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Versions: (draft-hr-idr-rfc5575bis) 00 01 02 03 04 05 06 07 08 09

IDR Working Group                                               S. Hares
Internet-Draft                                                    Huawei
Obsoletes: 5575,7674 (if approved)                              C. Loibl
Intended status: Standards Track               Next Layer Communications
Expires: April 20, 2019                                        R. Raszuk
                                                            Bloomberg LP
                                                            D. McPherson
                                                                Verisign
                                                               M. Bacher
                                                        T-Mobile Austria
                                                        October 17, 2018


               Dissemination of Flow Specification Rules
                      draft-ietf-idr-rfc5575bis-09

Abstract

   This document defines a Border Gateway Protocol Network Layer
   Reachability Information (BGP NLRI) encoding 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 specifies IPv4 traffic Flow Specifications via a BGP NLRI which
   carries traffic Flow Specification filter, and an Extended community
   value which encodes 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 of IP addresses.

   This document obsoletes RFC5575 and RFC7674 to correct unclear
   specifications in the flow filters and to provide rules for actions
   which interfere (e.g. redirection of traffic and flow filtering).

   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 traffic filtering in
   the context of a BGP/MPLS VPN service, and 3) applications with
   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, and the strict actions
   encoded in the extended community Flow Specification actions.







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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 April 20, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Definitions of Terms Used in This Memo  . . . . . . . . . . .   5
   3.  Flow Specifications . . . . . . . . . . . . . . . . . . . . .   6
   4.  Dissemination of IPv4 FLow Specification Information  . . . .   7
     4.1.  Length Encoding . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  NLRI Value Encoding . . . . . . . . . . . . . . . . . . .   8
       4.2.1.  Type 1 - Destination Prefix . . . . . . . . . . . . .   8
       4.2.2.  Type 2 - Source Prefix  . . . . . . . . . . . . . . .   8
       4.2.3.  Type 3 - IP Protocol  . . . . . . . . . . . . . . . .   9
       4.2.4.  Type 4 - Port . . . . . . . . . . . . . . . . . . . .  10
       4.2.5.  Type 5 - Destination Port . . . . . . . . . . . . . .  10
       4.2.6.  Type 6 - Source Port  . . . . . . . . . . . . . . . .  10
       4.2.7.  Type 7 - ICMP type  . . . . . . . . . . . . . . . . .  11
       4.2.8.  Type 8 - ICMP code  . . . . . . . . . . . . . . . . .  11



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       4.2.9.  Type 9 - TCP flags  . . . . . . . . . . . . . . . . .  11
       4.2.10. Type 10 - Packet length . . . . . . . . . . . . . . .  12
       4.2.11. Type 11 -  DSCP (Diffserv Code Point) . . . . . . . .  12
       4.2.12. Type 12 - Fragment  . . . . . . . . . . . . . . . . .  12
     4.3.  Examples of Encodings . . . . . . . . . . . . . . . . . .  13
   5.  Traffic Filtering . . . . . . . . . . . . . . . . . . . . . .  14
     5.1.  Ordering of Traffic Filtering Rules . . . . . . . . . . .  15
   6.  Validation Procedure  . . . . . . . . . . . . . . . . . . . .  17
   7.  Traffic Filtering Actions . . . . . . . . . . . . . . . . . .  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 . . . . . . . . . . . . . . . . . . . . . . . . . . .  20
     7.3.  Traffic-action (traffic-action) sub-type 0x07 . . . . . .  20
     7.4.  RT Redirect (rt-redirect) sub-type 0x08 . . . . . . . . .  21
     7.5.  Traffic Marking (traffic-marking) sub-type 0x09 . . . . .  21
     7.6.  Rules on Traffic Action Interference  . . . . . . . . . .  21
       7.6.1.  Examples  . . . . . . . . . . . . . . . . . . . . . .  22
   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 . . . . . . . . . . . . . . . . . .  23
   9.  Limitations of Previous Traffic Filtering Efforts . . . . . .  23
     9.1.  Limitations in Previous DDoS Traffic Filtering Efforts  .  24
     9.2.  Limitations in Previous BGP/MPLS Traffic Filtering  . . .  24
   10. Traffic Monitoring  . . . . . . . . . . . . . . . . . . . . .  25
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25
     11.1.  AFI/SAFI Definitions . . . . . . . . . . . . . . . . . .  25
     11.2.  Flow Component Definitions . . . . . . . . . . . . . . .  26
     11.3.  Extended Community Flow Specification Actions  . . . . .  27
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  29
   13. Operational Security Considerations . . . . . . . . . . . . .  30
   14. Original authors  . . . . . . . . . . . . . . . . . . . . . .  30
   15. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  30
   16. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     16.1.  Normative References . . . . . . . . . . . . . . . . . .  30
     16.2.  Informative References . . . . . . . . . . . . . . . . .  32
     16.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  32
   Appendix A.  Comparison with RFC 5575 . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

1.  Introduction

   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.






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   These traffic policy mechanisms allow the router 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 document defines a general procedure to encode flow
   specification rules for aggregated traffic flows so that they can be
   distributed as a BGP [RFC4271] NLRI.  Additionally, we define the
   required mechanisms to utilize this definition to the problem of
   immediate concern to the authors: 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 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.
   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 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.




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   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
   extension is originated both manually as well as automatically.  The
   latter by systems that are able to detect malicious flows.  When
   automated systems are used, care should be taken to ensure their
   correctness as well as to limit the number and advertisement rate of
   flow routes.

   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],

2.  Definitions of Terms Used in This Memo

   NLRI -   Network Layer Reachability Information.

   RIB -   Routing Information Base.

   Loc-RIB -   Local RIB.

   AS -   Autonomous System.



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   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 if it matches all the specified
   criteria.

   A given flow 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 opaque 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 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.







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4.  Dissemination of IPv4 FLow Specification Information

   We define a "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 is
   treated as an opaque bit string prefix by BGP.  Each bit string
   identifies a key to a database entry with which a set of attributes
   can be associated.

   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 information, this
   shall be encoded as a 0-octet length Next Hop in the MP_REACH_NLRI
   attribute and ignored on 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)  |
       +------------------------------+
       |    NLRI value  (variable)    |
       +------------------------------+

                     Figure 1: Flow-spec 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), 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 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 value 241 is encoded as 0xf0f1.





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4.2.  NLRI Value Encoding

   The Flow Specification NLRI-type consists of several optional
   subcomponents.  A specific packet is considered to match the 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 must follow strict type ordering by
   increasing numerical order.  A given component type may (exactly
   once) or may not be present in the specification.  If present, it
   MUST precede any component of higher numeric type value.

   All combinations of component types within a single NLRI 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 cannot be used for traffic filtering purposes by the
   receiver.  Since a Flow Specification has the semantics of a logical
   AND of all components, if a component is FALSE, 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.

   The <type, value> encoding is chosen in order to allow for future
   extensibility.

4.2.1.  Type 1 - Destination Prefix

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

      Defines: the destination prefix to match.  Prefixes 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.







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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 operator byte is encoded as:

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

        Numeric operator

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

      a - AND 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 of the value field for this operand encodes 1 (00) -
      4 (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".









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            +----+----+----+----------------------------------+
            | lt | gt | eq | Resulting operation              |
            +----+----+----+----------------------------------+
            | 0  | 0  | 0  | true (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  | false (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.  This list is encoded using the numeric
      operator format defined in Section 4.2.3.  Values SHOULD be
      encoded as 1- or 2-byte quantities.

      Port, source port, and destination port components evaluate to
      FALSE if the IP protocol field of the packet has a value other
      than TCP or UDP, if the packet is fragmented and this is not the
      first fragment, or if the system in 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.

4.2.5.  Type 5 - Destination Port

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

      Defines a list of {operator, value} pairs used to match the
      destination port of a TCP or UDP packet.  This list is encoded
      using the numeric operator format defined in Section 4.2.3.
      Values SHOULD be encoded as 1- or 2-byte quantities.

4.2.6.  Type 6 - Source Port

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

      Defines a list of {operator, value} pairs used to match the source
      port of a TCP or UDP packet.  This list is encoded using the




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      numeric operator format defined in Section 4.2.3.  Values SHOULD
      be encoded as 1- or 2-byte quantities.

4.2.7.  Type 7 - ICMP type

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

      Defines a list of {operator, value} pairs used to match the type
      field of an ICMP packet.  This list is encoded using the numeric
      operator format defined in Section 4.2.3.  Values SHOULD be
      encoded using a single byte.

      The ICMP type specifiers evaluate to FALSE whenever the protocol
      value is not ICMP.

4.2.8.  Type 8 - ICMP code

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

      Defines a list of {operator, value} pairs used to match the code
      field of an ICMP packet.  This list is encoded using the numeric
      operator format defined in Section 4.2.3.  Values SHOULD be
      encoded using a single byte.

      The ICMP code specifiers evaluate to FALSE whenever the protocol
      value is not ICMP.

4.2.9.  Type 9 - TCP flags

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

      Bitmask values can be encoded as a 1- or 2-byte bitmask.  When a
      single byte is specified, it matches byte 13 of the TCP header
      [RFC0793], which contains bits 8 though 15 of the 4th 32-bit word.
      When a 2-byte encoding is used, it matches bytes 12 and 13 of the
      TCP header with the data offset field having a "don't care" value.

      This component evaluates to FALSE for packets that are not TCP
      packets.

      This type uses the bitmask operand format, which differs from the
      numeric operator format in the lower nibble.









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

      Bitmask format

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

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

   m -   Match bit.  If set, this is a bitwise match operation defined
      as "(data AND value) == value"; if unset, (data AND value)
      evaluates to TRUE if any of the bits in the value mask are set in
      the data

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

4.2.10.  Type 10 - Packet length

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

      Defines a list of {operator, value} pairs used to match on the
      total IP packet length (excluding Layer 2 but including IP
      header).  This list is encoded using the numeric operator format
      defined in Section 4.2.3.  Values SHOULD be encoded using 1- or
      2-byte quantities.

4.2.11.  Type 11 - DSCP (Diffserv Code Point)

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

      Defines a list of {operator, value} pairs used to match the 6-bit
      DSCP field [RFC2474].  This list is encoded using the numeric
      operator format defined in Section 4.2.3.  Values SHOULD be
      encoded using a single byte.  The six least significant bits
      contain the DSCP value.  All other bits SHOULD be encoded as zero
      and ignored on decoding.

4.2.12.  Type 12 - Fragment

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

      Uses bitmask operand format defined in Section 4.2.9.




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

      Bitmask values:

         Bit 7 - Don't fragment (DF)

         Bit 6 - Is a fragment (IsF)

         Bit 5 - First fragment (FF)

         Bit 4 - Last fragment (LF)

         Bit 0-3 - SHOULD be set to 0 on NLRI encoding, and MUST be
         ignored during decoding

4.3.  Examples of Encodings

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

      +------------------+----------+----------+
      | destination      | proto    | port     |
      +------------------+----------+----------+
      | 0x01 18 0a 00 01 | 03 81 06 | 04 81 19 |
      +------------------+----------+----------+

   Decode for protocol:

      +-------+----------+------------------------------+
      | Value |          |                              |
      +-------+----------+------------------------------+
      |  0x03 | type     |                              |
      |  0x81 | operator | end-of-list, value size=1, = |
      |  0x06 | value    |                              |
      +-------+----------+------------------------------+

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

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




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   Decode for port:

      +--------+----------+------------------------------+
      |  Value |          |                              |
      +--------+----------+------------------------------+
      |   0x04 | type     |                              |
      |   0x03 | operator | size=1, >=                   |
      |   0x89 | value    | 137                          |
      |   0x45 | operator | "AND", value size=1, <=      |
      |   0x8b | value    | 139                          |
      |   0x91 | operator | end-of-list, value-size=2, = |
      | 0x1f90 | value    | 8080                         |
      +--------+----------+------------------------------+


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

5.  Traffic Filtering

   Traffic filtering policies have been traditionally considered to be
   relatively static.  Limitations of the static mechanisms caused this
   mechanism to be designed for the three new applications of traffic
   filtering (prevention of traffic-based, denial-of-service (DOS)
   attacks, traffic filtering in the context of BGP/MPLS VPN service,
   and centralized traffic control for SDN/NFV networks) requires
   coordination among service providers and/or coordination among the AS
   within a service provider.  Section 8 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 Flow Specification NLRI defined above to convey information
   about traffic filtering rules for traffic that should be discarded or
   handled in 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






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   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 of the IPv4 Flow Specification is described in section
   6, and distibution of BGP/MPLS traffic Flow Specification is
   described in section 8.  The traffic filtering actions are described
   in section 7.

5.1.  Ordering of Traffic Filtering Rules

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

   The relative order of two Flow Specification rules is determined by
   comparing their respective components.  The algorithm starts by
   comparing the left-most components of the rules.  If the types
   differ, the rule with lowest numeric type value has higher precedence
   (and thus will match before) than the rule 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 the
   prefixes overlap, the one with the longer prefix-length has higher
   precedence.  If they do not overlap 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.
   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 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



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   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 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:



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                       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 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 Flow Specification NLRI,
   to allow other validation procedures.

   A Flow Specification NLRI must be validated such that it is
   considered feasible if and only if:

      a) The originator of the Flow Specification matches the originator
      of the best-match unicast route for the destination prefix
      embedded in the Flow Specification.

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

   By originator of a BGP route, we mean either the BGP originator path
   attribute, as used by route reflection, or the transport 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




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   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 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.

   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 defines a minimum set of 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 Flow Specification is to
   accept IP traffic that matches that particular rule.

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







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   +-----------+----------------------+--------------------------------+
   | community | action               | encoding                       |
   +-----------+----------------------+--------------------------------+
   | 0x8006    | traffic-rate-bytes   | 2-byte ASN, 4-byte float       |
   | TBD       | traffic-rate-packets | 2-byte ASN, 4-byte float       |
   | 0x8007    | traffic-action       | bitmask                        |
   | 0x8008    | rt-redirect AS-2byte | 2-octet AS, 4-octet value      |
   | 0x8108    | rt-redirect IPv4     | 4-octet IPv4 addres, 2-octet   |
   |           |                      | value                          |
   | 0x8208    | rt-redirect AS-4byte | 4-octet AS, 2-octet value      |
   | 0x8009    | traffic-marking      | DSCP value                     |
   +-----------+----------------------+--------------------------------+

               Table 2: Traffic Action Extended Communities

   Some traffic action communities may interfere with each other.
   Section 7.6 of this specification provides rules for handling
   interference between specific types of traffic actions, and error
   handling based on [RFC7606].  Any additional definition of a traffic
   actions specified by additional standards documents or vendor
   documents MUST specify if the traffic action interacts 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).

   All traffic 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



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   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 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 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       | S | T |
       +---+---+---+---+---+---+---+---+

   where S and T are defined as:

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

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

   o  reserved: should always be set to 0 by the originator and not be
      evaluated by the receiving BGP speaker.

   The use of the Terminal Action (bit 47) may result in more than one
   filter-rule matching a particular flow.  All the flow actions from
   these rules shall be collected and applied.  If interfering actions
   have been collected only the first occurence SHALL be applied.



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   However, if a single rule contains interfering actions this rule
   SHALL still be handled as described in Section 7.6.

   Interferes with: No other BGP Flow Specification traffic 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 allows 3 different encodings formats for the
   route-target (type 0x80, 0x81, 0x82).  Is 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 Sections 3.1, 3.2, and 4 of [RFC4360] plus Section 2 of
   [RFC5668].)  The low-order octet (Sub-Type) of the Redirect Extended
   Community remains 0x08 for all three encodings of the BGP Extended
   Communities (AS 2-byte, AS 4-byte, and IPv4 address).

   Interferes with: All other redirect functions.  All redirect
   functions are mutually exclusive.  If this redirect function exists,
   then no other redirect functions can be processed.

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

   The traffic marking extended community instructs a system to modify
   the DSCP bits 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.

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

7.6.  Rules on Traffic Action Interference

   Traffic actions may interfere with each other.  If interfering
   traffic actions are present for a single Flow Specification NLRI the
   entire Flow Specification (irrespective if there are any other non
   conflicting actions associated with the same Flow Specification)
   SHALL be treated as BGP WITHDRAW.





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   This document defines 7 traffic actions which are interfering in the
   following way:

   1.  Redirect-action-communities (0x8008, 0x8108, 0x8208):

       The three redirect-communities are mutually exclusive.  Only a
       single redirect community may be associated with a Flow
       Specification otherwise they are interfering.

   2.  All traffic-action communities (including redirect-actions):

       Multiple occurences of the same (sub-type and type) traffic-
       action associated with a Flow Specification are always
       interfering.

   When a traffic action is defined in a standards document the handling
   of interaction with other/same traffic actions MUST be defined as
   well.  Invalid interactions between actions SHOULD NOT trigger a BGP
   NOTIFICATION.  All error handling for error conditions based on
   [RFC7606].

7.6.1.  Examples

      (rt-redirect vrf-a, rt-redirect vrf-b, traffic-rate-bytes 1Mbit/s)

      RT-redirect vrf-a and rt-redirect vrf-b are interfering: The BGP
      UPDATE is treated as WITHDRAW.

      (rt-redirect vrf-a, traffic-rate-bytes 1Mbit/s, traffic-rate-bytes
      2Mbit/s)

      Duplicate traffic-rate-bytes are interfering: The BGP UPDATE is
      treated as WITHDRAW.

      (rt-redirect vrf-a, traffic-rate-bytes 1Mbit/s, traffic-rate-
      packets 1000)

      No interfering action communities: The BGP UPDATE is subject to
      further processing.

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



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   table environment within this document.  This document proposes an
   additional BGP NLRI type (AFI=1, SAFI=134) value, which can be used
   to propagate traffic filtering information 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 Section 4.2 of this document.
   The NLRI length field shall include both the 8 bytes of the Route
   Distinguisher as well as the subsequent Flow Specification.

       +------------------------------+
       | 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].

   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








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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 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 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

   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.

   In these environments, the VPN customer network often has traffic
   filtering capabilities towards their external network connections



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   (e.g., firewall facing public network connection).  Less common is
   the presence of traffic filtering capabilities between different VPN
   attachment sites.  In an any-to-any connectivity model, which is the
   default, this means that site-to-site traffic is unfiltered.

   In circumstances where a security threat does get propagated inside
   the VPN customer network, there may not be readily available
   mechanisms to provide mitigation via traffic filter.

   But also Internet service providers may use those VPNs 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 Flow Specification addresses these limitations.

10.  Traffic Monitoring

   Traffic filtering applications require monitoring and traffic
   statistics facilities.  While this is an 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.

11.  IANA Considerations

   This section complies with [RFC7153].

11.1.  AFI/SAFI Definitions

   IANA maintains a registry entitled "SAFI Values".  For the purpose of
   this work, IANA updated the registry and allocated two additional
   SAFIs:

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

                      Table 3: Registry: SAFI Values





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11.2.  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".  This
   document defines the following Component Type Codes:

             +-------+--------------------+-----------------+
             | 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] used:

             +--------------+-------------------------------+
             | Range        | Policy                        |
             +--------------+-------------------------------+
             | 0            | Invalid value                 |
             | [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 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.






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11.3.  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 the registry to contain the values listed 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 Transitive Experimental Use Extended
                              Community Types

   Note-1: This document obsoletes RFC7674.

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











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

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

   Note-3: This document obsoletes RFC7674, and becomes the only
   reference for this table.





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   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".  These values should be assigned via IETF
   Review rules only.  The following traffic-action fields have been
   allocated:

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

                 Table 10: Registry: Traffic Action Fields

12.  Security Considerations

   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 of this proposal are equivalent to the
   existing security properties of BGP unicast routing.  However, this
   document also specifies traffic filtering actions that may need
   custom additional verification on the receiver side.  See Section 13.

   Where it is not the case, this would open the door to further denial-
   of-service attacks.

   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.







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13.  Operational Security Considerations

   While the general verification of the traffic filter NLRI is
   specified in this document (Section 6) the 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 of action communities at network borders and by
   mapping user-defined communities (see Section 7) to expose certain
   forwarding properties to third parties.

   Since verfication of the traffic filtering NLRI is tied to the
   announcement of the best unicast route, a unfiltered address space
   hijack (e.g. advertisement of a more specific route) may cause this
   verification to fail and consequently prevent Flow Specification
   filters from being accepted by a peer.

14.  Original authors

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

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.  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.

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

16.  References

16.1.  Normative References

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

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



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   [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, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [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>.

   [RFC4761]  Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
              LAN Service (VPLS) Using BGP for Auto-Discovery and
              Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
              <https://www.rfc-editor.org/info/rfc4761>.

   [RFC4762]  Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
              LAN Service (VPLS) Using Label Distribution Protocol (LDP)
              Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
              <https://www.rfc-editor.org/info/rfc4762>.

   [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>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.



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   [RFC6482]  Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
              Origin Authorizations (ROAs)", RFC 6482,
              DOI 10.17487/RFC6482, February 2012,
              <https://www.rfc-editor.org/info/rfc6482>.

   [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 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>.

16.3.  URIs

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

Appendix A.  Comparison with RFC 5575

   This document includes numerous editorial changes to RFC5575.  It is
   recommended to read the entire document.  The authors, however want
   to point out the following technical changes to RFC5575:

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



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

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

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

      Section 7.4 contains the same redirect actions already defined in
      RFC5575 however, these actions have been renamed to "rt-redirect"
      to make it clearer that the redirection is based on route-target.

      Section 7.6 introduces rules how updates of Flow Specifications
      shall be handled in case they contain interfering actions.
      Section 7.3 also cross-references this section.  RFC5575 did not
      define this.

Authors' Addresses

   Susan Hares
   Huawei
   7453 Hickory Hill
   Saline, MI  48176
   USA

   Email: shares@ndzh.com


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

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











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   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




























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