BGP Dissemination of Flow Specification Rules for Tunneled Traffic
draft-ietf-idr-flowspec-nvo3-13

Document Type Active Internet-Draft (idr WG)
Authors Donald Eastlake  , Hao Weiguo  , Shunwan Zhuang  , Zhenbin Li  , Rong Gu 
Last updated 2021-02-22
Replaces draft-hao-idr-flowspec-nvo3
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Intended RFC status Proposed Standard
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INTERNET-DRAFT                                               D. Eastlake
Intended Status: Proposed Standard                Futurewei Technologies
                                                                  W. Hao
                                                               S. Zhuang
                                                                   Z. Li
                                                     Huawei Technologies
                                                                   R. Gu
                                                            China Mobile
Expires: August 21, 2021                               February 22, 2021

                          BGP Dissemination of
             Flow Specification Rules for Tunneled Traffic
                    draft-ietf-idr-flowspec-nvo3-13

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 Document

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Distribution of this document is unlimited. Comments should be sent
   to the authors or the IDR Working Group mailing list <idr@ietf.org>.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
   Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

D. Eastlake, et al                                              [Page 1]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

Table of Contents

      1. Introduction............................................3
      1.1 Terminology............................................3

      2. Tunneled Traffic Flow Specification NLRI................5
      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................................................9
      2.3.2 VXLAN-GPE...........................................10
      2.3.3 NVGRE...............................................11
      2.3.4 L2TPv3..............................................11
      2.3.4.1 L2TPv3 Data Messages..............................12
      2.3.4.2 L2TPv3 Control Messages...........................12
      2.3.5 GRE.................................................12
      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...................................16

      5. Security Considerations................................16
      6. IANA Considerations....................................17

      Normative References......................................18
      Informative References....................................19

      Acknowledgments...........................................20
      Authors' Addresses........................................20

D. Eastlake, et al                                              [Page 2]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

1. Introduction

   BGP Flow Specification (flowspec [RFC8955]) is an extension to BGP
   that supports the dissemination of traffic flow specification rules.
   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
   are suitable for matching 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.

D. Eastlake, et al                                              [Page 3]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

   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]

   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]

D. Eastlake, et al                                              [Page 4]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

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, any 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.

         +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
         | 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      :
         +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

D. Eastlake, et al                                              [Page 5]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

                    Figure 1. Tunneled Traffic Flowspec NLRI

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

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

   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].

D. Eastlake, et al                                              [Page 6]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

   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 that is present matches:
     - Inner Flowspec, and
     - 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 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

D. Eastlake, et al                                              [Page 7]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

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

         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.

    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

D. Eastlake, et al                                              [Page 8]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

         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.

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

D. Eastlake, et al                                              [Page 9]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

   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.

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 the
   precedes the VXLAN or VXLAN-GPE headers.

   If the VXLAN-GPE header P flag is zero, then that header is followed

D. Eastlake, et al                                             [Page 10]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

   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
   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.

D. Eastlake, et al                                             [Page 11]
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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.

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

D. Eastlake, et al                                             [Page 12]
INTERNET-DRAFT                                       BGP Tunnel Flowspec

   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

   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.

   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 out 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.

D. Eastlake, et al                                             [Page 13]
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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.

D. Eastlake, et al                                             [Page 14]
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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.

D. Eastlake, et al                                             [Page 15]
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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
   [FlowSpecOID].

5. Security Considerations

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

   For general Flowspec security considerations, see [RFC8955].

D. Eastlake, et al                                             [Page 16]
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6. IANA Considerations

   IANA has assigned the following SAFI:

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

   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

   Initial contents:
       Type     Name                Reference
      ------   --------------      -----------------
           0   reserved             [this document]
           1   VN ID                [this document]
           2   Flow ID              [this document]
           3   Session              [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]

D. Eastlake, et al                                             [Page 17]
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Normative References

   [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>.

   [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>.

D. Eastlake, et al                                             [Page 18]
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   [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>.

   [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>.

   [FlowSpecL2] - W. Hao, et al, "Dissemination of Flow Specification
         Rules for L2 VPN", draft-ietf-idr-flowspec-l2vpn, work in
         progress.

   [FlowSpecOID] - J. Uttaro, J. Alcaide, C. Filsfils, D. Smith, P.
         Mohapatra, "Revised Validation Procedure for BGP Flow
         Specifications", draft-ietf-idr-bgp-flowspec-oid, work in
         progress.

Informative References

   [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>.

   [GPE] - P. Quinn, et al, "Generic Protocol Extension for VXLAN",
         draft-ietf-nvo3-vxlan-gpe, work in progress.

D. Eastlake, et al                                             [Page 19]
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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 Eastlake
      Futurewei Technologies
      2386 Panoramic Circle
      Apopka, FL 32703 USA

      Tel: +1-508-333-2270
      Email: d3e3e3@gmail.com

      Weiguo Hao
      Huawei Technologies
      101 Software Avenue,
      Nanjing 210012 China

      Email: haoweiguo@huawei.com

      Shunwan Zhuang
      Huawei Technologies
      Huawei Bld., No.156 Beiqing Rd.
      Beijing  100095 China

      Email: zhuangshunwan@huawei.com

      Zhenbin Li
      Huawei Technologies
      Huawei Bld., No.156 Beiqing Rd.
      Beijing  100095 China

      Email: lizhenbin@huawei.com

      Rong Gu
      China Mobile

      Email: gurong_cmcc@outlook.com

D. Eastlake, et al                                             [Page 20]
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   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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D. Eastlake, et al                                             [Page 21]