



opsawg                                                            K. Yao
Internet-Draft                                              China Mobile
Intended status: Standards Track                         L. M. Contreras
Expires: 23 April 2026                                        Telefonica
                                                           J. Ros-Giralt
                                                   Qualcomm Europe, Inc.
                                                         20 October 2025


  Service Instance Deployment based on Integrated Network and Compute
                                Metrics
         draft-ymg-opsawg-service-deployment-with-alto-cats-00

Abstract

   The deployment of service instances across distributed interconnected
   edge-cloud environments can be optimized in terms of performance
   expectations and Service Level Objectives (SLOs) satisfaction when
   performed taken into account both network and compute metrics.  In
   order to do so, this document primarily concentrates on existing
   standardized mechanisms, namely ALTO and CATS, to facilitate such
   integration of metrics.  The ALTO protocol can be extended to expose
   compute metrics from a cloud manager to a network orchestrator or as
   part of the network and cost maps, enabling improved deployment of
   compute service instances based on joint awareness of both network
   and computing information.  This document proposes protocol
   extensions, workflows, and operational considerations for ALTO
   enhancements using CATS metrics.

Status of This Memo

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   This Internet-Draft will expire on 23 April 2026.






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Copyright Notice

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   document authors.  All rights reserved.

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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Workflows . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Request and Response  . . . . . . . . . . . . . . . . . .   3
     2.2.  Active Push . . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  Protocol Extention Examples . . . . . . . . . . . . . . .   7
   3.  Operational Considerations  . . . . . . . . . . . . . . . . .   9
     3.1.  Compute Instance Deployment Strategy  . . . . . . . . . .   9
     3.2.  Deployment Considerations of ALTO Client and Server . . .  10
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Applications such as artificial intelligence (AI) inference and cloud
   rendering require performance optimization based on joint awareness
   of both network and computing information.
   [I-D.rcr-opsawg-operational-compute-metrics] introduces the service
   lifecycle, including service deployment, service selection, and
   service assurance.  The discussion and documentation of the service
   selection problem are currently being undertaken by the Computing-
   Aware Traffic Steering (CATS) Working Group, while the service
   deployment problem still lacks a dedicated venue for resolution.
   This document primarily focuses on the service deployment problem and
   leverages the flexibility of ALTO protocol extensions to enable joint
   awareness of both network and computing information for improved
   compute service instance deployment.




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   [I-D.ietf-cats-metric-definition], adopted by the CATS Working Group,
   defines three metric levels for all CATS-related metrics from the
   computing domain (e.g., cloud).  These metrics are initially intended
   to support service instance selection for traffic steering, but they
   can also be exposed for compute service deployment.
   [I-D.contreras-alto-service-edge] introduces a method for using ALTO
   protocol extensions for service deployment, but it does not cover
   CATS metrics or their encodings.  This document provides
   supplementary information to [I-D.contreras-alto-service-edge],
   including protocol extensions for encoding CATS metrics, workflows,
   and operational considerations for compute service instance
   deployment.

2.  Workflows

   The main entities involved in this solution are the ALTO server and
   the ALTO client.

   *ALTO Server: Deployed in the cloud manager and network controller,
   it is responsible for collecting various CATS metrics.

   *ALTO Client: Located in the service orchestrator, it is responsible
   for requesting and receiving information from the ALTO server, and
   for formulating compute instance deployment strategies based on the
   collected data.

   There are two basic implementation schemes.  The interactions between
   the ALTO client and servers may vary depending on the chosen mode.

2.1.  Request and Response

   Figure 1 shows the workflow under request and response mode.

   The ALTO client in the service orchestrator within the network domain
   first requests computing domain information from the ALTO server
   located in the cloud manager, and then requests network domain
   information from the ALTO server in the network controller.














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   The ALTO server in the cloud manager collects CATS metrics, including
   various L0 metrics, calculates L1 and L2 metrics, determines and
   selects all or part of the metrics from L0, L1, and L2 to pass to the
   ALTO client, encapsulates the message, and sends the ALTO message to
   the ALTO client.  The basis for the ALTO server in the cloud manager
   to determine which level of computing metrics to send is the request
   information from the ALTO client.  The initial request from the ALTO
   client will clearly specify the requested level of CATS metrics (such
   as L2, L1, and/or L0), and for L1 and/or L0 metrics, it will specify
   whether to request all metrics at that level or specific ones (e.g.,
   only the "compute type" L1 metric for L1, or only CPU utilization for
   L0).

   The ALTO server in the network controller obtains network domain
   information (such as link bandwidth, latency, etc.), encapsulates all
   the obtained information in an ALTO message, and sends it to the ALTO
   client.

   The ALTO client sends confirmation messages to both ALTO servers.

   The ALTO client in the service orchestrator calculates the compute
   instance deployment method based on the obtained computing domain and
   network domain information, and then sends the deployment strategy
   information to the ALTO server in the cloud manager, which notifies
   the cloud manager to deploy the corresponding computing instances.


























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 +--------------+                         +--------------+                           +--------------+
 |  controller  |                         | orchestrator |                           |cloud manager |
 |  +--------+  |                         |  +--------+  |                           |  +--------+  |
 |  |  ALTO  |  |                         |  |  ALTO  |  |                           |  |  ALTO  |  |
 |  | server |  |                         |  | client |  |                           |  | server |  |
 |  +---+----+  |                         |  +----+---+  |                           |  +---+----+  |
 +------+-------+                         +-------+------+                           +------+-------+
        |                                         |        Request for computing metrics    |
        |                                         +----------------------------------------->
        |      Request for network metrics        |                                         |
        <-----------------------------------------+                                         |
        |                                         |                                  +------+------+
        |                                         |                                  |CATS metrics |
        |                                         |                                  | collection  |
        |                                         |                                  +------+------+
+-------+-------+                                 |                                         |
|network metrics|                                 |     send ALTO message with CATS metrics |
|  collection   |                                 <-----------------------------------------+
+-------+-------+                                 |                                         |
        |                                         |                  ack                    |
        |                                         +----------------------------------------->
        |  send ALTO message with network metrics |                                         |
        +----------------------------------------->                                         |
        |                 ack                     |                                         |
        +-----------------------------------------+                                         |
        |                              +----------+-------------+                           |
        |                              |Make deployment strategy|                           |
        |                              | based on metrics from  |                           |
        |                              |     both sides         |                           |
        |                              +----------+-------------+                           |
        |                                         |     instance deployment notification    |
        |                                         +---------------------------------------->|
        |                                         |                                         |

                   Figure 1: Request-Response Mode

2.2.  Active Push

   Figure 2 shows the workflow under active push mode.

   The ALTO client establishes Server-Sent Events(SSE) long connections
   with the ALTO server in the cloud manager and the ALTO server in the
   network controller respectively.  During connection maintenance, ALTO
   servers actively push ALTO messages to the ALTO client.







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   The ALTO server in the cloud manager obtains CATS metrics, including
   various L0 metrics, calculates L1 and L2 metrics, determines and
   selects all or part of the metrics from L0, L1, and L2 to pass to the
   ALTO client, encapsulates the message, and actively pushes the ALTO
   message containing the selected computing domain information.

   The ALTO server in the network controller obtains network domain
   information, encapsulates it in an ALTO message, and pushes it to the
   ALTO client.

   The ALTO client sends confirmation messages and periodic heartbeat
   messages to maintain connection status.  ALTO servers then reply with
   acknowledgment (ACK) messages if the connections are valid.

   The ALTO client formulates the compute instance deployment strategy
   based on the obtained information and sends the deployment strategy
   information.

   Note that in the active push mode, the ALTO server initially sends L2
   level computing metrics by default.  The ALTO client can carry
   requests for L1 and/or L0 level metrics (all or part) in the
   confirmation message, and the ALTO server will start pushing the
   requested metrics from the next cycle.




























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 +--------------+                         +--------------+                           +--------------+
 |  controller  |                         | orchestrator |                           |cloud manager |
 |  +--------+  |                         |  +--------+  |                           |  +--------+  |
 |  |  ALTO  |  |                         |  |  ALTO  |  |                           |  |  ALTO  |  |
 |  | server |  |                         |  | client |  |                           |  | server |  |
 |  +---+----+  |                         |  +----+---+  |                           |  +---+----+  |
 +------+-------+                         +-------+------+                           +------+-------+
        |                                         |              SSE connection             |
        |                                         <----------------------------------------->
        |           SSE connection                |                                         |
        <----------------------------------------->                                         |
        |                                         |                                  +------+------+
        |                                         |                                  |CATS metrics |
        |                                         |                                  | collection  |
        |                                         |                                  +------+------+
+-------+-------+                                 |                                         |
|network metrics|                                 |     push ALTO message with CATS metrics |
|  collection   |                                 <-----------------------------------------+
+-------+-------+                                 |                                         |
        |                                         |                  ack                    |
        |                                         +----------------------------------------->
        |  push ALTO message with network metrics |                                         |
        +----------------------------------------->         heartbeat message               |
        |                 ack                     +----------------------------------------->
        <-----------------------------------------+                  ack                    |
        |        heartbeat message                <-----------------------------------------+
        <-----------------------------------------+                                         |
        |                 ack                     |                                         |
        +----------------------------------------->                                         |
        |                              +----------+-------------+                           |
        |                              |make deployment strategy|                           |
        |                              | based on metrics from  |                           |
        |                              |     both sides         |                           |
        |                              +----------+-------------+                           |
        |                                         |     instance deployment notification    |
        |                                         +---------------------------------------->|
        |                                         |                                         |

                      Figure 2: Active Push Mode

2.3.  Protocol Extention Examples

   The three-layer metric information can be defined by extending the
   ALTO endpoint cost service in RFC 7285, through extending the "cost-
   type" field.

   Figure 3 shows the example in JSON format:




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   {
     "meta": {
       "cost-types": {
         "L2-metric": {
           "metric-type": "Fully normalized metric",
           "level": "L2",
           "cost-mode": "numerical",
           "cost-metric": "normalized-value"
         },
         "L1-metric": {
           "metric-type": "Compute metric",
           "level": "L1",
           "cost-mode": "numerical",
           "cost-metric": "normalized-value"
         },
         "L0-metric": {
           "metric-type": "CPU frequency",
           "level": "L0",
           "cost-mode": "numerical",
           "cost-metric": "GigaHertz"
         }
       }
     }
   }

                       Figure 3: cost-type extension

   Figure 4 describes the encapsulation of CATS metrics as well as site
   information based on the ALTO protocol extensions in JSON format:






















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   {
     "meta": {
       "dependent-vtags": [
         {
           "resource-id": "my-default-networkmap",
           "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e"
         }
       ]
     },
     "endpoint-properties": {
       "ipv4:192.0.2.34": {
         "Fully normalized metric": {
           "level": "L2",
           "value": 5
         }
       },
       "ipv4:203.0.113.56": {
         "Compute metric": {
           "level": "L1",
           "value": 3
         },
         "CPU frequency": {
           "level": "L0",
           "value": "2.2 GigaHertz"
         }
       }
     }
   }

                          Figure 4: alto encodings

   In the example above, the ALTO message carries metric information of
   two service endpoints.  The ALTO server can define and set the
   content to be sent, choosing to send all levels of metric information
   for the corresponding endpoint, or select one level of metrics or a
   specific metric within a level.

3.  Operational Considerations

3.1.  Compute Instance Deployment Strategy

   The ALTO client in the service orchestrator formulates various
   computing service instance deployment methods based on computing and
   network information.  The procedure of how to generate and deploy the
   strategy should also be considered.






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   Firstly, determine the availability for instance deployment.  The
   ALTO client must first verify whether a specific site is capable of
   hosting the service.  Therefore, supplementary procedures may be
   required at the beginning of both workflows described in the previous
   sections.  Upon receiving a service request, the ALTO client needs to
   notify the ALTO server in the cloud manager of the specific resources
   required for deployment (e.g., X CPU cores or Y GB of GPU memory).

   Secondly, determine the priority for instance deployment.  If the
   ALTO client receives Level 2 (L2) metrics, it may perform a direct
   summation.  If it receives Level 1 (L1) metrics, it may apply a
   weighted summation, for example:

   (Score of computing class L1 metric of a node from the cloud
   manager's ALTO server * weight1) + (Score of normalized network class
   L1 metric of a link from the network controller's ALTO server *
   weight2)

   If the ALTO client receives Level 0 (L0) metrics, the algorithm may
   involve applying a polynomial function over multiple metrics.  After
   computation, the ALTO client sorts the results to determine the
   priority of instance deployment, with higher scores indicating higher
   priority.

   Thirdly, determine remaining resources after instance deployment.
   Once the compute service node for deployment is selected, the ALTO
   server completes the instance deployment, calculates the remaining
   resource availability, and notifies the ALTO client.

3.2.  Deployment Considerations of ALTO Client and Server

   The ALTO server can be co-located with the network controller or
   cloud manager, or deployed separately.  Similarly, the ALTO client
   can be co-located with the service orchestrator or deployed
   separately.

   The three-level metric framework provides flexibility in information
   exposure, allowing adaptation to different scenarios where the
   computing and network domains may belong to the same or different
   service entities.

   Dynamic updates of metrics should be considered to ensure the
   timeliness and accuracy of information for effective deployment
   decisions.







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4.  Security Considerations

   This document does not introduce new security risks beyond those
   inherent in the ALTO protocol.  Security mechanisms specified in
   [RFC7285] and related ALTO extensions (such as access control in
   [RFC7971]) should be applied to protect sensitive computing and
   network information, especially when computing and network domains
   belong to different service entities.

5.  IANA Considerations

   This document has no IANA actions.

6.  Acknowledgements

7.  References

7.1.  Normative References

   [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/rfc/rfc7285>.

   [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, October 2016,
              <https://www.rfc-editor.org/rfc/rfc7971>.

7.2.  Informative References

   [I-D.contreras-alto-service-edge]
              Contreras, L. M., Randriamasy, S., Ros-Giralt, J., Perez,
              D. A. L., and C. E. Rothenberg, "Use of ALTO for
              Determining Service Edge", Work in Progress, Internet-
              Draft, draft-contreras-alto-service-edge-10, 13 October
              2023, <https://datatracker.ietf.org/doc/html/draft-
              contreras-alto-service-edge-10>.

   [I-D.ietf-cats-metric-definition]
              Yao, K., Li, C., Contreras, L. M., Ros-Giralt, J., and H.
              Shi, "CATS Metrics Definition", Work in Progress,
              Internet-Draft, draft-ietf-cats-metric-definition-04, 20
              October 2025, <https://datatracker.ietf.org/doc/html/
              draft-ietf-cats-metric-definition-04>.




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   [I-D.rcr-opsawg-operational-compute-metrics]
              Randriamasy, S., Contreras, L. M., Ros-Giralt, J., and R.
              Schott, "Joint Exposure of Network and Compute Information
              for Infrastructure-Aware Service Deployment", Work in
              Progress, Internet-Draft, draft-rcr-opsawg-operational-
              compute-metrics-08, 21 October 2024,
              <https://datatracker.ietf.org/doc/html/draft-rcr-opsawg-
              operational-compute-metrics-08>.

Authors' Addresses

   Kehan Yao
   China Mobile
   Email: yaokehan@chinamobile.com


   L. M. Contreras
   Telefonica
   Email: luismiguel.contrerasmurillo@telefonica.com


   Jordi Ros-Giralt
   Qualcomm Europe, Inc.
   Email: jros@qti.qualcomm.com



























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