Network Working Group                                            T. King
Internet-Draft                                                C. Dietzel
Intended status: Standards Track                  DE-CIX Management GmbH
Expires: December 31, 2016                                   J. Snijders
                                                              G. Doering
                                                             SpaceNet AG
                                                              G. Hankins
                                                           June 29, 2016

                BLACKHOLE BGP Community for Blackholing


   This document describes the use of a well-known Border Gateway
   Protocol (BGP) community for blackholing in IP networks.  This well-
   known advisory transitive BGP community, namely BLACKHOLE, allows an
   origin AS to specify that a neighboring network should blackhole a
   specific IP prefix.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   be interpreted as described in [RFC2119] only when they appear in all
   upper case.  They may also appear in lower or mixed case as English
   words, without normative meaning.

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
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   This Internet-Draft will expire on December 31, 2016.

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Copyright Notice

   Copyright (c) 2016 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  BLACKHOLE Attribute . . . . . . . . . . . . . . . . . . . . .   3
   3.  Operational Recommendations . . . . . . . . . . . . . . . . .   3
     3.1.  IP Prefix Announcements with BLACKHOLE Community Attached   3
     3.2.  Local Scope of Blackholes . . . . . . . . . . . . . . . .   3
     3.3.  Accepting Blackholed IP Prefixes  . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Network infrastructures have been increasingly hampered by DDoS
   attacks.  In order to dampen the effects of these DDoS attacks, IP
   networks have offered BGP blackholing to neighboring networks via
   various mechanisms such as described in [RFC3882] and [RFC5635].

   DDoS attacks targeting a certain IP address may cause congestion of
   links used to connect to other networks.  In order to limit the
   impact of such a scenario on legitimate traffic, networks adopted a
   mechanism called BGP blackholing.  A network that wants to trigger
   blackholing needs to understand the triggering mechanism adopted by
   its neighboring networks.  Different networks provide different
   mechanisms to trigger blackholing, including but not limited to pre-
   defined blackhole next-hop IP addresses, specific BGP communities or
   via an out-of-band BGP session with a special BGP speaker.

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   Having several different mechanisms to trigger blackholing in
   different networks makes it an unnecessarily complex, error-prone and
   cumbersome task for network operators.  Therefore a well-known BGP
   community [RFC1997] is defined for operational ease.

   Having such a well-known BGP community for blackholing also supports
   networks because:

   o  implementing and monitoring blackholing becomes easier when
      implementation and operational guides do not cover many options
      that trigger blackholing.
   o  the number of support requests from customers about how to trigger
      blackholing in a particular neighboring network will be reduced as
      the codepoint for common blackholing mechanisms is unified.

   Making it considerably easier for network operators to utilize
   blackholing makes operations easier.

2.  BLACKHOLE Attribute

   This document defines the use of a new well-known BGP transitive
   community, BLACKHOLE.

   The semantics of this attribute allow a network to interpret the
   presence of this community as an advisory qualification to drop any
   traffic being sent towards this prefix.

3.  Operational Recommendations

3.1.  IP Prefix Announcements with BLACKHOLE Community Attached

   When a network is under DDoS duress, it MAY announce an IP prefix
   covering the victim's IP address(es) for the purpose of signaling to
   neighboring networks that any traffic destined for these IP
   address(es) should be discarded.  In such a scenario, the network
   operator SHOULD attach BLACKHOLE BGP community.

3.2.  Local Scope of Blackholes

   A BGP speaker receiving a BGP announcement tagged with the BLACKHOLE
   BGP community SHOULD add a NO_ADVERTISE, NO_EXPORT or similar
   community to prevent propagation of this route outside the local AS.

   Unintentional leaking of more specific IP prefixes to neighboring
   networks can have adverse effects.  Extreme caution should be used
   when purposefully propagating IP prefixes tagged with the BLACKHOLE
   BGP community outside the local routing domain.

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3.3.  Accepting Blackholed IP Prefixes

   It has been observed that announcements of IP prefixes larger than
   /24 for IPv4 and /48 for IPv6 are usually not accepted on the
   Internet (see section 6.1.3 [RFC7454]).  However, blackhole routes
   should be as small as possible in order to limit the impact of
   discarding traffic for adjacent IP space that is not under DDoS
   duress.  Typically, the blackhole route's prefix length is as
   specific as /32 for IPv4 and /128 for IPv6.

   BGP speakers SHOULD only accept and honor BGP announcements carrying
   the BLACKHOLE community if the announced prefix is covered by a
   shorter prefix for which the neighboring network is authorized to

4.  IANA Considerations

   The IANA is requested to register BLACKHOLE as a well-known BGP
   community with global significance:

      BLACKHOLE (= 0xFFFF029A)

   The low-order two octets in decimal are 666, amongst network
   operators a value commonly associated with BGP blackholing.

5.  Security Considerations

   BGP contains no specific mechanism to prevent the unauthorized
   modification of information by the forwarding agent.  This allows
   routing information to be modified, removed, or false information to
   be added by forwarding agents.  Recipients of routing information are
   not able to detect this modification.  Also, RPKI [RFC6810] and
   BGPSec [I-D.ietf-sidr-bgpsec-overview] do not fully resolve this
   situation.  For instance, BGP communities can still be added or
   altered by a forwarding agent even if RPKI and BGPSec are in place.

   The BLACKHOLE BGP community does not alter this situation.

   A new additional attack vector is introduced into BGP by using the
   BLACKHOLE BGP community: denial of service attacks for IP prefixes.

   The unauthorized addition of the BLACKHOLE BGP community to an IP
   prefix by a forwarding agent may cause a denial of service attack
   based on denial of reachability.  The denial of service will happen
   if a network offering blackholing is traversed.  However, denial of
   service attack vectors to BGP are not new as the injection of false
   routing information is already possible.

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   In order to further limit the impact of unauthorized BGP
   announcements carrying the BLACKHOLE BGP community, the receiving BGP
   speaker SHOULD verify by applying strict filtering (see section  [RFC7454]) that the peer announcing the prefix is
   authorized to do so.  If not, the BGP announcement should be filtered

   The presence of this BLACKHOLE BGP community may introduce a resource
   exhaustion attack to BGP speakers.  If a BGP speaker receives many IP
   prefixes containing the BLACKHOLE BGP community, its internal
   resources such as CPU power, memory or FIB capacity might exhaust,
   especially if usual prefix sanity checks (e.g. such as IP prefix
   length or number of prefixes) are disabled (see Section 3.3).

6.  References

6.1.  Normative References

   [RFC1997]  Chandra, R., Traina, P., and T. Li, "BGP Communities
              Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,

6.2.  Informative References

              Lepinski, M. and S. Turner, "An Overview of BGPsec",
              draft-ietf-sidr-bgpsec-overview-08 (work in progress),
              June 2016.

   [RFC3882]  Turk, D., "Configuring BGP to Block Denial-of-Service
              Attacks", RFC 3882, DOI 10.17487/RFC3882, September 2004,

   [RFC5635]  Kumari, W. and D. McPherson, "Remote Triggered Black Hole
              Filtering with Unicast Reverse Path Forwarding (uRPF)",
              RFC 5635, DOI 10.17487/RFC5635, August 2009,

   [RFC6810]  Bush, R. and R. Austein, "The Resource Public Key
              Infrastructure (RPKI) to Router Protocol", RFC 6810, DOI
              10.17487/RFC6810, January 2013,

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   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
              and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
              February 2015, <>.

Appendix A.  Acknowledgements

   The authors would like to gratefully acknowledge many people who have
   contributed discussions and ideas to the making of this proposal.
   They include Petr Jiran, Yordan Kritski, Christian Seitz, Nick
   Hilliard, Joel Jaeggli, Christopher Morrow, Thomas Mangin, Will
   Hargrave and Niels Bakker.

Authors' Addresses

   Thomas King
   DE-CIX Management GmbH
   Lichtstrasse 43i
   Cologne  50825


   Christoph Dietzel
   DE-CIX Management GmbH
   Lichtstrasse 43i
   Cologne  50825


   Job Snijders
   NTT Communications, Inc.
   Theodorus Majofskistraat 100
   Amsterdam  1065 SZ


   Gert Doering
   SpaceNet AG
   Joseph-Dollinger-Bogen 14
   Munich  80807


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   Greg Hankins
   777 E. Middlefield Road
   Mountain View, CA  94043


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