[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-roome-alto-unified-props-new) 00 01 02 03

ALTO WG                                                         W. Roome
Internet-Draft                                           Nokia Bell Labs
Intended status: Standards Track                                 S. Chen
Expires: September 6, 2018                             Tongji University
                                                          S. Randriamasy
                                                         Nokia Bell Labs
                                                                 Y. Yang
                                                         Yale University
                                                                J. Zhang
                                                       Tongji University
                                                           March 5, 2018


                Unified Properties for the ALTO Protocol
                  draft-ietf-alto-unified-props-new-03

Abstract

   This document extends the Application-Layer Traffic Optimization
   (ALTO) Protocol [RFC7285] by generalizing the concept of "endpoint
   properties" to other entity domains, 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 http://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 6, 2018.






Roome, et al.           Expires September 6, 2018               [Page 1]


Internet-Draft             Unified Properties                 March 2018


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
   (http://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.  Domain  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Domain Name . . . . . . . . . . . . . . . . . . . . . . .   4
     2.4.  Entity Address  . . . . . . . . . . . . . . . . . . . . .   5
     2.5.  Property Name . . . . . . . . . . . . . . . . . . . . . .   5
     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 . . . . . . . . . . . . . . . . . . . . .   7
       3.1.3.  Hierarchy and Inheritance of ipv4/ipv6 Domains  . . .   8
       3.1.4.  Relationship to Network Maps  . . . . . . . . . . . .   9
     3.2.  PID Domain  . . . . . . . . . . . . . . . . . . . . . . .  10
       3.2.1.  Domain Name . . . . . . . . . . . . . . . . . . . . .  10
       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 Resource . . . . . . . . . . . . . . . . . . . .  11
     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 Resource  . . . . . . . . . . . . . . .  12
     5.1.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .  13
     5.2.  HTTP Method . . . . . . . . . . . . . . . . . . . . . . .  13



Roome, et al.           Expires September 6, 2018               [Page 2]


Internet-Draft             Unified Properties                 March 2018


     5.3.  Accept Input Parameters . . . . . . . . . . . . . . . . .  13
     5.4.  Capabilities  . . . . . . . . . . . . . . . . . . . . . .  13
     5.5.  Uses  . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     5.6.  Response  . . . . . . . . . . . . . . . . . . . . . . . .  14
   6.  Impact on Legacy ALTO Servers and ALTO Clients  . . . . . . .  14
     6.1.  Impact on Endpoint Property Service . . . . . . . . . . .  14
     6.2.  Impact on Resource-Specific Properties  . . . . . . . . .  14
     6.3.  Impact on the "pid" Property  . . . . . . . . . . . . . .  15
     6.4.  Impact on Other Properties  . . . . . . . . . . . . . . .  15
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  15
     7.1.  Network Map . . . . . . . . . . . . . . . . . . . . . . .  15
     7.2.  Property Definitions  . . . . . . . . . . . . . . . . . .  16
     7.3.  Information Resource Directory (IRD)  . . . . . . . . . .  16
     7.4.  Property Map Example  . . . . . . . . . . . . . . . . . .  18
     7.5.  Filtered Property Map Example #1  . . . . . . . . . . . .  18
     7.6.  Filtered Property Map Example #2  . . . . . . . . . . . .  19
     7.7.  Filtered Property Map Example #3  . . . . . . . . . . . .  20
     7.8.  Filtered Property Map Example #4  . . . . . . . . . . . .  21
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
     9.1.  application/alto-* Media Types  . . . . . . . . . . . . .  23
     9.2.  ALTO Entity Domain Registry . . . . . . . . . . . . . . .  24
     9.3.  ALTO Endpoint Property Type Registry  . . . . . . . . . .  26
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   The ALTO protocol [RFC7285] introduced the concept of "properties"
   attached to "endpoint addresses", and defined the Endpoint Property
   Service (EPS) to allow 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.  The EPS cannot be extended to new
   entity domains.  Instead, new services, with new request and response
   messages, would have to be defined for each new entity domain.

   Second, the EPS is only defined as a POST-mode service.  Clients must
   request the properties for an explicit set of 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 lookup without querying the ALTO
   server.  [RFC7285] does not define an equivalent service for endpoint
   properties.  At first a map might seem impractical, because it could
   require enumerating the property value for every possible endpoint.



Roome, et al.           Expires September 6, 2018               [Page 3]


Internet-Draft             Unified Properties                 March 2018


   But in practice, it is highly unlikely that properties will be
   defined for every address.  It is much more likely that properties
   will only be defined for a subset of addresses, and that subset would
   be small enough to enumerate.  This is particularly true if blocks of
   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 resource types, namely Property Maps
   (see Section 4) and Filtered Property Maps (see Section 5).  The
   former are GET-mode resources which return the property values for
   all entities in a domain, and are analogous to the ALTO's Network
   Maps and Cost Maps.  The latter are POST-mode resources which return
   the values for a set of properties and entities requested by the
   client, and are analogous to the ALTO's Filtered Network Maps and
   Filtered Cost Maps.

   Entity domains and property names are extensible.  New 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 by the ALTO protocol.

   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

   An entity is an object with a (possibly empty) set of properties.
   Every entity is in a domain, such as the IPv4 and IPv6 domains, and
   has a unique address.

2.2.  Domain

   A domain is a family of entities.  Two examples are the Internet
   address and PID domain (see Section 3.1 and Section 3.2) that this
   document will define.

2.3.  Domain Name

   Each 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).




Roome, et al.           Expires September 6, 2018               [Page 4]


Internet-Draft             Unified Properties                 March 2018


   For example, the names "ipv4" and "ipv6" identify objects in the
   Internet address domain (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 in that domain, as well as any hierarchical or
   inheritance rules for those entities, MUST be specified at the same
   time.

2.4.  Entity Address

   Each entity has a unique address of the format:

       domain-name : domain-specific-entity-address

   Examples from the IP domain 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
   domain, and MUST be specified when registering a new 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 domain is registered.

   Note that an entity address MAY have different textual
   representations, for a given 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 Name

   The space of property names associated with entities defined by this
   document is the same as, and is shared with, the endpoint property
   names defined by [RFC7285].  Thus entity property names are as
   defined in Section 10.8.2 of that document, and must be registered
   with the "ALTO Endpoint Property Type Registry" defined in
   Section 9.3 of that document.  The type PropertyName denotes a JSON
   string with a property name in this format.

   This document defines uniform property names specified in a single
   property name space rather than being scoped by a specific domain,
   although some properties may only be applicable for particular



Roome, et al.           Expires September 6, 2018               [Page 5]


Internet-Draft             Unified Properties                 March 2018


   domains.  This design decision is to enforce a design so that similar
   properties are named similarly.  The interpretation of the value of a
   property, however, may depend on the domain.  For example, suppose
   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.  When applied to
   an entity that represents a set of computers, such as a CIDR, the
   property would be the location of the center of that set.  If it is
   necessary to represent the bounding box of a set of hosts, another
   property, such as "geo-region", should be defined.

2.6.  Hierarchy and Inheritance

   Entities in a given domain MAY form hierarchy based on entity
   address.  Each 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.  If and only if the property of an entity
   is undefined, the hierarchy and inheritance rules are applied.

2.7.  Relationship with Other ALTO Resources

   [RFC7285] recognizes that some properties MAY be specific to another
   ALTO resource, such as a network map.  Accordingly [RFC7285] defines
   the concept of "resource-specific endpoint properties" (see
   Section 10.8.1), 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.

   This document takes a different approach.  Instead of defining the
   dependency by qualifying the property name, this document attaches
   the dependency to the domains.  Thus all properties of a specific
   domain depend on the same resource, the properties of another domain
   may depend on another resource.  For example, entities in the PID
   domain depend on a network map.

   The "uses" field in an IRD entry defines the dependencies of a
   property map resource, and the "dependent-vtags" field in a property
   map response defines the dependencies of that map.  These fields are
   defined in Sections 9.1.5 and 11.1 of [RFC7285], respectively.

   The "uses" field in an IRD entry MUST NOT include two dependent
   resources with the same media type.  This is similar to how [RFC7285]
   handles dependencies between cost maps and network maps.  Recall that
   cost maps present the costs between PIDs, and PID names depend on a



Roome, et al.           Expires September 6, 2018               [Page 6]


Internet-Draft             Unified Properties                 March 2018


   network map.  If an ALTO server provides the "routingcost" metric for
   the network maps "net1" and "net2", then the server defines two
   separate cost maps, one for "net1" and the other for "net2".

   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 extensions defined in this
   document, would, instead, offer two different Property Maps for the
   "pid" property, one depending on "net1", the other on "net2".

3.  Entity Domains

   This document defines the following entity domains.  For the
   definition of each domain, it includes the following template: domain
   name, domain-specific addresses, and hierarchy and inheritance
   semantics.

3.1.  Internet Address Domains

   The document defines two domains (IPv4 and IPv6) for Internet
   addresses.  Both domains include individual addresses and blocks of
   addresses.

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
   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






Roome, et al.           Expires September 6, 2018               [Page 7]


Internet-Draft             Unified Properties                 March 2018


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 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 property P is not
   defined for a block C, but is defined for some block C' which prefix-
   matches 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 the 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:













Roome, et al.           Expires September 6, 2018               [Page 8]


Internet-Draft             Unified Properties                 March 2018


                         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 A 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 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.

3.1.4.  Relationship to Network Maps

   An Internet address domain MAY be associated with an ALTO network map
   resource.  Logically, there is a map of Internet address entities to
   property values for each network map defined by the ALTO server, plus
   an additional property map for Internet address entities which are
   not associated with a network map.  So, if there are n network maps,
   the server can provide n+1 maps of Internet address entities to
   property values.  These maps are separate from each other.  The
   prefixes in the property map do not have to correspond to the
   prefixes defining the network map's PIDs.  For example, the property
   map for a network map MAY assign properties to "ipv4:192.0.2.0/24"
   even if that prefix is not associated with any PID in the network
   map.




Roome, et al.           Expires September 6, 2018               [Page 9]


Internet-Draft             Unified Properties                 March 2018


3.2.  PID Domain

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

3.2.1.  Domain Name

   pid

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 domain is best for a property.  In
   general, the Internet address domain is 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




Roome, et al.           Expires September 6, 2018              [Page 10]


Internet-Draft             Unified Properties                 March 2018


   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 Resource

   A Property Map returns the properties defined for all entities in one
   or more domains.

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

4.1.  Media Type

   The media type of an ALTO Property Map resource is "application/alto-
   propmap+json".

4.2.  HTTP Method

   An ALTO Property Map resource 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 domain-types<1..*>;
         PropertyName prop-types<1..*>;
       } PropertyMapCapabilities;

   where "domain-types" is an array with the domains of the entities in
   this property map, and "prop-types" is an array with the names of the
   properties returned for entities in those domains.

4.5.  Uses

   An array with the resource ID(s) of resource(s) with which the
   domains in this map are associated.  In most cases, this array will
   have at most one ID, for example, for a network map resource.
   However, the "uses" field MUST NOT contain two resources of the same
   resource type.  For example, if a property map depends on network map
   resource, the "uses" field MUST include exactly one network map
   resource.




Roome, et al.           Expires September 6, 2018              [Page 11]


Internet-Draft             Unified Properties                 March 2018


4.6.  Response

   If the 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.  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 domain's
   inheritance rules to deduce those values.

5.  Filtered Property Map Resource

   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 and Section 7.7 give examples of filtered
   property map requests and responses.





Roome, et al.           Expires September 6, 2018              [Page 12]


Internet-Draft             Unified Properties                 March 2018


5.1.  Media Type

   The media type of an ALTO Property Map resource is "application/alto-
   propmap+json".

5.2.  HTTP Method

   An ALTO Filtered Property Map resource 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 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.







Roome, et al.           Expires September 6, 2018              [Page 13]


Internet-Draft             Unified Properties                 March 2018


5.5.  Uses

   An array with the resource ID(s) of resource(s) with which the
   domains in this map are associated.  In most cases, this array will
   have at most one ID, and it will be for a network map resource.

5.6.  Response

   The response is the same as for the property map (see Section 4.6),
   except that it only includes the entities and properties requested by
   the client.

   Also, the Filtered Property Map response MUST include all inherited
   property values for the specified entities (unlike the Full Property
   Map, the Filtered Property Map response does not include enough
   information for the client to calculate the inherited values).

   If the ALTO server does not define a requested property's value for a
   particular entity, then it MUST omit that property from the response
   for only that endpoint.

   If the ALTO server does not support a requested entity's domain, then
   it MUST return an E_INVALID_FIELD_VALUE error defined in
   Section 8.5.2 of [RFC7285].

6.  Impact on Legacy ALTO Servers and ALTO Clients

6.1.  Impact on Endpoint Property Service

   The Property Maps defined in this document provide the same
   functionality as the Endpoint Property Service (EPS) defined in
   Section 11.4 of [RFC7285].  Accordingly, it is RECOMMENDED that the
   EPS be deprecated in favor of Property Maps.  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 resources 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.



Roome, et al.           Expires September 6, 2018              [Page 14]


Internet-Draft             Unified Properties                 March 2018


6.3.  Impact on the "pid" Property

   Section 7.1.1 of [RFC7285] defines the resource-specific endpoint
   property "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 Endpoint Property Service
   MUST use that definition, and that syntax, in the EPS resource.

   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 resource 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 resource for
   each one.

   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 follows.  Let CS be the set of all address blocks
   in the network map.  If C is in CS, then the value of "pid" is the
   name of the PID associated with C.  Otherwise, find the longest block
   C' in CS such that C' prefix-matches C, but is shorter than C.  If
   there is such a block C', the value of "pid" is the name of the PID
   associated with C'.  If not, then "pid" has no value for block C.

   Note that although an ALTO server MAY provide a GET-mode property map
   resource 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:






Roome, et al.           Expires September 6, 2018              [Page 15]


Internet-Draft             Unified Properties                 March 2018


            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

                       Figure 3: Example Network Map

7.2.  Property Definitions

   The examples in this section use four additional properties, "ISP",
   "ASN", "country" and "state", with the following values:

                                   ISP    ASN   country   state
           ipv4:192.0.2.0/24:    BitsRus   -      us       -
           ipv4:192.0.2.0/28:       -    12345    -        NJ
           ipv4:192.0.2.16/28:      -    12345    -        CT
           ipv4:192.0.2.0:          -      -      -        PA

                     Figure 4: Example Property Values

7.3.  Information Resource Directory (IRD)

   The following IRD defines the relevant resources of the ALTO server.
   It provides two Property Map resources, one for the "ISP" and "ASN"
   properties, and another for the "country" and "state" properties.
   The server could have provided a Property Map resource 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": { ... },
      "resources" : {
         "default-network-map" : {
            "uri" : "http://alto.example.com/networkmap",



Roome, et al.           Expires September 6, 2018              [Page 16]


Internet-Draft             Unified Properties                 March 2018


            "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" : {
              "domain-types": [ "ipv4", "ipv6" ],
              "prop-types" : [  "country", "state" ]
            }
         },
         "isp-asn-property-map" : {
            "uri" : "http://alto.example.com/propmap/full/inet-ia",
            "media-type" : "application/alto-propmap+json",
            "capabilities" : {
              "domain-types": [ "ipv4", "ipv6" ],
              "prop-types" : [ "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" : {
              "domain-types": [ "ipv4", "ipv6" ],
              "prop-types" : [ "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" : {
              "domain-types" : [ "ipv4", "ipv6" ],
              "prop-types" : [ "pid" ]
            }
         },
         "availbw-property-map" : {
            "uri" : "http://alto.example.com/propmap/lookup/availbw",
            "media-type" : "application/alto-propmap+json",
            "accepts" : "application/alto-propmapparams+json",
            "capabilities" : {
              "domain-types" : [ "ane" ],
              "prop-types" : [ "availbw", "delay" ]
            }
         },
         "legacy-pid-property-map" : {



Roome, et al.           Expires September 6, 2018              [Page 17]


Internet-Draft             Unified Properties                 March 2018


            "uri" : "http://alto.example.com/legacy/eps-pid",
            "media-type" : "application/alto-endpointprop+json",
            "accepts" : "application/alto-endpointpropparams+json",
            "capabilities" : {
              "prop-types" : [ "default-network-map.pid" ]
            }
         }
      }

                           Figure 5: 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 the response does not include the entity
   "ipv4:192.0.2.0", because it does not have a value for either of
   those properties.  Also note that the entities "ipv4:192.0.2.0/28"
   and "ipv4:192.0.2.16/28" are refinements of "ipv4:192.0.2.0/24", and
   hence inherit its value for "ISP" property.  But because that value
   is inherited, it is not explicitly listed in the property map.

   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": {
       "ipv4:192.0.2.0/24":   {"ISP": "BitsRus"},
       "ipv4:192.0.2.0/28":   {"ASN": "12345"},
       "ipv4:192.0.2.16/28":  {"ASN": "12345"}
     }
   }

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.





Roome, et al.           Expires September 6, 2018              [Page 18]


Internet-Draft             Unified Properties                 March 2018


   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 none of the returned property values is
   explicitly defined; all values are derived by the inheritance rules
   for Internet address entities.

   Also note the "ASN" property has the value "12345" for both the
   blocks "ipv4:192.0.2.0/28" and "ipv4:192.0.2.16/28", so every address
   in the block "ipv4:192.0.2.0/27" has that property value.  However
   the block "ipv4:192.0.2.0/27" itself does not have a value for "ASN":
   address blocks cannot inherit properties from blocks with longer
   prefixes, even if every such block has the same value.








Roome, et al.           Expires September 6, 2018              [Page 19]


Internet-Draft             Unified Properties                 March 2018


   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",
                    "ipv4:192.0.2.0/27",
                    "ipv4:192.0.2.0/28" ],
     "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"},
       "ipv4:192.0.2.0/27":  {"country": "us"},
       "ipv4:192.0.2.0/28":  {"ASN": "12345",
                              "country": "us",
                              "state": "NJ"}
    }
   }

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 value of "pid" for the prefix "ipv4:192.0.2.0/26" is
   "pid1", even though all addresses in that block are in "pid2",
   because "ipv4:192.0.2.0/25" is the longest prefix in the network map
   which prefix-matches "ipv4:192.0.2.0/26", and that prefix is in
   "pid1".













Roome, et al.           Expires September 6, 2018              [Page 20]


Internet-Draft             Unified Properties                 March 2018


   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" : [
                   "ipv4:192.0.2.0",
                   "ipv4:192.0.2.16",
                   "ipv4:192.0.2.64",
                   "ipv4:192.0.2.128",
                   "ipv4:192.0.2.0/26",
                   "ipv4:192.0.2.0/30" ],
     "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": {
       "ipv4:192.0.2.0":     {"pid": "pid2"},
       "ipv4:192.0.2.16":    {"pid": "pid2"},
       "ipv4:192.0.2.64":    {"pid": "pid1"},
       "ipv4:192.0.2.128":   {"pid": "defaultpid"},
       "ipv4:192.0.2.0/26":  {"pid": "pid1"},
       "ipv4:192.0.2.0/30":  {"pid": "pid2"}
     }
   }

7.8.  Filtered Property Map Example #4

   The following example uses the Filtered Property Map resource to
   request the "availbw" property for several abstract network elements.








Roome, et al.           Expires September 6, 2018              [Page 21]


Internet-Draft             Unified Properties                 March 2018


   POST /propmap/lookup/availbw 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" : [
                   "ane:L001",
                   "ane:Lae0",
                   "ane:L3eb ],
     "properties" : [ "availbw" ]
   }


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

   {
     "property-map": {
       "ane:L001":    {"availbw": "55"},
       "ane:Lae0":    {"availbw": "70"},
       "ane:L3eb":    {"availbw": "40"}
     }
   }

8.  Security Considerations

   As discussed in Section 15 of [RFC7285], properties MAY have
   sensitive customer-specific information.  If this is the case, an
   ALTO Server MAY limit access to those properties by providing several
   different Property Maps.  For non-sensitive properties, the ALTO
   Server would provide a URI which accepts requests from any client.
   Sensitive properties, on the other hand, would only be available via
   a secure URI which would require client authentication.

   Also, while technically this document does not introduce any security
   risks not inherent in the Endpoint Property Service defined by
   [RFC7285], the GET-mode property map resource defined in this
   document does make it easier for a client to download large numbers
   of property values.  Accordingly, an ALTO Server SHOULD limit GET-
   mode Property Maps to properties which do not contain sensitive data.








Roome, et al.           Expires September 6, 2018              [Page 22]


Internet-Draft             Unified Properties                 March 2018


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: ~ Magic number(s): ~ n/a File extension(s): ~
   This document uses the mime type to refer to protocol messages and



Roome, et al.           Expires September 6, 2018              [Page 23]


Internet-Draft             Unified Properties                 March 2018


   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 Address Encoding  | Hierarchy & Inheritance  |
   +-------------+--------------------------+--------------------------+
   | ipv4        | See Section 3.1.1        | See Section 3.1.3        |
   | ipv6        | See Section 3.1.2        | See Section 3.1.3        |
   | pid         | See Section 3.2          | None                     |
   +-------------+--------------------------+--------------------------+

                    Table 2: ALTO Entity Domain Names.

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

   This registry is considered as an extension of the "ALTO Address Type
   Registry" defined in Section 14.4 of [RFC7285].  In particularly,

   o  An entity MAY or MAY NOT be an endpoint.  For example, "pid" is
      registered as an entity domain in Table 2, but it is not an
      endpoint address type.

   o  An endpoint MUST be an entity.  For example, "ipv4" and "ipv6" are
      already registered in "ALTO Address Type Registry" in [RFC7285],
      so they MUST be registered as entity domains.

   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



Roome, et al.           Expires September 6, 2018              [Page 24]


Internet-Draft             Unified Properties                 March 2018


   defining new entity domains SHOULD indicate how an entity in a
   registered domain is encoded as an EntityName, 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.

   When a new address type is registered in the ALTO Address Type
   Registry [RFC7285], the same identifier MUST be also registered in
   the ALTO Entity Domain Registry.  And the Entity Address Encoding of
   this entity 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.

   Requests 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 Address Encoding: The procedure for encoding the address of
      an entity of the registered type as an EntityAddr (see
      Section 2.4).

   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  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.








Roome, et al.           Expires September 6, 2018              [Page 25]


Internet-Draft             Unified Properties                 March 2018


9.3.  ALTO Endpoint Property Type Registry

   The ALTO Endpoint Property Type Registry was created by [RFC7285].
   If possible, the name of that registry SHOULD be changed to "ALTO
   Entity Property Type Registry", to indicate that it is not restricted
   to Endpoint Properties.  If it is not feasible to change the name,
   the description MUST be amended to indicate that it registers
   properties in all domains, rather than just the Internet address
   domain.

10.  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>.





Roome, et al.           Expires September 6, 2018              [Page 26]


Internet-Draft             Unified Properties                 March 2018


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


   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




Roome, et al.           Expires September 6, 2018              [Page 27]


Html markup produced by rfcmarkup 1.126, available from https://tools.ietf.org/tools/rfcmarkup/