IDR Working Group                                               C. Loibl
Internet-Draft                                 Next Layer Communications
Obsoletes: 5575,7674 (if approved)                              S. Hares
Intended status: Standards Track                                  Huawei
Expires: December 20, 2019 May 7, 2020                                           R. Raszuk
                                                            Bloomberg LP
                                                            D. McPherson
                                                                Verisign
                                                               M. Bacher
                                                        T-Mobile Austria
                                                           June 18,
                                                        November 4, 2019

               Dissemination of Flow Specification Rules
                      draft-ietf-idr-rfc5575bis-17
                      draft-ietf-idr-rfc5575bis-18

Abstract

   This document obsoletes both RFC5575 and RFC7674.

   This document defines a Border Gateway Protocol Network Layer
   Reachability Information (BGP NLRI) encoding format format, that can be used
   to distribute traffic Flow Specifications.  This allows the routing
   system to propagate information regarding more specific components of
   the traffic aggregate defined by an IP destination prefix.

   It also specifies IPv4 traffic Flow Specifications via a BGP NLRI which
   carries traffic Extended Community encoding formats, that can
   be used to propagate Traffic Filtering Actions along with the Flow
   Specification filter, and an Extended community
   value which encodes NLRI.  Those Traffic Filtering Actions encode actions a
   routing system can take if the packet matches the traffic flow filters.  The flow filters and the actions
   are processed in a fixed order.  Other drafts specify IPv6, MPLS
   addresses, L2VPN addresses, and NV03 encapsulation Flow Specification.

   Additionally, it defines two applications of IP addresses.

   This document obsoletes RFC5575 and RFC7674 that encoding format:
   one that can be used to correct unclear
   specifications in the flow filters.

   Applications which use the bgp Flow Specification are: 1) application
   which automate inter-domain coordination of traffic
   filtering, such as what is required in order to mitigate
   (distributed) denial-of-
   service attacks; 2) applications which control denial-of-service attacks, and a second application to
   provide traffic filtering in the context of a BGP/MPLS VPN service, and 3) service.
   Other applications with (ie. centralized control of traffic in a SDN or
   NFV context.  Some
   deployments of these three applications can be handled by the strict
   ordering of the BGP NLRI traffic flow filters, context) are also possible.  Other drafts specify IPv6, MPLS
   addresses, L2VPN addresses, and the strict actions
   encoded in the extended community NV03 encapsulation of IP addresses as
   Flow Specification actions. extensions.

   The information is carried via the BGP, thereby reusing protocol
   algorithms, operational experience, and administrative processes such
   as inter-provider peering agreements.

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 December 20, 2019. May 7, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definitions of Terms Used in This Memo  . . . . . . . . . . .   5
   3.  Flow Specifications . . . . . . . . . . . . . . . . . . . . .   6   5
   4.  Dissemination of IPv4 FLow Specification Information  . . . .   7   6
     4.1.  Length Encoding . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  NLRI Value Encoding . . . . . . . . . . . . . . . . . . .   8   7
       4.2.1.  Type 1 - Destination Prefix  Operators . . . . . . . . . . . . .   8
       4.2.2.  Type 2 - Source Prefix . . . . . . . . .   7
       4.2.2.  Components  . . . . . .   8
       4.2.3.  Type 3 - IP Protocol . . . . . . . . . . . . . . .   9
     4.3.  Examples of Encodings .   8
       4.2.4.  Type 4 - Port . . . . . . . . . . . . . . . . .  13
   5.  Traffic Filtering . . .  10
       4.2.5.  Type 5 - Destination Port . . . . . . . . . . . . . .  10
       4.2.6.  Type 6 - Source Port . . . . .  16
     5.1.  Ordering of Flow Specifications . . . . . . . . . . .  10
       4.2.7.  Type 7 - ICMP type . .  17
   6.  Validation Procedure  . . . . . . . . . . . . . . .  11
       4.2.8.  Type 8 - ICMP code . . . . .  18
   7.  Traffic Filtering Actions . . . . . . . . . . . .  11
       4.2.9.  Type 9 - TCP flags . . . . . .  19
     7.1.  Traffic Rate in Bytes (traffic-rate-bytes) sub-type 0x06   20
     7.2.  Traffic Rate in Packets (traffic-rate-packets) sub-type
           TBD . . . . . . . . . . .  11
       4.2.10. Type 10 - Packet length . . . . . . . . . . . . . . .  12
       4.2.11. Type 11 -  DSCP (Diffserv Code Point) .  21
     7.3.  Traffic-action (traffic-action) sub-type 0x07 . . . . . .  21
     7.4.  RT Redirect (rt-redirect) sub-type 0x08 .  12
       4.2.12. Type 12 - Fragment . . . . . . . .  22
     7.5.  Traffic Marking (traffic-marking) sub-type 0x09 . . . . .  22
     7.6.  Interaction with other Filtering Mechanisms in Routers  .  23
     7.7.  Considerations on Traffic Filtering Action Interference .  23
   8.  Dissemination of Traffic Filtering in BGP/MPLS VPN Networks .  24
   9.  Traffic Monitoring  .  12
     4.3.  Examples of Encodings . . . . . . . . . . . . . . . . . .  13
   5.  Traffic Filtering . .  25
   10. Error-Handling  . . . . . . . . . . . . . . . . . . . .  14
     5.1.  Ordering of Traffic Filtering Rules . . .  25
   11. Future NLRI Extensions  . . . . . . . .  15
   6.  Validation Procedure . . . . . . . . . . .  25
   12. IANA Considerations . . . . . . . . .  17
   7.  Traffic Filtering Actions . . . . . . . . . . . .  26
     12.1.  AFI/SAFI Definitions . . . . . .  18
     7.1.  Traffic Rate in Bytes (traffic-rate-bytes) sub-type 0x06   19
     7.2.  Traffic Rate in Packets (traffic-rate-packets) sub-type
           TBD . . . . . . . . . . . .  26
     12.2.  Flow Component Definitions . . . . . . . . . . . . . . .  20
     7.3.  Traffic-action (traffic-action) sub-type 0x07  26
     12.3.  Extended Community Flow Specification Actions  . . . . .  27
   13. Security Considerations .  20
     7.4.  RT Redirect (rt-redirect) sub-type 0x08 . . . . . . . . .  21
     7.5.  Traffic Marking (traffic-marking) sub-type 0x09 . . . . .  21
     7.6.  Considerations on Traffic Action Interference . . . .  30
   14. Contributors  . .  21
   8.  Dissemination of Traffic Filtering in BGP/MPLS VPN Networks .  22
     8.1.  Validation Procedures for BGP/MPLS VPNs . . . . . . . . .  23
     8.2.  Traffic Actions Rules . . . . . . . . . . . .  31
   15. Acknowledgements  . . . . . .  23
   9.  Limitations of Previous Traffic Filtering Efforts . . . . . .  23
     9.1.  Limitations in Previous DDoS Traffic Filtering Efforts .  23
     9.2.  Limitations in Previous BGP/MPLS Traffic Filtering
           Efforts . . . . . . . . .  31
   16. References  . . . . . . . . . . . . . . . .  24
   10. Traffic Monitoring . . . . . . . . .  32
     16.1.  Normative References . . . . . . . . . . . .  24
   11. Error-Handling and Future NLRI Extensions . . . . . . . . . .  24
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25
     12.1.  AFI/SAFI Definitions . . . . . . . . . . . . . . . . . .  25
     12.2.  Flow Component Definitions . . . . . . . . . . . . . . .  25
     12.3.  Extended Community Flow Specification Actions  . . . . .  26
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  29
   14. Operational Security Considerations . . . . . . . . . . . . .  30
   15. Original authors  . . . . . . . . . . . . . . . . . . . . . .  30
   16. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  30
   17. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     17.1.  Normative  32
     16.2.  Informative References . . . . . . . . . . . . . . . . . .  30
     17.2.  Informative References . . . .  33
     16.3.  URIs . . . . . . . . . . . . .  32
     17.3.  URIs . . . . . . . . . . . . .  34
   Appendix A.  Python code: flow_rule_cmp . . . . . . . . . . . . .  32  34
   Appendix A. B.  Comparison with RFC 5575 . . . . . . . . . . . . . .  32  36
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33  37

1.  Introduction

   This document obsoletes both
   "Dissemination of Flow Specification Rules" [RFC5575] and
   "Clarification of the Flowspec Redirect Extended Community"[RFC7674].

   Modern IP routers contain both the capability to forward traffic
   according to IP prefixes as well as to classify, shape, rate limit,
   filter, or redirect packets based on administratively defined
   policies.  These traffic policy mechanisms allow the router operator to
   define match rules that operate on multiple fields of the packet
   header.  Actions such as the ones described above can be associated
   with each rule.

   The n-tuple consisting of the matching criteria defines an aggregate
   traffic Flow Specification.  The matching criteria can include
   elements such as source and destination address prefixes, IP
   protocol, and transport protocol port numbers.

   This

   Section 4 of this document defines a general procedure to encode flow
   specification rules Flow
   Specification for aggregated traffic flows so that they can be
   distributed as a BGP [RFC4271] NLRI.  Additionally, we define Section 7 of this
   document defines the required Traffic Filtering Actions BGP Extended
   Communities and mechanisms to utilize this definition to the problem of
   immediate concern to the authors: use BGP for intra- and inter-provider
   distribution of traffic filtering rules to filter (distributed)
   denial-of-service (DoS) attacks.

   By expanding routing information with Flow Specifications, the
   routing system can take advantage of the ACL (Access Control List) or
   firewall capabilities in the router's forwarding path.  Flow
   specifications
   Specifications can be seen as more specific routing entries to a
   unicast prefix and are expected to depend upon the existing unicast
   data information.

   A Flow Specification received from an external autonomous system will
   need to be validated against unicast routing before being accepted. accepted
   (Section 6).  The flow specification received from an internal BGP
   peer within the same autonomous system (per [RFC4271]) is assumed to
   have been validated prior to transmission within the iBGP mesh of an
   autonomous system.  If the aggregate traffic flow defined by the
   unicast destination prefix is forwarded to a given BGP peer, then the
   local system can install more specific flow rules Flow Specifications that may
   result in different forwarding behavior, as requested by this system.

   The key technology components required to address the class of
   problems targeted by this document are:

   1.  Efficient point-to-multipoint distribution of control plane
       information.

   2.  Inter-domain capabilities and routing policy support.

   3.  Tight integration with unicast routing, for verification
       purposes.

   Items 1 and 2 have already been addressed using BGP for other types
   of control plane information.  Close integration with BGP also makes
   it feasible to specify a mechanism to automatically verify flow
   information against unicast routing.  These factors are behind the
   choice of BGP as the carrier of Flow Specification information.

   As with previous extensions to BGP, this specification makes it
   possible to add additional information to Internet routers.  These
   are limited in terms of the maximum number of data elements they can
   hold as well as the number of events they are able to process in a
   given unit of time.  The authors believe that, as with previous
   extensions, service providers will be careful to keep information
   levels below the maximum capacity of their devices.

   Experience with previous BGP extensions has also shown that the
   maximum capacity of BGP speakers has been gradually increased
   according to expected loads.  For example Internet unicast routing as
   well as other BGP applications increased their maximum capacity as
   they gain popularity.

   From an operational perspective, the utilization of BGP as the
   carrier for this information allows a network service provider to
   reuse both internal route distribution infrastructure (e.g., route
   reflector or confederation design) and existing external
   relationships (e.g., inter-domain BGP sessions to a customer
   network).

   While it is certainly possible to address this problem using other
   mechanisms, this solution has been utilized in deployments because of
   the substantial advantage of being an incremental addition to already
   deployed mechanisms.

   In current deployments, the information distributed by the flow-spec this extension
   is originated both manually as well as automatically.  The latter by
   systems that are able to detect malicious traffic flows.  When
   automated systems are used, care should be taken to ensure their
   correctness as well as to limit the number and advertisement rate limitations of
   flow routes. the systems that receive
   and process the advertised Flow Specifications (see also Section 13).

   This specification defines required protocol extensions to address
   most common applications of IPv4 unicast and VPNv4 unicast filtering.
   The same mechanism can be reused and new match criteria added to
   address similar filtering needs for other BGP address families such
   as IPv6 families [I-D.ietf-idr-flow-spec-v6], [I-D.ietf-idr-flow-spec-v6].

2.  Definitions of Terms Used in This Memo

   NLRI

   AFI -   Address Family Identifier.

   AS -   Autonomous System.

   Loc-RIB -   The Loc-RIB contains the routes that have been selected
      by the local BGP speaker's Decision Process.

   NLRI -   Network Layer Reachability Information.

   PE -   Provider Edge router.

   RIB -   Routing Information Base.

   Loc-RIB -   Local RIB.

   AS

   SAFI -   Autonomous System.   Subsequent Address Family Identifier.

   VRF -   Virtual Routing and Forwarding instance.

   PE -   Provider Edge router

   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.

3.  Flow Specifications

   A Flow Specification is an n-tuple consisting of several matching
   criteria that can be applied to IP traffic.  A given IP packet is
   said to match the defined flow Flow Specification if it matches all the
   specified criteria.  This n-tuple is encoded into a BGP NLRI defined
   below.

   A given flow Flow Specification may be associated with a set of
   attributes, depending on the particular application; such attributes
   may or may not include reachability information (i.e., NEXT_HOP).
   Well-known or AS-specific community attributes can be used to encode
   a set of predetermined actions.

   A particular application is identified by a specific (Address Family
   Identifier, Subsequent Address Family Identifier (AFI, SAFI)) pair
   [RFC4760] and corresponds to a distinct set of RIBs.  Those RIBs
   should be treated independently from each other in order to assure
   non-interference between distinct applications.

   BGP itself treats the NLRI as an a key to an entry in its databases.
   Entries that are placed in the Loc-RIB are then associated with a
   given set of semantics, which is application dependent.  This is
   consistent with existing BGP applications.  For instance, IP unicast
   routing (AFI=1, SAFI=1) and IP multicast reverse-path information
   (AFI=1, SAFI=2) are handled by BGP without any particular semantics
   being associated with them until installed in the Loc-RIB.

   Standard BGP policy mechanisms, such as UPDATE filtering by NLRI
   prefix as well as community matching and manipulation, MUST must apply to
   the Flow Specification defined NLRI-type, especially in an inter-
   domain environment.  Network operators can also control propagation
   of such routing updates by enabling or disabling the exchange of a
   particular (AFI, SAFI) pair on a given BGP peering session.

4.  Dissemination of IPv4 FLow Specification Information

   We define

   This document defines a "Flow Specification" Flow Specification NLRI type (Figure 1) that
   may include several components such as destination prefix, source
   prefix, protocol, ports, and others (see Section 4.2 below).

   This NLRI information is encoded using MP_REACH_NLRI and
   MP_UNREACH_NLRI attributes as defined in [RFC4760].  Whenever the
   corresponding application does not require Next-Hop Next Hop information, this
   shall be encoded as a 0-octet length Next Hop in the MP_REACH_NLRI
   attribute and (if a non 0-octet Next Hop is present it should be ignored
   on receipt. receipt).

   The NLRI field of the MP_REACH_NLRI and MP_UNREACH_NLRI is encoded as
   a 1- or 2-octet NLRI length field followed by a variable-length NLRI
   value.  The NLRI length is expressed in octets.

       +------------------------------+

                     +-------------------------------+
                     |    length (0xnn or 0xfn nn) 0xfnnn)    |
       +------------------------------+
                     +-------------------------------+
                     |    NLRI value   (variable)    |
       +------------------------------+
                     +-------------------------------+

                Figure 1: Flow-spec Flow Specification NLRI for IPv4

   Implementations wishing to exchange Flow Specification rules MUST use BGP's
   Capability Advertisement facility to exchange the Multiprotocol
   Extension Capability Code (Code 1) as defined in [RFC4760].  The
   (AFI, SAFI) pair carried in the Multiprotocol Extension Capability
   MUST be (AFI=1, SAFI=133) for IPv4 Flow Specification, and (AFI=1,
   SAFI=134) for VPNv4 Flow Specification.

4.1.  Length Encoding

   o  If the NLRI length value is smaller than 240 (0xf0 hex), hex) octets, the
      length field can be encoded as a single octet.

   o  Otherwise, it is encoded as an extended-length 2-octet value in
      which the most significant nibble of the first byte is all ones.

   In figure Figure 1 above, values less-than 240 are encoded using two hex
   digits (0xnn).  Values above 239 are encoded using 3 hex digits
   (0xfnnn).  The highest value that can be represented with this
   encoding is 4095.  The  For example the length value 241 of 239 is encoded as
   0xef (single octet) while 240 is encoded as 0xf0f1. 0xf0f0 (2-octet).

4.2.  NLRI Value Encoding

   The Flow Specification NLRI-type NLRI value consists of several a list of optional
   subcomponents.
   components and is encoded as follows:

   Encoding: <[component]+>

   A specific packet is considered to match the flow
   specification Flow Specification when
   it matches the intersection (AND) of all the components present in
   the specification.

   The encoding of each of the NLRI components begins with a type field
   (1 octet) followed by a variable length parameter.  Section 4.2.1 to
   Section 4.2.12 define component types and parameter encodings for the
   IPv4 IP layer and transport layer headers.  IPv6 NLRI component types
   are described in [I-D.ietf-idr-flow-spec-v6]. Flow Specification components Specification.

   Components must follow strict type ordering by increasing numerical
   order.  A given component type may (exactly once) or may not be
   present in the specification. Flow Specification.  If present, it MUST precede any
   component of higher numeric type value.

   All combinations of component types components within a single NLRI Flow Specification are allowed,
   even if the combination makes no sense from a semantical perspective.
   If a given component type within a prefix in unknown, the prefix in
   question
   allowed.  However, some combinations cannot match any packets (ie.
   "ICMP Type AND Port" will never match any packets), and thus SHOULD
   NOT be used for traffic filtering purposes propagated by BGP.

4.2.1.  Operators

   Most of the
   receiver.  Since a Flow Specification has the semantics components described below make use of a logical
   AND comparison
   operators.  Which of all components, if a component the two operators is used is FALSE, defined by definition it
   cannot be applied.  However, for the purposes of BGP route
   propagation, this prefix should still be transmitted since BGP route
   distribution is independent on NLRI semantics.

4.2.1.  Type 1 - Destination Prefix

      Encoding: <type (1 octet), prefix length (1 octet), prefix>

      Defines: the destination prefix to match.  Prefixes
   components in Section 4.2.2.  The operators are encoded as
      in BGP UPDATE messages, a length in bits is followed by enough
      octets to contain the prefix information.

4.2.2.  Type 2 - Source Prefix

      Encoding: <type (1 octet), prefix-length (1 octet), prefix>

      Defines the source prefix to match.

4.2.3.  Type 3 - IP Protocol

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

      Contains a set of {operator, value} pairs that are used to match
      the IP protocol value byte in IP packets.

      The single
   octet.

4.2.1.1.  Numeric Operator (numeric_op)

   This operator byte is encoded as: as shown in Figure 2.

                       0   1   2   3   4   5   6   7
                     +---+---+---+---+---+---+---+---+
                     | e | a |  len  | 0 |lt |gt |eq |
                     +---+---+---+---+---+---+---+---+

                  Figure 2: Numeric operator Operator (numeric_op)

   e -  end-of-list bit. bit: Set in the last {op, value} pair in the list.

   a -  AND bit. bit: If unset, the previous term is logically ORed with the
      current one.  If set, the operation is a logical AND.  In the
      first operator byte of a sequence it SHOULD be encoded as unset
      and and MUST be treated as always unset on decoding.  The AND
      operator has higher priority than OR for the purposes of
      evaluating logical expressions.

   len -  length: The length of the value field for this operator given
      as (1 << len).  This encodes 1 (00) - (len=00), 2 (len=01), 4 (len=10), 8 (11)
      (len=11) bytes.  Type 3 flow component
      values SHOULD be encoded as single byte (len = 00).

   0 -  SHOULD be set to 0 on NLRI encoding, and MUST be ignored during
      decoding

   lt -  less than comparison between data and value.

   gt -  greater than comparison between data and value.

   eq -  equality between data and value.

   The bits lt, gt, and eq can be combined to produce common relational
   operators such as "less or equal", "greater or equal", and "not equal
   to".
   to" as shown in Table 1.

            +----+----+----+----------------------------------+
            | lt | gt | eq | Resulting operation              |
            +----+----+----+----------------------------------+
            | 0  | 0  | 0  | false (independent of the value) |
            | 0  | 0  | 1  | == (equal)                       |
            | 0  | 1  | 0  | > (greater than)                 |
            | 0  | 1  | 1  | >= (greater than or equal)       |
            | 1  | 0  | 0  | < (less than)                    |
            | 1  | 0  | 1  | <= (less than or equal)          |
            | 1  | 1  | 0  | != (not equal value)             |
            | 1  | 1  | 1  | true (independent of the value)  |
            +----+----+----+----------------------------------+

                Table 1: Comparison operation combinations

4.2.4.  Type 4 - Port

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

      Defines a list of {operator, value} pairs that matches source OR
      destination TCP/UDP ports.

4.2.1.2.  Bitmask Operator (bitmask_op)

   This list operator is encoded using as shown in Figure 3.

                       0   1   2   3   4   5   6   7
                     +---+---+---+---+---+---+---+---+
                     | e | a |  len  | 0 | 0 |not| m |
                     +---+---+---+---+---+---+---+---+

                  Figure 3: Bitmask Operator (bitmask_op)

   e, a, len - Most significant nibble:  (end-of-list bit, AND bit, and
      length field), as defined in the numeric
      operator Numeric Operator format defined in
      Section 4.2.3.  Values SHOULD be
      encoded 4.2.1.1.

   not - NOT bit:  If set, logical negation of operation.

   m - Match bit:  If set, this is a bitwise match operation defined as 1- or 2-byte quantities.

      Port, source port, and destination port components evaluate
      "(data AND value) == value"; if unset, (data AND value) evaluates
      to
      FALSE TRUE if the IP protocol field any of the packet has a bits in the value other
      than TCP or UDP, if mask are set in the packet is fragmented data

   0 - all 0 bits:  SHOULD be set to 0 on NLRI encoding, and this is not MUST be
      ignored during decoding

4.2.2.  Components

   The encoding of each of the
      first fragment, or if components begins with a type field (1
   octet) followed by a variable length parameter.  The following
   sections define component types and parameter encodings for the system IPv4
   IP layer and transport layer headers.  IPv6 NLRI component types are
   described in unable to locate [I-D.ietf-idr-flow-spec-v6].

4.2.2.1.  Type 1 - Destination Prefix

   Encoding: <type (1 octet), length (1 octet), prefix (variable)>

   Defines the transport
      header.  Different implementations may or may not be able destination prefix to
      decode the transport header match.  The length and prefix
   fields are encoded as in BGP UPDATE messages [RFC4271]

4.2.2.2.  Type 2 - Source Prefix

   Encoding: <type (1 octet), length (1 octet), prefix (variable)>

   Defines the presence of IP options or
      Encapsulating Security Payload (ESP) NULL [RFC4303] encryption.

4.2.5. source prefix to match.  The length and prefix fields are
   encoded as in BGP UPDATE messages [RFC4271]

4.2.2.3.  Type 5 3 - Destination Port

      Encoding:<type IP Protocol

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

      Defines

   Contains a list of {operator, {numeric_op, value} pairs that are used to match
   the
      destination port of a TCP or UDP packet. IP protocol value byte in IP packet header (see [RFC0791]
   Section 3.1).

   This list is encoded
      using component uses the numeric operator format defined Numeric Operator (numeric_op) described in
   Section 4.2.3.
      Values 4.2.1.1.  Type 3 component values SHOULD be encoded as 1- or 2-byte quantities.

4.2.6. single
   byte (numeric_op len=00).

4.2.2.4.  Type 6 4 - Source Port

      Encoding:<type

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

   Defines a list of {operator, {numeric_op, value} pairs used to match that matches source OR
   destination TCP/UDP ports (see [RFC0793] Section 3.1 and [RFC0768]
   Section "Format").  This component matches if either the destination
   port OR the source port of a TCP or UDP packet. IP packet matches the value.

   This list is encoded using component uses the
      numeric operator format defined Numeric Operator (numeric_op) described in
   Section 4.2.3.  Values 4.2.1.1.  Type 4 component values SHOULD be encoded as 1- or
   2-byte quantities.

4.2.7. quantities (numeric_op len=00 or len=01).

   In case of the presence of the port (destination-port, source-port)
   component only TCP or UDP packets can match the entire Flow
   Specification.  The port component, if present, never matches when
   the packet's IP protocol value is not 6 (TCP) or 17 (UDP), if the
   packet is fragmented and this is not the first fragment, or if the
   system is unable to locate the transport header.  Different
   implementations may or may not be able to decode the transport header
   in the presence of IP options or Encapsulating Security Payload (ESP)
   NULL [RFC4303] encryption.

4.2.2.5.  Type 7 5 - ICMP type

      Encoding:<type Destination Port

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

   Defines a list of {operator, {numeric_op, value} pairs used to match the type
      field
   destination port of an ICMP packet. a TCP or UDP packet (see also [RFC0793]
   Section 3.1 and [RFC0768] Section "Format").

   This list is encoded using component uses the numeric
      operator format defined Numeric Operator (numeric_op) described in
   Section 4.2.3.  Values 4.2.1.1.  Type 5 component values SHOULD be encoded using a single byte. as 1- or
   2-byte quantities (numeric_op len=00 or len=01).

   The ICMP type specifiers evaluate last paragraph of Section 4.2.2.4 also applies to FALSE whenever the protocol
      value is not ICMP.

4.2.8. this component.

4.2.2.6.  Type 8 6 - ICMP code

      Encoding:<type Source Port

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

   Defines a list of {operator, {numeric_op, value} pairs used to match the code
      field source
   port of an ICMP packet. a TCP or UDP packet (see also [RFC0793] Section 3.1 and
   [RFC0768] Section "Format").

   This list is encoded using component uses the numeric
      operator format defined Numeric Operator (numeric_op) described in
   Section 4.2.3.  Values 4.2.1.1.  Type 6 component values SHOULD be encoded using a single byte. as 1- or
   2-byte quantities (numeric_op len=00 or len=01).

   The ICMP code specifiers evaluate last paragraph of Section 4.2.2.4 also applies to FALSE whenever the protocol
      value is not ICMP.

4.2.9. this component.

4.2.2.7.  Type 9 7 - TCP flags

      Encoding:<type ICMP type

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

      Bitmask values can be [numeric_op, value]+>

   Defines a list of {numeric_op, value} pairs used to match the type
   field of an ICMP packet (see also [RFC0792] Section "Message
   Formats").

   This component uses the Numeric Operator (numeric_op) described in
   Section 4.2.1.1.  Type 7 component values SHOULD be encoded as single
   byte (numeric_op len=00).

   In case of the presence of the ICMP type (code) component only ICMP
   packets can match the entire Flow Specification.  The ICMP type
   (code) component, if present, never matches when the packet's IP
   protocol value is not 1 (ICMP), if the packet is fragmented and this
   is not the first fragment, or if the system is unable to locate the
   transport header.  Different implementations may or may not be able
   to decode the transport header in the presence of IP options or
   Encapsulating Security Payload (ESP) NULL [RFC4303] encryption.

4.2.2.8.  Type 8 - ICMP code

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

   Defines a list of {numeric_op, value} pairs used to match the code
   field of an ICMP packet (see also [RFC0792] Section "Message
   Formats").

   This component uses the Numeric Operator (numeric_op) described in
   Section 4.2.1.1.  Type 8 component values SHOULD be encoded as single
   byte (numeric_op len=00).

   The last paragraph of Section 4.2.2.7 also applies to this component.

4.2.2.9.  Type 9 - TCP flags

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

   Defines a list of {bitmask_op, bitmask} pairs used to match TCP
   Control Bits (see also [RFC0793] Section 3.1).

   This component uses the Bitmask Operator (bitmask_op) described in
   Section 4.2.1.2.  Type 9 component bitmasks MUST be encoded as 1- or
   2-byte bitmask. bitmask (bitmask_op len=00 or len=01).

   When a single byte (bitmask_op len=00) is specified, it matches byte 13
   14 of the TCP header
      [RFC0793], (see also [RFC0793] Section 3.1), which contains bits 8 though 15 of
   the 4th 32-bit word. TCP Control Bits.  When a 2-byte (bitmask_op len=01) encoding is
   used, it matches bytes 12 and 13 and 14 of the TCP header with the data
   offset field having a "don't care" value.

      This (leftmost 4 bits) always treated as 0.

   In case of the presence of the TCP flags component evaluates to FALSE for packets that are not only TCP
      packets.

      This type uses the bitmask operator format, which differs from packets
   can match the
      numeric operator format in entire Flow Specification.  The TCP flags component, if
   present, never matches when the lower nibble.

    0   1   2   3   4   5 packet's IP protocol value is not 6   7
   +---+---+---+---+---+---+---+---+
   | e | a |  len  | 0 | 0 |not| m |
   +---+---+---+---+---+---+---+---+

      Bitmask operator

   e, a, len - Most significant nibble:  (end-of-list bit, AND bit, and
      length field), as defined for in
   (TCP), if the numeric operator format in
      Section 4.2.3.

   not - NOT bit.  If set, logical negation of operation.

   m -   Match bit.  If set, packet is fragmented and this is a bitwise match operation defined
      as "(data AND value) == value"; not the first
   fragment, or if unset, (data AND value)
      evaluates the system is unable to TRUE if any of locate the bits in transport header.
   Different implementations may or may not be able to decode the value mask are set
   transport header in the data

   0 -   all 0 bits  SHOULD be set to 0 on NLRI encoding, and MUST be
      ignored during decoding

4.2.10. presence of IP options or Encapsulating
   Security Payload (ESP) NULL [RFC4303] encryption.

4.2.2.10.  Type 10 - Packet length

      Encoding:<type

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

   Defines a list of {operator, {numeric_op, value} pairs used to match on the
   total IP packet length (excluding Layer 2 but including IP header).

   This list is encoded using component uses the numeric operator format
      defined Numeric Operator (numeric_op) described in
   Section 4.2.3.  Values 4.2.1.1.  Type 10 component values SHOULD be encoded using as 1- or
   2-byte quantities.

4.2.11. quantities (numeric_op len=00 or len=01).

4.2.2.11.  Type 11 - DSCP (Diffserv Code Point)

      Encoding:<type

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

   Defines a list of {operator, {numeric_op, value} pairs used to match the 6-bit
   DSCP field [RFC2474]. (see also [RFC2474]).

   This list is encoded using component uses the numeric
      operator format defined Numeric Operator (numeric_op) described in
   Section 4.2.3.  Values SHOULD 4.2.1.1.  Type 11 component values MUST be encoded using a as single byte.
   byte (numeric_op len=00).

   The six least significant bits contain the DSCP value.  All other
   bits SHOULD be encoded treated as zero
      and ignored on decoding.

4.2.12. 0.

4.2.2.12.  Type 12 - Fragment

      Encoding:<type

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

      Uses bitmask operator format defined in Section 4.2.9.

      0   1   2   3   4   5   6   7
    +---+---+---+---+---+---+---+---+
    | 0 |

   Defines a list of {bitmask_op, bitmask} pairs used to match specific
   IP fragments.

   This component uses the Bitmask Operator (bitmask_op) described in
   Section 4.2.1.2.  The Type 12 component bitmask MUST be encoded as
   single byte bitmask (bitmask_op len=00).

                      0   1   2   3   4   5   6   7
                    +---+---+---+---+---+---+---+---+
                    | 0 | 0 | 0 | 0 |LF |FF |IsF|DF |
                    +---+---+---+---+---+---+---+---+

                    Figure 4: Fragment Bitmask Operand

   Bitmask values:

         Bit 7

   DF -  Don't fragment - match if [RFC0791] IP Header Flags Bit-1 (DF)

         Bit 6
      is 1

   IsF -  Is a fragment (IsF)

         Bit 5 - match if [RFC0791] IP Header Fragment Offset
      is not 0

   FF -  First fragment (FF)

         Bit 4 - match if [RFC0791] IP Header Fragment Offset
      is 0 AND Flags Bit-2 (MF) is 1

   LF -  Last fragment (LF)

         Bit 0-3 - match if [RFC0791] IP Header Fragment Offset is
      not 0 AND Flags Bit-2 (MF) is 0

   0 -  SHOULD be set to 0 on NLRI encoding, and MUST be ignored during
      decoding

4.3.  Examples of Encodings

4.3.1.  Example 1

   An example of a Flow Specification NLRI encoding for: "all packets to
   10.0.1/24
   192.0.2.0/24 and TCP port 25".

      +------------------+----------+----------+

          +--------+----------------+----------+----------+
          | length | destination    | proto protocol | port     |
      +------------------+----------+----------+
          +--------+----------------+----------+----------+
          | 0x01 0x0b   | 01 18 0a c0 00 01 02 | 03 81 06 | 04 81 19 |
      +------------------+----------+----------+

   Decode for protocol:

      +-------+----------+------------------------------+
          +--------+----------------+----------+----------+

   Decoded:

          +-------+------------+------------------------------+
          | Value |            |                              |
      +-------+----------+------------------------------+
          +-------+------------+------------------------------+
          |  0x0b | length     | 11 octets (len<240 1-octet)  |
          |  0x01 | type       | Type 1 - Destination Prefix  |
          |  0x18 | length     | 24 bit                       |
          |  0xc0 | prefix     | 192                          |
          |  0x00 | prefix     | 0                            |
          |  0x02 | prefix     | 2                            |
          |  0x03 | type       | Type 3 - IP Protocol         |
          |  0x81 | operator numeric_op | end-of-list, value size=1, = |
          |  0x06 | value      | IP Protocol 6 = TCP          |
          |  0x04 | type       | Type 4 - Port                |
          |  0x81 | numeric_op | end-of-list, value size=1, = |
          |  0x19 | value      | 25                           |
      +-------+----------+------------------------------+
          +-------+------------+------------------------------+

   This constitutes a NLRI with a NLRI length of 11 octets.

4.3.2.  Example 2

   An example of a Flow Specification NLRI encoding for: "all packets to
   10.1.1/24
   192.0.2.0/24 from 192/8 203.0.113.0/24 and port {range [137, 139] or
   8080}".

      +------------------+----------+-------------------------+

  +--------+----------------+----------------+-------------------------+
  | length | destination    | source         | port                    |
      +------------------+----------+-------------------------+
  +--------+----------------+----------------+-------------------------+
  |  0x12  | 0x01 18 0a 01 01 18 c0 00 02 | 02 08 c0 18 cb 00 71 | 04 03 89 45 8b 91 1f 90 |
      +------------------+----------+-------------------------+

   Decode for port:

      +--------+----------+------------------------------+
  +--------+----------------+----------------+-------------------------+

   Decoded:

          +--------+------------+------------------------------+
          | Value  |            |                              |
      +--------+----------+------------------------------+
          +--------+------------+------------------------------+
          |   0x04 | type   0x12 | length     | 18 octets (len<240 1-octet)  |   0x03
          | operator   0x01 | size=1, >= type       | Type 1 - Destination Prefix  |   0x89
          | value   0x18 | 137 length     | 24 bit                       |   0x45
          | operator   0xc0 | "AND", value size=1, <= prefix     | 192                          |   0x8b
          | value   0x00 | 139 prefix     | 0                            |   0x91
          | operator   0x02 | end-of-list, value-size=2, = prefix     | 2                            | 0x1f90
          | value   0x02 | 8080 type       |
      +--------+----------+------------------------------+

   This constitutes an Type 2 - Source Prefix       |
          |   0x18 | length     | 24 bit                       |
          |   0xcb | prefix     | 203                          |
          |   0x00 | prefix     | 0                            |
          |   0x71 | prefix     | 113                          |
          |   0x04 | type       | Type 4 - Port                |
          |   0x03 | numeric_op | value size=1, >=             |
          |   0x89 | value      | 137                          |
          |   0x45 | numeric_op | "AND", value size=1, <=      |
          |   0x8b | value      | 139                          |
          |   0x91 | numeric_op | end-of-list, value size=2, = |
          | 0x1f90 | value      | 8080                         |
          +--------+------------+------------------------------+

   This constitutes a NLRI with an a NLRI length of 16 18 octets.

4.3.3.  Example 3

   An example of a Flow Specification NLRI encoding for: "all packets to
   192.0.2.1/32 and fragment { DF or FF } (matching packet with DF bit
   set or First Fragments)

          +--------+-------------------+----------+
          | length | destination       | fragment |
          +--------+-------------------+----------+
          |  0x09  | 01 20 c0 00 02 01 | 0c 80 05 |
          +--------+-------------------+----------+

   Decoded:

          +-------+------------+------------------------------+
          | Value |            |                              |
          +-------+------------+------------------------------+
          |  0x09 | length     | 9 octets (len<240 1-octet)   |
          |  0x01 | type       | Type 1 - Destination Prefix  |
          |  0x20 | length     | 32 bit                       |
          |  0xc0 | prefix     | 192                          |
          |  0x00 | prefix     | 0                            |
          |  0x02 | prefix     | 2                            |
          |  0x01 | prefix     | 1                            |
          |  0x0c | type       | Type 12 - Fragment           |
          |  0x80 | bitmask_op | end-of-list, value size=1    |
          |  0x05 | bitmask    | DF=1, FF=1                   |
          +-------+------------+------------------------------+

   This constitutes a NLRI with a NLRI length of 9 octets.

5.  Traffic Filtering

   Traffic filtering policies have been traditionally considered to be
   relatively static.  Limitations of the these static mechanisms caused
   this new dynamic mechanism to be designed for the three new
   applications of traffic
   filtering (prevention filtering:

   o  Prevention of traffic-based, denial-of-service (DOS)
   attacks, traffic attacks.

   o  Traffic filtering in the context of BGP/MPLS VPN service,
   and centralized service.

   o  Centralized traffic control for SDN/NFV networks) requires networks.

   These applications require coordination among service providers and/or and/
   or coordination among the AS within a service provider.  Section 9 has details on the limitation
   of previous mechanisms and why BGP Flow Specification provides a
   solution for to prevent DOS and aid BGP/MPLS VPN filtering rules.

   This

   The Flow Specification NLRI defined above to convey in Section 4 conveys information
   about traffic filtering rules for traffic that should be discarded or
   handled in a manner specified by a set of pre-defined actions (which
   are defined in BGP Extended Communities).  This mechanism is
   primarily designed to allow an upstream autonomous system to perform
   inbound filtering in their ingress routers of traffic that a given
   downstream AS wishes to drop.

   In order to achieve this goal, this draft specifies two application
   specific NLRI identifiers that provide traffic filters, and a set of
   actions encoding in BGP Extended Communities.  The two application
   specific NLRI identifiers are:

   o  IPv4 Flow Specification identifier (AFI=1, SAFI=133) along with
      specific semantic rules for IPv4 routes, and

   o  VPNv4 Flow Specification identifier (AFI=1, SAFI=134) value, which
      can be used to propagate traffic filtering information in a BGP/
      MPLS VPN environment.

   Distribution

   Encoding of the IPv4 Flow Specification NLRI is described in Section 6, and distibution of BGP/MPLS traffic 4 for IPv4 Flow
   Specification is
   described and in Section 8. 8 for VPNv4 Flow Specification.  The traffic
   filtering actions are described in Section 7.

5.1.  Ordering of Traffic Filtering Rules

   With traffic filtering rules, more Flow Specifications

   More than one rule Flow Specification may match a particular traffic flow.
   Thus, it is necessary to define the order
   at in which rules Flow
   Specifications get matched and actions being applied to a particular
   traffic flow.  This ordering function must be is such that it must does not depend
   on the arrival order of the Flow Specification's rules Specification via BGP and must be thus is
   consistent in the network.

   The relative order of two Flow Specification rules Specifications is determined by
   comparing their respective components.  The algorithm starts by
   comparing the left-most components (lowest component type value) of
   the rules. Flow Specifications.  If the types differ, the rule Flow Specification
   with lowest numeric type value has higher precedence (and thus will
   match before) than the rule Flow Specification that doesn't contain that
   component type.  If the component types are the same, then a type-
   specific comparison is performed (see below) if the types are equal
   the algorithm continues with the next component.

   For IP prefix values (IP destination or source prefix): If one of the
   two prefixes overlap, to compare is a more specific prefix of the one with other, the longer prefix-length
   more specific prefix has higher precedence.  If they do not overlap  Otherwise the one with
   the lowest IP value has higher precedence.

   For all other component types, unless otherwise specified, the
   comparison is performed by comparing the component data as a binary
   string using the memcmp() function as defined by the ISO C standard. [ISO_IEC_9899].  For
   strings with equal lengths the lowest string (memcmp) has higher
   precedence.  For strings of different lengths, the common prefix is
   compared.  If the common prefix is not equal the string with the
   lowest prefix has higher precedence.  If the common prefix is equal,
   the longest string is considered to have higher precedence than the
   shorter one.

   The code below in Appendix A shows a Python3 implementation of the
   comparison algorithm.  The full code was tested with Python 3.6.3 and
   can be obtained at https://github.com/stoffi92/flowspec-cmp [1].

   <CODE BEGINS>
   import itertools
   import ipaddress

   def flow_rule_cmp(a, b):
       for comp_a, comp_b in itertools.zip_longest(a.components,
                                              b.components):
           # If

6.  Validation Procedure

   Flow Specifications received from a component type does not exist BGP peer that are accepted in one rule
           # this rule has lower precedence
           if not comp_a:
               return B_HAS_PRECEDENCE
           if not comp_b:
               return A_HAS_PRECEDENCE
           # higher precedence for lower component type
           if comp_a.component_type < comp_b.component_type:
               return A_HAS_PRECEDENCE
           if comp_a.component_type > comp_b.component_type:
               return B_HAS_PRECEDENCE
           # component types the
   respective Adj-RIB-In are equal -> type specific comparison
           if comp_a.component_type used as input to the route selection
   process.  Although the forwarding attributes of two routes for the
   same Flow Specification prefix may be the same, BGP is still required
   to perform its path selection algorithm in (IP_DESTINATION, IP_SOURCE):
               # assuming comp_a.value, comp_b.value of type ipaddress
               if comp_a.value.overlaps(comp_b.value):
                   # longest prefixlen has precedence
                   if comp_a.value.prefixlen > comp_b.value.prefixlen:
                       return A_HAS_PRECEDENCE
                   if comp_a.value.prefixlen < comp_b.value.prefixlen:
                       return B_HAS_PRECEDENCE
                   # components equal -> continue with next component
               elif comp_a.value > comp_b.value:
                   return B_HAS_PRECEDENCE
               elif comp_a.value < comp_b.value:
                   return A_HAS_PRECEDENCE
           else:
               # assuming comp_a.value, comp_b.value of type bytearray
               if len(comp_a.value) == len(comp_b.value):
                   if comp_a.value > comp_b.value:
                       return B_HAS_PRECEDENCE
                   if comp_a.value < comp_b.value:
                       return A_HAS_PRECEDENCE
                   # components equal -> continue with next component
               else:
                   common = min(len(comp_a.value), len(comp_b.value))
                   if comp_a.value[:common] > comp_b.value[:common]:
                       return B_HAS_PRECEDENCE
                   elif comp_a.value[:common] < comp_b.value[:common]:
                       return A_HAS_PRECEDENCE
                   # the first common bytes match
                   elif len(comp_a.value) > len(comp_b.value):
                       return A_HAS_PRECEDENCE
                   else:

                       return B_HAS_PRECEDENCE
       return EQUAL
   <CODE ENDS>

6.  Validation Procedure

   Flow Specifications received from a BGP peer that are accepted in the
   respective Adj-RIB-In are used as input to the route selection
   process.  Although the forwarding attributes of two routes for the
   same Flow Specification prefix may be the same, BGP is still required
   to perform its path selection algorithm in order to select the
   correct set order to select the
   correct set of attributes to advertise.

   The first step of the BGP Route Selection procedure (Section 9.1.2 of
   [RFC4271] is to exclude from the selection procedure routes that are
   considered non-feasible.  In the context of IP routing information,
   this step is used to validate that the NEXT_HOP attribute of a given
   route is resolvable.

   The concept can be extended, in the case of the Flow Specification
   NLRI, to allow other validation procedures.

   A

   The validation process described below validates Flow Specifications
   against unicast routes received over the same AFI but the associated
   unicast routing information SAFI:

      Flow specification received over SAFI=133 will be validated
      against routes received over SAFI=1

      Flow specification received over SAFI=134 will be validated
      against routes received over SAFI=128

   By default a Flow Specification NLRI must MUST be validated such that it
   is considered feasible if and only if all of the below is true:

      a) A destination prefix component is embedded in the Flow
      Specification.

      b) The originator of the Flow Specification matches the originator
      of the best-match unicast route for the destination prefix
      embedded in the Flow Specification. Specification (this is the unicast route with
      the longest possible prefix length covering the destination prefix
      embedded in the Flow Specification).

      c) There are no more specific unicast routes, when compared with
      the flow destination prefix, that has have been received from a
      different neighboring AS than the best-match unicast route, which
      has been determined in rule b).

   Rule

   However, rule a) MAY be relaxed by explicit configuration, permitting
   Flow Specifications that include no destination prefix component.  If
   such is the case, rules b) and c) are moot and MUST be disregarded.

   By originator of a BGP route, we mean either the BGP address of the
   originator path
   attribute, as used by route reflection, in the ORIGINATOR_ID Attribute [RFC4456], or the transport source IP
   address of the BGP peer, if this path attribute is not present.

   BGP implementations MUST also enforce that the AS_PATH attribute of a
   route received via the External Border Gateway Protocol (eBGP)
   contains the neighboring AS in the left-most position of the AS_PATH
   attribute.  While this rule is optional in the BGP specification, it
   becomes necessary to enforce it for security reasons.

   The best-match unicast route may change over the time independently
   of the Flow Specification NLRI.  Therefore, a revalidation of the
   Flow Specification NLRI MUST be performed whenever unicast routes
   change.  Revalidation is defined as retesting that clause a and
   clause b above are true.

   Explanation:

   The underlying concept is that the neighboring AS that advertises the
   best unicast route for a destination is allowed to advertise flow-
   spec Flow
   Specification information that conveys a more or equally specific
   destination prefix.  Thus, as long as there are no more specific
   unicast routes, received from a different neighboring AS, which would
   be affected by that filtering rule. Flow Specification.

   The neighboring AS is the immediate destination of the traffic
   described by the Flow Specification.  If it requests these flows to
   be dropped, that request can be honored without concern that it
   represents a denial of service in itself.  Supposedly, the traffic is
   being dropped by the downstream autonomous system, and there is no
   added value in carrying the traffic to it.

7.  Traffic Filtering Actions

   This specification document defines a minimum set of filtering actions Traffic Filtering Actions that
   it standardizes as BGP extended community values [RFC4360].  This is
   not meant to be an inclusive list of all the possible actions, but
   only a subset that can be interpreted consistently across the
   network.  Additional actions can be defined as either requiring
   standards or as vendor specific.

   Implementations SHOULD provide mechanisms that map an arbitrary BGP
   community value (normal or extended) to filtering actions that
   require different mappings in different systems in the network.  For
   instance, providing packets with a worse-than-best-effort, per-hop
   behavior is a functionality that is likely to be implemented
   differently in different systems and for which no standard behavior
   is currently known.  Rather than attempting to define it here, this
   can be accomplished by mapping a user-defined community value to
   platform-/network-specific behavior via user configuration.

   The default action for a traffic filtering matching Flow Specification is to accept IP traffic that matches that particular rule. the
   packet (treat the packet according to the normal forwarding behaviour
   of the system).

   This document defines the following extended communities values shown
   in Table 2 in the form 0x8xnn 0xttss where nn tt indicates the type and ss
   indicates the sub-type. sub-type of the extended community.  Encodings for
   these extended communities are described below.

   +-----------+----------------------+--------------------------------+

   +--------------+--------------------------+-------------------------+
   | community    | action                   | encoding                |
   +-----------+----------------------+--------------------------------+
   | 0xttss       |                          |                         |
   +--------------+--------------------------+-------------------------+
   | 0x8006       | traffic-rate-bytes       | 2-byte ASN, 4-byte      |
   |              | (Section 7.1)            | float                   |
   | TBD          | traffic-rate-packets     | 2-byte ASN, 4-byte      |
   |              | (Section 7.1)            | float                   |
   | 0x8007       | traffic-action (Section  | bitmask                 |
   |              | 7.3)                     |                         |
   | 0x8008       | rt-redirect AS-2byte     | 2-octet AS, 4-octet     |
   |              | (Section 7.4)            | value                   |
   | 0x8108       | rt-redirect IPv4         | 4-octet IPv4 addres, 2-octet address,   |
   |              | (Section 7.4)            | 2-octet value           |
   | 0x8208       | rt-redirect AS-4byte     | 4-octet AS, 2-octet     |
   |              | (Section 7.4)            | value                   |
   | 0x8009       | traffic-marking (Section | DSCP value              |
   +-----------+----------------------+--------------------------------+
   |              | 7.5)                     |                         |
   +--------------+--------------------------+-------------------------+

          Table 2: Traffic Filtering Action Extended Communities

   Some

   Multiple Traffic Filtering Actions defined in this document may be
   present for a single Flow Specification and SHOULD be applied to the
   traffic action communities flow (for example traffic-rate-bytes and rt-redirect can be
   applied to packets at the same time).  If not all of the Traffic
   Filtering Actions can be applied to a traffic flow they should be
   treated as interfering Traffic filtering actions (see below).

   Some Traffic Filtering Actions may interfere with each other. other even
   contradict.  Section 7.6 7.7 of this specification document provides general
   considerations on such traffic action Traffic Filtering Action interference.  Any
   additional definition of a
   traffic actions specified by additional standards documents or vendor
   documents MUST Traffic Filtering Actions SHOULD specify if the traffic
   action interacts to take if those Traffic Filtering Actions interfere (also
   with an existing traffic actions, and provide error handling per [RFC7606].

   Multiple traffic actions may be present for a single NLRI.  The
   traffic actions are processed in ascending order of the sub-type
   found in the BGP Extended Communities.  If not all of them can be
   processed the filter SHALL NOT be applied at all (for example: if for
   a given flow there are the action communities rate-limit-bytes and
   traffic-marking attached, and the plattform does not support one of
   them also the other shall not be applied for that flow). Traffic Filtering Actions).

   All traffic actions Traffic Filtering Actions are specified as transitive BGP
   Extended Communities.

7.1.  Traffic Rate in Bytes (traffic-rate-bytes) sub-type 0x06

   The traffic-rate-bytes extended community uses the following extended
   community encoding:

   The first two octets carry the 2-octet id, which can be assigned from
   a 2-byte AS number.  When a 4-byte AS number is locally present, the
   2 least significant bytes of such an AS number can be used.  This
   value is purely informational and SHOULD NOT be interpreted by the
   implementation.

   The remaining 4 octets carry the maximum rate information in IEEE
   floating point [IEEE.754.1985] format, units being bytes per second.
   A traffic-rate of 0 should result on all traffic for the particular
   flow to be discarded.  On encoding the traffic-rate MUST NOT be
   negative.  On decoding negative values MUST be treated as zero
   (discard all traffic).

   Interferes with: No other BGP Flow Specification traffic action Traffic Filtering
   Action in this document.

7.2.  Traffic Rate in Packets (traffic-rate-packets) sub-type TBD

   The traffic-rate-packets extended community uses the same encoding as
   the traffic-rate-bytes extended community.  The floating point value
   carries the maximum packet rate in packets per second.  A traffic-
   rate-packets of 0 should result in all traffic for the particular
   flow to be discarded.  On encoding the traffic-rate-packets MUST NOT
   be negative.  On decoding negative values MUST be treated as zero
   (discard all traffic).

   Interferes with: No other BGP Flow Specification traffic action Traffic Filtering
   Action in this document.

7.3.  Traffic-action (traffic-action) sub-type 0x07

   The traffic-action extended community consists of 6 bytes of which
   only the 2 least significant bits of the 6th byte (from left to
   right) are currently defined.

        40  41  42  43  44  45  46  47
       +---+---+---+---+---+---+---+---+
       |        reserved defined by this document as shown in Figure 5.

      0                   1                   2                   3
      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | S Traffic Action Field                                          | T
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |
       +---+---+---+---+---+---+---+---+ Tr. Action Field (cont.)  |S|T|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 5: Traffic-action Extended Community Encoding

   where S and T are defined as:

   o  T: Terminal Action (bit 47): When this bit is set, the traffic
      filtering engine will apply evaluate any subsequent filtering rules Flow Specifications
      (as defined by the ordering procedure).  If not set, the
      evaluation of the traffic filter filters stops when this rule Flow
      Specification is applied. evaluated.

   o  S: Sample (bit 46): Enables traffic sampling and logging for this
      Flow Specification. Specification (only effective when set).

   o  reserved: should always be set to 0 by the originator and not be
      evaluated by the receiving BGP speaker.  Traffic Action Field: Other Traffic Action Field (see Section 12)
      bits unused in this specification.

   The use of the Terminal Action (bit 47) may result in more than one
   filter-rule
   Flow Specification matching a particular traffic flow.  All the flow actions
   Traffic Filtering Actions from these rules Flow Specifications shall be
   collected and applied.  In case of interfering
   traffic actions Traffic Filtering
   Actions it is an implementation decision which actions Traffic Filtering
   Actions are selected.  See also Section 7.6. 7.7.

   Interferes with: No other BGP Flow Specification traffic action Traffic Filtering
   Action in this document.

7.4.  RT Redirect (rt-redirect) sub-type 0x08

   The redirect extended community allows the traffic to be redirected
   to a VRF routing instance that lists the specified route-target in
   its import policy.  If several local instances match this criteria,
   the choice between them is a local matter (for example, the instance
   with the lowest Route Distinguisher value can be elected).

   This
   extended community Extended Community allows 3 different encodings formats for the
   route-target (type 0x80, 0x81, 0x82).  Is  It uses the same encoding as
   the Route Target extended community [RFC4360].

   It should be noted that the low-order nibble of the Redirect's Type
   field corresponds to the Route Target Extended Community format field
   (Type).  (See in Sections 3.1, 3.2, 3.1 (type 0x80:
   2-octet AS, 4-octet value), 3.2 (type 0x81: 4-octet IPv4 address,
   2-octet value) and 4 of [RFC4360] plus and Section 2 (type 0x82: 4-octet
   AS, 2-octet value) of
   [RFC5668].)  The low-order [RFC5668] with the high-order octet (Sub-Type) of the Redirect Extended
   Community remains 0x08 for all three encodings Type
   field 0x80, 0x81, 0x82 respectively and the low-order of the BGP Extended
   Communities (AS 2-byte, AS 4-byte, and IPv4 address). Type
   field (Sub-Type) always 0x08.

   Interferes with: All No other redirect functions. BGP Flow Specification Traffic Filtering
   Action in this document.

7.5.  Traffic Marking (traffic-marking) sub-type 0x09

   The traffic marking extended community instructs a system to modify
   the DSCP bits in the IP header ([RFC2474] Section 3) of a transiting
   IP packet to the corresponding value.
   This extended community is encoded as a sequence of 5 zero bytes
   followed by the DSCP value encoded in the 6 least
   significant bits of
   6th byte. the extended community value as shown in
   Figure 6.

   The extended is encoded as follows:

      0                   1                   2                   3
      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   reserved    |   reserved    |   reserved    |   reserved    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   reserved    | r.|    DSCP   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 6: Traffic Marking Extended Community Encoding

   o  DSCP: new DSCP value for the transiting IP packet.

   o  reserved, r.: SHOULD be set to 0 on encoding, and MUST be ignored
      during decoding.

   Interferes with: No other BGP Flow Specification traffic action Traffic Filtering
   Action in this document.

7.6.  Considerations on Traffic Action Interference

   Since traffic actions are represented as  Interaction with other Filtering Mechanisms in Routers

   Implementations SHOULD provide mechanisms that map an arbitrary BGP extended
   community
   values, traffic actions may interfere value (normal or extended) to Traffic Filtering Actions
   that require different mappings in different systems in the network.
   For instance, providing packets with each other (ie. there may a worse-than-best-effort, per-
   hop behavior is a functionality that is likely to be more implemented
   differently in different systems and for which no standard behavior
   is currently known.  Rather than one attempting to define it here, this
   can be accomplished by mapping a user-defined community value to
   platform-/network-specific behavior via user configuration.

7.7.  Considerations on Traffic Filtering Action Interference

   Since Traffic Filtering Actions are represented as BGP extended
   community values, Traffic Filtering Actions may interfere with each
   other (e.g. there may be more than one conflicting traffic-rate action traffic-rate-bytes
   Traffic Filtering Action associated with a single flow-filter). Flow
   Specification).  Traffic action Filtering Action interference has no impact
   on BGP propagation of flow filters Flow Specifications (all communities are
   propagated according to policies).

   If a flow filter Flow Specification associated with interfering flow actions Traffic Filtering
   Actions is selected for packet forwarding, it is a an implementation
   decision which of the interfering traffic actions Traffic Filtering Actions are
   selected.  Implementors of this specification SHOULD document the
   behaviour of their implementation in such cases.

   If required, operators

   Operators are encouraged to make use of the BGP policy framework
   supported by their implementation in order to achieve a predictable
   behaviour (ie. match - replace - delete communities on administrative
   boundaries).  See also Section 13.

8.  Dissemination of Traffic Filtering in BGP/MPLS VPN Networks

   Provider-based Layer 3 VPN networks, such as the ones using a BGP/
   MPLS IP VPN [RFC4364] control plane, may have different traffic
   filtering requirements than Internet service providers.  But also
   Internet service providers may use those VPNs for scenarios like
   having the Internet routing table in a VRF, resulting in the same
   traffic filtering requirements as defined for the global routing
   table environment within this document.  This document proposes defines an
   additional BGP NLRI type (AFI=1, SAFI=134) value, which can be used
   to propagate traffic filtering information Flow Specification in a BGP/MPLS VPN environment.

   The NLRI format for this address family consists of a fixed-length
   Route Distinguisher field (8 bytes) followed by a Flow Specification,
   following the encoding defined above in Flow
   Specification NLRI value Section 4.2 of this document. 4.2.  The NLRI length field shall
   include both the 8 bytes of the Route Distinguisher as well as the
   subsequent Flow Specification. Specification NLRI value.  The resulting encoding is
   shown in Figure 7.

                     +------------------------------+
                     | length (0xnn or 0xfn nn)     |
                     +------------------------------+
                     | Route Distinguisher (8 bytes)|
                     +------------------------------+
                     |    NLRI value  (variable)    |
                     +------------------------------+

                          Flow-spec NLRI for MPLS

   Propagation of this NLRI is controlled by matching Route Target
   extended communities associated with the BGP path advertisement with
   the VRF import policy, using the same mechanism as described in "BGP/
   MPLS IP VPNs" [RFC4364].

                Figure 7: Flow Specification rules received via this NLRI apply only to traffic
   that belongs to the VRF(s) in which it is imported.  By default,
   traffic received from a remote PE is switched via an MPLS forwarding
   decision and is not subject to filtering.

   Contrary to the behavior specified for the non-VPN NLRI, flow rules
   are accepted by default, when received from remote PE routers.

8.1.  Validation Procedures for BGP/MPLS VPNs

   The validation procedures are the same as for IPv4.

8.2.  Traffic Actions Rules

   The traffic action rules are the same as for IPv4.

9.  Limitations of Previous Traffic Filtering Efforts

9.1.  Limitations in Previous DDoS Traffic Filtering Efforts

   The popularity of traffic-based, denial-of-service (DoS) attacks,
   which often requires the network operator to be able to use traffic
   filters for detection and mitigation, brings with it requirements
   that are not fully satisfied by existing tools.

   Increasingly, DoS mitigation requires coordination among several
   service providers in order to be able to identify traffic source(s)
   and because the volumes of traffic may be such that they will
   otherwise significantly affect the performance of the network.

   Several techniques are currently used to control traffic filtering of
   DoS attacks.  Among those, one of the most common is to inject
   unicast route advertisements corresponding to a destination prefix
   being attacked (commonly known as remote triggered blackhole RTBH).
   One variant of this technique marks such route advertisements with a
   community that gets translated into a discard Next-Hop by the
   receiving router.  Other variants attract traffic to a particular
   node that serves as a deterministic drop point.

   Using unicast routing advertisements to distribute traffic filtering
   information has the advantage of using the existing infrastructure
   and inter-AS communication channels.  This can allow, for instance, a
   service provider to accept filtering requests from customers for
   address space they own.

   There are several drawbacks, however.  An issue that is immediately
   apparent is the granularity of filtering control: only destination
   prefixes may be specified.  Another area MPLS

   Propagation of concern is the fact that
   filtering information is intermingled with routing information.

   The mechanism defined in this document is designed to address these
   limitations.  We use the Flow Specification NLRI defined above to
   convey information about traffic filtering rules for traffic that is
   subject to modified forwarding behavior (actions).  The actions are
   defined as controlled by matching Route Target
   extended communities and include (but are not limited to)
   rate-limiting (including discard), traffic redirection, packet
   rewriting.

9.2.  Limitations in Previous BGP/MPLS Traffic Filtering Efforts

   Provider-based Layer 3 VPN networks, such as associated with the ones BGP path advertisement with
   the VRF import policy, using a the same mechanism as described in BGP/
   MPLS IP VPN [RFC4364] control plane, may have different traffic
   filtering requirements than Internet service providers.

   In these environments, the VPN customer network often has VPNs [RFC4364].

   Flow Specifications received via this NLRI apply only to traffic
   filtering capabilities towards their external network connections
   (e.g., firewall facing public network connection).  Less common is that
   belongs to the presence of traffic filtering capabilities between different VPN
   attachment sites.  In an any-to-any connectivity model, VRF(s) in which it is the imported.  By default, this means that site-to-site traffic is unfiltered.

   In circumstances where
   received from a security threat does get propagated inside
   the VPN customer network, there may remote PE is switched via an MPLS forwarding decision
   and is not be readily available
   mechanisms subject to provide mitigation via traffic filter.

   But also Internet service providers may use those VPNs filtering.

   Contrary to the behavior specified for scenarios
   like having the Internet routing table in a VRF.  Therefore,
   limitations described in Section 9.1 also apply to this section.

   The BGP non-VPN NLRI, Flow Specification addresses these limitations.

10.
   Specifications are accepted by default, when received from remote PE
   routers.

   The validation procedure (Section 6) and Traffic Filtering Actions
   (Section 7) are the same as for IPv4.

9.  Traffic Monitoring

   Traffic filtering applications require monitoring and traffic
   statistics facilities.  While this is an implementation-specific implementation specific
   choice, implementations SHOULD provide:

   o  A mechanism to log the packet header of filtered traffic.

   o  A mechanism to count the number of matches for a given flow
      specification rule. Flow
      Specification.

10.  Error-Handling

   Error handling according to [RFC7606] SHOULD apply to this
   specification.

   This document introduces Traffic Filtering Action Extended
   Communities.  Malformed Traffic Filtering Action Extended Communities
   in the sense of [RFC7606] Section 7.14. are Extended Community values
   that cannot be decoded according to Section 7 of this document.

11.  Error-Handling and  Future NLRI Extensions

   Future Flow Specification extensions may introduce new Flow
   Specification components.  In case order to facilitate such extensions of
   the Flow Specification NLRI, in addition to the cases described in
   [RFC7606], if BGP encounters an error in a unknown Flow Specification component
   in an UPDATE
   message message, it SHOULD also treat this message as Treat-as-withdraw according
   to Treat-as-
   withdraw as specified in [RFC7606] Section 2.

   Possible reasons for an error are (for more reasons see also
   [RFC7606]):

   o  Incorrect implementation of this

   The specification - the encoding/
      decoding of the NLRI or traffic action extended-communities do not
      comply with this specification.

   o  Unknown Flow Specification extensions - The sending party has
      implemented a new Flow Specification NLRI extension unknown to Component Type SHOULD
   clearly identify what the
      receiving party.

   In order criteria used to facilitate future extensions of match packets forwarded by
   the Flow Specification
   NLRI, router is.  This criteria should be meaningful across router hops
   and not depend on values that change hop-by-hop such as TTL or Layer
   2 encapsulation.

   Such extensions SHOULD also specify a way to encode a "always-true" an "always-match"
   match condition within the newly introduced components. components (this is a
   match condition, encoded with the newly introduced components: If
   present on its own, matches all flows).  This match condition can be
   used to propagate (and apply) certain filters Flow Specifications only if a
   specific extension is known to the implemenation. implementation.

12.  IANA Considerations

   This section complies with [RFC7153].

12.1.  AFI/SAFI Definitions

   IANA maintains a registry entitled "SAFI Values".  For the purpose of
   this work, IANA updated is requested to update the registry following SAFIs to read
   according to the table below (Note: This document obsoletes both
   RFC7674 and allocated two additional
   SAFIs: RFC5575 and all references to those documents should be
   deleted from the registry below):

   +-------+------------------------------------------+----------------+
   | Value | Name                                     | Reference      |
   +-------+------------------------------------------+----------------+
   | 133   | IPv4 dissemination Dissemination of Flow Specification      | [this          |
   |       | rules                                    | document]      |
   | 134   | VPNv4 dissemination L3VPN Dissemination of Flow              | [this          |
   |       | Specification rules                      | document]      |
   +-------+------------------------------------------+----------------+

                      Table 3: Registry: SAFI Values

12.2.  Flow Component Definitions

   A Flow Specification consists of a sequence of flow components, which
   are identified by a an 8-bit component type.  IANA has created and
   maintains a registry entitled "Flow Spec Component Types".  IANA is
   requested to update the reference for this registry to [this
   document].  Furthermore the references to the values should be
   updated according to the table below (Note: This document defines obsoletes
   both RFC7674 and RFC5575 and all references to those documents should
   be deleted from the following Component Type Codes: registry below).

             +-------+--------------------+-----------------+
             | Value | Name               | Reference       |
             +-------+--------------------+-----------------+
             | 1     | Destination Prefix | [this document] |
             | 2     | Source Prefix      | [this document] |
             | 3     | IP Protocol        | [this document] |
             | 4     | Port               | [this document] |
             | 5     | Destination port   | [this document] |
             | 6     | Source port        | [this document] |
             | 7     | ICMP type          | [this document] |
             | 8     | ICMP code          | [this document] |
             | 9     | TCP flags          | [this document] |
             | 10    | Packet length      | [this document] |
             | 11    | DSCP               | [this document] |
             | 12    | Fragment           | [this document] |
             +-------+--------------------+-----------------+

               Table 4: Registry: Flow Spec Component Types

   In order to manage the limited number space and accommodate several
   usages, the following policies defined by [RFC8126] are used:

             +--------------+-------------------------------+
             | Range Type Values  | Policy                        |
             +--------------+-------------------------------+
             | 0            | Invalid value Specification required        |
             | [1 .. 12]    | Defined by this specification |
             | [13 .. 127]  | Specification required        |
             | [128 .. 255] | First Come First Served       |
             +--------------+-------------------------------+

                Table 5: Flow Spec Component Types Policies

   The specification of a particular "Flow       |
             +--------------+-------------------------------+

                Table 5: Flow Spec Component Type" must
   clearly identify what the criteria used to match packets forwarded by
   the router is.  This criteria should be meaningful across router hops
   and not depend on values that change hop-by-hop such as TTL or Layer
   2 encapsulation. Types Policies

12.3.  Extended Community Flow Specification Actions

   The Extended Community Flow Specification Action types defined in
   this document consist of two parts:

      Type (BGP Transitive Extended Community Type)

      Sub-Type

   For the type-part, IANA maintains a registry entitled "BGP Transitive
   Extended Community Types".  For the purpose of this work (Section 7),
   IANA updated is requested to update the registry references to contain the values listed below: following entries
   according to the table below (Note: This document obsoletes both
   RFC7674 and RFC5575 and all references to those documents should be
   deleted in the registry below):

   +-------+-----------------------------------------------+-----------+
   | Type  | Name                                          | Reference |
   | Value |                                               |           |
   +-------+-----------------------------------------------+-----------+
   | 0x80  | Generic Transitive Experimental Use Extended  | [RFC7153] |
   |       | Community (Sub-Types are defined in the       |           |
   |       | "Generic Transitive Experimental Use Extended |           |
   |       | Community Sub-Types" registry)                |           |
   | 0x81  | Generic Transitive Experimental Use Extended  | [this     |
   |       | Community Part 2 (Sub-Types are defined in    | document] |
   |       | the "Generic Transitive Experimental Use      | [See           |
   |       | Extended Community Part 2 Sub-Types"          | Note-1]           |
   |       | Registry)                                     |           |
   | 0x82  | Generic Transitive Experimental Use Extended  | [this     |
   |       | Community Part 3 (Sub-Types are defined in    | document] |
   |       | the "Generic Transitive Experimental Use      | [See           |
   |       | Extended Community Part 3 Sub-Types"          | Note-1]           |
   |       | Registry)                                     |           |
   +-------+-----------------------------------------------+-----------+

        Table 6: Registry: Generic BGP Transitive Experimental Use Extended Community Types

   Note-1: This document obsoletes RFC7674.

   For the sub-type part of the extended community actions Traffic Filtering
   Actions IANA maintains and updated the following registries:

   +----------+-----------------------------------------+--------------+ registries.  IANA is requested
   to update all names and references according to the tables below and
   assign a new value for the "Flow spec traffic-rate-packets" Sub-Type
   (Note: This document obsoletes both RFC7674 and RFC5575 and all
   references to those documents should be deleted from the registries
   below).

   +----------+--------------------------------------------+-----------+
   | Sub-Type | Name                                       | Reference |
   | Value    |                                            |           |
   +----------+-----------------------------------------+--------------+
   +----------+--------------------------------------------+-----------+
   | 0x06     | Flow spec traffic-rate-bytes               | [this     |
   |          |                                            | document] |
   | TBD      | Flow spec traffic-rate-packets             | [this     |
   |          |                                            | document] |
   | 0x07     | Flow spec traffic-action (Use of the       | [this     |
   |          | "Value" field is defined in the "Traffic   | document] |
   |          | "Traffic Action Fields" registry)                   | [See Note-2]           |
   | 0x08     | Flow spec rt-redirect AS-2byte format      | [this     |
   |          |                                            | document] |
   | 0x09     | Flow spec traffic-remarking                | [this     |
   |          |                                            | document] |
   +----------+-----------------------------------------+--------------+
   +----------+--------------------------------------------+-----------+

      Table 7: Registry: Generic Transitive Experimental Use Extended
                            Community Sub-Types

   Note-2: This document obsoletes both RFC7674 and RFC5575.

   +-------------+---------------------------+-------------------------+

   +----------------+--------------------------------+-----------------+
   | Sub-Type Value | Name                           | Reference       |
   | Value       |                           |                         |
   +-------------+---------------------------+-------------------------+
   +----------------+--------------------------------+-----------------+
   | 0x08           | Flow spec rt-redirect IPv4     | [this document] [See |
   |                | IPv4 format                         | Note-3]                 |
   +-------------+---------------------------+-------------------------+
   +----------------+--------------------------------+-----------------+

      Table 8: Registry: Generic Transitive Experimental Use Extended
                        Community Part 2 Sub-Types

   +-------------+----------------------------+------------------------+

   +---------------+----------------------------------+----------------+
   | Sub-Type      | Name                             | Reference      |
   | Value         |                                  |                |
   +-------------+----------------------------+------------------------+
   +---------------+----------------------------------+----------------+
   | 0x08          | Flow spec rt-redirect AS- AS-4byte   | [this document] [See          |
   |               | 4byte format                           | Note-3] document]      |
   +-------------+----------------------------+------------------------+
   +---------------+----------------------------------+----------------+

      Table 9: Registry: Generic Transitive Experimental Use Extended
                        Community Part 3 Sub-Types

   Note-3: This document obsoletes RFC7674, and becomes

   Furthermore IANA is requested to update the only reference for this table. the
   registries "Generic Transitive Experimental Use Extended Community
   Part 2 Sub-Types" and "Generic Transitive Experimental Use Extended
   Community Part 3 Sub-Types" to [this document].

   The "traffic-action" extended community (Section 7.3) defined in this
   document has 46 unused bits, which can be used to convey additional
   meaning.  IANA created and maintains a new registry entitled: "Traffic
   Action Fields".  IANA is requested to update the reference for this
   registry to [this document].  Furthermore IANA is requested to update
   the references according to the table below.  These values should be assigned via IETF
   Review rules only.  The following traffic-action fields have been
   allocated:
   assigned via IETF Review rules only (Note: This document obsoletes
   both RFC7674 and RFC5575 and all references to those documents should
   be deleted from the registry below).

                +-----+-----------------+-----------------+
                | Bit | Name            | Reference       |
                +-----+-----------------+-----------------+
                | 47  | Terminal Action | [this document] |
                | 46  | Sample          | [this document] |
                +-----+-----------------+-----------------+

                 Table 10: Registry: Traffic Action Fields

13.  Security Considerations

   As long as Flow Specifications are restricted to match the
   corresponding unicast routing paths for the relevant prefixes
   (Section 6), the security characteristics of this proposal are
   equivalent to the existing security properties of BGP unicast
   routing.  Any relaxation of the validation procedure described in
   Section 6 may allow unwanted Flow Specifications to be propagated and
   thus unwanted Traffic Filtering Actions may be applied to flows.

   Where the above mechanisms are not in place, this could open the door
   to further denial-of-service attacks such as unwanted traffic
   filtering, remarking or redirection.

   Deployment of specific relaxations of the validation within an
   administrative boundary of a network, defined by an AS or an AS-
   Confederation boundary, may be useful in some networks for quickly
   distributing filters to prevent denial-of-service attacks.  For a
   network to utilize this relaxation, the BGP policies must support
   additional filtering since the origin AS field is empty.
   Specifications relaxing the validation restrictions SHOULD contain
   security considerations that provide details on the required
   additional filtering.  For example, the use of [RFC6811] to enhance
   filtering within an AS confederation.

   Inter-provider routing is based on a web of trust.  Neighboring
   autonomous systems are trusted to advertise valid reachability
   information.  If this trust model is violated, a neighboring
   autonomous system may cause a denial-of-service attack by advertising
   reachability information for a given prefix for which it does not
   provide service.

   As long as traffic filtering rules are restricted to match the
   corresponding unicast routing paths for the relevant prefixes, the
   security characteristics service (unfiltered address space hijack).  Since validation
   of this proposal are equivalent the Flow Specification is tied to the
   existing security properties announcement of BGP the best
   unicast routing.  However, route, this
   document also specifies traffic filtering actions that may need
   custom additional verification on the receiver side.  See Section 14.

   Where it is not the case, also cause this would open the door validation to further denial-
   of-service attacks. fail and
   consequently prevent Flow Specifications from being accepted by a
   peer.  Possible mitigations are [RFC6811] and [RFC8205].

   Enabling firewall-like capabilities in routers without centralized
   management could make certain failures harder to diagnose.  For
   example, it is possible to allow TCP packets to pass between a pair
   of addresses but not ICMP packets.  It is also possible to permit
   packets smaller than 900 or greater than 1000 bytes to pass between a
   pair of addresses, but not packets whose length is in the range 900-
   1000.  Such behavior may be confusing and these capabilities should
   be used with care whether manually configured or coordinated through
   the protocol extensions described in this document.

14.  Operational Security Considerations

   Flow Specification BGP speakers (e.g. automated DDoS controllers) not
   properly programmed, algorithms that are not performing as expected,
   or simply rogue systems may announce unintended Flow Specifications,
   send updates at a high rate or generate a high number of Flow
   Specifications.  This may stress the receiving systems, exceed their
   maximum capacity or may lead to unwanted Traffic Filtering Actions
   being applied to flows.

   While the general verification of the traffic filter Flow Specification NLRI is
   specified in this document (Section 6) the traffic filtering actions Traffic Filtering Actions
   received by a third party may need custom verification or filtering.
   In particular all non traffic-rate actions may allow a third party to
   modify packet forwarding properties and potentially gain access to
   other routing-tables/VPNs or undesired queues.  This can be avoided
   by proper filtering filtering/screening of action the Traffic Filtering Action
   communities at network borders and by
   mapping user-defined communities only exposing a predefined subset
   of Traffic Filtering Actions (see Section 7) to expose certain
   forwarding properties to third parties.

   Since verfication of the traffic filtering NLRI  One
   way to achieve this is tied by mapping user-defined communities, that can
   be set by the third party, to Traffic Filtering Actions and not
   accepting Traffic Filtering Action extended communities from third
   parties.

   This extension adds additional information to Internet routers.
   These are limited in terms of the
   announcement maximum number of data elements
   they can hold as well as the best unicast route, a unfiltered address space
   hijack (e.g. advertisement number of events they are able to
   process in a more specific route) may cause this
   verification given unit of time.  Service providers need to fail consider
   the maximum capacity of their devices and consequently prevent may need to limit the
   number of Flow Specification
   filters from being Specifications accepted by a peer.

15.  Original authors and processed.

14.  Contributors

   Barry Greene, Pedro Marques, Jared Mauch, Danny McPherson, and
   Nischal Sheth were authors on RFC5575, [RFC5575], and therefore are
   contributing authors on this document.

16.

15.  Acknowledgements

   The authors would like to thank Yakov Rekhter, Dennis Ferguson, Chris
   Morrow, Charlie Kaufman, and David Smith for their comments for the
   comments on the original RFC5575. [RFC5575].  Chaitanya Kodeboyina helped
   design the flow validation procedure; and Steven Lin and Jim Washburn
   ironed out all the details necessary to produce a working
   implementation in the original RFC5575. [RFC5575].

   A packet rate flowspec action Traffic Filtering Action was also discribed described in a flowspec
   extention Flow
   Specification extension draft and the authors like to thank Wesley
   Eddy, Justin Dailey and Gilbert Clark for their work.

   Additional

   Additionally, the authors would like to thank Alexander Mayrhofer,
   Nicolas Fevrier, Job Snijders, Jeffrey Haas and Adam Chappell for
   their comments and review.

17.

16.  References

17.1.

16.1.  Normative References

   [IEEE.754.1985]
              IEEE, "Standard for Binary Floating-Point Arithmetic",
              IEEE 754-1985, August 1985.

   [ISO_IEC_9899]
              ISO, "Information technology -- Programming languages --
              C", ISO/IEC 9899:2018, June 2018.

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <https://www.rfc-editor.org/info/rfc791>.

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, DOI 10.17487/RFC0792, September 1981,
              <https://www.rfc-editor.org/info/rfc792>.

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [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>.

   [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>.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
              February 2006, <https://www.rfc-editor.org/info/rfc4360>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, DOI 10.17487/RFC4364, February 10.17487/RFC4456, April 2006, <https://www.rfc-editor.org/info/rfc4364>.
              <https://www.rfc-editor.org/info/rfc4456>.

   [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>.

   [RFC5668]  Rekhter, Y., Sangli, S., and D. Tappan, "4-Octet AS
              Specific BGP Extended Community", RFC 5668,
              DOI 10.17487/RFC5668, October 2009,
              <https://www.rfc-editor.org/info/rfc5668>.

   [RFC7153]  Rosen, E. and Y. Rekhter, "IANA Registries for BGP
              Extended Communities", RFC 7153, DOI 10.17487/RFC7153,
              March 2014, <https://www.rfc-editor.org/info/rfc7153>.

   [RFC7606]  Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
              Patel, "Revised Error Handling for BGP UPDATE Messages",
              RFC 7606, DOI 10.17487/RFC7606, August 2015,
              <https://www.rfc-editor.org/info/rfc7606>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

16.2.  Informative References

   [I-D.ietf-idr-flow-spec-v6]
              McPherson, D., Raszuk, R., Pithawala, B.,
              akarch@cisco.com, a., and S. Hares, "Dissemination of Flow
              Specification Rules for IPv6", draft-ietf-idr-flow-spec-
              v6-09 (work in progress), November 2017.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
              <https://www.rfc-editor.org/info/rfc5575>.

   [RFC6811]  Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
              Austein, "BGP Prefix Origin Validation", RFC 6811,
              DOI 10.17487/RFC6811, January 2013,
              <https://www.rfc-editor.org/info/rfc6811>.

   [RFC7674]  Haas, J., Ed., "Clarification of the Flowspec Redirect
              Extended Community", RFC 7674, DOI 10.17487/RFC7674,
              October 2015, <https://www.rfc-editor.org/info/rfc7674>.

   [RFC8205]  Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol
              Specification", RFC 8205, DOI 10.17487/RFC8205, September
              2017, <https://www.rfc-editor.org/info/rfc8205>.

16.3.  URIs

   [1] https://github.com/stoffi92/flowspec-cmp

Appendix A.  Python code: flow_rule_cmp

  <CODE BEGINS>
  """
  Copyright (c) 2019 IETF Trust and the persons identified as authors of
  the code. All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, is permitted pursuant to, and subject to the license
  terms contained in, the Simplified BSD License set forth in Section
  4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
  (http://trustee.ietf.org/license-info).
  """

  import itertools
  import ipaddress

  def flow_rule_cmp(a, b):
      for comp_a, comp_b in itertools.zip_longest(a.components,
                                             b.components):
          # If a component type does not exist in one rule
          # this rule has lower precedence
          if not comp_a:
              return B_HAS_PRECEDENCE
          if not comp_b:
              return A_HAS_PRECEDENCE
          # higher precedence for lower component type
          if comp_a.component_type < comp_b.component_type:
              return A_HAS_PRECEDENCE
          if comp_a.component_type > comp_b.component_type:
              return B_HAS_PRECEDENCE
          # component types are equal -> type specific comparison
          if comp_a.component_type in (IP_DESTINATION, IP_SOURCE):
              # assuming comp_a.value, comp_b.value 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>.

17.2.  Informative References

   [I-D.ietf-idr-flow-spec-v6]
              McPherson, D., Raszuk, R., Pithawala, B.,
              akarch@cisco.com, a., and S. Hares, "Dissemination type
              # ipaddress.IPv4Network
              if comp_a.value.overlaps(comp_b.value):
                  # longest prefixlen has precedence
                  if comp_a.value.prefixlen > comp_b.value.prefixlen:
                      return A_HAS_PRECEDENCE
                  if comp_a.value.prefixlen < comp_b.value.prefixlen:
                      return B_HAS_PRECEDENCE
                  # components equal -> continue with next component
              elif comp_a.value > comp_b.value:
                  return B_HAS_PRECEDENCE
              elif comp_a.value < comp_b.value:
                  return A_HAS_PRECEDENCE
          else:
              # assuming comp_a.value, comp_b.value of Flow
              Specification Rules for IPv6", draft-ietf-idr-flow-spec-
              v6-09 (work in progress), November 2017.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

17.3.  URIs

   [1] https://github.com/stoffi92/flowspec-cmp type bytearray
              if len(comp_a.value) == len(comp_b.value):
                  if comp_a.value > comp_b.value:
                      return B_HAS_PRECEDENCE
                  if comp_a.value < comp_b.value:
                      return A_HAS_PRECEDENCE
                  # components equal -> continue with next component
              else:
                  common = min(len(comp_a.value), len(comp_b.value))
                  if comp_a.value[:common] > comp_b.value[:common]:
                      return B_HAS_PRECEDENCE
                  elif comp_a.value[:common] < comp_b.value[:common]:
                      return A_HAS_PRECEDENCE
                  # the first common bytes match
                  elif len(comp_a.value) > len(comp_b.value):
                      return A_HAS_PRECEDENCE
                  else:
                      return B_HAS_PRECEDENCE
      return EQUAL
  <CODE ENDS>

Appendix A. B.  Comparison with RFC 5575

   This document includes numerous editorial changes to RFC5575. [RFC5575].  It
   also completely incorporates the redirect action clarification
   document [RFC7674].  It is recommended to read the entire document.
   The authors, however want to point out the following technical
   changes to RFC5575: [RFC5575]:

      Section 1 introduces the Flow Specification NLRI.  In RFC5575 [RFC5575]
      this NLRI was defined as an opaque-key in BGPs database.  This
      specification has removed all references to a opaque-key property.
      BGP is able to understand the NLRI encoding.  This change also
      resulted in a new section regarding error-handling and
      extensibility (Section 10 and Section 11).

      Section 4.2.3 4.2.2.3 defines a numeric operator and comparison bit
      combinations.  In RFC5575 [RFC5575] the meaning of those bit combination
      was not explicitly defined and left open to the reader.

      Section 4.2.3 4.2.2.3 - Section 4.2.8, 4.2.2.8, Section 4.2.10, 4.2.2.10,
      Section 4.2.11 4.2.2.11 make use of the above numeric operator.  The
      allowed length of the comparison value was not consistently
      defined in RFC5575. [RFC5575].

      Section 7 defines all traffic action extended Traffic Filtering Action Extended
      communities as transitive extended communities.  RFC5575  [RFC5575] defined
      the traffic-rate action to be non-transitive and did not define
      the transitivity of the other action Traffic Filtering Action communities
      at all.

      Section 7.2 introduces a new traffic filtering action Traffic Filtering Action (traffic-
      rate-packets).  This action did not exist in RFC5575. [RFC5575].

      Section 7.4 contains the same redirect actions already defined in
      RFC5575
      [RFC5575] however, these actions have been renamed to "rt-redirect" "rt-
      redirect" to make it clearer that the redirection is based on
      route-target.  This section also completely incorporates the
      [RFC7674] clarifications of the Flowspec Redirect Extended
      Community.

      Section 7.6 7.7 contains general considerations on interfering traffic
      actions.  Section 7.3 also cross-references this section.  RFC5575
      [RFC5575] did not mention this.

      Section 11 10 contains a modified new error handling.

      Section 11 describes graceful handling of unknown Flow
      Specification components to gracefully allow future extensions of flow specification. extensions.

Authors' Addresses

   Christoph Loibl
   Next Layer Communications
   Mariahilfer Guertel 37/7
   Vienna  1150
   AT

   Phone: +43 664 1176414
   Email: cl@tix.at

   Susan Hares
   Huawei
   7453 Hickory Hill
   Saline, MI  48176
   USA

   Email: shares@ndzh.com

   Robert Raszuk
   Bloomberg LP
   731 Lexington Ave
   New York City, NY  10022
   USA

   Email: robert@raszuk.net

   Danny McPherson
   Verisign
   USA

   Email: dmcpherson@verisign.com

   Martin Bacher
   T-Mobile Austria
   Rennweg 97-99
   Vienna  1030
   AT

   Email: mb.ietf@gmail.com