Flowspec Indirection-id Redirect
draft-ietf-idr-flowspec-path-redirect-12

IDR Working Group                                   G. Van de Velde, Ed.
Internet-Draft                                                     Nokia
Intended status: Standards Track                                K. Patel
Expires: 28 May 2023                                              Arrcus
                                                                   Z. Li
                                                     Huawei Technologies
                                                        24 November 2022

                    Flowspec Indirection-id Redirect
                draft-ietf-idr-flowspec-path-redirect-12

Abstract

   This document defines a new extended community known as "FlowSpec
   Redirect to indirection-id Extended Community".  This extended
   community triggers advanced redirection capabilities to flowspec
   clients.  When activated, this flowspec extended community is used by
   a flowspec client to retrieve the corresponding next-hop and encoding
   information within a localised indirection-id mapping table.

   The functionality detailed in this document allows a network
   controller to decouple the BGP flowspec redirection instruction from
   the operation of the available paths.

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 28 May 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Van de Velde, et al.       Expires 28 May 2023                  [Page 1]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  indirection-id and indirection-id table . . . . . . . . . . .   3
   3.  Use Case Scenarios  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Redirection shortest Path tunnel  . . . . . . . . . . . .   3
     3.2.  Redirection to path-engineered tunnels  . . . . . . . . .   4
     3.3.  Redirection to complex dynamically constructed tunnels  .   5
   4.  Redirect to indirection-id Community  . . . . . . . . . . . .   6
   5.  Redirect using localised indirection-id mapping table . . . .   8
   6.  Validation Procedures . . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  10
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Flowspec is an extension to BGP that allows for the dissemination of
   traffic flow specification rules.  This has many possible
   applications but the primary one for many network operators is the
   distribution of traffic filtering actions for DDoS mitigation.  The
   flowspec standard [RFC8955] defines a redirect-to-VRF action for
   policy-based forwarding, but this mechanism is not always sufficient,
   particularly if the redirected traffic needs to be steered onto an
   explicit path.

   Every flowspec policy route is effectively a rule, consisting of two
   parts.  The first part, encoded in the NLRI field, provides
   information about the traffic matching the policy rule. the second
   part, encoded in one or more BGP extended communities, provides
   policy instructions for traffic handling on the flowspec client.  The
   flowspec standard [RFC8955] defines widely-used filter actions such
   as discard and rate limit; it also defines a redirect-to-VRF action

Van de Velde, et al.       Expires 28 May 2023                  [Page 2]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   for policy-based forwarding.  Using the redirect-to-VRF action to
   steer traffic towards an alternate destination is useful for DDoS
   mitigation, however using this methodology can be cumbersome when
   there is need to steer the traffic onto an explicitely defined
   traffic path.

   This draft specifies a "Redirect to indirection-id" flowspec action
   making use of a 32-bit indirection-id using a new extended community.
   Each indirection-id serves as anchor point, for policy-based
   forwarding onto an explicit path by a flowspec client.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  indirection-id and indirection-id table

   The indirection-id is a 32-bit unsigned number, used as anchor point
   on a flowspec client for policy-based forwarding onto an explicit
   path by a flowspec client.

   The indirection-id table is the table construct of indirection-id
   values, grouped by indirection-id "ID-Type".  Each entry in this
   table contains policy-based forwarding and encoding instructions.

   The configuration of the indirection-id table on a flowspec client is
   a localised operation on each router, and MAY happen out-of-band from
   BGP flowspec.  For some use-case scenarios the indirection-id "ID-
   Type" provides additional (maybe even fully sufficient) context for a
   flowspec client for policy based forwarding, making a localised
   indirection-id table obsolete.  For example, when the indirection-id
   refers to a MPLS segment routing node-id [RFC9256], then the
   indirection-id provides sufficient information for a segment routing
   lookup on the flowspec client.

3.  Use Case Scenarios

   This section describes a few use-case scenarios when deploying
   "Redirect to indirection-id".

3.1.  Redirection shortest Path tunnel

   Description:

Van de Velde, et al.       Expires 28 May 2023                  [Page 3]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   The first use-case describes an example where a single flowspec route
   is sent from a BGP flowspec controller to many BGP flowspec clients.
   This BGP flowspec route carries the "Redirect to indirection-id" to
   all flowspec clients with intent to redirect matching dataflows onto
   a shortest-path tunnel pointing towards a single remote destination.

   In this first use-case scenario, each flowspec client receives
   flowspec routes.  The received flowspec routes have the extended
   "Redirect to indirection-id" community attached.  Each "Redirect to
   indirection-id" community embeds two relevant components: (1) 32-bit
   indirection-id and (2) ID-type.  These two components provide the
   flowspec client with sufficient information for policy based
   forwarding, with intent to steer and encapsulate the data-packet
   accordingly upon a shortest path tunnel to a single remote end-point.

   Requirements:

   For redirect to shortest path tunnel it is required that the tunnel
   MUST be operational and allow packets to flow between tunnel head-
   and tail-end.

   Example: Indirection-ID community "ID-Type" which can be used:

   *  0 (localised ID): When the intent is to use a localised
      Indirection-id table, configured through out-of-band procedures.

   *  1 or 2 (Node ID's): This type can be used when the goal is to use
      MPLS based Segment Routing towards a remote destination.  In this
      use-case scenario the flowspec rule contains a SR (Segment
      Routing) node SID to steer traffic towards.

3.2.  Redirection to path-engineered tunnels

   Description:

   The second use-case describes an example where a single flowspec
   route is sent from a BGP flowspec controller to many BGP flowspec
   clients.  This BGP flowspec route carries policy information to steer
   traffic upon a path-engineered tunnel.  It is assumed that the path
   engineered tunnels are configured using out-of-band from BGP
   flowspec.

   Segment Routing Example:

   For this example the indirection-id "ID-Type" points towards a
   Segment Routing Binding SID.  The Binding SID is a segment identifier
   value (as per segment routing definitions in [RFC8402]) used to
   associate an explicit path.  The Binding SID and the associated path

Van de Velde, et al.       Expires 28 May 2023                  [Page 4]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   engineered tunnel may for example be setup by a controller using BGP
   as specified in [SR-TE] or alternately by using PCEP as detailed in
   [RFC8664].  To conclude, when a BGP speaker at some point in time
   receives a flowspec route with an extended "Redirect to indirection-
   id' community, it installs a policy-based forwarding rule to redirect
   packets onto an explicit path, associated with the corresponding
   Binding SID.  The encoding of the Binding SID within the "Redirect to
   indirection-id" extended community is specified in section 4.

   Requirements:

   For redirect to path engineered tunnels it is required that the
   tunnel MUST be operational and allow packets to flow over the
   engineered path between tunnel head- and tail-end.

   Example: Indirection-ID community "ID-Type" to be used:

   *  0 (localised ID): When the intent is to policy-based steer traffic
      using Indirection.  The engineered path is configured through out-
      of-band procedures and uses the 32-bit Indirection-id as local
      anchor point on the local flowspec client.

   *  3 or 4 (Binding Segment ID's): This type can be used when the goal
      is to use MPLS based Segment Routing towards an out-of-band
      configured explicit path.

   *  5 (Tunnel ID): When the intent is to policy-based steer traffic
      using a global tunnel-id.  The engineered path is configured
      through out-of-band procedures and uses the 32-bit Indirection-id
      as global anchor point on the local flowspec client.

3.3.  Redirection to complex dynamically constructed tunnels

   Description:

   A third use-case describes the application and redirection towards
   complex dynamically constructed tunnels.  For this use-case a BGP
   flowspec controller injects a single flowspec route with two unique
   "Redirect to indirection-id" communities attached, each community
   tagged with a different Sequence-ID (S-ID).  A flowspec client should
   use the Sequence-ID (S-ID) to sequence the received flowspec redirect
   information.  A potential use-case scenario would for example be the
   dynamic construction of Segment Routing Central Egress Path
   Engineered tunnel [RFC9087] or next-next-hop tunnels.

   Segment Routing Example:

Van de Velde, et al.       Expires 28 May 2023                  [Page 5]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   i.e. a classic Segment Routing example using complex tunnels is found
   in DDoS mitigation and traffic offload.  Suspicious traffic (e.g.
   dirty traffic flows) may be policy-based routed into a purpose built
   Segment Routing Central Egress Path Engineered tunnel [RFC9087].  For
   this complex dynamic redirect tunnel construct, a first "Redirect to
   indirection-id" (i.e.  S-ID=0) may be used to redirect traffic into a
   tunnel towards a particular egress router, while a second "Redirect
   to indirection-id" (i.e.  S-ID=1) is used to steer traffic beyond the
   particular egress router towards a pre-identified interface/peer.
   From data-plane perspective, the principles documented by [RFC9087]
   are valid for this use case scenario.

   Requirements:

   To achieve redirection towards complex dynamically constructed
   tunnels, multiple "Redirect to indirection-id" communities are
   imposed upon the flowspec route.  The "Redirect to indirection-id"
   communities should be sequenced using the Sequence ID (S-ID).  For
   redirect to complex dynamic engineered tunnels the tunnel MUST be
   operational and allow packets to flow over the engineered path
   between tunnel head- and tail-end.

   Example: Indirection-ID community "ID-Type" to be used:

   *  0 (localised ID) with S-ID: When the intent is to construct a
      dynamic engineered tunnel, then a sequence of localised
      indirection-ids may be used.  The Sequence ID (S-ID) MUST be used
      to sequence multiple "Redirect to indirection-id" actions to
      construct a more complex engineered tunnel.  The creation of the
      localised indirection-id table is operationalised out-of-band and
      is outside scope of this document.

4.  Redirect to indirection-id Community

   This document defines a new transitive BGP extended community known
   as "FlowSpec Redirect to indirection-id Extended Community" with the
   Type and the Sub-Type field to be assigned by IANA.  The format of
   this extended community is show in Figure 1.

      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Type          | Sub-Type      | Flags(1 octet)|    ID-Type    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Generalized indirection_id                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Van de Velde, et al.       Expires 28 May 2023                  [Page 6]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

                        Figure 1: Extended-Community

   The meaning of the extended community fields are as follows:

   *  Type: 1 octet to be assigned by IANA.

   *  Sub-Type: 1 octet to be assigned by IANA.

   *  Flags: 1 octet field.  Following Flags are defined.

                              0             1
                              0 1 2 3 4 5 6 7
                              +-+-+-+-+-+-+-+-+
                              | RES | S-ID  |C|
                              +-+-+-+-+-+-+-+-+

                              Figure 2: Flags

   The least-significant Flag bit is defined as the 'C' (or copy) bit.
   When the 'C' bit is set the redirection applies to copies of the
   matching packets and not to the original traffic stream.

   The 'S-ID' field identifies a 4 bit Sequence ID field.  This field is
   used to provide a flowspec client an indication how and where to
   sequence the received indirection-ids.  The Sequence ID value 0
   indicates that Sequence ID field is NOT set and all other sequence
   ID's SHOULD be ignored.  A single flowspec rule MUST NOT have more as
   one indirection-id per S-ID.  On a flowspec client the indirection-id
   with lowest S-ID MUST be imposed first for any given flowspec entry.

   All bits other than the 'C' and 'S-ID' bits MUST be set to 0 by the
   originating BGP speaker and ignored by receiving BGP speakers.

   ID-Type: 1 octet value.  This draft defines following Context Types:

   *  0 - Localised ID (The flowspec client uses the received 32-bit
      indirection-id to lookup forwarding information within the
      localised indirection-id table.  The allocation and programming of
      the localised indirection-id table is outside scope of the
      document)

   *  1 - Node ID with SID/index in MPLS-based Segment Routing (This
      means the 32-bit indirection-id is mapped to an MPLS label using
      the index as a global offset in the SID/label space)

Van de Velde, et al.       Expires 28 May 2023                  [Page 7]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   *  2 - Node ID with SID/label in MPLS-based Segment Routing (This
      means the 32-bit indirection-id is mapped to an MPLS label using
      the 32-bit indirection-id as global label)

   *  3 - Binding Segment ID with SID/index in MPLS-based Segment
      Routing (This means the 32-bit indirection-id is mapped to an MPLS
      binding label using the indirection-id as index for global offset
      in the SID/label space) [RFC8402]

   *  4 - Binding Segment ID with SID/label in MPLS-based Segment
      Routing (This means 32-bit indirection-id is mapped to an MPLS
      binding label using the 32-bit indirection-id as global label)
      [RFC8402]

   *  5 - Tunnel ID (Tunnel ID is within a single administrative domain
      a 32-bit globally unique tunnel identifier.  The allocation and
      programming of the Tunnel ID within the localised indirection-id
      table is outside scope of the document)

   Generalized indirection_id: 32-bit identifier used as indirection_id

5.  Redirect using localised indirection-id mapping table

   When a BGP flowspec client receives a flowspec policy route with a
   "Redirect to indirection-id" extended community attached, and the
   route represents the best BGP path, it will install a flowspec
   policy-based forwarding rule matching the tupples described by the
   flowpsec NLRI field and consequently redirects the flow (C=0) or
   copies the flow (C=1) using the information identified by the
   "Redirect to indirection-id" community.

6.  Validation Procedures

   The validation check described in [RFC8955] SHOULD be applied by
   default by a flowspec client, for received flowspec policy routes
   containing a "Redirect to indirection-id" extended community.  This
   results that a flowspec route with a destination prefix subcomponent
   SHOULD NOT be accepted from an EBGP peer unless that peer also
   advertised the best path for the matching unicast route.

   While it MUST NOT happen, and is seen as invalid combination, it is
   possible from a semantics perspective to have multiple clashing
   redirect actions defined within a single flowspec rule.  For best and
   consistant compatibility with legacy implementations, the redirect
   functionality as documented by rfc8955 MUST NOT be broken, and hence
   when a clash occurs, then rfc8955 based redirect MUST take priority.
   Additionally, if the "Redirect to indirection-id" does not result in
   a valid redirection, then the flowspec rule MUST be processed as if

Van de Velde, et al.       Expires 28 May 2023                  [Page 8]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   the "Redirect to indirection-id" community was not attached to the
   flowspec route.  In addition the flowspec client MUST provide an
   indication that the respective "'Redirect to indirection-id" resulted
   in an invalid redirection action.

7.  IANA Considerations

   This document requests a new Transitive Extended Community Type and a
   new registery sub-type.  The new Transitive Extended Community Type
   name shall be "FlowSpec Redirect to indirection-id Extended Community
   (Sub-Types are defined in the "FlowSpec Redirect to indirection-id
   Extended Community Sub-Type" registery)".  The name of the new Sub-
   type registery shall be "FlowSpec Redirect to indirection-id Extended
   Community Sub-Type"

   Under "Transitive Extended Community:"

   Registry: "FlowSpec Redirect to indirection-id Extended Community
   (Sub-Types are defined in the "FlowSpec Redirect to indirection-id
   Extended Community Sub-Type" registery)"

   Registration Procedure(s): First Come, First Served

   0x09 FlowSpec Redirect to indirection-id Extended Community

   New Sub-Type Registry: "FlowSpec Redirect to indirection-id Extended
   Community Sub-Type"

     Value    Code                                   Reference
     0x00     Flowspec Redirect to 32-bit Path-id    RFC-To-Be

                            Figure 3: IANA-Flags

8.  Security Considerations

   A system using "Redirect to indirection-id" extended community can
   cause during the redirect mitigation of a DDoS attack overflow of
   traffic received by the mitigation infrastructure.

9.  References

9.1.  Normative References

Van de Velde, et al.       Expires 28 May 2023                  [Page 9]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [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,
              <https://www.rfc-editor.org/info/rfc8955>.

9.2.  Informative References

   [RFC8664]  Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "Path Computation Element Communication
              Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
              DOI 10.17487/RFC8664, December 2019,
              <https://www.rfc-editor.org/info/rfc8664>.

   [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>.

   [RFC9256]  Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
              A., and P. Mattes, "Segment Routing Policy Architecture",
              RFC 9256, DOI 10.17487/RFC9256, July 2022,
              <https://www.rfc-editor.org/info/rfc9256>.

   [SR-TE]    Talaulikar, K., Filsfils, C., Previdi, S., Jain, D.,
              Mattes, P., and S. Lin, "Advertising Segment Routing
              Policies in BGP", July 2022.

Acknowledgements

   This document received valuable comments and input from IDR working
   group including Adam Simpson, Mustapha Aissaoui, Jan Mertens, Robert
   Raszuk, Jeff Haas, Susan Hares and Lucy Yong.

Van de Velde, et al.       Expires 28 May 2023                 [Page 10]
Internet-Draft      Flowspec Indirection-id Redirect       November 2022

Contributors

   The following people contributed to the content of this document and
   should be considered as co-authors:

   *  Arjun Sreekantiah, USA, arjunhrs@gmail.com

   *  Nan Wu, Huawei Technologies, China, eric.wu@huawei.com

   *  Shunwan Zhuang, Huawei Technologies, China,
      zhuangshunwan@huawei.com

   *  Wim Henderickx, Nokia Antwerp, Belgium, wim.henderickx@nokia.com

Authors' Addresses

   Gunter Van de Velde (editor)
   Nokia
   Antwerp
   Belgium
   Email: gunter.van_de_velde@nokia.com

   Keyur Patel
   Arrcus
   United States of America
   Email: keyur@arrcus.com

   Zhenbin Li
   Huawei Technologies
   Huawei Bld., No. 156 Beiquing Rd
   Beijing
   100095
   China
   Email: lizhenbin@huawei.com

Van de Velde, et al.       Expires 28 May 2023                 [Page 11]