rfc:rfc9241
Internet Engineering Task Force (IETF) J. Seedorf Request for Comments: 9241 HFT Stuttgart Category: Standards Track Y. Yang ISSN: 2070-1721 Yale University
K. Ma
Ericsson
J. Peterson
NeuStar
J. Zhang
Tongji University
July 2022
Content Delivery Network Interconnection (CDNI) Footprint and
Capabilities Advertisement Using Application-Layer Traffic Optimization
(ALTO)
Abstract
The Content Delivery Networks Interconnection (CDNI) framework in RFC 6707 defines a set of protocols to interconnect CDNs to achieve multiple goals, including extending the reach of a given CDN. A CDNI Request Routing Footprint & Capabilities Advertisement interface (FCI) is needed to achieve the goals of a CDNI. RFC 8008 defines the FCI semantics and provides guidelines on the FCI protocol, but the exact protocol is not specified. This document defines a new Application-Layer Traffic Optimization (ALTO) service, called "CDNI Advertisement Service", that provides an implementation of the FCI, following the guidelines defined in RFC 8008.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9241.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction
2. Terminology and Background
2.1. Terminology
2.2. Semantics of FCI Advertisement
2.3. ALTO Background and Benefits
3. CDNI Advertisement Service
3.1. Media Type
3.2. HTTP Method
3.3. Accept Input Parameters
3.4. Capabilities
3.5. Uses
3.6. Response
3.7. Examples
3.7.1. IRD
3.7.2. A Basic Example
3.7.3. Incremental Updates
4. CDNI Advertisement Service Using ALTO Network Map
4.1. Network Map Footprint Type: altopid
4.2. Examples
4.2.1. ALTO Network Map for CDNI Advertisements
4.2.2. ALTO PID Footprints in CDNI Advertisements
4.2.3. Incremental Updates
5. Filtered CDNI Advertisement Using CDNI Capabilities
5.1. Media Type
5.2. HTTP Method
5.3. Accept Input Parameters
5.4. Capabilities
5.5. Uses
5.6. Response
5.7. Examples
5.7.1. A Basic Example
5.7.2. Incremental Updates
6. Query Footprint Properties Using ALTO Property Map Service
6.1. Representing Footprint Objects as Property Map Entities
6.1.1. ASN Domain
6.1.2. COUNTRYCODE Domain
6.2. Representing CDNI Capabilities as Property Map Entity
Properties
6.2.1. Defining Information Resource Media Type for Property
Type cdni-capabilities
6.2.2. Intended Semantics of Property Type cdni-capabilities
6.3. Examples
6.3.1. Property Map
6.3.2. Filtered Property Map
6.3.3. Incremental Updates
7. IANA Considerations
7.1. application/alto-cdni+json Media Type
7.2. application/alto-cdnifilter+json Media Type
7.3. CDNI Metadata Footprint Types Registry
7.4. ALTO Entity Domain Types Registry
7.5. ALTO Entity Property Types Registry
8. Security Considerations
9. References
9.1. Normative References
9.2. Informative References
Acknowledgments
Contributors
Authors' Addresses
1. Introduction
The ability to interconnect multiple content delivery networks (CDNs) has many benefits, including increased coverage, capability, and reliability. The Content Delivery Networks Interconnection (CDNI) framework [RFC6707] defines four interfaces to interconnect CDNs: (1) the CDNI Request Routing Interface, (2) the CDNI Metadata Interface, (3) the CDNI Logging Interface, and (4) the CDNI Control Interface.
Among these four interfaces, the CDNI Request Routing Interface provides key functions, as specified in [RFC6707]:
| The CDNI Request Routing interface enables a Request Routing | function in an Upstream CDN to query a Request Routing function in | a Downstream CDN to determine if the Downstream CDN is able (and | willing) to accept the delegated Content Request. It also allows | the Downstream CDN to control what should be returned to the User | Agent in the redirection message by the upstream Request Routing | function.
At a high level, therefore, the scope of the CDNI Request Routing Interface contains two main tasks: (1) determining if the 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.
2. Terminology and Background
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
The design of CDNI FCI transport using ALTO assumes an understanding of both FCI semantics and ALTO. Hence, this document starts with a non-normative review of both.
2.1. Terminology
The document uses the CDNI terms defined in [RFC6707], [RFC8006], and [RFC8008]. Also, the document uses the ALTO terms defined in [RFC7285] and [RFC9240]. This document uses the following abbreviations:
ALTO: Application-Layer Traffic Optimization
ASN: Autonomous System Number
CDN: Content Delivery Network
CDNI: CDN Interconnection
dCDN: Downstream CDN
FCI: CDNI FCI, CDNI Request Routing Footprint & Capabilities
Advertisement interface
IRD: Information Resource Directory in ALTO
PID: Provider-defined Identifier in ALTO
uCDN: Upstream CDN
2.2. Semantics of FCI Advertisement
[RFC8008] defines the semantics of CDNI FCI, provides guidance on what footprint and capabilities mean in a CDNI context, and specifies the requirements on the CDNI FCI transport protocol. The definitions in [RFC8008] depend on [RFC8006]. Below is a non-normative review of key related points of [RFC8008] and [RFC8006]. For detailed information and normative specification, the reader should refer to these two RFCs.
- 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. CDNI Advertisement Service
The ALTO Protocol relies upon the ALTO information service framework, which consists of multiple services. All ALTO services are "provided through a common transport protocol; messaging structure and encoding; and transaction model" [RFC7285]. The ALTO Protocol specification defines multiple initial services, e.g., the ALTO Network Map Service and Cost Map Service.
This document defines a new ALTO service, called "CDNI Advertisement Service", which conveys JSON [RFC8259] objects of media type "application/alto-cdni+json". These JSON objects are used to transport BaseAdvertisementObject objects defined in [RFC8008]. This document specifies how to transport such BaseAdvertisementObject objects via the ALTO Protocol with the ALTO CDNI Advertisement Service. Similar to other ALTO services, this document defines the ALTO information resource for the CDNI Advertisement Service as follows.
Note that the encoding of BaseAdvertisementObject reuses the one defined in [RFC8008] and therefore also follows the recommendations of I-JSON (Internet JSON) [RFC7493], which is required by [RFC8008].
3.1. Media Type
The media type of the CDNI Advertisement resource is "application/ alto-cdni+json" (see Section 7).
3.2. HTTP Method
A CDNI Advertisement resource is requested using the HTTP GET method.
3.3. Accept Input Parameters
There are no applicable Accept Input parameters.
3.4. Capabilities
There are no applicable capabilities.
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
3.7.1. IRD
Below is the IRD of a simple, example ALTO server. The server provides both base ALTO information resources (e.g., network maps) and CDNI FCI-related information resources (e.g., CDNI Advertisement resources), demonstrating a single, integrated environment.
Specifically, the IRD announces nine information resources as follows:
- two network maps,
- one CDNI Advertisement resource without dependency,
- one CDNI Advertisement resource depending on a network map,
- one filtered CDNI Advertisement resource to be defined in
Section 5,
- one property map including "cdni-capabilities" as its entity
property,
- one filtered property map including "cdni-capabilities" and "pid"
as its entity properties, and
- two update stream services:
- one for updating CDNI Advertisement resources,
- one for updating property maps
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 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" ]
}
]
}
]
}
}
3.7.3. Incremental Updates
A benefit of using ALTO to provide CDNI Advertisement resources is that such resources can be updated using ALTO incremental updates [RFC8895]. Below is an example that also shows the benefit of having both JSON merge patch and JSON patch to encode updates.
At first, an ALTO client requests updates for "my-default-cdnifci", and the ALTO server returns the "control-uri" followed by the full CDNI Advertisement response. Then when there is a change in the "delivery-protocols" in that "http/1.1" is removed (from ["http/1.1", "https/1.1"] to only "https/1.1") due to maintenance of the "http/1.1" clusters, the ALTO server regenerates the new CDNI Advertisement resource and pushes the full replacement to the ALTO client. Later on, the ALTO server notifies the ALTO client that "192.0.2.0/24" is added into the "ipv4" footprint object for delivery protocol "https/1.1" by sending the change encoded by JSON patch to the ALTO client.
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) to represent a group of IPv4 or IPv6 addresses to which can be applied the same management policy. The PID is an alternative to the predefined CDNI footprint types (i.e., "ipv4cidr", "ipv6cidr", "asn", and "countrycode").
To leverage this concept, this document defines a new CDNI Footprint Type called "altopid". A CDNI Advertisement resource can depend on an ALTO network map resource and use "altopid" footprints to compress its CDNI Footprint Payload.
Specifically, the "altopid" footprint type indicates that the corresponding footprint value is a list of PIDNames as defined in [RFC7285]. These PIDNames are references of PIDs in a network map resource. Hence a CDNI Advertisement resource using "altopid" footprints depends on a network map. For such a CDNI Advertisement resource, the resource ID of its dependent network map MUST be included in the "uses" field of its IRD entry, and the "dependent- vtags" field with a reference to this network map MUST be included in its response (see the example in Section 4.2.2).
4.2. Examples
The following examples use the same IRD given in Section 3.7.1.
4.2.1. ALTO Network Map for CDNI Advertisements
Below provides a sample network map whose resource ID is "my-eu- netmap". This map is referenced by the CDNI Advertisement example in Section 4.2.2.
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 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" ]
}
]
}
]
}
}
4.2.3. Incremental Updates
In this example, the ALTO client is interested in changes of "my- cdnifci-with-pid-footprints" and its dependent network map "my-eu- netmap". Considering two changes, the first one is to change footprints of the "https/1.1" delivery protocol capability, and the second one is to remove the "south-france" PID from the footprints of the "https/1.1" acquisition protocol capability.
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
Sections 3 and 4 describe the CDNI Advertisement Service that can be used to enable a uCDN to get capabilities with footprint restrictions from dCDNs. However, since always getting full CDNI Advertisement resources from dCDNs is inefficient, this document introduces a new service named "Filtered CDNI Advertisement Service" to allow a client to filter a CDNI Advertisement resource using a client-given set of CDNI capabilities. For each entry of the CDNI Advertisement response, an entry will only be returned to the client if it contains at least one of the client-given CDNI capabilities. The relationship between a filtered CDNI Advertisement resource and a CDNI Advertisement resource is similar to the relationship between a filtered network/cost map and a network/cost map.
5.1. Media Type
A filtered CDNI Advertisement resource uses the same media type defined for the CDNI Advertisement resource in Section 3.1: "application/alto-cdni+json".
5.2. HTTP Method
A filtered CDNI Advertisement resource is requested using the HTTP POST method.
5.3. Accept Input Parameters
The input parameters for a filtered CDNI Advertisement resource are supplied in the entity body 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.
5.7.1. A Basic Example
This example filters the full CDNI Advertisement resource in Section 3.7.2 by selecting only the "http/1.1" delivery protocol capability. Only the second BaseAdvertisementObject in the full resource will be returned because the second object's capability is "http/1.1" and "https/1.1" delivery protocols, which is the superset of "https/1.1" delivery protocol.
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 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: ]
6. Query Footprint Properties Using ALTO Property Map Service
Besides the requirement of retrieving footprints of given capabilities, another common requirement for uCDN is to query CDNI capabilities of given footprints.
Considering each footprint as an entity with properties including CDNI capabilities, a natural way to satisfy this requirement is to use the ALTO property map as defined in [RFC9240]. This section describes how ALTO clients look up properties for individual footprints. First, it describes how to represent footprint objects as entities in the ALTO property map. Then it describes how to represent footprint capabilities as entity properties in the ALTO property map. Finally, it provides examples of the full property map and the filtered property map supporting CDNI capabilities, and their incremental updates.
6.1. Representing Footprint Objects as Property Map Entities
A footprint object has two properties: "footprint-type" and
"footprint-value". A "footprint-value" is an array of footprint
values conforming to the specification associated with the registered
footprint type ("ipv4cidr", "ipv6cidr", "asn", "countrycode", and
"altopid"). Considering each ALTO entity defined in [RFC9240] also
has two properties: entity domain type and domain-specific
identifier, a straightforward approach to represent a footprint as an
ALTO entity is to represent its "footprint-type" as an entity domain
type, and its footprint value as a domain-specific identifier.
Each existing footprint type can be represented as an entity domain type as follows:
- According to [RFC9240], "ipv4" and "ipv6" are two predefined
entity domain types, which can be used to represent "ipv4cidr" and
"ipv6cidr" footprints respectively. Note that both "ipv4" and
"ipv6" domains can include not only hierarchical addresses but
also individual addresses. Therefore, a "ipv4cidr" or "ipv6cidr"
footprint with the longest prefix can also be represented by an
individual address entity. When the uCDN receives a property map
with individual addresses in an "ipv4" or "ipv6" domain, it can
translate them as corresponding "ipv4cidr" or "ipv6cidr"
footprints with the longest prefix.
- "pid" is also a predefined entity domain type, which can be used
to represent "altopid" footprints. Note that "pid" is a resource-
specific entity domain. To represent an "altopid" footprint, the
specifying information resource of the corresponding "pid" entity
domain MUST be the dependent network map used by the CDNI
Advertisement resource providing this "altopid" footprint.
- However, no existing entity domain type can represent "asn" and
"countrycode" footprints. To represent footprint-type "asn" and
"countrycode", this document registers two new entity domains in
Section 7 in addition to the ones in [RFC9240].
Here is an example of representing a footprint object of "ipv4cidr" type as a set of "ipv4" entities in the ALTO property map. The representation of the footprint object of "ipv6cidr" type is similar.
{ "footprint-type": "ipv4cidr",
"footprint-value": ["192.0.2.0/24", "198.51.100.0/24"]
} --> "ipv4:192.0.2.0/24", "ipv4:198.51.100.0/24"
And here is an example of the corresponding footprint object of "ipv4cidr" type represented by an individual address in an "ipv4" domain in the ALTO property map. The translation of the entities in an "ipv6" domain is similar.
"ipv4:203.0.113.100" --> {
"footprint-type": "ipv4cidr",
"footprint-value": ["203.0.113.100/32"]
}
6.1.1. ASN Domain
The ASN domain associates property values with Autonomous Systems in the Internet.
6.1.1.1. Entity Domain Type
The entity domain type of the ASN domain is "asn" (in lowercase).
6.1.1.2. Domain-Specific Entity Identifiers
The entity identifier of an entity in an ASN domain MUST be encoded as a string consisting of the characters "as" (in lowercase) followed by the ASN [RFC6793] as a decimal number without leading zeros.
6.1.1.3. Hierarchy and Inheritance
There is no hierarchy or inheritance for properties associated with ASN.
6.1.2. COUNTRYCODE Domain
The COUNTRYCODE domain associates property values with countries.
6.1.2.1. Entity Domain Type
The entity domain type of the COUNTRYCODE domain is "countrycode" (in lowercase).
6.1.2.2. Domain-Specific Entity Identifiers
The entity identifier of an entity in a COUNTRYCODE domain is encoded as an ISO 3166-1 alpha-2 code [ISO3166-1] in lowercase.
6.1.2.3. Hierarchy and Inheritance
There is no hierarchy or inheritance for properties associated with country codes.
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.
6.2.1. Defining Information Resource Media Type for Property Type cdni-
capabilities
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
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 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.
6.3. Examples
The following examples use the same IRD example given by Section 3.7.1.
6.3.1. Property Map
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"]}}]
}
}
}
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", 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).
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 (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 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 (iesg@ietf.org)
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.
+================+=====================+=====================+
| Footprint Type | Description | Reference |
+================+=====================+=====================+
| altopid | A list of PID names | RFC 9241, Section 4 |
+----------------+---------------------+---------------------+
Table 1: CDNI Metadata Footprint Type
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.
+=============+============+=============+=============+=========+ | Identifier | Entity | Hierarchy | Media Type | Mapping | | | Identifier | and | of Defining | to ALTO | | | Encoding | Inheritance | Resource | Address | | | | | | Type | +=============+============+=============+=============+=========+ | asn | See RFC | None | None | false | | | 9241, | | | | | | Section | | | | | | 6.1.1.2 | | | | +-------------+------------+-------------+-------------+---------+ | countrycode | See RFC | None | None | false | | | 9241, | | | | | | Section | | | | | | 6.1.2.2 | | | | +-------------+------------+-------------+-------------+---------+
Table 2: Additional ALTO Entity Domain Types
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.
+===================+====================+===================+
| Identifier | Intended Semantics | Media Type of |
| | | Defining Resource |
+===================+====================+===================+
| cdni-capabilities | See RFC 9241, | application/alto- |
| | Section 6.2 | cdni+json |
+-------------------+--------------------+-------------------+
Table 3: Additional ALTO Entity Property Type
8. Security Considerations
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:
- Authenticity and integrity of ALTO information: an attacker may
disguise itself 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 the CDNI Advertisement Service. Such false information
may lead a uCDN to (1) select an incorrect dCDN to serve user
requests or (2) skip uCDNs in good conditions. To address this
risk, protection strategies in Section 15.1.2 of [RFC7285] can be
applied.
- Potential undesirable guidance from authenticated ALTO
information: a dCDN can provide a uCDN with limited capabilities
and smaller footprint coverage so that the dCDN can avoid
transferring traffic for a uCDN that they should have to transfer.
To reduce this risk, the protection strategies in Section 15.2.2
of [RFC7285] can be considered.
- Confidentiality and privacy of ALTO information: footprint
properties integrated with ALTO property maps may expose network
location identifiers (e.g., IP addresses or fine-grained PIDs).
To address this risk, the protection strategy for risk types (1)
and (3) as described in Section 15.3 of [RFC7285] can be
considered.
- For availability of ALTO services, an attacker may conduct
service-degradation attacks using services defined in this
document to disable ALTO services of a network. It may request
potentially large, full CDNI Advertisement resources from an ALTO
server in a dCDN continuously in order to consume the bandwidth
resources of that ALTO server. It may also query filtered
property Map Services with many smaller individual footprints in
order to consume the computation resources of the ALTO server. To
mitigate these risks, the protection strategies in Section 15.5.2
of [RFC7285] can be applied.
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.
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. and E. 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., and R. 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., and S. 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., and K. Ma,
"Content Delivery Network Interconnection (CDNI)
Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
<https://www.rfc-editor.org/info/rfc8006>.
[RFC8008] Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
R., and K. Ma, "Content Delivery Network Interconnection
(CDNI) Request Routing: Footprint and Capabilities
Semantics", RFC 8008, DOI 10.17487/RFC8008, December 2016,
<https://www.rfc-editor.org/info/rfc8008>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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. and Y. 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., and K.
Gao, "An Extension for Application-Layer Traffic
Optimization (ALTO): Entity Property Maps", RFC 9240,
DOI 10.17487/RFC9240, July 2022,
<https://www.rfc-editor.org/info/rfc9240>.
9.2. Informative References
[ALTO-PATH-VECTOR]
Gao, K., Lee, Y., Randriamasy, S., Yang, Y. R., and J. 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. and E. 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., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, DOI 10.17487/RFC6707, September
2012, <https://www.rfc-editor.org/info/rfc6707>.
[RFC7971] Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and
S. 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. and R. 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>.
Acknowledgments
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 <https://www.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.
Contributors
Xiao Shawn Lin Huawei 2222 Newjinqiao Rd Shanghai 200125 China Phone: +86-15316812351 Email: x.shawn.lin@gmail.com
Authors' Addresses
Jan Seedorf HFT Stuttgart - Univ. of Applied Sciences Schellingstrasse 24 70174 Stuttgart Germany Phone: +49-0711-8926-2801 Email: jan.seedorf@hft-stuttgart.de
Y. Richard Yang Yale University 51 Prospect Street New Haven, CT 06511 United States of America Phone: +1-203-432-6400 Email: yry@cs.yale.edu URI: http://www.cs.yale.edu/~yry/
Kevin J. Ma Ericsson 43 Nagog Park Acton, MA 01720 United States of America Phone: +1-978-844-5100 Email: kevin.j.ma.ietf@gmail.com
Jon Peterson NeuStar 1800 Sutter St., Suite 570 Concord, CA 94520 United States of America Email: jon.peterson@neustar.biz
Jingxuan Jensen Zhang Tongji University 4800 Cao'an Hwy Shanghai 201804 China Email: jingxuan.zhang@tongji.edu.cn
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