Dissemination of Flow Specification Rules for IPv6
draft-ietf-idr-flow-spec-v6-15

Document Type Active Internet-Draft (idr WG)
Last updated 2020-09-21
Replaces draft-raszuk-idr-flow-spec-v6
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IDR Working Group                                          C. Loibl, Ed.
Internet-Draft                                   next layer Telekom GmbH
Intended status: Standards Track                          R. Raszuk, Ed.
Expires: March 25, 2021                                     Bloomberg LP
                                                           S. Hares, Ed.
                                                                  Huawei
                                                      September 21, 2020

           Dissemination of Flow Specification Rules for IPv6
                     draft-ietf-idr-flow-spec-v6-15

Abstract

   Dissemination of Flow Specification Rules provides a Border Gateway
   Protocol extension for the propagation of traffic flow information
   for the purpose of rate limiting or filtering IPv4 protocol data
   packets.

   This specification extends I-D.ietf-idr-rfc5575bis with IPv6
   functionality.

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 March 25, 2021.

Copyright Notice

   Copyright (c) 2020 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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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Definitions of Terms Used in This Memo  . . . . . . . . .   3
   2.  IPv6 Flow Specification encoding in BGP . . . . . . . . . . .   3
   3.  IPv6 Flow Specification components  . . . . . . . . . . . . .   3
     3.1.  Type 1 - Destination IPv6 Prefix  . . . . . . . . . . . .   4
     3.2.  Type 2 - Source IPv6 Prefix . . . . . . . . . . . . . . .   4
     3.3.  Type 3 - Upper-Layer Protocol . . . . . . . . . . . . . .   4
     3.4.  Type 7 - ICMPv6 Type  . . . . . . . . . . . . . . . . . .   5
     3.5.  Type 8 - ICMPv6 Code  . . . . . . . . . . . . . . . . . .   5
     3.6.  Type 12 - Fragment  . . . . . . . . . . . . . . . . . . .   6
     3.7.  Type 13 - Flow Label (new)  . . . . . . . . . . . . . . .   6
     3.8.  Encoding Example  . . . . . . . . . . . . . . . . . . . .   7
   4.  Ordering of Flow Specifications . . . . . . . . . . . . . . .   8
   5.  Validation Procedure  . . . . . . . . . . . . . . . . . . . .   9
   6.  IPv6 Traffic Filtering Action changes . . . . . . . . . . . .   9
     6.1.  Redirect IPv6 (rt-redirect-ipv6) Type/Sub-Type 0x80/TBD .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Flow Spec IPv6 Component Types  . . . . . . . . . . . . .  10
       8.1.1.  Registry Template . . . . . . . . . . . . . . . . . .  10
       8.1.2.  Registry Contents . . . . . . . . . . . . . . . . . .  10
     8.2.  Extended Community Flow Spec IPv6 Actions . . . . . . . .  12
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  13
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     11.2.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  14
   Appendix A.  Example python code: flow_rule_cmp_v6  . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   The growing amount of IPv6 traffic in private and public networks
   requires the extension of tools used in IPv4-only networks to be also
   capable of supporting IPv6 data packets.

   This document analyzes the differences of IPv6 [RFC8200] flows
   description from those of traditional IPv4 packets and propose a
   subset of new Border Gateway Protocol [RFC4271] encoding formats to

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   enable Dissemination of Flow Specification Rules
   [I-D.ietf-idr-rfc5575bis] for IPv6.

   This specification is an extension of the base
   [I-D.ietf-idr-rfc5575bis].  It only defines the delta changes
   required to support IPv6 while all other definitions and operation
   mechanisms of Dissemination of Flow Specification Rules will remain
   in the main specification and will not be repeated here.

1.1.  Definitions of Terms Used in This Memo

   AFI -   Address Family Identifier.

   AS -   Autonomous System.

   NLRI -   Network Layer Reachability Information.

   SAFI -   Subsequent Address Family Identifier.

   VRF -   Virtual Routing and Forwarding instance.

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

2.  IPv6 Flow Specification encoding in BGP

   [I-D.ietf-idr-rfc5575bis] defines SAFIs 133 (Dissemination of Flow
   Specification) and 134 (L3VPN Dissemination of Flow Specification) in
   order to carry the corresponding Flow Specification.

   Implementations wishing to exchange IPv6 Flow Specifications 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=2, SAFI=133) for IPv6 Flow Specification, and (AFI=2,
   SAFI=134) for VPNv6 Flow Specification.

3.  IPv6 Flow Specification components

   The encoding of each of the components begins with a type field (1
   octet) followed by a variable length parameter.  The following
   sections define component types and parameter encodings for IPv6.

   Types 4, 5, 6, 9, 10 and 11, as defined in [I-D.ietf-idr-rfc5575bis],
   also apply to IPv6.  Note that even if the definitions are the same

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   (and not repeated here), the number space is managed separately
   (Section 8).

3.1.  Type 1 - Destination IPv6 Prefix

   Encoding: <type (1 octet), length (1 octet), offset (1 octet),
   pattern (variable), padding(variable) >

   Defines the destination prefix to match.  The offset has been defined
   to allow for flexible matching on part of the IPv6 address where it
   is required to skip (don't care) of N first bits of the address.
   This can be especially useful where part of the IPv6 address consists
   of an embedded IPv4 address and matching needs to happen only on the
   embedded IPv4 address.  The encoded pattern contains enough octets
   for the bits used in matching (length minus offset bits).

   length -  The length field indicates the N-th leftmost bit in the
      address where bitwise pattern matching stops.

   offset -  The offset field indicates the number of leftmost address
      bits to skip before bitwise pattern matching starts.

   pattern -  Contains the matching pattern.  The length of the pattern
      is defined by the number of bits needed for pattern matching
      (length minus offset).

   padding -  The minimum number of bits required to pad the component
      to an octet boundary.  Padding bits MUST be 0 on encoding and MUST
      be ignored on decoding.

   Length minus offset must always be 0 or more, otherwise this
   component is malformed.

3.2.  Type 2 - Source IPv6 Prefix

   Encoding: <type (1 octet), length (1 octet), offset (1 octet),
   pattern (variable), padding(variable) >

   Defines the source prefix to match.  The length, offset, pattern and
   padding are the same as in Section 3.1

3.3.  Type 3 - Upper-Layer Protocol

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

   Contains a list of {numeric_op, value} pairs that are used to match
   the first Next Header value octet in IPv6 packets that is not an

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   extension header and thus indicates that the next item in the packet
   is the corresponding upper-layer header (see [RFC8200] Section 4).

   This component uses the Numeric Operator (numeric_op) described in
   [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1.  Type 3 component values
   SHOULD be encoded as single octet (numeric_op len=00).

   Note: While IPv6 allows for more than one Next Header field in the
   packet, the main goal of the Type 3 Flow Specification component is
   to match on the first upper-layer IP protocol value.  Therefore the
   definition is limited to match only on this specific Next Header
   field in the packet.

3.4.  Type 7 - ICMPv6 Type

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

   Defines a list of {numeric_op, value} pairs used to match the type
   field of an ICMPv6 packet (see also [RFC4443] Section 2.1).

   This component uses the Numeric Operator (numeric_op) described in
   [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1.  Type 7 component values
   SHOULD be encoded as single octet (numeric_op len=00).

   In case of the presence of the ICMPv6 Type component only ICMPv6
   packets can match the entire Flow Specification.  The ICMPv6 Type
   component, if present, never matches when the packet's upper-layer IP
   protocol value is not 58 (ICMPv6), 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.

3.5.  Type 8 - ICMPv6 Code

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

   Defines a list of {numeric_op, value} pairs used to match the code
   field of an ICMPv6 packet (see also [RFC4443] Section 2.1).

   This component uses the Numeric Operator (numeric_op) described in
   [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1.  Type 8 component values
   SHOULD be encoded as single octet (numeric_op len=00).

   In case of the presence of the ICMPv6 Code component only ICMPv6
   packets can match the entire Flow Specification.  The ICMPv6 code
   component, if present, never matches when the packet's upper-layer IP
   protocol value is not 58 (ICMPv6), if the packet is fragmented and
   this is not the first fragment, or if the system is unable to locate

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   the transport header.  Different implementations may or may not be
   able to decode the transport header.

3.6.  Type 12 - Fragment

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

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

   This component uses the Bitmask Operator (bitmask_op) described in
   [I-D.ietf-idr-rfc5575bis] Section 4.2.1.2.  The Type 12 component
   bitmask MUST be encoded as single octet bitmask (bitmask_op len=00).

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

                    Figure 1: Fragment Bitmask Operand

   Bitmask values:

   IsF -  Is a fragment - match if IPv6 Fragment Header ([RFC8200]
      Section 4.5) Fragment Offset is not 0

   FF -  First fragment - match if IPv6 Fragment Header ([RFC8200]
      Section 4.5) Fragment Offset is 0 AND M flag is 1

   LF -  Last fragment - match if IPv6 Fragment Header ([RFC8200]
      Section 4.5) Fragment Offset is not 0 AND M flag is 0

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

3.7.  Type 13 - Flow Label (new)

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

   Contains a list of {numeric_op, value} pairs that are used to match
   the 20-bit Flow Label IPv6 header field ([RFC8200] Section 3).

   This component uses the Numeric Operator (numeric_op) described in
   [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1.  Type 13 component values
   SHOULD be encoded as 1-, 2-, or 4-byte quantities (numeric_op len=00,
   len=01 or len=10).

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3.8.  Encoding Example

3.8.1.  Example 1

   The following example demonstrates the prefix encoding for: "packets
   from ::1234:5678:9A00:0/64-104 to 2001:DB8::/32 and upper-layer-
   protocol tcp".

  +--------+----------------------+-------------------------+----------+
  | length | destination          | source                  | ul-proto |
  +--------+----------------------+-------------------------+----------+
  | 0x12   | 01 20 00 20 01 0D B8 | 02 68 40 12 34 56 78 9A | 03 81 06 |
  +--------+----------------------+-------------------------+----------+

   Decoded:

       +-------+------------+-------------------------------+
       | Value |            |                               |
       +-------+------------+-------------------------------+
       |  0x12 | length     | 18 octets (len<240 1-octet)   |
       |  0x01 | type       | Type 1 - Dest. IPv6 Prefix    |
       |  0x20 | length     | 32 bit                        |
       |  0x00 | offset     | 0 bit                         |
       |  0x20 | pattern    |                               |
       |  0x01 | pattern    |                               |
       |  0x0D | pattern    |                               |
       |  0xB8 | pattern    | (no padding needed)           |
       |  0x02 | type       | Type 2 - Source IPv6 Prefix   |
       |  0x68 | length     | 104 bit                       |
       |  0x40 | offset     | 64 bit                        |
       |  0x12 | pattern    |                               |
       |  0x34 | pattern    |                               |
       |  0x56 | pattern    |                               |
       |  0x78 | pattern    |                               |
       |  0x9A | pattern    | (no padding needed)           |
       |  0x03 | type       | Type 3 - upper-layer-proto    |
       |  0x81 | numeric_op | end-of-list, value size=1, == |
       |  0x06 | value      | 06                            |
       +-------+------------+-------------------------------+

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

   Neither for the destination prefix pattern (length - offset = 32 bit)
   nor for the source prefix pattern (length - offset = 40 bit) any
   padding is needed (both patterns end on a octet boundary).

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3.8.2.  Example 2

   The following example demonstrates the prefix encoding for: "all
   packets from ::1234:5678:9A00:0/65-104 to 2001:DB8::/32".

      +--------+----------------------+-------------------------+
      | length | destination          | source                  |
      +--------+----------------------+-------------------------+
      | 0x0f   | 01 20 00 20 01 0D B8 | 02 68 41 24 68 ac f1 34 |
      +--------+----------------------+-------------------------+

   Decoded:

       +-------+-------------+-------------------------------+
       | Value |             |                               |
       +-------+-------------+-------------------------------+
       |  0x0f | length      | 15 octets (len<240 1-octet)   |
       |  0x01 | type        | Type 1 - Dest. IPv6 Prefix    |
       |  0x20 | length      | 32 bit                        |
       |  0x00 | offset      | 0 bit                         |
       |  0x20 | pattern     |                               |
       |  0x01 | pattern     |                               |
       |  0x0D | pattern     |                               |
       |  0xB8 | pattern     | (no padding needed)           |
       |  0x02 | type        | Type 2 - Source IPv6 Prefix   |
       |  0x68 | length      | 104 bit                       |
       |  0x41 | offset      | 65 bit                        |
       |  0x24 | pattern     |                               |
       |  0x68 | pattern     |                               |
       |  0xac | pattern     |                               |
       |  0xf1 | pattern     |                               |
       |  0x34 | pattern/pad | (contains 1 bit padding)      |
       +-------+-------------+-------------------------------+

   This constitutes a NLRI with a NLRI length of 15 octets.

   The source prefix pattern is 104 - 65 = 39 bits in length.  After the
   pattern one bit of padding needs to be added so that the component
   ends on a octet boundary.  However, only the first 39 bits are
   actually used for bitwise pattern matching starting with a 65 bit
   offset from the topmost bit of the address.

4.  Ordering of Flow Specifications

   The definition for the order of traffic filtering rules from
   [I-D.ietf-idr-rfc5575bis] Section 5.1 is reused with new
   consideration for the IPv6 prefix offset.  As long as the offsets are
   equal, the comparison is the same, retaining longest-prefix-match

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   semantics.  If the offsets are not equal, the lowest offset has
   precedence, as this flow matches the most significant bit.

   The code in Appendix A shows a Python3 implementation of the
   resulting comparison algorithm.  The full code was tested with Python
   3.7.2 and can be obtained at https://github.com/stoffi92/draft-ietf-
   idr-flow-spec-v6/tree/master/flowspec-cmp [1].

5.  Validation Procedure

   The validation procedure is the same as specified in
   [I-D.ietf-idr-rfc5575bis] Section 6 with the exception that item a)
   of the validation procedure should now read as follows:

      a) A destination prefix component with offset=0 is embedded in the
      Flow Specification

6.  IPv6 Traffic Filtering Action changes

   Traffic Filtering Actions from [I-D.ietf-idr-rfc5575bis] Section 7
   can also be applied to IPv6 Flow Specifications.  To allow an IPv6
   address specific route-target, a new Traffic Filtering Action IPv6
   address specific extended community is specified in Section 6.1
   below.

6.1.  Redirect IPv6 (rt-redirect-ipv6) Type/Sub-Type 0x80/TBD

   The redirect IPv6 address specific extended community allows the
   traffic to be redirected to a VRF routing instance that lists the
   specified IPv6 address specific 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 uses the same encoding as the IPv6 address
   specific Route Target extended community [RFC5701] Section 2 with the
   high-order octet of the Type always set to 0x80 and the Sub-Type
   always TBD.

   Interferes with: All BGP Flow Specification redirect Traffic
   Filtering Actions (with itself and those specified in
   [I-D.ietf-idr-rfc5575bis] Section 7.4).

7.  Security Considerations

   This document extends the functionality in [I-D.ietf-idr-rfc5575bis]
   to be applicable to IPv6 data packets.  The same Security
   Considerations from [I-D.ietf-idr-rfc5575bis] now also apply to IPv6

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   networks.  Otherwise, no new security issues are added to the BGP
   protocol.

8.  IANA Considerations

   This section complies with [RFC7153].

8.1.  Flow Spec IPv6 Component Types

   IANA has created and maintains a registry entitled "Flow Spec
   Component Types".  IANA is requested to add [this document] to the
   reference for this registry.  Furthermore the registry should be
   rewritten to also contain the IPv6 Flow Specification Component Types
   as described below.

8.1.1.  Registry Template

   Type Value:
         Contains the assigned Flow Specification component type value.

   IPv4 Name:
         Contains the associated IPv4 Flow Specification component name
         as specified in [I-D.ietf-idr-rfc5575bis].

   IPv6 Name:
         Contains the associated IPv6 Flow Specification component name
         as specified in this document.

   Reference:
         Contains referenced to the specifications.

8.1.2.  Registry Contents

      + Type Value: 0
      + IPv4 Name: Reserved
      + IPv6 Name: Reserved
      + Reference: [I-D.ietf-idr-rfc5575bis]

      + Type Value: 1
      + IPv4 Name: Destination Prefix
      + IPv6 Name: Destination IPv6 Prefix
      + Reference: [I-D.ietf-idr-rfc5575bis] [this document]

      + Type Value: 2
      + IPv4 Name: Source Prefix
      + IPv6 Name: Source IPv6 Prefix

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      + Reference: [I-D.ietf-idr-rfc5575bis] [this document]

      + Type Value: 3
      + IPv4 Name: IP Protocol
      + IPv6 Name: Upper-Layer Protocol
      + Reference: [I-D.ietf-idr-rfc5575bis] [this document]

      + Type Value: 4
      + IPv4 Name: Port
      + IPv6 Name: Port
      + Reference: [I-D.ietf-idr-rfc5575bis]

      + Type Value: 5
      + IPv4 Name: Destination Port
      + IPv6 Name: Destination Port
      + Reference: [I-D.ietf-idr-rfc5575bis]

      + Type Value: 6
      + IPv4 Name: Source Port
      + IPv6 Name: Source Port
      + Reference: [I-D.ietf-idr-rfc5575bis]

      + Type Value: 7
      + IPv4 Name: ICMP Type
      + IPv6 Name: ICMPv6 Type
      + Reference: [I-D.ietf-idr-rfc5575bis] [this document]

      + Type Value: 8
      + IPv4 Name: ICMP Code
      + IPv6 Name: ICMPv6 Code
      + Reference: [I-D.ietf-idr-rfc5575bis] [this document]

      + Type Value: 9
      + IPv4 Name: TCP flags
      + IPv6 Name: TCP flags
      + Reference: [I-D.ietf-idr-rfc5575bis]

      + Type Value: 10
      + IPv4 Name: Packet length
      + IPv6 Name: Packet length

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      + Reference: [I-D.ietf-idr-rfc5575bis]

      + Type Value: 11
      + IPv4 Name: DSCP
      + IPv6 Name: DSCP
      + Reference: [I-D.ietf-idr-rfc5575bis]

      + Type Value: 12
      + IPv4 Name: Fragment
      + IPv6 Name: Fragment
      + Reference: [I-D.ietf-idr-rfc5575bis] [this document]

      + Type Value: 13
      + IPv4 Name: Unassigned
      + IPv6 Name: Flow Label
      + Reference: [this document]

      + Type Value: 14-254
      + IPv4 Name: Unassigned
      + IPv6 Name: Unassigned
      + Reference:

      + Type Value: 255
      + IPv4 Name: Reserved
      + IPv6 Name: Reserved
      + Reference: [I-D.ietf-idr-rfc5575bis]

8.2.  Extended Community Flow Spec IPv6 Actions

   IANA maintains a registry entitled "Generic Transitive Experimental
   Use Extended Community Sub-Types".  For the purpose of this work,
   IANA is requested to assign a new value:

   +----------------+--------------------------------+-----------------+
   | Sub-Type Value | Name                           | Reference       |
   +----------------+--------------------------------+-----------------+
   | TBD            | Flow spec rt-redirect-ipv6     | [this document] |
   |                | format                         |                 |
   +----------------+--------------------------------+-----------------+

      Table 1: Registry: Generic Transitive Experimental Use Extended
                            Community Sub-Types

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9.  Acknowledgements

   Authors would like to thank Pedro Marques, Hannes Gredler, Bruno
   Rijsman, Brian Carpenter, and Thomas Mangin for their valuable input.

10.  Contributors

   Danny McPherson
   Verisign, Inc.

   Email: dmcpherson@verisign.com

   Burjiz Pithawala
   Individual

   Email: burjizp@gmail.com

   Andy Karch
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: akarch@cisco.com

11.  References

11.1.  Normative References

   [I-D.ietf-idr-rfc5575bis]
              Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
              Bacher, "Dissemination of Flow Specification Rules",
              draft-ietf-idr-rfc5575bis-26 (work in progress), August
              2020.

   [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>.

   [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>.

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   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.

   [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>.

   [RFC5701]  Rekhter, Y., "IPv6 Address Specific BGP Extended Community
              Attribute", RFC 5701, DOI 10.17487/RFC5701, November 2009,
              <https://www.rfc-editor.org/info/rfc5701>.

   [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>.

   [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 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>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

11.2.  URIs

   [1] https://github.com/stoffi92/draft-ietf-idr-flow-spec-
       v6/tree/master/flowspec-cmp

Appendix A.  Example python code: flow_rule_cmp_v6

   <CODE BEGINS>
   """
   Copyright (c) 2020 IETF Trust and the persons identified as authors
   of draft-ietf-idr-flow-spec-v6. 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

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   4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info).
   """

   import itertools
   import collections
   import ipaddress

   EQUAL = 0
   A_HAS_PRECEDENCE = 1
   B_HAS_PRECEDENCE = 2
   IP_DESTINATION = 1
   IP_SOURCE = 2

   FS_component = collections.namedtuple('FS_component',
                                         'component_type value')

   class FS_IPv6_prefix_component:
       def __init__(self, prefix, offset=0,
                    component_type=IP_DESTINATION):
           self.offset = offset
           self.component_type = component_type
           # make sure if offset != 0 that non of the
           # first offset bits are set in the prefix
           self.value = prefix
           if offset != 0:
               i = ipaddress.IPv6Interface(
                   (self.value.network_address, offset))
               if i.network.network_address != \
                   ipaddress.ip_address('0::0'):
                   raise ValueError('Bits set in the offset')

   class FS_nlri(object):
       """
       FS_nlri class implementation that allows sorting.

       By calling .sort() on a array of FS_nlri objects these
       will be sorted according to the flow_rule_cmp algorithm.

       Example:
       nlri = [ FS_nlri(components=[
                FS_component(component_type=4,
                             value=bytearray([0,1,2,3,4,5,6])),
                ]),
                FS_nlri(components=[

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                FS_component(component_type=5,
                             value=bytearray([0,1,2,3,4,5,6])),
                FS_component(component_type=6,
                             value=bytearray([0,1,2,3,4,5,6])),
                ]),
              ]
       nlri.sort() # sorts the array accorinding to the algorithm
       """
       def __init__(self, components = None):
           """
           components: list of type FS_component
           """
           self.components = components

       def __lt__(self, other):
           # use the below algorithm for sorting
           result = flow_rule_cmp_v6(self, other)
           if result == B_HAS_PRECEDENCE:
               return True
           else:
               return False

   def flow_rule_cmp_v6(a, b):
       """
       Implementation of the flowspec sorting algorithm in
       draft-ietf-idr-flow-spec-v6.
       """
       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):
               if comp_a.offset < comp_b.offset:
                   return A_HAS_PRECEDENCE
               if comp_a.offset < comp_b.offset:
                   return B_HAS_PRECEDENCE
               # both components have the same offset

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               # assuming comp_a.value, comp_b.value of type
               # ipaddress.IPv6Network
               # and the offset bits are reset to 0 (since they are
               # not represented in the NLRI)
               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>

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Authors' Addresses

   Christoph Loibl (editor)
   next layer Telekom GmbH
   Mariahilfer Guertel 37/7
   Vienna  1150
   AT

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

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

   Email: robert@raszuk.net

   Susan Hares (editor)
   Huawei
   7453 Hickory Hill
   Saline, MI  48176
   USA

   Email: shares@ndzh.com

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