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Versions: (draft-yang-alto-path-vector) 00 01 02 03 04 05 06 07 08

ALTO WG                                                     G. Bernstein
Internet-Draft                                         Grotto Networking
Intended status: Standards Track                                 S. Chen
Expires: November 4, 2017                              Tongji University
                                                                  K. Gao
                                                     Tsinghua University
                                                                  Y. Lee
                                                                  Huawei
                                                                W. Roome
                                                               M. Scharf
                                                                   Nokia
                                                                 Y. Yang
                                                         Yale University
                                                                J. Zhang
                                                       Tongji University
                                                             May 3, 2017


                 ALTO Extension: Path Vector Cost Mode
                   draft-ietf-alto-path-vector-00.txt

Abstract

   The Application-Layer Traffic Optimization (ALTO) Service has defined
   network and cost maps to provide basic network information, where the
   cost maps allow only scalar (numerical or ordinal) cost mode values.
   This document introduces a new cost mode called path-vector to allow
   ALTO clients to support use cases such as capacity regions for
   applications.  This document starts with a non-normative example
   called multi-flow scheduling (or capacity region) to illustrate that
   ALTO cost maps without path vectors cannot provide sufficient
   information.  This document then defines path-vector as a new cost
   mode.

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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   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 November 4, 2017.

Copyright Notice

   Copyright (c) 2017 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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Use Case: Capacity Region for Multi-Flow Scheduling . . . . .   5
   4.  Overview of Approach  . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Path Vector Data Format . . . . . . . . . . . . . . . . .   7
     4.2.  Network Element Property Map  . . . . . . . . . . . . . .   8
     4.3.  Flow Query Format . . . . . . . . . . . . . . . . . . . .   8
     4.4.  Query Specific  . . . . . . . . . . . . . . . . . . . . .   8
   5.  Protocol Extensions . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Cost Type . . . . . . . . . . . . . . . . . . . . . . . .   9
       5.1.1.  Cost Metric . . . . . . . . . . . . . . . . . . . . .   9
       5.1.2.  Cost Mode: Path Vector  . . . . . . . . . . . . . . .   9
     5.2.  Version Tag . . . . . . . . . . . . . . . . . . . . . . .   9
     5.3.  Network Element Name  . . . . . . . . . . . . . . . . . .  10
     5.4.  ANE Domain  . . . . . . . . . . . . . . . . . . . . . . .  10
       5.4.1.  Domain Name . . . . . . . . . . . . . . . . . . . . .  10
       5.4.2.  Domain-Specific Entity Addresses  . . . . . . . . . .  10
     5.5.  Filtered Network Element Property Map . . . . . . . . . .  10
       5.5.1.  Accept Input Parameters . . . . . . . . . . . . . . .  10
       5.5.2.  Capabilities  . . . . . . . . . . . . . . . . . . . .  11
       5.5.3.  Response  . . . . . . . . . . . . . . . . . . . . . .  11



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     5.6.  IRD Extensions  . . . . . . . . . . . . . . . . . . . . .  11
     5.7.  Cost Map Extensions . . . . . . . . . . . . . . . . . . .  12
       5.7.1.  Propertymap . . . . . . . . . . . . . . . . . . . . .  12
       5.7.2.  Response  . . . . . . . . . . . . . . . . . . . . . .  12
     5.8.  Filtered Cost Map Extensions  . . . . . . . . . . . . . .  12
       5.8.1.  Capabilities  . . . . . . . . . . . . . . . . . . . .  12
       5.8.2.  Accept Input Parameters . . . . . . . . . . . . . . .  13
       5.8.3.  Propertymap . . . . . . . . . . . . . . . . . . . . .  14
       5.8.4.  Response  . . . . . . . . . . . . . . . . . . . . . .  14
     5.9.  Endpoint Cost Service Extensions  . . . . . . . . . . . .  14
       5.9.1.  Capabilities  . . . . . . . . . . . . . . . . . . . .  15
       5.9.2.  Accept Input Parameters . . . . . . . . . . . . . . .  15
       5.9.3.  Propertymap . . . . . . . . . . . . . . . . . . . . .  16
       5.9.4.  Response  . . . . . . . . . . . . . . . . . . . . . .  16
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.1.  Workflow  . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.2.  Information Resource Directory Example  . . . . . . . . .  17
     6.3.  Cost Map Example  . . . . . . . . . . . . . . . . . . . .  19
     6.4.  Multi-Cost Filtered Cost Map Example  . . . . . . . . . .  20
     6.5.  Endpoint Cost Service Example . . . . . . . . . . . . . .  22
     6.6.  Network Element Property Map Example # 1  . . . . . . . .  23
     6.7.  Network Element Property Map Example # 2  . . . . . . . .  24
   7.  Compatibility . . . . . . . . . . . . . . . . . . . . . . . .  25
     7.1.  Compatibility with Legacy ALTO Clients/Servers  . . . . .  25
     7.2.  Compatibility with Multi-Cost Extensions  . . . . . . . .  25
     7.3.  Compatibility with Incremental Update . . . . . . . . . .  26
   8.  Time to live  . . . . . . . . . . . . . . . . . . . . . . . .  26
   9.  Design Decisions and Discussions  . . . . . . . . . . . . . .  26
     9.1.  Path Vector or Path Graph . . . . . . . . . . . . . . . .  26
     9.2.  Provide More General Calendar Extension . . . . . . . . .  27
     9.3.  Snapshot and real-time update . . . . . . . . . . . . . .  27
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  27
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  28
     11.1.  ALTO Cost Mode Registry  . . . . . . . . . . . . . . . .  28
     11.2.  ALTO Cost Metric Registry  . . . . . . . . . . . . . . .  28
     11.3.  ALTO Entity Domain Registry  . . . . . . . . . . . . . .  28
     11.4.  ALTO Network Element Property Type Registry  . . . . . .  29
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  29
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  29
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  29
     13.2.  Informative References . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31

1.  Introduction

   The ALTO base protocol [RFC7285] is designed for exposing network
   information through services such as the Network Map service and the
   Cost Map service.  These services use the extreme "single-node"



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   abstraction, which represents the whole network with a single node
   and hosts are connected to the node's access ports.

   Although the "single-node" abstraction works well for many settings,
   new use cases, such as inter-datacenter data transfers and scientific
   high-performance computing data transfers, require additional network
   information beyond the single-node abstraction, to support
   application capabilities, in particular, the ability of application
   flow scheduling.

   Specifically, providing network information to support application
   flow scheduling introduces multiple complexities.  First, the
   underlying assumption of existing ALTO services is single-commodity
   flows.  Hence, given the flow from a source to a destination, ALTO
   computes the network metrics of the flow and returns them to the
   application.  The metric values for different flows are independent.
   Application flow scheduling, however, requires network information to
   compute application-desirable multi-commodity flows, where multiple
   flows under the control of the same application may share common
   network bottlenecks.  This requirement is beyond the capability of
   the single-node abstraction adopted by the base ALTO protocol.
   Second, some flow scheduling problems may consider end-to-end metrics
   at the same time and thus require multiple costs to be updated
   simultaneously.  Such a requirement, even though already addressed by
   [I-D.ietf-alto-multi-cost], still needs to be handled very carefully.

   To address these complexities in supporting the new flow scheduling
   use case, this document specifies a path-vector extension to the base
   ALTO protocol.  This extension introduces a new cost type, which uses
   "path-vector" as cost mode and "ane" (abstract network element) as
   cost metric.  It extends "Filtered Property Map" defined in
   [I-D.roome-alto-unified-props] to address the issue of scalability
   and consistency in providing path vectors with fine-grained
   information.  This document also registers a new entity domain,
   entity specification and properties in the ALTO Entity Domain
   Registry.  Besides, (Filtered) Cost Map and Endpoint Cost Service are
   extended to support path-vector and flow query format.  The concept
   of "query specific" is put forward to correlate the response
   information of (Filtered) Cost Map/Endpoint Cost service and query of
   property map.

   The document is organized as follows.  Section 3 gives an example of
   flow scheduling to illustrate the need to introduce cost mode "path-
   vector" and cost metric "ane".  Section 4 gives an overview of the
   path-vector extension.  Section 5 specifies the new cost mode and
   cost metric, new domain type, entity properties and protocol
   extensions for (Filtered) Cost Maps and Endpoint Cost Services.
   Section 6 presents several examples.  Section 7 discusses the



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   compatibility issues with some other proposed ALTO extensions.
   Section 8 discusses the time to live problem.  Section 9 discusses
   several design decisions.  Section 10 and Section 11 discusses about
   security and IANA Considerations.

2.  Terminology

   This document uses the following terms: Network Element, Network
   Element Name, Network Element Property, Network Element Property Map
   and Path Vector.

   o  Network Element (NE): A Network Element is an abstract network
      element, which can be a link, a network switching device, or a set
      of devices.

   o  Network Element Name (NEN): The id of a NE.  It can be referenced
      by Cost Map, Filtered Cost Map, Endpoint Cost Service and Property
      Map.

   o  Network Element Property (NEP): The property of a NE.  It can be
      the available bandwidth of a link, the delay or other available
      properties.

   o  Network Element Property Map (NEP Map): It is a Filtered Property
      Map resource defined in [I-D.roome-alto-unified-props] and
      supports "ane" domain in its "domain-types" capability.

   o  Cost Map, Filtered Cost Map, Endpoint Cost Service: If not
      explained explicitly, they are the same definition as of
      [I-D.ietf-alto-multi-cost] by default.

   o  Path Vector (PV): An array of NENs.  It can be used to convey the
      routing information.

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

   Consider the case that routing is given.  Then what application-layer
   traffic optimization will focus on is traffic scheduling among
   application-layer paths.  Specifically, assume that an application
   has control over a set of flows F = {f_1, f_2, ..., f_|F|}. If
   routing is given, what the application can control is x_1, x_2, ...,
   x_|F|, where x_i is the amount of traffic for flow i.  Let x = [x_1,
   ..., x_|F|] be the vector of the flow traffic amounts.  Due to shared
   links, feasible values of x where link capacities are not exceeded
   can be a complex polytype.

   Specifically, consider a network as shown in Figure 1.  The network
   has 7 switches (sw1 to sw7) forming a dumb-bell topology.  Switches



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   sw1/sw3 provide access on one side, sw2/sw4 provide access on the
   other side, and sw5-sw7 form the backbone.  End hosts eh1 to eh4 are
   connected to access switches sw1 to sw4 respectively.  Assume that
   the bandwidth of each link is 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 needs to schedule the traffic among a set of end host source-
   destination pairs, say eh1 -> eh2, and eh3 -> eh4.  The application
   can request a cost map providing end-to-end available bandwidth,
   using 'availbw' as cost-metric and 'numerical' as cost-mode.

   Assume that the application receives from the ALTO server that the
   bandwidth of eh1 -> eh2 and eh3 ->eh4 are both 100 Mbps.  It cannot
   determine that if it schedules the two flows together, whether it
   will obtain a total of 100 Mbps or 200 Mbps.  This depends on whether



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   the routing paths of the two flows share a bottleneck in the
   underlying topology:

   o  Case 1: If eh1 -> eh2 and eh3 -> eh4 use different paths, for
      example, when the first uses sw1 -> sw5 -> sw7 -> sw2, and the
      second uses sw3 -> sw5 -> sw6 -> sw7 -> sw4.  Then the application
      will obtain 200 Mbps.

   o  Case 2: If eh1 -> eh2 and eh3 -> eh4 share a bottleneck, for
      example, when both use the direct link sw5 -> sw7, then the
      application will obtain only 100 Mbps.

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

   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 as possible.

   The path-vector extension defined in this document will satisfy all
   the requirements.

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

4.  Overview of Approach

   This section presents a non-normative overview of the path-vector
   extension defined in this document.  It assumes the readers are
   familiar with (Filtered) Cost Map and Endpoint Cost Service defined
   in [RFC7285], their extensions defined in [I-D.ietf-alto-multi-cost]
   and Filtered Property Map defined in [I-D.roome-alto-unified-props].

4.1.  Path Vector Data Format

   The path-vector extension defined in this document introduces "path-
   vector" as a cost mode, where a path vector between two entities
   (either PIDs or endpoints) is an array of abstract network elements.
   Each abstract network element is represented by a name.  An abstract
   network element can be a link, a network switching device, or a set
   of devices.

   One issue of introducing path vectors is how to encode them.  The
   cost entries contained in an ALTO (Filtered) Cost Map or Endpoint
   Cost Service are formally defined in Section 11.2.3.6 of [RFC7285] to



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   be any type of JSON value.  But the section also suggests that
   implementations may assume the cost values are numbers unless
   specifically defined by an extension.  This document extends the
   definition of Cost Map and Endpoint Cost Map to allow the returned
   cost to be a path vector, which is a JSONArray of Network Element
   Names.

4.2.  Network Element Property Map

   The response with only the names of network elements does not provide
   enough information.  To be useful to applications, the extension need
   to provide desired properties of the abstract network elements as
   well.  This document registers a new entity domain "ane" and entity
   specifications.  The Filtered Property Map defined in
   [I-D.roome-alto-unified-props] supporting "ane" domain (named Network
   Element Property Map) is used for ALTO clients to retrieve the
   properties of abstract network elements.

4.3.  Flow Query Format

   Current queries of the (Filtered) Cost Map/Endpoint Cost Service are
   of cross-product format.  Such format fails to support lists of
   single src to single dst costs.  So the input scheme of the Filtered
   Cost Map and Endpoint Cost Service is extended to support the above
   flow query format.

4.4.  Query Specific

   Path Vector extension has raised a new occasion that different
   resources can be associated with the same query.  Here, the cost path
   vector of the (Filtered) Cost Map/Endpoint Cost Service and the
   properties of the abstract network elements of the Network Element
   Property Map are generated at the same time and they are related.
   So, a query-specific attribute "query-id" is introduced in the "vtag"
   to express such information.  Also, the input parameters of the
   Network Element Property Map is extended to support the query-
   specific queries.

5.  Protocol Extensions

   This section formally specifies the path-vector extension which
   includes the following components: a new cost type, a new entity
   domain, extensions of (Filtered) Cost Map and Endpoint Cost Map.
   Below we specify each component in details.







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5.1.  Cost Type

   The path-vector extension defined in this document enriches the cost
   types defined in Section 6.1 of [RFC7285].

5.1.1.  Cost Metric

   This document specifies a new cost metric: "ane".  It is of type
   CostMetric as defined in Section 10.6 of [RFC7285].  The cost metric
   "ane" MUST NOT be used when the cost mode is not "path-vector" unless
   it is explicitly specified in a future extension.  Meanwhile, an ALTO
   server with path-vector extension MUST support the cost metric "ane".

   Cost metric "ane":  This cost metric MUST be encoded as the
      JSONString "ane".  When cost metric is "ane", Network Element
      Names contained in the path vectors MUST be query-specific.

5.1.2.  Cost Mode: Path Vector

   This document specifies a new cost mode: "path-vector".  The path-
   vector cost mode is of type CostMode as defined in Section 6.1.2 of
   [RFC7285] and is encoded as the JSONString "path-vector".

   A (Filtered) Cost Map resource or Endpoint Cost Service, when queried
   with this cost mode, MUST return a CostMapData or EndpointCostMapData
   whose cost value is a JSONArray of type NetworkElementName as
   specified in Section 5.3.

   This cost mode MUST be used with the cost metric "ane" unless it is
   explicitly specified by a future extension.

5.2.  Version Tag

   To support the concept of query specific, a new field named "query-
   id" is introduced to correlate the query information between the
   (Filtered) Cost Map/Endpoint Cost Service response and the
   corresponding property map query.  The object VersionTag as defined
   in Section 10.3 of [RFC7285] is extended as follows:

     object {
       ResourceID   resource-id;
       JSONString   tag;
       [JSONString  query-id;]
     } VersionTag;

   resource-id, tag:  As defined in Section 10.3 of [RFC7285].





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   query-id:  A string used to uniquely identify the abstract network
      elements in the property map.

5.3.  Network Element Name

   This document also extends [RFC7285] with a new basic data type:
   NetworkElementName.  A NetworkElementName is of type EntityAddr as
   defined in Section 2.3 of [I-D.roome-alto-unified-props] and is
   encoded as a JSONString.  A NetworkElementName MUST be an EntityAddr
   of the ANE domain (Section 5.4).

5.4.  ANE Domain

   This document specifies a new domain in addition to the ones in
   [I-D.roome-alto-unified-props].

5.4.1.  Domain Name

   ane

5.4.2.  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.

5.5.  Filtered Network Element Property Map

   A Filtered Network Element Property Map MUST be a Filtered Property
   Map as defined in Section 5 of [I-D.roome-alto-unified-props].

5.5.1.  Accept Input Parameters

   This document extends ReqFilteredPropertyMap defined in Section 5.3
   of [I-D.roome-alto-unified-props] by introducing an optional field
   named "query-id".  The ReqFilteredPropertyMap is extended as follows:

     object {
       EntityAddr     entities<1..*>
       PropertyName   properties<1..*>;
       [JSONString    query-id;]
     } ReqFilteredPropertyMap;



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   entities, properties:  The same as defined in Section 5.3 of
      [I-D.roome-alto-unified-props].

   query-id:  Like the "query-id" defined in Section 5.2, the "query-id"
      here is also a string used to uniquely identify the abstract
      network elements in the property map.

5.5.2.  Capabilities

   A Network Element Property Map MUST have capabilities "domain-types"
   and "prop-types" as defined in Section 4.4 of
   [I-D.roome-alto-unified-props].  The "domain-types" capability MUST
   contain domain "ane".  And the "prop-types" capability MUST be a
   subset of property types which are registered with the "ALTO Network
   Element Property Type Registry" defined in Section 11.4 of this
   document.

5.5.3.  Response

   The response is the same as for the Property Map, as defined in
   Section 4.6 of [I-D.roome-alto-unified-props], except that only the
   requested entities and properties are returned for Filtered Network
   Element Map. Examples can be found in Section 6.6 and Section 6.7.

5.6.  IRD Extensions

   This document extends IRDResourceEntry defined in Section 9.2.2 of
   [RFC7285] by introducing a new entry named "propertymap".  The
   IRDResourceEntry object is extended as follows:

     object {
       JSONString uri;
       JSONString media-type;
       [JSONString accepts;]
       [Capabilities capabilities;]
       [ResourceID uses<0..*>;]
       [ResourceID propertymap<0..*>;]
     } IRDResourceEntry;

   uri, media-type, accepts, capabilities, uses:  The same as defined in
      Section 9.2.2 of [RFC7285].

   propertymap:  A list of resource IDs, defined in the same IRD, that
      indicates where the specific properties of the returned abstract
      network elements can be retrieved.






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5.7.  Cost Map Extensions

   This document extends Cost Map defined in Section 11.2.3 of [RFC7285]
   by returning JSONArray instead of JSONNumber as the cost value,
   including "vtag" in "meta" field in the response, and adding a new
   field referencing to the Network Element Property Map.

   The media type, HTTP method, capabilities, accept input parameter and
   uses specifications are unchanged.

5.7.1.  Propertymap

   If the Cost Map supports the path-vector extension, the field
   "propertymap" provides a list of resource ids of Network Element
   Property Map. Each network element property map resource provides
   properties for the dynamically generated abstract network elements.

5.7.2.  Response

   The response is the same as defined in Section 11.2.3.6 of [RFC7285]
   except the follows:

   o  If the cost mode is "path-vector", the cost is a JSONArray of
      Network Element Names.

   o  If the query sent by the client includes cost type path vector,
      the "vtag" filed defined in Section 5.2 has to be included in the
      response.  And the "query-id" information in "vtag" MUST be
      provided to clients.

5.8.  Filtered Cost Map Extensions

   This document extends the Filtered Cost Map defined in Section 4.1 of
   [I-D.ietf-alto-multi-cost] by specifying details on capabilities,
   returning JSONArray instead of JSONNumber as the cost value,
   including "vtag" in "meta" field in the response, and adding a new
   field referencing to the Network Element Property Map.

   The media type, HTTP method and uses specifications are unchanged.

5.8.1.  Capabilities

   The FilteredCostMapCapabilities object is the same as defined in
   Section 4.1.1 of [I-D.ietf-alto-multi-cost] expect the follow:

   testable-cost-type-names:  Cost type "path-vector" MUST NOT appear in
      the "testable-cost-type-names" field.




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5.8.2.  Accept Input Parameters

   The ReqFilteredCostMap defined in Section 4.1.2 of
   [I-D.ietf-alto-multi-cost] is extended, the meanings and the
   constraints of some fields are also extended.

     object {
       [CostType cost-type;]
       [CostType multi-cost-types<1..*>;]
       [CostType testable-cost-types<1..*>;]
       [JSONString constraints<0..*>;]
       [JSONString or-constraints<1..*><1..*>;]
       [PIDFilter pids;]
       [PIDFlowFilter pid-flows<1..*>;]
     } ReqFilteredCostMap;

     object {
       PIDName src;
       PIDName dst;
     } PIDFlowFilter;

   cost-type:  If the cost type is path-vector and neither the
      "testable-cost-type-names" field is provided by the server nor the
      "testable-cost-types" field is provided by the client, the
      "constraints" field and the "or-constraints" field SHOULD NOT
      appear.  If not, the ALTO server MUST return an error with error
      code E_INVALID_FIELD_VALUE.  The server MAY include an optional
      field named "field" in the "meta" field of the response, the value
      of "field" is "constraints" or "or-constraints".  The server MAY
      also include an optional field named "value" in the "meta" field,
      the value of "value" is "path-vector".  If the "value" field is
      specified, the "field" field MUST be specified.

   multi-cost-types:  If "multi-cost-types" includes cost type path-
      vector, meanwhile, neither the "testable-cost-type-names" field is
      provided by the server nor the "testable-cost-types" field is
      provided by the client, the cost type index of path-vector MUST
      NOT appear in the "constraints" field or the "or-constraints"
      field.  If not, the ALTO server MUST return an error with error
      code E_INVALID_FIELD_VALUE.  The server MAY include an optional
      field named "field" in the "meta" field of the response, the value
      of "field" is "constraints" or "or-constraints".  The server MAY
      also include an optional field named "value" in the "meta" field,
      the value of "value" is "path-vector".  If the "value" field is
      specified, the "field" field MUST be specified.

   testable-cost-types:  "testable-cost-types" SHOULD NOT include path-
      vector cost type.  If "testable-cost-types" contains path-vector



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      cost type, the ALTO server MUST return an error with error code
      E_INVALID_FIELD_VALUE.  The server MAY include an optional field
      named "field" in the "meta" field of the response, the value of
      "filed" is "testable-cost-types/cost-mode".  The server MAY also
      include an optional field named "value" in the "meta" field, the
      value of "value" is "path-vector".  If the "value" field is
      specified, the "field" field MUST be specified.

   pid-flows:  A list of PID src to PID dst for which path costs are to
      be returned.

   Additional requirement is that the Client MUST specify either "pids"
   or "pid-flows", but MUST NOT specify both.

5.8.3.  Propertymap

   If the Filtered Cost Map supports the path-vector extension, the
   field "propertymap" provides a list of resource ids of Network
   Element Property Map. Each network element property map resource
   provides properties for the dynamically generated abstract network
   elements.

5.8.4.  Response

   The response is the same as defined in Section 4.1.3 of
   [I-D.ietf-alto-multi-cost] except the follows:

   o  Whether the "cost-type" field or the "multi-cost-types" field
      includes cost type path-vector, the cost is a JSONArray of Network
      Element Names.

   o  If the query sent by the client includes cost type path vector,
      the "vtag" filed defined in Section 5.2 has to be included in the
      response.  And the "query-id" information in "vtag" MUST be
      provided to clients.

5.9.  Endpoint Cost Service Extensions

   This document extends the Endpoint Cost Service defined in
   Section 4.2 in [I-D.ietf-alto-multi-cost] by specifying details on
   capabilities, returning JSONArray instead of JSONNumber as the cost
   value, including "vtag" in "meta" field in the response, and adding a
   new field referencing to the Network Element Property Map.

   The media type, HTTP method and uses specifications are unchanged.






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5.9.1.  Capabilities

   The same as defined in Section 5.8.1.

5.9.2.  Accept Input Parameters

   The ReqFilteredCostMap defined in Section 4.1.2 of
   [I-D.ietf-alto-multi-cost] is extended, the meanings and the
   constraints of some fields are also extended.

   ``` object { [CostType cost-type;][CostType multi-cost-types<1..*>;]
   [CostType testable-cost-types<1..*>;][JSONString constraints<0..*>;]
   [JSONString or-constraints<1.._><1.._>;][EndpointFilter endpoints;]
   [EndpointFlowFilter endpoint-flows<1..*>;] } ReqEndpointCostMap;

   object { TypedEndpointAddr src; TypedEndpointAddr dst; }
   EndpointFlowFilter; ```

   cost-type:  If the cost type is path-vector and neither the
      "testable-cost-type-names" field is provided by the server nor the
      "testable-cost-types" field is provided by the client, the
      "constraints" field and the "or-constraints" field SHOULD NOT
      appear.  If not, the ALTO server MUST return an error with error
      code E_INVALID_FIELD_VALUE.  The server MAY include an optional
      field named "field" in the "meta" field of the response, the value
      of "field" is "constraints" or "or-constraints".  The server MAY
      also include an optional field named "value" in the "meta" field,
      the value of "value" is "path-vector".  If the "value" field is
      specified, the "field" field MUST be specified.

   multi-cost-types:  If "multi-cost-types" includes cost type path-
      vector, meanwhile, neither the "testable-cost-type-names" field is
      provided by the server nor the "testable-cost-types" field is
      provided by the client, the cost type index of path-vector MUST
      NOT appear in the "constraints" field or the "or-constraints"
      field.  If not, the ALTO server MUST return an error with error
      code E_INVALID_FIELD_VALUE.  The server MAY include an optional
      field named "field" in the "meta" field of the response, the value
      of "field" is "constraints" or "or-constraints".  The server MAY
      also include an optional field named "value" in the "meta" field,
      the value of "value" is "path-vector".  If the "value" field is
      specified, the "field" field MUST be specified.

   testable-cost-types:  "testable-cost-types" SHOULD NOT include path-
      vector cost type.  If "testable-cost-types" contains path-vector
      cost type, the ALTO server MUST return an error with error code
      E_INVALID_FIELD_VALUE.  The server MAY include an optional field
      named "field" in the "meta" field of the response, the value of



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      "filed" is "testable-cost-types/cost-mode".  The server MAY also
      include an optional field named "value" in the "meta" field, the
      value of "value" is "path-vector".  If the "value" field is
      specified, the "field" field MUST be specified.

   endpoint-flows:  A list of endpoint src to endpoint dst for which
      path costs are to be returned.

   Additional requirement is that the Client MUST specify either
   "endpoints" or "endpoint-flows", but MUST NOT specify both.

5.9.3.  Propertymap

   If the Endpoint Cost Service supports the path-vector extension, the
   field "propertymap" provides a list of resource ids of Network
   Element Property Map. Each network element property map resource
   provides properties for the dynamically generated abstract network
   elements.

5.9.4.  Response

   The response is the same as defined in Section 4.2.3 of
   [I-D.ietf-alto-multi-cost] except the follows:

   o  Whether the "cost-type" field or the "multi-cost-types" field
      includes cost type path-vector, the cost is a JSONArray of Network
      Element Names.

   o  If the query sent by the client includes cost type path vector,
      the "vtag" filed defined in Section 5.2 has to be included in the
      response.  And the "query-id" information in "vtag" MUST be
      provided to clients.

6.  Examples

   This section lists a series of examples to proceed the multi-flow
   scheduling like the use case in Section 3.

   The recommended workflow is like the following:

6.1.  Workflow

   o  Send the GET request for the whole Information Resource Directory.

   o  Look for the resource of the (Filtered) Cost Map/Endpoint Cost
      Service which contains the path-vector cost type and get the
      resource id of the property map.




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   o  Look for the resource of the property map to check whether it
      supports the desired "prop-types".

   o  Send request to the (Filtered) Cost Map/Endpoint Cost Service and
      get the response with "query-id" information.  Meanwhile, the
      properties of the returned abstract network elements are generated
      in the corresponding Network Element Property Map.

   o  Send request to the Network Element Property Map with the returned
      "query-id" information and get the response.

6.2.  Information Resource Directory Example

   Here is an example of an ALTO server's Information Resource
   Directory.  In this example, both "filtered-multi-cost-map" and
   "default-endpoint-cost-map" support the multi-cost extension and the
   path-vector extension.  Resource "ane-property-map-availbw" supports
   property "availbw" and resource "ane-property-map-delay" supports
   property "delay".

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

       ... NetworkMap Resource ...

       "default-network-map": {
         "uri": "http://alto.example.com/networkmap",
         "media-type": "application/alto-networkmap+json"
       },

       ... Cost Map Resource ...

       "pv-cost-map": {



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         "uri": "http://alto.example.com/pv/ane",
         "media-type": "application/alto-costmap+json",
         "capabilities": {
           "cost-type-names": ["pv-ane"]
         },
         "uses": ["default-network-map"],
         "propertymap": ["ane-property-map-delay",
                         "ane-property-map-availbw"]
       }

       ... Multi-Cost Filtered Map Resource ...

       "filtered-multi-cost-map": {
         "uri": "http://alto.example.com/costmap/multi/filtered",
         "media-type": "application/alto-costmap+json",
         "accepts": "application/alto-costmapfilter+json",
         "uses": ["default-network-map"],
         "capabilities": {
           "max-cost-types": 3,
           "cost-type-names": ["pv-ane",
                               "num-routingcost",
                               "num-hopcount"],
           "cost-constraints": true
         },
         "propertymap": ["ane-property-map-delay",
                         "ane-property-map-availbw"]
       },

       ... Endpoint Cost Service Resource ...

       "default-endpoint-cost-map": {
         "uri": "http://alto.example.com/endpointcost/lookup",
         "media-type": "application/alto-endpointcostmap+json",
         "accepts": "application/alto-endpointcostparams+json",
         "capabilities": {
           "max-cost-types": 3,
           "cost-type-names": ["pv-ane",
                               "num-routingcost",
                               "num-hopcount"],
           "testable-cost-types-names": ["num-hopcount",
                                         "num-routingcost"],
         },
         "propertymap": ["ane-property-map-delay"]
       }

       ... Network Element Property Map Resource ...

       "ane-property-map-delay": {



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         "uri": "http://alto.example.com/propmap/lookup/delay",
         "media-type": "application/alto-propmap+json",
         "accepts": "application/alto-propmapparams+json",
         "capabilities": {
           "domain-types": ["ane"],
           "prop-types": ["delay"]
         }
       }

       "ane-property-map-availbw": {
         "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"]
         }
       }
     }

6.3.  Cost Map Example

   Here is an example of the Cost Map request for path-vector and the
   corresponding response.  In response, the extended "vtag" field is
   included in "meta" to provide "query-id" information.


























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     GET /costmap/pv/ane HTTP/1.1
     Host: alto.example.com
     Accept: application/alto-costmap+json,application/alto-error+json

     HTTP/1.1 200 OK
     Content-Length: [TBD]
     Content-Type: application/alto-costmap+json

     {
       "meta" : {
         "dependent-vtags" : [
           { "resource-id": "default-network-map",
             "tag": "5eb2cb7f8d63a9fab71d9b34cbf763436315542f"
           }
         ],
         "vtag": [
           { "resource-id": "pv-cost-map",
             "tag": "aef527ca2eb7a7566db0597407893e3f8eb1d9dff",
             "query-id": "query0"
           }
         ],
         "cost-type" : {"cost-mode"  : "pv",
                        "cost-metric": "ane"
         }
       },
       "cost-map" : {
           "PID1": { "PID2": ["ane:L001", "ane:L003"],
                     "PID3": ["ane:L002", "ane:L004"] },
           "PID2": { "PID1": ["ane:L003", "ane:L002"],
                     "PID3": ["ane:L003", "ane:L004"] },
           "PID3": { "PID1": ["ane:L004", "ane:L002"],
                     "PID2": ["ane:L004", "ane:L003"] }
       }
     }

6.4.  Multi-Cost Filtered Cost Map Example

   The following example presents the request and response of "filtered-
   multi-cost-map".  In this example, the client is interested in the
   path-vector and numerical routing cost information.  The client uses
   "or-constraints" but all the results satisfy the conditions.  In
   resposne, the extended "vtag" field is included in "meta" to provide
   "query-id" information.

     POST /costmap/multi/filtered HTTP/1.1
     Host: alto.example.com
     Accept: application/alto-costmap+json,application/alto-error+json
     Content-Length: [TBD]



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     Content-Type: application/alto-costmapfilter+json

     {
       "multi-cost-types": [
         {
           "cost-mode": "path-vector",
           "cost-metric": "ane"
         },
         {
           "cost-mode": "numerical",
           "cost-metric": "routingcost"
         }
       ],
       "testable-cost-types": [
         { "cost-mode": "numerical", "cost-metric": "routingcost" },
         { "cost-mode": "numerical", "cost-metric": "hopcount" }
       ],
       "or-constraints": [
         ["[0] ge 50", "[1] le 60"]
       ],
       "pid-flows": [
         { "src": "PID1", "dst": "PID2" },
         { "src": "PID2", "dst": "PID3" }
       ]
     }

     HTTP/1.1 200 OK
     Content-Length: [TBD]
     Content-Type: application/alto-costmap+json

     {
       "meta": {
         "dependent-vtags": [
           {
             "resource-id": "default-network-map",
             "tag": "75ed013b3cb58f896e839582504f622838ce670f"
           }
         ],
         "vtag": [
           {
             "resource-id": "filtered-multi-cost-map",
             "tag": "27612897acf278ffu3287c284dd28841da78213",
             "query-id": "query1"
           }
         ]
       }
       "cost-type": {},
       "multi-cost-types": [



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         { "cost-mode": "path-vector", "cost-metric": "ane" },
         { "cost-mode": "numerical",   "cost-metric": "routingcost"}
       ],

       "cost-map": {
         "PID1": {
           "PID2": [ [ "ane:L001", "ane:L003" ], 55 ]
         },
         "PID2": {
           "PID3": [ [ "ane:L003", "ane:L004" ], 60 ]
         }
       }
     }

6.5.  Endpoint Cost Service Example

   If the ALTO client expects the routing state information between
   endpoints, it can also query the "default-endpoint-cost-map" resource
   which supports path vector.  In resposne, the extended "vtag" field
   is included in "meta" to provide "query-id" information.

  POST /endpointcost/lookup 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": "path-vector", "cost-metric": "ane" },
      { "cost-mode": "numerical",   "cost-metric": "hopcount" }

    ],
    "endpoint-flows": [
      { "src": "ipv4:192.0.2.2",     "dst": "ipv4:203.0.113.45"  },
      { "src": "ipv4:192.0.2.89",    "dst": "ipv4:198.51.100.34" },
      { "src": "ipv4:194.2.3.67",    "dst": "ipv4:202.56.54.230" },
      { "src": "ipv4:203.32.56.102", "dst": "ipv4:202.76.89.103" }
    ]
  }

  HTTP/1.1 200 OK
  Content-Length: [TBD]
  Content-Type: application/alto-endpointcost+json

  {
    "meta": {
      "vtag": [



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        {
          "resource-id": "default-endpoint-cost-map",
          "tag": "73182ffa829dc28c218a1823bb1293dea232885",
          "query-id": "query2"
        }
      ],
      "cost-type": {},
      "multi-cost-types": [
        { "cost-mode": "path-vector", "cost-metric": "ane" },
        { "cost-mode": "numerical", "cost-metric": "hopcount" }
      ]
    },
    "endpoint-cost-map": {
      "ipv4:192.0.2.2": {
        "ipv4:203.0.113.45": [ [ "ane:L10", "ane:L11",
                                 "ane:L15", "ane:L16",
                                 "ane:L17", "ane:L13" ], 100]
      },
      "ipv4:192.0.2.89": {
        "ipv4:198.51.100.34": [ [ "ane:L14", "ane:L11",
                                  "ane:L12", "ane:L18",
                                  "ane:L19" ], 124]
      },
      "ipv4:194.2.3.67": {
        "ipv4:202.56.54.230": [ [ "ane:L21", "ane:L15",
                                  "ane:L16", "ane:L17",
                                  "ane:L18", "ane:L20"], 78]
      },
      "ipv4:203.32.56.102": {
        "ipv4:202.76.89.103": [ [ "ane:L22", "ane:L16",
                                  "ane:L23"], 168]
      }
    }
  }

6.6.  Network Element Property Map Example # 1

   After the client send the query to the Multi-Cost Filtered Cost Map
   "filtered-multi-cost-map" and get the response with query-id "query1"
   (See Section 6.4).  The client send request to the "ane-property-map-
   availbw" with query-id "query1" and get the response.










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     POST /propmap/lookup/availbw 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

     {
       "query-id": "query1",
       "entities" : [ "ane:L001",
                      "ane:L003",
                      "ane:L004" ],
       "properties" : [ "availbw" ]
     }

     HTTP/1.1 200 OK
     Content-Length: [TBD]
     Content-Type: application/alto-propmap+json

     {
       "property-map": {
         "ane:L001": { "availbw": "50" },
         "ane:L003": { "availbw": "70" },
         "ane:L004": { "availbw": "80" }
       }
     }

6.7.  Network Element Property Map Example # 2

   After the client send the query to the Endpoint Cost Service
   "default-endpoint-cost-map" and get the response with query-id
   "query2" (See Section 6.5).  The client send request to the "ane-
   property-map-delay" with query-id "query2" and get the response.



















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     POST /propmap/lookup/delay 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

     {
       "query-id": "query2",
       "entities" : [ "ane:L11",
                      "ane:L15",
                      "ane:L16",
                      "ane:L18" ],
       "properties" : [ "delay" ]
     }

     HTTP/1.1 200 OK
     Content-Length: [TBD]
     Content-Type: application/alto-propmap+json

     {
       "property-map": {
         "ane:L11": { "delay": "25" },
         "ane:L15": { "delay": "40" },
         "ane:L16": { "delay": "60" },
         "ane:L18": { "delay": "10" }
       }
     }

7.  Compatibility

7.1.  Compatibility with Legacy ALTO Clients/Servers

   Legacy ALTO clients SHOULD NOT send queries with path vector
   extension and ALTO servers with this extension SHOULD NOT have any
   compatibility issue.  Legacy ALTO servers do not support cost types
   with the "path-vector" cost mode and MUST NOT announce the extended
   cost types in IRD.  Thus, ALTO clients MUST NOT send queries
   specified in this extension to legacy ALTO servers according to
   Section 11.3.2.3 [RFC7285].

7.2.  Compatibility with Multi-Cost Extensions

   Path Vector is not a testable cost type.  So two conditions have to
   be satisfied when multi-cost supports path-vector extension.  Any
   format of constraints SHOULD NOT be applied to cost type path-vector.

   o  Cost type path-vector MUST NOT be included in "testable-cost-
      types-names" or "testable-cost-types".



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   o  When "testable-cost-types-names" is omitted in the "capabilities"
      and "testable-cost-types" is omitted in the input parameters,
      "constraints" or "or-constraints" SHOULD NOT add any format of
      constraints on cost type path-vector.

7.3.  Compatibility with Incremental Update

   There is no compatibility issue with incremental update extension.

8.  Time to live

   The Network Element Property Map 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 Network Element
   Property Map.

9.  Design Decisions and Discussions

9.1.  Path Vector or Path Graph

   When we introduce the "path-vector" as a cost mode in the Cost Map,
   an unavoidable problem is how to handle multipath.  Because a PID is
   a group of endpoints, it is common that there are multiple paths
   between two PIDs.  The valid routing state information is all of the
   accessible paths.  So in this scenario, the Cost Map Resource SHOULD
   provide the cost values including of the multiple paths.

   A natural solution is to provide an array of path vectors as the cost
   value.  Every path vector in this array means an accessible path
   between the source PID and the destination PID.  It is different from
   the solution of the path vector extension which provides an array of
   network elements.  So it requires to introduce a different cost mode.
   This document proposes this new cost mode named "path-graph".

   However, the "path-graph" will increase the complexity of the Cost
   Map Response.  Since the applications select ALTO as the protocol to
   get the network information rather than other topology-based solution
   such as I2RS, the major reason should be the simplicity.  If we
   provide "path-graph" for each PID pairs, the ALTO client has to
   handle the complex data structure.

   What's more, the "path-vector" is powerful enough to express multiple
   paths.  The simple solution is to list the network elements of all
   accessible paths in a single path vector.  This solution will lose
   the information about paths.  Another solution is to define the path
   as a new type of network elements.  In this way, the path vector can



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   provide an array of paths.  Each element of this array contains a
   path vector of network elements in the Network Element Property Map.

   So in this document, we just introduce "path-vector" as the only
   required cost mode for routing state information.

9.2.  Provide More General Calendar Extension

   Cost Calendar is proposed as a useful ALTO extension to provide the
   historical cost values for Filtered Cost Map Service and Endpoint
   Cost Service.  Since path vector is an extension to these services,
   it SHOULD be compatible with Cost Calendar extension.

   However, the calendar of a path-vector (Endpoint) Cost Map is
   insufficient for the application which requires the historical data
   of routing state information.  The (Endpoint) Cost Map can only
   provide the changes of the paths.  But more useful information is the
   history of network element properties which are recorded in the
   dependent Network Element Property Map.

   Before the Unified Property Map 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 to be updated frequently.  But Network Element
   Property Map as a use case of Unified Property Map will collect the
   real-time information of the network.  It SHOULD be updated as soon
   as possible once the metrics of network elements change.

   So the requirement is to provide a general calendar extension which
   not only meets the Filtered Cost Map and Endpoint Cost Service but
   also applies to the Property Map Service.

9.3.  Snapshot and real-time update

   As the suggested workflow mentioned in Section 6.1, the properties of
   the abstract network elements are computed ahead of the query of
   these properties.  So the properties of abstract network elements are
   likely to be snapshot rather than realt-time value when queried.

10.  Security Considerations

   We can identify multiple potential security issues.  A main security
   issue is network privacy, as the 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



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   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 is
   unlikely to be cachable, 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.

11.  IANA Considerations

11.1.  ALTO Cost Mode Registry

   This document specifies a new cost mode "path-vector".  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.  ALTO Cost Metric Registry

   A new cost metric needs to be registered in the "ALTO Cost Metric
   Registry", listed in Table 1.

                   +-------------+---------------------+
                   | Identifier  | Intended Semantics  |
                   +-------------+---------------------+
                   | ane         | See Section 5.1.1   |
                   +-------------+---------------------+

                        Table 1: ALTO Cost Metrics

11.3.  ALTO Entity Domain Registry

   As proposed in Section 9.2 of [I-D.roome-alto-unified-props], "ALTO
   Entity Domain Registry" is requested.  Besides, a new domain is to be
   registered, listed in Table 2.







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   +-------------+--------------------------+--------------------------+
   | Identifier  | Entity Address Encoding  |  Hierarchy & Inheritance |
   +-------------+--------------------------+--------------------------+
   | ane         |    See Section 5.4.2     |                     None |
   +-------------+--------------------------+--------------------------+

                        Table 2: ALTO Entity Domain

11.4.  ALTO Network Element Property Type Registry

   The "ALTO Network Element Property Type Registry" is required by the
   ALTO Entity Domain "ane", listed in Table 3.

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

               Table 3: ALTO Network Element Property Types

12.  Acknowledgments

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

13.  References

13.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

13.2.  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.



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   [I-D.clemm-i2rs-yang-network-topo]
              Clemm, A., Medved, J., Tkacik, T., Varga, R., Bahadur, N.,
              and H. Ananthakrishnan, "A YANG Data Model for Network
              Topologies", draft-clemm-i2rs-yang-network-topo-01 (work
              in progress), October 2014.

   [I-D.gao-alto-fcs]
              Gao, K., Zhang, J., Wang, J., Xiang, Q., and Y. Yang,
              "ALTO Extension: Flow-based Cost Query", draft-gao-alto-
              fcs-01 (work in progress), March 2017.

   [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-03 (work in progress), September 2016.

   [I-D.ietf-alto-multi-cost]
              Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost
              ALTO", draft-ietf-alto-multi-cost-07 (work in progress),
              March 2017.

   [I-D.lee-alto-app-net-info-exchange]
              Lee, Y., Bernstein, G., Choi, T., and D. Dhody, "ALTO
              Extensions to Support Application and Network Resource
              Information Exchange for High Bandwidth Applications",
              draft-lee-alto-app-net-info-exchange-02 (work in
              progress), July 2013.

   [I-D.roome-alto-unified-props]
              Roome, W., "Extensible Property Maps for the ALTO
              Protocol", draft-roome-alto-unified-props-01 (work in
              progress), July 2016.

   [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,
              <http://www.rfc-editor.org/info/rfc7285>.








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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
   600 Mountain Ave, Rm 3B-324
   Murray Hill, NJ  07974
   USA

   Phone: +1-908-582-7974
   Email: wendy.roome@nokia.com








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   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




























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