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<rfc category="info" docName="draft-wang-cats-usecase-green-00"
     ipr="trust200902" submissionType="IETF">
  <front>
    <title abbrev="">A Use case for Green Computing-Aware Traffic
    Steering</title>

    <author fullname="Jing Wang" initials="J." surname="Wang">
      <organization>China Mobile</organization>

      <address>
        <postal>
          <street>No.32 XuanWuMen West Street</street>

          <city>Beijing</city>

          <code>100053</code>

          <country>China</country>
        </postal>

        <email>wangjingjc@chinamobile.com</email>
      </address>
    </author>

    <date day="21" month="October" year="2024"/>

    <workgroup>cats</workgroup>

    <abstract>
      <t>This draft describes a compute-aware use case for services with green
      energy requirements. This use case considers both network, computation
      and energy metrics when selecting a service instance.</t>
    </abstract>
  </front>

  <middle>
    <section anchor="introduction" title="Introduction">
      <t>As mobile edge computing networks sink computational tasks from cloud
      data centers to the edge of the network, tasks need to be processed by
      computational resources close to the user's end as mentioned in <xref
      target="I-D.ietf-cats-usecases-requirements"/>. Therefore, CATS is
      proposed. Reducing carbon emissions is a major challenge that needs to
      be faced in our time. The network is the main enabler to achieve the
      reduction of carbon emission.The introduction of computational dimension
      in CATS makes the previous energy saving by considering only the network
      dimension to be insufficient and hence green for CATS based on the
      association of network and computation is worth to be explored.</t>

      <t>Recently, the GREEN WG was formed. It is chartered to explore use
      cases, derive requirements, and provide solutions for identifying and
      characterizing energy efficiency metrics, methods related to energy
      consumption of network devices, and optimizing energy efficiency across
      the network. network. There are also a number of contributions that
      explore green networks, and the document <xref
      target="I-D.wang-cats-green-challenges"/> summarizes a number of
      challenges faced by cats considering green.</t>

      <t>This document provides a green cats use case.</t>
    </section>

    <section anchor="definition-of-terms" title="Definition of Terms">
      <t><list hangIndent="2" style="hanging">
          <t hangText="Computing-Aware Traffic Steering (CATS): ">Aiming at
          computing and network resource optimization by steering traffic to
          appropriate computing resources considering not only routing metric
          but also computing resource metric.</t>

          <t hangText="Service:">A monolithic functionality that is provided
          by an endpoint according to the specification for said service. A
          composite service can be built by orchestrating monolithic
          services.</t>

          <t hangText="Service instance:">Running environment (e.g., a node)
          that makes the functionality of a service available. One service can
          have several instances running at different network locations.</t>
        </list></t>
    </section>

    <section title="Use Case">
      <t>Geared towards green computing-aware traffics Steering, the green
      metrics include the energy consumption of network devices as well as the
      energy consumption of computing resources. The following describes how
      green metrics are distributed under both distributed and centralized
      models.</t>

      <section title="Distributed Model">
        <t><xref target="fig-cats-example-overlay"/> shows an example of how
        Green CATS metrics can be disseminated in the distributed model. In
        this way, green metrics are distributed among network devices directly
        using distributed protocols without interactions with a centralized
        control plane.</t>

        <figure anchor="fig-cats-example-overlay">
          <name>An Example of Green CATS Metric Dessimination in a Distributed
          Model</name>

          <artwork><![CDATA[
          Service CS-ID 1, contact instance CSCI-ID 1 <computing metrics, green metrics>
          Service CS-ID 1, contact instance CSCI-ID 2 <computing metrics, green metrics>

                 :<----------------------:
                 :                       :               +---------+
                 :                       :               |CS-ID 1  |
                 :                       :            +--|CSCI-ID 1|
                 :              +----------------+    |  +---------+
                 :              |    C-SMA       |----|   Service Site 2
                 :              +----------------+    |  +---------+
                 :              |CATS-Forwarder 2|    +--|CS-ID 1  |
                 :              +----------------+       |CSCI-ID 2|
 +--------+      :                        |              +---------+
 | Client |      :  Network +----------------------+
 +--------+      :  metrics | +-------+            |
      |          : :<---------| C-NMA |            |
      |          :  Green   | +-------+            |
      |          :  metrics |                      |
 +---------------------+    |                      |
 |CATS-Forwarder 1|C-PS|----|                      |
 +---------------------+    |       Underlay       |
                 :          |     Infrastructure   |     +---------+
                 :          |                      |     |CS-ID 1  |
                 :          +----------------------+ +---|CSCI-ID 3|
                 :                    |              |   +---------+
                 :          +----------------+  +-------+
                 :          |CATS-Forwarder 3|--| C-SMA | Service Site 3
                 :          +----------------+  +-------+
                 :                                :  |   +-------+
                 :                                :  +---|CS-ID 2|
                 :                                :      +-------+
                 :<-------------------------------:
          Service CS-ID 1, contact instance CSCI-ID 3 <computing metrics, green metrics>
          Service CS-ID 2, <computing metrics, green metrics>
]]></artwork>
        </figure>
      </section>

      <section title=" Centralized Model">
        <t>In <xref target="fig-cats-centralized"/>, network metrics,
        computing metrics, and green metrics can be distributed in a
        centralized way. Green metrics are collected by the centralized
        control plane, and then the centralized control plane calculates the
        forwarding path corresponding to the energy efficiency demand request
        and synchronizes with the Ingress CATS-Forwarder.</t>

        <t><figure anchor="fig-cats-centralized">
            <name>An Example of Green CATS Metric Distribution in a
            Centralized Model</name>

            <artwork><![CDATA[
                        Service CS-ID 1, instance CSCI-ID 1 <computing metrics, green metrics>
                        Service CS-ID 1, instance CSCI-ID 2 <computing metrics, green metrics>
                        Service CS-ID 1, instance CSCI-ID 3 <computing metrics, green metrics>
                        Service CS-ID 2, <metrics>

             :       +------+
             :<------| C-PS |<-----------------------------------+
             :       +------+ <------+              +---------+  |
             :          ^            |           +--|CS-ID 1  |  |
             :          |            |           |  |CSCI-ID 1|  |
             :          |   +----------------+   |  +---------+  |
             :          |   |    C-SMA       |---|Service Site 2 |
             :          |   +----------------+   |  +---------+  |
             :          |   |CATS-Forwarder 2|   +--|CS-ID 1  |  |
             :          |   +----------------+      |CSCI-ID 2|  |
 +--------+  :          |             |             +---------+  |
 | Client |  :  Network |   +----------------------+             |
 +--------+  :  metrics |   | +-------+            |             |
      |      :          +-----| C-NMA |            |      +-----+
      |      :  Green   |   | +-------+            |      |C-SMA|<-+
      |         metrics |   |                      |      +-----+  |         
 +----------------+ <---+   |                      |               |
 |CATS-Forwarder 1|---------|                      |          ^    |
 +----------------+         |       Underlay       |          |    |
             :              |     Infrastructure   |    +---------+|
             :              |                      |    |CS-ID 1  ||
             :              +----------------------+  +-|CSCI-ID 3||
             :                        |               | +---------+|
             :          +----------------+------------+            |
             :          |CATS-Forwarder 3|         Service Site 3  |
             :          +----------------+                         |
             :                        |       :      +-------+     |
             :                        +-------:------|CS-ID 2|-----+
             :                                :      +-------+
             :<-------------------------------:
      Service CS-ID 1, contact instance CSCI-ID 3
      Service CS-ID 2
]]></artwork>
          </figure></t>
      </section>
    </section>

    <section anchor="Conclusion" title="Conclusion">
      <t>This document gives a CATS use case related to green and further
      describes how green metrics can be distributed under both distributed
      and centralized models.</t>
    </section>

    <section anchor="security-considerations" title="Security Considerations">
      <t>TBD.</t>
    </section>

    <section anchor="iana-considerations" title="IANA Considerations">
      <t>TBD.</t>
    </section>
  </middle>

  <back>
    <references title="Informative References">
      <?rfc include="reference.I-D.ietf-cats-usecases-requirements"?>

      <?rfc include="reference.I-D.wang-cats-green-challenges"?>
    </references>
  </back>
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