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

ALTO WG                                                         W. Roome
Internet-Draft                                            S. Randriamasy
Intended status: Standards Track                         Nokia Bell Labs
Expires: September 12, 2019                                      Y. Yang
                                                         Yale University
                                                                J. Zhang
                                                       Tongji University
                                                          March 11, 2019


                Unified Properties for the ALTO Protocol
                  draft-ietf-alto-unified-props-new-07

Abstract

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

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 September 12, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definitions and Concepts  . . . . . . . . . . . . . . . . . .   4
     2.1.  Entity  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Entity Domain . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  Domain Name . . . . . . . . . . . . . . . . . . . . . . .   5
     2.4.  Entity Identifier . . . . . . . . . . . . . . . . . . . .   6
     2.5.  Property Type and Property Name . . . . . . . . . . . . .   6
     2.6.  Hierarchy and Inheritance . . . . . . . . . . . . . . . .   7
     2.7.  Relationship with Other ALTO Resources  . . . . . . . . .   7
   3.  Entity Domains  . . . . . . . . . . . . . . . . . . . . . . .   8
     3.1.  Internet Address Domains  . . . . . . . . . . . . . . . .   9
       3.1.1.  IPv4 Domain . . . . . . . . . . . . . . . . . . . . .   9
       3.1.2.  IPv6 Domain . . . . . . . . . . . . . . . . . . . . .   9
       3.1.3.  Hierarchy and Inheritance of ipv4/ipv6 Domains  . . .   9
     3.2.  PID Domain  . . . . . . . . . . . . . . . . . . . . . . .  11
       3.2.1.  Domain Name . . . . . . . . . . . . . . . . . . . . .  11
       3.2.2.  Domain-Specific Entity Identifiers  . . . . . . . . .  11
       3.2.3.  Hierarchy and Inheritance . . . . . . . . . . . . . .  11
       3.2.4.  Relationship To Internet Addresses Domains  . . . . .  11
     3.3.  Internet Address Properties vs. PID Properties  . . . . .  11
   4.  Property Map  . . . . . . . . . . . . . . . . . . . . . . . .  12
     4.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  12
     4.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  12
     4.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  12
     4.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  12
     4.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     4.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  13
   5.  Filtered Property Map . . . . . . . . . . . . . . . . . . . .  14
     5.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  14
     5.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  14
     5.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  14
     5.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  15
     5.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  15
     5.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  15
   6.  Impact on Legacy ALTO Servers and ALTO Clients  . . . . . . .  17
     6.1.  Impact on Endpoint Property Service . . . . . . . . . . .  17



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     6.2.  Impact on Resource-Specific Properties  . . . . . . . . .  17
     6.3.  Impact on the pid Property  . . . . . . . . . . . . . . .  17
     6.4.  Impact on Other Properties  . . . . . . . . . . . . . . .  18
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  18
     7.1.  Network Map . . . . . . . . . . . . . . . . . . . . . . .  18
     7.2.  Property Definitions  . . . . . . . . . . . . . . . . . .  18
     7.3.  Information Resource Directory (IRD)  . . . . . . . . . .  19
     7.4.  Property Map Example  . . . . . . . . . . . . . . . . . .  21
     7.5.  Filtered Property Map Example #1  . . . . . . . . . . . .  22
     7.6.  Filtered Property Map Example #2  . . . . . . . . . . . .  23
     7.7.  Filtered Property Map Example #3  . . . . . . . . . . . .  24
     7.8.  Filtered Property Map Example #4  . . . . . . . . . . . .  25
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  26
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  27
     9.1.  application/alto-* Media Types  . . . . . . . . . . . . .  27
     9.2.  ALTO Entity Domain Registry . . . . . . . . . . . . . . .  28
       9.2.1.  Consistency Procedure between ALTO Address Type
               Registry and ALTO Entity Domain Registry  . . . . . .  29
       9.2.2.  ALTO Entity Domain Registration Process . . . . . . .  30
     9.3.  ALTO Entity Property Type Registry  . . . . . . . . . . .  31
     9.4.  Acknowledgments . . . . . . . . . . . . . . . . . . . . .  32
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

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 two
   limitations.

   First, it only allows properties to be associated with a particular
   domain of entities, namely individual IP addresses.  It is reasonable
   to think that collections of endpoints, as defined by CIDRs [RFC4632]
   or PIDs, may also have properties.  Since the EPS cannot be extended
   to new entity domains, new services, with new request and response
   messages, would have to be defined for new entity domains.

   Second, 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 an equivalent service for endpoint
   properties.  At first a map of endpoint properties might seem
   impractical, because it could require enumerating the property value
   for every possible endpoint.  But in practice, it is highly unlikely



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   that properties will be defined for every endpoint address.  It is
   much more likely that properties will only be defined for a subset of
   endpoint addresses, and that subset would be small enough to be
   enumerated.  This is particularly true if blocks of endpoint
   addresses with a common prefix (e.g., a CIDR) have the same value for
   a property.  Furthermore, entities in other domains may very well be
   enumerable.

   This document proposes a new approach to retrieve ALTO properties.
   Specifically, it defines two new types of resources, namely Property
   Map (see Section 4) and Filtered Property Map (see Section 5).  The
   former is a GET-mode resource which returns the property values for
   all entities in a domain, 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.

   Additionally, this document introduces ALTO Entity Domains, where an
   entity is a generalization of an endpoint to also represent, a PID, a
   network element, or a cell in a cellular network, etc.  As a
   consequence, ALTO Entity Domains defined in this document are a
   super-set of ALTO Address Types defined in [RFC7285].  Their exact
   relationship is specified in Section 9.2.1.

   Entity domains and property names are extensible.  New entity domains
   can be defined without revising the messages defined in this
   document, in the same way that new cost metrics and new endpoint
   properties can be defined without revising the messages defined in
   [RFC7285].

   This proposal subsumes the Endpoint Property Service defined in
   [RFC7285], although that service may be retained for legacy clients
   (see Section 6).

2.  Definitions and Concepts

2.1.  Entity

   The entity generalizes the concept of the 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:





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   o  a PID, defined in [RFC7285], that has a provider defined human
      readable abstract identifier and maps to a set of ipv4 and ipv6
      addresses,

   o  an ASN number, that has a specified identifier and direct mapping
      to network addresses,

   o  a country code, that specified in ISO 3166 format and that can be
      retrieved from an IP of cellular address.  As a consequence, all
      endpoints are entities while not all entities are endpoints,

   o  a TCP/IP network flow, that has a server defined identifier and
      represents in a TCP/IP 5-Tuple,

   o  a routing element, that 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

   Each entity MUST be in one and only one entity domain.  An entity
   domain is a class of entities.  Examples of entity domains are the
   Internet address domains (see Section 3.1 and the PID domain (see
   Section 3.2).  The future documents can define new entity domains to
   satisfy the additional requirements such as cellular network
   information and routing capability exposure.  But they are not in the
   scope of this document.

2.3.  Domain Name

   Each entity domain has a unique name.  A domain name MUST be no more
   than 32 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 names "ipv4" and "ipv6" identify entities in the
   Internet address domains (see Section 3.1).

   The type DomainName is used in this document to denote a JSON string
   with a domain name in this format.

   Domain names MUST be registered with the IANA, and the format of the
   entity addresses (see Section 2.4) in that entity domain, as well as
   any hierarchical or inheritance rules (see Section 2.6) for those
   entities, MUST be specified at the same time.





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2.4.  Entity Identifier

   Each entity has an identifier of the format:

       EntityId ::= DomainName : DomainSpecificEntityId

   An entity identifier uniquely identifies a particular entity within
   an ALTO property map resource (see Section 4).

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

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

   The format of the second part of an entity identifier depends on the
   entity domain, and MUST be specified when registering a new entity
   domain.  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 is
   registered.

   Note that an entity address MAY have different textual
   representations, for a given entity domain.  For example, the strings
   "ipv6:2001:db8::1" and "ipv6:2001:db8:0:0:0:0:0:1" refer to the same
   entity.

2.5.  Property Type and Property Name

   Every entity in some domain MAY have one or more properties.  Every
   property is identified by a Property Type and is specific to a
   domain.  Every property MUST have a unique Property Type.

   This document defines property types in the domain-specific
   semantics.  Multiple property types with similar semantics MAY share
   the same Property Name in different entity domains.  But each
   property type MUST be registered for a single specific entity domain
   for the following reasons:

   o  Some properties may only be applicable for particular entity
      domains, not all.  For example, the "pid" property is not
      applicable for entities in the "pid" domain.

   o  The interpretation of the value of a property may depend on the
      entity domain.  For different entity domains, not only the
      intended semantics but also the dependent resource types may be
      totally different.  For example, suppose that the "geo-location"



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      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 domain, the property defines the host's
      location and has no required dependency.  However, when applied to
      an entity in the "pid" domain, the property would indicate the
      location of the center of all hosts in this "pid" entity and
      depend on the Network Map defining this "pid" entity.

   Therefore, each property type has a unique identifier encoded with
   the following format:

   PropertyType ::= DomainName : PropertyName

   o  The "DomainName" indicates which entity domain the property type
      applies to.

   o  The "PropertyName" SHOULD relate to the semantics of this property
      type.  It does not have to be globally unique.  In other words,
      different property types could have the same property name applied
      to different entity domains, if they have the similar semantics.
      For example, the property types "ipv4:pid" and "ipv6:pid" have the
      same property name "pid" applied to both "ipv4" and "ipv6"
      domains.

   Property types MUST be registered with the IANA, and the intended
   semantics, as well as the media types of dependent resources and the
   interpretation, MUST be specified at the same time.

2.6.  Hierarchy and Inheritance

   Entities in a given domain MAY form a hierarchy based on entity
   identifiers, and introducing hierarchy allows the introduction of
   inheritance.  Each entity domain MUST define its own hierarchy and
   inheritance rules when registered.  The hierarchy and inheritance
   rule makes it possible for an entity to inherit a property value from
   another entity in the same domain.

2.7.  Relationship with Other ALTO Resources

   [RFC7285] recognizes that some properties for some entity domains MAY
   be specific to an ALTO resource, such as a network map.  Accordingly
   Section 10.8.1 of [RFC7285] defines the concept of "resource-specific
   endpoint properties", and indicates that dependency by prefixing the
   property name with the ID of the resource on which it depends.  That
   document defines one resource-specific property, namely the "pid"
   property, whose value is the name of the PID containing that endpoint
   in the associated network map.



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   Because a property may be associated to more than one information
   resources within an entity domain, this document takes a different
   approach as follows:

   o  Firstly, instead of defining the dependency by prefixing the
      property name with a specific dependent resource identifier, this
      document introduces a Property Type that appends a property name
      to an entity domain name, and registers the dependency types for
      this Property Type.  This gives a hint on the types of dependent
      resources.  For example, the fictitious property "pid:region"
      applying to entities in the PID domain depends on the network map
      in which the input PID entities have been defined; but the
      fictitious property "ipv4:region" does not depend on any
      information resource.

   o  Secondly, it sets a rule saying that in a property map, all
      provided property types MUST have the same dependency types.  For
      example, "pid:region" and "ipv4:region" cannot be provided by an
      individual property map.

   o  Finally, it identifies, in the IRD and Server responses, the
      sequence of information resources associated to all provided
      properties in a particular property map.  If a property depends on
      some different information resources from other properties, the
      ALTO server should define a different property map to provide it.
      For example, the property "ipv4:pid" provided by a particular
      property map MUST depend on one and only one network map.  If an
      ALTO server wants to provide "ipv4:pid" for PIDs defined in both
      network maps "net1" and "net2", it MUST define two individual
      property maps.

   To specify the aforementionned dependencies, this document uses the
   "uses" and "dependent-vtags" fields defined respectively in Sections
   9.1.5 and 11.1 of [RFC7285].

   o  the "uses" field is included in the IRD entry of a resources-
      dependent information resource and specifies the dependent IRD
      resource.

   o  the "dependent-vtags" member is used in a Server response message
      to specify the dependent resource.

3.  Entity Domains

   This document defines three entity domains.  The definition of each
   entity domain below includes the following: (1) domain name, (2)
   domain-specific entity identifiers, and (3) hierarchy and inheritance
   semantics.



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3.1.  Internet Address Domains

   The document defines two entity domains (IPv4 and IPv6) for Internet
   addresses.  Both entity domains include individual addresses and
   blocks of addresses.  Since the two domains use the same hierarchy
   and inheritance semantics, we define the semantics together, instead
   of repeating for each.

3.1.1.  IPv4 Domain

3.1.1.1.  Domain Name

   ipv4

3.1.1.2.  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].  For the
   purpose of defining 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.

3.1.2.  IPv6 Domain

3.1.2.1.  Domain Name

   ipv6

3.1.2.2.  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].  For the purpose of defining 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.

3.1.3.  Hierarchy and Inheritance of ipv4/ipv6 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



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   that this longest prefix rule will ensure no multiple inheritance,
   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.

   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



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      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.

3.2.  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.

3.2.1.  Domain Name

   pid

3.2.2.  Domain-Specific Entity Identifiers

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

3.2.3.  Hierarchy and Inheritance

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

3.2.4.  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".

3.3.  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.




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   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
   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.

4.  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 7.4 gives an example of a property map request and its
   response.

4.1.  Media Type

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

4.2.  HTTP Method

   The property map is requested using the HTTP GET method.

4.3.  Accept Input Parameters

   None.

4.4.  Capabilities

   The capabilities are defined by an object of type
   PropertyMapCapabilities:

       object {
         DomainName entity-domains<1..*>;
         PropertyName properties<1..*>;
       } PropertyMapCapabilities;

   where "entity-domains" is an array specifying the entity domains, and
   "properties" is an array specifying the property names returned for
   entities in those domains.  The semantics is that this property map
   provides all property types generated by the cross product of
   "entity-domains" and "properties".  If a property in "properties" is




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   NOT supported by a domain in "entity-domains", the server can declare
   different property maps to conform to the semantics.

   For example, the capability {"entity-domains": ["ipv4", "ipv6"],
   "properties": ["pid"]} means the property map provides both property
   types "ipv4:pid" and "ipv6:pid".

4.5.  Uses

   The "uses" field of a property map resource in an IRD entry specifies
   dependencies as discussed in Section 2.7.  It is an array of the
   resource ID(s) of the resource(s) that properties of entities in
   domains specified in "entity-domains" depend on.

   In a single property map, every property value of every entity
   depends on the same array of resources.  Thus, if properties
   depending on different resources arrays would be provided, they MUST
   be split into different property maps.

   Note that according to [RFC7285], a legacy ALTO server with two
   network maps, with resource IDs "net1" and "net2", could offer a
   single Endpoint Property Service for the two properties "net1.pid"
   and "net2.pid".  An ALTO server which supports the property map
   resource defined in this document, would, instead, offer two
   different property maps for the "pid" property, one depending on
   "net1", and the other on "net2".

4.6.  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 {
         PropertyName -> JSONValue;
       } EntityProps;



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   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
   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, the ALTO server returns the
   value defined for each of the properties specified in this resource's
   "capabilities" list.  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.

5.  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 7.5, Section 7.6, Section 7.7 and Section 7.8 give examples
   of filtered property map requests and responses.

5.1.  Media Type

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

5.2.  HTTP Method

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

5.3.  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
   "application/alto-propmapparams+json", which is a JSON object of type
   ReqFilteredPropertyMap:

     object {
       EntityId     entities<1..*>;
       PropertyName   properties<1..*>;
     } ReqFilteredPropertyMap;



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   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 5.4).

   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 5.4).  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.

5.4.  Capabilities

   The capabilities are defined by an object of type
   PropertyMapCapabilities, as defined in Section 4.4.

5.5.  Uses

   The "uses" field of a filtered property map is an array with the
   resource ID(s) of resource(s) that each domain in "entity-domains"
   depends on, in order to provide the properties specified in the
   "properties" capability.  The same "uses" rule as defined by the
   property map resource applies (see Section 4.5).

5.6.  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 identifiers in "entities" in the request is invalid if:

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

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





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      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 "property-types" 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 4.6), except that:

   o  The "dependent-vtags" field in its "meta" field only includes the
      version tags of resources on which the requested properties of the
      entity domains depend, and the order MUST be consistent with the
      "uses" field of this filtered property map resource.

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

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



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   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.

6.  Impact on Legacy ALTO Servers and ALTO Clients

6.1.  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.

6.2.  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 do not
   distinguish between those two types of properties.  Instead, if there
   is a dependency, it is indicated by the "uses" capability of a
   property map, and is shared by all properties and entity domains in
   that map.  Accordingly, it is RECOMMENDED that resource-specific
   endpoint properties be deprecated, and no new resource-specific
   endpoint properties be defined.

6.3.  Impact on the pid Property

   Section 7.1.1 of [RFC7285] defines the resource-specific endpoint
   property name "pid", whose value is the name of the PID containing
   that endpoint.  For compatibility with legacy clients, an ALTO server




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   which provides the "pid" property via the EPS MUST use that
   definition, and that syntax.

   However, when used with property maps, this document amends the
   definition of the "pid" property as follows.

   First, the name of the property is simply "pid"; the name is not
   prefixed with the resource ID of a network map.  The "uses"
   capability of the property map indicates the associated network map.
   This implies that a property map can only return the "pid" property
   for one network map; if an ALTO server provides several network maps,
   it MUST provide a Property Map for each of the network maps.

   Second, a client MAY request the "pid" property for a block of
   Internet addresses.  An ALTO server determines the value of "pid" for
   an address block C as the rules defined in Section 5.6.

   Note that although an ALTO server MAY provide a GET-mode property map
   which returns the entire map for the "pid" property, there is no need
   to do so, because that map is simply the inverse of the network map.

6.4.  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 identifiers, rather than just individual
   identifiers, which might change the semantics of a property.

7.  Examples

7.1.  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 Network Map

7.2.  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
           ipv4:192.0.2.0:          -      -      -        PA
           ipv4:192.0.3.0/28:       -    12346    -        TX
           ipv4:192.0.3.16/28:      -    12346    -        MN

      Figure 4: Example Property Values for Internet Address Domains

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

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

             Figure 5: Example Property Values for 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 "ipv4:192.0.2.0" 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.

7.3.  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
   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



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   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",
            "media-type" : "application/alto-networkmap+json"
         },
         .... property map resources ....
         "country-state-property-map" : {
            "uri" : "http://alto.example.com/propmap/full/inet-cs",
            "media-type" : "application/alto-propmap+json",
            "capabilities" : {
              "entity-domains": [ "ipv4", "ipv6" ],
              "properties" : [  "country", "state" ]
            }
         },
         "isp-asn-property-map" : {
            "uri" : "http://alto.example.com/propmap/full/inet-ia",
            "media-type" : "application/alto-propmap+json",
            "capabilities" : {
              "entity-domains": [ "ipv4", "ipv6" ],
              "properties" : [ "ISP", "ASN" ]
            }
         },
         "iacs-property-map" : {
            "uri" : "http://alto.example.com/propmap/lookup/inet-iacs",
            "media-type" : "application/alto-propmap+json",
            "accepts" : "application/alto-propmapparams+json",
            "capabilities" : {
              "entity-domains": [ "ipv4", "ipv6" ],
              "properties" : [ "ISP", "ASN", "country", "state" ]
            }
         },
         "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" ]
            "capabilities" : {
              "entity-domains" : [ "ipv4", "ipv6" ],



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              "properties" : [ "pid" ]
            }
         },
         "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" ],
           "capabilities": {
             "domain-types": [ "pid" ],
             "properties": [ "region" ]
           }
         },
         "legacy-pid-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" ]
            }
         }
      }

                           Figure 6: Example IRD

7.4.  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 includes 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





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

   {
     "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"}
     }
   }

7.5.  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.

   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" ]
   }

















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

   {
     "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"}
     }
   }

7.6.  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.

   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

   {
     "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"}
    }
   }

7.7.  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 cover all addresses in that block.
   So an ALTO server who wants a compact response can omit this entity.

   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" : [ "pid" ]
   }







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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": "7915dc0290c2705481c491a2b4ffbec482b3cf62"}
       ]
     },
     "property-map": {
       "ipv4:192.0.2.128":   {"pid": "defaultpid"},
       "ipv4:192.0.2.0/27":  {"pid": "defaultpid"},
       "ipv4:192.0.3.0/28":  {"pid": "pid3"},
       "ipv4:192.0.3.16/28": {"pid": "pid4"}
     }
   }

7.8.  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.

   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" : ["pid:pid1",
                   "pid:pid2"],
     "properties" : [ "region" ]
   }













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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": "7915dc0290c2705481c491a2b4ffbec482b3cf62"}
       ]
     },
     "property-map": {
       "pid:pid1": {
         "region": "west"
       },
       "pid:pid2": {
         "region": "east"
       }
     }
   }

8.  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.

   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.





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9.  IANA Considerations

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

9.1.  application/alto-* Media Types

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

    +--------------+--------------------------+-----------------------+
    | Type         | Subtype                  | Specification         |
    +--------------+--------------------------+-----------------------+
    | application  | alto-propmap+json        | Section 4.1           |
    | application  | alto-propmapparams+json  | Section 5.3           |
    +--------------+--------------------------+-----------------------+

                   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].

   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:




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      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).

9.2.  ALTO Entity Domain Registry

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

   +------------+----------------+------------------+------------------+
   | Identifier | Entity         | Hierarchy &      | Mapping to ALTO  |
   |            | Identifier     | Inheritance      | Address Type     |
   |            | Encoding       |                  |                  |
   +------------+----------------+------------------+------------------+
   | ipv4       | See            | See              | Yes              |
   |            | Section 3.1.1  | Section 3.1.3    |                  |
   | ipv6       | See            | See              | Yes              |
   |            | Section 3.1.2  | Section 3.1.3    |                  |
   | pid        | See            | None             | No               |
   |            | Section 3.2    |                  |                  |
   +------------+----------------+------------------+------------------+

                       Table 2: ALTO Entity Domains.

   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.









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

   One potential issue of introducing the "ALTO Entity Domain Registry"
   is its relationship with the "ALTO Address Types Registry" already
   defined in Section 14.4 of [RFC7285].  In particular, the entity
   identifier of an entity domain registered in the "ALTO Entity Domain
   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 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 is registered in the ALTO
      Entity Domain Registry.

   o  If an ALTO entity domain 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 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 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 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):

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





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

            -  If no: Define a new ALTO entity domain 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 identifier to register a new
            ALTO entity domain in the ALTO Entity Domain Registry
            following Section 9.2.2 of this document.

      *  If no (e.g., pid name, ane name or country code): Proceed with
         the ALTO Entity Domain registration as described in
         Section 9.2.2.

9.2.2.  ALTO Entity Domain Registration Process

   New ALTO entity domains are assigned after IETF Review [RFC5226] to
   ensure that proper documentation regarding the new ALTO entity
   domains and their security considerations has been provided.  RFCs
   defining new entity domains SHOULD indicate how an entity in a
   registered 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 identifiers MUST conform to the
   syntactical requirements specified in Section 2.3.  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.

   o  Entity Identifier Encoding: The procedure for encoding the
      identifier of an entity of the registered type as an EntityId (see
      Section 2.4).  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
      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.



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   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 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.

9.3.  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 2.5.  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         | Dependencies and Interpretation   |
   |            | Semantics        |                                   |
   +------------+------------------+-----------------------------------+
   | ipv4:pid   | PID for the IPv4 | application/alto-networkmap+json, |
   |            | entity           | where the PID names are defined   |
   | ipv6:pid   | PID for the IPv6 | application/alto-networkmap+json, |
   |            | entity           | where the PID names are defined   |
   +------------+------------------+-----------------------------------+

                   Table 3: ALTO Entity Property Types.

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

   o  Identifier: The unique id for the desired ALTO entity property
      type.  The format MUST be as defined in Section 2.5 of this



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      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.

   o  Dependencies and Interpretation: Dependent ALTO resources MAY be
      required by ALTO clients to interpret ALTO entity properties.
      Hence, a document defining a new type SHOULD provide a sequence of
      media types in which the dependent ALTO resources are and the
      guidance how ALTO clients use them to interpret the property.

   This specification requests registration of the identifiers
   "ipv4:pid" and "ipv6:pid", as shown in Table 3.

9.4.  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.

10.  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>.

   [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>.

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


































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