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.¶

• 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.¶
• 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 FCI? 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.¶

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, i.e., 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 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.¶

3.1. 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.¶

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].¶

    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.¶

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-specific CDNI Payload Types defined in [RFC8008] as the mandatory-to-implement CDNI capabilities.¶

3.7. Examples

 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"
         }
       }
     }
   }
 }

  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" ]
            }
          ]
        }
      ]
    }
  }

 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: ]

4.1. 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.¶

 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" ]
     }
   }
 }

 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" ]
           }
         ]
       }
     ]
   }
 }

  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: ]

5.1. 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 of the 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 ReqFilteredCDNIAdvertisement 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 in Section 5.1 of [RFC8008].¶

capability-value:

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

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;¶
• 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 server MUST return an "E_INVALID_FIELD_VALUE" 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.¶

5.7. Examples

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

  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" ]
            }
          ]
        }
      ]
    }
  }

  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: ]

6.1. 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.¶

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

6.2. Representing CDNI Capabilities as Property Map Entity Properties

This document defines a new entity property type called "cdni-capabilities". An ALTO 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.¶

6.3. Examples

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

 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"]}}]
     }
   }
 }

   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"
     }
   }
 }

  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: ]

7.1. 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 ALTO Protocol messages are discussed in Section 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 other applications 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 ([email protected])¶

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 ALTO Protocol messages are discussed in Section 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 embedded within other applications that provide CDNI interfaces for uCDNs or dCDNs and 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 ([email protected])¶

7.3. CDNI Metadata Footprint Types Registry

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

7.4. ALTO Entity Domain Types Registry

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

7.5. ALTO Entity Property Types Registry

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