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BGP Dissemination of Flow Specification Rules for Tunneled Traffic
draft-ietf-idr-flowspec-nvo3-19

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This is an older version of an Internet-Draft whose latest revision state is "Active".
Authors Donald E. Eastlake 3rd , Hao Weiguo , Shunwan Zhuang , Zhenbin Li , Rong Gu
Last updated 2023-12-26 (Latest revision 2023-07-05)
Replaces draft-hao-idr-flowspec-nvo3
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draft-ietf-idr-flowspec-nvo3-19
IDR Working Group                                            D. Eastlake
Internet-Draft                                    Futurewei Technologies
Intended status: Standards Track                                  W. Hao
Expires: 28 June 2024                                          S. Zhuang
                                                                   Z. Li
                                                     Huawei Technologies
                                                                   R. Gu
                                                            China Mobile
                                                        26 December 2023

   BGP Dissemination of Flow Specification Rules for Tunneled Traffic
                    draft-ietf-idr-flowspec-nvo3-19

Abstract

   This draft specifies a Border Gateway Protocol (BGP) Network Layer
   Reachability Information (NLRI) encoding format for flow
   specifications (RFC 8955) that can match on a variety of tunneled
   traffic.  In addition, flow specification components are specified
   for certain tunneling header fields.

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 June 2024.

Copyright Notice

   Copyright (c) 2023 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 (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

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   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Tunneled Traffic Flow Specification NLRI  . . . . . . . . . .   4
     2.1.  The SAFI Code Point . . . . . . . . . . . . . . . . . . .   7
     2.2.  Tunnel Header Component Code Points . . . . . . . . . . .   7
     2.3.  Specific Tunnel Types . . . . . . . . . . . . . . . . . .   9
       2.3.1.  VXLAN . . . . . . . . . . . . . . . . . . . . . . . .  10
       2.3.2.  VXLAN-GPE . . . . . . . . . . . . . . . . . . . . . .  11
       2.3.3.  NVGRE . . . . . . . . . . . . . . . . . . . . . . . .  11
       2.3.4.  L2TPv3  . . . . . . . . . . . . . . . . . . . . . . .  11
       2.3.5.  GRE . . . . . . . . . . . . . . . . . . . . . . . . .  13
       2.3.6.  IP-in-IP  . . . . . . . . . . . . . . . . . . . . . .  13
       2.3.7.  Geneve  . . . . . . . . . . . . . . . . . . . . . . .  14
     2.4.  Tunneled Traffic Actions  . . . . . . . . . . . . . . . .  14
   3.  Order of Traffic Filtering Rules  . . . . . . . . . . . . . .  15
   4.  Flow Spec Validation  . . . . . . . . . . . . . . . . . . . .  15
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  17
   8.  Informative References  . . . . . . . . . . . . . . . . . . .  19
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   BGP Flow Specification (flowspec [RFC8955]) is an extension to BGP
   that supports the dissemination of traffic flow specification rules
   and actions to be taken on packets matching such specifications.  It
   uses the BGP control plane to simplify the distribution of Access
   Control Lists (ACLs) and allows new filter rules to be injected to
   all BGP peers simultaneously without changing router configuration.
   A typical application of BGP flowspec is to automate the distribution
   of traffic filter lists to routers for Distributed Denial of Service
   (DDOS) mitigation.

   BGP flowspec defines BGP Network Layer Reachability Information
   (NLRI) formats used to distribute traffic flow specification rules.
   AFI=1/SAFI=133 is for IPv4 unicast filtering.  AFI=1/SAFI=134 is for
   IPv4 BGP/MPLS VPN filtering [RFC8955].  [RFC8956] and [FlowSpecL2]
   extend the flowspec rules for IPv6 and Layer 2 Ethernet packets
   respectively.  None of these previously defined flow specifications

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   are suitable for matching packets in cases of tunneling or
   encapsulation where there might be duplicates of a layer of header
   such as two IPv6 headers in IP-in-IP [RFC2003] or a nested header
   sequence such as the Layer 2 and 3 headers encapsulated in VXLAN
   [RFC7348].

   In the cloud computing era, multi-tenancy has become a core
   requirement for data centers.  It is increasingly common to see
   tunneled traffic with a field to distinguish tenants.  An example is
   the Network Virtualization Over Layer 3 (NVO3 [RFC8014]) overlay
   technology that can satisfy multi-tenancy key requirements.  VXLAN
   [RFC7348] and NVGRE [RFC7637] are two typical NVO3 encapsulations.
   Other encapsulations such as IP-in-IP or GRE may be encountered.
   Because these tunnel / overlay technologies involving an additional
   level of encapsulation, flow specification that can match on the
   inner header as well as the outer header and fields in any tunneling
   header are needed.

   In summary, Flow Specifications should be able to include inner
   nested header information as well as fields specific to the type of
   tunneling in use such as virtual network / tenant ID.  This draft
   specifies methods for accomplishing this using SAFI=77 and a new NLRI
   encoding.  In addition, flow specification components are specified
   for certain tunneling header fields.

1.1.  Terminology

   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.

   The reader is assumed to be familiar with BGP terminology [RFC4271]
   [RFC4760].  The following terms and acronyms are used in this
   document with the meaning indicated:

   ACL  - Access Control List

   DDoS  - Distributed Denial of Service (Attack)

   DSCP  - Differentiated Services Code Point [RFC2474]

   GRE  - Generic Router Encapsulation [RFC2890]

   L2TPv3  - Layer Two Tunneling Protocol - Version 3 [RFC3931]

   NLRI  - Network Layer Reachability Information [RFC4271] [RFC4760]

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   NVGRE  - Network Virtualization Using Generic Routing Encapsulation
      [RFC7637]

   NVO3  - Network Virtual Overlay Layer 3 [RFC8014]

   PE  - Provider Edge

   VN  - virtual network

   VXLAN  - Virtual eXtensible Local Area Network [RFC7348]

2.  Tunneled Traffic Flow Specification NLRI

   The Flowspec rules specified in [RFC8955], [RFC8956], and
   [FlowSpecL2] cannot match or filter tunneled traffic based on the
   tunnel type, tunnel header fields, or headers past the tunnel header.
   To enable flow specification of tunneled traffic, a new SAFI (77) and
   NLRI encoding are specified.  This encoding, shown in Figure 1,
   enables flow specification of more than one layer of header when
   needed.

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              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              | Length                          2 octets      |
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              | Tunnel Type                     2 octets      |
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
            Flags:
              +--+--+--+--+--+--+--+--+
              | D| I| Reserved        |         1 octet
              +--+--+--+--+--+--+--+--+
            Optional Routing Distinguisher:
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              |                                               |
              +                                               +
              |                                               |
              + Routing Distinguisher           8 octets      +
              |                                               |
              +                                               +
              |                                               |
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
            Outer Flowspec:
              +--+--+--+--+--+--+--+--+
              | Outer Flowspec Length ...       1 or 2 octets
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              | Outer Flowspec                  variable      :
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
            Tunnel Header Flowspec:
              +--+--+--+--+--+--+--+--+
              | Tunnel Flowspec Length ...      1 or 2 octets
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              | Tunnel Header Flowspec          variable      :
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
            Optional Inner Flowspec:
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              | Inner AFI                       2 octets      |
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              | Inner Flowspec Length ...       1 or 2 octets
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
              | Inner Flowspec                  variable      :
              +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

                  Figure 1: Tunneled Traffic Flowspec NLRI

   Length  - The NLRI Length encoded as an unsigned integer including
      the Tunnel Type.

   Tunnel Type  - The type of tunnel using a value from the IANA BGP
      Tunnel Encapsulation Attribute Tunnel Types registry.

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   Flags: D bit  - Indicates the presence of the Routing Distinguisher
      (see below).

   Flags: I bit  - Indicates the presence of the Inner AFI and the Inner
      Flowspec (see below).

   Flags: Reserved  - Six bits that MUST be sent as zero and ignored on
      receipt.

   Routing Distinguisher  - If the outer Layer 3 address belongs to a
      BGP/MPLS VPN, the routing distinguisher is included to indicate
      traffic filtering within that VPN.  Because NVO3 outer layer
      addresses normally belong to a public network, a Route
      Distinguisher field is normally not needed for NVO3.

   Outer Flowspec / Length  - The flow specification for the outer
      header.  The length is encoded as provided in Section 4.1 of
      [RFC8955].  The AFI for the Outer Flowspec is the AFI at the
      beginning of the BGP multiprotocol MP_REACH_NLRI or
      MP_UNREACH_NLRI containing the tunneled traffic flow specification
      NLRI.

   Tunnel Header Flowspec / Length  - The flow specification for the
      tunneling header.  The length is encoded as provided in
      Section 4.1 of [RFC8955].  This specifies matching criterion on
      tunnel header fields as well as, implicitly, on the tunnel type
      which is indicated by the Tunnel Type field above.  For some types
      of tunneling, such as IP-in-IP, there may be no tunnel header
      fields.  For other types of tunneling, there may be several tunnel
      header fields on which matching can be specified with this
      flowspec.  If a Tunnel Type has no tunnel header fields or it is
      not desired to filter on header fields, the Tunnel Flowspec length
      field is present but has value zero.

   Inner AFI  - Depending on the Tunnel Type, there may be an Inner AFI
      that indicate the type of inner flow specification.  The "Inner
      SAFI" is implicitly 133 for flowspec.

   Inner Flowspec / Length  - Depending on the Tunnel Type, there may be
      an inner flowspec for the header level encapsulated within the
      outer header.  The length is encoded as provided in Section 4.1 of
      [RFC8955].

   A Tunneled Traffic Flowspec matches if the Outer Flowspec, Tunnel
   Type, and Tunnel Header Flowspec match and, in addition, each of the
   following optional items matches if it is present:

   -  Inner Flowspec, and

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   -  Routing Distinguisher.

   An omitted (as can be done for the Inner Flowspec) or null flowspec
   is considered to always match.

2.1.  The SAFI Code Point

   Use of the tunneled traffic flow specification NLRI format is
   indicated by SAFI=77.  This is used in conjunction with the AFI for
   the outer header, that is AFI=1 for IPv4, AFI=2 for IPv6, and AFI=6
   for Layer 2.

2.2.  Tunnel Header Component Code Points

   For most cases of tunneled traffic, there are tunnel header fields
   that can be tested by components that appear in the Tunnel Header
   Flowspec field.  The types for these components are specified in a
   Tunnel Header Flowspec component registry (see Section 6) and the
   initial entries in this registry are specified below.

   All Tunnel Header field components defined below and all such
   components added in the future have a TLV structure as follows:

   -  one octet of type followed by

   -  one octet giving the length of the value part as an unsigned
      integer number of octets followed by

   -  the specific matching operations/values as determined by the type.

   Type 1 -  VN ID

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match the
      24-bit VN ID (Virtual Network Identifier) that is used as the
      tenant identification in some tunneling headers.  For VXLAN and
      Geneve encapsulation, the VN ID field is the VNI.  For NVGRE
      encapsulation, the VN ID is the VSID. op is encoded as specified
      in Section 4.2.3 of [RFC8955].  Values are encoded as a 1, 2, or 4
      octet quantity.  If value is 24-bits, it is left-justified in the
      first 3 octets of the value and the last value octet MUST be sent
      as zero and ignored on receipt.

   Type 2 -  Flow ID

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

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      Defines a list of {operation, value} pairs used to match 8-bit
      Flow ID fields which are currently only useful for NVGRE
      encapsulation. op is encoded as specified in Section 4.2.3 of
      [RFC8955].  Values are encoded as a 1-octet quantity.

   Type 3 -  Session

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match a 32-bit
      Session field.  This field is called Key in GRE [RFC2890]
      encapsulation and Session ID in L2TPv3 encapsulation. op is
      encoded as specified in Section 4.2.3 of [RFC8955].  Values are
      encoded as a 1, 2, or 4 octet quantity; if 1 or 2 octets are
      provided, these are right justified and padded on the left with
      zeros.

   Type 4 -  Cookie

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match a
      variable length Cookie field.  This is only useful in L2TPv3
      encapsulation. op is encoded as specified in Section 4.2.3 of
      [RFC8955].  Values are encoded as a 1, 2, 4, or 8 octet quantity.
      If the Cookie does not fit exactly into the value length, it is
      left justified and padded with following octets that MUST be sent
      as zero and ignored on receipt.

   Type 5 -  Tunnel Header Flags

   Encoding:  <type (1 octet), length (1 octet), [op, bitmask]+>

      Defines a list of {operation, bitmask} pairs used to match against
      the tunnel header flags field. op is encoded as in Section 4.2.9
      of [RFC8955]. bitmask is encoded as 1 octet for VXLAN-GPE and
      Geneve and as 2 octets for L2TPv3 control messages.  When matching
      on L2TPv3 control message flags, the 3-bit Version subfield is
      treated as if it was zero.

   Type 6 -  L2TP Control Version

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match against
      the L2TP Control Message Version. op is encoded as in
      Section 4.2.3 of [RFC8955].  Value is encoded as 1 octet.

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   Type 7 -  L2TPv3 Control Connection ID

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match against
      the L2TPv3 Control Connection ID. op is encoded as in
      Section 4.2.3 of [RFC8955].  Value is encoded as 4 octets.

   Type 8 -  L2TPv3 Ns

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match against
      the L2TPv3 control message Ns field. op is encoded as in
      Section 4.2.3 of [RFC8955].  Value is encoded as 2 octets.

   Type 9 -  L2TPv3 Nr

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match against
      the L2TPv3 control message Nr field. op is encoded as in
      Section 4.2.3 of [RFC8955].  Values are encoded as 2 octets.

   Type 10 -  Protocol Type

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match against
      the GRE and Geneve Protocol Type fields. op is encoded as in
      Section 4.2.3 of [RFC8955].  Values are encoded as 2 octets.

   Type 11 -  GRE Sequence

   Encoding:  <type (1 octet), length (1 octet), [op, value]+>

      Defines a list of {operation, value} pairs used to match against
      the GRE Sequence field. op is encoded as in Section 4.2.3 of
      [RFC8955].  Values are encoded as a 1, 2, or 4 octet quantity; if
      1 or 2 octets are provided, these are right justified and padded
      on the left with zeros.

2.3.  Specific Tunnel Types

   The following subsections describe how to handle flow specification
   for several specific tunnel types.

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2.3.1.  VXLAN

   The headers on a VXLAN [RFC7348] data packet are an outer Ethernet
   header, an outer IP header, a UDP header, the VXLAN header, and an
   inner Ethernet header.  This inner Ethernet header is frequently, but
   not always, followed by an inner IP header.  If the tunnel type is
   VXLAN, the I flag MUST be set in the Tunneled Traffic Flow
   Specification.

   If the outer Ethernet header is not being matched, the version (IPv4
   or IPv6) of the outer IP header is indicated by the AFI at the
   beginning of the multiprotocol MP_REACH_NLRI or MP_UNREACH_NLRI
   containing the Tunneled Traffic Flow Specification NLRI.  The outer
   Flowspec is used to filter the outer headers including, if desired,
   the UDP header.

   If the outer Ethernet header is being matched, then the initial AFI
   is 6 [FlowSpecL2] and the Outer Flowspec can match the outer Ethernet
   header, specify the IP version of the outer IP header, and match that
   IP header including, if desired, the UDP header.

   The Tunnel Header Flowspec can be used to filter on the VXLAN header
   VN ID (VNI).

   The Inner Flowspec can be used on the Inner Ethernet header
   [FlowSpecL2] and any following IP header.  If the inner AFI is 6,
   then the inner Flowspec provides filtering of the Layer 2 header,
   indicates whether filtering on a following IPv4 or IPv6 header is
   desired, and if it is desired provides the Flowspec components for
   that filtering.  If the Inner AFI is 1 or 2, the Inner Ethernet
   header is not matched and to match the Flowspec the Inner Ethernet
   header must be followed by an IPv4 or IPv6 header, respectively, and
   the inner Flowspec is used to filter that inner IP header.

   The inner MAC/IP address is associated with the VN ID.  In the NVO3
   terminating into a VPN scenario, if multiple access VN IDs map to one
   VPN instance, one shared VN ID can be carried in the flowspec rule to
   enforce the rule on the entire VPN instance and the shared VN ID and
   VPN correspondence should be configured on each VPN PE beforehand.
   In this case, the function of the Layer 3 VN ID is the same as a
   Route Distinguisher: it acts as the identification of the VPN
   instance.

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2.3.2.  VXLAN-GPE

   VXLAN-GPE [GPE] is similar to VXLAN.  The VXLAN-GPE header is the
   same size as the VXLAN header but has been extended from the VXLAN
   header by specifying a number of bits that are reserved in the VXLAN
   header.  In particular, a number of additional flag bits are
   specified and a Next Protocol field is added that is valid if the P
   flag bit is set in the VXLAN-GPE header.  These flags bits can be
   tested using the Tunnel Header Flags flowspec component defined
   above.  VXLAN and VXLAN-GPE are distinguished by the port number in
   the UDP header that precedes the VXLAN or VXLAN-GPE headers.

   If the VXLAN-GPE header P flag is zero, then that header is followed
   by the same sequence as for VXLAN and the same flowspec choices apply
   (see Section 2.3.1).

   If the VXLAN-GPE header P flag is one and that header's next protocol
   field is 1, then the VXLAN-GPE header is followed by an IPv4 header
   (there is no Inner Ethernet header).  The Inner Flowspec matches only
   if the Inner AFI is 1 and the Inner Flowspec matches.

   If the VXLAN-GPE header P flag is one and that header's next protocol
   field is 2, then the VXLAN-GPE header is followed by an IPv6 header
   (there is no Inner Ethernet header).  The Inner Flowspec match only
   if the Inner AFI is 2 and the Inner Flowspec matches.

2.3.3.  NVGRE

   NVGRE [RFC7637] is similar to VXLAN except that the UDP header and
   VXLAN header immediately after the outer IP header are replaced by a
   GRE (Generic Router Encapsulation) header.  The GRE header as used in
   NVGRE has no Checksum or Reserved1 field as shown in [RFC2890] but
   there are Virtual Subnet ID and Flow ID fields in place of what is
   labeled in [RFC2890] as the Key field.  Processing and restrictions
   for NVGRE are as in Section 2.3.1 eliminating references to a UDP
   header and replacing references to the VXLAN header and its VN ID
   with references to the GRE header and its VN ID (VSID) and Flow ID.

2.3.4.  L2TPv3

   The headers on an L2TPv3 [RFC3931] packets are an outer Ethernet
   header, an outer IP header, the L2TPv3 header, an inner Ethernet
   header, and possibly an inner IP header if indicated by the inner
   Ethernet header EtherType.  The Outer Flowspec operates on the outer
   headers that precede the L2TPv3 Session Header.  The version of IP in
   the outer IP header is specified by either the outer AFI at the
   beginning of the MP_REACH_NLRI or MP_UNREACH_NLRI or, if that AFI is
   6 (L2), optionally specified by the inner AFI within that L2

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   flowspec.

   L2TPv3 data messages and control messages both start with a Session
   ID and are distinguished by whether the Session ID is non-zero or
   zero, respectively.  Data message filtering is further specified in
   Section 2.3.4.1 and control message filtering is further specified in
   Section 2.3.4.2.

2.3.4.1.  L2TPv3 Data Messages

   For data messages, the L2TPv3 Session Header consists of a 32-bit
   non-zero Session ID followed by a variable length Cookie (maximum
   length 8 octets).  A Tunnel Header flowspec is assumed to apply to
   data messages unless the first component requires a zero Session ID.

   The Session ID and Cookie can be filtered on by using the Session and
   Cookie flowspec components in the Tunnel Header Flowspec.  To filter
   on Cookie or even be able to bypass Cookie and parse the remainder of
   the L2TPv3 packet, the node implementing tunneled traffic flowspec
   needs to know the length and/or value of the Cookie fields of
   interest.  This is negotiated at L2TPv3 session establishment and it
   is out of scope for this document how the node would learn this
   information.  Of course, if flowspec is being used for DDOS
   mitigation and the Cookie has a fixed length and/or value in the DDOS
   traffic, this could be learned by inspecting that traffic.

   If the I flag bit is zero, then no filtering is done on data beyond
   the L2TPv3 header.  If the I flag is one, indicating the presence of
   an Inner Flowspec, and the node implementing flowspec does not know
   the length of the L2TPv3 header Cookie, the match fails.  If that
   node does know the length of that Cookie, the Inner Flowspec if
   matched against the headers at the beginning of that data using the
   Inner AFI.  If that Inner AFI is 1 or 2, then an inner IP header is
   required and filtering can be done on that IPv4 or IPv6 header
   respectively.  If the Inner AFI is 6, filtering is done on the inner
   Ethernet header and, if an IPv4 or IPv6 inner AFI is specified within
   the inner L2 flowspec, done on the following IP header [FlowSpecL2].

2.3.4.2.  L2TPv3 Control Messages

   Control messages are distinguished by starting with a zero value
   32-bit Session ID.  L2TPv3 control message flowspecs MUST start with
   a Session component that requires Session to be zero.  For L2TPv3
   control messages, there is no Cookie but there are L2TPv3 flags, a
   3-bit Version field, a 32-bit Control Connection ID, and 16-bit Ns
   and Nr sequence numbers.  These can be tested using the Tunnel Header
   Flags, L2TP Control Version, L2TPv3 Control Connection ID, L2TPv3 Ns,
   and L2TPv3 Nr flowspec components in the Tunnel Header Flowspec.

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2.3.5.  GRE

   Generic Router Encapsulation (GRE [RFC2890]) is another type of
   encapsulation.  The Outer Flowspec operates on the outer headers that
   precede the GRE header.  The version of IP is specified by the outer
   AFI at the beginning of the MP_REACH_NLRI or MP_UNREACH_NLRI.

   The Tunnel Header Flags component can be used to match the first two
   octets of the GRE header.  The Protocol Type component can be used to
   match the corresponding GRE header field.  The Session and GRE
   Sequence components can be used to match on the GRE Key and GRE
   Sequence fields if those fields are present respectively.  If either
   of those fields is not present, a component to match on that field
   fails.

   If the I flag bit is zero, no filtering is done on data after the GRE
   header.  If the I flag bit is one in the tunnel flowspec, then there
   is an inner AFI and inner flowspec and the Protocol Type field of the
   GRE header must correspond to the Inner AFI as follows for the tunnel
   Flowspec to match.  Otherwise, the match fails.

                     +===================+===========+
                     | GRE Protocol Type | Inner AFI |
                     +===================+===========+
                     | 0x0800 (IPv4)     |     1     |
                     +-------------------+-----------+
                     | 0x86DD (IPv6)     |     2     |
                     +-------------------+-----------+
                     | 0x6558            |     6     |
                     +-------------------+-----------+

                                  Table 1

   With the I flag a one and the Inner AFI and GRE Protocol Type fields
   correspond, the Inner Flowspec is used to filter the inner IP headers
   (Inner AFI=1 or 2) or the inner Ethernet header and optionally a
   following IP header (Inner AFI=6).

2.3.6.  IP-in-IP

   IP-in-IP encapsulation [RFC2003] is indicated when an outer IP header
   indicates an inner IP IPv4 or IPv6 header by the value of the outer
   IP header's Protocol (IPv4) or Next Protocol (IPv6) field.

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   The IP version of the outer IP header (IPv4 or IPv6) matched is
   indicated by an AFI of 1 or 2 at the beginning of the MP_REACH_NLRI
   or MP_UNREACH_NLRI while if that AFI is 6, it indicates a match on
   the outer Ethernet header and, optionally, the following IP Header
   [FlowSpecL2].  The IP version of the inner IP header is indicated by
   the Inner AFI and the Inner Flowspec applies to the inner IP header.

   There is no tunnel header so there are no fields that can be matched
   by the Tunnel Header Flowspec in the case of IP-in-IP.

2.3.7.  Geneve

   The headers on a Geneve [RFC8926] encapsulated packet are an outer
   Ethernet header, an outer IP header, a UDP header, the Geneve header,
   and subsequent headers depending on the Geneve header Protocol Type
   field.

   If the outer Ethernet header is not being matched, the version (IPv4
   or IPv6) of the outer IP header is indicated by the AFI at the
   beginning of the multiprotocol MP_REACH_NLRI or MP_UNREACH_NLRI
   containing the Tunneled Traffic Flow Specification NLRI.  The outer
   Flowspec is used to filter the outer headers including, if desired,
   the UDP header.

   If the outer Ethernet header is being matched, then the initial AFI
   is 6 [FlowSpecL2] and the Outer Flowspec can match the outer Ethernet
   header, specify the IP version of the outer IP header, and match that
   IP header including, if desired, the UDP header.

   The Tunnel Header Flowspec can be used to filter on the Protocol Type
   field and/or the VNI field in the Geneve header.  The flags octet of
   the Geneve header, the second octet of that header, can be filtered
   using the Tunnel Header Flags component.

   If an Inner Flowspec is present, it is used to match the header(s)
   after the Geneve header.  The Protocol Type field in the Geneve
   header must correspond to the Inner AFI as shown in the table in
   Section 2.3.5 above or the match fails.  If the Inner AFI and GRE
   Protocol Type fields correspond, the Inner Flowspec is used to filter
   the inner IP headers (Inner AFI=1 or 2) or the inner Ethernet header
   and optionally a following IP header (Inner AFI=6).

2.4.  Tunneled Traffic Actions

   The traffic filtering actions previously specified in [RFC8955] and
   [FlowSpecL2] are used for tunneled traffic.  For Traffic Marking in
   NVO3, only the DSCP in the outer header can be modified.

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3.  Order of Traffic Filtering Rules

   The following rules determine which flowspec takes precedence where
   one or more are applicable and at least one of the applicable
   flowspecs is a tunneled traffic flowspec:

   *  In comparing an applicable tunneled traffic flow specification
      with an applicable non-tunneled flow specification, the tunneled
      specification has precedence.

   *  If comparing tunneled traffic flow specifications, if all are
      applicable, the tunnel types will be the same.  Any that have a
      Routing Distinguisher will take precedence over those without a
      Routing Distinguisher.  Of those with a Routing Distinguisher, all
      applicable flowspecs will have the same Routing Distinguisher.

   *  At this point in the process, all remaining contenders for the
      highest precedence will either not have a Routing Distinguisher or
      have equal Routing Distinguishers.  If more than one contender
      remain, those with an L2 Outer Flowspec take precedence over those
      with an L3 Outer Flowspec.  If the Outer Flowspec AFI is the same,
      their order of precedence is determined by comparing the Outer
      Flowspecs as described in [RFC8955] and [RFC8956] for AFI for 1 or
      2 respectively or [FlowSpecL2] for AFI=6.

   *  If the Outer Flowspecs are equal, then the Tunnel Header Flowspecs
      are compared using the usual sequential component comparison
      process [RFC8955].

   *  If the Tunnel Header Flowspecs are equal then compare the "I"
      flag.  Those with an Inner Flowspec take precedence over those
      without an Inner Flowspec.  If you get to this stage in the
      ordering process, those without an Inner Flowspec are equal.  For
      those with an Inner Flowspec, check the Inner AFI.  An L2 Inner
      AFI (AFI=6) takes precedence over an L3 Inner AFI.

   *  If the Inner AFIs are equal, precedence is determined by comparing
      the Inner Flowspecs as described in [FlowSpecL2] for L2 or
      [RFC8955] for L3.

4.  Flow Spec Validation

   Flowspecs received over AFI=1/SAFI=77 or AFI=2/SAFI=77 are validated,
   using only the Outer Flowspec, against routing reachability received
   over AFI=1/SAFI=133 and AFI=2/SAFI=133 respectively, as modified by
   [RFC9117].

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5.  Security Considerations

   No new security issues are introduced to the BGP protocol by this
   specification.

   For general Flowspec security considerations, see [RFC8955].

6.  IANA Considerations

   IANA has assigned the following SAFI:

          +=======+===========================+=================+
          | Value | Description               | Reference       |
          +=======+===========================+=================+
          | 77    | Tunneled Traffic Flowspec | [This document] |
          +-------+---------------------------+-----------------+

                                  Table 2

   IANA is requested to create a "Tunnel Header Flow Spec Component
   Type" registry on the Flow Spec Component Types registries web page
   as follows:

   Name:  Tunnel Flow Spec Component Types

   Reference:  [this document]

   Registration Procedures:
                    +---------+-------------------------+
                    |       0 | Reserved                |
                    +---------+-------------------------+
                    |   1-127 | Specification Required  |
                    +---------+-------------------------+
                    | 128-254 | First Come First Served |
                    +---------+-------------------------+
                    |     255 | Reserved                |
                    +---------+-------------------------+

                                   Table 3

   Initial contents:

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        +========+==============================+=================+
        | Type   | Name                         | Reference       |
        +========+==============================+=================+
        |      0 | reserved                     | [this document] |
        +--------+------------------------------+-----------------+
        |      1 | VN ID                        | [this document] |
        +--------+------------------------------+-----------------+
        |      4 | Cookie                       | [this document] |
        +--------+------------------------------+-----------------+
        |      5 | Tunnel Header Flags          | [this document] |
        +--------+------------------------------+-----------------+
        |      6 | L2TP Control Version         | [this document] |
        +--------+------------------------------+-----------------+
        |      7 | L2TPv3 Control Connection ID | [this document] |
        +--------+------------------------------+-----------------+
        |      8 | L2TPv3 Ns                    | [this document] |
        +--------+------------------------------+-----------------+
        |      9 | L2TPv3 Nr                    | [this document] |
        +--------+------------------------------+-----------------+
        |     10 | Protocol Type                | [this document] |
        +--------+------------------------------+-----------------+
        |     11 | GRE Sequence                 | [this document] |
        +--------+------------------------------+-----------------+
        | 12-254 | unassigned                   | [this document] |
        +--------+------------------------------+-----------------+
        |    255 | reserved                     | [this document] |
        +--------+------------------------------+-----------------+

                                  Table 4

7.  Normative References

   [FlowSpecL2]
              Hao, W., Eastlake, D., Litkowski, S., and S. Zhuang,
              "Dissemination of Flow Specification Rules for L2 VPN",
              Work in progress, <https://datatracker.ietf.org/doc/draft-
              ietf-idr-flowspec-l2vpn/>.

   [RFC2003]  Perkins, C., "IP Encapsulation within IP", RFC 2003,
              DOI 10.17487/RFC2003, October 1996,
              <https://www.rfc-editor.org/info/rfc2003>.

   [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>.

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   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

   [RFC2890]  Dommety, G., "Key and Sequence Number Extensions to GRE",
              RFC 2890, DOI 10.17487/RFC2890, September 2000,
              <https://www.rfc-editor.org/info/rfc2890>.

   [RFC3931]  Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
              "Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
              RFC 3931, DOI 10.17487/RFC3931, March 2005,
              <https://www.rfc-editor.org/info/rfc3931>.

   [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/info/rfc4271>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <https://www.rfc-editor.org/info/rfc7348>.

   [RFC7637]  Garg, P., Ed. and Y. Wang, Ed., "NVGRE: Network
              Virtualization Using Generic Routing Encapsulation",
              RFC 7637, DOI 10.17487/RFC7637, September 2015,
              <https://www.rfc-editor.org/info/rfc7637>.

   [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>.

   [RFC8926]  Gross, J., Ed., Ganga, I., Ed., and T. Sridhar, Ed.,
              "Geneve: Generic Network Virtualization Encapsulation",
              RFC 8926, DOI 10.17487/RFC8926, November 2020,
              <https://www.rfc-editor.org/info/rfc8926>.

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   [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>.

   [RFC8956]  Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed.,
              "Dissemination of Flow Specification Rules for IPv6",
              RFC 8956, DOI 10.17487/RFC8956, December 2020,
              <https://www.rfc-editor.org/info/rfc8956>.

   [RFC9117]  Uttaro, J., Alcaide, J., Filsfils, C., Smith, D., and P.
              Mohapatra, "Revised Validation Procedure for BGP Flow
              Specifications", RFC 9117, DOI 10.17487/RFC9117, August
              2021, <https://www.rfc-editor.org/info/rfc9117>.

8.  Informative References

   [GPE]      Maino, F., Kreeger, L., and U. Elzur, "Generic Protocol
              Extension for VXLAN", Work in progress, 26 March 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-nvo3-
              vxlan-gpe-12>.

   [RFC8014]  Black, D., Hudson, J., Kreeger, L., Lasserre, M., and T.
              Narten, "An Architecture for Data-Center Network
              Virtualization over Layer 3 (NVO3)", RFC 8014,
              DOI 10.17487/RFC8014, December 2016,
              <https://www.rfc-editor.org/info/rfc8014>.

Acknowledgments

   The authors wish to acknowledge the important contributions of the
   following listed in alphabetic order:

   Jeff Haas, Susan Hares, Yizhou Li, Qiandeng Liang, Greg Mirsky, Nan
   Wu, Robert Raszuk, and Lucy Yong

Authors' Addresses

   Donald E. Eastlake 3rd
   Futurewei Technologies
   2386 Panoramic Circle
   Apopka, Florida 32703
   United States of America
   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com, donald.eastlake@futurewei.com

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   Weiguo Hao
   Huawei Technologies
   101 Software Avenue
   Nanjing
   Jiangsu, 210012
   China
   Email: haoweiguo@huawei.com

   Shunwan Zhuang
   Huawei Technologies
   Huawei Building, No.156 Beiqing Road
   Beijing
   100095
   China
   Email: zhuangshunwan@huawei.com

   Zhenbin Li
   Huawei Technologies
   Huawei Building, No.156 Beiqing Road
   Beijing
   100095
   China
   Email: lizhenbin@huawei.com

   Rong Gu
   China Mobile
   Email: gurong_cmcc@outlook.com

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