Internet DRAFT - draft-liu-cats-bgp-epe-applicability

draft-liu-cats-bgp-epe-applicability







IDR                                                               X. Liu
Internet-Draft                                              China Mobile
Intended status: Informational                              10 July 2023
Expires: 11 January 2024


                  Using BGP EPE Control Plane for CATS
                draft-liu-cats-bgp-epe-applicability-00

Abstract

   This document describes an approach for using the BGP EPE Control
   Plane [RFC8670] for CATS cross as domain steering traffic based on a
   normalized metric that reflect the underlying network conditions and
   other service-specific metrics collected from available service
   locations.

Status of This Memo

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   This Internet-Draft will expire on 11 January 2024.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   2
   3.  CATS information to be Distributed by BGP . . . . . . . . . .   3
   4.  BGP EPE for CATS  . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Metric collected and distributed  . . . . . . . . . . . .   4
     4.2.  BGP Extension for CATS  . . . . . . . . . . . . . . . . .   5
     4.3.  Implemention for BGP EPE CATS . . . . . . . . . . . . . .   5
   5.  Minimum Interval for Metrics Change Advertisement . . . . . .   6
   6.  Manageability Considerations  . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   BGP (Border Gateway Protocol) is a dynamic routing protocol between
   autonomous system AS (Autonomous System).  The BGP EPE function is an
   extension of BGP to Segment Routing to implement source routing
   between AS.

   Enabling BGP EPE?egress peer engineering [RFC8670], BGP Peer SID can
   be assigned to inter-domain paths and Peer SID can be passed to the
   network controller via BGP-LS extension.  Through the rational
   arrangement of IGP SID and BGP Peer SID, the controller can realize
   the optimal path forwarding across the domain.

   In addition to the Peer Node and Peer Adjacency, there is also the
   Peer Set. Peer Set That is, a group of neighbors as a Set, and then
   assign SID based on the group.  This SID can also correspond to
   multiple outgoing interfaces.

   CATS is about finding an optimal service path for arrange a service
   request, and thus about selecting one of the available service
   instances that better optimize a set of metrics .  The document
   focuses on multiple AS domains traffic engineering .

2.  Definition of Terms

   This document makes use of the following terms:

   Computing-Aware Traffic Steering (CATS):  Aiming at computing and




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     network resource optimization by steering traffic to appropriate
     computing resources considering not only routing metric but also
     computing resource metric.

   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.

   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.

   Service identifier:  Used to uniquely identify a service, at the same
     time identifying the whole set of service instances that each
     represents the same service behavior, no matter where those service
     instances are running.

   Service transaction:  Has one or more service request that has
     several flows which require the affinity because of the transaction
     related state.

   Computing Capacity:  The ability of nodes with computing resource
     achieve specific result output through data processing, including
     but not limited to computing, communication, memory and storage
     capacity.

3.  CATS information to be Distributed by BGP

   The goal of the proposed BGP extension is to distribute the metrics
   collected by C-SMAs (CATS Service Metric Agents) to the CATS SDN
   controller(centrial framwork) or ingress routers(distribued framwork)
   to be used by the corresponding CATS Path Selectors .  In this
   document, We mainly propose a multi-domain centralized computing
   force routing implementation scheme, combined with BGP EPE technology
   to realize cats multi-domain traffic scheduling.

   The detailed metrics collected by a C-SMA will be decided by the CATS
   WG . And the encoding of the CATS metrics that will be selected by
   the WG will be discussed in IDR WG . When a CATS ingress router
   receives metrics updates for a Service ID from multiple CATS egress
   routers, all those egress routers are considered as the next hops for
   that Service ID . The Service ID is represented as an IPv4/IPv6
   unicast address, which is assigned to a group of interfaces to which
   the service instances are attached .

   The CATS ingress router's BGP engine will send this metric to SDN
   controller by BGP-LS protocol.  According to the collected computing
   power resource information and network information, the SDN



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   controller generates an end-to-end segmentID list through the
   computing path algorithm, which is sent to cats ingress through BGP
   SR policy.

4.  BGP EPE for CATS

4.1.  Metric collected and distributed

   As shown in Figure 1, computing service node 1 and node 2 are cloud
   resource pools, which can provide computing power resource services.
   The main functions of the computing power agent(C-SMA) module are as
   follows:

   Use restful protocol to collect the computing information of
   computing service nodes.  The computing information includes CPU
   utilization, memory utilization, GPU utilization, storage capacity,
   DPU utilization, energy efficiency of computing power nodes, etc.

   The computing power agent module normalized the collected computing
   information(metric) by PageRank algorithm to generate the
   comprehensive computing power index metric.  The larger the metric,
   the more preferred.

   Computing power information notification, as shown in Figure R11,
   R12, as the exit router of computing power agent module, needs to
   have BGP routing protocol capability.  R9, R11, R 11 and R12 should
   establish BGP neighbors respectively.  The BGP update message passes
   the above normalized metric value to R9 and R10.























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                                                               +---------+
                                                               | R12     |
        +---------------+  +-----------------+  +------------+ |         |
        | SDN           |  |        R8       |  |            | |    C-SMA|
        |               |  |                 |  |            | +---------+
        |          R2   |  |                 |  |     R10    |
        |               |  |   R4      R6    |  |            |
        |               |  |       AS3       |  |            |
        | R1            |  +-----------------+  |            |
        |               |                       |            |
        |               |   +----------------+  |            |
        |         R3    |   |                |  |            |
        |               |   |                |  |            |
        |               |   |  R5      R7    |  |     R9     |
        |               |   |                |  |            | +----------+
        |      AS1      |   |     AS2        |  |    AS4     | | R11      |
        +---------------+   +----------------+  +------------+ |          |
                                                               |     C-SMA|
                                                               +----------+

                                 |

                Figure 1: Modeling of BGP EPE For CSTS

4.2.  BGP Extension for CATS

   As shown in FIG. 1, the router R9 and R10 of AS4 receive the
   computing information(metric) distributed by the R9 to its? all
   peers.(the process flow of R9 is same R10, we use R9 for example in
   following).The R9 as the export router of AS4 domain would to be
   assigned a BGP prefix SID [RFC8669], while enabling BGP LU address
   family(BGP label unicast address family). routers establishing IBGP
   peers within inter-domain, and intra-domain establishing EBGP peers .
   By extending the BGP update message that add a new BGP attribute
   indicates the metric of the computing resource pool hanging under the
   egress router.  R1 can receive the BGP prefix-SID of R9 through the
   message interaction between bgp peers.  Finally, the metric will be
   sent to SDN controller.

4.3.  Implemention for BGP EPE CATS

   Enabling BGP EPE[RFC7855] function on egress routers of each As
   domain.  After the device starts the EPE function, BGP peer SID will
   be automatically assigned, and the SDN controller in the domain will
   collect Peer SID, all BGP routes,the network information, the
   topology information, the information from the EPE function in the
   domain, and the metric which distributed by C-SMA of CATS.




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   According to the business needs, the controller determines the last
   jump of the egress equipment of the computing resource pool that
   meets the computing requirements to generate SID-LIST.  The
   controller sends the SID-LIST to the forwarding entry device(ingress
   device, R1 in Fig.1) through the border gateway protocol or the PCEP
   protocol.  Finally, in the cross-domain scenario, the appropriate
   service center can be determined according to the computing
   information(metirc), and at the same time, the traditional BGP based
   on the shortest path selection, realizing the cross-domain computing
   network traffic engineering.

5.  Minimum Interval for Metrics Change Advertisement

   As the metrics change can triger bgp provider send update message to
   peer, the bgp route table may changed, and impact the path selection.
   The route update interval was fifteen seconds for the IBGP peer, and
   thirty seconds for the EBGP peer.  The Minimum Interval for Metrics
   Change Advertisement is configured to control the bgp message update
   frequency to avoid bgp route oscillations . The minmun interval is
   set equal or greater than bgp route fresh interval in best .

6.  Manageability Considerations

   The Edge Service Metadata described in this document are only
   intended for propagating between Ingress and egress routers of one
   single BGP domain . Only the selective services by clients are
   considered as CATS Services, which are managed by one operator, even
   though the routers can be by different vendors.

7.  Security Considerations

   BGP EPE CATS needs to follow the spring architecture[RFC7855], and be
   consistent with the spring architecture?s security considerations.

8.  IANA Considerations

   In the current IANA definition, the number 41 to 127 are unused.  The
   type value (Type Code) of the computing-aware routing attribute is
   defined as optional transitive, and the normalized metric attribute
   type value is temporarily set to 127.

9.  Acknowledgements

   TBD.

10.  References

10.1.  Normative References



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   [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>.

   [RFC8670]  Filsfils, C., Ed., Previdi, S., Dawra, G., Aries, E., and
              P. Lapukhov, "BGP Prefix Segment in Large-Scale Data
              Centers", RFC 8670, DOI 10.17487/RFC8670, December 2019,
              <https://www.rfc-editor.org/info/rfc8670>.

   [RFC8669]  Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
              A., and H. Gredler, "Segment Routing Prefix Segment
              Identifier Extensions for BGP", RFC 8669,
              DOI 10.17487/RFC8669, December 2019,
              <https://www.rfc-editor.org/info/rfc8669>.

   [RFC9085]  Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
              H., and M. Chen, "Border Gateway Protocol - Link State
              (BGP-LS) Extensions for Segment Routing", RFC 9085,
              DOI 10.17487/RFC9085, August 2021,
              <https://www.rfc-editor.org/info/rfc9085>.

   [RFC9086]  Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel, K.,
              Ray, S., and J. Dong, "Border Gateway Protocol - Link
              State (BGP-LS) Extensions for Segment Routing BGP Egress
              Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
              2021, <https://www.rfc-editor.org/info/rfc9086>.

   [RFC9087]  Filsfils, C., Ed., Previdi, S., Dawra, G., Ed., Aries, E.,
              and D. Afanasiev, "Segment Routing Centralized BGP Egress
              Peer Engineering", RFC 9087, DOI 10.17487/RFC9087, August
              2021, <https://www.rfc-editor.org/info/rfc9087>.

10.2.  Informative References

   [RFC7855]  Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
              Litkowski, S., Horneffer, M., and R. Shakir, "Source
              Packet Routing in Networking (SPRING) Problem Statement
              and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
              2016, <https://www.rfc-editor.org/info/rfc7855>.











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   [I-D.yao-cats-ps-usecases]
              Yao, K., Trossen, D., Boucadair, M., Contreras, L. M.,
              Shi, H., Li, Y., and S. Zhang, "Computing-Aware Traffic
              Steering (CATS) Problem Statement, Use Cases and
              Requirements", Work in Progress, Internet-Draft, draft-
              yao-cats-ps-usecases-02, 22 June 2023,
              <https://datatracker.ietf.org/doc/html/draft-yao-cats-ps-
              usecases-02>.

Author's Address

   Xingsheng Liu
   China Mobile
   No.32 XuanWuMen West Street
   Beijing
   100053
   China
   Email: liuxing0315@sohu.com

































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