Traffic Steering using BGP Flowspec with SRv6 Policy

Document Type Active Internet-Draft (individual)
Authors Jiang Wenying  , Yisong Liu  , Shuanglong Chen 
Last updated 2021-07-11
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Network Working Group                                               W. J
Internet-Draft                                                    Y. Liu
Intended status: Informational                              China Mobile
Expires: January 13, 2022                                        S. Chen
                                                           July 12, 2021

          Traffic Steering using BGP Flowspec with SRv6 Policy


   BGP Flow Specification (FlowSpec) [RFC8955] has been proposed to
   distribute BGP FlowSpec NLRI to FlowSpec clients to mitigate
   (distributed) denial-of-service attacks, and to provide traffic
   filtering in the context of a BGP/MPLS VPN service.  Recently,
   traffic steering applications in the context of SRv6 using FlowSpec
   aslo attract attention.  This document introduces the usage of BGP
   FlowSpec to steer packets into an SRv6 Policy.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 13, 2022.

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Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definitions and Acronyms  . . . . . . . . . . . . . . . . . .   3
   3.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Application Example . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Segment Routing IPv6 (SRv6) is a protocol designed to forward IPv6
   data packets on a network using the source routing model.  SRv6
   enables the ingress to add a segment routing header (SRH) [RFC8754]
   to an IPv6 packet and push an explicit IPv6 address stack into the
   SRH.  After receiving the packet, each transit node updates the IPv6
   destination IP address in the packet and segment list to implement
   hop-by-hop forwarding.

   SRv6 Policy [I-D.ietf-spring-segment-routing-policy] is a tunneling
   technology developed based on SRv6.  An SRv6 Policy is a set of
   candidate paths consisting of one or more segment lists, that is,
   segment ID (SID) lists.  Each SID list identifies an end-to-end path
   from the source to the destination, instructing a device to forward
   traffic through the path rather than the shortest path computed using
   an IGP.  The header of a packet steered into an SRv6 Policy is
   augmented with an ordered list of segments associated with that SRv6

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   Policy, so that other devices on the network can execute the
   instructions encapsulated into the list.

   The headend of an SRv6 Policy may learn multiple candidate paths for
   an SRv6 Policy.  Candidate paths may be learned via a number of
   different mechanisms, e.g., CLI, NetConf, PCEP, or BGP.

   [RFC8955] defines the flow specification (FlowSpec) that allows to
   convey flow specifications and traffic Action/Rules associated (rate-
   limiting, redirect, remark ...).  BGP Flow specifications are encoded
   within the MP_REACH_NLRI and MP_UNREACH_NLRI attributes.  Rules
   (Actions associated) are encoded in Extended Community attribute.
   The BGP Flow Specification function allows BGP Flow Specification
   routes that carry traffic policies to be transmitted to BGP Flow
   Specification peers to steer traffic.

   This document proposes BGP flow specification usage that are used to
   steer data flow into an SRv6 Policy as well as to indicate Tailend

2.  Definitions and Acronyms

   o  FlowSpec: Flow Specification

   o  SR: Segment Routing

   o  SRv6: IPv6 Segment Routing

   o  SID: Segment Identifier

   o  SRH: Segment Routing Header

   o  TE: Traffic Engineering

3.  Operations

   An SRv6 Policy [I-D.ietf-spring-segment-routing-policy] is identified
   through the tuple <headend, color, endpoint>.  In the context of a
   specific headend, one may identify an SRv6 policy by the <color,
   endpoint> tuple.  The headend is the node where the SRv6 policy is
   instantiated/implemented.  The headend is specified as an IPv4 or
   IPv6 address and is expected to be unique in the domain.  The
   endpoint indicates the destination of the SRv6 policy.  The endpoint
   is specified as an IPv6 address and is expected to be unique in the
   domain.  The color is a 32-bit numerical value that associates the
   SRv6 Policy, and it defines an application-level network Service
   Level Agreement (SLA) policy.

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   Assume one or multiple SRv6 Policies are already setup in the SRv6
   HeadEnd device.  In order to steer traffic into a specific SRv6
   policy at the Headend, one can use the SRv6 color extended community
   and endpoint to map to a satisfying SRv6 policy, and steer traffic
   into this specific policy.

   [I-D.ietf-idr-flowspec-redirect-ip] defines the redirect to IPv4 and
   IPv6 Next-hop action.  The IPv6 next-hop address in the Flow-spec
   Redirect to IPv6 Extended Community can be used to specify the
   endpoint of the SRv6 Policy.  When the packets reach to the TailEnd
   device, some specific function imformation identifiers can be used
   decide how to further process the flows.  Several endpoint functions
   are already defined, e.g., End.DT6: Endpoint with decapsulation and
   IPv6 table lookup, and End.DX6: Endpoint with decapsulation and IPv6
   cross-connect.  The BGP Prefix-SID defined in [RFC8669] is utilized
   to enable SRv6 VPN services [I-D.ietf-bess-srv6-services].  SRv6
   Services TLVs within the BGP Prefix-SID Attribute can be used to
   indicate the endpoint functions.

   This document proposes to carry the Color Extended Community and BGP
   Prefix-SID Attribute in the context of a Flowspec NLRI [RFC8955] to
   an SRv6 Headend to steer traffic into one SRv6 policy, as well as to
   indicate specific Tailend functions.

   In this document, the usage of at most one Color Extended Community
   in combination at most one BGP Prefix SID Attribute is discussed.
   For the case that a flowspec route carries multiple Color Extend
   Communities and/or a BGP Prefix SID Attribute, a protocol extension
   to Flowspec is required, and is thus out of the scope of this

   However, the method proposed in this document still supports load
   balancing to the tailend device.  To achieve that, the headend device
   CAN set up multiple paths in one SRv6 policy, and use a Flowspec
   route to indicate the specific SRv6 policy.

4.  Application Example

   In following scenario, BGP FlowSpec Controller signals the function
   imformation (SRv6 SID: Service_id_x) to the HeadEnd device.

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      |  BGP FS    |
      | Controller |
         | Flowspec route to HeadEnd:
         |   NLRI: Filter Rules
         |   Redirect to IPv6 Nexthop: TailEnd's Address
         |   Policy Color: C1
         |   PrefixSID: Service_id_x
         |          .-----.
         |         (       )
         V     .--(         )--.
   +-------+  (                 )  +-------+
   |       |_( SRv6 Core Network )_|       |
   |HeadEnd| ( ================> ) |TailEnd|
   +-------+  (SR List<S1,S2,S3>)  +-------+
               '--(         )--'   Service SID: Service_id_x
                   (       )       (e.g.: End.DT4 or End.DT6 or others)

         Figure 1: Steering the Flow into SRv6 Policy

   When the headend device (as a Flowspec client) receives such
   instructions, it will steer the flows matching the criteria in the
   Flowspec route into the SRv6 Policy matching the tuple (Endpoint:
   TailEnd's Address, Color: C1).  And the packets of such flows will be
   encapsulated with SRH using the SR List<S1, S2, S3, Service_id_x>.
   When the packets reach to the TailEnd device, they will be further
   procetssed per the function denoted by the Service_id_x.

   For the cases of intra-AS and inter-AS traffic steering using this
   method, the usages of Flowspec Color Extended Community with BGP
   prefix SID are the same for both scenarios.  The difference lie
   between the local SRv6 policy configurations.  For the inter-domain
   case, the operator can configure an inter-domain SRv6 policy/path at
   the Headend device.  For the intra-domain case, the operator can
   configure an intra-domain SRv6 policy/path at the Headend device.

5.  IANA Considerations

   No IANA actions are required for this document.

6.  Security Considerations

   This document does not change the security properties of SRv6 and

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7.  Contributors

   The following people made significant contributions to this document:

   Yunan Gu

   Shunwan Zhaung

   Haibo Wang

   Jie Dong

8.  Acknowledgements


9.  References

9.1.  Normative References

              Dawra, G., Filsfils, C., Talaulikar, K., Raszuk, R.,
              Decraene, B., Zhuang, S., and J. Rabadan, "SRv6 BGP based
              Overlay Services", draft-ietf-bess-srv6-services-07 (work
              in progress), April 2021.

              Uttaro, J., Haas, J., Texier, M., Karch, A., Ray, S.,
              Simpson, A., and W. Henderickx, "BGP Flow-Spec Redirect to
              IP Action", draft-ietf-idr-flowspec-redirect-ip-02 (work
              in progress), February 2015.

              Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
              Rosen, E., Jain, D., and S. Lin, "Advertising Segment
              Routing Policies in BGP", draft-ietf-idr-segment-routing-
              te-policy-11 (work in progress), November 2020.

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              Patel, K., Velde, G. V. D., Sangli, S. R., and J. Scudder,
              "The BGP Tunnel Encapsulation Attribute", draft-ietf-idr-
              tunnel-encaps-22 (work in progress), January 2021.

              Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", draft-
              ietf-spring-segment-routing-policy-11 (work in progress),
              April 2021.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [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,

   [RFC8955]  Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
              Bacher, "Dissemination of Flow Specification Rules",
              RFC 8955, DOI 10.17487/RFC8955, December 2020,

9.2.  Informative References

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,

Authors' Addresses

   Wenying Jiang
   China Mobile


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   Yisong Liu
   China Mobile


   Shuanglong Chen


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