A Discard Prefix for IPv6
draft-ietf-v6ops-ipv6-discard-prefix-00

Abstract

Remote triggered black hole filtering describes a method of mitigating against denial-of-service attacks by selectively discarding traffic based on source or destination address. This document explains why a unique IPv6 prefix should be formally assigned by IANA for the purpose of facilitating IPv6 remote triggered black hole filtering.

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 http://datatracker.ietf.org/drafts/current/.

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This Internet-Draft will expire on April 12, 2012.

Copyright Notice

Copyright (c) 2011 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 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
• 1.1. Conventions
• 2. A Discard Prefix for IPv6
• 3. Operational Implications
• 4. IANA Considerations
• 5. Security Considerations
• 6. References
• 6.1. Normative References
• 6.2. Informative References
• Author's Address

1. Introduction

Remote triggered black hole (RTBH) filtering describes a class of methods of blocking IP traffic to or from a specific destination on a network. 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 or null interface. Typically, this information is propagated throughout an autonomous system using a dynamic routing protocol. By deploying RTBH systems across a network, traffic to or from specific destinations may be selectively black-holed 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 [RFC5737].

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 creating an assigned discard prefix for IPv6, the IETF will introduce operational clarity and good practice for implementation of IPv6 RTBH configurations.

1.1. Conventions

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].

2. A Discard Prefix for IPv6

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

As [RFC5635] describes situations where more than one discard address may be used for implementing multiple remote triggered black holes, a single assigned prefix is not sufficient to cover all likely RTBH filtering 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 third party autonomous systems and IPv6 traffic with an destination address within this prefix SHOULD NOT be forwarded to 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 appropriate to label the prefix as a Martian ([RFC3704]) for inclusion in inter-domain BGP prefix filters.

6. References

6.1. Normative References

6.2. Informative References

Author's Address