RFC 9241 | CDNI FCI Using ALTO | July 2022 |
Seedorf, et al. | Standards Track | [Page] |
The Content Delivery Networks Interconnection (CDNI) framework in RFC 6707 defines a set of protocols to interconnect CDNs to achieve multiple goals, including extending the reach of a given CDN. A CDNI Request Routing Footprint & Capabilities Advertisement interface (FCI) is needed to achieve the goals of a CDNI. RFC 8008 defines the FCI semantics and provides guidelines on the FCI protocol, but the exact protocol is not specified. This document defines a new Application-Layer Traffic Optimization (ALTO) service, called "CDNI Advertisement Service", that provides an implementation of the FCI, following the guidelines defined in RFC 8008.¶
This is an Internet Standards Track document.¶
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.¶
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9241.¶
Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
The ability to interconnect multiple content delivery networks (CDNs) has many benefits, including increased coverage, capability, and reliability. The Content Delivery Networks Interconnection (CDNI) framework [RFC6707] defines four interfaces to interconnect CDNs: (1) the CDNI Request Routing Interface, (2) the CDNI Metadata Interface, (3) the CDNI Logging Interface, and (4) the CDNI Control Interface.¶
Among these four interfaces, the CDNI Request Routing Interface provides key functions, as specified in [RFC6707]:¶
The CDNI Request Routing interface enables a Request Routing function in an Upstream CDN to query a Request Routing function in a Downstream CDN to determine if the Downstream CDN is able (and willing) to accept the delegated Content Request. It also allows the Downstream CDN to control what should be returned to the User Agent in the redirection message by the upstream Request Routing function.¶
At a high level, therefore, the scope of the CDNI Request Routing Interface contains two main tasks: (1) determining if the dCDN (downstream CDN) is willing to accept a delegated Content Request and (2) redirecting the Content Request coming from a uCDN (upstream CDN) to the proper entry point or entity in the dCDN.¶
Correspondingly, the Request Routing Interface is broadly divided into two functionalities: (1) the CDNI Footprint & Capabilities Advertisement interface (FCI) defined in [RFC8008] and (2) the CDNI Request Routing Redirection interface (RI) defined in [RFC7975]. This document focuses on the first functionality (CDNI FCI).¶
Specifically, CDNI FCI allows both an Advertisement from a dCDN to a uCDN (push) and a query from a uCDN to a dCDN (pull) so that the uCDN knows whether it can redirect a particular user request to that dCDN.¶
A key component in defining the CDNI FCI is defining the objects that describe the footprints and capabilities of a dCDN. Such objects are already specified in Section 5 of [RFC8008]. However, no protocol is defined to transport and update such objects between a uCDN and a dCDN.¶
To define such a protocol, this document specifies an extension of the Application-Layer Traffic Optimization (ALTO) Protocol [RFC7285] by introducing a new ALTO service called "CDNI Advertisement Service".¶
Section 2.3 discusses the benefits in using ALTO as a transport protocol.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The design of CDNI FCI transport using ALTO assumes an understanding of both FCI semantics and ALTO. Hence, this document starts with a non-normative review of both.¶
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:¶
[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.¶
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:¶
The ALTO Protocol relies upon the ALTO information service framework, which consists of multiple services. All ALTO services are "provided through a common transport protocol; messaging structure and encoding; and transaction model" [RFC7285]. The ALTO Protocol specification defines multiple initial services, e.g., the ALTO Network Map Service and Cost Map Service.¶
This document defines a new ALTO service, called "CDNI Advertisement Service", which conveys JSON [RFC8259] objects of media type "application/alto-cdni+json". These JSON objects are used to transport BaseAdvertisementObject objects defined in [RFC8008]. This document specifies how to transport such BaseAdvertisementObject objects via the ALTO Protocol with the ALTO CDNI Advertisement Service. Similar to other ALTO services, this document defines the ALTO information resource for the CDNI Advertisement Service as follows.¶
Note that the encoding of BaseAdvertisementObject reuses the one defined in [RFC8008] and therefore also follows the recommendations of I-JSON (Internet JSON) [RFC7493], which is required by [RFC8008].¶
The media type of the CDNI Advertisement resource is "application/alto-cdni+json" (see Section 7).¶
A CDNI Advertisement resource is requested using the HTTP GET method.¶
There are no applicable Accept Input parameters.¶
There are no applicable capabilities.¶
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.¶
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.¶
Below is the IRD of a simple, example ALTO server. The server provides both base ALTO information resources (e.g., network maps) and CDNI FCI-related information resources (e.g., CDNI Advertisement resources), demonstrating a single, integrated environment.¶
Specifically, the IRD announces nine information resources as follows:¶
two update stream services:¶
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" } } } } }¶
This basic example demonstrates a simple CDNI Advertisement resource, which does not depend on other resources. There are three BaseAdvertisementObjects in this resource and these objects' capabilities are "http/1.1" delivery protocol, ["http/1.1", "https/1.1"] delivery protocol, and "https/1.1" acquisition protocol, respectively.¶
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" ] } ] } ] } }¶
A benefit of using ALTO to provide CDNI Advertisement resources is that such resources can be updated using ALTO incremental updates [RFC8895]. Below is an example that also shows the benefit of having both JSON merge patch and JSON patch to encode updates.¶
At first, an ALTO client requests updates for "my-default-cdnifci", and the ALTO server returns the "control-uri" followed by the full CDNI Advertisement response. Then when there is a change in the "delivery-protocols" in that "http/1.1" is removed (from ["http/1.1", "https/1.1"] to only "https/1.1") due to maintenance of the "http/1.1" clusters, the ALTO server regenerates the new CDNI Advertisement resource and pushes the full replacement to the ALTO client. Later on, the ALTO server notifies the ALTO client that "192.0.2.0/24" is added into the "ipv4" footprint object for delivery protocol "https/1.1" by sending the change encoded by JSON patch to the ALTO client.¶
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: ]¶
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).¶
The following examples use the same IRD given in Section 3.7.1.¶
Below provides a sample network map whose resource ID is "my-eu-netmap". This map is referenced by the CDNI Advertisement example in Section 4.2.2.¶
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" ] } } }¶
This example shows a CDNI Advertisement resource that depends on a network map described in Section 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" ] } ] } ] } }¶
In this example, the ALTO client is interested in changes of "my-cdnifci-with-pid-footprints" and its dependent network map "my-eu-netmap". Considering two changes, the first one is to change footprints of the "https/1.1" delivery protocol capability, and the second one is to remove the "south-france" PID from the footprints of the "https/1.1" acquisition protocol capability.¶
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: ]¶
Sections 3 and 4 describe the CDNI Advertisement Service that can be used to enable a uCDN to get capabilities with footprint restrictions from dCDNs. However, since always getting full CDNI Advertisement resources from dCDNs is inefficient, this document introduces a new service named "Filtered CDNI Advertisement Service" to allow a client to filter a CDNI Advertisement resource using a client-given set of CDNI capabilities. For each entry of the CDNI Advertisement response, an entry will only be returned to the client if it contains at least one of the client-given CDNI capabilities. The relationship between a filtered CDNI Advertisement resource and a CDNI Advertisement resource is similar to the relationship between a filtered network/cost map and a network/cost map.¶
A filtered CDNI Advertisement resource uses the same media type defined for the CDNI Advertisement resource in Section 3.1: "application/alto-cdni+json".¶
A filtered CDNI Advertisement resource is requested using the HTTP POST method.¶
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:¶
The same as Base Advertisement Object's "capability-type" defined in Section 5.1 of [RFC8008].¶
The same as Base Advertisement Object's "capability-value" defined in Section 5.1 of [RFC8008].¶
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.¶
There are no applicable capabilities.¶
The same rules as for the "uses" field of the CDNI Advertisement resource apply (see Section 3.5).¶
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:¶
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:¶
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.¶
The following examples use the same IRD example as in Section 3.7.1.¶
This example filters the full CDNI Advertisement resource in Section 3.7.2 by selecting only the "http/1.1" delivery protocol capability. Only the second BaseAdvertisementObject in the full resource will be returned because the second object's capability is "http/1.1" and "https/1.1" delivery protocols, which is the superset of "https/1.1" delivery protocol.¶
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" ] } ] } ] } }¶
In this example, the ALTO client only cares about the updates of one advertisement object for delivery protocol capability whose value includes "https/1.1". Thus, it adds its limitation of capabilities in "input" field of the POST request.¶
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: ]¶
Besides the requirement of retrieving footprints of given capabilities, another common requirement for uCDN is to query CDNI capabilities of given footprints.¶
Considering each footprint as an entity with properties including CDNI capabilities, a natural way to satisfy this requirement is to use the ALTO property map as defined in [RFC9240]. This section describes how ALTO clients look up properties for individual footprints. First, it describes how to represent footprint objects as entities in the ALTO property map. Then it describes how to represent footprint capabilities as entity properties in the ALTO property map. Finally, it provides examples of the full property map and the filtered property map supporting CDNI capabilities, and their incremental updates.¶
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:¶
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"] }¶
The ASN domain associates property values with Autonomous Systems in the Internet.¶
The entity domain type of the ASN domain is "asn" (in lowercase).¶
The entity identifier of an entity in an ASN domain MUST be encoded as a string consisting of the characters "as" (in lowercase) followed by the ASN [RFC6793] as a decimal number without leading zeros.¶
There is no hierarchy or inheritance for properties associated with ASN.¶
The COUNTRYCODE domain associates property values with countries.¶
The entity domain type of the COUNTRYCODE domain is "countrycode" (in lowercase).¶
The entity identifier of an entity in a COUNTRYCODE domain is encoded as an ISO 3166-1 alpha-2 code [ISO3166-1] in lowercase.¶
There is no hierarchy or inheritance for properties associated with country codes.¶
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.¶
The entity property type "cdni-capabilities" allows defining resource-specific entity properties. When resource-specific entity properties are defined with entity property type "cdni-capabilities", the defining information resource for a "cdni-capabilities" property MUST be a CDNI Advertisement resource provided by the ALTO server. The media type of the defining information resource for a "cdni-capabilities" property is therefore:¶
application/alto-cdni+json¶
The purpose of a "cdni-capabilities" property for an entity is to indicate all the CDNI capabilities that a corresponding CDNI Advertisement resource provides for the footprint represented by this entity. Thus, the value of a "cdni-capabilities" property MUST be a JSON array. Each element in a "cdni-capabilities" property MUST be a JSON object in the format of CDNICapability (see Section 5.3). The value of a "cdni-capabilities" property for an "ipv4", "ipv6", "asn", "countrycode", or "altopid" entity MUST include all the CDNICapability objects satisfying the following conditions: (1) they are provided by the defining CDNI Advertisement resource, and (2) the represented footprint object of this entity is in their footprint restrictions.¶
The following examples use the same IRD example given by Section 3.7.1.¶
This example shows a full property map in which entities are footprints and entities' 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"]}}] } } }¶
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" } } }¶
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: ]¶
This document defines two new media types: "application/alto-cdni+json", as described in Section 7.1, and "application/cdnifilter+json", as described in Section 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).¶
application¶
alto-cdni+json¶
N/A¶
N/A¶
Encoding considerations are identical to those specified for the "application/json" media type. See [RFC8259].¶
Security considerations related to the generation and consumption of ALTO Protocol messages are discussed in Section 15 of [RFC7285].¶
N/A¶
ALTO servers and ALTO clients [RFC7285] either stand alone or are embedded within other applications that provide CDNI interfaces for uCDNs or dCDNs.¶
N/A¶
See Authors' Addresses section.¶
COMMON¶
N/A¶
See Authors' Addresses section.¶
Internet Engineering Task Force (iesg@ietf.org)¶
application¶
alto-cdnifilter+json¶
N/A¶
N/A¶
Encoding considerations are identical to those specified for the "application/json" media type. See [RFC8259].¶
Security considerations related to the generation and consumption of ALTO Protocol messages are discussed in Section 15 of [RFC7285].¶
N/A¶
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.¶
N/A¶
See Authors' Addresses section.¶
COMMON¶
N/A¶
See Authors' Addresses section.¶
Internet Engineering Task Force (iesg@ietf.org)¶
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.¶
Footprint Type | Description | Reference |
---|---|---|
altopid | A list of PID names | RFC 9241, Section 4 |
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.¶
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 |
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.¶
Identifier | Intended Semantics | Media Type of Defining Resource |
---|---|---|
cdni-capabilities | See RFC 9241, Section 6.2 | application/alto-cdni+json |
As an extension of the base ALTO Protocol [RFC7285], this document fits into the architecture of the base protocol, and hence Security Considerations of the base protocol (Section 15 of [RFC7285]) fully apply when this extension is provided by an ALTO server.¶
In the context of CDNI Advertisement, the following security risk scenarios should be considered:¶
Although protection strategies as described in Section 15 of [RFC7285] should be applied to address aforementioned security and privacy considerations, two special cases need to be included as follows:¶
As required by Section 7 of [RFC8008],¶
All protocols that implement these capabilities and footprint advertisement objects are REQUIRED to provide integrity and authentication 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] and MAY also support TLS mutual authentication [RFC8446]. The authentication method will need to be negotiated out of band and is out of scope for this document, as is the approach for provisioning and managing these credentials.¶
One specific information leakage risk introduced by this document cannot be 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 dCDN SHOULD isolate full and/or filtered CDNI Advertisement resources for different uCDNs. It could consider generating URIs of different full and/or filtered CDNI Advertisement resources by hashing its company ID, a uCDN's company ID as well as their agreements. A dCDN SHOULD avoid exposing all full and/or filtered CDNI Advertisement resources in one of its IRDs.¶
The authors thank Matt Caulfield, Danny Alex Lachos Perez, Daryl Malas, and Sanjay Mishra for their timely reviews and invaluable comments. Big thanks also to the ALTO WG Chairs (Qin Wu and Vijay Gurbani), all the directorate reviewers, and the IESG reviewers (Martin Duke, Erik Kline, Martin Vigoureux, Murray Kucherawy, Roman Danyliw, Zaheduzzaman Sarker, Éric Vyncke, and Francesca Palombini), for their thorough reviews, discussions, guidance, and shepherding, which further improve this document.¶
Jan Seedorf has been partially supported by the GreenICN project (GreenICN: Architecture and Applications of Green Information Centric Networking), a research project supported jointly by the European Commission under its 7th Framework Program (contract no. 608518) and the National Institute of Information and Communications Technology (NICT) in Japan (contract no. 167). The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the GreenICN project, the European Commission, or NICT.¶
This document has also been supported by the Coordination Support Action entitled 'Supporting European Experts Presence in International Standardisation Activities in ICT' (StandICT.eu) funded by the European Commission under the Horizon 2020 Programme with Grant Agreement no. 780439. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the European Commission.¶