Internet-Draft BGP FlowSpec v2 July 2021
Hares Expires 13 January 2022 [Page]
Workgroup:
IDR Working Group
Internet-Draft:
draft-hares-idr-flowspec-v2-01
Published:
Intended Status:
Standards Track
Expires:
Author:
S. Hares
Hickory Hill Consulting

BGP Flow Specification Version 2

Abstract

BGP flow specification version 1 (RFC8955, RFC8956) describes the distribution of traffic filter policy (traffic filters and actions) which are distributed via BGP to BGP peers. Multiple applications utilize the BGP distributed traffic filter policy. These applications include: (1) mitigation of Denial of Service (DoS), (2) enabling of traffic filtering in BGP/MPLS VPNS, (3)centralized traffic control for networks utilizing either SDN control of router firewall functions. During the deployment of BGP flow specification v1, the following issues were detected: 1) problems due to the lack of clear TLV encoding for rules for flow specifications, 2) desire to order filters rules, and 3) ordering of actions to provide deterministic actions. Version 2 of the BGP flow specification protocol addresses these features.

BGP Flow Specification v2 is encapsulated in a different NLRI which encapsulates previous flow specification informatino.

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 13 January 2022.

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Table of Contents

1. Introduction

BGP ([RFC4271]) flow specification (see [RFC8955] and [RFC8956]) describes the distribution of traffic filter policy (traffic filters and actions) which are distributed via BGP to BGP peers. The traffic filter policy is applied when packets are received on a router with the flow specification function turned on. Multiple applications utilize the BGP distributed traffic filter policy. These applications include: (1) mitigation of Denial of Service (DoS), (2) enabling of traffic filtering in BGP/MPLS VPNS, and (3)centralized traffic control for networks utilizing either SDN control of router firewall functions. During the deployment of BGP flow specification v1, the following issues were detected:

Version 2 of the BGP flow specification protocol addresses these features.

This document describes distribution of three new BGP Flow Specification NLRI (3 AFIs (1, 2, and 6) with SAFI (TBD) that allow user-ordered list of traffic match filters, and user-ordered traffic match actions encoded in BGP Wide Communities. This document contains a overview in this section and the following other sections:

This section reviews the existing flow specification and provides a logical description of ordered flow specification.

1.1. Flow Specification v1 Review

If one considers the reception of the packet as an event, then BGP flow specification describes a set of minimalistic Event-MatchCondition-Action (ECA) policies where the match-condition is defined in the BGP NLRI, and the action is defined either by the default condition (accept traffic) or actions defined in Extended BGP Community values [RFC4360].

The initial set of policy [RFC8955] and [RFC8956] for this policy includes 13 types of match filters encoded the following: specific AFI/SAFIs for the IPv4 and IPv6 AFIs:

  • IPv4 traffic: AFI:1, SAFI:133;
  • IPv6 Traffic: AFI:2 SAFI:133
  • BGP/MPLS IPv4 VPN: AFI:1, SAFI: 134
  • BGP/MPLS IPv6 VPN: AFI:2, SAFI: 134

The 13 types of filters are the following:

  • Type 1: Destination Prefix
  • Type 2: Source Prefix
  • Type 3: IP Protocol (v4,[RFC8955] ) or Upper Layer Protocol (v6, [RFC8956])
  • Type 4: Port
  • Type 5: Destination Port
  • Type 6: Source Port
  • Type 7: ICMPv4 Type (v4,[RFC8955] ) or ICMPv6 Type (v6, [RFC8956])
  • Type 8: ICMPv4 Code (v4,[RFC8955] ) or ICMPv6 code(v6, [RFC8956])
  • Type 9: TCP flags (v4,[RFC8955] )
  • Type 10: Packet length
  • Type 11: DSCP marking
  • Type 12: Fragment
  • Type 13: Flow Label (v6, [RFC8956])

The actions proposed in [RFC8955] and [RFC8956] for exclusion on Extended Community (0xttss) are the following:

  • Traffic rate limited by bytes (0x8006) [2 byte AS, 4 byte float]
  • Traffic action (set by bitmask, bits 47 and 46 defined) (0x8007)
  • rt-redirect IPv4 (0x8008) [2 byte AS, 4 octet value]
  • rt-redirect IPv4 (0x8108) [4 byte IPv4 address, 2 octet value]
  • rt-redirect IPv4 (0x8108) [4 byte AS, 2 octet value]
  • traffic marking (0x8009) (DSCP value)
  • Traffic rate limited by packets (0x800C) [2 byte AS, 4 byte float]
  • rt-redirect IPv6 (0x820D) [2 byte AS, 4 octet value]
  • rt-redirect IPv6 (0x810D) [4 byte IPv4 address, 2 octet value]
  • rt-redirect IPv6 (0x820D) [4 byte AS, 2 octet value]

The flow specification filers and actions combine to make up flow specification rules associated with an NRLI. The Extended Communities for actions can be attached to a single rule or multiple rules. Figure 1 shows a diagram of the flow specification data structures.


     +--------------------------------------+
     | Flow Specification (FS)              |
     |  Policy                              |
     +--------------------------------------+
         ^               ^              ^
         |               |              |
         |               |              |
+--------^----+  +-------^-------+     +-------------+
|   FS Rule1  |  |   FS Rule     | ... |  FS rule    |
+-------------+  +---------------+     +-------------+
                    :          :
                    :          :
                 ...:          :........
                 :                     :
       +---------V---------+      +----V-------------+
       |  Rule Condition   |      |   Rule Action    |
       |  in BGP NLRIs     |      | in BGP extended  |
           | AFIs: 1 and 2     |      | Communities      |
       | SAFI 133, 134     |      |                  |
       +-------------------+      +------------------+
           :     :    :                 :      :    :
      .....:     .    :.....       .....:      .    :.....
      :          :         :       :           :         :
 +----V---+  +---V----+ +--V---+ +-V------+ +--V-----++--V---+
 |  Match |  | match  | |match | | Action | | action ||action|
 |Operator|  |Variable| |Value | |Operator| |variable|| Value|
 |*1      |  |        | |      | |(subtype| |        ||      |
 +--------+  +--------+ +------+ +--------+ +--------++------+

   *1 match operator may be complex.

   Figure 1: BGP Flow Specification Policy

1.2. Order Flow Specification Data Proposed for v2

An minimal ordered specification of the rules would include an order indicator per rule. The inclusion of names for each rule, match condition and action allows for logical indirection. The existing extended community which tags multiple NLRIs could be saved as an indirect reference by name. For Flow specification v1 actions, the Extended actions could be assigned default names. The actions could be linked to many NLRIs. Figure 2 below provides a logical diagram of the ordering of rules and the association of names per rule, rule match action, and rule action.

Since many policies also group data flow specifications under rule groups, many implementations may order set of rules under a particular group policy. Network Management display of BGP filers may use the Rule Grouping mechanism to display the filters.


       +--------------------------------+
       |          Rule Group            |
       +------------------------------ -+
         ^          ^                  ^
                 |          ----------         |
         |                   |             ------
         |                   |               |
+--------^-------+   +-------^-----+     +---^-----+
|      Rule1     |   |     Rule2   | ... |  Rule-n |
+----------------+   +-------------+     +---------+
                      :  :   :    :
    :.................:  :   :    :
    :          |.........:   :    :
 +--V--+    +--V--+          :    :
 | name|    |order| .........:    :.....
 +-----+    +-----+ :                  :
                    :                  :
   +----------------V----+  +-----V-------  --+
   |Rule Match condition |  | Rule Action     |
   +---------------------+  +-----------------+
    :      :     :    :       :      :   :   :
 +--V--+   :     :    :    +--V--+   :   :   :
 | name|   :     :    :    |name |   :   :   :
 +-----+   :     :    :    +-----+       :   :   :
           :     :    :              :   :   :...........
           :     :    :              :   :              :
      .....:     .    :.....       ..:   :.....         :
      :          :         :       :          :         :
 +----V---+  +---V----+ +--V---+ +-V------++--V-----++--V---+
 |  Match |  | match  | |match | | Action || action ||action|
 |Operator|  |variable| |Value | |Operator||Variable|| Value|
 +--------+  +--------+ +------+ +--------++--------++------+

   Figure 2: Order Flow Specification Data storage

2. Definitions

2.1. Definitions and Acronyms

2.2. RFC 2119 language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

3. Dissemination of BGP Flow Specification version 2 NLRI

The BGP Flow Specification version 2 (BGP-FS v2) uses an NRLI with the format for AFIs for IPv4 (AFI = 1), IPv6 (AFI = 2), and L2VPN (L2VPN = 6) with a SAFI of (TBD=xx). This NLRI information is encoded using MP_READ_NRI and MP_UNREACH_NLRI attributes defined in [RFC4760]. Whenever the corresponding application does not require Next-HOP information, this shall be encoded as zero-octet length Next Hop in the MP_REAC_NLRI and ignored upon receipt.

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], and indicate a capability for flow specification v2 (TBD).

3.1. Encoding of BGP-FS v2 Filters

The AFI/SAFI NLRI for BGP Flow Specification has the format:

 +------------------------+
 |length (2 octets)       |
 +------------------------+
 | Sub-TLVs (variable)    |
 | +====================+ |
 | | order (2 octets)   | |
 | +--------------------+ |
 | | type (2 octets)    | |
 | +--------------------+ |
 | | length (2 octets)  | |
 | +--------------------+ |
 | | value (variable)   | |
 | +====================+ |
 +------------------------+

 Figure 3 -Flow Specification v2 format

where:

Filters are processed in the order specified by the user.

3.1.1. Encoding of Value field for Rule Identification (Value = 00)

The BGP flow specification V2 identifier sub-TLVs use the following format:

 +------------------------+
 |length (2 octets)       |
 +------------------------+
 | Sub-TLVs (variable)    |
 | +====================+ |
 | | order (2 octets)   | |
 | +--------------------+ |
 | | type = 00          | |
 | +--------------------+ |
 | | length (4 octets)  | |
 | +--------------------+ |
 | | identifier for     | |
 | | rule (variable)    | |
 | +====================+ |
 +------------------------+

 Figure 4 - NRLI revision

The octets for the identifier are string of octets of variable length.

3.1.2. Encoding of Value field for default Action of Block traffic (Value = 01)

The BGP flow specification V2 identifier sub-TLVs use the following format:

 +--------------------------+
 |length (2 octets)         |
 +--------------------------+
 | Sub-TLVs (variable)      |
 | +======================+ |
 | | order (2 octets)     | |
 | +----------------------+ |
 | | type = 01            | |
 | +----------------------+ |
 | | length (variable)    | |
 | +----------------------+ |
 | | value field          | |
 | | AFI/SAFI field (4)   | |
 | | components (variable | |
 | +======================+ |
 +--------------------------+

 Figure 5 - Flow specification v2
 with default Block traffic flow

Flow Specification v2 with a default Action of block traffic has the following sub-TLVs in the value field:

  • a value of an AFI/SAFI field with 4 bytes [AFI 2 Bytes, SAFI 1 byte, 1 Byte reserved]

  • Component fields as defined in the following documents:

3.1.3. Encoding of Value field for default Action of Permit traffic (Value = 02)

The BGP flow specification V2 identifier sub-TLVs use the following format:

 +--------------------------+
 |length (2 octets)         |
 +--------------------------+
 | Sub-TLVs (variable)      |
 | +======================+ |
 | | order (2 octets)     | |
 | +----------------------+ |
 | | type = 01            | |
 | +----------------------+ |
 | | length (variable)    | |
 | +----------------------+ |
 | | value field          | |
 | | AFI/SAFI field (4)   | |
 | | components (variable | |
 | +======================+ |
 +--------------------------+

 Figure 6 - Flow specification v2
 with default permit traffic flow

Flow Specification v2 with Filters and Default action of block traffic has the following sub-TLVs in the value field:

  • a value of an AFI/SAFI field with 4 bytes [AFI 2 Bytes, SAFI 1 byte, 1 Byte reserved]

  • Component fields as defined in the following documents:

3.1.4. Encoding of Value field filters plus actions(Value = 03)

The BGP flow specification V2 identifier sub-TLVs use the following format:

 +----------------------------+
 |length (2 octets)           |
 +----------------------------+
 | Sub-TLVs (variable)        |
 | +=======================+  |
 | | order (2 octets)      |  |
 | +-----------------------+  |
 | | type = 01             |  |
 | +-----------------------+  |
 | | length (variable)     |  |
 | +-----------------------+  |
 | | value field           |  |
 | |                       |  |
 | | Action length   (4)   |  |
 | | Action sub-TLVs (var) |  |
 | | number of filters     |  |
 | | [filter 1]            |  |
 | | AFI/SAFI field (4)    |  |
 | | components (variable) |  |
 | | [filter 2]            |  |
 | | AFI/SAFI field (4)    |  |
 | | components (variable) |  |
 | | ....                  |  |
 | +=======================+  |
 +----------------------------+

 Figure 7 - Flow Specification with
 Actions encoded in NLRI

The Flow Specification v2 with action fields applies actions to the AFI/SAFI field. The format of the field is

  • Action length (4 bytes)

  • Action SubTLVs (variable) in format Type (2 bytes), length (2 bytes), and value (variable). The types are:

    • Extended community (01)
    • Wide Community (02) 
      [Type (2 bytes)][Extended-Community-type (2 bytes)][6 bytes]

 Figure 8 - Extended Community action type encoding

    The Extended community types are the following:

    • Type 1: Traffic rate limited by bytes (0x8006) [2 byte AS, 4 byte float]
    • Type 2: Traffic action (set by bitmask, bits 47 and 46 defined) (0x8007)
    • Type 3: rt-redirect IPv4 (0x8008) [2 byte AS, 4 octet value]
    • Type 4: rt-redirect IPv4 (0x8108) [4 byte IPv4 address, 2 octet value]
    • Type 5: rt-redirect IPv4 (0x8108) [4 byte AS, 2 octet value]
    • Type 6: traffic marking (0x8009) (DSCP value)
    • Type 7: Traffic rate limited by packets (0x800C) [2 byte AS, 4 byte float]
    • Type 8: rt-redirect IPv6 (0x820D) [2 byte AS, 4 octet value]
    • Type 9: rt-redirect IPv6 (0x810D) [4 byte IPv4 address, 2 octet value]
    • Type 10: rt-redirect IPv6 (0x820D) [4 byte AS, 2 octet value]

  • Component fields as defined in the following documents:

The BGP-FS version 2 actions are passed in a Wide Community [I-D.ietf-idr-wide-bgp-communities] atom with the following format.

3.1.5. Encoding of Value Fields filters passed in Wide Communities (Value = 04)

The BGP-FS version 2 actions are passed in a Wide Community [I-D.ietf-idr-wide-bgp-communities] atom with the following format:

 +----------------------------+
 |length (2 octets)           |
 +----------------------------+
 | Sub-TLVs (variable)        |
 | +=======================+  |
 | | order (2 octets)      |  |
 | +-----------------------+  |
 | | type = 01             |  |
 | +-----------------------+  |
 | | length (variable)     |  |
 | +-----------------------+  |
 | | value field           |  |
 | |                       |  |
 | | Action length(4)      |  |
 | | Atom-id-1  (4)        |  |
 | | Atom-id-2 (4)         |  |
 | | number of filters     |  |
 | | [filter 1]            |  |
 | | AFI/SAFI field (4)    |  |
 | | components (variable) |  |
 | | [filter 2]            |  |
 | | AFI/SAFI field (4)    |  |
 | | components (variable) |  |
 | | ....                  |  |
 | +=======================+  |
 +----------------------------+

 Figure 9 - Flow Specification with
 IDs for Wide Community Actions

The BGP Atom IDs in the Wide Community must contain:

+--------------------------+
| Atom ID (4 octets)       |
+--------------------------+
| order (2 octets)         |
+--------------------------+
| Action type (2 octets)   |
+--------------------------+
| Action length (2 octets) |
+--------------------------+
| Action Values (variable) |
| (multiples of 2 octets)  |
+--------------------------+

Figure 10
Wide Community Atom

where:

  • Action type (2 octets) - is the type of action. These actions can be standardized (0x0001 - 0x3ffff), vendor specific (0x40000-0x7FFFF), or reserved (0x0, 0x80000-0xFFFFFFFF).
  • Action length - length of actions including variable field,
  • Action values - value of actions (variable) defined in individual definitions.

The BGP Flow Specification (BGP-FS) atom can be part of the Wide Community container (type 1) or the BGP Flow Specification Atom can be part of the BGP Flow Specification container (type 2) which will have:

+-----------------------------+
| Source AS Number  (4 octets)|
+-----------------------------+
| list of atoms (variable)    |
+-----------------------------+
figure 11

3.1.6. Encoding of Value Fields filters for Tunnels (Value = 05)

This section needs to be discussed with the authors of draft-ietf-idr-flowspec-nv03.

4. Optional Security Additions

This section discusses the optional BGP Security additions for BGP-FS v2 relating to BGPSEC [RFC8205] and ROA.

4.1. BGP FS v2 and BGPSEC

Flow specification v1 ([RFC8955] and [RFC8956]) do not BGP Flow specifications to be passed BGPSEC [RFC8205] BGP Flow Specification v2 can be passed in BGPSEC, but it is not required.

4.2. BGP FS v2 with with ROA

BGP Flow Specification v2 can utilize ROAs in the validation. If BGP-FS v2 is used with BGPSEC and ROA, the first thing is to validate the route within BGPSEC and second to utilize BGP ROA to validate the route origin.

The BGP-FS peers using both ROA and BGP-FS validation determine that a BGP Flow specification is valid if and only if one of the following cases:

The best match is defined to be the longest-match NLRI with the highest preference.

4.3. Revise Flow Specification Security for centralized Server

The distribution of Flow Specifications from a centralized server supports mitigation of DoS attacks. [I-D.ietf-idr-bgp-flowspec-oid] suggests the following redefined procedure for validation for this case:

A route is valid if the following conditions holds true:

This reduced validation mechanism can be used for BGP-FS v2 within a single domain.

5. IANA Considerations

This section complies with [RFC7153]

This document requests:

Registry be created for BGP-FS V2 filter component types with the following ranges:

Registry be created for BGP-FS v2 action types with the following ranges:

6. Security Considerations

The use of ROA improves on [RFC8955] to check the route orgination is valid can improve the validation sequence for a multiple-AS environment. The use of BGPSEC [RFC8205] to secure the packet can increase security of BGP flow specification information sent in the packet.

The use of the reduced validation within an AS [I-D.ietf-idr-bgp-flowspec-oid] can provide adequate validation for distribution of flow specification within an single autonomous system for prevention of DDOS.

Distribution of flow filters may provide insight into traffic being sent within an AS, but this information should be composite information that does not reveal the traffic patterns of individuals.

7. References

7.1. Normative References

[I-D.ietf-idr-bgp-flowspec-oid]
Uttaro, J., Alcaide, J., Filsfils, C., Smith, D., and P. Mohapatra, "Revised Validation Procedure for BGP Flow Specifications", Work in Progress, Internet-Draft, draft-ietf-idr-bgp-flowspec-oid-13, , <https://www.ietf.org/archive/id/draft-ietf-idr-bgp-flowspec-oid-13.txt>.
[I-D.ietf-idr-wide-bgp-communities]
Raszuk, R., Haas, J., Lange, A., Decraene, B., Amante, S., and P. Jakma, "BGP Community Container Attribute", Work in Progress, Internet-Draft, draft-ietf-idr-wide-bgp-communities-05, , <https://www.ietf.org/archive/id/draft-ietf-idr-wide-bgp-communities-05.txt>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <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, , <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, , <https://www.rfc-editor.org/info/rfc4360>.
[RFC4760]
Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, , <https://www.rfc-editor.org/info/rfc4760>.
[RFC7153]
Rosen, E. and Y. Rekhter, "IANA Registries for BGP Extended Communities", RFC 7153, DOI 10.17487/RFC7153, , <https://www.rfc-editor.org/info/rfc7153>.
[RFC8955]
Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M. Bacher, "Dissemination of Flow Specification Rules", RFC 8955, DOI 10.17487/RFC8955, , <https://www.rfc-editor.org/info/rfc8955>.
[RFC8956]
Loibl, C., Ed., Raszuk, R., Ed., and S. Hares, Ed., "Dissemination of Flow Specification Rules for IPv6", RFC 8956, DOI 10.17487/RFC8956, , <https://www.rfc-editor.org/info/rfc8956>.

7.2. Informative References

[RFC6241]
Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, , <https://www.rfc-editor.org/info/rfc6241>.
[RFC8040]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, , <https://www.rfc-editor.org/info/rfc8040>.
[RFC8205]
Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol Specification", RFC 8205, DOI 10.17487/RFC8205, , <https://www.rfc-editor.org/info/rfc8205>.
[RFC8206]
George, W. and S. Murphy, "BGPsec Considerations for Autonomous System (AS) Migration", RFC 8206, DOI 10.17487/RFC8206, , <https://www.rfc-editor.org/info/rfc8206>.

Author's Address

Susan Hares
Hickory Hill Consulting
7453 Hickory Hill
Saline, MI 48176
United States of America