wdiff draft-ietf-v6ops-ivi-icmp-address-00.txt draft-ietf-v6ops-ivi-icmp-address-01.txt

Network Working Group X. Li
Internet-Draft C. Bao
Intended status: BCP CERNET Center/Tsinghua
Expires: May 17, August 28, 2012 University
D. Wing
R. Vaithianathan
Cisco
G. Huston
APNIC
November 14, 2011
February 25, 2012

Stateless Source Address Mapping for ICMPv6 Packets
draft-ietf-v6ops-ivi-icmp-address-00
draft-ietf-v6ops-ivi-icmp-address-01

Abstract

A stateless IPv4/IPv6 translator may receive ICMPv6 packets
containing non IPv4-translatable addresses as the source that should
be passed across the translator as an ICMP packet directed to the the
IPv4-translatable destination. This document discusses the
considerations and the presents a stateless address mapping algorithms algorithm for
source address translation in ICMPv6 headers for such cases.

Status of this Memo

This Internet-Draft is submitted to IETF 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 May 17, August 28, 2012.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement and Considerations . . . . . . . . . . . . . 3
4. Routing Considerations . . . . . . . . . . . . . . . . . . . . 4
5. Possible Stateless Address Mapping Algorithms Algorithm . . . . . . . . . . . . . . 4
6. Security Considerations ICMP Extension . . . . . . . . . . . . . . . . . . . . . . . . 5
7. IANA Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7.1. Filtering Recommendations . . . . . . . . . . . . . . . . . 5
7.2. Rate-limiting Recommendations . . . . . . . . . . . . . . . 5
7.3. RFC5837 Recommendations . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
9.
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1.
10.1. Normative References . . . . . . . . . . . . . . . . . . . 6
9.2.
10.2. Informative References . . . . . . . . . . . . . . . . . . 6 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 7

1. Introduction

The IP/ICMP translation document of IPv4/IPv6 translation [RFC6145]
states that "the IPv6 addresses in the ICMPv6 header may not be IPv4-
translatable addresses and there will be no corresponding IPv4
addresses represented of this IPv6 address. In this case, the
translator can do stateful translation. A mechanism by which the
translator can instead do stateless translation is left for future
work." This document defines such a stateless translation mechanism.

2. Notational Conventions

The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC2119].

3. Problem Statement and Considerations

When a stateless IPv4/IPv6 translator receives an ICMPv6 message (for
example "Packet Too Big") sourced from an non-IPv4-translatable IPv6
address, directed to an IPv4-translatable IPv6 address, it needs to
generate an ICMP message. For the reasons discussed below, choosing
the source IPv4 address of this ICMP message is problematic.

The address used should not cause the ICMP packet to be a candidate
for discarding, particularly in the contest of uRPF filters
[RFC3704]. This consideration precludes the use of private IPv4
address space [RFC1918] in this context.

It is also a consideration that the IPv4/IPv6 translation is intended
for use in contexts where IPv4 addresses may not be readily
available, so it is not considered to be appropriate to use IPv4-
translatable IPv6 addresses for all internal points in the IPv6
network that may originate ICMPv6 messages.

It is also an objective that it is possible for the IPv4 recipient of
the ICMP message be able to distinguish between different IPv6 ICMPv6
originations (for example, to support a traceroute diagnostic utility
that provides some limited network level visibility across the IPv4/
IPv6 translator). This implies that a IPv4/IPv6 translator needs to
have a pool of IPv4 addresses to be used for mapping the source
address of ICMPv6 packets generated from different originations.

These addresses are for use in the source address of ICMP packets,
and therefore are not intended to be used as a destination address
for any packet. It is therefore possible to use a common address
pool for the IPv4/IPv6 translation protocol, and, considering an
objective of constraining the use of these IPv4 addresses in this
application, it is feasible to use a common address pool for mapping
the source addresses of non-translatable ICMPv6 packets as a part of
the protocol specification.

These considerations leads to the recommendation of drawing an IPv4
/24 prefix from the IANA Special Purpose Address Registry as a "Well-
Known Prefix" for use by IPv4/IPv6 translators for the purpose of
mapping otherwise untranslatable IPv6 source addresses of ICMPv6
messages to IPv4 ICMP messages.

The ICMP extension defined by [RFC5837] provides a mechanism to
process the ICMPv4 messages that contain IP Address Sub-Objects that
specify IPv6 addresses. However, an enhanced traceroute application
must be used, which has not yet been widely available. In this
document, a combined approach is proposed, i.e. non IPv4-translatable
address is mapped to IANA-assigned /24, and the resulting ICMP is
extended according to [RFC5837]. Therefore, ordinary ICMP processing
tools (traceroute) can be utilized in normal cases and when DDoS
happens, enhanced ICMP process tools can be utilized to identify the
real source.

4. Routing Considerations

Addresses from the assigned address prefix are intended to be used as
source addresses and not as destination addresses in the context of
the public network. As packets passing through the public network
need to pass through conventional packet filters, including uRPF
filters [RFC3704], this implies that the assigned address may be used
in routing advertisements. Such routing advertisements are non-
exclusive and should be accepted from any originating AS in an
anycast fashion.

5. Possible Stateless Address Mapping Algorithms Algorithm

When an IPv4 /24 prefix is allocated to represent the source address
of ICMP, the Last Octet can be generated using one of the following
algorithms.

o The translator can randomly generates the Last Octet of the /24
prefix for different non IPv4-translatable addresses. However, in
this case the translator may need to maintain states to ensure
same non IPv4-translatable IPv6 address maps to same IPv4 address.

o The translator can MUST copy the "Hop Count" in the IPv6 header
of the ICMPv6 to the Last Octet. Routers typically When routers emit ICMPv6 packets
with the same hop count, thus as the ICMPv6 packet is routed through the
network its hop count is decreased. However, if the routers emit
ICMPv6 packets with different hop counts, it may give the appearance
of a routing loop to tools such as traceroute. That minor side-effect side-
effect in that particular case cannot be avoided while still being
stateless.

o Hashing of the IPv6 address to generate a 8 bit value which will
be used

6. ICMP Extension

When translator is configured to generate use the last octet. In this case, there is no
need IANA-assigned /24 to maintain expensive states, except hashing table which
should be simple with minimal memory usage and consume minimal CPU
cycles. If map non
IPv4-translatable address, the hashing function is good and there are limited
number of IPv6 routers (< 256) on translator MUST implement ICMP
extension defined by [RFC5837]. The resulting ICMP extension MUST
include the IPv6 side of IP address Sub-Objects that specify the network, we
will get unique IPv4 source IPv6
addresses to map in the addresses of original ICMPv6. Therefore, an enhanced traceroute
application can get the real IPv6
routers with O(1) lookup.

The selection of source addresses which generate the algorithm SHOULD
ICMPv6 messages, be a configuration function in
the IPv4/IPv6 translator.

6. able to traceback to their origins and take
filtering/rate-limiting actions if necessary.

7. Security Considerations

The use of an address for source addresses in ICMP packets is
considered "safe" in so far as ICMP packets are not intended to
generate responses directed to the source address.

However it is possible to use this address as a means of gaining
anonymity when launching a denial of service attacks by using this
address as the source address for other forms of malicious traffic.
Packet firewall filters should be configured to treat addresses in
the IANA-assigned /24 network as martian addresses by discarding all
non-ICMP packets that use the IANA-assigned /24 network as a source
address, and all packets that use the IANA-assigned /24 network as a
destination address.

7.1. Filtering Recommendations

o SHOULD allow ICMP type 3 - Destination Unreachable (inc PTB).

o SHOULD allow ICMP type 11 - Time Exceeded.

o MAY allow ICMP type 12 - Parameter Problem.

o SHOULD NOT allow any of the various ICMP request messages.

7.2. Rate-limiting Recommendations

The rate limiting of traffic from the prefix SHOULD also be enabled
as additional countermeasure against abuse of this prefix. The
methods presented in [RFC4443] [RFC5597] [RFC6192] [RFC6398]
[RFC6450] can be used.

7.3. RFC5837 Recommendations

Advanced filtering and rate-limiting techniques which can process the
ICMP extension defined in [RFC5837] MAY also be used to control the
source of the ICMP.

8. IANA Considerations

IANA is requested to make a permanent assignment of a /24 from the
IPv4 Special Purpose Address Registry [RFC5736]. The assigned
address is to be used in the context of generating an IPv4 source
address for mapped ICMPv6 packets being passed through a stateless
IPv4/IPv6 translator. The assignment is under the category of a
specialized use of a designated address block in an anycast context
associated with an Internet Standards Track protocol.

The IANA IPv4 Special Purpose Address Registry records are:

o Prefix 192.70.192.0/24

o Description: To be used in the context of generating an IPv4
source address for mapped ICMPv6 packets being passed through a
stateless IPv4/IPv6 translator.

o Begin: 2011-06-01

o End: Never

o Purpose: Stateless ICMPv6/ICMP translation

o Contact: See RFC

o Scope: Addresses from the assigned address prefix are intended to
be used as source addresses and not as destination addresses in
the context of the public network.

o RFC: This draft.

9. Acknowledgments

The authors would like to acknowledge the following contributors of
this document: Kevin Yin, Chris Metz and Neeraj Gupta.

10. References

9.1.

10.1. Normative 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.

[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.

[RFC5597] Denis-Courmont, R., "Network Address Translation (NAT)
Behavioral Requirements for the Datagram Congestion
Control Protocol", BCP 150, RFC 5597, September 2009.

[RFC5837] Atlas, A., Bonica, R., Pignataro, C., Shen, N., and JR.
Rivers, "Extending ICMP for Interface and Next-Hop
Identification", RFC 5837, April 2010.

[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, April 2011.

9.2.

[RFC6398] Le Faucheur, F., "IP Router Alert Considerations and
Usage", BCP 168, RFC 6398, October 2011.

[RFC6450] Venaas, S., "Multicast Ping Protocol", RFC 6450,
December 2011.

10.2. Informative References

[RFC5736] Huston, G., Cotton, M., and L. Vegoda, "IANA IPv4 Special
Purpose Address Registry", RFC 5736, January 2010.

[RFC6192] Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
Router Control Plane", RFC 6192, March 2011.

Authors' Addresses

Xing Li
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN

Phone: +86 10-62785983
Email: xing@cernet.edu.cn

Congxiao Bao
CERNET Center/Tsinghua University
Room 225, Main Building, Tsinghua University
Beijing 100084
CN

Phone: +86 10-62785983
Email: congxiao@cernet.edu.cn

Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134
USA

Email: dwing@cisco.com

Ramji Vaithianathan
Cisco Systems, Inc.
A 5-2, BGL 12-4, SEZ Unit,
Cessna Business Park, Varthur Hobli
Sarjapur Outer Ring Road
BANGALORE KARNATAKA 560 103
INDIA

Phone: +91 80 4426 0895
Email: rvaithia@cisco.com

Geoff Huston
APNIC

Email: gih@apnic.net