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Versions: (draft-roome-alto-unified-props-new) 00 01 02 03 04 05 06 07 08 09 10

ALTO WG                                                         W. Roome
Internet-Draft                                            S. Randriamasy
Intended status: Standards Track                         Nokia Bell Labs
Expires: May 7, 2020                                             Y. Yang
                                                         Yale University
                                                                J. Zhang
                                                       Tongji University
                                                                  K. Gao
                                                      Sichuan University
                                                        November 4, 2019


                Unified Properties for the ALTO Protocol
                  draft-ietf-alto-unified-props-new-10

Abstract

   This document extends the Application-Layer Traffic Optimization
   (ALTO) Protocol [RFC7285] by generalizing the concept of "endpoint
   properties" to generic types of entities, and by presenting those
   properties as maps, similar to the network and cost maps in
   [RFC7285].

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 May 7, 2020.






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Copyright Notice

   Copyright (c) 2019 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  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Basic Features of the Unified Property Extension  . . . . . .   6
     2.1.  Entity  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Entity Domain . . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  Entity Property . . . . . . . . . . . . . . . . . . . . .   7
     2.4.  New information resource and media type: ALTO Property
           Map . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  Advanced Features of the Unified Property Extension . . . . .   8
     3.1.  Entity Identifier and Entity Domain . . . . . . . . . . .   8
     3.2.  Resource-Specific Entity Domain Name  . . . . . . . . . .   8
     3.3.  Resource-Specific Entity Property . . . . . . . . . . . .   9
     3.4.  Entity Hierarchy and Property Inheritance . . . . . . . .   9
     3.5.  Applicable Entity Domains and Properties in the Property
           Map Capabilities  . . . . . . . . . . . . . . . . . . . .  10
     3.6.  Connection between Resource-Specific Entity Domain/Entity
           Property Mapping and Information Resources  . . . . . . .  10
   4.  Protocol Specification: Basic Data Type . . . . . . . . . . .  11
     4.1.  Entity Domain . . . . . . . . . . . . . . . . . . . . . .  11
       4.1.1.  Entity Domain Type  . . . . . . . . . . . . . . . . .  11
       4.1.2.  Entity Domain Name  . . . . . . . . . . . . . . . . .  11
       4.1.3.  Entity Identifier . . . . . . . . . . . . . . . . . .  12
       4.1.4.  Hierarchy and Inheritance . . . . . . . . . . . . . .  13
     4.2.  Entity Property . . . . . . . . . . . . . . . . . . . . .  13
       4.2.1.  Entity Property Type  . . . . . . . . . . . . . . . .  13
       4.2.2.  Entity Property Name  . . . . . . . . . . . . . . . .  14
   5.  Entity Domain Types . . . . . . . . . . . . . . . . . . . . .  14
     5.1.  Internet Address Domain Types . . . . . . . . . . . . . .  14
       5.1.1.  IPv4 Domain . . . . . . . . . . . . . . . . . . . . .  15
       5.1.2.  IPv6 Domain . . . . . . . . . . . . . . . . . . . . .  15
       5.1.3.  Hierarchy and Inheritance of Internet Address Domains  15
     5.2.  PID Domain  . . . . . . . . . . . . . . . . . . . . . . .  17



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       5.2.1.  Entity Domain Type  . . . . . . . . . . . . . . . . .  17
       5.2.2.  Domain-Specific Entity Identifiers  . . . . . . . . .  17
       5.2.3.  Hierarchy and Inheritance . . . . . . . . . . . . . .  17
       5.2.4.  Relationship To Internet Addresses Domains  . . . . .  17
     5.3.  Internet Address Properties vs. PID Properties  . . . . .  17
   6.  Entity Domains and Property Mappings in Information Resources  18
     6.1.  Information Resource Export . . . . . . . . . . . . . . .  18
       6.1.1.  Resource-Specific Entity Domain Export  . . . . . . .  18
       6.1.2.  Entity Property Mapping Export  . . . . . . . . . . .  18
     6.2.  Network Map Resource  . . . . . . . . . . . . . . . . . .  19
       6.2.1.  Resource-Specific Entity Domain . . . . . . . . . . .  19
       6.2.2.  Entity Property Mapping . . . . . . . . . . . . . . .  19
     6.3.  Endpoint Property Resource  . . . . . . . . . . . . . . .  19
       6.3.1.  Resource-Specific Entity Domain . . . . . . . . . . .  19
       6.3.2.  Entity Property Mapping . . . . . . . . . . . . . . .  20
     6.4.  Property Map Resource . . . . . . . . . . . . . . . . . .  20
   7.  Property Map  . . . . . . . . . . . . . . . . . . . . . . . .  20
     7.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  20
     7.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  20
     7.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  20
     7.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  20
     7.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  21
     7.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  21
   8.  Filtered Property Map . . . . . . . . . . . . . . . . . . . .  22
     8.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  22
     8.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  22
     8.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  22
     8.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  23
     8.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  23
     8.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  23
   9.  Impact on Legacy ALTO Servers and ALTO Clients  . . . . . . .  25
     9.1.  Impact on Endpoint Property Service . . . . . . . . . . .  25
     9.2.  Impact on Resource-Specific Properties  . . . . . . . . .  25
     9.3.  Impact on Other Properties  . . . . . . . . . . . . . . .  26
   10. Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  26
     10.1.  Network Map  . . . . . . . . . . . . . . . . . . . . . .  26
     10.2.  Property Definitions . . . . . . . . . . . . . . . . . .  26
     10.3.  Information Resource Directory (IRD) . . . . . . . . . .  27
     10.4.  Property Map Example . . . . . . . . . . . . . . . . . .  30
     10.5.  Filtered Property Map Example #1 . . . . . . . . . . . .  30
     10.6.  Filtered Property Map Example #2 . . . . . . . . . . . .  31
     10.7.  Filtered Property Map Example #3 . . . . . . . . . . . .  33
     10.8.  Filtered Property Map Example #4 . . . . . . . . . . . .  34
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  35
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  36
     12.1.  application/alto-* Media Types . . . . . . . . . . . . .  36
     12.2.  ALTO Entity Domain Type Registry . . . . . . . . . . . .  37
       12.2.1.  Consistency Procedure between ALTO Address Type



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                Registry and ALTO Entity Domain Type Registry  . . .  38
       12.2.2.  ALTO Entity Domain Type Registration Process . . . .  39
     12.3.  ALTO Entity Property Type Registry . . . . . . . . . . .  40
     12.4.  ALTO Resource-Specific Entity Domain Registries  . . . .  41
       12.4.1.  Network Map  . . . . . . . . . . . . . . . . . . . .  41
       12.4.2.  Endpoint Property  . . . . . . . . . . . . . . . . .  41
     12.5.  ALTO Resource Entity Property Mapping Registries . . . .  41
       12.5.1.  Network Map  . . . . . . . . . . . . . . . . . . . .  42
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  42
   14. Normative References  . . . . . . . . . . . . . . . . . . . .  42
   Appendix A.  Scope of Property Map  . . . . . . . . . . . . . . .  43
     A.1.  Example Property Map  . . . . . . . . . . . . . . . . . .  44
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  45

1.  Introduction

   The ALTO protocol [RFC7285] introduces the concept of "properties"
   attached to "endpoint addresses", and defines the Endpoint Property
   Service (EPS) to allow ALTO clients to retrieve those properties.
   While useful, the EPS, as defined in [RFC7285], has at least three
   limitations.

   First, the EPS allows properties to be associated with only endpoints
   which are identified by individual communication addresses like IPv4
   and IPv6 addresses.  It is reasonable to think that collections of
   endpoints, as defined by CIDRs [RFC4632] or PIDs, may also have
   properties.  Furthermore, recent ALTO use cases show that properties
   of network flows [RFC7011] and routing elements [RFC7921] are also
   very useful.  Since the EPS cannot be extended to those generic
   entities, new services, with new request and response messages, would
   have to be defined for them.

   Second, the EPS only allows endpoints identified by global
   communication addresses.  However, an endpoint address may be a local
   IP address or an anycast IP address which is also not globally
   unique.  Additionally, a generic entity such as a PID may have an
   identifier that is not globally unique.  For example, a PID
   identifier may be used in several network maps, where in each network
   map, this PID identifier points to a different set of addresses.

   Third, the EPS is only defined as a POST-mode service.  Clients must
   request the properties for an explicit set of endpoint addresses.  By
   contrast, [RFC7285] defines a GET-mode cost map resource which
   returns all available costs, so a client can get a full set of costs
   once, and then processes costs lookups without querying the ALTO
   server.  [RFC7285] does not define a similar service for endpoint
   properties.  At first, a map of endpoint properties might seem
   impractical, because it could require enumerating the property value



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   for every possible endpoint.  However, in practice, it is highly
   unlikely that properties will be defined for every endpoint address.
   It is much more likely that properties may be defined for only a
   subset of endpoint addresses, and the specification of properties
   uses an aggregation representation to allow enumeration.  This is
   particularly true if blocks of endpoint addresses with a common
   prefix (e.g., a CIDR) have the same value for a property.  Entities
   in other domains may very well allow aggregated representation and
   hence be enumerable as well.

   To address the three limitations, this document specifies a protocol
   extension for defining and retrieving ALTO properties:

   o  The first limitation is adressed by introducing a generic concept
      called ALTO Entity, which generalizes an endpoint and may
      represent a PID, a network element, a cell in a cellular network,
      an abstracted network element as defined in [REF path-vector], or
      other physical or logical objects used by ALTO.  Each entity is
      included in a collection called ALTO Entity Domain.  Also, each
      Entity Domain includes only one type of entities.  Thus, each
      entity domain has a type.

   o  The second limitation is addressed by using resource-specific
      entity domains.  A resource-specific entity domain contains
      entities defined and identified with respect to a given ALTO
      information resource.  For example, an entity domain containing
      PIDs is identified w.r.t. the network map in which these PIDs are
      defined.  Likewise an entity domain containing local IP addresses
      may be defined w.r.t. a local network.

   o  Finally, the third limitation is addressed by defining two new
      types of ALTO information resources: Property Map, detailed in
      Section 7 and Filtered Property Map, detailed in Section 8.  The
      former is a GET-mode resource which returns the property values
      for all entities in some entity domains, and is analogous to a
      network map or a cost map in [RFC7285].  The latter is a POST-mode
      resource which returns the values for a set of properties and
      entities requested by the client, and is analogous to a filtered
      network map or a filtered cost map.

   This approach is extensible, because new entity domain types can be
   defined without revising the protocol specification defined in this
   document.  In the same way, new cost metrics and new endpoint
   properties can be defined without revising the protocol specification
   defined in [RFC7285].






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   This document subsumes the Endpoint Property Service defined in
   [RFC7285], although that service may be retained for legacy clients
   (see Section 9).

2.  Basic Features of the Unified Property Extension

   The purpose of this extension is to convey properties on objects that
   extend ALTO Endpoints and are called ALTO Entities, entities for
   short.  This section introduces the basic features involved in ALTO
   Entity Property Maps.

2.1.  Entity

   The concept of ALTO Entity generalizes the concept of an ALTO
   Endpoint defined in Section 2.1 of [RFC7285].  An entity is an object
   that can be an endpoint and is identified by its network address, but
   can also be an object that has a defined mapping to a set of one or
   more network addresses or is even not related to any network address.

   Examples of eligible entities are:

   o  a PID, defined in [RFC7285], that has a provider defined human-
      readable abstract identifier defined by an ALTO network map, which
      maps a PID to a set of ipv4 and ipv6 addresses;

   o  an autonomous system (AS), that has an AS number (ASN) as its
      identifier and maps to a set of ipv4 and ipv6 addresses;

   o  a region representing a country, that is identified by its country
      code defined by ISO 3166 and maps to a set of cellular addresses;

   o  a TCP/IP network flow, that has a server defined identifier
      consisting of the defining TCP/IP 5-Tuple, which is an example
      that all endpoints are entities while not all entities are
      endpoints;

   o  a routing element, that is specified in [RFC7921] and includes
      routing capability information;

   o  an abstract network element, that has a server defined identifier
      and represents a network node, link or their aggregation.

2.2.  Entity Domain

   An entity domain defines a set of entities of same type.  This type
   is also called the type of the entity domain.  Thus, an entity domain
   type defines the type semantics and the identifier format of its
   entities.  An entity domain also has a name.  Very often the name and



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   type of an entity domain are the same.  Example of such entity
   domains are: "ipv4", "pid", which are defined in Section 5.1 and
   Section 5.2.

   Using entity domains, the ALTO property map capabilities indicate on
   which entity domains an ALTO client can query properties.

2.3.  Entity Property

   An entity property defines a property of an entity.  It is similar to
   the endpoint property defined by Section 7.1 of [RFC7285].  It can be
   network-aware but can also convey network-agnostic information such
   as geographical location.

   For example:

   o  an entity in the "ipv4" domain may have a property whose value is
      an Autonomous System (AS) number indicating the AS that owns this
      IPv4 address,

   o  an entity in the "pid" domain may have a property that indicates
      the central geographical location of endpoints it includes.

   It should be noted that some objects may be both entities and
   properties.  For example, a PID may be both a property of an "ipv4"
   entity and an entity on which a Client may query properties such as
   geographical location.

2.4.  New information resource and media type: ALTO Property Map

   The Unified Property extension introduces a new ALTO information
   resource named Property Map. An ALTO property map provides a set of
   properties on a set of entities.  These entities may be of different
   types.  For example, an ALTO property map may define the ASN property
   for both "ipv4" and "ipv6" type of entities.

   The present extension also introduces a new media type.

   This document uses the same definition of the information resource as
   defined by [RFC7285].  Each information resource usually has a JSON
   format representation following a specific schema defined by its
   media type.  In the present case, an ALTO property map resource is
   represented by a JSON object of type InfoResourcePropertyMap and
   defined by the media type "application/alto-propmap+json".

   A Property Map can be queried as a GET-mode resource, thus conveying
   values of all properties on all entities indicated in its




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   capabilities.  It can also be queried as a POST-mode resource, thus
   conveying a selection of properties on a selection of entities.

3.  Advanced Features of the Unified Property Extension

3.1.  Entity Identifier and Entity Domain

   In [RFC7285], an endpoint has an identifier explicitly associated to
   the "ipv4" or "ipv6" address domain.  Examples are "ipv4:192.0.2.14"
   and "ipv6:2001:db8::12".  In this extension, an entity domain
   characterizes the type semantics and identifier format of its
   entities and the identifier of an entity is explicitly associated to
   its entity domain.  For instance: an entity that is an endpoint with
   an IPv4 address will have an identifier associated with domain
   "ipv4", like "ipv4:192.0.2.14"; an entity which is a PID will have an
   identifier associated with domain "pid", like "pid:mypid10".

   In this document, an entity must be owned by exactly one entity
   domain.  And an entity identifier must point to exactly one entity.
   If two entities in two different entity domains refer to the same
   physical or logical object, they are treated as different entities,
   as it is the case for an endpoint having an IPv4 and IPv6 address.

3.2.  Resource-Specific Entity Domain Name

   Some entities are defined and identified in a unique and global way.
   This is the case for instance for entities that are endpoints
   identified by a routable IPv4 or IPv6 address.  The entity domain for
   such entities can be globally defined and named "ipv4" or "ipv6".
   Those entity domains are also called resource-agnostic entity domains
   in this document, as they are not associated to any specific ALTO
   information resources.

   Some other entities and entity types are only defined relatively to a
   given information resource.  This is the case for entities of domain
   "pid", that can only be understood with respect to the network map
   where they are defined.  For example: a PID named "mypid10" may be
   defined by a set S1 of IP adresses, in an information resource of
   type Network Map and named "netmap1".  Another Network Map "netmap2"
   may use the same name "mypid10" and define it with another set S2 of
   IP addresses.  The identifier "pid:mypid10" may thus point to
   different objects because the information on the originating
   information resource is lost.  The reason is that "pid" denotes an
   entity domain type rather than an unambiguous identifier.

   To solve this ambiguity, the present extension introduces the concept
   of resources-specific entity domain.  This concept applies to domains
   where entities are defined relatively to a given information



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   resource.  It can also apply to domains of entities that are defined
   locally, such as local networks of objects identified with a local
   IPv4 address.

   In such cases, an entity domain name is explicitly associated with an
   identifier of the information resource where these entities are
   defined.  Using a resource-specific entity domain name, an ALTO
   Property Map may unambiguously indicate entity domains of the same
   type, on which entity properties may be queried.  Example resource-
   specific entity domain names may look like: "netmap1.pid" or
   "netmap2.pid".  This allows to identify two distinct PID entities
   such as "netmap1.pid:mypid10" or "netmap1.pid:mypid10".  Resource-
   specific entity domain name will be specified in Section 4.1.2.

3.3.  Resource-Specific Entity Property

   An entity may have properties of same type, whose values are
   associated to different information resources.  For instance, entity
   "192.0.2.34" defined in the "ipv4" domain may have two "pid"
   properties defined in two different network maps "netmap1" and
   "netmap2".  These properties will likely have different values in
   "netmap1" and "netmap2".  To distinguish between them, this document
   uses the same approach proposed as in Section 10.8.1 of [RFC7285],
   which is called "Resource-Specific Entity Property".  When a property
   value depends on a given information resource, the identifier of the
   property must be explicitly associated with the information resource
   that defines it.

   For example, the "pid" property queried on entity "ipv4:192.0.2.34"
   and defined in "netmap1" and "netmap2" respectively, may be named
   "netmap1.pid" and "netmap2.pid".  This allows a Client to get a
   property of the same type but defined in different information
   resources in a single query.  Specifications are provided in
   Section 4.2.

3.4.  Entity Hierarchy and Property Inheritance

   Enumerating all individual entities is inefficient.  Some types of
   entities have a hierarchy format, for example CIDRs, which stand for
   sets of individual entities.  A property P may not be defined for a
   specific entity E, but P may be defined for a set of entities
   containing E.  In which case, E inherits the value of P.  For entity
   domains organized in a hierarchy, this can significantly reduce the
   size of Property Maps and Client query payload.  To reduce the size
   of the property map representation, this document introduces, when
   applicable, an approach called "Property Inheritance".  Individual
   entities can inherit property values from their upper hierarchical
   levels.  This will be specified in Section 4.1.4.



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3.5.  Applicable Entity Domains and Properties in the Property Map
      Capabilities

   This section explains how the IRD capabilities of a Property Map
   unambiguously expose what type of properties on what entity domains a
   Client can query.  A field called "mapping" enumerates the entity
   domains supported by the Property Map; For each entity domain, a list
   of applicable properties is provided.  An example can be found in
   Section 10.3.  Using resource-agnostic or resource-specific entity
   domains and properties allows to formulate compact an unambiguous
   entity property queries relating to one or more information
   resources, in particular:

   o  avoid a Client to query a property on entity domains on which P is
      not defined,

   o  query for en entity E property values defined in different
      information resources,

   o  query a property P on entities E defined in different information
      resources.

   Specifications will be provided in Section 7.4.

3.6.  Connection between Resource-Specific Entity Domain/Entity Property
      Mapping and Information Resources

   Although the IRD capabilities of a Property Map can expose the
   supported mappings in this property map, it may still not be clear to
   a Client what a resource-specific entity domain is, and what an
   applicable resource-specific entity property means, as those concepts
   are not defined in other ALTO information resources.  For example, a
   Client should understand that:

   o  a local IPv4 entity domain "netmap1.ipv4" includes the IPv4
      addresses appearing in the "ipv4" field of the endpoint address
      group of each PID in the network map "netmap1";

   o  a "netmap1.pid" property of an IPv4 entity "ipv4:192.0.1.1"
      indicates the PID defined by the network map "netmap1" and
      including the IPv4 address "ipv4:192.0.1.1" in its endpoint
      address group.

   To help the client understanding these connections, this document
   requests two new IANA registries for each information resource to
   define the connection to each supported resource-specific entity
   domain and entity property mapping respectively.  Such a connection
   is called "Information Resource Export", to explain what is an



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   resource-specific entity domain or an entity property mapping
   exported by an information resource.  Examples of "Information
   Resource Exports" of existing ALTO information resources are provided
   in Section 6.  Specifications are provided in Section 6.1.  The
   details of these new IANA registries are provided in Section 12.4 and
   Section 12.5.

4.  Protocol Specification: Basic Data Type

4.1.  Entity Domain

4.1.1.  Entity Domain Type

   An entity domain has a type, which is defined by a string that MUST
   be no more than 64 characters, and MUST NOT contain characters other
   than US-ASCII alphanumeric characters (U+0030-U+0039, U+0041-U+005A,
   and U+0061-U+007A), hyphen ("-", U+002D), and low line ("_", U+005F).
   For example, the strings "ipv4", "ipv6", and "pid" are valid entity
   domain types.

   The type EntityDomainType is used in this document to denote a JSON
   string confirming to the preceding requirement.

   An entity domain type defines the semantics of a type of entity
   domains.  Each entity domain type MUST be registered with the IANA.
   The format of the entity identifiers (see Section 4.1.3) in that type
   of entity domains, as well as any hierarchical or inheritance rules
   (see Section 4.1.4) for those entities, MUST be specified at the same
   time.

4.1.2.  Entity Domain Name

   Each entity domain is identified by an entity domain name, a string
   of the following format:

   EntityDomainName ::= [ [ ResourceID ] '.' ] EntityDomainType

   This document distinguish three types of entity domains: resource-
   specific entity domains, self-defined entity domain and resource-
   agnostic entity domains.  Their entity domain names are derived as
   follows.

   Each ALTO information resource MAY define a resource-specific entity
   domain (which could be empty) in a given entity domain type.  A
   resource-specific entity domain is identified by an entity domain
   name derived as follows.  It MUST start with a resource ID using the
   ResourceID type defined in [RFC7285], followed by the "." separator
   (U+002E), followed by an EntityDomainType typed string.  For example,



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   if an ALTO server provides two network maps "netmap-1" and "netmap-
   2", they can define two different "pid" domains identified by
   "netmap-1.pid" and "netmap-2.pid" respectively.  To be simplified, in
   the scope of a specific information resource, the resource-specific
   entity domain defined by itself can be identified by the "."
   EntityDomainTyep without the ResourceID.

   When the associated information resource of a resource-specific
   entity domain is the current information resource itself, this
   resource-specific entity domain is a self-defined entity domain, and
   its ResourceID SHOULD be ignored from its entity domain name.

   Given a set of ALTO information resources, there MAY be a resource-
   agnostic entity domain in a given entity domain type amongst them.  A
   resource-agnostic entity domain is simply identified by its entity
   domain type.  For example, given two network maps "net-map-1" and
   "net-map-2", "ipv4" and "ipv6" identify two resource-agnostic
   Internet address entity domains (see Section 5.1) between them.

   Note that the "." separator is not allowed in EntityDomainType and
   hence there is no ambiguity on whether an entity domain name refers
   to a global entity domain or a resource-specific entity domain.

4.1.3.  Entity Identifier

   Entities in an entity domain are identified by entity identifiers
   (EntityID) of the following format:

   EntityID ::= EntityDomainName ':' DomainTypeSpecificEntityID

   Examples from the Internet address entity domains include individual
   IP addresses such as "net1.ipv4:192.0.2.14" and
   "net1.ipv6:2001:db8::12", as well as address blocks such as
   "net1.ipv4:192.0.2.0/26" and "net1.ipv6:2001:db8::1/48".

   The format of the second part of an entity identifier depends on the
   entity domain type, and MUST be specified when registering a new
   entity domain type.  Identifiers MAY be hierarchical, and properties
   MAY be inherited based on that hierarchy.  Again, the rules defining
   any hierarchy or inheritance MUST be defined when the entity domain
   type is registered.

   The type EntityID is used in this document to denote a JSON string
   representing an entity identifier in this format.

   Note that two entity identifiers with different textual
   representations may refer to the same entity, for a given entity
   domain.  For example, the strings "net1.ipv6:2001:db8::1" and



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   "net1.ipv6:2001:db8:0:0:0:0:0:1" refer to the same entity in the
   "ipv6" entity domain.

4.1.4.  Hierarchy and Inheritance

   To make the representation efficient, some types of entity domains
   MAY allow the ALTO client/server to use a hierarchical format entity
   identifier to represent a block of individual entities. e.g., In an
   IPv4 domain "net1.ipv4", a cidr "net1.ipv4:192.0.2.0/26" represents
   64 individual IPv4 entities.  In this case, the corresponding
   property inheritance rule MUST be defined for the entity domain type.
   The hierarchy and inheritance rule MUST have no ambiguity.

4.2.  Entity Property

   Each entity property has a type to indicate the encoding and the
   semantics of the value of this entity property, and has a name to be
   identified.  One entity MAY have multiple properties in the same
   type.

4.2.1.  Entity Property Type

   The type EntityPropertyType is used in this document to indicate a
   string denoting an entity property type.  The string MUST be no more
   than 32 characters, and it MUST NOT contain characters other than US-
   ASCII alphanumeric characters (U+0030-U+0039, U+0041-U+005A, and
   U+0061-U+007A), the hyphen ("-", U+002D), the colon (":", U+003A), or
   the low line ('_', U+005F).

   Each entity property type MUST be registered with the IANA.  The
   intended semantics of the entity property type MUST be specified at
   the same time.

   To distinguish with the endpoint property type, the entity property
   type has the following features.

   o  Some entity property types may be applicable to entities in only
      particular types of entity domains, not all.  For example, the
      "pid" property is not applicable to entities in a "pid" typed
      entity domain, but is applicable to entities in the "ipv4" or
      "ipv6" domains.

   o  The intended semantics of the value of an entity property may also
      depend on the entity domain type of this entity.  For example,
      suppose that the "geo-location" property is defined as the
      coordinates of a point, encoded as (say) "latitude longitude
      [altitude]."  When applied to an entity that represents a specific
      host computer, identified by an address in the "ipv4" or "ipv6"



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      entity domain, the property defines the host's location.  However,
      when applied to an entity in a "pid" domain, the property would
      indicate the location of the center of all hosts in this "pid"
      entity.

4.2.2.  Entity Property Name

   Each entity property is identified by an entity property name, which
   is a string of the following format:

   EntityPropertyName ::= [ ResourceID ] '.' EntityPropertyType

   Similar to the endpoint property type defined in Section 10.8 of
   [RFC7285], each entity property may be defined by either the property
   map itself (self-defined) or some other specific information resource
   (resource-specific).

   The entity property name of a resource-specific entity property
   starts with a string of the type ResourceID defined in [RFC7285],
   followed by the "." separator (U+002E) and a EntityDomainType typed
   string.  For example, the "pid" properties of an "ipv4" entity
   defined by two different maps "net-map-1" and "net-map-2" are
   identified by "net-map-1.pid" and "net-map-2.pid" respectively.

   When the associated information resource of the entity property is
   the current information resource itself, the ResourceID in the
   property name SHOULD be ignored.  For example, the ".asn" property of
   an "ipv4" entity indicates the AS number of the AS which this IPv4
   address is owned by.

5.  Entity Domain Types

   This document defines three entity domain types.  The definition of
   each entity domain type below includes the following: (1) entity
   domain type name, (2) entity domain-specific entity identifiers, and
   (3) hierarchy and inheritance semantics.  Since a global entity
   domain type defines a single global entity domain, we say entity
   domain instead of entity domain type.

5.1.  Internet Address Domain Types

   The document defines two entity domain types (IPv4 and IPv6) for
   Internet addresses.  Both types are global entity domain types and
   hence define a corresponding global entity domain as well.  Since the
   two domains use the same hierarchy and inheritance semantics, we
   define the semantics together, instead of repeating for each.





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5.1.1.  IPv4 Domain

5.1.1.1.  Entity Domain Type

   ipv4

5.1.1.2.  Domain-Specific Entity Identifiers

   Individual addresses are strings as specified by the IPv4Addresses
   rule of Section 3.2.2 of [RFC3986]; blocks of addresses are prefix-
   match strings as specified in Section 3.1 of [RFC4632].  To define
   properties, an individual Internet address and the corresponding
   full-length prefix are considered aliases for the same entity.  Thus
   "ipv4:192.0.2.0" and "ipv4:192.0.2.0/32" are equivalent.

5.1.2.  IPv6 Domain

5.1.2.1.  Entity Domain Type

   ipv6

5.1.2.2.  Domain-Specific Entity Identifiers

   Individual addresses are strings as specified by Section 4 of
   [RFC5952]; blocks of addresses are prefix-match strings as specified
   in Section 7 of [RFC5952].  To define properties, an individual
   Internet address and the corresponding 128-bit prefix are considered
   aliases for the same entity.  That is, "ipv6:2001:db8::1" and
   "ipv6:2001:db8::1/128" are equivalent, and have the same set of
   properties.

5.1.3.  Hierarchy and Inheritance of Internet Address Domains

   Both Internet address domains allow property values to be inherited.
   Specifically, if a property P is not defined for a specific Internet
   address I, but P is defined for some block C which prefix-matches I,
   then the address I inherits the value of P defined for block C.  If
   more than one such block defines a value for P, I inherits the value
   of P in the block with the longest prefix.  It is important to notice
   that this longest prefix rule will ensure no multiple inheritances,
   and hence no ambiguity.

   Address blocks can also inherit properties: if a property P is not
   defined for a block C, but is defined for some block C' which covers
   all IP addresses in C, and C' has a shorter mask than C, then block C
   inherits the property from C'.  If there are several such blocks C',
   C inherits from the block with the longest prefix.




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   As an example, suppose that a server defines a property P for the
   following entities:

                             ipv4:192.0.2.0/26: P=v1
                             ipv4:192.0.2.0/28: P=v2
                             ipv4:192.0.2.0/30: P=v3
                             ipv4:192.0.2.0:    P=v4

                    Figure 1: Defined Property Values.

   Then the following entities have the indicated values:

                         ipv4:192.0.2.0:    P=v4
                         ipv4:192.0.2.1:    P=v3
                         ipv4:192.0.2.16:   P=v1
                         ipv4:192.0.2.32:   P=v1
                         ipv4:192.0.2.64:   (not defined)
                         ipv4:192.0.2.0/32: P=v4
                         ipv4:192.0.2.0/31: P=v3
                         ipv4:192.0.2.0/29: P=v2
                         ipv4:192.0.2.0/27: P=v1
                         ipv4:192.0.2.0/25: (not defined)

                   Figure 2: Inherited Property Values.

   An ALTO server MAY explicitly indicate a property as not having a
   value for a particular entity.  That is, a server MAY say that
   property P of entity X is "defined to have no value", instead of
   "undefined".  To indicate "no value", a server MAY perform different
   behaviours:

   o  If that entity would inherit a value for that property, then the
      ALTO server MUST return a "null" value for that property.  In this
      case, the ALTO client MUST recognize a "null" value as "no value"
      and "do not apply the inheritance rules for this property."

   o  If the entity would not inherit a value, then the ALTO server MAY
      return "null" or just omit the property.  In this case, the ALTO
      client cannot infer the value for this property of this entity
      from the Inheritance rules.  So the client MUST interpret that
      this property has no value.

   If the ALTO server does not define any properties for an entity, then
   the server MAY omit that entity from the response.







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5.2.  PID Domain

   The PID domain associates property values with the PIDs in a network
   map.  Accordingly, this entity domain always depends on a network
   map.

5.2.1.  Entity Domain Type

   pid

5.2.2.  Domain-Specific Entity Identifiers

   The entity identifiers are the PID names of the associated network
   map.

5.2.3.  Hierarchy and Inheritance

   There is no hierarchy or inheritance for properties associated with
   PIDs.

5.2.4.  Relationship To Internet Addresses Domains

   The PID domain and the Internet address domains are completely
   independent; the properties associated with a PID have no relation to
   the properties associated with the prefixes or endpoint addresses in
   that PID.  An ALTO server MAY choose to assign some or all properties
   of a PID to the prefixes in that PID.

   For example, suppose "PID1" consists of the prefix
   "ipv4:192.0.2.0/24", and has the property "P" with value "v1".  The
   Internet address entities "ipv4:192.0.2.0" and "ipv4:192.0.2.0/24",
   in the IPv4 domain MAY have a value for the property "P", and if they
   do, it is not necessarily "v1".

5.3.  Internet Address Properties vs. PID Properties

   Because the Internet address and PID domains are completely separate,
   the question may arise as to which entity domain is the best for a
   property.  In general, the Internet address domains are RECOMMENDED
   for properties that are closely related to the Internet address, or
   are associated with, and inherited through, blocks of addresses.

   The PID domain is RECOMMENDED for properties that arise from the
   definition of the PID, rather than from the Internet address prefixes
   in that PID.

   For example, because Internet addresses are allocated to service
   providers by blocks of prefixes, an "ISP" property would be best



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   associated with the Internet address domain.  On the other hand, a
   property that explains why a PID was formed, or how it relates a
   provider's network, would best be associated with the PID domain.

6.  Entity Domains and Property Mappings in Information Resources

6.1.  Information Resource Export

   Each information resource MAY export a set of entity domains and
   entity property mappings.

6.1.1.  Resource-Specific Entity Domain Export

   Each type of information resource MAY export several types of entity
   domains.  For example, a network map resource defines a "pid" domain,
   a "ipv4" domain and a "ipv6" domain (which may be empty).

   When a new ALTO information resource type is registered, if this type
   of information resource can export an existing type of entity domain,
   the corresponding document MUST define how to export such type of
   entity domain from such type of information resource.

   When a new entity domain type is defined, if an existing type of
   information resource can export an entity domain in this entity
   domain type, the corresponding document MUST define how to export
   such type of entity domain from such type of information resource.

6.1.2.  Entity Property Mapping Export

   For each entity domain which could be exported by an information
   resource, this information resource MAY also export some mapping from
   this entity domain to some entity property.  For example, a network
   map resource can map an "ipv4" entity to its "pid" property.

   When a new ALTO information resource type is registered, if this type
   of information resource can export an entity domain in an existing
   entity domain type, and map entities in this entity domain to an
   existing type of entity property, the corresponding document MUST
   define how to export such type of an entity property.

   When a new ALTO entity domain type or a new entity property type is
   defined, if an existing type of resource can export an entity domain
   in this entity domain type, and map entities in this entity domain to
   this type of entity property, the corresponding document MUST define
   how to export such type of an entity property.






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6.2.  Network Map Resource

   The ALTO network map resource defined by the media type "application/
   alto-networkmap+json" exports the following types of entity domains
   and entity property mappings.

6.2.1.  Resource-Specific Entity Domain

   An ALTO network map resource defines a "pid" domain, an "ipv4" domain
   and an "ipv6" domain by follows:

   o  The defined "pid" domain includes all PIDs in keys of the
      "network-map" object.

   o  The defined "ipv4" domain includes all IPv4 addresses appearing in
      the "ipv4" field of the endpoint address group of each PID.

   o  The defined "ipv6" domain includes all IPv6 addresses appearing in
      the "ipv6" field of the endpoint address group of each PID.

6.2.2.  Entity Property Mapping

   For each of the preceding entity domains, an ALTO network map
   resource provides the properties mapping as follows:

   ipv4 -> pid:  An "networkmap" typed resource can map an "ipv4" entity
      to a "pid" property whose value is a PID defined by this
      "networkmap" resource and including the IPv4 address of this
      entity.

   ipv6 -> pid:  An "networkmap" typed resource can map an "ipv6" entity
      to a "pid" property whose value is a PID defined by this
      "networkmap" resource and including the IPv6 address of this
      entity.

6.3.  Endpoint Property Resource

   The ALTO endpoint property resource defined by the media type
   "application/alto-endpointprop+json" exports the following types of
   entity domains and entity property mappings.

6.3.1.  Resource-Specific Entity Domain

   An ALTO endpoint property resource defined an "ipv4" domain and an
   "ipv6" domain by follows:

   o  The defined "ipv4" domain includes all IPv4 addresses appearing in
      keys of the "endpoint-properties" object.



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   o  The defined "ipv6" domain includes all IPv6 addresses appearing in
      keys of the "endpoint-properties" object.

6.3.2.  Entity Property Mapping

   For each of the preceding entity domains, an ALTO endpoint property
   resource exports the properties mapping from it to each supported
   global endpoint property.  The property value is the corresponding
   global endpoint property value in the "endpiont-properties" object.

6.4.  Property Map Resource

   To avoid the nested reference and its potential complexity, this
   document does not specify the export rule of resource-specific entity
   domain and entity property mapping for the ALTO property map resource
   defined by the media type "application/alto-propmap+json" (see
   Section 7.1).

7.  Property Map

   A property map returns the properties defined for all entities in one
   or more domains, e.g., the "location" property of entities in "pid"
   domain, and the "ASN" property of entities in "ipv4" and "ipv6"
   domains.

   Section 10.4 gives an example of a property map request and its
   response.

7.1.  Media Type

   The media type of a property map is "application/alto-propmap+json".

7.2.  HTTP Method

   The property map is requested using the HTTP GET method.

7.3.  Accept Input Parameters

   None.

7.4.  Capabilities

   The capabilities are defined by an object of type
   PropertyMapCapabilities:







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       object {
         EntityPropertyMapping mappings;
       } PropertyMapCapabilities;

       object-map {
         EntityDomainName -> EntityPropertyName<1..*>;
       } EntityPropertyMapping

   with fields:

   mappings:  A JSON object whose keys are names of entity domains and
      values are the supported entity properties of the corresponding
      entity domains.

7.5.  Uses

   The "uses" field of a property map resource in an IRD entry specifies
   dependent resources of this property map.  It is an array of the
   resource ID(s) of the resource(s).

7.6.  Response

   If the entity domains in this property map depend on other resources,
   the "dependent-vtags" field in the "meta" field of the response MUST
   be an array that includes the version tags of those resources, and
   the order MUST be consistent with the "uses" field of this property
   map resource.  The data component of a property map response is named
   "property-map", which is a JSON object of type PropertyMapData,
   where:

       object {
         PropertyMapData property-map;
       } InfoResourceProperties : ResponseEntityBase;

       object-map {
         EntityID -> EntityProps;
       } PropertyMapData;

       object {
         EntityPropertyName -> JSONValue;
       } EntityProps;

   The ResponseEntityBase type is defined in Section 8.4 of [RFC7285].

   Specifically, a PropertyMapData object has one member for each entity
   in the property map.  The entity's properties are encoded in the
   corresponding EntityProps object.  EntityProps encodes one name/value
   pair for each property, where the property names are encoded as



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   strings of type PropertyName.  A protocol implementation SHOULD
   assume that the property value is either a JSONString or a JSON
   "null" value, and fail to parse if it is not, unless the
   implementation is using an extension to this document that indicates
   when and how property values of other data types are signaled.

   For each entity in the property map:

   o  If the entity is in a resource-specific entity domain, the ALTO
      server SHOULD only return self-defined properties and resource-
      specific properties which depend on the same resource as the
      entity does.  The ALTO client SHOULD ignore the resource-specific
      property in this entity if their mapping is not registered in the
      ALTO Resource Entity Property Transfer Registry of the type of the
      corresponding resource.

   o  If the entity is in a shared entity domain, the ALTO server SHOULD
      return self-defined properties and all resource-specific
      properties defined for all resource-specific entities which have
      the same domain-specific entity identifier as this entity does.

   For efficiency, the ALTO server SHOULD omit property values that are
   inherited rather than explicitly defined; if a client needs inherited
   values, the client SHOULD use the entity domain's inheritance rules
   to deduce those values.

8.  Filtered Property Map

   A filtered property map returns the values of a set of properties for
   a set of entities selected by the client.

   Section 10.5, Section 10.6, Section 10.7 and Section 10.8 give
   examples of filtered property map requests and responses.

8.1.  Media Type

   The media type of a property map resource is "application/alto-
   propmap+json".

8.2.  HTTP Method

   The filtered property map is requested using the HTTP POST method.

8.3.  Accept Input Parameters

   The input parameters for a filtered property map request 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



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   "application/alto-propmapparams+json", which is a JSON object of type
   ReqFilteredPropertyMap:

     object {
       EntityID             entities<1..*>;
       EntityPropertyName   properties<1..*>;
     } ReqFilteredPropertyMap;

   with fields:

   entities:  List of entity identifiers for which the specified
      properties are to be returned.  The ALTO server MUST interpret
      entries appearing multiple times as if they appeared only once.
      The domain of each entity MUST be included in the list of entity
      domains in this resource's "capabilities" field (see Section 8.4).

   properties:  List of properties to be returned for each entity.  Each
      specified property MUST be included in the list of properties in
      this resource's "capabilities" field (see Section 8.4).  The ALTO
      server MUST interpret entries appearing multiple times as if they
      appeared only once.

      Note that the "entities" and "properties" fields MUST have at
      least one entry each.

8.4.  Capabilities

   The capabilities are defined by an object of type
   PropertyMapCapabilities, as defined in Section 7.4.

8.5.  Uses

   Same to the "uses" field of the Property Map resource (see
   Section 7.5).

8.6.  Response

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

   Specifically, a filtered property map request can be invalid as
   follows:

   o  An entity identifier in "entities" in the request is invalid if:

      *  The domain of this entity is not defined in the "entity-
         domains" capability of this resource in the IRD;



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      *  The entity identifier is an invalid identifier in the entity
         domain.

      A valid entity identifier is never an error, even if this filtered
      property map resource does not define any properties for it.

      If an entity identifier in "entities" in the 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 entity identifier.

   o  A property name in "properties" in the request is invalid if this
      property name is not defined in the "properties" capability of
      this resource in the IRD.

      It is not an error that a filtered property map resource does not
      define a requested property's value for a particular entity.  In
      this case, the ALTO server MUST omit that property from the
      response for that endpoint.

      If a property name in "properties" in the request is invalid, the
      ALTO server MUST return an "E_INVALID_FIELD_VALUE" error defined
      in Section 8.5.2 of [RFC7285].  The "value" field of the error
      message SHOULD indicate the property name.

   The response to a valid request is the same as for the Property Map
   (see Section 7.6), except that:

   o  If the requested entities include entities in the shared entity
      domain, the "dependent-vtags" field in its "meta" field MUST
      include version tags of all dependent resources appearing in the
      "uses" field.

   o  If the requested entities only include entities in resource-
      specific entity domains, the "dependent-vtags" field in its "meta"
      field MUST include version tags of resources which requested
      resource-specific entity domains and requested resource-specific
      properties are dependent on.

   o  The response only includes the entities and properties requested
      by the client.  If an entity in the request is identified by a
      hierarchical identifier (e.g., an "ipv4" or "ipv6" address block),
      the response MUST cover properties for all identifiers in this
      hierarchical identifier.

   It is important that the filtered property map response MUST include
   all inherited property values for the requested entities and all the




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   entities which are able to inherit property values from them.  To
   achieve this goal, the ALTO server MAY follow three rules:

   o  If a property for a requested entity is inherited from another
      entity not included in the request, the response SHOULD include
      this property for the requested entity.  For example, A full
      property map may skip a property P for an entity A (e.g.,
      ipv4:192.0.2.0/31) if P can be derived using inheritance from
      another entity B (e.g., ipv4:192.0.2.0/30).  A filtered property
      map request may include only A but not B.  In such a case, the
      property P SHOULD be included in the response for A.

   o  If there are entities covered by a requested entity but having
      different values for the requested properties, the response SHOULD
      include all those entities and the different property values for
      them.  For example, considering a request for property P of entity
      A (e.g., ipv4:192.0.2.0/31), if P has value v1 for
      A1=ipv4:192.0.2.0/32 and v2 for A2=ipv4:192.0.2.1/32, then, the
      response SHOULD include A1 and A2.

   o  If an entity in the response is already covered by some other
      entities in the same response, it SHOULD be removed from the
      response for compactness.  For example, in the previous example,
      the entity A=ipv4:192.0.2.0/31 SHOULD be removed because A1 and A2
      cover all the addresses in A.

   An ALTO client should be aware that the entities in the response MAY
   be different from the entities in its request.

9.  Impact on Legacy ALTO Servers and ALTO Clients

9.1.  Impact on Endpoint Property Service

   Since the property map and the filtered property map defined in this
   document provide the functionality of the Endpoint Property Service
   (EPS) defined in Section 11.4 of [RFC7285], it is RECOMMENDED that
   the EPS be deprecated in favor of Property Map and Filtered Property
   Map.  However, ALTO servers MAY provide an EPS for the benefit of
   legacy clients.

9.2.  Impact on Resource-Specific Properties

   Section 10.8 of [RFC7285] defines two categories of endpoint
   properties: "resource-specific" and "global".  Resource-specific
   property names are prefixed with the ID of the resource they depend
   upon, while global property names have no such prefix.  The property
   map and the filtered property map defined in this document defines
   the similar categories for entity properties.  The difference is that



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   there is no "global" entity properties but the "self-defined" entity
   properties as the special case of the "resource-specific" entity
   properties instead.

9.3.  Impact on Other Properties

   In general, there should be little or no impact on other previously
   defined properties.  The only consideration is that properties can
   now be defined on blocks of entity identifiers, rather than just
   individual entity identifiers, which might change the semantics of a
   property.

10.  Examples

10.1.  Network Map

   The examples in this section use a very simple default network map:

            defaultpid:  ipv4:0.0.0.0/0  ipv6:::0/0
            pid1:        ipv4:192.0.2.0/25
            pid2:        ipv4:192.0.2.0/28  ipv4:192.0.2.16/28
            pid3:        ipv4:192.0.3.0/28
            pid4:        ipv4:192.0.3.16/28

                   Figure 3: Example Default Network Map

   And another simple alternative network map:

            defaultpid:  ipv4:0.0.0.0/0  ipv6:::0/0
            pid1:        ipv4:192.0.2.0/28  ipv4:192.0.2.16/28
            pid2:        ipv4:192.0.3.0/28  ipv4:192.0.3.16/28

                 Figure 4: Example Alternative Network Map

10.2.  Property Definitions

   Beyond "pid", the examples in this section use four additional
   properties for Internet address domains, "ISP", "ASN", "country" and
   "state", with the following values:












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                                   ISP    ASN   country   state
           ipv4:192.0.2.0/23:    BitsRus   -      us       -
           ipv4:192.0.2.0/28:       -    12345    -        NJ
           ipv4:192.0.2.16/28:      -    12345    -        CT
           ipv4:192.0.2.1:          -      -      -        PA
           ipv4:192.0.3.0/28:       -    12346    -        TX
           ipv4:192.0.3.16/28:      -    12346    -        MN

      Figure 5: Example Property Values for Internet Address Domains

   And the examples in this section use the property "region" for the
   PID domain of the default network map with the following values:

                                          region
                       pid:defaultpid:     -
                       pid:pid1:           us-west
                       pid:pid2:           us-east
                       pid:pid3:           us-south
                       pid:pid4:           us-north

      Figure 6: Example Property Values for Default Network Map's PID
                                  Domain

   Note that "-" means the value of the property for the entity is
   "undefined".  So the entity would inherit a value for this property
   by the inheritance rule if possible.  For example, the value of the
   "ISP" property for "ipv4:192.0.2.1" is "BitsRus" because of
   "ipv4:192.0.2.0/24".  But the "region" property for "pid:defaultpid"
   has no value because no entity from which it can inherit.

   Similar to the PID domain of the default network map, the examples in
   this section use the property "ASN" for the PID domain of the
   alternative network map with the following values:

                                             ASN
                          pid:defaultpid:     -
                          pid:pid1:         12345
                          pid:pid2:         12346

    Figure 7: Example Property Values for Alternative Network Map's PID
                                  Domain

10.3.  Information Resource Directory (IRD)

   The following IRD defines the relevant resources of the ALTO server.
   It provides two property maps, one for the "ISP" and "ASN"
   properties, and another for the "country" and "state" properties.
   The server could have provided a single property map for all four



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   properties, but did not, presumably because the organization that
   runs the ALTO server believes any given client is not interested in
   all four properties.

   The server provides two filtered property maps.  The first returns
   all four properties, and the second just returns the "pid" property
   for the default network map.

   The filtered property maps for the "ISP", "ASN", "country" and
   "state" properties do not depend on the default network map (it does
   not have a "uses" capability), because the definitions of those
   properties do not depend on the default network map.  The Filtered
   Property Map for the "pid" property does have a "uses" capability for
   the default network map, because that defines the values of the "pid"
   property.

   Note that for legacy clients, the ALTO server provides an Endpoint
   Property Service for the "pid" property for the default network map.

        "meta" : {
          ...
          "default-alto-network-map" : "default-network-map"
        },
        "resources" : {
          "default-network-map" : {
            "uri" : "http://alto.example.com/networkmap/default",
            "media-type" : "application/alto-networkmap+json"
          },
          "alt-network-map" : {
            "uri" : "http://alto.example.com/networkmap/alt",
            "media-type" : "application/alto-networkmap+json"
          },
          .... property map resources ....
          "ia-property-map" : {
            "uri" : "http://alto.example.com/propmap/full/inet-ia",
            "media-type" : "application/alto-propmap+json",
            "uses": [ "default-network-map", "alt-network-map" ],
            "capabilities" : {
              "mappings": {
                "ipv4": [ ".ISP", ".ASN" ],
                "ipv6": [ ".ISP", ".ASN" ]
              }
            }
          },
          "iacs-property-map" : {
            "uri" : "http://alto.example.com/propmap/full/inet-iacs",
            "media-type" : "application/alto-propmap+json",
            "accepts": "application/alto-propmapparams+json",



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            "uses": [ "default-network-map", "alt-network-map" ],
            "capabilities" : {
              "mappings": {
                "ipv4": [ ".ISP", ".ASN", ".country", ".state" ],
                "ipv6": [ ".ISP", ".ASN", ".country", ".state" ]
              }
            }
          },
          "region-property-map": {
            "uri": "http://alto.exmaple.com/propmap/region",
            "media-type": "application/alto-propmap+json",
            "accepts": "application/alto-propmapparams+json",
            "uses" : [ "default-network-map", "alt-network-map" ],
            "capabilities": {
              "mappings": {
                "default-network-map.pid": [ ".region" ],
                "alt-network-map.pid": [ ".ASN" ],
              }
            }
          },
          "ip-pid-property-map" : {
            "uri" : "http://alto.example.com/propmap/lookup/pid",
            "media-type" : "application/alto-propmap+json",
            "accepts" : "application/alto-propmapparams+json",
            "uses" : [ "default-network-map", "alt-network-map" ],
            "capabilities" : {
              "mappings": {
                "ipv4": [ "default-network-map.pid",
                          "alt-network-map.pid" ],
                "ipv6": [ "default-network-map.pid",
                          "alt-network-map.pid" ]
              }
            }
          },
          "legacy-endpoint-property" : {
             "uri" : "http://alto.example.com/legacy/eps-pid",
             "media-type" : "application/alto-endpointprop+json",
             "accepts" : "application/alto-endpointpropparams+json",
             "capabilities" : {
               "properties" : [ "default-network-map.pid",
                                "alt-network-map.pid" ]
             }
          }
        }

                           Figure 8: Example IRD





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10.4.  Property Map Example

   The following example uses the properties and IRD defined above to
   retrieve a Property Map for entities with the "ISP" and "ASN"
   properties.

   Note that, to be compact, the response does not include the entity
   "ipv4:192.0.2.0", because values of all those properties for this
   entity are inherited from other entities.

   Also note that the entities "ipv4:192.0.2.0/28" and
   "ipv4:192.0.2.16/28" are merged into "ipv4:192.0.2.0/27", because
   they have the same value of the "ASN" property.  The same rule
   applies to the entities "ipv4:192.0.3.0/28" and "ipv4:192.0.3.0/28".
   Both of "ipv4:192.0.2.0/27" and "ipv4:192.0.3.0/27" omit the value
   for the "ISP" property, because it is inherited from
   "ipv4:192.0.2.0/23".

   GET /propmap/full/inet-ia HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-propmap+json,application/alto-error+json

   HTTP/1.1 200 OK
   Content-Length: ###
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {"resource-id": "default-network-map",
          "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"},
         {"resource-id": "alt-network-map",
          "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d"}
       ]
     },
     "property-map": {
       "ipv4:192.0.2.0/23":   {".ISP": "BitsRus"},
       "ipv4:192.0.2.0/27":   {".ASN": "12345"},
       "ipv4:192.0.3.0/27":   {".ASN": "12346"}
     }
   }

10.5.  Filtered Property Map Example #1

   The following example uses the filtered property map resource to
   request the "ISP", "ASN" and "state" properties for several IPv4
   addresses.




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   Note that the value of "state" for "ipv4:192.0.2.0" is the only
   explicitly defined property; the other values are all derived by the
   inheritance rules for Internet address entities.

   POST /propmap/lookup/inet-iacs HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-propmap+json,application/alto-error+json
   Content-Length: ###
   Content-Type: application/alto-propmapparams+json

   {
     "entities" : [ "ipv4:192.0.2.0",
                    "ipv4:192.0.2.1",
                    "ipv4:192.0.2.17" ],
     "properties" : [ ".ISP", ".ASN", ".state" ]
   }

   HTTP/1.1 200 OK
   Content-Length: ###
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {"resource-id": "default-network-map",
          "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"},
         {"resource-id": "alt-network-map",
          "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d"}
       ]
     },
     "property-map": {
       "ipv4:192.0.2.0":
              {".ISP": "BitsRus", ".ASN": "12345", ".state": "PA"},
       "ipv4:192.0.2.1":
              {".ISP": "BitsRus", ".ASN": "12345", ".state": "NJ"},
       "ipv4:192.0.2.17":
              {".ISP": "BitsRus", ".ASN": "12345", ".state": "CT"}
     }
   }

10.6.  Filtered Property Map Example #2

   The following example uses the filtered property map resource to
   request the "ASN", "country" and "state" properties for several IPv4
   prefixes.






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   Note that the property values for both entities "ipv4:192.0.2.0/26"
   and "ipv4:192.0.3.0/26" are not explicitly defined.  They are
   inherited from the entity "ipv4:192.0.2.0/23".

   Also note that some entities like "ipv4:192.0.2.0/28" and
   "ipv4:192.0.2.16/28" in the response are not listed in the request
   explicitly.  The response includes them because they are refinements
   of the requested entities and have different values for the requested
   properties.

   The entity "ipv4:192.0.4.0/26" is not included in the response,
   because there are neither entities which it is inherited from, nor
   entities inherited from it.

   POST /propmap/lookup/inet-iacs HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-propmap+json,application/alto-error+json
   Content-Length: ###
   Content-Type: application/alto-propmapparams+json

   {
     "entities" : [ "ipv4:192.0.2.0/26",
                    "ipv4:192.0.3.0/26",
                    "ipv4:192.0.4.0/26" ],
     "properties" : [ ".ASN", ".country", ".state" ]
   }

























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   HTTP/1.1 200 OK
   Content-Length: ###
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {"resource-id": "default-network-map",
          "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"},
         {"resource-id": "alt-network-map",
          "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d"}
       ]
     },
     "property-map": {
       "ipv4:192.0.2.0/26":  {".country": "us"},
       "ipv4:192.0.2.0/28":  {".ASN": "12345",
                              ".state": "NJ"},
       "ipv4:192.0.2.16/28": {".ASN": "12345",
                              ".state": "CT"},
       "ipv4:192.0.2.0":     {".state": "PA"},
       "ipv4:192.0.3.0/26":  {".country": "us"},
       "ipv4:192.0.3.0/28":  {".ASN": "12345",
                              ".state": "TX"},
       "ipv4:192.0.3.16/28": {".ASN": "12345",
                              ".state": "MN"}
    }
   }

10.7.  Filtered Property Map Example #3

   The following example uses the filtered property map resource to
   request the "pid" property for several IPv4 addresses and prefixes.

   Note that the entity "ipv4:192.0.3.0/27" is redundant in the
   response.  Although it can inherit a value of "defaultpid" for the
   "pid" property from the entity "ipv4:0.0.0.0/0", none of addresses in
   it is in "defaultpid".  Because blocks "ipv4:192.0.3.0/28" and
   "ipv4:192.0.3.16/28" have already covered all addresses in that
   block.  So an ALTO server who wants a compact response can omit this
   entity.











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   POST /propmap/lookup/pid HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-propmap+json,application/alto-error+json
   Content-Length: ###
   Content-Type: application/alto-propmapparams+json

   {
     "entities" : [
                   "ipv4:192.0.2.128",
                   "ipv4:192.0.3.0/27" ],
     "properties" : [ "default-network-map.pid" ]
   }

   HTTP/1.1 200 OK
   Content-Length: ###
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {"resource-id": "default-network-map",
          "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"},
         {"resource-id": "alt-network-map",
          "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d"}
       ]
     },
     "property-map": {
       "ipv4:192.0.2.128":   {"default-network-map.pid": "defaultpid"},
       "ipv4:192.0.2.0/27":  {"default-network-map.pid": "defaultpid"},
       "ipv4:192.0.3.0/28":  {"default-network-map.pid": "pid3"},
       "ipv4:192.0.3.16/28": {"default-network-map.pid": "pid4"}
     }
   }

10.8.  Filtered Property Map Example #4

   The following example uses the filtered property map resource to
   request the "region" property for several PIDs defined in "default-
   network-map".  The value of the "region" property for each PID is not
   defined by "default-network-map", but the reason why the PID is
   defined by the network operator.










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   POST /propmap/lookup/region HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-propmap+json,application/alto-error+json
   Content-Length: ###
   Content-Type: application/alto-propmapparams+json

   {
     "entities" : ["default-network-map.pid:pid1",
                   "default-network-map.pid:pid2"],
     "properties" : [ ".region" ]
   }

   HTTP/1.1 200 OK
   Content-Length: ###
   Content-Type: application/alto-propmap+json

   {
     "meta" : {
       "dependent-vtags" : [
          {"resource-id": "default-network-map",
           "tag": "7915dc0290c2705481c491a2b4ffbec482b3cf62"}
       ]
     },
     "property-map": {
       "default-network-map.pid:pid1": {
         ".region": "us-west"
       },
       "default-network-map.pid:pid2": {
         ".region": "us-east"
       }
     }
   }

11.  Security Considerations

   Both Property Map and Filtered Property Map defined in this document
   fit into the architecture of the ALTO base protocol, and hence the
   Security Considerations (Section 15 of [RFC7285]) of the base
   protocol fully apply: authenticity and integrity of ALTO information
   (i.e., authenticity and integrity of Property Maps), potential
   undesirable guidance from authenticated ALTO information (e.g.,
   potentially imprecise or even wrong value of a property such as geo-
   location), confidentiality of ALTO information (e.g., exposure of a
   potentially sensitive entity property such as geo-location), privacy
   for ALTO users, and availability of ALTO services should all be
   considered.





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   A particular fundamental security consideration when an ALTO server
   provides a Property Map is to define precisely the policies on who
   can access what properties for which entities.  Security mechanisms
   such as authentication and confidentiality mechanisms then should be
   applied to enforce the policy.  For example, a policy can be that a
   property P can be accessed only by its owner (e.g., the customer who
   is allocated a given IP address).  Then, the ALTO server will need to
   deploy corresponding mechanisms to realize the policy.  The policy
   may allow non-owners to access a coarse-grained value of the property
   P.  In such a case, the ALTO server may provide a different URI to
   provide the information.

12.  IANA Considerations

   This document defines additional application/alto-* media types, and
   extends the ALTO endpoint property registry.

12.1.  application/alto-* Media Types

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

    +--------------+--------------------------+-----------------------+
    | Type         | Subtype                  | Specification         |
    +--------------+--------------------------+-----------------------+
    | application  | alto-propmap+json        | Section 7.1           |
    | application  | alto-propmapparams+json  | Section 8.3           |
    +--------------+--------------------------+-----------------------+

                   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

   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].




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   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).

12.2.  ALTO Entity Domain Type Registry

   This document requests IANA to create and maintain the "ALTO Entity
   Domain Type Registry", listed in Table 2.

   +-------------+---------------------------+-------------------------+
   | Identifier  | Entity Identifier         | Hierarchy & Inheritance |
   |             | Encoding                  |                         |
   +-------------+---------------------------+-------------------------+
   | ipv4        | See Section 5.1.1         | See Section 5.1.3       |
   | ipv6        | See Section 5.1.2         | See Section 5.1.3       |
   | pid         | See Section 5.2           | None                    |
   +-------------+---------------------------+-------------------------+

                       Table 2: ALTO Entity Domains.





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   This registry serves two purposes.  First, it ensures uniqueness of
   identifiers referring to ALTO entity domains.  Second, it states the
   requirements for allocated entity domains.

12.2.1.  Consistency Procedure between ALTO Address Type Registry and
         ALTO Entity Domain Type Registry

   One potential issue of introducing the "ALTO Entity Domain Type
   Registry" is its relationship with the "ALTO Address Types Registry"
   already defined in Section 14.4 of [RFC7285].  In particular, the
   entity identifier of a type of an entity domain registered in the
   "ALTO Entity Domain Type Registry" MAY match an address type defined
   in "ALTO Address Type Registry".  It is necessary to precisely define
   and guarantee the consistency between "ALTO Address Type Registry"
   and "ALTO Entity Domain Registry".

   We define that the ALTO Entity Domain Type Registry is consistent
   with ALTO Address Type Registry if two conditions are satisfied:

   o  When an address type is already or able to be registered in the
      ALTO Address Type Registry [RFC7285], the same identifier MUST be
      used when a corresponding entity domain type is registered in the
      ALTO Entity Domain Type Registry.

   o  If an ALTO entity domain type has the same identifier as an ALTO
      address type, their addresses encoding MUST be compatible.

   To achieve this consistency, the following items MUST be checked
   before registering a new ALTO entity domain type in a future
   document:

   o  Whether the ALTO Address Type Registry contains an address type
      that can be used as an entity identifier for the candidate domain
      identifier.  This has been done for the identifiers "ipv4" and
      "ipv6" in Table 2.

   o  Whether the candidate entity identifier of the type of the entity
      domain is able to be an endpoint address, as defined in Sections
      2.1 and 2.2 of [RFC7285].

   When a new ALTO entity domain type is registered, the consistency
   with the ALTO Address Type Registry MUST be ensured by the following
   procedure:

   o  Test: Do corresponding entity identifiers match a known "network"
      address type?

      *  If yes (e.g., cell, MAC or socket addresses):



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         +  Test: Is such an address type present in the ALTO Address
            Type Registry?

            -  If yes: Set the new ALTO entity domain type identifier to
               be the found ALTO address type identifier.

            -  If no: Define a new ALTO entity domain type identifier
               and use it to register a new address type in the ALTO
               Address Type Registry following Section 14.4 of
               [RFC7285].

         +  Use the new ALTO entity domain type identifier to register a
            new ALTO entity domain type in the ALTO Entity Domain Type
            Registry following Section 12.2.2 of this document.

      *  If no (e.g., pid name, ane name or country code): Proceed with
         the ALTO Entity Domain Type registration as described in
         Section 12.2.2.

12.2.2.  ALTO Entity Domain Type Registration Process

   New ALTO entity domain types are assigned after IETF Review [RFC5226]
   to ensure that proper documentation regarding the new ALTO entity
   domain types and their security considerations has been provided.
   RFCs defining new entity domain types SHOULD indicate how an entity
   in a registered type of domain is encoded as an EntityID, and, if
   applicable, the rules defining the entity hierarchy and property
   inheritance.  Updates and deletions of ALTO entity domains follow the
   same procedure.

   Registered ALTO entity domain type identifiers MUST conform to the
   syntactical requirements specified in Section 4.1.2.  Identifiers are
   to be recorded and displayed as strings.

   Requests to the IANA to add a new value to the registry MUST include
   the following information:

   o  Identifier: The name of the desired ALTO entity domain type.

   o  Entity Identifier Encoding: The procedure for encoding the
      identifier of an entity of the registered type as an EntityID (see
      Section 4.1.3).  If corresponding entity identifiers of an entity
      domain match a known "network" address type, the Entity Identifier
      Encoding of this domain identifier MUST include both Address
      Encoding and Prefix Encoding of the same identifier registered in
      the ALTO Address Type Registry [RFC7285].  For the purpose of
      defining properties, an individual entity identifier and the




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      corresponding full-length prefix MUST be considered aliases for
      the same entity.

   o  Hierarchy: If the entities form a hierarchy, the procedure for
      determining that hierarchy.

   o  Inheritance: If entities can inherit property values from other
      entities, the procedure for determining that inheritance.

   o  Mapping to ALTO Address Type: A boolean value to indicate if the
      entity domain type can be mapped to the ALTO address type with the
      same identifier.

   o  Security Considerations: In some usage scenarios, entity
      identifiers carried in ALTO Protocol messages may reveal
      information about an ALTO client or an ALTO service provider.
      Applications and ALTO service providers using addresses of the
      registered type should be made aware of how (or if) the addressing
      scheme relates to private information and network proximity.

   This specification requests registration of the identifiers "ipv4",
   "ipv6" and "pid", as shown in Table 2.

12.3.  ALTO Entity Property Type Registry

   This document requests IANA to create and maintain the "ALTO Entity
   Property Type Registry", listed in Table 3.

   To distinguish with the "ALTO Endpoint Property Type Registry", each
   entry in this registry is an ALTO entity property type defined in
   Section 4.2.1.  Thus, registered ALTO entity property type identifier
   MUST conform to the syntactical requirements specified in that
   section.

   The initial registered ALTO entity property types are listed in
   Table 3.

             +-------------+---------------------------------+
             | Identifier  | Intended Semantics              |
             +-------------+---------------------------------+
             | pid         | See Section 7.1.1 of [RFC7285]  |
             +-------------+---------------------------------+

                   Table 3: ALTO Entity Property Types.

   Requests to the IANA to add a new value to the registry MUST include
   the following information:




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   o  Identifier: The unique id for the desired ALTO entity property
      type.  The format MUST be as defined in Section 4.2.1 of this
      document.  It includes the information of the applied ALTO entity
      domain and the property name.

   o  Intended Semantics: ALTO entity properties carry with them
      semantics to guide their usage by ALTO clients.  Hence, a document
      defining a new type SHOULD provide guidance to both ALTO service
      providers and applications utilizing ALTO clients as to how values
      of the registered ALTO entity property should be interpreted.

   This document requests registration of the identifier "pid", as shown
   in Table 3.

12.4.  ALTO Resource-Specific Entity Domain Registries

12.4.1.  Network Map

   Media-type: application/alto-networkmap+json

               +---------------------+---------------------+
               | Entity Domain Type  | Intended Semantics  |
               +---------------------+---------------------+
               | ipv4                | See Section 6.2.1   |
               | ipv6                | See Section 6.2.1   |
               | pid                 | See Section 6.2.1   |
               +---------------------+---------------------+

        Table 4: ALTO Network Map Resource-Specific Entity Domain.

12.4.2.  Endpoint Property

   Media-type: application/alto-endpointprop+json

               +---------------------+---------------------+
               | Entity Domain Type  | Intended Semantics  |
               +---------------------+---------------------+
               | ipv4                | See Section 6.3.1   |
               | ipv6                | See Section 6.3.1   |
               +---------------------+---------------------+

     Table 5: ALTO Endpoint Property Resource-Specific Entity Domain.

12.5.  ALTO Resource Entity Property Mapping Registries







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12.5.1.  Network Map

   Media-type: application/alto-networkmap+json

   +-----------------+-----------------+-------------+-----------------+
   | Mapping         | Entity Domain   | Property    | Intended        |
   | Descriptor      | Type            | Type        | Semantics       |
   +-----------------+-----------------+-------------+-----------------+
   | ipv4 -> pid     | ipv4            | pid         | See Section     |
   |                 |                 |             | 6.2.2           |
   | ipv6 -> pid     | ipv6            | pid         | See Section     |
   |                 |                 |             | 6.2.2           |
   +-----------------+-----------------+-------------+-----------------+

            Table 6: ALTO Network Map Entity Property Mapping.

13.  Acknowledgments

   The authors would like to thank discussions with Kai Gao, Qiao Xiang,
   Shawn Lin, Xin Wang, Danny Perez, and Vijay Gurbani.  The authors
   thank Dawn Chen (Tongji University), and Shenshen Chen (Tongji/Yale
   University) for their contributions to earlier drafts.

14.  Normative References

   [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>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
              (CIDR): The Internet Address Assignment and Aggregation
              Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
              2006, <https://www.rfc-editor.org/info/rfc4632>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.







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   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952,
              DOI 10.17487/RFC5952, August 2010,
              <https://www.rfc-editor.org/info/rfc5952>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

   [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>.

   [RFC7921]  Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
              Nadeau, "An Architecture for the Interface to the Routing
              System", RFC 7921, DOI 10.17487/RFC7921, June 2016,
              <https://www.rfc-editor.org/info/rfc7921>.

Appendix A.  Scope of Property Map

   Using entity domains to organize entities, an ALTO property map
   resource can be regarded as given sets of properties for given entity
   domains.  If we ignore the resource-agnostic entity domains, we can
   regard an ALTO property map resource as a set of (ri, di) => (ro, po)
   mappings, where (ri, di) means a resource-specific entity domain of
   type di defined by the information resource ri, and (ro, po) means a
   resource-specific entity property po defined by the information
   resource ro.

   For each (ri, di) => (ro, po) mapping, the scope of an ALTO property
   map resource must be one of the cases in the following diagram:












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                       domain.resource   domain.resource
                       (ri) = r          (ri) = this
                     +-----------------|-----------------+
       prop.resource | Export          | Non-exist       |
       (ro) = r      |                 |                 |
                     +-----------------|-----------------+
       prop.resource | Extend          | Define          |
       (ro) = this   |                 |                 |
                     +-----------------|-----------------+

   where "this" represents the resulting property map resource, and "r"
   represents an existing ALTO information resource other the resulting
   property map resource.

   o  ri = ro = r ("export" mode): the property map resource just
      transforms the property mapping di => po defined by r into the
      unified representation format and exports it.  For example: r =
      "netmap1", di = "ipv4", po = "pid".  The property map resource
      exports the "ipv4 => pid" mapping defined by "netmap1".

   o  ri = r, ro = this ("extend" mode): the property map extends
      properties of entities in the entity domain (r, di) and defines a
      new property po on them.  For example: the property map resource
      ("this") defines a "geolocation" property on domain "netmap1.pid".

   o  ri = ro = this ("define" mode): the property map defines a new
      intrinsic entity domain and defines property po for each entity in
      this domain.  For example: the property map resource ("this")
      defines a new entity domain "asn" and defines a property
      "ipprefixes" on this domain.

   o  ri = this, ro = r: in the scope of a property map resource, it
      does not make sense that another existing ALTO information
      resource defines a property for this property map resource.

A.1.  Example Property Map

   The following figure shows an example property map called Property
   Map 1, which depends on two network maps and provides three sets of
   mappings by

   o  exporting a mapping from ipv4 entities to PIDs defined by two
      different network maps,

   o  extending geo-location properties to ipv4 entities defined by
      Network Map 1,

   o  and defining a new mapping from ASNs to traffic load properties.



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                                                          (Define)
      +----------+                                       +-------------+
    ->| Property |<-----------------------------|--------| asn  | load |
   /  |   Map 1  |                              |        |-------------|
  /   +----------+                              |        | 1234 | 95%  |
 |         ^                                    |        | 5678 | 70%  |
 |         |                                     \       +-------------+
 |         |          (Export)                    \       (Extend)
 |    +---------+    +------------------------+    \     +--------------+
 |    | Network |----| ipv4           | pid   |     -----| geo-location |
 |    |  Map 1  |    |------------------------|          +--------------+
 |    +---------+    | 192.168.0.0/24 | pid1  | - - - -> | New York     |
 |                   | 192.168.1.0/24 | pid2  | - - - -> | Shanghai     |
 |                   +------------------------+          +--------------+
 |                    (Export)
  \   +---------+    +------------------------+
   ---| Network |----| ipv4           | pid   |
      |  Map 2  |    |------------------------|
      +---------+    | 192.168.0.0/24 | Paris |
                     | ...            | ...   |
                     +------------------------+

   More detailed examples are shown in Section 10.

Authors' Addresses

   Wendy Roome
   Nokia Bell Labs (Retired)
   124 Burlington Rd
   Murray Hill, NJ  07974
   USA

   Phone: +1-908-464-6975
   Email: wendy@wdroome.com


   Sabine Randriamasy
   Nokia Bell Labs
   Route de Villejust
   NOZAY  91460
   FRANCE

   Email: Sabine.Randriamasy@nokia-bell-labs.com








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   Y. Richard Yang
   Yale University
   51 Prospect Street
   New Haven, CT  06511
   USA

   Phone: +1-203-432-6400
   Email: yry@cs.yale.edu


   Jingxuan Jensen Zhang
   Tongji University
   4800 Caoan Road
   Shanghai  201804
   China

   Email: jingxuan.n.zhang@gmail.com


   Kai Gao
   Sichuan University
   Chengdu  610000
   China

   Email: kaigao@scu.edu.cn


























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