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A Discard Prefix for IPv6

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 6666.
Author Nick Hilliard
Last updated 2012-02-02 (Latest revision 2012-01-09)
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state WG Document
Document shepherd (None)
IESG IESG state Became RFC 6666 (Informational)
Consensus boilerplate Unknown
Telechat date (None)
Needs a YES.
Responsible AD Ron Bonica
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Send notices to,
v6ops Working Group                                          N. Hilliard
Internet-Draft                                                      INEX
Updates: 5156 (if approved)                              January 9, 2012
Intended status: Informational
Expires: July 12, 2012

                       A Discard Prefix for IPv6


   Remote triggered black hole filtering describes a method of
   militating against denial-of-service attacks by selectively
   discarding traffic based on source or destination address.  Remote
   triggered black hole routing describes a method of selectively re-
   routing traffic into a sinkhole router (for further analysis) based
   on destination address.  This document updates RFC5156 by explaining
   why a unique IPv6 prefix should be formally assigned by IANA for the
   purpose of facilitating IPv6 remote triggered black hole filtering
   and routing.

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

   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 July 12, 2012.

Copyright Notice

   Copyright (c) 2012 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
   ( in effect on the date of
   publication of this document.  Please review these documents

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . . . 3
   2.  A Discard Prefix for IPv6 . . . . . . . . . . . . . . . . . . . 4
   3.  Operational Implications  . . . . . . . . . . . . . . . . . . . 4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 5

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1.  Introduction

   Remote triggered black hole (RTBH) filtering describes a class of
   methods of blocking IP traffic either from a specific source
   ([RFC5635]) or to a specific destination ([RFC3882]) on a network.
   Remote triggered black hole (RTBH) routing describes a class of
   methods of re-routing IP traffic destined to the attacked/targeted
   host to a special path (tunnel) where a sniffer could capture the
   traffic for analysis.  These methods operate by setting the next-hop
   address of an IP packet with a specified source or destination
   address to be a unicast prefix which is wired locally or remotely to
   a router's discard, null or tunnel interface.  Typically, this
   information is propagated throughout an autonomous system using a
   dynamic routing protocol such as BGP ([RFC3882]).  By deploying RTBH
   systems across a network, traffic to or from specific destinations
   may be selectively black-holed or re-routed to a sinkhole device in a
   manner which is efficient, scalable and straightforward to implement.
   For IPv4, some networks configure RTBH installations using [RFC1918]
   address space or the address blocks reserved for documentation in

   However RTBH configurations are not documentation, but operationally
   important features of many public-facing production networks.
   Furthermore, [RFC3849] specifies that the IPv6 documentation prefix
   should be filtered in both local and public contexts.  On this basis,
   it is suggested that both private network address blocks and
   documentation prefixes described in [RFC5737] are inappropriate for
   the purpose of RTBH configurations.

   While it could be argued that there are other addresses and address
   prefixes which could be used for this purpose (e.g. ::/128), or that
   an operator could assign an address block from their own address
   space for this purposes, there is currently no operational clarity on
   what address block would be appropriate or inappropriate to use for
   this purpose.  By assigning a globally unique discard prefix for
   IPv6, the IETF will introduce good practice for the implementation of
   IPv6 RTBH configurations and will facilitate operational clarity by
   allowing operators to implement consistent and deterministic inter-
   domain prefix and traffic filtering policies for black-holed traffic.

   This document updates [RFC5156].

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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2.  A Discard Prefix for IPv6

   For the purposes of implementing an IPv6 remote triggered black hole
   configuration, a unicast address block is required.  There are
   currently no IPv6 unicast address blocks which are specifically
   nominated for the purposes of implementing such RTBH systems.

   As [RFC3882] and [RFC5635] describe situations where more than one
   discard address may be used for implementing multiple remote
   triggered black hole scenarios, a single assigned prefix is not
   sufficient to cover all likely RTBH situations.  Consequently, an
   address block is required in preference to a single address.

3.  Operational Implications

   This assignment MAY be carried in a dynamic routing protocol within
   an autonomous system.  The assignment SHOULD NOT be announced to or
   accepted from third party autonomous systems and IPv6 traffic with a
   destination address within this prefix SHOULD NOT be forwarded to or
   accepted from third party autonomous systems.

   On networks which implement IPv6 remote triggered black holes, some
   or all of this network block MAY be configured with a destination of
   a discard or null interface on any or all IPv6 routers within the
   autonomous system.

4.  IANA Considerations

   This document directs IANA to record the allocation of the IPv6
   address prefix xxxx/64 as a discard-only prefix in the IPv6 Address
   Space registry.  No end party is to be assigned this prefix.  The
   prefix should be allocated from ::/3.

5.  Security Considerations

   As the prefix specified in this document should not normally be
   transmitted or accepted over inter-domain BGP sessions, it is usually
   appropriate to include this prefix in inter-domain BGP prefix filters

6.  References

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6.1.  Normative References

   [RFC3882]  Turk, D., "Configuring BGP to Block Denial-of-Service
              Attacks", RFC 3882, September 2004.

   [RFC5156]  Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156,
              April 2008.

   [RFC5635]  Kumari, W. and D. McPherson, "Remote Triggered Black Hole
              Filtering with Unicast Reverse Path Forwarding (uRPF)",
              RFC 5635, August 2009.

6.2.  Informative References

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
              Networks", BCP 84, RFC 3704, March 2004.

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849, July 2004.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
              Reserved for Documentation", RFC 5737, January 2010.

Author's Address

   Nick Hilliard
   4027 Kingswood Road
   Dublin  24


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