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Versions: (draft-seedorf-cdni-request-routing-alto) 00 01 02 03 04 05 06 07 08 09 10 12

ALTO & CDNI WGs                                               J. Seedorf
Internet-Draft                 HFT Stuttgart - Univ. of Applied Sciences
Intended status: Standards Track                                 Y. Yang
Expires: January 14, 2021                                    Tongji/Yale
                                                                   K. Ma
                                                                Ericsson
                                                             J. Peterson
                                                                 Neustar
                                                                J. Zhang
                                                                  Tongji
                                                           July 13, 2020


 Content Delivery Network Interconnection (CDNI) Request Routing: CDNI
          Footprint and Capabilities Advertisement using ALTO
              draft-ietf-alto-cdni-request-routing-alto-12

Abstract

   The Content Delivery Networks Interconnection (CDNI) framework
   [RFC6707] defines a set of protocols to interconnect CDNs, to achieve
   multiple goals such as extending the reach of a given CDN to areas
   that are not covered by that particular CDN.  One component that is
   needed to achieve the goal of CDNI described in [RFC7336] is the CDNI
   Request Routing Footprint & Capabilities Advertisement interface
   (FCI).  [RFC8008] defines precisely the semantics of FCI and provides
   guidelines on the FCI protocol, but the exact protocol is explicitly
   outside the scope of that document.  This document defines an FCI
   protocol using the Application-Layer Traffic Optimization (ALTO)
   protocol, following the guidelines defined in [RFC8008].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 14, 2021.




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Copyright Notice

   Copyright (c) 2020 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 Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Semantics of FCI Advertisement  . . . . . . . . . . . . .   5
     2.2.  ALTO Background and Benefits  . . . . . . . . . . . . . .   6
   3.  CDNI Advertisement Service  . . . . . . . . . . . . . . . . .   8
     3.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .   8
     3.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .   8
     3.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .   8
     3.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .   9
     3.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .   9
     3.7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  12
       3.7.1.  IRD Example . . . . . . . . . . . . . . . . . . . . .  12
       3.7.2.  Basic Example . . . . . . . . . . . . . . . . . . . .  14
       3.7.3.  Incremental Updates Example . . . . . . . . . . . . .  16
   4.  CDNI Advertisement Service using ALTO Network Map . . . . . .  18
     4.1.  Network Map Footprint Type: altopid . . . . . . . . . . .  18
     4.2.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  18
       4.2.1.  IRD Example . . . . . . . . . . . . . . . . . . . . .  18
       4.2.2.  ALTO Network Map for CDNI Advertisement Example . . .  18
       4.2.3.  ALTO PID Footprints in CDNI Advertisement . . . . . .  19
       4.2.4.  Incremental Updates Example . . . . . . . . . . . . .  20
   5.  Filtered CDNI Advertisement using CDNI Capabilities . . . . .  22
     5.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  22
     5.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  22
     5.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  22
     5.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  23
     5.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  23
     5.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  23
     5.7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  24
       5.7.1.  IRD Example . . . . . . . . . . . . . . . . . . . . .  24



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       5.7.2.  Basic Example . . . . . . . . . . . . . . . . . . . .  24
       5.7.3.  Incremental Updates Example . . . . . . . . . . . . .  26
   6.  Query Footprint Properties using ALTO Property Map Service  .  27
     6.1.  Representing Footprint Objects as Property Map Entities .  27
       6.1.1.  ASN Domain  . . . . . . . . . . . . . . . . . . . . .  28
       6.1.2.  COUNTRYCODE Domain  . . . . . . . . . . . . . . . . .  28
     6.2.  Representing CDNI Capabilities as Property Map Entity
           Properties  . . . . . . . . . . . . . . . . . . . . . . .  29
       6.2.1.  Defining Information Resource Media Type for Property
               Type cdni-capabilities  . . . . . . . . . . . . . . .  29
       6.2.2.  Intended Semantics of Property Type cdni-capabilities  29
     6.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  30
       6.3.1.  IRD Example . . . . . . . . . . . . . . . . . . . . .  30
       6.3.2.  Property Map Example  . . . . . . . . . . . . . . . .  30
       6.3.3.  Filtered Property Map Example . . . . . . . . . . . .  31
       6.3.4.  Incremental Updates Example . . . . . . . . . . . . .  33
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  34
     7.1.  application/alto-* Media Types  . . . . . . . . . . . . .  34
     7.2.  CDNI Metadata Footprint Type Registry . . . . . . . . . .  35
     7.3.  ALTO Entity Domain Type Registry  . . . . . . . . . . . .  36
     7.4.  ALTO Entity Property Type Registry  . . . . . . . . . . .  36
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  37
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  38
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  39
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  39
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  39
     11.2.  Informative References . . . . . . . . . . . . . . . . .  40
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  40

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 achieve the
   interconnection of CDNs: (1) the CDNI Request Routing Interface; (2)
   the CDNI Metadata Interface; (3) the CDNI Logging Interface; and (4)
   the CDNI Control Interface.

   Among the 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,
   the scope of the CDNI Request Routing Interface, therefore, contains



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   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].
   Since this document focuses on the first functionality (CDNI FCI),
   below is more details about it.

   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 CDNI FCI is defining objects describing
   the footprints and capabilities of a dCDN.  Such objects are already
   defined in [RFC8008].  A protocol to transport and update such
   objects between a uCDN and a dCDN, however, is not defined.  Hence,
   the scope of this document is to define such a protocol by
   introducing a new Application-Layer Traffic Optimization (ALTO)
   [RFC7285] service called "CDNI Advertisement Service".

   There are multiple benefits in using ALTO as a transport protocol, as
   discussed in Section 2.2.

   The rest of this document is organized as follows.  Section 2
   provides non-normative background on both CDNI FCI and ALTO.
   Section 3 introduces the most basic service, called "CDNI
   Advertisement Service", to realize CDNI FCI using ALTO.  Section 4
   demonstrates a key benefit of using ALTO: the ability to integrate
   CDNI FCI with ALTO network maps.  Such integration provides new
   granularity to describe footprints.  Section 5 introduces "Filtered
   CDNI Advertisement Service" to allow a uCDN to get footprints with
   given capabilities instead of getting the full resource, which can be
   large.  Section 6 further shows another benefit of using ALTO: the
   ability to query footprint properties using ALTO unified properties.
   In this way, a uCDN can effectively fetch capabilities of footprints
   in which it is interested.  IANA and security considerations are
   discussed in Section 7 and Section 8 respectively.

2.  Background

   The design of CDNI FCI transport using ALTO depends on the
   understanding of both FCI semantics and ALTO.  Hence, this document
   starts with a non-normative review for both.  The review uses the
   terminologies for CDNI as defined in [RFC6707], [RFC8006] and



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   [RFC8008]; those for ALTO as defined in [RFC7285] and
   [I-D.ietf-alto-unified-props-new].

2.1.  Semantics of FCI Advertisement

   [RFC8008] (CDNI "Footprint and Capabilities Semantics") 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 is referred to these two RFCs.

   o  Multiple types of mandatory-to-implement footprints (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.

   o  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.

   o  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.

   o  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 ASN(s), 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.  Multiple
      footprint constraints are additive, i.e., the advertisement of




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      different types of footprint narrows the dCDN candidacy
      cumulatively.

   o  Given that a large part of Footprint and Capabilities
      Advertisement may actually 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 in contracts between the
      participating CDNs.  In other words, the CDNI FCI is a means for a
      dCDN (downstream CDN) to provide changes/updates regarding a
      footprint and/or capabilities that it has prior agreed to serve in
      a contract with a uCDN (upstream CDN).  Hence, server push and
      incremental encoding will be necessary techniques.

2.2.  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 P2P applications [RFC5693].  However, ALTO can also be
   used for improving the request routing in CDNs.  In particular, the
   CDNI problem statement [RFC6707] explicitly mentions ALTO as a
   candidate protocol for "actual algorithms for selection of CDN or
   Surrogate by Request-Routing systems".

   The following reasons make ALTO a suitable candidate protocol for
   dCDN (downstream CDN) selection as part of CDNI request routing and,
   in particular, for an FCI protocol:

   o  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: 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.



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   o  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.

   o  Security: The identification between uCDNs and dCDNs is an
      important requirement.  ALTO maps can be signed and hence provide
      inherent integrity protection.  Please see Section 8.

   o  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.  A CDNI FCI
      interface based on ALTO would inherit this RESTful design.  Please
      see Section 3.

   o  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 this extensive error-handling framework.
      Please see Section 5.

   o  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 (see Section 6).

   o  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
      which 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
      [I-D.ietf-alto-incr-update-sse].

   o  Content Availability on Hosts: A dCDN might want to express CDN
      capabilities in terms of certain content types (e.g., codecs/
      formats, or content from certain content providers).  The new
      endpoint property for ALTO would enable a dCDN to make such
      information available to a uCDN.  This would enable a uCDN to
      determine whether a dCDN actually has the capabilities for a given
      type of content requested.



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   o  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 new endpoint properties, it would enable more
      sophisticated means for dCDN selection with ALTO.  ALTO Path
      Vector Extension [I-D.ietf-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 is based on the ALTO Information Service Framework
   which consists of multiple services, where all ALTO services are
   "provided through a common transport protocol, messaging structure
   and encoding, and transaction model" [RFC7285].  The ALTO protocol
   specification [RFC7285] 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 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.

3.1.  Media Type

   The media type of the CDNI Advertisement resource is "application/
   alto-cdni+json".

3.2.  HTTP Method

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

3.3.  Accept Input Parameters

   None.







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3.4.  Capabilities

   None.

3.5.  Uses

   The "uses" field SHOULD 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 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.

   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-




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   value, and footprints, where footprints are defined in
   Section 4.2.2.2 of [RFC8006].

   To be self-contained, below is a non-normative specification of
   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 not
   appearing, the ALTO client MUST understand that the capabilities in
   this BaseAdvertisementObject have the "global" coverage.

   Note: Further optimization of BaseAdvertisement objects 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>



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               ]
             },
             {

               "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.  There may be other
   documents extending BaseAdvertisementObject and additional CDNI



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   capabilities.  They are outside the scope of this document.  To
   support them, future documents can extend the specification defined
   in this document.

3.7.  Examples

3.7.1.  IRD Example

   Below is the information resource directory (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 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, and the other 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: 3571
    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"



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        },
        "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",



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            "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.  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



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     Host: alto.example.com
     Accept: application/alto-cdni+json,
             application/alto-error+json

     HTTP/1.1 200 OK
     Content-Length: 1235
     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" ]
               }
             ]
           },
           {
             "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",



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             "capability-value": {
               "acquisition-protocols": [
                 "https/1.1"
               ]
             },
             "footprints": [
               {
                 "footprint-type": "ipv4cidr",
                 "footprint-value": [ "203.0.113.0/24" ]
               }
             ]
           }
         ]
       }
     }


3.7.3.  Incremental Updates Example

   A benefit of using ALTO to provide CDNI Advertisement resources is
   that such resources can be updated using ALTO incremental updates.
   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 https/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: 92

    { "add": {
        "my-cdnifci-stream": {
          "resource-id": "my-default-cdnifci"
        }
      }



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    }

    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": [
    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



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    /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 PID to represent a group
   of IPv4 or IPv6 addresses which can be applied the same management
   policy.  The PID is an alternative to the pre-defined 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-
   vtag" field with a reference to this network map MUST be included in
   its response (see the example in Section 4.2.3).

4.2.  Examples

4.2.1.  IRD Example

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

4.2.2.  ALTO Network Map for CDNI Advertisement Example

   Below is an example network map whose resource id is "my-eu-netmap",
   and this map is referenced by the CDNI Advertisement example in
   Section 4.2.3.










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

    HTTP/1.1 200 OK
    Content-Length: 309
    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" ]
        },
        "germany": {
          "ipv4": [ "203.0.113.0/24" ]
        }
      }
    }


4.2.3.  ALTO PID Footprints in CDNI Advertisement

   This example shows a CDNI Advertisement resource that depends on a
   network map described in Section 4.2.2.




















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    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: 738
    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" ]
              }
            ]
          }
        ]
      }
    }


4.2.4.  Incremental Updates Example

   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 "south-france" from the footprints of the
   https/1.1 acquisition protocol capability.



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     POST /updates/cdnifci HTTP/1.1
     Host: alto.example.com
     Accept: text/event-stream,application/alto-error+json
     Content-Type: application/alto-updatestreamparams+json
     Content-Length: 183

     { "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",



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     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

   Section 3 and Section 4 describe CDNI Advertisement Service which 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.

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:









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

      object {
          [CDNIFCICapability 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-fci-capabilities:  A list of CDNI capabilities defined in
      Section 5.1 of [RFC8008] for which footprints are to be returned.
      If a list is empty or not appearing, the ALTO server MUST
      interpret it as a request for the full CDNI Advertisement
      resource.  The ALTO server MUST interpret entries appearing in a
      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

   None.

5.5.  Uses

   Same to the "uses" field of the CDNI Advertisement resource (see
   Section 3.5).

5.6.  Response

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

   Specifically, a filtered CDNI Advertisement request is invalid if:

   o  the value of "capability-type" is null;

   o  the value of "capability-value" is null;



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   o  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 CDNI Advertisement resource MUST contain only
   BaseAdvertisementObject objects whose CDNI capability object is the
   superset of one of CDNI capability object in "cdni-fci-capabilities".
   Specifically, that a CDNI capability object A is the superset of
   another CDNI capability object B means that these two CDNI capability
   objects have the same capability type and mandatory properties in
   capability value of A MUST include mandatory properties in capability
   value of B semantically.  See Section 5.7.2 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

5.7.1.  IRD Example

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

5.7.2.  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 BaseAdvertisementObjects 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



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

     HTTP/1.1 200 OK
     Content-Length: 571
     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" ]
               }
             ]
           }
         ]
       }
     }









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5.7.3.  Incremental Updates Example

   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".  So 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",



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     data:     "value": "a10ce8b059740b0b2e3f8eb1d4785acd42231bfe"
     data:   },
     data:   { "op": "add",
     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
   [I-D.ietf-alto-unified-props-new].  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
   [I-D.ietf-alto-unified-props-new] 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:

   o  According to [I-D.ietf-alto-unified-props-new], "ipv4" and "ipv6"
      are two predefined entity domain types, which can be used to
      represent "ipv4cidr" and "ipv6cidr" footprints respectively.




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   o  "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.

   o  However, no existing entity domain type can represent "asn" and
      "countrycode" footprints.  To represent footprint-type "asn" and
      "countrycode", this document registers two new domains in
      Section 7 in addition to the ones in
      [I-D.ietf-alto-unified-props-new].

   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"


6.1.1.  ASN Domain

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

6.1.1.1.  Entity Domain Type

   asn

6.1.1.2.  Domain-Specific Entity Identifiers

   The entity identifier of an entity in an asn domain is encoded as a
   string consisting of the characters "as" (in lowercase) followed by
   the Autonomous System Number [RFC6793].

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.





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6.1.2.1.  Entity Domain Type

   countrycode

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-capablities" 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 to define
   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

   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 an JSON object as
   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 that are
   provided by the defining CDNI Advertisement resource and the
   represented footprint object of this entity are in their footprint
   restrictions.



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6.3.  Examples

6.3.1.  IRD Example

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

6.3.2.  Property Map Example

   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": [



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            { "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"]}}]
        }
      }
    }


6.3.3.  Filtered Property Map Example

   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".


























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      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"
        }
      }
    }








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6.3.4.  Incremental Updates Example

   In this example, the 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: 337

    { "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:     },



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    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

7.1.  application/alto-* Media Types

   This document registers two additional ALTO media types, listed in
   Table 1.

   +----------------+-------------------------+------------------------+
   | Type           | Subtype                 | Specification          |
   +----------------+-------------------------+------------------------+
   | application    |              alto-      |              Section 3 |
   |                | cdni+json               |                        |
   | application    |              alto-      |              Section 5 |
   |                | cdnifilter+json         |                        |
   +----------------+-------------------------+------------------------+

                   Table 1: Additional ALTO Media Types.

   Type name:  application

   Subtype name:  This document registers multiple subtypes, as listed
      in Table 1.

   Required parameters:  n/a




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   Optional parameters:  n/a

   Encoding considerations:  Encoding considerations are identical to
      those specified for the "application/json" media type.  See
      [RFC7159].

   Security considerations:  Security considerations related to the
      generation and consumption of ALTO Protocol messages are discussed
      in Section 15 of [RFC7285].

   Interoperability considerations:  This document specifies formats of
      conforming messages and the interpretation thereof.

   Published specification:  This document is the specification for
      these media types; see Table 1 for the section documenting each
      media type.

   Applications that use this media type:  ALTO servers and ALTO clients
      either stand alone or are embedded within other applications.

   Additional information:

      Magic number(s):  n/a

      File extension(s):  This document uses the mime type to refer to
         protocol messages and thus does not require a file extension.

      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
      (mailto:iesg@ietf.org).

7.2.  CDNI Metadata Footprint Type Registry

   As proposed in Section 7.2 of [RFC8006], "CDNI Metadata Footprint
   Types" registry is requested.  A new footprint type is to be
   registered, listed in Table 2.





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      +----------------+---------------------+----------------------+
      | Footprint Type | Description         | Specification        |
      +----------------+---------------------+----------------------+
      | altopid        | A list of PID-names | Section 4 of RFCthis |
      +----------------+---------------------+----------------------+

                   Table 2: CDNI Metadata Footprint Type

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]

7.3.  ALTO Entity Domain Type Registry

   As proposed in Section 11.2 of [I-D.ietf-alto-unified-props-new],
   "ALTO Entity Domain Type Registry" is requested.  Two new entity
   domain types are to be registered, listed in Table 3.

   +-------------+-----------------------+-------------+---------------+
   | Identifier  | Entity Address        | Hierarchy & | Media Type of |
   |             | Encoding              | Inheritance | Defining      |
   |             |                       |             | Resource      |
   +-------------+-----------------------+-------------+---------------+
   | asn         |              See      | None        | None          |
   |             | Section 6.1.1.2 of    |             |               |
   |             | RFCthis               |             |               |
   | countrycode |              See      | None        | None          |
   |             | Section 6.1.2.2 of    |             |               |
   |             | RFCthis               |             |               |
   +-------------+-----------------------+-------------+---------------+

               Table 3: Additional ALTO Entity Domain Types

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]

7.4.  ALTO Entity Property Type Registry

   As proposed in Section 11.3 of [I-D.ietf-alto-unified-props-new],
   "ALTO Entity Property Type Registry" is required.  A new entity
   property type is to be registered, listed in Table 4.











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   +-------------------+------------------+----------------------------+
   | Identifier        | Intended         | Media Type of Defining     |
   |                   | Semantics        | Resource                   |
   +-------------------+------------------+----------------------------+
   | cdni-capabilities | Section 6.2 of   | application/alto-cdni+json |
   |                   | RFCthis          |                            |
   +-------------------+------------------+----------------------------+

               Table 4: Additional ALTO Entity Property Type

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]

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, additional security
   considerations should be included as follows:

   o  For authenticity and integrity of ALTO information, an attacker
      may disguise itself as an ALTO server for a dCDN, 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.

   o  For 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 which they should have to
      transfer.

   o  For confidentiality and privacy of ALTO information, footprint
      properties integrated with ALTO unified property may expose
      network location identifiers (e.g., IP addresses or fine-grained
      PIDs).

   o  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, to consume the bandwidth resources of that ALTO
      server.  It may also query filtered property map services with




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      many smaller individual footprints, to consume the computation
      resources of the ALTO server.

   Although protection strategies as described in Section 15 of
   [RFC7285] should be applied to address aforementioned security
   considerations, one additional information leakage risk introduced by
   this document could not be addressed by these strategies.  In
   particular, if a dCDN signs agreements with multiple uCDNs without
   any isolation, this dCDN may disclose extra information of one uCDN
   to another one.  In that case, one uCDN may redirect requests which
   should not have to be served by this dCDN to it.

   To reduce the risk, a dCDN should isolate full/filtered CDNI
   Advertisement resources for different uCDNs.  It could consider
   generating URIs of different full/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/filtered
   CDNI Advertisement resources in one of its IRDs.

9.  Acknowledgments

   The authors thank Matt Caulfield, Danny Alex Lachos Perez, Daryl
   Malas and Sanjay Mishra for their timely reviews and invaluable
   comments.

   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
   lnternational Standardisation Activities in ICT' ("StandlCT.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.







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10.  Contributors

   Mr. Xiao Shawn Lin is an author of an early version of this document,
   with many contributions.

11.  References

11.1.  Normative References

   [ISO3166-1]
              The International Organization for Standardization, "Codes
              for the representation of names of countries and their
              subdivisions -- Part 1: Country codes", ISO 3166-1:2013,
              2013.

   [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>.

   [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>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/info/rfc7159>.

   [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>.

   [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>.







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   [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>.

11.2.  Informative References

   [I-D.ietf-alto-incr-update-sse]
              Roome, W. and Y. Yang, "ALTO Incremental Updates Using
              Server-Sent Events (SSE)", draft-ietf-alto-incr-update-
              sse-22 (work in progress), March 2020.

   [I-D.ietf-alto-path-vector]
              Gao, K., Randriamasy, S., Yang, Y., and J. Zhang, "ALTO
              Extension: Path Vector", draft-ietf-alto-path-vector-10
              (work in progress), March 2020.

   [I-D.ietf-alto-unified-props-new]
              Roome, W., Randriamasy, S., Yang, Y., Zhang, J., and K.
              Gao, "Unified Properties for the ALTO Protocol", draft-
              ietf-alto-unified-props-new-11 (work in progress), March
              2020.

   [RFC7336]  Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
              "Framework for Content Distribution Network
              Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
              August 2014, <https://www.rfc-editor.org/info/rfc7336>.

   [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>.

Authors' Addresses

   Jan Seedorf
   HFT Stuttgart - Univ. of Applied Sciences
   Schellingstrasse 24
   Stuttgart  70174
   Germany

   Phone: +49-0711-8926-2801
   Email: jan.seedorf@hft-stuttgart.de






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   Y.R. Yang
   Yale University/PCL
   51 Prospect Street
   New Haven, CT  06511
   United States of America

   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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