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Freedman 5 Expires: December 11, 2012 Claranet 6 June 9, 2012 8 A Discard Prefix for IPv6 9 draft-ietf-v6ops-ipv6-discard-prefix-05 11 Abstract 13 Remote triggered black hole filtering describes a method of 14 mitigating the effects of denial-of-service attacks by selectively 15 discarding traffic based on source or destination address. Remote 16 triggered black hole routing describes a method of selectively re- 17 routing traffic into a sinkhole router (for further analysis) based 18 on destination address. This document updates the IPv6 Special 19 Purpose Address Registry by explaining why a unique IPv6 prefix 20 should be formally assigned by IANA for the purpose of facilitating 21 IPv6 remote triggered black hole filtering and routing. 23 Status of this Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on December 11, 2012. 40 Copyright Notice 42 Copyright (c) 2012 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 3 59 2. A Discard Prefix for IPv6 . . . . . . . . . . . . . . . . . . . 3 60 3. Operational Implications . . . . . . . . . . . . . . . . . . . 4 61 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 62 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 63 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 64 6.1. Normative References . . . . . . . . . . . . . . . . . . . 5 65 6.2. Informative References . . . . . . . . . . . . . . . . . . 5 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 68 1. Introduction 70 Remote triggered black hole (RTBH) filtering describes a class of 71 methods of blocking IP traffic either from a specific source 72 ([RFC5635]) or to a specific destination ([RFC3882]) on a network. 73 RTBH routing describes a class of methods of re-routing IP traffic 74 destined to the attacked/targeted host to a special path (tunnel) 75 where a sniffer could capture the traffic for analysis. Both these 76 methods operate by setting the next-hop address of an IP packet with 77 a specified source or destination address to be a unicast prefix 78 which is connected locally or remotely to a router's discard, null or 79 tunnel interface. Typically, reachability information for this 80 prefix is propagated throughout an autonomous system using a dynamic 81 routing protocol such as BGP ([RFC3882]). By deploying RTBH systems 82 across a network, traffic to or from specific destinations may be 83 selectively black-holed or re-routed to a sinkhole device in a manner 84 which is efficient, scalable and straightforward to implement. 86 On some networks, operators configure RTBH installations using 87 [RFC1918] address space or the address blocks reserved for 88 documentation in [RFC5737]. This approach is inadequate because RTBH 89 configurations are not documentation, but rather operationally 90 important features of many public-facing production networks. 91 Furthermore, [RFC3849] specifies that the IPv6 documentation prefix 92 should be filtered in both local and public contexts. On this basis, 93 it is suggested that both private network address blocks and the 94 documentation prefixes described in [RFC5737] are inappropriate for 95 RTBH configurations, and that a dedicated IPv6 prefix should be 96 assigned instead. 98 This document updates the IPv6 Special Purpose Address Registry 99 [IANA-IPV6REG]. 101 1.1. Notational Conventions 103 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 104 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 105 document are to be interpreted as described in [RFC2119]. 107 2. A Discard Prefix for IPv6 109 For the purposes of implementing an IPv6 remote triggered black hole 110 configuration, a unicast address block is required. There are 111 currently no IPv6 unicast address blocks which are specifically 112 nominated for the purposes of implementing such RTBH systems. 114 While it could be argued that there are other addresses and address 115 prefixes which could be used for this purpose (e.g. documentation 116 prefixes, private address space), or that an operator could assign an 117 address block from their own address space for this purposes, there 118 is currently no operational clarity on what address block would be 119 appropriate or inappropriate to use for this purpose. By assigning a 120 globally unique discard prefix for IPv6, the IETF will introduce good 121 practice for the implementation of IPv6 RTBH configurations and will 122 facilitate operational clarity by allowing operators to implement 123 consistent and deterministic inter-domain prefix and traffic 124 filtering policies for black-holed traffic. 126 As [RFC3882] and [RFC5635] describe situations where more than one 127 discard address may be used for implementing multiple remote 128 triggered black hole scenarios, a single address is not sufficient to 129 cover all likely RTBH situations. Consequently, an address block is 130 required. 132 3. Operational Implications 134 This assignment MAY be carried in a dynamic routing protocol within 135 an autonomous system. The assignment SHOULD NOT be announced to or 136 accepted from third party autonomous systems and IPv6 traffic with a 137 destination address within this prefix SHOULD NOT be forwarded to or 138 accepted from third party autonomous systems. If the prefix or a 139 subnet of the prefix is inadvertently announced to or accepted from a 140 third party autonomous system, this may cause excessive volumes of 141 traffic to pass unintentionally between the the two networks, which 142 would aggravate the effect of a denial-of-service attack. 144 On networks which implement IPv6 remote triggered black holes, some 145 or all of this network block MAY be configured with a next-hop 146 destination of a discard or null interface on any or all IPv6 routers 147 within the autonomous system. 149 4. IANA Considerations 151 This document directs IANA to record the allocation of the IPv6 152 address prefix xxxx/64 as a discard-only prefix in the IPv6 Address 153 Space registry and to add the prefix to the IPv6 Special Purpose 154 Address Registry [IANA-IPV6REG]. No end party is to be assigned this 155 prefix. The prefix should be allocated from ::/3. 157 5. Security Considerations 159 As the prefix specified in this document ought not normally be 160 transmitted or accepted over inter-domain BGP sessions for the 161 reasons described in Section 3, it is usually appropriate to include 162 this prefix in inter-domain BGP prefix filters [RFC3704] or otherwise 163 ensure the prefix is neither transmitted to or accepted from a third 164 party autonomous system. 166 6. References 168 6.1. Normative References 170 [IANA-IPV6REG] 171 Internet Assigned Numbers Authority, "IPv6 Special Purpose 172 Address Registry", 2012, . 175 [RFC3882] Turk, D., "Configuring BGP to Block Denial-of-Service 176 Attacks", RFC 3882, September 2004. 178 [RFC5635] Kumari, W. and D. McPherson, "Remote Triggered Black Hole 179 Filtering with Unicast Reverse Path Forwarding (uRPF)", 180 RFC 5635, August 2009. 182 6.2. Informative References 184 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 185 E. Lear, "Address Allocation for Private Internets", 186 BCP 5, RFC 1918, February 1996. 188 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 189 Requirement Levels", BCP 14, RFC 2119, March 1997. 191 [RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed 192 Networks", BCP 84, RFC 3704, March 2004. 194 [RFC3849] Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix 195 Reserved for Documentation", RFC 3849, July 2004. 197 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 198 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 199 May 2008. 201 [RFC5737] Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks 202 Reserved for Documentation", RFC 5737, January 2010. 204 Authors' Addresses 206 Nick Hilliard 207 INEX 208 4027 Kingswood Road 209 Dublin 24 210 IE 212 Email: nick@inex.ie 214 David Freedman 215 Claranet 216 21 Southampton Row, Holborn 217 London WC1B 5HA 218 UK 220 Email: david.freedman@uk.clara.net