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ALTO WG                                                         W. Roome
Internet-Draft                                           Nokia Bell Labs
Intended status: Standards Track                                 S. Chen
Expires: June 13, 2019                                 Tongji University
                                                          S. Randriamasy
                                                         Nokia Bell Labs
                                                                 Y. Yang
                                                         Yale University
                                                                J. Zhang
                                                       Tongji University
                                                       December 10, 2018


                Unified Properties for the ALTO Protocol
                  draft-ietf-alto-unified-props-new-05

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 June 13, 2019.






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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definitions and Concepts  . . . . . . . . . . . . . . . . . .   4
     2.1.  Entity  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Entity Domain . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  Domain Name . . . . . . . . . . . . . . . . . . . . . . .   5
     2.4.  Entity Address  . . . . . . . . . . . . . . . . . . . . .   5
     2.5.  Property Name . . . . . . . . . . . . . . . . . . . . . .   6
     2.6.  Hierarchy and Inheritance . . . . . . . . . . . . . . . .   6
     2.7.  Relationship with Other ALTO Resources  . . . . . . . . .   6
   3.  Entity Domains  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Internet Address Domains  . . . . . . . . . . . . . . . .   7
       3.1.1.  IPv4 Domain . . . . . . . . . . . . . . . . . . . . .   7
       3.1.2.  IPv6 Domain . . . . . . . . . . . . . . . . . . . . .   8
       3.1.3.  Hierarchy and Inheritance of ipv4/ipv6 Domains  . . .   8
     3.2.  PID Domain  . . . . . . . . . . . . . . . . . . . . . . .   9
       3.2.1.  Domain Name . . . . . . . . . . . . . . . . . . . . .   9
       3.2.2.  Domain-Specific Entity Addresses  . . . . . . . . . .  10
       3.2.3.  Hierarchy and Inheritance . . . . . . . . . . . . . .  10
       3.2.4.  Relationship To Internet Addresses Domains  . . . . .  10
     3.3.  Internet Address Properties vs. PID Properties  . . . . .  10
   4.  Property Map  . . . . . . . . . . . . . . . . . . . . . . . .  10
     4.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  11
     4.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  11
     4.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  11
     4.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  11
     4.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  12
   5.  Filtered Property Map . . . . . . . . . . . . . . . . . . . .  13
     5.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  13
     5.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  13
     5.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  13



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     5.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  14
     5.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     5.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  14
   6.  Impact on Legacy ALTO Servers and ALTO Clients  . . . . . . .  16
     6.1.  Impact on Endpoint Property Service . . . . . . . . . . .  16
     6.2.  Impact on Resource-Specific Properties  . . . . . . . . .  16
     6.3.  Impact on the pid Property  . . . . . . . . . . . . . . .  16
     6.4.  Impact on Other Properties  . . . . . . . . . . . . . . .  17
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
     7.1.  Network Map . . . . . . . . . . . . . . . . . . . . . . .  17
     7.2.  Property Definitions  . . . . . . . . . . . . . . . . . .  17
     7.3.  Information Resource Directory (IRD)  . . . . . . . . . .  18
     7.4.  Property Map Example  . . . . . . . . . . . . . . . . . .  20
     7.5.  Filtered Property Map Example #1  . . . . . . . . . . . .  21
     7.6.  Filtered Property Map Example #2  . . . . . . . . . . . .  21
     7.7.  Filtered Property Map Example #3  . . . . . . . . . . . .  22
     7.8.  Filtered Property Map Example #4  . . . . . . . . . . . .  23
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25
     9.1.  application/alto-* Media Types  . . . . . . . . . . . . .  25
     9.2.  ALTO Entity Domain Registry . . . . . . . . . . . . . . .  26
       9.2.1.  Consistency Procedure between ALTO Address Type
               Registry and ALTO Entity Domain Registry  . . . . . .  27
       9.2.2.  ALTO Entity Domain Registration Process . . . . . . .  28
     9.3.  ALTO Entity Property Type Registry  . . . . . . . . . . .  29
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

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



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   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
   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 would subsume 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 is a generalized concept of the endpoint defined in
   Section 2.1 of [RFC7285].  An entity is an object with a (possibly
   empty) set of properties.  Each entity MUST be in one and only one
   domain, such as the IPv4 domain or the IPv6 domain, and has a unique
   address.



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2.2.  Entity Domain

   An entity domain is a set of entities.  Examples of domains are the
   Internet address domains (see Section 3.1 and the PID domain (see
   Section 3.2).  This document will define the domains precisely below.

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.

2.4.  Entity Address

   Each entity has a unique address of the format:

       EntityAddr ::= DomainName : DomainSpecificEntityAddr

   Examples from the IP domains include individual 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 EntityAddr is used in this document to denote a JSON string
   with an entity address in this format.

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




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2.5.  Property Name

   The space of entity property names associated with entities defined
   by this document is a superset of the endpoint property names defined
   by [RFC7285].  Thus endpoint property names registered with the "ALTO
   Endpoint Property Type Registry" MUST be defined in Section 9.3 of
   this document.  The type PropertyName denotes a JSON string with a
   property name in this format.

   This document defines property names in the domain-specific context.
   This design is to enforce that each property name MUST be registered
   for every applicable entity domains individually.  This design
   decision is adopted because of the following considerations:

   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"
      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, such as an Internet
      address, 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 a Network
      Map defining this "pid" entity.

2.6.  Hierarchy and Inheritance

   Entities in a given domain MAY form a hierarchy based on entity
   addresses, 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"



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   property, whose value is the name of the PID containing that endpoint
   in the associated network map.

   This document takes a different approach.  Instead of defining the
   dependency by qualifying the property name, this document attaches
   the dependency to the entity domains.  Thus each resource-specific
   property of all entities in a specific domain depends on the same
   resources; the properties of entities in another domain may depend on
   another resource.  For example, in a single property map, the "pid"
   property of all entities in an Internet address domain MUST depend on
   the same network map.  Each property of all entities in the PID
   domain MUST also depend on a network map; but different properties
   may depend on different network maps.

   Specifically, this document uses the "uses" and "dependent-vtags"
   fields defined in Sections 9.1.5 and 11.1 of [RFC7285], respectively,
   to specify the preceding dependency: the "uses" field of an IRD entry
   providing entity domain related resources (see Property Map and
   Filtered Property Map resources below) specifies the dependent
   resources, and the "dependent-vtags" field specifies dependency in
   message responses.

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 addresses, and (3) hierarchy and inheritance
   semantics.

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 Addresses

   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



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   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 Addresses

   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
   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.




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   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.

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







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3.2.2.  Domain-Specific Entity Addresses

   The entity addresses 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.

   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.




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   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 names of the properties
   returned for entities in those domains.  The semantics is that each
   domain in "entity-domains" provides all properties defined in
   "properties".  If a property in "properties" is NOT supported by a
   domain in "entity-domains", the server can declare different property
   maps to conform to the semantics.

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 depend
   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"



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   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 {
         EntityAddr -> EntityProps;
       } PropertyMapData;

       object {
         PropertyName -> 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
   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.






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

   with fields:

   entities:  List of entity addresses 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.





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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 address 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 address is an invalid address in the entity domain.

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

      If an entity address 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 address.

   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



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      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 address block (e.g., an
      "ipv4" or "ipv6" entity), the response MUST cover properties for
      all addresses 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.

   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.





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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
   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
   addresses.  An ALTO server determines the value of "pid" for an
   address block C as the rules defined in Section 5.6.





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   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 addresses, rather than just individual
   addresses, 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:

                                   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:








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                                            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
   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",



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            "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" ],
              "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" ]
           }
         },



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         "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

   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"}
     }
   }






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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" ]
   }

   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".




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   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" ]
   }

   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.




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   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" ]
   }

   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.





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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" : ["pid:pid1",
                   "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": {
       "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.





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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.

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].




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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).

9.2.  ALTO Entity Domain Registry

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
















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

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
   address 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 address for the candidate domain
      identifier.  This has been done for the identifiers "ipv4" and
      "ipv6" in Table 2.



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   o  Whether the candidate entity address 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 addresses 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?

            -  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 EntityAddr, 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:



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

   o  Entity Address Encoding: The procedure for encoding the address of
      an entity of the registered type as an EntityAddr (see
      Section 2.4).  If corresponding entity addresses of an entity
      domain match a known "network" address type, the Entity Address
      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 address 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.

   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 addresses
      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".

   To distinguish with the "ALTO Endpoint Property Type Registry", this
   new registry is for properties in all possible entity domains, rather
   than just the Internet address domain.  So it is necessary to define
   and process the consistency between the two registries.

   In the meanwhile, because every entity property is owned by some
   entity domains, for each registered entity property, the ALTO Entity
   Property Registry MUST define its accepted entity domains and its
   semantics in every different accepted entity domains.




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   Also, an entity property MAY depend on several other ALTO resources.
   The ALTO Entity Property Registry MUST specify the media types of all
   dependent resources and how the ALTO client uses them in order.

   TODO: The registry format and the initial content

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>.

   [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>.

Authors' Addresses







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

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


   Shiwei Dawn Chen
   Tongji University
   4800 Caoan Road
   Shanghai  201804
   China

   Email: dawn_chen_f@hotmail.com


   Sabine Randriamasy
   Nokia Bell Labs
   Route de Villejust
   NOZAY  91460
   FRANCE

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


   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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