Network Working Group T. King
Internet-Draft C. Dietzel
Intended status: Standards Track DE-CIX Management GmbH
Expires: December 31, 2016 J. Snijders
NTT
G. Doering
SpaceNet AG
G. Hankins
Nokia
June 29, 2016
BLACKHOLE BGP Community for Blackholing
draft-ietf-grow-blackholing-01
Abstract
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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
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
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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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 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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
advertise.
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
6.2.1.1.2. [RFC7454]) that the peer announcing the prefix is
authorized to do so. If not, the BGP announcement should be filtered
out.
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,
<http://www.rfc-editor.org/info/rfc1997>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
6.2. Informative References
[I-D.ietf-sidr-bgpsec-overview]
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,
<http://www.rfc-editor.org/info/rfc3882>.
[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,
<http://www.rfc-editor.org/info/rfc5635>.
[RFC6810] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol", RFC 6810, DOI
10.17487/RFC6810, January 2013,
<http://www.rfc-editor.org/info/rfc6810>.
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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, <http://www.rfc-editor.org/info/rfc7454>.
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
Germany
Email: thomas.king@de-cix.net
Christoph Dietzel
DE-CIX Management GmbH
Lichtstrasse 43i
Cologne 50825
Germany
Email: christoph.dietzel@de-cix.net
Job Snijders
NTT Communications, Inc.
Theodorus Majofskistraat 100
Amsterdam 1065 SZ
NL
Email: job@ntt.net
Gert Doering
SpaceNet AG
Joseph-Dollinger-Bogen 14
Munich 80807
Germany
Email: gert@space.net
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Greg Hankins
Nokia
777 E. Middlefield Road
Mountain View, CA 94043
USA
Email: greg.hankins@nokia.com
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