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CATS based on Real Locator
draft-shi-cats-with-real-locator-01

Document Type Active Internet-Draft (individual)
Authors Hang Shi , Xia Chen , Zhenbin Li , Xinxin Yi , Kehan Yao
Last updated 2024-02-28
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draft-shi-cats-with-real-locator-01
Network Working Group                                             H. Shi
Internet-Draft                                                   X. Chen
Intended status: Informational                                     Z. Li
Expires: 1 September 2024                            Huawei Technologies
                                                                   X. Yi
                                                            China Unicom
                                                                  K. Yao
                                                            China Mobile
                                                        29 February 2024

                       CATS based on Real Locator
                  draft-shi-cats-with-real-locator-01

Abstract

   This document describes a solution framework that adheres to the CATS
   framework.  The solution uses anycast IP addresses as the CATS
   service identifier and real locator of the service contact instance
   as the CATS Instance Selection ID.

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 [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
   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 1 September 2024.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Solution Overview . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Realization of CATS Framework Components  . . . . . . . .   4
     3.2.  Realization of CATS Framework Workflow  . . . . . . . . .   5
       3.2.1.  Service Announcement  . . . . . . . . . . . . . . . .   5
       3.2.2.  Metrics Distribution  . . . . . . . . . . . . . . . .   5
       3.2.3.  Service Demand processing . . . . . . . . . . . . . .   6
       3.2.4.  Service Instance Affinity . . . . . . . . . . . . . .   6
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [I-D.ldbc-cats-framework]defines a framework for Computing-Aware
   Traffic Steering (CATS).  Such a framework defines an approach for
   making compute- and network-aware traffic steering decisions in
   networking environments where services are deployed in many
   locations.

   [I-D.lbdd-cats-dp-sr] proposes a data plane solution for the
   realization of CATS.  The solution uses an anycast IP address as the
   Computing-aware Service ID (CS-ID) associated with a service.  Also,
   the solution uses Segment Routing (SR) as the data plane
   encapsulation from an ingress CATS-Router to an egress CATS-Router.

   [I-D.lbdd-cats-dp-sr] describes the scenario with multiple service
   sites connected to a single egress CATS-Router.  To demultiplex these
   sites, a specific attachment circuit must be provided to indicate the
   specific target service.  In order to explicitly indicate the
   interface towards a site, an END.DX is encoded as the last segment in
   the SRv6 encapsulation[RFC8986].  The associated END.DX is learned
   from the control plane.

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   In the case that there are multiple service contact instances
   connected to the same interface of the egress, the selected specific
   service contact instance can not be distiguished only by END.DX and
   anycast IP.  This document proposes real locator of the service
   contact instance acting as the CIS-ID in [I-D.ldbc-cats-framework].

2.  Terminology

   This document makes use of the terms defined in
   [I-D.ldbc-cats-framework] and [I-D.lbdd-cats-dp-sr].

3.  Solution Overview

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                                   +------+
                                   |Client|
                                   +------+
                                       |
                                +-------------+
                                |    C-TC     |
                                |-------------|
                                |     | C-PS  |
          ......................|     +-------|....................
          :                     |CATS-Router 2|                   :
          :                     +-------------+                   :
          :                                                       :
          :                         Underlay                      :
          :                      Infrastructure                   :
          : SRv6 Encap 1                            SRv6 Encap 2  :
          :                                                       :
          :   +-------------+                +-------------+      :
          :   |CATS-Router 1|                |CATS-Router 3|      :
          :...|             |................|             |......:
              +-------------+                +-------------+
              |    C-SMA    |                |    C-SMA    |
              +-------------+                +-------------+
        END.DX SID1  |              END.DX SID2 |         | END.DX SID3
              ...................             ......    ......
              :                 :             :    :    :    :
              ...................             ......    ......
                | Real IP1    |Real IP2         |         |
            +-----------+  +----------+   +----------+  +----------+
            |  Service  |  | Service  |   | Service  |  | Service  |
            |  contact  |  | contact  |   | contact  |  | contact  |
            |  instance |  | instance |   | instance |  | instance |
            +-----------+  +----------+   +----------+  +----------+

                    Edge site 1           Edge site 2   Edge site 3

       Figure 1: Using SRv6 and Real Locator in CATS

3.1.  Realization of CATS Framework Components

   The realization of CATS Framework in this document adheres to
   [I-D.ldbc-cats-framework] and [I-D.lbdd-cats-dp-sr] and adds some
   additional description.

   As in Figure 1, there is underlay infrastructure between an egress
   CATS-Router and service contact instances.  One egress CATS-Router
   can connect multiple service site.  One service site has only one
   service contact instance or multiple service contact instances.

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   In the realization of CATS framework, CATS service ID is anycast IP
   and CATS Instance Selector ID is the real locator of the CATS service
   contact instance.

   The CATS overlay encapsulation is established from an ingress CATS-
   Router to an egress CATS-Router connected to a service site.To
   describe conveniently in this document the tunnel between CATS-Router
   assumes SRv6[RFC8986].

   As in Figure 1, only one service contact instance is hosted in the
   edge site2.  The solution proposed in I-D.lbdd-cats-dp-sr is enough.
   The solution is only use END.DX or END.DT without real locator.

   But as in Figure 1, the edge site1 has two service contact instances.
   As described in [I-D.ldbc-cats-framework] if the egress CATS-Router
   executes per-instance computing-related metric distribution the real
   locator should be advertised with the service ID too.  And when the
   packet is forwarded according to the computing result of CATS PATH
   Selector the real locator of selected service contact instance should
   be carried besides END.DX or END.DT.  The following section will
   describe the detail of process.

3.2.  Realization of CATS Framework Workflow

   As described in Section 3.4 of [I-D.ldbc-cats-framework], CATS can be
   deployed in a distributed model, centralized model, or a hybrid
   model.  The following description is about distributed model.

3.2.1.  Service Announcement

   This section is the same as Section 3.2.1 of [I-D.lbdd-cats-dp-sr].

3.2.2.  Metrics Distribution

   As per the CATS framework, CS-ID routes with metrics and CIS-ID are
   distributed among the overlay CATS-Routers for per-instance metric
   distribution.  The detailed control plane solutions of metrics
   distribution are out of the scope of this document.  However, a
   sample procedure is provided for the readers convenience.

   For example, BGP can be used to distribute anycast IP route of the
   service with additional metrics and real locator.

   In the case of the C-SMA running as stand alone outside an egress
   CATS-Router, the C-SMA collects the metrics of computing resource for
   the service per one service contact instance and distributes the
   anycast IP route of the service with the collected metrics and real
   locator to the egress CATS-Router.  Egress CATS-Routers will generate

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   new metrics combining the network metrics and computing-related
   metrics, and redistribute the anycast IP route with the new metrics
   and real locator to ingress CATS-Routers.  In the case of the C-SMA
   running as a logic entity on an egress CATS-Router, the same process
   will be performed inside the egress CATS-Router.

3.2.3.  Service Demand processing

   In a distributed model an ingress CATS-Router receives the packet
   with destination address being anycast IP of the service.  The
   ingress CATS-Router determines the special service contact instance
   to serve this packet and get the IP address of the egress CATS-Router
   the service contact instance is connected to, END.DX or END.DT for
   SRv6 and real locator.

   The ingress CATS-Router generates SRv6 encapsulations from itself to
   the egress CATS-Router with real locator carried in the outer IPv6
   extension header.  Egress CATS-Router decapsulates the outer tunnel
   header and get the real locator.  It determines the service site
   according to END.DX or END.DT and forwards the packet to the specific
   service contact instance according to the real locator.

   There are two typical ways to forward the packet from the egress
   CATS-Router to the service contact instance:

   1.  Tunnel mode: The packet with destination IP being anycast IP is
       encapsulated to the tunnel with destination address set to real
       locator.

   2.  IP mode: The packet should be IPv6 packet with the real locator
       carried in the IPv6 extension header.  The CATS-Router and the
       underlay infrastructure should forward the packet according to
       the real locator.  And the real locator in the IPv6 extension
       header can be inserted to the packet in the ingress or egress
       CATS-Router.

3.2.4.  Service Instance Affinity

   This section is the same as Section 3.2.4 of [I-D.lbdd-cats-dp-sr].

4.  Requirements

   This section describes the requirements of protocol extensions about
   the real locator used in CATS .

   [REQ01] IPv6 extension header should be used to carry real locator.

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   [REQ02] Protocol extensions should be defined to advertise real
   locator from C-SMA running as stand alone to an egress CATS-Router.

   [REQ03] Protocol extensions should be defined to advertise real
   locator from an egress CATS-Router to an ingress CATS-Router in a
   distributed model.

5.  Security Considerations

   TBD

6.  IANA Considerations

   There are no IANA considerations in this document.

7.  Normative References

   [I-D.lbdd-cats-dp-sr]
              Li, C., Boucadair, M., Du, Z., and J. Drake, "Computing-
              Aware Traffic Steering (CATS) Using Segment Routing", Work
              in Progress, Internet-Draft, draft-lbdd-cats-dp-sr-01, 11
              January 2024, <https://datatracker.ietf.org/doc/html/
              draft-lbdd-cats-dp-sr-01>.

   [I-D.ldbc-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-ldbc-
              cats-framework-06, 8 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ldbc-cats-
              framework-06>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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/info/rfc8986>.

Authors' Addresses

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   Hang Shi
   Huawei Technologies
   Beijing
   China
   Email: shihang9@huawei.com

   Xia Chen
   Huawei Technologies
   Beijing
   China
   Email: jescia.chenxia@huawei.com

   Zhenbin Li
   Huawei Technologies
   Beijing
   China
   Email: lizhenbin@huawei.com

   Xinxin Yi
   China Unicom
   Beijing
   China
   Email: yixx3@chinaunicom.cn

   Kehan Yao
   China Mobile
   Beijing
   China
   Email: yaokehan@chinamobile.com

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