ALTO WG                                                     G. Bernstein
Internet-Draft                                         Grotto Networking
Intended status: Standards Track                                 S. Chen
Expires: September 6, 2018 January 3, 2019                               Tongji University
                                                                  K. Gao
                                                     Tsinghua University
                                                                  Y. Lee
                                                                  Huawei
                                                                W. Roome
                                                               M. Scharf
                                                                   Nokia
                                                                 Y. Yang
                                                         Yale University
                                                                J. Zhang
                                                       Tongji University
                                                           March 5,
                                                            July 2, 2018

                 ALTO Extension: Path Vector Cost Type
                   draft-ietf-alto-path-vector-03.txt
                     draft-ietf-alto-path-vector-04

Abstract

   The Application-Layer Traffic Optimization (ALTO) protocol [RFC7285]
   has defined several resources cost maps and services endpoint cost maps to provide clients with basic network
   information.  However, the base ALTO protocol and
   latest extensions only they provide end-to-end metrics, only scalar (numerical or
   ordinal) cost mode values, which are insufficient to satisfy the
   demands of solving more complex network optimization problems.  This
   document introduces an extension to the base ALTO protocol, namely
   the path-vector extension, which allows ALTO clients to query
   information such as capacity regions for a given set of flows.  A
   non-normative example called multi-flow scheduling is presented to
   illustrate the limitations of existing ALTO (endpoint) endpoint cost maps.
   After that, details of the extension are defined.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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. January 3, 2019.

Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Use Case: Capacity Region for Multi-Flow Scheduling . . . . .   5
   4.  Overview of Path Vector Extensions  . . . . . . . . . . . . .   7
     4.1.  New Cost Type to Encode Path Vectors  . . . . . . . . . .   7
     4.2.  New ALTO Entity Domain to Provide ANE Properties  . . . . . . .   8
     4.3.  New  Extended Cost Map/Endpoint Cost Service to Enable Multipart for Compound
           Resources . . . . . . . .   8
   5.  Path Vector Extension: Basic Data Types . . . . . . . . . . .   9
     5.1. . . . . .   8
   5.  Cost Type . . . . . . . . . . . . . . . . . . . . . . . .   9
       5.1.1. . .   8
     5.1.  Cost Mode: array  . . . . . . . . . . . . . . . . . . . .   9
       5.1.2.
     5.2.  Cost Metric: ane-path . . . . . . . . . . . . . . . . . .   9
       5.1.3.
     5.3.  Path Vector Cost Type Semantics . . . . . . . . . . . . .   9
     5.2.
   6.  ANE Domain  . . . . . . . . . . . . . . . . . . . . . . . . .  10
       5.2.1.
     6.1.  Domain Name . . . . . . . . . . . . . . . . . . . . . . .  10
       5.2.2.
     6.2.  Domain-Specific Entity Addresses  . . . . . . . . . . . .  10
       5.2.3.
     6.3.  Hierarchy and Inheritance . . . . . . . . . . . . . .  11
     5.3.  Abstract Network Element Name . . . . . . . . . . . . . .  11
   6.  10
   7.  Protocol Extensions for Path Vector Extension: Services . . . Compound Query  . . . . . . . . . . . .  11
     6.1.  10
     7.1.  Filtered Cost Map Extensions  . . . . . . . . . . . . . .  11
       6.1.1.
       7.1.1.  Capabilities  . . . . . . . . . . . . . . . . . . . .  11
       6.1.2.
       7.1.2.  Accept Input Parameters . . . . . . . . . . . . . . .  12
       6.1.3.
       7.1.3.  Response  . . . . . . . . . . . . . . . . . . . . . .  12
     6.2.

     7.2.  Endpoint Cost Service Extensions  . . . . . . . . . . . .  12
       6.2.1.
       7.2.1.  Capabilities  . . . . . . . . . . . . . . . . . . . .  12
       6.2.2.  13
       7.2.2.  Accept Input Parameters . . . . . . . . . . . . . . .  12
       6.2.3.  13
       7.2.3.  Response  . . . . . . . . . . . . . . . . . . . . . .  13
     6.3.  Multipart Cost Property Service .
   8.  Examples  . . . . . . . . . . . .  13
       6.3.1.  Media Type . . . . . . . . . . . . . .  13
     8.1.  Workflow  . . . . . . .  13
       6.3.2.  HTTP Method . . . . . . . . . . . . . . . . .  13
     8.2.  Information Resource Directory Example  . . . .  13
       6.3.3.  Accept Input Parameters . . . . .  14
     8.3.  Example # 1 . . . . . . . . . .  13
       6.3.4.  Capabilities . . . . . . . . . . . . .  16
     8.4.  Example # 2 . . . . . . .  14
       6.3.5.  Uses . . . . . . . . . . . . . . . .  18
     8.5.  Example #3  . . . . . . . .  14
       6.3.6.  Response . . . . . . . . . . . . . . .  20
   9.  Compatibility . . . . . . .  14
   7.  Examples . . . . . . . . . . . . . . . . .  22
     9.1.  Compatibility with Legacy ALTO Clients/Servers  . . . . .  22
     9.2.  Compatibility with Multi-Cost Extension . . . .  14
     7.1.  Workflow . . . . .  23
     9.3.  Compatibility with Incremental Update . . . . . . . . . .  23
   10. General Discussions . . . . . . . . .  15
     7.2.  Information Resource Directory Example . . . . . . . . .  15
     7.3.  Example # 1 . . .  23
     10.1.  Provide Calendar for Property Map  . . . . . . . . . . .  23
     10.2.  Constraint Tests for General Cost Types  . . . . . . . .  24
     10.3.  General Compound Resources Query .  17
     7.4.  Example # 2 . . . . . . . . . . .  24
   11. Security Considerations . . . . . . . . . . . .  18
   8.  Compatibility . . . . . . .  24
     11.1.  Privacy Concerns . . . . . . . . . . . . . . . . .  19
     8.1.  Compatibility with Legacy ALTO Clients/Servers . . .  24
     11.2.  Resource Consumption on ALTO Servers . .  19
     8.2.  Compatibility with Multi-Cost Extensions . . . . . . . .  20
     8.3.  Compatibility with Incremental Update . . . . . . . . . .  20
   9.  Design Decisions and Discussions  . . . . . . . . . . . . . .  20
     9.1.  Provide More General Calendar Extension . . . . . . . . .  20
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  21
     10.1.  Privacy Concerns . . . . . . . . . . . . . . . . . . . .  21
     10.2.  Resource Consumption on ALTO Servers . . . . . . . . . .  21
   11.  25
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
     11.1.  25
     12.1.  ALTO Cost Mode Registry  . . . . . . . . . . . . . . . .  21
     11.2.  25
     12.2.  ALTO Cost Metric Registry  . . . . . . . . . . . . . . .  22
     11.3.  25
     12.3.  ALTO Entity Domain Registry . . . . . . . . . . . . . .  22
     11.4. . . . .  25
     12.4.  ALTO Network Element Property Type Registry  . . . . . .  22
   12.  26
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  22
   13.  26
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     13.1.  26
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  23
     13.2.  26
     14.2.  Informative References . . . . . . . . . . . . . . . . .  23  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24  27

1.  Introduction

   The base ALTO protocol [RFC7285] is designed to expose network
   information through services such as Cost Map cost map and Endpoint Cost endpoint cost
   service.  These services use an extreme "single-node" network view
   abstraction, which represents the whole network with a single node
   and hosts with "endpoint groups" directly connected to the node.

   Although the "single-node" network view abstraction works well in
   many settings, it lacks the ability to support emerging use cases,
   such as applications requiring large bandwidth or latency sensitivity
   [I-D.bernstein-alto-topo], and inter-datacenter data transfers
   [I-D.lee-alto-app-net-info-exchange].  For these use cases,
   applications require a more powerful network view abstraction beyond
   the "single-node" abstraction to support application capabilities, in
   particular, the ability of multi-flow scheduling.

   To support capabilities like multi-flow scheduling,
   [I-D.yang-alto-topology] provides many candidate network view
   abstractions.  This this document
   uses one of those abstractions called a "path vector" abstraction. abstraction to represent more detailed network
   graph information like capacity regions.  The path vector abstraction use
   uses path vectors with abstract network elements to provide network
   graph view for applications.  Here, abstract network elements can be links,
   switches, middleboxes and their aggregations.  And a  A path vector
   presents consists of a sequence of abstract network elements
   Abstract Network Elements (ANEs) that end-to-end traffic goes
   through.  Each abstract network element  ANEs can own several be links, switches, middleboxes, their
   aggregations, etc.; they have properties like "bandwidth" and "delay". "bandwidth", "delay",
   etc.  These information may help the application avoid network congestion, achieving
   congestion and achieve better application performance.

   Providing path vector abstraction using ALTO introduces the following
   requirements:

   o  Encoding path vectors
   additional requirements (ARs):

   AR-1:  The ALTO protocol SHOULD include the support for encoding
      array-like cost values rather than scalar cost values in cost maps:
      Cost maps allow only
      or endpoint cost maps.

      The ALTO server providing path vector abstraction SHOULD convey
      sequences of ANEs between sources and destinations the ALTO client
      requests.  Theses information cannot be encoded by the scalar
      types (numerical or ordinal) cost values,
      they cannot carry an array of abstract network elements as a cost.
      A new which the base ALTO protocol
      supports.  A new cost type is required to encode path vectors as costs in
      cost maps.

   o  Encoding
      costs.

   AR-2:  The ALTO protocol SHOULD include the support for encoding
      properties of abstract network elements: Unified
      property map can provide ANEs.

      Only the sequences of ANEs are not enough for most use cases
      mentioned previously.  The properties of endpoints ANEs like "bandwidth" and pids, but it
      cannot convey
      "delay" are required by applications to build the properties of abstract network elements.  A new
      entity domain needs capacity region
      or realize the latency sensitivity.

   AR-3:  The ALTO server SHOULD allow the ALTO client to be registered so that unified property map
      can encode query path
      vectors and the properties of abstract network elements.

   o  Encapsulating multiple map messages in a single session: Making
      multiple queries to get path elements
      consistently.

      Path vectors and the properties of abstract network elements introduce additional communication
      overhead. are
      correlated information, but can be separated into different ALTO
      information resources.  A mechanism to provide multiple map messages in a
      single session query both of them
      consistently is necessary.

   This document proposes the path vector extension which satisfies
   these additional requirements to the ALTO protocol.  Specifically, it
   the ALTO protocol encodes selected abstract network elements in the array of ANEs over an end-to-end path with
   using a new cost type called "path-vector", type, and conveys the properties of
   abstract network elements ANEs using
   unified property map. map [I-D.ietf-alto-unified-props-new].  We also
   provide an optional solution to query separated path vectors and
   properties of ANEs in a consistent way.  But querying general
   separated resources consistently is not the scope in this document.

   The rest of this document is organized as follows.  Section 3 gives
   an example of multi-flow scheduling and illustrates the limitations
   of the base ALTO protocol in such a use case.  Section 4 gives an
   overview of the path vector extension.  Section 5 and introduces a new
   cost type.  Section 6
   define the formal extension. registers a new domain in Domain Registry.
   Section 7 extends Filtered Cost Map and Endpoint Cost Service to
   support the compound resource query.  Section 8 presents several
   examples.  Section 8 9 and Section 9 10 discusses compatibility issues
   with other existing ALTO extensions and design decisions.  Section 10 11
   and Section 11 12 review the security and IANA considerations.

2.  Terminology

   Besides the terms defined in [RFC7285], [RFC8189] [RFC7285] and
   [I-D.ietf-alto-unified-props-new], this document also uses the
   following additional terms: Abstract Network Element, Abstract
   Network Element Name, Abstract Network Element Property, Abstract
   Network Element Property Map, Path Vector and Path-Vector. Vector.

   o  Abstract Network Element (ANE): An abstract network element is an
      abstraction of network components, components; it can be an aggregation of
      links, middle boxes, virtualized network function (VNF), or even a
      sub-network. etc.  An
      abstract network element has two types of attributes: a name and a
      set of properties.

   o  Abstract Network Element Name (ANE Name): An abstract network
      element name  Path Vector: A path vector is an identifier that uniquely identifies array of ANEs.  It presents an
      abstract network element, as defined in Section 5.3.

   o  Abstract Network Element Property (ANE Property): An abstract
      network element property is a network-related property of an
      abstract network element.  It can be "bandwidth" for links and
      "delay" between two switches.

   o  Abstract Network Element Property Map (ANE Property Map): An
      abstract network element property map is a Filtered Property Map
      defined in [I-D.ietf-alto-unified-props-new] which supports the
      "ane" domain in its "domain-types" capability.

   o  Path Vector: A path vector is an array of ALTO Abstract Network
      Elements (ANEs).  It presents an abstract network path between
      entities such path between source/destination points such as
      PIDs or endpoints.  An ANE represents a selected
      part of an end-to-end path that the ALTO Server considers worth
      exposing.

3.  Use Case: Capacity Region for Multi-Flow Scheduling

   Assume that an application has control over a set of flows, some
   flows which may
   go through shared links or switches and share a bottleneck.
   Existing  The
   application hopes to schedule the traffic among multiple flows to get
   better performance.  The capacity region information for those flows
   will benefit the scheduling.  However, existing cost maps can not
   reveal such information.

   Specifically, consider a network as shown in Figure 1.  The network
   has 7 switches (sw1 to sw7) forming a dumb-bell topology.  Switches
   sw1/sw3 provide access on one side, sw2/sw4 provide access on the
   other side, and sw5-sw7 form the backbone.  Endhosts eh1 to eh4 are
   connected to access switches sw1 to sw4 respectively.  Assume that
   the bandwidth of link eh1 -> sw1 and link sw1 -> sw5 are 150 Mbps,
   and the bandwidth of the rest links are 100 Mbps.

                                  +------+
                                  |      |
                                --+ sw6  +--
                              /   |      |  \
        PID1 +-----+         /    +------+   \          +-----+  PID2
        eh1__|     |_       /                 \     ____|     |__eh2
             | sw1 | \   +--|---+         +---|--+ /    | sw2 |
             +-----+  \  |      |         |      |/     +-----+
                       \_| sw5  +---------+ sw7  |
        PID3 +-----+   / |      |         |      |\     +-----+  PID4
        eh3__|     |__/  +------+         +------+ \____|     |__eh4
             | sw3 |                                    | sw4 |
             +-----+                                    +-----+

                      Figure 1: Raw Network Topology.

   The single-node ALTO topology abstraction of the network is shown in
   Figure 2.

                          +----------------------+
                 {eh1}    |                      |     {eh2}
                 PID1     |                      |     PID2
                   +------+                      +------+
                          |                      |
                          |                      |
                 {eh3}    |                      |     {eh4}
                 PID3     |                      |     PID4
                   +------+                      +------+
                          |                      |
                          +----------------------+

             Figure 2: Base Single-Node Topology Abstraction.

   Consider an application overlay (e.g., a large data analysis system)
   which wants to schedule the traffic among a set of end host source-
   destination pairs, say eh1 -> eh2 and eh1 -> eh4.  The application
   can request a cost map providing end-to-end available bandwidth,
   using 'availbw' "availbw" as cost-metric and 'numerical' "numerical" as cost-mode.

   The application will receive from ALTO server that the bandwidth of
   eh1 -> eh2 and eh1 -> eh4 are both 100 Mbps.  But this information is
   not enough.  Consider the following two cases:

   o  Case 1: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw6 ->
      sw7 -> sw2 -> eh2 and eh1 -> eh4 uses path eh1 -> sw1 -> sw5 ->
      sw7 -> sw4 -> eh4, then the application will obtain 150 Mbps. Mbps at
      most.

   o  Case 2: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw7 ->
      sw2 -> eh2 and eh1 -> eh4 uses the path eh1 -> sw1 -> sw5 -> sw7
      -> sw4 -> eh4, then the application will obtain only 100 Mbps. Mbps at
      most.

   To allow applications to distinguish the two aforementioned cases,
   the network needs to provide more details.  In particular:

   o  The network needs to expose more detailed routing information to
      show the shared bottlenecks.

   o  The network needs to provide the necessary abstraction to hide the
      real topology information while providing enough information to
      applications.

   The path-vector path vector extension defined in this document meets all the
   requirements. propose a solution
   to provide these details.

   See [I-D.bernstein-alto-topo] for a more comprehensive survey of use-cases use
   cases where extended network topology information is needed.

4.  Overview of Path Vector Extensions

   This section presents an overview of approaches adopted by the path
   vector extension.  It assumes the readers are familiar with
   (Filtered) Cost Map and Endpoint Cost Service defined in [RFC7285] cost map
   and their extensions endpoint cost service defined in [RFC8189]. [RFC7285].  The path vector
   extension also requires the support of Filtered Property Map defined
   in [I-D.ietf-alto-unified-props-new].

   The path vector extension is composed of three building blocks: (1) a
   new cost type to encode path vectors; (2) a new ALTO entity domain
   for unified property extension [I-D.ietf-alto-unified-props-new] to
   encode properties of abstract network elements; ANEs; and (3) a new service an extension to the cost map and
   endpoint cost resource to provide path vector messages vectors and properties of ANEs
   in a single session; response.

4.1.  New Cost Type to Encode Path Vectors

   Existing cost types defined in [RFC7285] only allow only scalar cost
   values, they cannot be used
   values.  However, the "path vector" abstraction requires to convey
   vector format information.
   This  To achieve this requirement, this
   document defines a new cost mode to enable the cost value to carry an
   array of elements, and a new cost metric to pass ANE take names of ANEs as
   elements in the array.  We call such an array of ANEs a path vector.
   In this way, the cost map and endpoint cost service can convey the
   path vector to represent the routing information.  Detailed
   information and specifications are given in Section 5.1.1 5.1 and
   Section 5.1.2. 5.2.

4.2.  New ALTO Entity Domain to Provide ANE Properties

   Given

   The path vector can only represent the new cost type introduced by Section 4.1, Cost Map route between the source and
   Endpoint Cost Service can provide
   the ANE names along a flow path.
   However, only providing destination.  Although the ANE names without properties application can find the shared ANEs
   among different paths, it is not
   enough.  To detect shared bottlenecks, ALTO clients may expect
   information on specific ANE properties such as link capacity enough for most use cases, which
   requires the bandwidth or
   delay.

   This delay information of the ANEs.  So this
   document adopts the property map defined in
   [I-D.ietf-alto-unified-props-new] to encode provide the general properties
   of
   abstract network elements.  A ANEs.  The document registers a new entity domain called "ane" is registered in the
   property map.  Each entity in to
   represent the "ane" domain has an identifier of
   an ANE.  An  The address of the ANE identifier entity is just the ANE
   name used in the values of by the
   "ane-path" metric defined in path vector.  By requesting the present draft.  ANE properties are
   provided property map of
   entities in information resources called "Property Map Resource" and
   "Filtered Property Map Resource".  The "Filtered Property Map"
   resource which supports the "ane" domain is used to encode domain, the client can retrieve the properties
   of ane entities, and it is called an ANE Property Map ANEs in
   this document. path vectors.

4.3.  New  Extended Cost Map/Endpoint Cost Service to Enable Multipart for Compound Resources

   In

   Providing the base ALTO protocol, ALTO servers use media types in path vector information and the HTTP
   header to indicate ANE properties by
   separated resources have several known benefits: (1) can be better
   compatible with the type of base ALTO protocol; (2) can make different
   property map resources reuse the response.  Typically one response
   only contains a single media type, such as "application/alto-
   costmap+json" same cost map or "application/alto-propmap+json".  This has limited endpoint cost
   resource.  However, it conducts two issues:

   o  Efficiency: The separated resources will require the capability of ALTO servers to return multiple map messages in a
   single response.

   Thus, an ALTO client needs
      to make separate queries invoke multiple requests/responses to get collect all needed
      information.  It increases the
   information communication overhead.

   o  Consistency: The path vectors and properties of related services.  This ANEs are
      correlated.  So querying them one by one may cause a data
   synchronization problem between dependent ALTO services because when
   making conduct consistency
      issue.  Once the second query, path vector changes during the result for client requests
      the first query ANE properties, the ANE properties may have
   already changed.  The same problem can happen to Network Map and Cost
   Map resources.  However, unlike Network Map be inconsistent with
      the previous path vector.

   To solve these issues, this document introduces an extension to cost
   map and Cost Map endpoint cost service, which are
   considered more stable, Path Vectors and allows the dependent ANE Property
   Maps might change more frequently.

   Instead of introducing a new media type ALTO server to encapsulate multiple types
   in attach
   a single response, this document adopts the "multipart/related"
   media type defined property map in [RFC2387].  In this way, a response can contain
   both the path vectors in data entry of a filtered cost map (or or an endpoint cost map)
   and the associated ANE Property Map. The media types of the cost map
   and the property map can still be retrieved from the
   service response.  The
   interpretation of each media type

   These issues may exist in the "multipart/related" response all general cases for querying separated
   ALTO information resources.  But solving this general problem is consistent with not
   in the base ALTO protocol. scope of this document.

5.  Path Vector Extension: Basic Data Types

   This section formally specifies a new cost type and a new entity
   domain.

5.1.  Cost Type

   This document extends the cost types defined in Section 6.1 of
   [RFC7285] by introducing a new cost mode "array" and a new cost
   metric "ane-path".  In the rest content, this document use uses "path-
   vector" to indicate the combination cost type of the cost mode
   "array" and the cost metric "ane-path".

5.1.1.

5.1.  Cost Mode: array

   This document extends the CostMode defined in Section 10.5 of
   [RFC7285] with a new cost mode: "array".  This cost mode indicates
   that every cost value in a cost map represents an array rather than a
   simple value.  The values are arrays of JSONValue.  The specific type
   of each element in the array depends on the cost metric.

5.1.2.

5.2.  Cost Metric: ane-path

   This document specifies a new cost metric: "ane-path".  This cost
   metric indicates that the cost value is a list of abstract network
   elements ANEs which the path
   from a source to a destination goes across.  The values are arrays of
   ANE names which are defined in Section 5.3. 6.2.

   The cost metric "ane-path" SHOULD NOT be used when the cost mode is
   not "array" unless it is explicitly specified by a future extension.
   If an ALTO client send queries with the cost metric "ane-path" and a
   non "array" cost mode, the ALTO server SHOULD return an error with
   the error code "E_INVALID_FIELD_VALUE"; If an ALTO server declares
   the support of a cost type with the cost metric "ane-path" and a non
   "array" cost mode, the ALTO client SHOULD assume such a cost type is
   invalid and ignore it.

5.1.3.

5.3.  Path Vector Cost Type Semantics

   The new cost type follows the convention of the cost types in the
   base ALTO protocol.  Table 1 lists some of the current defined cost
   types and their semantics.

   +------------+--------------+---------------------------------------+
   | Cost Mode  | Cost Metric  | Semantics                             |
   +------------+--------------+---------------------------------------+
   | numerical  | routingcost  | a number representing the routing     |
   |            |              | cost                                  |
   | numerical  | hopcount     | a number representing the hop count   |
   | ordinal    | routingcost  | a ranking representing the routing    |
   |            |              | cost                                  |
   | ordinal    | hopcount     | a ranking representing the hop count  |
   | array      | ane-path     | a list representing the ane path      |
   +------------+--------------+---------------------------------------+

                  Table 1: Cost Types and Their Semantics

   The "routingcost" and "hopcount" can encoded in "numerical" or
   "ordinal", however, the cost metric "ane-path" can only be applied to
   the cost mode "array" defined in this document to convey path vector
   information.  The cost metric "ane-path" can not be used in
   "numerical" or "ordinal" unless it is defined in future extensions.
   If the ALTO server declares that it support cost type with cost
   metric being "ane-path" and cost mode not being "array", the ALTO
   client SHOULD ignore them.

5.2.

6.  ANE Domain

   This document specifies a new ALTO entity domain called "ane" in
   addition to the ones in [I-D.ietf-alto-unified-props-new].

5.2.1.  The ANE
   domain associates property values with the ANEs in a network.  The
   entity in ANE domain is often used in the path vector by cost maps or
   endpoint cost resources.  Accordingly, the ANE domain always depends
   on a cost map or an endpoint cost map.

6.1.  Domain Name

   ane

5.2.2.

6.2.  Domain-Specific Entity Addresses

   The entity address of ane domain is encoded as a JSON string.  The
   string MUST be no more than 64 characters, and it MUST NOT contain
   characters other than US-ASCII alphanumeric characters
   (U+0030-U+0039, U+0041-U+005A, and U+0061-U+007A), the hyphen ("-",
   U+002D), the colon (":", U+003A), the at sign ("@", code point
   U+0040), the low line ("_", U+005F), or the "." separator (U+002E).
   The "." separator is reserved for future use and MUST NOT be used
   unless specifically indicated in this document, or an extension
   document.

5.2.3.

   To simplify the description, we use "ANE name" to indicate the
   address of an entity in ANE domain in this document.

   The ANE name is usually unrelated to the physical device information.
   It is usually generated by the ALTO server on demand and used to
   distinguish from other ANEs in its dependent cost map or endpoint
   cost map.

6.3.  Hierarchy and Inheritance

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

5.3.  Abstract Network Element Name

   An Abstract Network Element Name is encoded as an EntityAddr of the
   "ane" domain as defined in Section 3.4.2 of
   [I-D.ietf-alto-unified-props-new].

6.

7.  Protocol Extensions for Path Vector Extension: Services

   This section Compound Query

   To make the ALTO client query the path vectors and properties of ANEs
   efficiently and consistently, this document extends the Filtered Cost
   Map Service and Endpoint Cost Service.  It also introduce a new service called "Multipart Cost
   Property Service".

6.1.

7.1.  Filtered Cost Map Extensions

   This document extends the Filtered Cost Map Map, as defined in Section 4.1 11.3.2
   of
   [RFC8189].

   The specifications for [RFC7285], by adding new input parameters and capabilities, and by
   augmenting the property map into the data entry of the response.

   The "media type", "HTTP method" method", and "uses" are
   the same as defined specifications (described
   in Section 4.1 Sections 11.3.2.1, 11.3.2.2, and 11.3.2.5 of [RFC8189].

6.1.1. [RFC7285],
   respectively) remain the same.

7.1.1.  Capabilities

   The Filtered Cost Map capabilities are extended with two new members:

   o  dependent-property-map

   o  allow-compound-response

   The capability "dependent-property-map" indicates which property map
   this resource depends on, and the capability "allow-compound-
   response" indicates whether the ALTO server supports the resource to
   compound the property map with its own response data.  With these two
   additional members, the FilteredCostMapCapabilities object in
   Section 11.3.2.4 of [RFC7285] is extended with a new member
   "property-map": as follows:

     object {
       [ResourceID property-map;] dependent-property-map;]
       [JSONBool   allow-compound-response;]
     } PathVectorFilteredCostMapCapabilities PVFCMCapabilities : FilteredCostMapCapabilities

   property-map:  A resource ID defined in the same IRD pointing to an
      ANE Property Map as defined in Section 2. FilteredCostMapCapabilities;

   dependent-property-map:  This field MUST be
      present if specified when the path vector "cost-
      type-names" includes a cost type name indicating a "ane-path"
      metric.  Its value MUST be a resource id indicating a property map
      including "ane" domain.  If not, the ALTO client SHOULD consider
      this resource is present in invalid.

   allow-compound-response:  If present, the "cost-type-
      names" field.

   Other fields of true value means the FilteredCostMapCapabilities object has ALTO
      client can request the same
   format as defined in Section 4.1.1 of [RFC8189] with resource to augment its dependent property
      map into the following
   restriction:

   testable-cost-type-names:  The path vector cost type with "ane-path"
      as response automatically; the false value means the
      ALTO client cannot request the compound response.  If omitted, the
      default value is false;

   To be noticed that the capability "cost-constraints" is unexpected
   for the "array" cost metric mode.  The syntax and "array" as semantics of constraint
   tests on the "array" cost mode MUST NOT depends on the implementation and can
   be
      included defined in the future documents.  But it is not in "testable-cost-type-names".

6.1.2. the scope of
   this document.

7.1.2.  Accept Input Parameters

   The ReqFilteredCostMap uses the same format as defined object in Section 4.1.2 11.3.2.3 of [RFC8189], with the following restrictions:

   constraints, or-constraints: [RFC7285] is
   extended as follows:

     object {
       [PropertyName compound-properties<1..*>;]
     } ReqPVFilteredCostMap : ReqFilteredCostMap;

   compound-properties:  If the path vector cost type capability "allow-compound-response" is
      included in either "cost-type" or "multi-cost-types",
      false, the ALTO clients client MUST NOT use it in "constraints" or "or-constraints".  Otherwise, specify this field, and the ALTO
      server MUST reject the request and return an error with "E_INVALID_FILED_VALUE"
      error code
      "E_INVALID_FIELD_VALUE".

   testable-cost-types:  The path vector cost type MUST NOT be included
      in the "testable-cost-types" when it receives a request including this field.  Otherwise,  If this
      field is specified and accepted, the ALTO server MUST return an error augment the
      dependent property map with error code "E_INVALID_FIELD_VALUE".

6.1.3. the properties in this field into the
      response automatically.

7.1.3.  Response

   If the ALTO client includes specifies the cost type "path-vector" "cost-type" input parameter with
   "ane-path" metric, the "dependent-vtags" field in the "cost-
   type" or "multi-cost-types" "meta" field of
   the response MUST include the version tag of its dependent property
   map following its dependent network map.

   If the ALTO client specifies the "compound-properties" input parameter,
   parameter which is accepted by the ALTO server, the response use MUST
   include a "property-map" field following the "cost-map" field, and
   its value MUST be a PropertyMapData object.  This PropertyMapData
   object MUST be equivalent to the result when query the dependent
   property map resource using the following request: the "entities"
   field includes all the ANE names appearing in the cost values of the
   "cost-map" field, the "properties" field has the same format value as defined the
   "compound-properties" field does.  The properties shown in Section 4.1.3 of
   [RFC8189], the
   "compound-properties" input parameter but are not supported by the corresponding cost value MUST
   dependent property map SHOULD be encoded as a
   JSONArray of AbstractNetworkElementName.

6.2. omitted from the response.

7.2.  Endpoint Cost Service Extensions

   This document extends the Endpoint Cost Service Service, as defined in
   Section 4.2 in [RFC8189]. 11.5.1 of [RFC7285], by adding new input parameters and
   capabilities and by augmenting the property map into the data entry
   of the response.

   The specifications for "HTTP method", "media-type" media type, HTTP method, and "uses" are the
   same as defined in Section 4.2 specifications (described in [RFC8189].

6.2.1.
   Sections 11.5.1.1, 11.5.1.2, and 11.5.1.5 of [RFC7285], respectively)
   are unchanged.

7.2.1.  Capabilities

   The same as defined in extensions to the Endpoint Cost Service capabilities are
   identical to the extensions to the Filtered Cost Map (see
   Section 6.1.1.

6.2.2. 7.1.1).

7.2.2.  Accept Input Parameters

   The ReqEndpointCostMap uses object in Section 11.5.1.3 of [RFC7285] is
   extended as follows:

     object {
       [PropertyName compound-properties<1..*>;]
     } ReqPVEndpointCostMap : ReqEndpointCostMap;

   The "compound-properties" has the same format interpretation as defined in
   Section 4.2.2 of [RFC8189], with 7.1.2

7.2.3.  Response

   If the following restrictions:

   cost-type, multi-cost-types: ALTO clients client specifies the "cost-type" input parameter with
   "ane-path" metric, the response MUST include the path
      vector cost type, e.g.  the one "meta" field with "ane-path" as cost metric and
      "array" as cost mode,
   the "dependent-vtags" in either "cost-type" or "multi-cost-types"
      to activate it, and the path vector extension.

   constraints, or-constraints: "dependent-vtags" field MUST
   include the version tag of its dependent property map.

   If the path vector cost type ALTO client specifies the "compound-properties" input
   parameter which is
      included in either "cost-type" or "multi-cost-types", accepted by the ALTO clients server, the response MUST NOT use it in "constraints" or "or-constraints".  Otherwise,
   include a "property-map" field following the ALTO server "endpoint-cost-map"
   field, and its value MUST return an error with error code
      "E_INVALID_FIELD_VALUE".

   testable-cost-types:  The path vector cost type be a PropertyMapData object.  This
   PropertyMapData object MUST NOT be included
      in equivalent to the "testable-cost-types" field.  Otherwise, result when query
   the ALTO server
      MUST return an error with error code "E_INVALID_FIELD_VALUE".

6.2.3.  Response

   If dependent property map resource using the ALTO client specifies following request: the path vector cost type
   "entities" field includes all the ANE names appearing in the "cost-
   type" or "multi-cost-types" field cost
   values of the input parameter, "endpoint-cost-map" field, the
   response use "properties" field has
   the same format value as defined the "compound-properties" field does.  The
   properties shown in Section 4.2.3 of
   [RFC8189], the "compound-properties" input parameter but are
   not supported by the corresponding cost value MUST dependent property map SHOULD be encoded as a
   JSONArray of AbstractNetworkElementName.

6.3.  Multipart Cost Property Service

   This document introduces a new ALTO service called "Multipart Cost
   Property Service", which provides omitted from
   the response.

8.  Examples

   This section lists some examples of path vector information and the
   associated ANE property information in the same response.

6.3.1.  Media Type

   The media type of the Multipart Cost Property service is "multipart/
   related".

6.3.2.  HTTP Method

   The Multipart Cost Property service is requested using the HTTP POST
   method.

6.3.3.  Accept Input Parameters

   The input parameters of the Multipart Cost Property service MUST be
   encoded as a JSON object in the body of an HTTP POST request.  The
   media type of the request SHOULD be one of "application/alto-
   costmapfilter+json" and "application/alto-endpointcostparams+json".
   The format of the request body depends on the media type:

   o  If the media type of the request is "application/alto-
      costmapfilter+json", the request body MUST be the same type as
      defined by Section 6.1.2.

   o  If the media type of the request is "application/alto-
      endpointcostparams+json", the request body MUST be the same type
      as defined by Section 6.2.2.

   The path vector cost type MUST be the only cost type in the input
   parameter.

6.3.4.  Capabilities

   TBD

6.3.5.  Uses

   The "uses" attribute MUST be an array with at least one resource id.
   The first resource id MUST point to a Filtered Cost Map or an
   Endpoint Cost Service resource.  And the path vector cost type MUST
   be in its "cost-type" capability.  If there are more than one
   resource id in the "uses" attribute, the ALTO client SHOULD ignore
   any additional resource ids.

   According to Section 6.1.1, the "property-map" field MUST be present
   in the first resource.  So the ALTO client MUST infer that the
   Property Map pointed by the "property-map" field of the first
   resource is also a dependent resource.

6.3.6.  Response

   If an ALTO client sends a request of the media type "application/
   alto-costmapfilter+json" and accepts "multipart/related", the HTTP
   body of the response MUST consist of two parts with the media types
   "application/alto-costmap+json" and "application/alto-propmap+json"
   accordingly.  The part with media type "application/alto-
   costmap+json" MUST be the first part.  The content of the
   "application/alto-endpointcost+json" part has the same format as
   defined in Section 6.1.3.

   If an ALTO client sends a request of the media type "application/
   alto-endpointcostparams+json" and accepts "multipart/related", the
   HTTP body of the response MUST consist of two parts with the media
   types "application/alto-endpointcost+json" and "application/alto-
   propmap+json" accordingly.  The part with media type "application/
   alto-endpointcost+json" MUST be the first part.  The content of the
   "application/alto-endpointcost+json" part has the same format as
   defined in Section 6.2.3.

7.  Examples

   This section lists some examples of path vector queries queries and the
   corresponding responses.

7.1.

8.1.  Workflow

   This section gives a typical workflow of how an ALTO client query
   path vectors using the
   path-vector extension.

   1.  Send a GET request for the whole Information Resource Directory.

   2.  Look for the resource of the (Filtered) Cost Map/Endpoint Cost
       Service which contains supports the path vector "ane-path" cost type metric and get the
       resource ID of the dependent abstract network element property map.

   3.  Check whether the capabilities of the property map includes the
       desired "prop-types".

   4.  Send  Check whether the (Filtered) Cost Map/Endpoint Cost Service
       allows the compound response.

       1.  If allowed, the ALTO client can send a path-vector request which accepts "multipart/related"
       media type following "application/alto-costmap+json" or
       "application/endpointcost+json".

7.2. including the
           desired ANE properties to the ALTO server and receive a
           compound response with the cost map/endpoint cost map and the
           property map.

       2.  If not allowed, the ALTO client sends a query for the cost
           map/endpoint cost map first.  After receiving the response,
           the ALTO client interprets all the ANE names appearing in the
           response and sends another query for the property map on
           those ANE names.

8.2.  Information Resource Directory Example

   Here is an example of an Information Resource Directory.  In this
   example, filtered cost map "cost-map-pv" doesn't support the multi-
   cost extension but support the path-vector extension, "endpoint-
   multicost-map" supports both multi-cost extension and path-vector
   extension.  Filtered Property Map "propmap-delay-availbw" "propmap-availbw-delay" supports
   properties "availbw" and "delay", and "propmap-location" supports
   property "location". "delay".

     {
       "meta": {
         "cost-types": {
           "pv":
           "path-vector": {
             "cost-mode": "array",
             "cost-metric": "ane-path"
           },
           "num-routingcost": {
             "cost-mode": "numerical",
             "cost-metric": "routingcost"
           },
           "num-hopcount": {
             "cost-mode": "numerical",
             "cost-metric": "hopcount"
           }
         }

       },
       "resources": {
         "my-default-networkmap": {
           "uri" : "http://alto.example.com/networkmap",
           "media-type" : "application/alto-networkmap+json"
         }
         "cost-map-pv" :
         },
         "my-default-cost-map": {
           "uri": "http://alto.example.com/costmap/pv",
           "media-type": "application/alto-costmap+json",
           "accepts": "application/alto-costmapfilter+json",
           "capabilities": {
             "cost-type-names": [ "pv", "num-hopcount" "num-hopcount",
                                  "num-routingcost" ]
           },
           "property-map": "propmap-delay",
           "uses": [ "my-default-networkmap" ]
         },
         "endpoint-multicost-map" :
         "cost-map-pv": {
           "uri": "http://alto.example.com/costmap/pv",
           "media-type": "application/alto-costmap+json",
           "accepts": "application/alto-costmapfilter+json",
           "capabilities": {
             "cost-type-names": [ "path-vector" ],
             "dependent-property-map": "propmap-availbw-delay"
           },
           "uses": [ "my-default-networkmap" ]
         },
         "endpoint-cost-pv": {
           "uri": "http://alto.exmaple.com/endpointcostmap/multicost", "http://alto.exmaple.com/endpointcost/pv",
           "media-type": "application/alto-endpointcost+json",
           "accepts": "application/alto-endpointcostparams+json",
           "capabilities": {
             "cost-constraints": true,
             "cost-type-names": [ "pv", "num-routingcost" "path-vector" ],
             "max-cost-types": 2
           },
           "property-map": "propmap-availbw"
             "dependent-property-map": "propmap-availbw-delay",
             "allow-compound-response": true
           }
         },
         "propmap-availbw-delay"
         "invalid-cost-map" : {
           "uri": "http://alto.exmaple.com/propmap/availbw", "http://alto.example.com/costmap/invalid",
           "media-type": "application/alto-propmap+json", "application/alto-costmap+json",
           "accepts": "application/alto-propmapparams+json", "application/alto-costmapfilter+json",
           "capabilities": {
             "domain-types":
             "cost-type-names": [ "ane" "path-vector" ],
             "prop-types":
             "allow-compound-response": true
           },
           "uses": [ "availbw" "my-default-networkmap" ]
           }
         },
         "propmap-location" :
         "propmap-availbw-delay": {
           "uri": "http://alto.exmaple.com/propmap/delay", "http://alto.exmaple.com/propmap/ane-prop",
           "media-type": "application/alto-propmap+json",
           "accepts": "application/alto-propmapparams+json",
           "capabilities": {
             "domain-types": [ "pid" "ane" ],
             "prop-types": [ "location" "availbw", "delay" ]
           },
           "uses": [ "cost-map-pv", "endpoint-cost-pv" ]
         }
       }
     }
     }

7.3.

8.3.  Example # 1

   Query filtered cost map to get the path vectors.

   POST /costmap/pv HTTP/1.1
   Host: alto.example.com
   Accept: multipart/related, application/alto-costmap+json,
           application/alto-propmap+json,
           application/alto-error+json
   Content-Length: [TBD]
   Content-Type: application/alto-costmapfilter+json

   {
     "cost-type": {
       "cost-mode": "array",
       "cost-metric": "ane-path"
     },
     "pids": {
       "srcs": [ "PID1" ],
       "dsts": [ "PID2", "PID3" ]
     }
   }
   HTTP/1.1 200 OK
   Content-Length: [TBD]
   Content-Type: multipart/related; boundary=42

   --42
   Content-Type: application/alto-costmap+json

   {
     "meta": {
       "dependent-vtags": [
         {
           "resource-id": "default-network-map", "my-default-networkmap",
           "tag": "75ed013b3cb58f896e839582504f622838ce670f"
         }
       ],
       "cost-type": {
         "cost-mode": "array",
         "cost-metric": "ane-path"
       },
       }
     },
     "cost-map": {
       "PID1": {
         "PID2": [ "ane:L001", "ane:L003" ],
         "PID3": [ "ane:L001", "ane:L004" ]
       }
     }
   }
   --42

   Then query the properties of ANEs in path vectors.

   POST /propmap/ane-prop HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-propmap+json,
           application/alto-error+json
   Content-Length: [TBD]
   Content-Type: application/alto-propmapparams+json

   {
     "entities": [ "ane:L001", "ane:L003", "ane:L004" ],
     "properties": [ "delay" ]
   }
   HTTP/1.1 200 OK
   Content-Length: [TBD]
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {
           "resource-id": "cost-map-pv",
           "tag": "a7d57e120ab63124e3c9a82f7a54bc120fc96216"
         }
       ]
     },
     "property-map": {
       "ane:L001": { "delay": 46},
       "ane:L003": { "delay": 50},
       "ane:L004": { "delay": 70}
     }
   }

8.4.  Example # 2

   POST /endpointcost/pv HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-endpointcost+json,
           application/alto-error+json
   Content-Length: [TBD]
   Content-Type: application/alto-endpointcostparams+json

   {
     "multi-cost-types": [
       {
         "cost-mode": "array",
         "cost-metric": "ane-path"
       },
       {
         "cost-mode": "numerical",
         "cost-metric": "routingcost"
       }
     ],
     "endpoints": {
       "srcs": [ "ipv4:192.0.2.2" ],
       "dsts": [ "ipv4:192.0.2.89",
                 "ipv4:203.0.113.45",
                 "ipv6:2001:db8::10" ]
     }
   }
   HTTP/1.1 200 OK
   Content-Length: [TBD]
   Content-Type: application/alto-endpointcost+json

   {
     "meta": {
       "cost-type": [
         {"cost-mode": "array", "cost-metric": "ane-path"}
       ]
     },
     "endpoint-cost-map": {
       "ipv4:192.0.2.2": {
         "ipv4:192.0.2.89":   [ "ane:L001", "ane:L003",
                                "ane:L004" ],
         "ipv4:203.0.113.45": [ "ane:L001", "ane:L004",
                                "ane:L005" ],
         "ipv6:2001:db8::10": [ "ane:L001", "ane:L005",
                                "ane:L007" ]
       }
     }
   }

   POST /endpointcost/pv HTTP/1.1
   Host: alto.example.com
   Accept: application/alto-endpointcost+json,
           application/alto-error+json
   Content-Length: [TBD]
   Content-Type: application/alto-endpointcostparams+json

   {
     "entities": [ "ane:L001", "ane:L003", "ane:L004",
                   "ane:L005", "ane:L007" ],
     "properties": [ "availbw" ]
   }
   HTTP/1.1 200 OK
   Content-Length: [TBD]
   Content-Type: application/alto-propmap+json

   {
     "meta": {
       "dependent-vtags": [
         {
           "resource-id": "endpoint-cost-pv",
           "tag": "12c0889c3c0892bb67df561ed16d93f5d1fa75cf"
         }
       ]
     },
     "property-map": {
       "ane:L001": { "delay": 46}, "availbw": 50 },
       "ane:L003": { "delay": 50}, "availbw": 48 },
       "ane:L004": { "delay": 70} "availbw": 55 },
       "ane:L005": { "availbw": 60 },
       "ane:L007": { "availbw": 35 }
     }

   --42--

7.4.
   }

8.5.  Example # 2 #3
   POST /endpointcostmap/multicost /endpointcost/pv HTTP/1.1
   Host: alto.example.com
   Accept: multipart/related, application/alto-endpointcost+json,
        application/alto-propmap+json,
           application/alto-error+json
   Content-Length: [TBD]
   Content-Type: application/alto-endpointcostparams+json

   {
     "multi-cost-types": [
       {
         "cost-mode": "array",
         "cost-metric": "ane-path"
       },
       {
         "cost-mode": "numerical",
         "cost-metric": "routingcost"
       }
     ],
     "endpoints": {
       "srcs": [ "ipv4:192.0.2.2" ],
       "dsts": [ "ipv4:192.0.2.89",
                 "ipv4:203.0.113.45",
                 "ipv6:2001:db8::10" ]
  }
     },
     "properties": [ "delay", "availbw" ]
   }
   HTTP/1.1 200 OK
   Content-Length: [TBD]
   Content-Type: multipart/related; boundary=example-2

--example-2
Content-Type: application/alto-endpointcost+json

   {
     "meta": {
    "multi-cost-types":
       "dependent-vtags": [
         {
           "resource-id": "propmap-availbw-delay",
           "tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef"
         }
       ],
       "cost-type": [
         {"cost-mode": "array", "cost-metric": "ane-path"},
      {"cost-mode": "numerical", "cost-metric": "routingcost"} "ane-path"}
       ]
     },
     "endpoint-cost-map": {
       "ipv4:192.0.2.2": {
         "ipv4:192.0.2.89":   [[   [ "ane:L001", "ane:L003",
                                "ane:L004" ], 77],
         "ipv4:203.0.113.45": [[ [ "ane:L001", "ane:L004",
                                "ane:L005" ], 68],
         "ipv6:2001:db8::10": [[ [ "ane:L001", "ane:L005",
                                "ane:L007" ], 98]
    }
  } ]
       }

--example-2
Content-Type: application/alto-propmap+json

{
     },
     "property-map": {
       "ane:L001": { "availbw": 50 50, "delay": 46 },
       "ane:L003": { "availbw": 48 48, "delay": 50 },
       "ane:L004": { "availbw": 55 55, "delay": 70 },
       "ane:L005": { "availbw": 60 60, "delay": 100 },
       "ane:L007": { "availbw": 35 35, "delay": 100 }
     }
   }

--example-2--

8.

9.  Compatibility

8.1.

9.1.  Compatibility with Legacy ALTO Clients/Servers

   The path vector extension on Filtered Cost Map and Endpoint Cost
   Service is backward compatible with the base ALTO protocol. protocol:

   o  If the ALTO server provides path vector extended capabilities "dependent-
      property-map" and "allow-compound-response" for Filtered Cost Map
      or Endpoint Cost Service, but the client is a only supports the base
      ALTO client, protocol, then the client will ignore the path vector cost type those capabilities
      without conducting any incompatibility.

   o  If the client sents sends a request with path vector cost
   type, the input parameter
      "properties", but the server is a only supports the base ALTO server, protocol,
      the server will return an
   "E_INVALID_FIELD_VALUE" error.

8.2. ignore this field.

9.2.  Compatibility with Multi-Cost Extensions

   Cost type path-vector is Extension

   This document does not a testable specify how to integrate the "array" cost type.  Any format of
   constraints SHOULD NOT be applied mode
   and the "ane-path" cost metric with the multi-cost extension
   [RFC8189].  Although there is no reason why somebody has to compound
   the path vectors with other cost type path-vector types in order a single query, there is no
   compatible issue doing it without constraint tests.

   As Section 7.1.1 mentions, the syntax and semantics of whether
   "constraints" or "or-constraints" field for multi-cost to support the path-vector extension.  Specifically, "array" cost mode is
   not specified in this document.  So if an ALTO server provides a
   resource with the "array" cost mode and the capability "cost-
   constraints" or "testable-cost-types-names", the ALTO client MAY
   ignore the capability "cost-constraints" or "testable-cost-types-
   names" unless the implementation or future docuements specify the
   behavior.

9.3.  Compatibility with Incremental Update

   As this document still follows the basic request/response protocol
   with JSON encoding, it is surely compatible with the incremental
   update service as defined by [I-D.ietf-alto-incr-update-sse].  But
   the following details are to be noticed:

   o  Cost type path-vector MUST NOT  When using the compound response, updates on both cost map and
      property map SHOULD be included in "testable-cost-
      types-names" or "testable-cost-types". notified.

   o  When "testable-cost-types-names" not using the compound response, because the cost map is omitted in
      the "capabilities"
      and "testable-cost-types" is omitted "uses" attribute of the property map, once the path vectors in
      the input parameters,
      "constraints" or "or-constraints" SHOULD NOT add any format cost map change, the ALTO server MUST send the updates of
      constraints on the
      cost type path-vector.

8.3.  Compatibility with Incremental Update

   [I-D.ietf-alto-incr-update-sse] defines incremental map before the updates to ALTO
   resources and hence it can be applied to of the path-vector resource
   defined in this document.

9.  Design Decisions and property map.

10.  General Discussions

9.1.

10.1.  Provide More General Calendar Extension

   Cost Calendar for Property Map

   Fetching the historical network information is proposed as a useful for many
   traffic optimization problem.  [I-D.ietf-alto-cost-calendar] already
   proposes an ALTO extension to provide called Cost Calendar which provides the
   historical cost values for using Filtered Cost Map Service and Endpoint Cost
   Service.  Since  However, the calendar for only path vector costs is an extension not enough.

   For example, as the properties of ANEs (e.g., available bandwidth and
   link delay) are usually the real-time network states, they change
   frequently in the real network.  It is very helpful to these services,
   it SHOULD be compatible with Cost Calendar extension.

   However, get the calendar
   historical value of these properties.  Applications may predicate the
   network status using these information to better optimize their
   performance.

   So the coming requirement may be a path-vector (Endpoint) general calendar service for the
   ALTO information resources.

10.2.  Constraint Tests for General Cost Map Types

   The constraint test is
   insufficient for a simple approach to query the application which requires data.  It
   allows users to filter the query result by specifying some boolean
   tests.  This approach is already used in the ALTO protocol.
   [RFC7285] and [RFC8189] allow ALTO clients to specify the
   "constraints" and "or-constraints" tests to better filter the result.

   However, the historical data
   of routing state information.  The (Endpoint) Cost Map current defined syntax is too simple and can only
   provide the changes of be
   used to test the paths.  But scalar cost value.  For more useful information is complex cost types,
   like the
   history of network element properties which are recorded "array" mode defined in this document, it does not work
   well.  It will be helpful to propose more general constraint tests to
   better perform the
   dependent Network Element Property Map.

   Before the Unified Property Map query.

   In practice, it is introduced as an ALTO extension,
   Filtered Cost Map Service and Endpoint Cost Service are the only
   resources which require the calendar supported.  Because other
   resources don't have too complex to be updated frequently.  But Network Element
   Property Map as customize a use case of Unified Property Map will collect the
   real-time information of language for the network.  It SHOULD
   general-purpose boolean tests, and can be updated as soon
   as possible once the metrics of network elements change. a duplicated work.  So it
   may be a good idea to integrate some already defined and widely used
   query languages (or their subset) to solve this problem.  The
   candidates can be XQuery and JSONiq.

10.3.  General Compound Resources Query

   As the requirement last paragraph of Section 4.3 mentions, querying multiple ALTO
   information resources continuously is to provide a general calendar extension which
   not only meets requirement.  And the Filtered Cost Map
   coming issues like inefficiency and Endpoint Cost Service but inconsistency are also applies general.
   There is no standard solving these issues yet.  So we need some
   approach to make the Property Map Service.

10. ALTO client request the compound ALTO
   information resources in a single query.

11.  Security Considerations

10.1.

11.1.  Privacy Concerns

   We can identify multiple potential security issues.  A main security
   issue is network privacy, as the path-vector path vector information may reveal
   more network internal structures than the more abstract single-node
   abstraction.  The network should consider protection mechanisms to
   reduce information exposure, in particular, in settings where the
   network and the application do not belong to the same trust domain.
   On the other hand, in a setting of the same trust domain, a key
   benefit of the path-vector abstraction is reduced information
   transfer from the network to the application.

   The path-vector query may also reveal more information about the
   application.  In particular, the application may reveal all potential
   transfers sites (e.g., where the data source is replicated, and where
   the potential replication sites are).  The application should
   evaluate the potential privacy concerns.

   Beyond the privacy issues, the computation of the path-vector path vector is
   unlikely to be cachable, cacheable, in that the results will depend on the
   particular requests (e.g., where the flows are distributed).  Hence,
   this service may become an entry point for denial of service attacks
   on the availability of an ALTO server.  Hence, authenticity and
   authorization of this ALTO service may need to be better protected.

10.2.

11.2.  Resource Consumption on ALTO Servers

   TODO:

   The Abstract Network Element dependent Property Map of path vectors is dynamically enriched
   when the (Filtered) Cost Map/Endpoint Cost Service is queried of the
   path-vector information.  The properties of the abstract network
   elements can consume a large amount of resources when cached.  So, a
   time-to-live is needed to remove outdated entries in the Abstract
   Network Element Property Map.

11.

12.  IANA Considerations

11.1.

12.1.  ALTO Cost Mode Registry

   This document specifies a new cost mode "array".  However, the base
   ALTO protocol does not have a Cost Mode Registry where new cost mode
   can be registered.  This new cost mode will be registered once the
   registry is defined either in a revised version of [RFC7285] or in
   another future extension.

11.2.

12.2.  ALTO Cost Metric Registry

   A new cost metric needs to be registered in the "ALTO Cost Metric
   Registry", listed in Table 2.

                   +-------------+---------------------+
                   | Identifier  | Intended Semantics  |
                   +-------------+---------------------+
                   | ane-path    | See Section 5.1.2 5.2     |
                   +-------------+---------------------+

                        Table 2: ALTO Cost Metrics

11.3.

12.3.  ALTO Entity Domain Registry

   As proposed in Section 9.2 of [I-D.ietf-alto-unified-props-new],
   "ALTO Entity Domain Registry" is requested.  Besides, a new domain is to be
   registered, listed in Table 3.

   +-------------+--------------------------+--------------------------+
   | Identifier  | Entity Address Encoding  | Hierarchy & Inheritance  |
   +-------------+--------------------------+--------------------------+
   | ane         | See Section 5.2.2 6.2          | None                     |
   +-------------+--------------------------+--------------------------+

                           Table 3: ALTO Entity Domain

11.4.

12.4.  ALTO Network Element Property Type Registry

   The "ALTO Abstract Network Element Property Type Registry" is
   required by the ALTO Entity Domain "ane", listed in Table 4.

                +-------------+--------------------------+
                | Identifier  | Intended Semantics       |
                +-------------+--------------------------+
                | availbw     | The available bandwidth  |
                | delay       | The transmission delay   |
                +-------------+--------------------------+

           Table 4: ALTO Abstract Network Element Property Types

12.

13.  Acknowledgments

   The authors would like to thank discussions with Randriamasy Sabine,
   Andreas Voellmy, Erran Li, Haibin Son, Haizhou Du, Jiayuan Hu, Qiao
   Xiang, Tianyuan Liu, Xiao Shi, Xin Wang, and Yan Luo.

13.

14.  References

13.1.

14.1.  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>.

13.2.
              <https://www.rfc-editor.org/info/rfc2119>.

14.2.  Informative References

   [I-D.amante-i2rs-topology-use-cases]
              Medved, J., Previdi, S., Lopez, V., and S. Amante,
              "Topology API Use Cases", draft-amante-i2rs-topology-use-
              cases-01 (work in progress), October 2013.

   [I-D.bernstein-alto-topo]
              Bernstein, G., Yang, Y., and Y. Lee, "ALTO Topology
              Service: Uses Cases, Requirements, and Framework", draft-
              bernstein-alto-topo-00 (work in progress), October 2013.

   [I-D.ietf-alto-cost-calendar]
              Randriamasy, S., Yang, Y., Wu, Q., Lingli, D., and N.
              Schwan, "ALTO Cost Calendar", draft-ietf-alto-cost-
              calendar-01 (work in progress), February 2017.

   [I-D.ietf-alto-incr-update-sse]
              Roome, W. and Y. Yang, "ALTO Incremental Updates Using
              Server-Sent Events (SSE)", draft-ietf-alto-incr-update-
              sse-08 (work in progress), January 2018.

   [I-D.ietf-alto-unified-props-new]
              Roome, W., Chen, S., xinwang2014@hotmail.com, x., Yang,
              Y., and J. Zhang, "Extensible Property Maps for the ALTO
              Protocol", draft-ietf-alto-unified-props-new-01 (work in
              progress), December 2017.

   [I-D.lee-alto-app-net-info-exchange]
              Lee, Y., Dhody, D., Wu, Q., Bernstein, G., and T. Choi,
              "ALTO Extensions to Support Application and Network
              Resource Information Exchange for High Bandwidth
              Applications in TE networks", draft-lee-alto-app-net-info-
              exchange-04 (work in progress), October 2013.

   [I-D.yang-alto-topology]
              Bernstein, G., Lee, Y., Roome, W., Scharf, M., and Y.
              Yang, "ALTO Topology Extensions: Node-Link Graphs", draft-
              yang-alto-topology-06 (work in progress), March 2015.

   [RFC2387]  Levinson, E., "The MIME Multipart/Related Content-type",
              RFC 2387, DOI 10.17487/RFC2387, August 1998,
              <https://www.rfc-editor.org/info/rfc2387>.

   [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>.

   [RFC8189]  Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost
              Application-Layer Traffic Optimization (ALTO)", RFC 8189,
              DOI 10.17487/RFC8189, October 2017, <https://www.rfc-
              editor.org/info/rfc8189>.
              <https://www.rfc-editor.org/info/rfc8189>.

Authors' Addresses

   Greg Bernstein
   Grotto Networking
   Fremont, CA
   USA

   Email: gregb@grotto-networking.com
   Shiwei Dawn Chen
   Tongji University
   4800 Caoan Road
   Shanghai  201804
   China

   Email: dawn_chen_f@hotmail.com

   Kai Gao
   Tsinghua University
   Beijing  Beijing
   China

   Email: gaok12@mails.tsinghua.edu.cn

   Young Lee
   Huawei
   TX
   USA

   Email: leeyoung@huawei.com

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

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

   Michael Scharf
   Nokia
   Germany

   Email: michael.scharf@nokia.com
   Y. Richard Yang
   Yale University
   51 Prospect St
   New Haven  CT
   USA

   Email: yry@cs.yale.edu

   Jingxuan Jensen Zhang
   Tongji University
   4800 Caoan Road
   Shanghai  201804
   China

   Email: jingxuan.n.zhang@gmail.com