ALTO Working Group                                                 Q. Wu
Internet-Draft                                                    Huawei
Intended status: Standards Track                                 Y. Yang
Expires: June 1, 2019 January 9, 2020                                 Yale University
                                                                  Y. Lee
                                                                D. Dhody
                                                                  Huawei
                                                          S. Randriamasy
                                                         Nokia Bell Labs
                                                       November 28, 2018
                                                           July 08, 2019

                     ALTO Performance Cost Metrics
                 draft-ietf-alto-performance-metrics-06
                 draft-ietf-alto-performance-metrics-07

Abstract

   Cost Metric metric is a basic concept in Application-Layer Traffic
   Optimization (ALTO).  It (ALTO), and is used in basic services including both the Cost Map Service
   cost map service and the
   Endpoint Cost Service. endpoint cost service.

   Different applications may benefit from use different Cost Metrics.  For
   example, a Resource Consumer may prefer Resource Providers that offer
   a low delay delivery to the Resource Consumer.  However, cost metrics, but the base ALTO
   base protocol has documented documents only one single cost metric, i.e., the
   generic "routingcost" metric (Sec. metric; see Sec. 14.2 of ALTO base
   specification
   [RFC7285]).

   This document proposes a set [RFC7285].  Hence, if the resource consumer of Cost Metrics, an
   application prefers a resource provider that offers low-delay
   delivery to the resource consumer, the base protocol does not define
   the cost metric to be used.

   ALTO cost metrics can be generic metrics and this document focuses on
   network performance metrics, including network delay, jitter, packet
   loss, hop count, and bandwidth.  These metrics can be derived and
   aggregated from routing protocols with different granularity and
   scope, such as BGP-LS, OSPF-TE and ISIS-TE, or from end-to-end
   traffic management tools.  It currently documents Network Performance Cost Metrics
   reporting on network delay, jitter, packet loss, hop count, and
   bandwidth.  These metrics may then be exposed by an
   ALTO Server to allow applications to determine "where" to connect
   based on network performance criteria.  Additional Cost Metrics involving ISP specific
   considerations or other network technologies cost metrics may
   be documented in
   further versions of this draft. other documents.

   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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   Drafts is at https://datatracker.ietf.org/drafts/current/. http://datatracker.ietf.org/drafts/current/.

   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 June 1, 2019. January 9, 2020.

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   Copyright (c) 2018 2019 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Challenges on data sources and computation of ALTO
       performance metrics  Network Performance Cost Metrics  . . . . . . . . . . . . . .   5
     2.1.  Cost Metric: One Way Delay (owdelay)  . . . . . . . . . .   5
     2.1.  Data sources Challenge
       2.1.1.  Intended Semantics  . . . . . . . . . . . . . . . . .   5
     2.2.  ALTO performance metrics Computation Challenges   6
       2.1.2.  Use and Example . . . . .   5
       2.2.1.  Configuration Parameters Challenge . . . . . . . . .   5
       2.2.2.  Availability of end to end path values  Challenge . .   6
   3.  Network Performance Cost Metrics . . .   6
       2.1.3.  Measurement Considerations  . . . . . . . . . . .   6
     3.1. . .   7
     2.2.  Cost Metric: OWDelay RoundTrip Time (rtt) . . . . . . . . . . . .   7
       2.2.1.  Intended Semantics  . . . . . .   6
     3.2.  Cost Metric: RTT . . . . . . . . . . .   8
       2.2.2.  Use and Example . . . . . . . . . . . .   8
     3.3.  Cost Metric: PDV . . . . . . .   8
       2.2.3.  Measurement Considerations  . . . . . . . . . . . . .  10
     3.4.   9
     2.3.  Cost Metric: Hop Count  . Packet Delay Variation (pdv) . . . . . . . .   9
       2.3.1.  Intended Semantics  . . . . . . . .  12
     3.5.  Cost Metric: Packet Loss . . . . . . . . .  10
       2.3.2.  Use and Example . . . . . . .  14
     3.6.  Cost Metric: Throughput . . . . . . . . . . . .  10
       2.3.3.  Measurement Considerations  . . . . .  16

   4.  Traffic Engineering Performance Cost Metrics . . . . . . . .  18
     4.1.  11

     2.4.  Cost Metric: Link Maximum Reservable Bandwidth Hop Count  . . . . .  19
     4.2.  Cost Metric: Link Residue Bandwidth . . . . . . . . . . .  20
   5.  Security Considerations .  12
       2.4.1.  Intended Semantics  . . . . . . . . . . . . . . . . .  12
       2.4.2.  Use and Example .  22
   6.  IANA . . . . . . . . . . . . . . . . . .  13
       2.4.3.  Measurement Considerations  . . . . . . . . . . . . .  14
     2.5.  Cost Metric: Packet Loss  . . . . . . . .  23
   7.  Acknowledgments . . . . . . . .  14
       2.5.1.  Intended Semantics  . . . . . . . . . . . . . . .  23
   8.  References . .  14
       2.5.2.  Use and Example . . . . . . . . . . . . . . . . . . .  15
       2.5.3.  Measurement Considerations  . . . .  23
     8.1.  Normative References . . . . . . . . .  16
     2.6.  Cost Metric: Throughput . . . . . . . . .  23
     8.2.  Informative References . . . . . . . .  16
       2.6.1.  Intended Semantics  . . . . . . . . .  25
   Authors' Addresses . . . . . . . .  17
       2.6.2.  Use and Example . . . . . . . . . . . . . . .  25

1.  Introduction

   Cost Metric is a basic concept in Application-Layer . . . .  17
       2.6.3.  Measurement Considerations  . . . . . . . . . . . . .  18
   3.  Traffic
   Optimization (ALTO).  It is used in both the Engineering Performance Cost Map Service and the
   Endpoint Metrics  . . . . . . . .  18
     3.1.  Cost Service.  In particular, applications may benefit from
   knowing network performance measured on several Metric: Link Maximum Reservable Bandwidth  . . . . .  19
       3.1.1.  Intended Semantics  . . . . . . . . . . . . . . . . .  19
       3.1.2.  Use and Example . . . . . . . . . . . . . . . . . . .  19
       3.1.3.  Measurement Considerations  . . . . . . . . . . . . .  20
     3.2.  Cost Metrics.  For
   example, a more delay-sensitive application may focus on latency, Metric: Link Residue Bandwidth . . . . . . . . . . .  21
       3.2.1.  Intended Semantics  . . . . . . . . . . . . . . . . .  21
       3.2.2.  Use and
   a more bandwidth-sensitive application may focus on available
   bandwidth.

   This document introduces a set of new cost metrics, listed in
   Table 1, to support the aforementioned applications and allow them to
   determine "where" to connect based on network performance criteria.
   Hence, this document extends the base ALTO protocol [RFC7285], which
   defines only a single cost metric, i.e., the generic "routingcost"
   metric (Sec. 14.2 of ALTO base specification [RFC7285]).

   +----------+--------------+----------------------------------------+
   |Namespace | Property     | Reference                              |
   +----------+--------------+----------------------------------------+
   |          |  owdelay     | See Section 3,[RFC2679] Section 3.6    |
   |          |   rtt        | See Section 4,[RFC2681] Section 2.6    |
   |          |   pdv        | See Section 5,[RFC3393] Section 2.6    |
   |          | hopcount     | See Section 6,[RFC7285]                |
   |          | pktloss      | See Section 7,[RFC7680] Section 2.6    |
   |          | throughput   | See Section x, [RFC6349] Section 3.3   |
   |          | maxresbw     | See Section 8.1,[RFC5305] Section 3.5  |
   |          | residbw      | See Section 8.2,[RFC7810] Section 4.5  |
   +----------+--------------+----------------------------------------+
                          Table 1.

   The purpose of this draft is to list the metrics likely to be exposed
   to ALTO Clients, including those already specified in other
   standardization groups and as such it does not claim novelty on all
   the specified metrics.  Some metrics may have values produced by
   standard measurement methods such as those specified in IPPM, some
   may be ISP dependent such as those registered in ISIS or OSPF-TE.  In
   this case, this document will refer to the relevant specifications.

   An ALTO server may provide a subset of the cost metrics described in
   this document.  These cost metrics can be retrieved and aggregated
   from routing protocols or other traffic measurement management tools
   (See Figure 1).  Note that these cost metrics are optional and not
   all them need to be exposed to applications.  For example, those that
   are subject to privacy concerns should not be provided to
   unauthorized ALTO clients.

   +--------+   +--------+  +--------+
   | Client |   | Client |  | Client |
   +----^---+   +---^----+  +---^----+
        |           |           |
        +-----------|-----------+
              NBI   |ALTO protocol
                    |
                    |
                 +--+-----+  retrieval      +---------+
                 |  ALTO  |<----------------| Routing |
                 | Server |  and aggregation|         |
                 |        |<-------------+  | Protocol|
                 +--------+              |  +---------+
                                         |
                                         |  +---------+
                                         |  |Management
                                         ---|         |
                                            |  Tool   |
                                            +---------+
                    Figure 1.End-to-End Path Example . . . . . . . . . . . . . . . . . . .  21
       3.2.3.  Measurement Considerations  . . . . . . . . . . . . .  22
   4.  Operational Considerations  . . . . . . . . . . . . . . . . .  23
     4.1.  Data Source Considerations  . . . . . . . . . . . . . . .  23
     4.2.  Computation Considerations  . . . . . . . . . . . . . . .  24
       4.2.1.  Configuration Parameters Considerations . . . . . . .  24
       4.2.2.  Availability Considerations . . . . . . . . . . . . .  24
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  25
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  25
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   Cost Metrics Exposing

   When an ALTO server supports Metric is a cost metric defined basic concept in this document,
   it MUST announce this metric Application-Layer Traffic
   Optimization (ALTO).  It is used in its IRD.

   Additionally, future versions of this document may define network
   metric values that stem from both measurements and provider policies
   such as many metrics related to end-to-end path bandwidth.

   As for the reliability ALTO cost map service
   and trust in the exposed metric values, ALTO endpoint cost service, to allow applications SHOULD rapidly give up using ALTO-based guidance if they
   feel the exposed information does not preserve their performance
   level or even degrades it.

   Following to request
   network cost metrics.

   Different applications may use different cost metrics.  Hence, the
   ALTO base protocol, this document uses JSON to specify
   the value type of each defined metric.  See [RFC4627] for JSON data
   type specification.

2.  Challenges on data sources and computation of protocol [RFC7285] introduces an ALTO performance Cost Metric Registry
   (Section 14.2 of [RFC7285]) as a systematic mechanism to allow
   different metrics

2.1.  Data sources Challenge

   An ALTO server needs data sources to compute be specified.  For example, a more delay-
   sensitive application may want to use latency related metrics, and a
   more bandwidth-sensitive application may want to use bandwidth
   related metrics.  The ALTO base protocol [RFC7285], however, has
   registered only one single cost metric, i.e., the generic
   "routingcost" metric; no latency or bandwidth related metrics are
   defined.

   This document registers a set of new cost metrics
   described specified in this document.
   Table 1, to support the aforementioned applications, to allow them to
   determine "where" to connect based on network performance criteria.
   This document does not define follows the exact
   data sources.  For example, guideline (Section 14.2 of [RFC7285]) of
   the ALTO server may use log servers or
   the OAM system as its data source [RFC7971].  In particular, the base protocol on registering ALTO cost
   metrics defined in this document can be computed using routing
   systems as metrics.  Hence it
   specifies the data sources.  Mechanisms defined in [RFC2681],
   [RFC3393], [RFC7679], [RFC7680], [RFC3630], [RFC3784], [RFC7471],
   [RFC7810], [RFC7752] and [I-D.ietf-idr-te-pm-bgp] that allow an ALTO
   Server to retrieve identifier, the intended semantics, and derive the necessary information to compute security
   considerations of each one of the metrics that we describe defined in this document. Table 1.

   +--------------------------+-------------+-----------------------+
   | Metric                   | Definition  |  Origin               |
   +--------------------------+-------------+-----------------------+
   | One challenge lies in the data sources originating the ALTO metric
   values.  The very important purpose of ALTO is to guide application
   traffic with provider network centric information that may be exposed
   to ALTO Clients Way Delay            | Section 2.1 | [RFC2679] Section 3.6 |
   | Round Trip Delay         | Section 2.2 | [RFC2681] Section 2.6 |
   | Packet Delay Variation   | Section 2.3 | [RFC3393] Section 2.6 |
   | Hop Count                | Section 2.4 | [RFC7285]             |
   | Packet Loss              | Section 2.5 | [RFC7680] Section 2.6 |
   | Throughput               | Section 2.6 | [RFC6349] Section 3.3 |
   | Max Reservable Bandwidth | Section 3.1 | [RFC5305] Section 3.5 |
   | Residue Bandwidth        | Section 3.2 | [RFC7810] Section 4.5 |
   +------------+---------------------------------------------------+
      Table 1. Cost Metrics Defined in the form this Document

   The purpose of network performance metric values.
   Not all this document is to ensure proper usage of these the metrics have values produced
   by standardized
   measurement methods or routing protocols.  Some ALTO clients.  It does not claim novelty of them involve
   provider-centric policy considerations. the metrics.  Some of them may describe
   wireless or cellular networks.  To reliably guide users and
   applications while preserving provider privacy, ALTO performance
   metric values may also add abstraction to measurements or provide
   unitless performance scores.

2.2.  ALTO performance
   these metrics Computation Challenges

   The metric values exposed are already specified by an ALTO server may result from
   additional processing on measurements from data sources to compute
   exposed metrics.  This may involve data processing tasks standards such as
   aggregating the results across multiple systems, removing outliers,
   and creating additional statistics.  There IPPM; some
   are two challenges on ISP dependent such as those registered in ISIS or OSPF-TE.  This
   document will refer to the
   computation of relevant specifications.

   An ALTO performance metrics.

2.2.1.  Configuration Parameters Challenge

   Performance metrics often depend on configuration parameters.  For
   example, the value server may provide only a subset of packet loss rate depends on the measurement
   interval and varies over time.  To handle cost metrics
   described in this issue, document.  Hence, all cost metrics defined in this
   document are optional and not all them need to be exposed to
   applications.  For example, those that are subject to privacy
   concerns should not be provided to unauthorized ALTO clients.

   When an ALTO server
   may collect data on time periods covering the previous supports a cost metric defined in this document,
   it MUST announce this metric in its information resource directory
   (IRD).

   The cost metrics defined in this document can be retrieved and current
   time
   aggregated from routing protocols or only collect data other traffic measurement
   management tools, with corresponding operational issues.  A potential
   architecture on present time.  The ALTO server may
   further aggregate computing these data to provide an abstract and unified view
   that can be metrics is shown in Figure 1 below.
   In Section 4, we discuss in more useful to applications.  To make detail the ALTO client
   better understand operations issues and how
   to use these address them.

     +--------+   +--------+  +--------+
     | Client |   | Client |  | Client |
     +----^---+   +---^----+  +---^----+
          |           |           |
          +-----------|-----------+
                NBI   |ALTO protocol
                      |
                      |
                   +--+-----+  retrieval      +---------+
                   |  ALTO  |<----------------| Routing |
                   | Server |  and aggregation|         |
                   |        |<-------------+  | Protocol|
                   +--------+              |  +---------+
                                           |
                                           |  +---------+
                                           |  |Management
                                           ---|         |
                                              |  Tool   |
                                              +---------+
   Figure 1. Potential framework to compute performance data, the cost metrics

   An ALTO server
   may provide the client with introducing these metrics should also consider
   security issues.  As a generic security consideration on the validity period of
   reliability and trust in the exposed metric
   values.

2.2.2.  Availability of end to end path values Challenge

   Applications value information relating to bandwidth availability
   whereas bandwidth related metrics can often be only measured at values, applications
   SHOULD rapidly give up using ALTO-based guidance if they feel the
   link level.  This document specifies a set of link-level bandwidth
   related values that may be
   exposed as such by an ALTO server.  The
   server may also expose other metrics derived from information does not preserve their aggregation
   and having different levels of endpoint granularity, e.g., link
   endpoints performance level or session endpoints.  The metric specifications may also
   expose even
   degrades it.  We discuss security considerations in more details in
   Section 5.

   Following the utilized aggregation laws.

3. ALTO base protocol, this document uses JSON to specify
   the value type of each defined metric.  See [RFC4627] for JSON data
   type specification.

2.  Network Performance Cost Metrics

   This section introduces generic ALTO network performance metrics such
   as one way delay,round trip delay,hop count,packet loss,throughput
   derived and aggregated from routing protocols or from end to end
   traffic management tools.

3.1. from end to end
   traffic management tools.

2.1.  Cost Metric: One Way Delay (owdelay)

   Metric name:

      One Way Delay

   Metric Identifier:

      owdelay

2.1.1.  Intended Semantics

   Metric Description: To specify spatial and temporal aggregated delay
   of a stream of packets exchanged between the specified source and
   destination or the time that the packet spends to travel from source
   to destination.  The spatial aggregation level is specified in the
   query context (e.g., PID to PID, or endpoint to endpoint).

   Metric Representation: The metric value type is a single 'JSONNumber'
   type value containing a non-negative integer component that may be
   followed by an exponent part.  See section 8.4.3 of [I-D.ietf-ippm-
   initial-registry] for metric unit.  The unit is expressed in
   milliseconds in this document.

2.1.2.  Use and Example

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

   Example 1: Delay value on source-destination endpoint pairs

   POST /endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
     application/alto-endpointcost+json,application/alto-error+json

   {
     "cost-type": {"cost-mode" : "numerical",
                   "cost-metric" : "owdelay"},
     "endpoints" : {
       "srcs": [ "ipv4:192.0.2.2" ],
       "dsts": [
         "ipv4:192.0.2.89",
         "ipv4:198.51.100.34",
         "ipv6:2000::1:2345:6789:abcd"
       ]
     }
   }
   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
     "meta" :{
       "cost-type": {"cost-mode" : "numerical",
                     "cost-metric" : "owdelay"
        }
      },
       "endpoint-cost-map" : {
         "ipv4:192.0.2.2": {
           "ipv4:192.0.2.89"    : 10,
           "ipv4:198.51.100.34" : 20,
           "ipv6:2000::1:2345:6789:abcd"  : 30,
       }
     }
   }

2.1.3.  Measurement Considerations

   Method of Measurement or Calculation:

      See section 8.3 of [I-D.ietf-ippm-initial-registry] for potential
      measurement method.

   Measurement Point(s) with Potential Measurement Domain:

      See Section 4.1, Data sources for potential data sources.

   Measurement Timing:

      See section 8.3.5 of [I-D.ietf-ippm-initial-registry] for
      potential measurement timing considerations.

2.2.  Cost Metric: OWDelay RoundTrip Time (rtt)

   Metric name:

      One Way Delay

      Round Trip Time

   Metric Identifier:

      rtt

2.2.1.  Intended Semantics

   Metric Description: To specify spatial and temporal aggregated round
   trip delay of a stream of
      packets exchanged between the specified source and destination or the time
   that the packet spends to travel from source to
      destination. destination and then
   from destination to source.  The spatial aggregation level is
   specified in the query context (e.g., PID to PID, or endpoint to
   endpoint).

   Method of Measurement or Calculation:

      See section 8.3 of [I-D.ietf-ippm-initial-registry] for
      Measurement Method.

   Units of Measurement:

   Metric Representation: The metric value type is a single 'JSONNumber'
   type value containing a non-negative integer component that may be
   followed by an exponent part.  See section 8.4.3 4.4.3 of [I-D.ietf-ippm-initial-registry] [I-D.ietf-ippm-
   initial-registry] for Measurement Unit.  The unit is expressed in
   milliseconds in this document.

2.2.2.  Use and Example

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

   Example 2: Roundtrip Delay value on source-destination endpoint pairs

   POST /endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
     application/alto-endpointcost+json,application/alto-error+json

   {
    "cost-type": {"cost-mode" : "numerical",
                  "cost-metric" : "rtt"},
     "endpoints" : {
        "srcs": [ "ipv4:192.0.2.2" ],
        "dsts": [
          "ipv4:192.0.2.89",
          "ipv4:198.51.100.34",
          "ipv6:2000::1:2345:6789:abcd"
        ]
      }
   }
    HTTP/1.1 200 OK
    Content-Length: TBA
    Content-Type: application/alto-endpointcost+json
    {
      "meta" :{
        "cost-type": {"cost-mode" : "numerical",
                      "cost-metric" : "rtt"
         }
       },
        "endpoint-cost-map" : {
          "ipv4:192.0.2.2": {
            "ipv4:192.0.2.89"    : 4,
            "ipv4:198.51.100.34" : 3,
            "ipv6:2000::1:2345:6789:abcd"  : 2,
        }
      }
    }

2.2.3.  Measurement Considerations

   Method of Measurement or Calculation:

      See section 4.3 of [I-D.ietf-ippm-initial-registry] for potential
      measurement method.

   Measurement Point(s) with Potential Measurement Domain:

      See section 2.1, 4.1, Data sources.

   Measurement Timing:

      See section 8.3.5 4.3.5 of [I-D.ietf-ippm-initial-registry] for
      Measurement Timing.

   Use

2.3.  Cost Metric: Packet Delay Variation (pdv)

   Metric name:

      Packet Delay Variation

   Metric Identifier:

      pdv

2.3.1.  Intended Semantics

   Metric Description: To specify spatial and temporal aggregated jitter
   (packet delay variation) with respect to the minimum delay observed
   on the stream over the specified source and Applications: destination.  The spatial
   aggregation level is specified in the query context (e.g., PID to
   PID, or endpoint to endpoint).

   Metric Representation: The metric value Type type is a single 'JSONNumber'
   type value containing a non-negative integer component that may be
   followed by an exponent part.  See section 5.4.4 of [I-D.ietf-ippm-
   initial-registry] for Measurement Unit.  The Cost Mode unit is encoded as a US-ASCII
      string. expressed in
   milliseconds in this document.

2.3.2.  Use and Example

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

   Example 1: Delay 3: PDV value on source-destination endpoint pairs

   POST /endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
      application/alto-endpointcost+json,application/alto-error+json

   {
     "cost-type": {"cost-mode" : "numerical",
      "cost-metric" : "owdelay"}, "pdv"},
     "endpoints" : {
       "srcs": [ "ipv4:192.0.2.2" ],
       "dsts": [
         "ipv4:192.0.2.89",
         "ipv4:198.51.100.34",
         "ipv6:2000::1:2345:6789:abcd"
       ]
     }
   }
   HTTP/1.1 200 OK
    Content-Length: TBA
    Content-Type: application/alto-endpointcost+json
   {
     "meta" :{
       "cost-type": {"cost-mode" :
     "meta": {
              "cost type": {
              "cost-mode": "numerical",
                     "cost-metric" : "owdelay"
              "cost-metric":"delayjitter"
       }
      },
       "endpoint-cost-map" :
     "endpoint-cost-map": {
              "ipv4:192.0.2.2": {
              "ipv4:192.0.2.89"    : 10, 0
              "ipv4:198.51.100.34" : 20, 1
              "ipv6:2000::1:2345:6789:abcd"  : 30, 5
            }
         }
      }

3.2.

2.3.3.  Measurement Considerations

   Method of Measurement or Calculation:

      See Section 5.3 of [I-D.ietf-ippm-initial-registry] for potential
      measurement method.

   Measurement Point(s) with Potential Measurement Domain:

      See Section 4.1, Data sources for potential data sources.

   Measurement Timing:

      See Section 5.3.5 of [I-D.ietf-ippm-initial-registry] for
      Measurement Timing.

2.4.  Cost Metric: RTT Hop Count

   The metric hopcount is mentioned in [RFC7285] Section 9.2.3 as an
   example.  This section further clarifies its properties.

   Metric name:

      Round Trip Delay

      Hop count

   Metric Identifier:

      hopcount

2.4.1.  Intended Semantics

   Metric Description:

      To specify spatial and temporal aggregated round trip delay
      between the specified source and destination or number of hops in the time that path between the
      packet spends to travel from source to destination
      endpoint and then from the destination to source. endpoint.  The spatial aggregation level hop count is specified a basic
      measurement of distance in the query context (e.g., PID to PID, or endpoint a network and can be exposed as Router
      Hops, in direct relation to endpoint).

   Method of Measurement or Calculation:

      See section 4.3 of [I-D.ietf-ippm-initial-registry] for
      Measurement Method.

   Units of Measurement:

      See section 4.4.3 of [I-D.ietf-ippm-initial-registry] for
      Measurement Unit. the routing protocols originating this
      information.

   Metric Representation:

      The metric value type is a single 'JSONNumber' type value
      containing a non-negative integer component.  The unit is expressed in milliseconds in this
      document.

   Measurement Point(s) with Potential Measurement Domain:

      See section 2.1, Data sources.

   Measurement Timing:

      See section 4.3.5 of [I-D.ietf-ippm-initial-registry] for
      Measurement Timing. integer
      number.

2.4.2.  Use and Applications:

      See section 3 for use and application. Example 2: Round Trip Delay

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

   Example 4: hopcount value on source-destination endpoint pairs

   POST /endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
     application/alto-endpointcost+json,application/alto-error+json

     {
       "cost-type": {"cost-mode" : "numerical",
        "cost-metric" : "rtt"}, "hopcount"},
       "endpoints" : {
         "srcs": [ "ipv4:192.0.2.2" ],
         "dsts": [
           "ipv4:192.0.2.89",
           "ipv4:198.51.100.34",
           "ipv6:2000::1:2345:6789:abcd"
         ]
       }
     }

   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
      "meta" :{
        "cost-type": {"cost-mode" :
       "meta": {
                  "cost type": {
                "cost-mode": "numerical",
                      "cost-metric" : "rtt"
                "cost-metric":"hopcount"}
          }
       },
        "endpoint-cost-map" :
      "endpoint-cost-map": {
              "ipv4:192.0.2.2": {
              "ipv4:192.0.2.89"   : 4,
            "ipv4:198.51.100.34" : 5,
              "ipv4:198.51.100.34": 3,
              "ipv6:2000::1:2345:6789:abcd" : 2,
                                }
                }
    }

3.3.

2.4.3.  Measurement Considerations

   Method of Measurement or Calculation:

      The hop count can be calculated based on the number of routers
      from the source endpoint through which data must pass to reach the
      destination endpoint.

   Measurement Point(s) with Potential Measurement Domain:

      The hop count can be measured at the source endpoint by
      traceroute.

   Measurement Timing:

      Upon need, the traceroute can use UDP probe message or other
      implementations that use ICMP and TCP to discover the hop counts
      along the path from source endpoint to destination endpoint.

2.5.  Cost Metric: PDV Packet Loss

   Metric name:

      Packet Delay Variation loss

   Metric Identifier:

      pktloss

2.5.1.  Intended Semantics

   Metric Description:

      To specify spatial and temporal aggregated jitter (packet delay
      variation) with respect to the minimum delay observed on the
      stream packet loss over the
      specified source and destination.  The spatial aggregation level
      is specified in the query context (e.g., PID to PID, or endpoint
      to endpoint).

   Method of Measurement or Calculation:

      See section 5.3 of [I-D.ietf-ippm-initial-registry] for
      Measurement Method.

   Units of Measurement:

      See section 5.4.4 of [I-D.ietf-ippm-initial-registry] for
      Measurement Unit.

   Metric Representation:

      The metric value type is a single 'JSONNumber' type value which be
      be non-negative integer.  The unit is expressed in milliseconds in this
      document.

   Measurement Point(s) with Potential Measurement Domain:

      See section 2.1, Data sources.

   Measurement Timing:

      See section 5.3.5 of [I-D.ietf-ippm-initial-registry] for
      Measurement Timing. percentile.

2.5.2.  Use and Applications:

      See section 3 for use and application. Example 3: PDV

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

   Example 5: pktloss value on source-destination endpoint pairs

   POST /endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
     application/alto-endpointcost+json,application/alto-error+json

     {
       "cost-type": {"cost-mode" : "numerical",
        "cost-metric" : "pdv"}, "pktloss"},
       "endpoints" : {
         "srcs": [ "ipv4:192.0.2.2" ],
         "dsts": [
           "ipv4:192.0.2.89",
           "ipv4:198.51.100.34",
           "ipv6:2000::1:2345:6789:abcd"
         ]
       }
     }

   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
       "meta": {
                  "cost type": {
                "cost-mode": "numerical",
             "cost-metric":"delayjitter"
                "cost-metric":"pktloss"}
          }
       },
      "endpoint-cost-map": {
              "ipv4:192.0.2.2": {
              "ipv4:192.0.2.89"   : 0
             "ipv4:198.51.100.34" : 1 0,
              "ipv4:198.51.100.34": 0,
              "ipv6:2000::1:2345:6789:abcd" : 5 0,
                                }
                }
    }

3.4.  Cost Metric: Hop Count

   The metric hopcount is mentioned in [RFC7285] section 9.2.3 as an
   example.  This section further clarifies its properties.

   Metric name:

      Hop count

   Metric Description:

      To specify the number of hops in the path between the source
      endpoint and the destination endpoint.  The hop count is a basic
      measurement of distance in a network and can be exposed as Router
      Hops, in direct relation to the routing protocols originating this
      information.

2.5.3.  Measurement Considerations

   Method of Measurement or Calculation:

      The hop count can be calculated based on the number of routers
      from the source endpoint through which data must pass to reach the
      destination endpoint.

   Units

      See Section 2.6 of Measurement:

      The unit is integer number. [RFC7680] for Measurement Method.

   Measurement Point(s) with Potential Measurement Domain:

      The hop count can be measured at the source endpoint by
      traceroute.

      See Section 4.1 this document, Data sources.

   Measurement Timing:

      Upon need, the traceroute can use UDP probe message or other
      implementations that use ICMP

      See Section 2 and TCP to discover the hop counts
      along Section 3 of [RFC7680] for Measurement Timing.

2.6.  Cost Metric: Throughput

   Metric name:

      Throughput

   Metric Identifier:

      throughput

2.6.1.  Intended Semantics

   Metric Description:

      To specify spatial and temporal throughput over the path from specified
      source and destination.  The spatial aggregation level is
      specified in the query context (e.g., PID to PID, or endpoint to destination endpoint.
      endpoint).

   Metric Representation:

      The unit is Mbps.

2.6.2.  Use and Applications:

      See section 3 for use and application. Example 4: hopcount

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

   Example 5: throughtput value on source-destination endpoint pairs

   POST /endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
     application/alto-endpointcost+json,application/alto-error+json

   {
     "cost-type": {"cost-mode" : "numerical",
                   "cost-metric" : "hopcount"}, "throughput"},
     "endpoints" : {
       "srcs": [ "ipv4:192.0.2.2" ],
       "dsts": [
          "ipv4:192.0.2.89",
          "ipv4:198.51.100.34",
          "ipv6:2000::1:2345:6789:abcd"
       ]
     }
   }
   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
     "meta": {
        "cost type": {
           "cost-mode": "numerical",
                "cost-metric":"hopcount"}
           "cost-metric":"throughput"
       }
     }
       },
     "endpoint-cost-map": {
       "ipv4:192.0.2.2": {
         "ipv4:192.0.2.89"   : 5, 25.6,
         "ipv4:198.51.100.34": 3, 12.8,
         "ipv6:2000::1:2345:6789:abcd" : 2,
                                } 42.8,
     }
   }

3.5.

2.6.3.  Measurement Considerations

   Method of Measurement or Calculation:

      See Section 3.3 of [RFC6349] for Measurement Method.

   Measurement Point(s) with Potential Measurement Domain:

      See Section 4.1 of this document.

   Measurement Timing:

      Similar to RTT.  See Section 4.3.5 of [I-D.ietf-ippm-initial-
      registry] for Measurement Timing.

3.  Traffic Engineering Performance Cost Metrics

   This section introduces ALTO network performance metrics that may be
   aggregated from network metrics measured on links and specified in
   other documents.  In particular, the bandwidth related metrics
   specified in this section are only available through link level
   measurements.  For some of these metrics, the ALTO Server may further
   expose aggregated values while specifying the aggregation laws.

3.1.  Cost Metric: Packet Loss Link Maximum Reservable Bandwidth

   Metric name:

      Packet loss

      Maximum Reservable Bandwidth

   Metric Identifier:

      maxresbw

3.1.1.  Intended Semantics

   Metric Description:

      To specify spatial and temporal aggregated packet loss maximum reservable bandwidth over
      the specified source and destination.  The value is corresponding
      to the maximum bandwidth that can be reserved (motivated from RFC
      3630 Sec. 2.5.7.).  The spatial aggregation level unit is specified in
      the query context (e.g., PID to PID, or endpoint
      to endpoint).

   Method of Measurement or Calculation:

      See section 2.6 of [RFC7680] for Measurement Method.

   Units of Measurement: (e.g., PID to PID, or endpoint to endpoint).

   Metric Representation:

      The unit metric value type is percentile.

   Measurement Point(s) with Potential Measurement Domain:

      See section 2.1, Data sources.

   Measurement Timing:

      See section 2 and section3 a single 'JSONNumber' type value that is
      non-negative.  The unit of [RFC7680] for Measurement Timing. measurement is mbps.

3.1.2.  Use and Applications:

      See section 3 for use and application. Example 5: pktloss

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

     Example 6: maxresbw value on source-destination endpoint pairs

  POST /endpointcost/lookup

   POST/ endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
     application/alto-endpointcost+json,application/alto-error+json

     {
      "cost-type": {"cost-mode" :
       "cost-type" { "cost-mode":  "numerical",
       "cost-metric" : "pktloss"},
      "endpoints" :
                     "cost-metric":  "maxresbw"},
       "endpoints":  {
         "srcs": [ "ipv4:192.0.2.2" "ipv4 : 192.0.2.2" ],
         "dsts": [
           "ipv4:192.0.2.89",
           "ipv4:198.51.100.34",
           "ipv6:2000::1:2345:6789:abcd"
         ]
       }
     }

   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
       "meta": {
                  "cost type":
              "cost-type": {
              "cost-mode": "numerical",
                "cost-metric":"pktloss"}
              "cost-metric": "maxresbw"
              }
       },
      "endpoint-cost-map":
     " endpoint-cost-map": {
              "ipv4:192.0.2.2":
             "ipv4:192.0.2.2" {
             "ipv4:192.0.2.89" :    0,
             "ipv4:198.51.100.34": 0,
              "ipv6:2000::1:2345:6789:abcd" : 0, 2000,
             "ipv6:2000::1:2345:6789:abcd":  5000,
                               }
              }
   }

3.6.

3.1.3.  Measurement Considerations

   Method of Measurement or Calculation:

      Maximum Reservable Bandwidth is the bandwidth measured between two
      directly connected IS-IS neighbors or OSPF neighbors.  See
      Section 3.5 of [RFC5305] for Measurement Method.

   Measurement Point(s) with Potential Measurement Domain:

      See Section 4.1 this document for discussions.

   Measurement Timing:

      See Section 3.5 of [RFC5305] and Section 5 of [RFC7810] for
      Measurement Timing.

3.2.  Cost Metric: Throughput Link Residue Bandwidth

   Metric name:

      Throughput

      Residue Bandwidth

   Metric Identifier:

      residuebw

3.2.1.  Intended Semantics

   Metric Description:

      To specify spatial and temporal throughput residual bandwidth over the
      specified source and destination.  The value is calculated by
      subtracting tunnel reservations from Maximum Bandwidth (motivated
      from [RFC7810], Section 4.5.).  The spatial aggregation level unit is
      specified in the query context (e.g., PID to PID, or endpoint to
      endpoint).

   Method of Measurement or Calculation:

      See section 3.3 of [RFC6349] for Measurement Method.

   Units of Measurement:

   Metric Representation:

      The unit metric value type is Mbps.

   Measurement Point(s) with Potential Measurement Domain:

      See section 2.1, Data sources.

   Measurement Timing:

      Similar to RTT,See section 4.3.5 a single 'JSONNumber' type value that is
      non-negative.  The unit of [I-D.ietf-ippm-initial-
      registry] for Measurement Timing. measurement is mbps.

3.2.2.  Use and Applications:

      See section 3 for use and application. Example 5: throughtput

   This metric could be used as a cost metric constraint attribute used
   either together with cost metric attribute 'routingcost' or on its
   own or as a returned cost metric in the response.

   Example 7: residuebw value on source-destination endpoint pairs

  POST /endpointcost/lookup

   POST/ endpointcost/lookup HTTP/1.1
   Host: alto.example.com
   Content-Length: TBA
   Content-Type: application/alto-endpointcostparams+json
   Accept:
     application/alto-endpointcost+json,application/alto-error+json

     {
      "cost-type": {"cost-mode" : { "cost-mode":  "numerical",
       "cost-metric" : "throughput"},
      "endpoints" :
                     "cost-metric":  "residuebw"},
      "endpoints":  {
        "srcs": [ "ipv4:192.0.2.2" "ipv4 : 192.0.2.2" ],
        "dsts": [
          "ipv4:192.0.2.89",
          "ipv4:198.51.100.34",
          "ipv6:2000::1:2345:6789:abcd"
        ]
      }
     }
  }

   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
      "meta": {
                     "cost type":
             "cost-type" {
             "cost-mode": "numerical",
                   "cost-metric":"throughput"}
             "cost-metric": "residuebw"
           }
       },
         "endpoint-cost-map":
   "endpoint-cost-map" {
                 "ipv4:192.0.2.2":
            "ipv4:192.0.2.2" {
            "ipv4:192.0.2.89" : 25.6,    0,
            "ipv4:198.51.100.34": 12.8,
                 "ipv6:2000::1:2345:6789:abcd" : 42.8, 2000,
            "ipv6:2000::1:2345:6789:abcd":  5000,
                          }
           }
   }

3.2.3.  Measurement Considerations

   Method of Measurement or Calculation:

      Residue Bandwidth is the Unidirectional Residue bandwidth measured
      between two directly connected IS-IS neighbors or OSPF neighbors.
      See Section 4.5 of [RFC7810] for Measurement Method.

   Measurement Point(s) with Potential Measurement Domain:

      See Section 4.1 of this document.

   Measurement Timing:

      See Section 5 of [RFC7810] for Measurement Timing.

4.  Traffic Engineering Performance Cost Metrics

   This section introduces  Operational Considerations

   It can be non-trivial for an ALTO network server to derive the metrics.
   Also, the exact infrastructure and algorithms can vary from different
   networks, and are outside the scope of this document.  However, since
   they present challenges, we discuss these common challenges.

   Also, the performance metrics specified in this document are similar,
   in that they may be
   aggregated from network metrics measured on links use similar data sources and specified have similar issues in
   other documents.
   their calculation.  Hence, we specify common issues unless one metric
   has its unique challenges.

4.1.  Data Source Considerations

   An ALTO server needs data sources to compute the cost metrics
   described in this document.  This document does not define the exact
   data sources.  For example, the ALTO server may use log servers or
   the OAM system as its data source [RFC7971].  In particular, the bandwidth related cost
   metrics
   specified defined in this section are only available through link level
   measurements.  For some of these metrics, document can be computed using routing
   systems as the data sources.  Mechanisms defined in [RFC2681],
   [RFC3393], [RFC7679], [RFC7680], [RFC3630], [RFC3784], [RFC7471],
   [RFC7810], [RFC7752] and [I-D.ietf-idr-te-pm-bgp] that allow an ALTO
   Server may further
   expose aggregated values while specifying the aggregation laws.

4.1.  Cost Metric: Link Maximum Reservable Bandwidth

   Metric name:

      Maximum Reservable Bandwidth

   Metric Description:

      To specify spatial to retrieve and temporal maximum reservable bandwidth over derive the specified source and destination.  The value is corresponding necessary information to compute
   the maximum bandwidth metrics that can be reserved (motivated from RFC
      3630 Sec. 2.5.7.).  The spatial aggregation unit is specified we describe in this document.

   One challenge lies in the query context (e.g., PID to PID, or endpoint to endpoint).

   Method data sources originating the ALTO metric
   values.  The very important purpose of Measurement or Calculation:

      Maximum Reservable Bandwidth ALTO is to guide application
   traffic with provider network centric information that may be exposed
   to ALTO Clients in the bandwidth measured between two
      directly connected IS-IS neighbors or OSPF neighbors, See section
      3.5 of [RFC5305] for Measurement Method.

   Units form of Measurement:

      The unit network performance metric values.
   Not all of these metrics have values produced by standardized
   measurement is byte per seconds.

   Measurement Point(s) with Potential Measurement Domain:

      See section 2.1, Data sources.

   Measurement Timing:

      See section 3.5 methods or routing protocols.  Some of [RFC5305] them involve
   provider-centric policy considerations.  Some of them may describe
   wireless or cellular networks.  To reliably guide users and
   applications while preserving provider privacy, ALTO performance
   metric values may also add abstraction to measurements or provide
   unitless performance scores.

4.2.  Computation Considerations

   The metric values exposed by an ALTO server may result from
   additional processing on measurements from data sources to compute
   exposed metrics.  This may involve data processing tasks such as
   aggregating the results across multiple systems, removing outliers,
   and section 5 creating additional statistics.  There are two challenges on the
   computation of [RFC7810] for
      Measurement Timing.

   Use and Applications:

      See section 3 for use and application.

  Example 6: maxresbw ALTO performance metrics.

4.2.1.  Configuration Parameters Considerations

   Performance metrics often depend on configuration parameters.  For
   example, the value of packet loss rate depends on source-destination endpoint pairs

  POST/ endpointcost/lookup HTTP/1.1
  Host: alto.example.com
  Content-Length: TBA
  Content-Type: application/alto-endpointcostparams+json
  Accept: application/alto-endpointcost+json,application/alto-error+json

    {
      "cost-type" { "cost-mode":  "numerical",
      "cost-metric":  "maxresbw"},
      "endpoints":  {
        "srcs": [ "ipv4 : 192.0.2.2" ],
        "dsts": [
          "ipv4:192.0.2.89",
          "ipv4:198.51.100.34",
          "ipv6:2000::1:2345:6789:abcd"
        ]
      }
    }

   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
       "meta": {
              "cost-type": {
              "cost-mode": "numerical",
              "cost-metric": "maxresbw"
              }
       },
     " endpoint-cost-map": {
             "ipv4:192.0.2.2" {
             "ipv4:192.0.2.89" :    0,
             "ipv4:198.51.100.34": 2000,
             "ipv6:2000::1:2345:6789:abcd":  5000,
                               }
              }
   }

4.2.  Cost Metric: Link Residue Bandwidth

   Metric name:

      Residue Bandwidth

   Metric Description:

      To specify spatial the measurement
   interval and temporal residual bandwidth varies over time.  To handle this issue, an ALTO server
   may collect data on time periods covering the
      specified source previous and destination.  The value is calculated by
      subtracting tunnel reservations from Maximum Bandwidth (motivated
      from [RFC7810], Sec.4.5.). current
   time or only collect data on present time.  The spatial aggregation unit is
      specified in the query context (e.g., PID ALTO server may
   further aggregate these data to PID, or endpoint provide an abstract and unified view
   that can be more useful to applications.  To make the ALTO client
   better understand how to
      endpoint).

   Method use these performance data, the ALTO server
   may provide the client with the validity period of Measurement or Calculation:

      Residue Bandwidth is the Unidirectional Residue exposed metric
   values.

4.2.2.  Availability Considerations

   Applications value information relating to bandwidth availability
   whereas bandwidth related metrics can often be only measured
      between two directly connected IS-IS neighbors or OSPF neighbors,
      See section 4.5 of [RFC7810] for Measurement Method.

   Units at the
   link level.  This document specifies a set of Measurement: link-level bandwidth
   related values that may be exposed as such by an ALTO server.  The unit of measurement is byte per seconds.

   Measurement Point(s) with Potential Measurement Domain:

      See section 2.1, Data sources.

   Measurement Timing:

      See section 5 of [RFC7810] for Measurement Timing.

   Use and Applications:

      See section 3 for use
   server may also expose other metrics derived from their aggregation
   and application.

  Example 7: residbw value on source-destination having different levels of endpoint pairs

  POST/ endpointcost/lookup HTTP/1.1
  Host: alto.example.com
  Content-Length: TBA
  Content-Type: application/alto-endpointcostparams+json
  Accept: application/alto-endpointcost+json,application/alto-error+json

    {
     "cost-type": { "cost-mode":  "numerical",
     "cost-metric":  "residubw"},
     "endpoints":  {
       "srcs": [ "ipv4 : 192.0.2.2" ],
       "dsts": [
         "ipv4:192.0.2.89",
         "ipv4:198.51.100.34",
         "ipv6:2000::1:2345:6789:abcd"
       ]
     }
  }

   HTTP/1.1 200 OK
   Content-Length: TBA
   Content-Type: application/alto-endpointcost+json
   {
      "meta": {
             "cost-type" {
             "cost-mode": "numerical",
             "cost-metric": "residbw"
           }
       },
   "endpoint-cost-map" {
            "ipv4:192.0.2.2" {
            "ipv4:192.0.2.89" :    0,
            "ipv4:198.51.100.34": 2000,
            "ipv6:2000::1:2345:6789:abcd":  5000,
                          }
           }
   } granularity, e.g., link
   endpoints or session endpoints.  The metric specifications may also
   expose the utilized aggregation laws.

5.  Security Considerations

   The properties defined in this document present no security
   considerations beyond those in Section 15 of the base ALTO
   specification [RFC7285].

   However concerns addressed in Sections "15.1 Authenticity and
   Integrity of ALTO Information", "15.2 Potential Undesirable Guidance
   from Authenticated ALTO Information" and "15.3 Confidentiality of
   ALTO Information" remain of utmost importance.  Indeed, TE
   performance is a highly sensitive ISP information, therefore, sharing
   TE metric values in numerical mode requires full mutual confidence
   between the entities managing the ALTO Server and Client.  Numerical
   TE performance information will most likely be distributed by ALTO
   Servers to Clients under strict and formal mutual trust agreements.

   On the other hand, ALTO Clients must be cognizant on the risks
   attached to such information that they would have acquired outside
   formal conditions of mutual trust.

6.  IANA Considerations

   IANA has created and now maintains the "ALTO Cost Metric Registry",
   listed in Section 14.2, Table 3 of [RFC7285].  This registry is
   located at <http://www.iana.org/assignments/alto-protocol/alto-
   protocol.xhtml#cost-metrics>.  This document requests to add the
   following entries to "ALTO Cost Meric Metric Registry".

+----------+------------+----------------------------------------------+
|Namespace | Property

   +------------+--------------------+
   | Reference Identifier |
+----------+------------+----------------------------------------------+ Intended Semantics |
   +------------+--------------------+
   | owdelay    | [thisdraft] Section 3,[RFC2679] See Section 3.6  | 2.1    |
   | rtt        | [thisdraft] See Section 4,[RFC2681],Section 2.6  | 2.2    |
   | pdv        | [thisdraft] See Section 5,[RFC3393],Section 2.6  | 2.3    |
   | hopcount   | [thisdraft] See Section 6,[RFC7285]              | 2.4    |
   | pktloss    | [thisdraft] See Section 7,[RFC7680],Section 2.6  | 2.5    |
   | throughput | [thisdraft],[RFC6349],Section3.3             | See Section 2.6    |
   | maxresbw   | [thisdraft] See Section 8.1,[RFC5305],Section 3.5| 3.1    |
   | residbw residuebw  | [thisdraft] See Section 8.2,[RFC7810],Section 4.5|
+----------+------------+----------------------------------------------+ 3.2    |
   +------------+--------------------+

7.  Acknowledgments

   The authors of this document would also like to thank Brian
   Trammell,Haizhou Du,Kai Gao,Lili Trammell,
   Haizhou Du, Kai Gao, Lili Liu, Li, Geng, Danny Alex Lachos Perez for
   the review reviews and comments.

8.  References

8.1.  Normative References

   [I-D.ietf-idr-te-pm-bgp]
              Ginsberg, L., Previdi, S., Wu, Q., Tantsura, J., and C.
              Filsfils, "BGP-LS Advertisement of IGP Traffic Engineering
              Performance Metric Extensions", draft-ietf-idr-te-pm-
              bgp-14
              bgp-18 (work in progress), October December 2018.

   [I-D.ietf-ippm-initial-registry]
              Morton, A., Bagnulo, M., Eardley, P., and K. D'Souza,
              "Initial Performance Metric Metrics Registry Entries", draft-ietf-
              ippm-initial-registry-08 draft-
              ietf-ippm-initial-registry-11 (work in progress), October 2018. March
              2019.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", March 1997.

   [RFC2679]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Delay Metric for IPPM", RFC 2679, DOI 10.17487/RFC2679,
              September 1999, <https://www.rfc-editor.org/info/rfc2679>.

   [RFC2681]  Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
              Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681,
              September 1999, <https://www.rfc-editor.org/info/rfc2681>.

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI
              10.17487/RFC3393, November 2002,
              <https://www.rfc-editor.org/info/rfc3393>. <https://www.rfc-
              editor.org/info/rfc3393>.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, DOI
              10.17487/RFC4627, July 2006,
              <https://www.rfc-editor.org/info/rfc4627>. <https://www.rfc-
              editor.org/info/rfc4627>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, 10.17487/
              RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>. <https://www.rfc-editor.org/info/
              rfc5234>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC6349]  Constantine, B., Forget, G., Geib, R., and R. Schrage,
              "Framework for TCP Throughput Testing", RFC 6349, DOI
              10.17487/RFC6349, August 2011,
              <https://www.rfc-editor.org/info/rfc6349>. <https://www.rfc-
              editor.org/info/rfc6349>.

   [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>.

   [RFC7471]  Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
              Previdi, "OSPF Traffic Engineering (TE) Metric
              Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
              <https://www.rfc-editor.org/info/rfc7471>.

   [RFC7679]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Delay Metric for IP Performance Metrics
              (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
              2016, <https://www.rfc-editor.org/info/rfc7679>.

   [RFC7680]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Loss Metric for IP Performance Metrics
              (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
              2016, <https://www.rfc-editor.org/info/rfc7680>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>. <https://www.rfc-
              editor.org/info/rfc7752>.

   [RFC7810]  Previdi, S., Ed., Giacalone, S., Ward, D., Drake, J., and
              Q. Wu, "IS-IS Traffic Engineering (TE) Metric Extensions",
              RFC 7810, DOI 10.17487/RFC7810, May 2016,
              <https://www.rfc-editor.org/info/rfc7810>.

8.2.  Informative References

   [RFC6390]  Clark, A. and B. Claise, "Framework for Performance Metric
              Development", RFC 6390, July 2011.

   [RFC7971]  Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and
              S. Previdi, "Application-Layer Traffic Optimization (ALTO)
              Deployment Considerations", RFC 7971, DOI 10.17487/RFC7971, 10.17487/
              RFC7971, October 2016,
              <https://www.rfc-editor.org/info/rfc7971>. <https://www.rfc-editor.org/info/
              rfc7971>.

Authors' Addresses

   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: bill.wu@huawei.com
   Y. Richard Yang
   Yale University
   51 Prospect St
   New Haven, CT  06520
   USA

   Email: yry@cs.yale.edu

   Young Lee
   Huawei
   1700 Alma Drive, Suite 500
   Plano, TX  75075
   USA

   Email: leeyoung@huawei.com

   Dhruv Dhody
   Huawei
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   Email: dhruv.ietf@gmail.com

   Sabine Randriamasy
   Nokia Bell Labs
   Route de Villejust
   Nozay  91460
   FRANCE

   Email: sabine.randriamasy@nokia-bell-labs.com