



bmwg                                                              K. Yao
Internet-Draft                                                    P. Liu
Intended status: Informational                              China Mobile
Expires: 26 November 2026                                        G. Zeng
                                                                  Huawei
                                                                   X. Yi
                                                            China Unicom
                                                                Q. Xiong
                                                                     ZTE
                                                              M.-N. Tran
                                                                    ETRI
                                                             25 May 2026


     Benchmarking Methodology for Computing-aware Traffic Steering
                         draft-yl-bmwg-cats-04

Abstract

   Computing-aware traffic steering (CATS) is a traffic engineering
   approach for steering service requests towards appropriate service
   instances based on the awareness of both computing and network
   information.  This document proposes benchmarking methodologies for
   CATS.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 26 November 2026.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





Yao, et al.             Expires 26 November 2026                [Page 1]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   3
   3.  Test Methodology  . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Test Setup  . . . . . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  Test Setup - Centralized Model  . . . . . . . . . . .   4
       3.1.2.  Test Setup - Distributed Model  . . . . . . . . . . .   6
       3.1.3.  Test Setup - Hybrid Model . . . . . . . . . . . . . .   7
     3.2.  Control Plane and Forwarding Plane Support  . . . . . . .  10
     3.3.  Topology  . . . . . . . . . . . . . . . . . . . . . . . .  10
     3.4.  Device Configuration  . . . . . . . . . . . . . . . . . .  10
   4.  Reporting Format  . . . . . . . . . . . . . . . . . . . . . .  11
   5.  Benchmarking Tests  . . . . . . . . . . . . . . . . . . . . .  13
     5.1.  CATS Metrics Collection and Distribution  . . . . . . . .  13
     5.2.  Session continuity  . . . . . . . . . . . . . . . . . . .  14
     5.3.  End-to-end Service Latency  . . . . . . . . . . . . . . .  15
     5.4.  System Utilization  . . . . . . . . . . . . . . . . . . .  15
     5.5.  Load Balancing Variance . . . . . . . . . . . . . . . . .  16
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  18
   Appendix A.  Aggregation and Normalization Functions  . . . . . .  18
     A.1.  Time-scale Aggregation  . . . . . . . . . . . . . . . . .  18
     A.2.  Spatial Aggregation . . . . . . . . . . . . . . . . . . .  19
     A.3.  Cross-category Aggregation  . . . . . . . . . . . . . . .  19
     A.4.  Normalization . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20











Yao, et al.             Expires 26 November 2026                [Page 2]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


1.  Introduction

   Computing-aware traffic Steering(CATS) is a traffic engineering
   approach considering both computing and network metrics, in order to
   select appropriate service instances.  Some of the latency-sensitive,
   throughput-sensitive applications or compute-intensive applications
   need CATS to guarantee effective instance selection, which are
   mentioned in [I-D.ietf-cats-usecases-requirements].  Considering
   there are many computing and network metrics that can be selected for
   traffic steering, as proposed in [I-D.ietf-cats-metric-definition],
   some benchmarking test methods are required to validate the
   effectiveness of different CATS metrics.  Besides, there are also
   different deployment models as described in the CATS framework
   [I-D.ietf-cats-framework], i.e. the distributed model, the
   centralized model and the hybrid model, and there are also multiple
   objectives for instance selection, for example, instance with lowest
   end-to-end latency or the highest system utilization.  The
   benchmarking methodology proposed in this document is essential for
   guiding CATS implementation.

2.  Definition of Terms

   This document uses the following terms defined in
   [I-D.ietf-cats-framework]:

   *  Computing-aware Traffic Steering (CATS)

   *  CATS Path Selector (C-PS)

   *  CATS-Forwarder

   *  CATS Service Metric Agent (C-SMA)

   *  CATS Network Metric Agent (C-NMA)

3.  Test Methodology

3.1.  Test Setup

   The test setup in general is compliant with [RFC2544].  As is
   mentioned in the introduction, there are basically three models for
   CATS deployment.  The centralized model, the distributed model, and
   the hybrid model.

   The difference primarily sits in how CATS metrics are collected and
   distributed into the network and accordingly, where the CATS path
   selector(C-PS) is placed to make decisions, as is defined in
   [I-D.ietf-cats-framework].



Yao, et al.             Expires 26 November 2026                [Page 3]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


3.1.1.  Test Setup - Centralized Model

   Figure 1 shows the test setup of the centralized model to implement
   CATS.  The centralized test setup is similar to the Software Defined
   Networking(SDN) standalone mode test setup defined in [RFC8456].  The
   DUT locates at the same place with the SDN controller.  In the
   centralized model, SDN controller takes the role of the decision
   making for instance selection as well as traffic steering.  The
   application plane test emulator is connected with the forwarding
   plane test emulator via interface 2 (I2).  The SDN controller is
   connected to Edge server manager via interface 4 (I4).  The interface
   (I1) of the SDN controller is connected with the forwarding plane.
   Service request is sent from application to the ingress CATS-
   Forwarder through I2.  CATS metrics are collected from Edge server
   manager via I4.  The traffic steering policies are configured through
   I1.

   In the forwarding plane, CATS-Forwarder 1 serves as the ingress node
   and is connected with the host which is an application plane
   emulator.  CATS-Forwarder 2 and CATS-Forwarder 3 serve as the egress
   nodes and are connected with two edge servers respectively.  Both of
   the edge servers are connected with edge server manager via I3.  I3
   is an internal interface for CATS metrics collection within edge
   sites.

   To accommodate the CATS framework, the C-PS is placed at the SDN
   controller.  The C-SMA is placed at the edge server manager.  C-NMAs
   are placed at all CATS-Forwarders.























Yao, et al.             Expires 26 November 2026                [Page 4]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


         +-----------------------------------------------+
         |       Application-Plane Test Emulator         |
         |                                               |
         |   +-----------------+      +-------------+    |
         |   |   Application   |      |   Service   |    |
         |   +-----------------+      +-------------+    |
         |                                               |
         +-+(I2)-----------------------------------------+
           |
           |
           |   +-------------------------------+    +-------------+
           |   |       +----------------+      |    |             |
           |   |       | SDN Controller |      |    | Edge Server |
           |   |       |     (C-PS)     |      |----|   Manager   |
           |   |       +----------------+      | I4 |   (C-SMA)   |
           |   |    Device Under Test (DUT)    |    |             |
           |   +-------------------------------+    +--------+----+
           |             |                                   |
           |             |                                   |
         +-+------------+(I1)--------------------------+     |
         |                                             |     |
         |        +----------------+                   |     |
         |        |CATS-Forwarder 1|                   |     |
         |        |     (C-NMA)    |                   |     | I3
         |        +----------------+                   |     |
         |          /            \                     |     |
         |         /              \                    |     |
         |     l0 /                \ ln                |     |
         |       /                  \                  |     |
         |  +----------------+  +----------------+     |     |
         |  |CATS-Forwarder 2|  |CATS-Forwarder 3|     |     |
         |  |     (C-NMA)    |..|     (C-NMA)    |     |     |
         |  +----------------+  +----------------+     |     |
         |          |                |                 |     |
         |    +------------+  +------------+           |     |
         |    |   Edge     |  |   Edge     |           |     |
         |    |  Server 1  |  |  Server 2  |           |     |
         |    |   (ES1)    |  |   (ES2)    |           |     |
         |    +------------+  +------------+           |     |
         |          |               |                  |     |
         |          +---------------+------------------------+
         |     Forwarding-Plane Test Emulator          |
         +---------------------------------------------+

                      Figure 1: Centralized Test Setup






Yao, et al.             Expires 26 November 2026                [Page 5]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


3.1.2.  Test Setup - Distributed Model

   Figure 2 shows the test setup of the distributed model to implement
   CATS.  In the distributed test setup, The DUT is the group of CATS-
   Forwarders, since the decision maker is the CATS ingress node, namely
   CATS-Forwarder 1.  CATS egress nodes, CATS-Forwarder 2 and CATS-
   Forwarder 3, take the role of collecting CATS metrics from edge
   servers and distribute these metrics towards other CATS-Forwarders.
   Service emulators from application plane is connected with the
   control-plane and forwarding-plane test emulator through the
   interface 1.

   To accommodate the CATS framework, the C-PS is placed at the ingress
   CATS-Forwarder 1.  The C-NMAs and C-SMAs are placed at all egress
   CATS-Forwarders (CATS-Forwarder 2 and 3).




































Yao, et al.             Expires 26 November 2026                [Page 6]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


         +---------------------------------------------+
         |       Application-Plane Test Emulator       |
         |                                             |
         |   +-----------------+      +-------------+  |
         |   |   Application   |      |   Service   |  |
         |   +-----------------+      +-------------+  |
         |                                             |
         +---------------+-----------------------------+
                         |
                         |
         +---------------+(I1)---------------------------+
         |                                               |
         |   +----------------------------------------+  |
         |   |        +----------------+              |  |
         |   |        |CATS-Forwarder 1|              |  |
         |   |        |     (C-PS)     |              |  |
         |   |        +----------------+              |  |
         |   |          /            \                |  |
         |   |         /              \               |  |
         |   |     l0 /                \ ln           |  |
         |   |       /                  \             |  |
         |   | +----------------+  +----------------+ |  |
         |   | |CATS-Forwarder 2|  |CATS-Forwarder 3| |  |
         |   | |(C-NMA & C-SMA) |..|(C-NMA & C-SMA) | |  |
         |   | +----------------+  +----------------+ |  |
         |   |      Device Under Test (DUT)           |  |
         |   +----------------------------------------+  |
         |              |                |               |
         |      +-------------+  +-------------+         |
         |      |Edge Server 1|  |Edge Server 2|         |
         |      |    (ES1)    |  |    (ES2)    |         |
         |      +-------------+  +-------------+         |
         |           Control-Plane and                   |
         |      Forwarding-Plane Test Emulator           |
         +-----------------------------------------------+

                      Figure 2: Distributed Test Setup

3.1.3.  Test Setup - Hybrid Model

   Figure 3 shows the test setup of the hybrid model to implement CATS.
   In hybrid model, some stable CATS metrics are distributed among
   involved network devices (i.e., CATS-Forwarders), while other
   frequent changing CATS metrics may be collected by a centralized SDN
   controller.  At the mean time, Service scheduling function can be
   performed by a SDN controller and/or the ingress CATS-Forwarder.  The
   entire or partial C-PS function may be implemented in the centralized
   control plane, depending on the specific implementation and



Yao, et al.             Expires 26 November 2026                [Page 7]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


   deployment.

   To accommodate the CATS framework, the C-PSs are placed at the SDN
   controller and the ingress CATS-Forwarder 1.  The C-SMAs are placed
   at the edge server manager and all egress CATS-Forwarders, The C-NMAs
   are placed at all egress CATS-Forwarders (CATS-Forwarder 2 and 3)
   too.












































Yao, et al.             Expires 26 November 2026                [Page 8]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


         +-----------------------------------------------+
         |       Application-Plane Test Emulator         |
         |                                               |
         |   +-----------------+      +-------------+    |
         |   |   Application   |      |   Service   |    |
         |   +-----------------+      +-------------+    |
         |                                               |
         +-+(I2)-----------------------------------------+
           |
           |
           |   +-------------------------------+    +-------------+
           |   |       +----------------+      |    |             |
           |   |       | SDN Controller |      |    | Edge Server |
           |   |       |     (C-PS)     |      |----|   Manager   |
           |   |       +----------------+      | I4 |   (C-SMA)   |
           |   |    Device Under Test (DUT)    |    |             |
           |   +-------------------------------+    +--------+----+
           |             |                                   |
           |             |                                   |
         +-+------------+(I1)--------------------------+     |
         |                                             |     |
         |        +----------------+                   |     |
         |        |CATS-Forwarder 1|                   |     |
         |        |     (C-PS)     |                   |     | I3
         |        +----------------+                   |     |
         |          /            \                     |     |
         |         /              \                    |     |
         |     l0 /                \ ln                |     |
         |       /                  \                  |     |
         |  +----------------+  +----------------+     |     |
         |  |CATS-Forwarder 2|  |CATS-Forwarder 3|     |     |
         |  |(C-NMA & C-SMA) |..|(C-NMA & C-SMA) |     |     |
         |  +----------------+  +----------------+     |     |
         |          |                |                 |     |
         |    +------------+  +------------+           |     |
         |    |   Edge     |  |   Edge     |           |     |
         |    |  Server 1  |  |  Server 2  |           |     |
         |    |   (ES1)    |  |   (ES2)    |           |     |
         |    +------------+  +------------+           |     |
         |          |               |                  |     |
         |          +---------------+------------------------+
         |     Forwarding-Plane Test Emulator          |
         +---------------------------------------------+

                        Figure 3: Hybrid Test Setup






Yao, et al.             Expires 26 November 2026                [Page 9]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


3.2.  Control Plane and Forwarding Plane Support

   In the centralized model, Both of the control plane and forwarding
   plane follow Segment Routing pattern, i.e. SRv6[RFC8986].  The SDN
   controller configure SRv6 policies based on the awareness of CATS
   metrics and traffic is steered through SRv6 tunnels built between
   CATS ingress nodes and CATS egress nodes.  The collection of CATS
   metrics in control plane is through Restful API or similar signalling
   protocols built between the SDN controller and the edge server
   manager.

   In the distributed model, in terms of the control plane,
   EBGP[RFC4271] is established between CATS egress nodes and edge
   servers.  IBGP[RFC4271] is established between CATS egress nodes with
   CATS ingress nodes.  BGP is chosen to distribute CATS metrics in
   network domain, from edge servers to CATS ingress node.  Carrying
   CATS metrics is implemented through the extension of BGP, and
   [I-D.ietf-idr-5g-edge-service-metadata] provides some examples by
   leveraging sub-TLVs extensions.

   In the hybrid model, the metric distribution follows the control
   plane settings in both centralized and distributed model, according
   to the actual choices in what metrics are required to be distributed
   centrally or distributedly.

   In terms of the forwarding plane, SRv6 tunnels are enabled between
   CATS ingress nodes with CATS egress nodes.

   Service flows are routed towards service instances by following
   anycast IP addresses in all of the models.

3.3.  Topology

   In terms of all of the approaches to test CATS performance in
   laboratory environments, implementors consider only single domain
   realization, that is all CATS-Forwarders are within the same AS.
   There is no further special requirement for specific topologies.

3.4.  Device Configuration

   Before implementation, there are some pre-configurations need to be
   settled.

   ** Application plane Setup

   Application plane functionalities must be setup in edge servers
   before the implementation, and hosts that send service requests must
   also be setup.



Yao, et al.             Expires 26 November 2026               [Page 10]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


   ** CATS Metrics Collector Setup

   In the centralized model and the hybrid model, the CATS metrics
   collector need to be first setup in the edge server manager.  A
   typical example of the collector can be the monitoring components of
   Kubernetes.  It can periodically collect different levels of CATS
   metrics.  Then the connecton between the edge server manager and the
   SDN controller must be established, one example is to set restful API
   or ALTO protocol for CATS metrics publication and subscription.

   In the distributed model and the hybrid model, the CATS metrics
   collector need to be setup in each edge site.  In this benchmark
   test, the collector is setup in each edge server which is directly
   connected with a CATS egress node.  Implementors can use plugin
   software to collect CATS metrics.  Then each edge server must set BGP
   peer with the CATS egress node that's directly connected.  In each
   edge server, a BGP speaker is setup.

   ** Control Plane and Fordwarding Plane functionality Setup

   In the centralized model and the hybrid model, the SDN controller
   need to be pre-configured and the interface between the SDN
   controller and CATS-Forwarders must be tested to validate if control
   plane policies can be correctly downloaded and it metrics from
   network side can be correctly uploaded.  In the distributed model and
   the hybrid model, the control plane setup is the iBGP connections
   between CATS-Forwarders.  For both models. the forwarding plane
   functions, SRv6 tunnels must be pre-established and tested.

4.  Reporting Format

   CATS benchmarking tests focus on data that can be measured and
   controllable.

   *  Control plane configurations:

      -  SDN controller types and versions;

      -  northbound and southbound protocols.

   *  Forwarding plane configurations:

      -  forwarding plane protocols (e.g., SRv6);

      -  the number of CATS-Forwarders;

      -  the number of edge servers;




Yao, et al.             Expires 26 November 2026               [Page 11]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


      -  the number of links;

      -  edge server types, versions.

   *  Application plane configurations:

      -  Traffic types and configurations.

   *  CATS Metrics: Each test must clearly state what CATS metrics it
      use for traffic steering, according to the CATS metrics definition
      in [I-D.ietf-cats-metric-definition].

      -  For Level 0 metrics, benchmarking tests must declare metric
         types, units, statistics(e.g, mean, max, min), format, and
         metric sources(e.g, nominal, estimation, aggregation).

      -  For Level 1 metrics, benchmarking tests must declare metric
         types, statistics, units, format, aggregation functions, and
         metric sources.

      -  For the Level 2 metric, benchmarking tests must declare metric
         type, normalization functions, and metric source.

      For all metric levels, benchmarking tests must report the
      Measurement_Window parameter used for metric collection.

   *Detailed normalization functions and aggregation functions are
   listed in appendix A.*

   The recommended metric levels are listed in Figure 4 for the
   benchmark tests that are described in Section 5:




















Yao, et al.             Expires 26 November 2026               [Page 12]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


     +----------------+--------------------------+---------------------+
     | Test Objective | Recommended Metric Level | Example Metric_Type |
     +----------------+--------------------------+---------------------+
     | CATS Metrics   |                          | compute_CPU_util or |
     | Collection and |    All Metric Levels     | level1_composed  or |
     | Distribution   |                          | level2_global       |
     +----------------+--------------------------+---------------------+
     | Session        |      Level 1 or          | level1_composed  or |
     | Continuity     |      Level 2             | level2_global       |
     +----------------+--------------------------+---------------------+
     | End-to-end     |      Level 1 or          | level1_composed  or |
     | Service Latency|      Level 2             | level2_global       |
     +----------------+--------------------------+---------------------+
     | System         |      Level 1             | level1_computing    |
     | Utilization    |                          |                     |
     +----------------+--------------------------+---------------------+
     | Load Balancing |      Level 1 or          | level1_computing or |
     | Variance       |      Level 2             | level2_global       |
     +----------------+--------------------------+---------------------+

       Figure 4: Mapping between Benchmarking Tests and Metric Levels

5.  Benchmarking Tests

5.1.  CATS Metrics Collection and Distribution

   *  Objective: To determine that CATS metrics can be correctly
      collected and distributed to the DUTs which are the SDN controller
      in the centralized model and the CATS ingress node in the
      distributed model, as anticipated within a pre-defined time
      interval for CATS metrics update.

   *  Procedure:

   In the centralized model and the hybrid model, the edge server
   manager periodically grasp CATS metrics from every edge server that
   can provide CATS service.  Then it passes the information to the SDN
   controller through publish-subscription methods.  Implementors then
   should log into the SDN controller to check if it can receive the
   CATS metrics from the edge server manager.

   In the distributed model and the hybrid model, the collectors within
   each edge server periodically grasp the CATS metrics of the edge
   server.  Then it distributes the metrics to the CATS egress node it
   directly connected.  Then Each CATS egress node further distributes
   the metrics to the CATS ingress node.  Implementors then log into the
   CATS ingress node to check if metrics from all edge servers have been
   received.



Yao, et al.             Expires 26 November 2026               [Page 13]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


   For all of these approaches, to test whether metrics can be received
   within the pre-defined time interval, implementors could compare the
   timestamp when receiving the current metric and the timestamp when
   the last metric arrives from the logs.  If the time difference is
   exactly equal to the pre-defined metric update time interval, then
   CATS metrics collection is correct.

   *  Expected results:

   ** All CATS metrics are correctly received without loss or error.

   ** The interval between consecutive metric updates matches the
   predefined value.

5.2.  Session continuity

   *  Objective: To determine that traffic can be correctly steered to
      the selected service instances and TCP sessions are maintained for
      specific service flows.

   *  Procedure: Enable several hosts to send service requests.  In
      distributed model, log into the CATS ingress node to check the
      forwarding table that route entries have been created for service
      instances.  Implementors can see that a specific packet which hits
      the session table, is matched to a target service intance.  Then
      manually increasing the load of the target edge server.  From the
      host side, one can see that service is going normally, while in
      the interface of the CATS-Forwarder, one can see that the previous
      session table aging successfully which means CATS has steer the
      service traffic to another service instance.

   In the centralized model and the hybrid model, implementors log into
   the management interface of the SDN controller and can check routes
   and sessions.

   *  Expected results:

   ** Traffic is correctly forwarded to the selected edge server without
   blackholing.

   ** Session entries are dynamically created and properly aged.

   ** When the target server is overloaded, traffic is smoothly switched
   to another instance.

   ** No session drop or service interruption occurs during steering.





Yao, et al.             Expires 26 November 2026               [Page 14]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


5.3.  End-to-end Service Latency

   *  Objective: To determine that CATS works properly under the pre-
      defined test condition and prove its effectiveness in service end-
      to-end latency guarantee.

   *  Procedure: Pre-define the CATS metrics distribution time to be T_1
      seconds.  Enable a host to send service requests.  In distributed
      model, log into the CATS ingress node to check if route entries
      have been successfully created.  Suppose the current selected edge
      server is ES1.  Then manually increase the load of ES1, and check
      the CATS ingress node again.  The selected instance has been
      changed to ES2.  CATS works properly.  Then print the logs of the
      ingress CATS-Forwarder to check the time it updates the route
      entries.  The time difference delta_T between when the new route
      entry first appears and when the previous route entry last appears
      should equals to T_1.  Then check if service SLA can be satisfied.

   In the centralized model and the hybrid model, implementors log into
   the management interface of the SDN controller and can check routes
   and sessions.

   *  Expected results:

   ** C-PS updates routing entries within delta_T, which is
   approximately equal to T1.

   ** End-to-end latency remains within the predefined SLA threshold.

   ** Latency after steering is not higher than before steering.

   ** Service performance is stable during path switching.

5.4.  System Utilization

   *  Objective: To determine that CATS can have better load balancing
      effect at server side than simple network load balancing
      mechanism, for example, Equal cost multi-path routing (ECMP).

   *  Procedure: Enable several hosts to send service requests and
      enable ECMP at network side.  Then measure the bias of the CPU
      utilization among different edge servers in time duration
      delta_T_2.  Stop services.  Then enable the same number of service
      requests and enable CATS at network side(the distributed model,
      the centralized model, and the hybrid model are tested
      separately.).  Measure the bias of the CPU utilization among the
      same edge servers in time duration delta_T_2.  Compare the bias
      value from two test setup.



Yao, et al.             Expires 26 November 2026               [Page 15]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


   *  Expected results:

   ** CATS reduces CPU utilization bias compared to ECMP, and edge
   server resources are used more evenly.

   ** No server is overloaded while others are underutilized.

   ** Overall system resource utilization is improved.

5.5.  Load Balancing Variance

   *  Objective: To test the load balancing variance under different
      path selection algorithms, which could evaluate the traffic
      steering effectiveness of these algorithms.  Low variance value
      means the algorithm performs better for traffic steering.
      Algorithms that are compared include ECMP, global-min, and
      Proportional-Integral-Derivative (PID).

   *  Procedure: Three different path selection algorithm are tested
      one-by-one.  In distributed model, pre-configure the control plane
      function C-PS in the ingress CATS-Forwarder, while in the
      centralized and hybrid model, the path selection function is
      configured in the SDN controller.  For each test round,
      implementors initiate the same number of service flows to multiple
      service edge sites.  For example, the number of service flows are
      set to M, while the number of service edge sites is N.
      Implementors need to record the number of service flows at each
      site, and calculate the load balancing variance, according to the
      following equations:

   ** n_avg = (n_s1 + n_s2 + .. + n_sN) / N **

   ** var_alg = sqrt( sum_{i=1 to N} (n_si - n_avg)^2 / N ) **

   Where 'n_s1', 'n_s2', ..., 'n_sN' refer to the number of service
   flows that are steered to the corresponding edge site, while 'n_avg'
   refers to the average number of service flows per site. 'var_alg' is
   the standard deviation of service flows across all N edge sites,
   which is used to evaluate the load balancing effectiveness of each
   algorithm.  A lower standard deviation indicates better load
   balancing, as traffic is more evenly distributed among edge sites.

   *  Expected Results:

   ** CATS algorithms (global-min, PID) show lower variance than ECMP.

   ** Traffic is distributed evenly without flow loss or service
   degradation.



Yao, et al.             Expires 26 November 2026               [Page 16]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


6.  Security Considerations

   The benchmarking characterization described in this document is
   constrained to a controlled environment (as a laboratory) and
   includes controlled stimuli.  The network under benchmarking MUST NOT
   be connected to production networks.  Beyond these, there are no
   specific security considerations within the scope of this document.

7.  IANA Considerations

   This document has no IANA actions.

8.  Acknowledgements

9.  References

9.1.  Normative References

   [I-D.ietf-cats-framework]
              Li, C., Du, Z., Boucadair, M., Contreras, L. M., and J.
              Drake, "A Framework for Computing-Aware Traffic Steering
              (CATS)", Work in Progress, Internet-Draft, draft-ietf-
              cats-framework-24, 2 April 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-cats-
              framework-24>.

   [I-D.ietf-cats-metric-definition]
              Yao, K., Li, C., Contreras, L. M., Ros-Giralt, J., and G.
              Zeng, "CATS Metrics Definition", Work in Progress,
              Internet-Draft, draft-ietf-cats-metric-definition-08, 15
              May 2026, <https://datatracker.ietf.org/doc/html/draft-
              ietf-cats-metric-definition-08>.

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for
              Network Interconnect Devices", RFC 2544,
              DOI 10.17487/RFC2544, March 1999,
              <https://www.rfc-editor.org/rfc/rfc2544>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/rfc/rfc4271>.

   [RFC8456]  Bhuvaneswaran, V., Basil, A., Tassinari, M., Manral, V.,
              and S. Banks, "Benchmarking Methodology for Software-
              Defined Networking (SDN) Controller Performance",
              RFC 8456, DOI 10.17487/RFC8456, October 2018,
              <https://www.rfc-editor.org/rfc/rfc8456>.



Yao, et al.             Expires 26 November 2026               [Page 17]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


   [RFC8986]  Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
              D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
              (SRv6) Network Programming", RFC 8986,
              DOI 10.17487/RFC8986, February 2021,
              <https://www.rfc-editor.org/rfc/rfc8986>.

9.2.  Informative References

   [I-D.ietf-cats-usecases-requirements]
              Yao, K., Contreras, L. M., Shi, H., Zhang, S., and Q. An,
              "Computing-Aware Traffic Steering (CATS) Problem
              Statement, Use Cases, and Requirements", Work in Progress,
              Internet-Draft, draft-ietf-cats-usecases-requirements-14,
              2 February 2026, <https://datatracker.ietf.org/doc/html/
              draft-ietf-cats-usecases-requirements-14>.

   [I-D.ietf-idr-5g-edge-service-metadata]
              Dunbar, L., Majumdar, K., Li, C., Mishra, G. S., and Z.
              Du, "BGP Extension for 5G Edge Service Metadata", Work in
              Progress, Internet-Draft, draft-ietf-idr-5g-edge-service-
              metadata-32, 27 April 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-5g-
              edge-service-metadata-32>.

Appendix A.  Aggregation and Normalization Functions

   This appendix specifies the detailed aggregation functions
   (categorized by time-scale, spatial, and cross-category) and
   normalization functions for CATS metrics, aligned with
   [I-D.ietf-cats-metric-definition].

A.1.  Time-scale Aggregation

   Time-scale aggregation consolidates metric values over a specified
   time window to reflect temporal trends (e.g., average computing load
   over 1 minute).  The following functions are defined for CATS
   benchmarking:

   ** Time Average

   Time_Average = (Sample_1 + Sample_2 + ... + Sample_n) / n

   ** Time Maximum

   Time_Max = Maximum value of all samples in the time window

   ** Time Minimum




Yao, et al.             Expires 26 November 2026               [Page 18]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


   Time_Min = Minimum value of all samples in the time window

A.2.  Spatial Aggregation

   Spatial aggregation consolidates metric values across multiple
   compute entities (e.g., multiple edge servers) to reflect regional/
   global status.

   ** Spatial Sum

   Spatial_Sum = Entity_1_Value + Entity_2_Value + ... + Entity_m_Value

   ** Spatial Average

   Spatial_Average = (Entity_1_Value + Entity_2_Value + ... +
   Entity_m_Value) / m

   ** Spatial Median

   Spatial_Median = Middle value of sorted entity values

A.3.  Cross-category Aggregation

   Cross-category aggregation combines metrics from different categories
   (e.g., type 1: CPU load; type 2: GPU memory) to generate metrics with
   level up for CATS decision-making.  This documents adopts linear
   combination as the cross-category aggregation function.

   ** Linear Combination

   Linear_Combination = alpha * Metric_1 + beta * Metric_2 + ... (alpha
   + beta + ... = 1)

A.4.  Normalization

   Normalization scales CATS metrics to a uniform range (0-10) using
   min-max scaling, ensuring comparability while ensuring simplicity.
   The functions are defined as:

   ** Standard Normalization

   Normalized_Value = 10 * (Raw_Value - Min_Value) / (Max_Value -
   Min_Value)

   ** Inverse Normalization

   Inverse_Normalized_Value = 10 * (Max_Value - Raw_Value) / (Max_Value
   - Min_Value)



Yao, et al.             Expires 26 November 2026               [Page 19]

Internet-Draft      Benchmarking Methodology for CATS           May 2026


Authors' Addresses

   Kehan Yao
   China Mobile
   Email: yaokehan@chinamobile.com


   Peng Liu
   China Mobile
   Email: liupengyjy@chinamobile.com


   Guanming Zeng
   Huawei
   Email: zengguanming@huawei.com


   Xinxin Yi
   China Unicom
   Email: yixx3@chinaunicom.cn


   Quan Xiong
   ZTE
   Email: xiong.quan@zte.com.cn


   Minh-Ngoc Tran
   ETRI
   Email: mipearlska@etri.re.kr





















Yao, et al.             Expires 26 November 2026               [Page 20]
