approachfor conveying network-layer (topology) information to "guide" the resourceprovider selection process in distributed applications that can choose amongseveral candidate resources providers to retrieve a given resource. Usually, itis assumed that an ALTO server conveys information that these applicationscannot 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 theRequest Routing in CDNs. In particular,Section 5 of [RFC7971]explicitly mentions ALTO as a candidate protocol to improve the selection of aCDN surrogate or origin.¶

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

Application-Layer-oriented: ALTO is a protocol specifically designed toimprove application-layer traffic (and application-layer connections amonghosts on the Internet) by providing additional information to applicationsthat these applications could not easily retrieve themselves. This matches theneed of CDNI, where a uCDN wants to improve application-layer CDN request routing byusing information (provided by a dCDN) that the uCDN could not easily obtainotherwise. Hence, ALTO can help a uCDN to select a proper dCDN by firstproviding dCDNs' capabilities as well as footprints (seeSection 3) andthen providing costs of surrogates in a dCDN by ALTO cost maps.¶
Security: The identification between uCDNs and dCDNs is an importantrequirement (seeSection 8). ALTO maps can be signed and hence provideinherent origin protection. Please seeSection 15.1.2 of [RFC7285] fordetailed protection strategies.¶
RESTful design: The ALTO Protocol has undergone extensive revisions in orderto provide a RESTful design regarding the client-server interaction specifiedby the protocol. It is flexible and extensible enough to handle existing andpotential future data formats defined by CDNI. It can provide the consistentclient-server interaction model for other existing CDNI interfaces orpotential future extensions and therefore reduce the learning cost for bothusers and developers, although they are not in the scope of thisdocument. A CDNI FCI interface based on ALTO would inherit this RESTfuldesign. Please seeSection 3.¶
Error handling: The ALTO Protocol provides extensive error handling in thewhole request and response process (seeSection 8.5 of [RFC7285]). A CDNIFCI interface based on ALTO would inherit this extensive error-handlingframework. Please seeSection 5.¶
Map Service: The semantics of an ALTO network map is an exact match for theneeded information to convey a footprint by a dCDN, inparticular, if such a footprint is being expressed by IP prefixranges. Please seeSection 4.¶
Filtered Map Service: The ALTO map filtering service would allow a uCDN toquery only for parts of an ALTO map. For example, the ALTO filtered propertyMap Service can enable a uCDN to query properties of a part of footprintsefficiently. Please seeSection 6.¶
Server-initiated notifications and incremental updates: When the footprint orthe capabilities of a dCDN change (i.e., unexpectedly from the perspective ofa uCDN), server-initiated notifications would enable a dCDN to inform a uCDNabout such changes directly. Consider the case where -- due to failure -- partof the footprint of the dCDN is not functioning, i.e., the CDN cannot servecontent to such clients with reasonable QoS. Without server-initiatednotifications, the uCDN might still use a recent network and cost map from thedCDN and therefore redirect requests to the dCDN that it cannot serve.Similarly, the possibility for incremental updates would enable efficientconveyance of the aforementioned (or similar) status changes by the dCDN tothe uCDN. The newest design of ALTO supports server-pushed incremental updates[RFC8895].¶
Content availability on hosts: A dCDN might want to express CDN capabilitiesin terms of certain content types (e.g., codecs and/or formats, or content fromcertain content providers). ALTO Entity Property Map[RFC9240] would enable a dCDN to make suchinformation available to a uCDN. This would enable a uCDN to assess whethera 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 informationfor a uCDN for optimized dCDN selection. For instance, if a uCDN receives astreaming request for content with a certain bitrate, it needs to know if itis likely that a dCDN can fulfill such stringent application-levelrequirements (i.e., can be expected to have enough consistent bandwidth)before it redirects the request. In general, if ALTO could convey suchinformation via ALTO Entity Property Map[RFC9240],it would enable more sophisticated means for dCDN selection with ALTO. The ALTOPath Vector extension[ALTO-PATH-VECTOR] is designed to allow ALTOclients to query information such as capacity regions for a given set offlows.¶

3.CDNI Advertisement Service

The ALTO Protocol relies upon the ALTO information service framework, whichconsists of multiple services. All ALTO services are "provided through a commontransport protocol; messaging structure and encoding; and transactionmodel"[RFC7285]. The ALTO Protocol specification defines multipleinitial 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". TheseJSON objects are used to transport BaseAdvertisementObject objects defined in[RFC8008]. This document specifies how to transport suchBaseAdvertisementObject objects via the ALTO Protocol with the ALTO CDNIAdvertisement Service. Similar to other ALTO services, this document definesthe ALTO information resource for the CDNI Advertisement Service as follows.¶

Note that the encoding of BaseAdvertisementObject reuses the onedefined 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" (seeSection 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.¶

3.5.Uses

The "uses" fieldMUST NOT appear unless the CDNI Advertisement resourcedepends on other ALTO information resources. If the CDNI Advertisementresource has dependent resources, the resource IDs of itsdependent resourcesMUST be included into the "uses" field. Thisdocument only defines one potential dependent resource for the CDNIAdvertisement resource. SeeSection 4 for detailsof when and how to use it. Future documents may extend the CDNI Advertisementresource and allow other dependent resources.¶

3.6.Response

The "meta" field of a CDNI Advertisement responseMUST include the "vtag"field defined inSection 10.3 of [RFC7285]. Thisfield provides the version of the retrieved CDNI FCI resource.¶

If a CDNI Advertisement response depends on other ALTO information resources, itMUST include the "dependent-vtags" field, whose value is an array to indicatethe 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 includesonly one property named "capabilities-with-footprints", whose value is an arrayof BaseAdvertisementObject objects. It provides capabilities with footprintrestrictions for the uCDN to decide the dCDN selection. If the value of thisproperty is an empty array, it means the corresponding dCDN cannot provide anymandatory-to-implement CDNI capabilities for any footprints.¶

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

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

    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 clientMUST interpret "footprints"appearing multiple times as if they appeared only once. If "footprints" in aBaseAdvertisementObject is null or empty or does not appear, the ALTO clientMUSTunderstand that the capabilities in this BaseAdvertisementObject have the"global" coverage, i.e., the corresponding dCDN can provide them for anyRequest Routing source.¶

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

EXAMPLE 1    {      "meta": {...},      "cdni-advertisement": {        "capabilities-with-footprints": [          {            "capability-type": "FCI.DeliveryProtocol",            "capability-value": {              "delivery-protocols": [                "http/1.1"              ]            },            "footprints": [              <Footprint objects>            ]          },          {            "capability-type": "FCI.DeliveryProtocol",            "capability-value": {              "delivery-protocols": [                "https/1.1"              ]            },            "footprints": [              <Footprint objects>            ]          }        ]      }    }

EXAMPLE 2    {      "meta": {...},      "cdni-advertisement": {        "capabilities-with-footprints": [          {            "capability-type": "FCI.DeliveryProtocol",            "capability-value": {              "delivery-protocols": [                "https/1.1",                "http/1.1"              ]            },            "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.¶

This document only requires the ALTO server to provide the initial FCI-specificCDNI Payload Types defined in[RFC8008] as the mandatory-to-implement CDNIcapabilities.¶

3.7.Examples

3.7.1.IRD

Below is the IRD of a simple, example ALTOserver. The server provides both base ALTO information resources (e.g., networkmaps) and CDNI FCI-related information resources (e.g., CDNI Advertisementresources), 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,¶
one filtered CDNI Advertisement resource to be defined inSection 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¶

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

3.7.2.A Basic Example

This basic example demonstrates a simple CDNI Advertisement resource, which doesnot depend on other resources. There are three BaseAdvertisementObjects in thisresource 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.¶

  GET /cdnifci HTTP/1.1  Host: alto.example.com  Accept: application/alto-cdni+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"      }    },    "cdni-advertisement": {      "capabilities-with-footprints": [        {          "capability-type": "FCI.DeliveryProtocol",          "capability-value": {            "delivery-protocols": [              "http/1.1"            ]          },          "footprints": [            {              "footprint-type": "ipv4cidr",              "footprint-value": [ "192.0.2.0/24" ]            },            {              "footprint-type": "ipv6cidr",              "footprint-value": [ "2001:db8::/32" ]            }          ]        },        {          "capability-type": "FCI.DeliveryProtocol",          "capability-value": {            "delivery-protocols": [              "https/1.1",              "http/1.1"            ]          },          "footprints": [            {              "footprint-type": "ipv4cidr",              "footprint-value": [ "198.51.100.0/24" ]            }          ]        },        {          "capability-type": "FCI.AcquisitionProtocol",          "capability-value": {            "acquisition-protocols": [              "https/1.1"            ]          },          "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 suchresources can be updated using ALTO incremental updates[RFC8895]. Below isan example that also shows the benefit of having both JSON merge patch and JSONpatch to encode updates.¶

At first, an ALTO client requests updates for "my-default-cdnifci", and the ALTOserver returns the "control-uri" followed by the full CDNI Advertisementresponse. 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 ofthe "http/1.1" clusters, the ALTO server regenerates the new CDNI Advertisementresource and pushes the full replacement to the ALTO client. Later on, the ALTOserver 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 encodedby JSON patch to the ALTO client.¶

 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"     }   } } 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": "dasdfa10ce8b059740bddsfasd8eb1d47853716" data:     } data:   }, data:   "cdni-advertisement": { data:     "capabilities-with-footprints": [ data:       { data:         "capability-type": "FCI.DeliveryProtocol", data:         "capability-value": { data:           "delivery-protocols": [ data:             "https/1.1" data:           ] data:         }, 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" data:   }, 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) torepresent a group of IPv4 or IPv6 addresses to which can be applied the samemanagement policy. The PID is an alternative to the predefined CDNI footprinttypes (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 mapresource and use "altopid" footprints to compress its CDNI Footprint Payload.¶

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

4.2.Examples

The following examples use the same IRD given inSection 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". Thismap is referenced by the CDNI Advertisement example inSection 4.2.2.¶

 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": {     "vtag": [       { "resource-id": "my-eu-netmap",         "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"       }     ]   },   "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 mapdescribed inSection 4.2.1.¶

 GET /networkcdnifci HTTP/1.1 Host: alto.example.com Accept: application/alto-cdni+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"       }     ]   },   "cdni-advertisement": {     "capabilities-with-footprints": [       { "capability-type": "FCI.DeliveryProtocol",         "capability-value": [ "https/1.1" ],         "footprints": [           { "footprint-type": "altopid",             "footprint-value": [ "south-france" ]           }         ]       },       { "capability-type": "FCI.AcquisitionProtocol",         "capability-value": [ "https/1.1" ],         "footprints": [           { "footprint-type": "altopid",             "footprint-value": [ "germany", "south-france" ]           }         ]       }     ]   } }

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 protocolcapability.¶

  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:   },  data:   { "op": "add",  data:     "path":  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:   },  data:   { "op": "remove",  data:     "path":  data:     "/cdni-advertisement/capabilities-with-footprints  /1/footprints/0/footprint-value/1"  data:   }  data: ]

5.Filtered CDNI Advertisement Using CDNI Capabilities

Sections3 and4 describe the CDNI Advertisement Servicethat can be used to enable a uCDN to get capabilities with footprintrestrictions from dCDNs. However, since always getting full CDNI Advertisementresources from dCDNs is inefficient, this document introduces a new servicenamed "Filtered CDNI Advertisement Service" to allow a client to filter a CDNIAdvertisement resource using a client-given set of CDNI capabilities. For eachentry of the CDNI Advertisement response, an entry will only be returned to theclient if it contains at least one of the client-given CDNI capabilities. Therelationship between a filtered CDNI Advertisement resource and a CDNIAdvertisement resource is similar to the relationship between a filterednetwork/cost map and a network/cost map.¶

5.1.Media Type

A filtered CDNI Advertisement resource uses the same media type defined for theCDNI Advertisement resource inSection 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 inthe entity body of the POST request. This document specifies the inputparameters with a data format indicated by the media type"application/alto-cdnifilter+json", which is a JSON object of typeReqFilteredCDNIAdvertisement where:¶

   object {       JSONString capability-type;       JSONValue capability-value;   } CDNICapability;   object {       CDNICapability cdni-capabilities<0..*>;   } ReqFilteredCDNIAdvertisement;

with fields:¶

capability-type:: The same as Base Advertisement Object's "capability-type" defined inSection 5.1 of [RFC8008].¶
capability-value:: The same as Base Advertisement Object's "capability-value" defined inSection 5.1 of [RFC8008].¶
cdni-capabilities:: A list of CDNI capabilities defined inSection 5.1 of [RFC8008] for whichfootprints are to be returned. If this list is empty, the ALTOserverMUST interpret it as a request for the full CDNI Advertisementresource. The ALTO serverMUST interpret entries appearing in this list multipletimes as if they appeared only once. If the ALTO server does not define anyfootprints for a CDNI capability, itMUST omit this capability from theresponse.¶

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 (seeSection 3.5).¶

5.6.Response

If the request is invalid, the responseMUST indicate an error using ALTOProtocol error handling specified inSection 8.5 of [RFC7285].¶

Specifically, a filtered CDNI Advertisement request is invalid if:¶

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

When a request is invalid, the ALTO serverMUST return an"E_INVALID_FIELD_VALUE" error defined inSection 8.5.2 of [RFC7285], and the"value" field of the error messageSHOULD indicate this CDNI capability.¶

The ALTO server returns a filtered CDNI Advertisement resource for a validrequest. The format of a filtered CDNI Advertisement resource is the same as afull CDNI Advertisement resource (seeSection 3.6).¶

The returned filtered CDNI Advertisement resourceMUST contain all theBaseAdvertisementObject objects satisfying the following condition: the CDNIcapability object of each included BaseAdvertisementObject objectMUST followtwo constraints:¶

The "cdni-capabilities" field of the input includes a CDNI capability objectX having the same "capability-type" as it.¶
All the mandatory properties in its "capability-value" is a superset ofmandatory properties in "capability-value" of X semantically.¶

SeeSection 5.7.1 for a concrete example.¶

The version tag included in the "vtag" field of the responseMUST correspond tothe full CDNI Advertisement resource from which the filtered CDNI Advertisementresource is provided. This ensures that a single, canonical version tag is usedindependently of any filtering that is requested by an ALTO client.¶

5.7.Examples

The following examples use the same IRD example as inSection 3.7.1.¶

5.7.1.A Basic Example

This example filters the full CDNI Advertisement resource inSection 3.7.2 by selecting only the "http/1.1" delivery protocolcapability. Only the second BaseAdvertisementObject in the full resource willbe 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.¶

  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" ]        }      }    ]  }  HTTP/1.1 200 OK  Content-Length: 570  Content-Type: application/alto-cdni+json  {    "meta": {      "vtag": {        "resource-id": "my-filtered-cdnifci",        "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785"      }    },    "cdni-advertisement": {      "capabilities-with-footprints": [        {          "capability-type": "FCI.DeliveryProtocol",          "capability-value": {            "delivery-protocols": [              "https/1.1",              "http/1.1"            ]          },          "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 oneadvertisement object for delivery protocol capability whose value includes"https/1.1". Thus, it adds its limitation of capabilities in "input" field of thePOST request.¶

  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",        "input": {          "cdni-capabilities": [            {              "capability-type": "FCI.DeliveryProtocol",              "capability-value": {                "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:   },  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: ]

6.Query Footprint Properties Using ALTO Property Map Service

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

Considering each footprint as an entity with properties including CDNIcapabilities, a natural way to satisfy this requirement is to use the ALTOproperty map as defined in[RFC9240]. This sectiondescribes how ALTO clients look up properties for individual footprints. First,it describes how to represent footprint objects as entities in the ALTO propertymap. Then it describes how to represent footprint capabilities as entityproperties in the ALTO property map. Finally, it provides examples of the fullproperty map and the filtered property map supporting CDNI capabilities, andtheir 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 specificationassociated with the registered footprint type ("ipv4cidr", "ipv6cidr", "asn","countrycode", and "altopid"). Considering each ALTO entity defined in[RFC9240] also has two properties: entity domain typeand domain-specific identifier, a straightforward approach to represent afootprint as an ALTO entity is to represent its "footprint-type" as an entitydomain type, and its footprint value as a domain-specific identifier.¶

Each existing footprint type can be represented as an entity domain type asfollows:¶

According to[RFC9240], "ipv4" and "ipv6" are twopredefined entity domain types, which can be used to represent "ipv4cidr" and"ipv6cidr" footprints respectively. Note that both "ipv4" and "ipv6" domainscan include not only hierarchical addresses but also individual addresses.Therefore, a "ipv4cidr" or "ipv6cidr" footprint with the longest prefix canalso be represented by an individual address entity. When the uCDN receives aproperty map with individual addresses in an "ipv4" or "ipv6" domain, it cantranslate them as corresponding "ipv4cidr" or "ipv6cidr" footprints with thelongest 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. Torepresent an "altopid" footprint, the specifying information resource of thecorresponding "pid" entity domainMUST be the dependent network map used bythe 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 documentregisters two new entity domains inSection 7 in addition to the ones in[RFC9240].¶

Here is an example of representing a footprint object of "ipv4cidr" type as aset of "ipv4" entities in the ALTO property map. The representation of thefootprint 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" typerepresented by an individual address in an "ipv4" domain in the ALTO propertymap. The translation of the entities in an "ipv6" domain is similar.¶

"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 theInternet.¶

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 domainMUST be encoded as a stringconsisting 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 identifier of an entity in a COUNTRYCODE domain is encoded as an ISO3166-1 alpha-2 code[ISO3166-1] in lowercase.¶

6.1.2.3.Hierarchy and Inheritance

There is no hierarchy or inheritance for properties associated with countrycodes.¶

6.2.Representing CDNI Capabilities as Property Map Entity Properties

This document defines a new entity property type called "cdni-capabilities". AnALTO server can provide a property map resource mapping the "cdni-capabilities"entity property type for a CDNI Advertisement resource that it provides to an"ipv4", "ipv6", "asn", or "countrycode" entity domain.¶

6.2.1.Defining Information Resource Media Type for Property Type cdni-capabilities

The entity property type "cdni-capabilities" allows defining resource-specificentity properties. When resource-specific entity properties are defined withentity property type "cdni-capabilities", the defining information resource fora "cdni-capabilities" propertyMUST be a CDNI Advertisement resource provided bythe ALTO server. The media type of the defining information resource for a"cdni-capabilities" property is therefore:¶

application/alto-cdni+json¶

6.2.2.Intended Semantics of Property Type cdni-capabilities

The purpose of a "cdni-capabilities" property for an entity is to indicate all the CDNIcapabilities that a corresponding CDNI Advertisement resource provides for thefootprint represented by this entity. Thus, the value of a "cdni-capabilities"propertyMUST be a JSON array. Each element in a "cdni-capabilities" propertyMUST be a JSON object in the format of CDNICapability (seeSection 5.3). The value of a "cdni-capabilities" property for an"ipv4", "ipv6", "asn", "countrycode", or "altopid" entityMUST include all theCDNICapability objects satisfying the following conditions: (1) they areprovided by the defining CDNI Advertisement resource, and (2) the representedfootprint object of this entity is in their footprint restrictions.¶

6.3.Examples

The following examples use the same IRD example given bySection 3.7.1.¶

6.3.1.Property Map

This example shows a full property map in which entities are footprints andentities' property is "cdni-capabilities".¶

 GET /propmap/full/cdnifci HTTP/1.1 Host: alto.example.com Accept: application/alto-propmap+json,application/alto-error+json HTTP/1.1 200 OK Content-Length: 1522 Content-Type: application/alto-propmap+json {   "property-map": {     "meta": {       "dependent-vtags": [         { "resource-id": "my-default-cdnifci",           "tag": "7915dc0290c2705481c491a2b4ffbec482b3cf62"}       ]     },     "countrycode:us": {       "my-default-cdnifci.cdni-capabilities": [         { "capability-type": "FCI.DeliveryProtocol",           "capability-value": {             "delivery-protocols": ["http/1.1"]}}]     },     "ipv4:192.0.2.0/24": {       "my-default-cdnifci.cdni-capabilities": [         { "capability-type": "FCI.DeliveryProtocol",           "capability-value": {             "delivery-protocols": ["http/1.1"]}}]     },     "ipv4:198.51.100.0/24": {       "my-default-cdnifci.cdni-capabilities": [         { "capability-type": "FCI.DeliveryProtocol",           "capability-value": {             "delivery-protocols": ["https/1.1", "http/1.1"]}}]     },     "ipv4:203.0.113.0/24": {       "my-default-cdnifci.cdni-capabilities": [         { "capability-type": "FCI.AcquisitionProtocol",           "capability-value": {             "acquisition-protocols": ["http/1.1"]}}]     },     "ipv6:2001:db8::/32": {       "my-default-cdnifci.cdni-capabilities": [         { "capability-type": "FCI.DeliveryProtocol",           "capability-value": {             "delivery-protocols": ["http/1.1"]}}]     },     "asn:as64496": {       "my-default-cdnifci.cdni-capabilities": [         { "capability-type": "FCI.DeliveryProtocol",           "capability-value": {             "delivery-protocols": ["https/1.1", "http/1.1"]}}]     }   } }

6.3.2.Filtered Property Map

This example uses the filtered property Map Service to get "pid" and"cdni-capabilities" properties for two footprints "ipv4:192.0.2.0/24" and"ipv6:2001:db8::/32".¶

   POST /propmap/lookup/cdnifci-pid HTTP/1.1   Host: alto.example.com   Content-Type: application/alto-propmapparams+json   Accept: application/alto-propmap+json,application/alto-error+json   Content-Length: 181   {     "entities": [       "ipv4:192.0.2.0/24",       "ipv6:2001:db8::/32"     ],     "properties": [ "my-default-cdnifci.cdni-capabilities",                     "my-default-networkmap.pid" ]   } HTTP/1.1 200 OK Content-Length: 796 Content-Type: application/alto-propmap+json {   "property-map": {     "meta": {       "dependent-vtags": [          {"resource-id": "my-default-cdnifci",            "tag": "7915dc0290c2705481c491a2b4ffbec482b3cf62"},          {"resource-id": "my-default-networkmap",            "tag": "7915dc0290c2705481c491a2b4ffbec482b3cf63"}       ]     },     "ipv4:192.0.2.0/24": {       "my-default-cdnifci.cdni-capabilities": [         {"capability-type": "FCI.DeliveryProtocol",          "capability-value": {"delivery-protocols": ["http/1.1"]}}],       "my-default-networkmap.pid": "pid1"     },     "ipv6:2001:db8::/32": {       "my-default-cdnifci.cdni-capabilities": [         {"capability-type": "FCI.DeliveryProtocol",          "capability-value": {"delivery-protocols": ["http/1.1"]}}],       "my-default-networkmap.pid": "pid3"     }   } }

6.3.3.Incremental Updates

In this example, the ALTO client is interested in updates for the properties"cdni-capabilities" and "pid" of two footprints "ipv4:192.0.2.0/24" and"countrycode:fr".¶

  POST /updates/properties HTTP/1.1  Host: alto.example.com  Accept: text/event-stream,application/alto-error+json  Content-Type: application/alto-updatestreamparams+json  Content-Length: 339  {    "add": {      "fci-propmap-stream": {        "resource-id": "filtered-cdnifci-property-map",        "input": {          "properties": [ "my-default-cdnifci.cdni-capabilities",                          "my-default-networkmap.pid" ],          "entities": [ "ipv4:192.0.2.0/24",                        "ipv6:2001:db8::/32" ]        }      }    }  }  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/1414213562373"}  event: application/alto-cdni+json,fci-propmap-stream  data: { ... filtered property map ... }  event: application/merge-patch+json,fci-propmap-stream  data: {  data:   "property-map": {  data:     "meta": {  data:       "dependent-vtags": [  data:         { "resource-id": "my-default-cdnifci",  data:           "tag": "2beeac8ee23c3dd1e98a73fd30df80ece9fa5627"},  data:         { "resource-id": "my-default-networkmap",  data:           "tag": "7915dc0290c2705481c491a2b4ffbec482b3cf63"}  data:       ]  data:     },  data:     "ipv4:192.0.2.0/24": {  data:       "my-default-cdnifci.cdni-capabilities": [  data:         { "capability-type": "FCI.DeliveryProtocol",  data:           "capability-value": {  data:             "delivery-protocols": ["http/1.1", "https/1.1"]}}]  data:     }  data:   }  data: }  event: application/json-patch+json,fci-propmap-stream  data: [  data:   { "op": "replace",  data:     "path": "/meta/dependent-vtags/0/tag",  data:     "value": "61b23185a50dc7b334577507e8f00ff8c3b409e4"  data:   },  data:   { "op": "replace",  data:     "path":  data:     "/property-map/countrycode:fr/my-default-networkmap.pid",  data:     "value": "pid5"  data:   }  data: ]

7.IANA Considerations

This document defines two new media types: "application/alto-cdni+json", asdescribed inSection 7.1, and "application/cdnifilter+json", as described inSection 7.2. It also defines a new CDNI Metadata Footprint Type(Section 7.3), two new ALTO entity domain types(Section 7.4), and a new ALTO entity property type(Section 7.5).¶

7.1.application/alto-cdni+json Media Type

Type name:

application¶

Subtype name:

alto-cdni+json¶

Required parameters:

N/A¶

Optional parameters:

N/A¶

Encoding considerations:

Encoding considerations are identical to those specified for the"application/json" media type. See[RFC8259].¶

Security considerations:

Security considerations related to the generation and consumption of ALTOProtocol messages are discussed inSection 15 of [RFC7285].¶

Interoperability considerations:

N/A¶

Published specification:

Section 3 of RFC 9241¶

Applications that use this media type:

ALTO servers and ALTO clients[RFC7285] either stand alone or are embedded within otherapplications that provide CDNI interfaces for uCDNs or dCDNs.¶

Fragment identifier considerations:

N/A¶

Additional information:

Magic number(s):: N/A¶
File extension(s):: N/A¶
Macintosh file type code(s):: N/A¶

Person & email address to contact for further information:

See Authors' Addresses section.¶

Intended usage:

COMMON¶

Restrictions on usage:

N/A¶

Author:

See Authors' Addresses section.¶

Change controller:

Internet Engineering Task Force (iesg@ietf.org)¶

7.2.application/alto-cdnifilter+json Media Type

Type name:

application¶

Subtype name:

alto-cdnifilter+json¶

Required parameters:

N/A¶

Optional parameters:

N/A¶

Encoding considerations:

Encoding considerations are identical to those specified for the"application/json" media type. See[RFC8259].¶

Security considerations:

Security considerations related to the generation and consumption of ALTOProtocol messages are discussed inSection 15 of [RFC7285].¶

Interoperability considerations:

N/A¶

Published specification:

Section 5 of RFC 9241¶

Applications that use this media type:

ALTO servers and ALTO clients[RFC7285] either stand alone or are embeddedwithin other applications that provide CDNI interfaces for uCDNs or dCDNsand supports CDNI capability-based filtering.¶

Fragment identifier considerations:

N/A¶

Additional information:

Magic number(s):: N/A¶
File extension(s):: N/A¶
Macintosh file type code(s):: N/A¶

Person & email address to contact for further information:

See Authors' Addresses section.¶

Intended usage:

COMMON¶

Restrictions on usage:

N/A¶

Author:

See Authors' Addresses section.¶

Change controller:

Internet Engineering Task Force (iesg@ietf.org)¶

7.3.CDNI Metadata Footprint Types Registry

This document updates the "CDNI Metadata Footprint Types" registry created bySection 7.2 of [RFC8006]. A new footprint type, which is listed inTable 1, has been registered.¶

Table 1:CDNI Metadata Footprint Type
Footprint Type	Description	Reference
altopid	A list of PID names	RFC 9241,Section 4

7.4.ALTO Entity Domain Types Registry

This document updates the "ALTO Entity Domain Types" registry created bySection 11.2 of [RFC9240]. Two new entity domain types, which are listed inTable 2, have been registered.¶

Table 2:Additional ALTO Entity Domain Types
Identifier	Entity Identifier Encoding	Hierarchy and Inheritance	Media Type of Defining Resource	Mapping to ALTO Address Type
asn	See RFC 9241,Section 6.1.1.2	None	None	false
countrycode	See RFC 9241,Section 6.1.2.2	None	None	false

7.5.ALTO Entity Property Types Registry

This document updates the "ALTO Entity Property Types" registry created bySection 11.3 of [RFC9240]. A new entity property type,which is listed inTable 3, has been registered.¶

Table 3:Additional ALTO Entity Property Type
Identifier	Intended Semantics	Media Type of Defining Resource
cdni-capabilities	See RFC 9241,Section 6.2	application/alto-cdni+json

8.Security Considerations

As an extension of the base ALTO Protocol[RFC7285], this document fits intothe architecture of the base protocol, and hence Security Considerations of thebase protocol (Section 15 of [RFC7285]) fully apply when this extension isprovided by an ALTO server.¶

In the context of CDNI Advertisement, the following security risk scenariosshould be considered:¶

Authenticity and integrity of ALTO information: an attacker may disguiseitself as an ALTO server for a dCDN (e.g., by starting a on-path attack) and provide false capabilities and footprints to a uCDN using theCDNI Advertisement Service. Such false information may lead a uCDN to (1)select an incorrect dCDN to serve user requests or (2) skip uCDNs in goodconditions. To address this risk, protection strategies inSection 15.1.2 of [RFC7285] can be applied.¶
Potential undesirable guidance from authenticated ALTO information: a dCDNcan provide a uCDN with limited capabilities and smaller footprint coverage sothat the dCDN can avoid transferring traffic for a uCDN that they should haveto transfer. To reduce this risk, the protection strategies inSection 15.2.2 of [RFC7285] can be considered.¶
Confidentiality and privacy of ALTO information: footprint propertiesintegrated with ALTO property maps may expose network location identifiers(e.g., IP addresses or fine-grained PIDs). To address this risk, theprotection strategy for risk types (1) and (3) as described inSection 15.3 of [RFC7285] can be considered.¶
For availability of ALTO services, an attacker may conduct service-degradationattacks using services defined in this document to disable ALTO services of anetwork. It may request potentially large, full CDNI Advertisement resourcesfrom an ALTO server in a dCDN continuously in order to consume the bandwidth resourcesof that ALTO server. It may also query filtered property Map Services withmany smaller individual footprints in order to consume the computation resources ofthe ALTO server. To mitigate these risks, the protection strategies inSection 15.5.2 of [RFC7285] can be applied.¶

Although protection strategies as described inSection 15 of [RFC7285] shouldbe applied to address aforementioned security and privacy considerations,two special cases need to be included as follows:¶

As required bySection 7 of [RFC8008],¶
All protocols that implement these capabilities and footprintadvertisement objects areREQUIRED to provide integrity andauthentication services.¶
Therefore, the uCDN (ALTO Client)MUST be authenticated to the dCDN (ALTO Server). And the dCDN (ALTO Server)MUST support HTTP Digest Authentication[RFC7616] andMAY also support TLS mutualauthentication[RFC8446]. The authentication method will need to be negotiated out ofband and is out of scope for this document, as is the approach forprovisioning and managing these credentials.¶
One specific information leakage risk introduced by this document cannotbe addressed by these strategies. In particular, if a dCDN A signs agreements with multiple uCDNs without any isolation, dCDN A may disclose extra information of one uCDN to another one. In that case, one uCDN may redirect requests that should not have to be served by dCDN A to dCDN A.¶
To reduce the risk, a dCDNSHOULD isolate full and/or filtered CDNI Advertisementresources for different uCDNs. It could consider generating URIs of differentfull and/or filtered CDNI Advertisement resources by hashing its company ID, auCDN's company ID as well as their agreements. A dCDNSHOULD avoid exposingall full and/or filtered CDNI Advertisement resources in one of its IRDs.¶

9.References

9.1.Normative References

[ISO3166-1]: International Organization for Standardization,"Codes for the representation of names of countries and their subdivisions -- Part 1: Country codes",ISO 3166-1:2020,August 2020.
[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>.
[RFC6793]: Vohra, Q. andE. Chen,"BGP Support for Four-Octet Autonomous System (AS) Number Space",RFC 6793,DOI 10.17487/RFC6793,December 2012,<https://www.rfc-editor.org/info/rfc6793>.
[RFC7285]: Alimi, R., Ed.,Penno, R., Ed.,Yang, Y., Ed.,Kiesel, S.,Previdi, S.,Roome, W.,Shalunov, S., andR. Woundy,"Application-Layer Traffic Optimization (ALTO) Protocol",RFC 7285,DOI 10.17487/RFC7285,September 2014,<https://www.rfc-editor.org/info/rfc7285>.
[RFC7493]: Bray, T., Ed.,"The I-JSON Message Format",RFC 7493,DOI 10.17487/RFC7493,March 2015,<https://www.rfc-editor.org/info/rfc7493>.
[RFC7616]: Shekh-Yusef, R., Ed.,Ahrens, D., andS. Bremer,"HTTP Digest Access Authentication",RFC 7616,DOI 10.17487/RFC7616,September 2015,<https://www.rfc-editor.org/info/rfc7616>.
[RFC8006]: Niven-Jenkins, B.,Murray, R.,Caulfield, M., andK. 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., andK. 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>.
[RFC8259]: Bray, T., Ed.,"The JavaScript Object Notation (JSON) Data Interchange Format",STD 90,RFC 8259,DOI 10.17487/RFC8259,December 2017,<https://www.rfc-editor.org/info/rfc8259>.
[RFC8446]: Rescorla, E.,"The Transport Layer Security (TLS) Protocol Version 1.3",RFC 8446,DOI 10.17487/RFC8446,August 2018,<https://www.rfc-editor.org/info/rfc8446>.
[RFC8895]: Roome, W. andY. Yang,"Application-Layer Traffic Optimization (ALTO) Incremental Updates Using Server-Sent Events (SSE)",RFC 8895,DOI 10.17487/RFC8895,November 2020,<https://www.rfc-editor.org/info/rfc8895>.
[RFC9240]: Roome, W.,Randriamasy, S.,Yang, Y.,Zhang, J., andK. 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>.

9.2.Informative References

[ALTO-PATH-VECTOR]: Gao, K.,Lee, Y.,Randriamasy, S.,Yang, Y. R., andJ. J. Zhang,"An ALTO Extension: Path Vector",Work in Progress,Internet-Draft, draft-ietf-alto-path-vector-25,20 March 2022,<https://datatracker.ietf.org/doc/html/draft-ietf-alto-path-vector-25>.
[RFC5693]: Seedorf, J. andE. Burger,"Application-Layer Traffic Optimization (ALTO) Problem Statement",RFC 5693,DOI 10.17487/RFC5693,October 2009,<https://www.rfc-editor.org/info/rfc5693>.
[RFC6707]: Niven-Jenkins, B.,Le Faucheur, F., andN. Bitar,"Content Distribution Network Interconnection (CDNI) Problem Statement",RFC 6707,DOI 10.17487/RFC6707,September 2012,<https://www.rfc-editor.org/info/rfc6707>.
[RFC7971]: Stiemerling, M.,Kiesel, S.,Scharf, M.,Seidel, H., andS. Previdi,"Application-Layer Traffic Optimization (ALTO) Deployment Considerations",RFC 7971,DOI 10.17487/RFC7971,October 2016,<https://www.rfc-editor.org/info/rfc7971>.
[RFC7975]: Niven-Jenkins, B., Ed. andR. van Brandenburg, Ed.,"Request Routing Redirection Interface for Content Delivery Network (CDN) Interconnection",RFC 7975,DOI 10.17487/RFC7975,October 2016,<https://www.rfc-editor.org/info/rfc7975>.

Movatterモバイル変換

RFC 9241

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