One document matched: draft-kato-behave-prefix-nat-01.txt
Differences from draft-kato-behave-prefix-nat-00.txt
Behave Working Group J. Kato
Internet-Draft A. Matsumoto
Intended status: Standards Track T. Fujisaki
Expires: September 6, 2010 NTT
March 5, 2010
Checksum-Neutral Prefix NAT for IPv6
draft-kato-behave-prefix-nat-01.txt
Abstract
This document describes a use-case of IPv6-to-IPv6 network address
translation, and a translation mechanism for smaller network. To be
used typically in a network where IPv6 /64 prefix is advertiesed, a
network address translation mechanism is proposed that is based on
Interface Identifier rewriting to be checksum neutral.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright Notice
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document authors. All rights reserved.
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Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Proposal of Address Translation using Interface Identifier . . 4
2.1. Address Translation Example . . . . . . . . . . . . . . . . 4
3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
The IPv6-to-IPv6 translation mechanism proposed in NAT66 document.
NAT66 document [I-D.mrw-behave-nat66]. This assumes that a network
is assigned /48 or larger address block. This is because the
mechanism uses 16 bits of IPv6 address for subnetting to make the
translation neutral to address translation.
However, in some environment, a network cannot get such a large
address space. Then, we propose another IPv6-to-IPv6 translation
mechanism that can be used in a network with /48 or smaller address
block and that is neutral to transport layer checksum. This
mechanism also has a characteristics of one-to-one mapping, to keep
the end-to-end transparency as much as possible.
2. Proposal of Address Translation using Interface Identifier
A IPv6 address translation mechanism for smaller network is proposed
in this section. This translation mechiansm is one-to-one mapping
based, and is Interface Identifier rewriting based, to make it
checksum neutral.
Regarding the prefix part of an IPv6 address, it is simply replaced
with the predefined external/internal prefix value. Regarding the
Interface Identifier part, the modified value is chosen so that the
address translation does not have an impact on transport layer
checksum, which is almost the same technique adopted in NAT66
[I-D.mrw-behave-nat66].
2.1. Address Translation Example
Example network structure is described below.
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external network: 2001:0DB8:1111:0001::/64
------+----------------------
|
|
o eth0 2001:0DB8:1111:0001::1
+----+-----+
| NAT66BOX |
+----+-----+
o eth1 FD00:0203:1111:0405::1
|
|
---+--+----------------------
| internal network: FD00:0203:1111:0405::/64
|
|
o eth0 FD00:0203:1111:0405:0200:1111:1011:1234
+-----+-----+
| IPv6 host |
+-----+-----+
example network
When IPv6 host sends a packet destined to external network, NAT66BOX
receives the following IPv6 packet.
dst IPv6 address: (somewhere in external network)
src IPv6 address: fd00:0203:1111:0405:0200:1111:1011:1234
NAT66BOX performs the following address translation to the source
address of the IPv6 packet, and forward the packet to the upstream.
Here, it is assumed that the function cksum(x) calculates the 16-bit
one's complement sum as defined in RFC1071 [RFC1071].
1. Calculates the difference between to-be-translated prefix
checksum and translated prefix checksum.
cksum(FD01:0203:1111:0405) => 0x141B
cksum(2001:0DB8:1111:0001) => 0x3ECB
2. Gets the difference of the two prefixes based on one's
complement sum.
0x3ECB - 0x141B = 0x2AB0
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3. Gets the difference of the least significant 16 bits of the
to-be-translated IPv6 address and the difference of the prefixes'
checksums calculated at 2.
0x1234 - 0x2AB0 = 0xE783
4. Puts the value of 3 to the least significant 16 bits of the
translated address Interface Identifier, and gets the translated
address.
2001:0DB8:1111:0001:0200:1111:1011:E783
In the same way, translation of incoming packet from external network
can be processed.
3. Discussion
The mechanism describes here ignores the meaning U/L bit described in
[RFC4291]. As the Interface Identifier part of the translated
address is not assured of uniqueness, the U/L bit should not be set
to 1.
The workarounds for this issue are to have per-session translation
table, to administrate the addresses of hosts in local network and
make all of them use addresses with U/L bit 0.
4. IANA Considerations
This document has no actions for IANA.
5. Security Considerations
TBD
6. References
6.1. Normative References
[I-D.mrw-behave-nat66]
Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Address
Translation (NAT66)", draft-mrw-behave-nat66-02 (work in
progress), March 2009.
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[RFC1071] Braden, R., Borman, D., Partridge, C., and W. Plummer,
"Computing the Internet checksum", RFC 1071,
September 1988.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
6.2. Informative References
Authors' Addresses
Jun-ya Kato
NTT PF Lab
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81 422 59 2939
Email: kato@nttv6.net
Arifumi Matsumoto
NTT PF Lab
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81 422 59 3334
Email: arifumi@nttv6.net
Tomohiro Fujisaki
NTT PF Lab
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
Phone: +81 422 59 7351
Email: fujisaki@syce.net
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