INTERNET DRAFT Joo-Chul Lee
Expires: December 2003 Myung-Ki Shin
ETRI
June 2003
Considerations for Mobility Support in NAT-PT
<draft-lee-v6ops-natpt-mobility-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Abstract
The document specifies considerations for mobility support in NAT-
PT (RFC-2766) [1].
1. Introduction
NAT-PT (RFC-2766) enables end-nodes in IPv6 realm to communicate
with end-nodes in IPv4 realm and vice versa. RFC-2766 [1] needs
some fixes and/or applicability statements. Among them, there
exists considerations in NAT-PT [1] when IPv6 end-nodes move. 3GPP
drafts [2, 3] mention that there is a need for transltors, such as
NAT-PT, but in this case, current RFC-2766 [1] does not support
IPv6 mobile nodes. The document specifies considerations for
mobility support in NAT-PT (RFC-2766)[1].
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2. Issues with mobility support in NAT-PT
2.1 Movement of end-nodes in IPv6 realm (IPv6-MNs)
When IPv6 end-nodes move, there are issues should be considered in
RFC-2766. Basically, since mobile IPv6 (MIPv6) [4] provides route
optimization, NAT-PT box must update its associated address mapping
entries. As well, NAT-PT box needs appropriate handling of controls
such as RR (Return Routability), BU (Binding Update), etc.
+---------+
+------------------------>| IPv4 CN |
| +---------+
V IPv4 domain
+----------+
/--------------| NAT-PT |-----------\
/ +----------+ \
| / | |
| /-----/ | |
| / | |
| : +-------+ |
| : | R1 | |
| / +-------+ |
| +-------+ / \ |
| | HA | / +-------+ |
| +-------+ : | R2 | |
| | : +-------+ |
| | | |
| +-------+ | |
| |IPv6 MN|- - - + ------+---+- |
| +-------+ | | |
| . +-------+ |
| +- - - - -> |IPv6 MN| |
| Movement +-------+ |
\ /
\-------------------------------------/
IPv6 realm
2.2 Movement of end-nodes in IPv4 realm (IPv4-MNs)
Obviously, there is no issue when IPv4 end-nodes move, since mobile
IPv4 (MIPv4) ][5] uses tunneling.
3. Mobility support in NAT-PT box
This section describes the case that an IPv6-MN moves from home
network to other network in the same IPv6 island.
Main consideration is that NAT-PT box does all of MIPv6
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functionalities on behalf of IPv4-CNs. Following subsections show
how NAT-PT box works in this situation.
In the example below, the following notations will be used.
==> means IPv6 packet.
--> means IPv4 packet.
++> means IPv6 over IPv6 tunnel.
3.1 Control Sessions
3.1.1 Initial state
In initial state <IPv6 MN> is in home network and it communicates
with <IPv4 CN> like general NAT-PT outbound session.
<IPv6 MN> <HA> <NAT-PT> <IPv4 CN>
| | | |
|======>|======>| | - <IPv6 MN> sends IPv6 packet [src
| | | | (P1::xxxx/64),dst(PREFIX::a.b.c.d)]
| | | | to <IPv4 CN>.
| | | |
| | |------->| - <NAT-PT> translates IPv6 packet
| | | | into IPv4 packet[src(w.x.y.z),
| | | | dst(a.b.c.d)] and sends it to
| | | | <IPv4 CN>.
| | | |
| | |<-------| - <IPv4 CN> sends IPv4 packet[src
| | | | (a.b.c.d),dst(w.x.y.z)] to
| | | | <NAT-PT>.
| | | |
|<======|<======| | - <NAT-PT> translates IPv4 packet
| | | | into IPv6 packet[src(PREFIX::
| | | | a.b.c.d),dst(P1::xxxx/64)]
* IPv6 MN
P1::xxxx/64 (Home Address)
* HA
advertises P1::/64
* NAT-PT
advertises PREFIX::/64
Mapping Table:
mapping_entry[0] = {P1::xxxx/64, w.x.y.z}
Binding Cache Table:
binding_cache_entry[0] = {}
Kcn/nonce Table:
kcn_entry[0] = {}
* IPv4 CN
a.b.c.d
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3.1.2 RR procedure
After <IPv6 MN>'s moving from home network to other subnet, <IPv6
MN> tries RR procedure to check reachability of <IPv4 CN> before
sending BU.
<IPv6 MN> <HA> <R1> <NAT-PT> <IPv4 CN>
| | | | |
|===========>|======>| | - <IPv6 MN> sends CoTI message
| | | | | to <IPv4 CN>.
| | | | |
|++++++>|===========>| | - <IPv6 MN> sends HoTI message
| | | | | to <IPv4 CN> through HA.
| | | | |
|<===========|<======| | - <NAT-PT> intercepts CoTI
| | | | | message and return CoT message
| | | | | to <IPv6 MN>. Before sending
| | | | | CoT message, <NAT-PT> must
| | | | | save kcn and care-of nonce
| | | | | index for <IPv4 CN>
| | | | |
|<++++++|<===========| | - <NAT-PT> intercepts HoTI
| | | | | message and return HoT message
| | | | | to <IPv6 MN>. Before sending
| | | | | HoT message, <NAT-PT> must
| | | | | save kcn and home nonce index
| | | | | for <IPv4 CN>
* IPv6 MN
P1::xxxx/64 (Home Address)
P2::xxxx/64 (Care of Address)
* HA
advertises P1::/64
* R1
advertises P2::/64
* NAT-PT
advertises PREFIX::/64
Mapping Table:
mapping_entry[0] = { P1::xxxx/64, w.x.y.z }
Binding Cache Table:
binding_cache_entry[0] = {}
Kcn/nonce Table:
kcn_entry[0] = { HA: P1::xxxx/64, COA: P2::xxxx/64,
CN: a.b.c.d, Kcn: nnn,
Home Nonce index: nnn,
Care-of Nonce Index: nnn }
* IPv4 CN
a.b.c.d
3.1.3 Binding Update/Acknowledge
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After finishing RR procedure <IPv6 MN> makes authenticator and
sends BU message to <IPv4 CN> for route optimization.
<IPv6 MN> <HA> <R1> <NAT-PT> <IPv4 CN>
| | | | |
|===========>|======>| | - <IPv6 MN> sends BU message to
| | | | | <IPv4 CN>
| | | | |
|<===========|<======| | - <NAT-PT> interceptes BU
| | | | | message and returns BA to
| | | | | <IPv6 MN>. Before sending BA
| | | | | <NAT-PT> must add new binding
| | | | | cache entry.
* IPv6 MN
P1::xxxx/64 (Home Address)
P2::xxxx/64 (Care of Address)
* HA
advertises P1::/64
* R1
advertises P2::/64
* NAT-PT
advertises PREFIX::/64
Mapping Table:
mapping_entry[0] = { P1::xxxx/64, w.x.y.z }
Binding Cache Table:
binding_cache_entry[0] = { HA: P1::xxxx/64,
COA: P2::xxxx/64,
Lifetime: nnn, Flag: 0,
Seq no: nnn, Usage info: nnn}
Kcn/nonce Table:
kcn_entry[0] = { HA: P1::xxxx/64, COA: P2::xxxx/64,
CN: a.b.c.d, Kcn: nnn,
Home Nonce index: nnn,
Care-of Nonce Index: nnn }
* IPv4 CN
a.b.c.d
3.2 General Data Transimission
<IPv6 MN> <HA> <R1> <NAT-PT> <IPv4 CN>
| | | | |
|===========>|======>| | - <IPv6 MN> sends IPv6 packet
| | | | | with HAO to <IPv4 CN>.
| | | | |
| | | |------->| - <NAT-PT> intercepts IPv6
| | | | | packet with HAO. To translate
| | | | | packet with HAO <NAT-PT>
| | | | | searches connection {src(HA),
| | | | | dst(PREFIX::a.b.c.d)} which
| | | | | has mapping information.
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| | | | |
| | | |<-------| - <IPv4 CN> sends IPv4 packet
| | | | | [src(a.b.c.d), dst(w.x.y.z)]
| | | | | to <NAT-PT>.
| | | | |
|<===========|<======| | - <NAT-PT> translates IPv4
| | | | | packet and forwards it. Before
| | | | | sending translated IPv6 packet
| | | | | <NAT-PT> must check whether
| | | | | there is binding cache entry
| | | | | corresponding to P1::xxxx/64
| | | | | or not.
| | | | | If there is binding cache
| | | | | entry, <NAT-PT> changes
| | | | | destination address into COA
| | | | | (P2::xxxx/64) and adds routing
| | | | | option header including HA
| | | | | (P1::xxxx/64) to basic IPv6
| | | | | header.
* IPv6 MN
P1::xxxx/64 (Home Address)
P2::xxxx/64 (Care of Address)
* HA
advertises P1::/64
* R1
advertises P2::/64
* NAT-PT
advertises PREFIX::/64
Mapping Table:
mapping_entry[0] = { P1::xxxx/64, w.x.y.z }
Binding Cache Table:
binding_cache_entry[0] = { HA: P1::xxxx/64,
COA: P2::xxxx/64,
Lifetime: nnn, Flag: 0,
Seq no: nnn, Usage info: nnn}
Kcn/nonce Table:
kcn_entry[0] = { HA: P1::xxxx/64, COA: P2::xxxx/64,
CN: a.b.c.d, Kcn: nnn,
Home Nonce index: nnn,
Care-of Nonce Index: nnn }
* IPv4 CN
a.b.c.d
4. IPv6-MNs move from one island to another island
This issue should be also considered. This version of the draft is
not mentioned yet.
5. Security Considerations
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Security consideration is not studied yet.
8. Acknowledgments
Authors would like to acknowledge the idea sharing contributions by
Hee Cheol Lee and for detailed comments by KyeongJin Lee on this
document.
References
[1] Tsirtsis, G. and P. Srisuresh, "Network Address Translation -
Protocol Translation (NAT-PT)", RFC 2766, February 2000.
[2] J. Soininen (ed.), "Transition Scenarios for 3GPP Networks",
draft-ietf-v6ops-3gpp-cases-03, March 2003 (Work-in-Progress).
[3] J. Wiljakka (ed.), "Analysis on IPv6 Transition in 3GPP Networks",
draft-ietf-v6ops-3gpp-analysis-03, March 2003 (Work-in-Progress).
[4] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in IPv6",
draft-ietf-mobileip-ipv6-21, February 2003 (Work-in-Progress).
[5] C. Perkins, Ed., "IP Mobility Support for IPv4", RFC 3344, August
2002
Authors' Addresses
Joo-Chul Lee
ETRI PEC
161 Kajong-Dong, Yusong-Gu, Taejon 305-350, Korea
Tel : +82 42 860 1080
Fax : +82 42 861 5404
E-mail : rune@etri.re.kr
Myung-Ki Shin
ETRI PEC
161 Kajong-Dong, Yusong-Gu, Taejon 305-350, Korea
Tel : +82 42 860 4847
Fax : +82 42 861 5404
E-mail : mkshin@pec.etri.re.kr
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