Network Working Group S. Daniel Park
Internet Draft P. Kim
Expires : August 2004 Samsung Electronics
February 2004
DHCP Option for Configuring IPv6-in-IPv4 Tunnels
<draft-daniel-dhc-ipv6in4-opt-01.txt>
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document provides a mechanism by which the DHCPv4 servers can
provide information about the configured IPv6-in-IPv4 tunnel
end-points. The IPv4/IPv6 dual-stack nodes can use this
information to set up a configured tunnel to the tunnel end-point
to obtain IPv6 connectivity.
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Table of Contents
1. Introduction.................................................3
2. Requirements.................................................3
3. Configured Tunnel End Point Option...........................4
4. Multiple Tunnel End Point Considerations.....................5
5. Security Considerations......................................5
6. IANA Considerations..........................................6
7. References...................................................6
7.1 Normative References....................................6
7.2 Informative Reference...................................6
8. Authors' Addresses...........................................7
9. Acknowledgements.............................................7
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1. Introduction
In the initial deployment of IPv6, the IPv6 nodes may need to
communicate with the other IPv6 nodes via IPv4 tunnel service. The
connectivity can be obtained by setting up an IPv6-in-IPv4
configured tunnel between a client and a tunnel router.
This document defines a new option by which the DHCPv4 [1] server
can notify the client with the list of end-points of the possible
configured tunnels.
2. Requirements
The keywords 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 RFC 2119 [2].
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3. Configured Tunnel End Point Option
This option specifies the configured tunnel end-points that client
should use when discovering the IPv4 address of the ISP's tunnel
router somehow via the Dynamic Host Configuration Protocol.
Once the IPv4 address has been learned, it is configured as the
tunnel end-point for the configured IPv6-over-IPv4 tunnel.
The format of the Configured Tunnel End Point Option is shown as
below;
The code for this option is TBD. The minimum length of this option
is 4, and the length MUST be a multiple of 4.
Code Length CTEP Order in Sequence
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_CTEP | Len | CTEP Addr1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CTEP Addr 1 | Subnet Mask 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subnet Mask 1 | CTEP Addr 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CTEP Addr 2 | Subnet Mask 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subnet Mask 2 |. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the above diagram, CTEP Addr and Subnet Mask are 32-bit integers
corresponding to DHCP options which specify the IP addresses of
different configured tunnel end-points.
As described in [4], the dual node received CTEP option MUST store
the tunnel end-point addresses and these addresses are used as
destination address for the encapsulating IPv4 header.
The determination of which packets to tunnel is usually made by
routing information on the encapsulator. This is usually done via a
routing table, which directs packets based on their destination
address using the prefix mask and match technique. For more
information, refer to section 4. Configured Tunneling in [4].
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4. Multiple Tunnel End Point Considerations
For the simple configured tunnel, one tunnel end-point is generally
used and it assumes that all the networks will be reached through
the same end-point. In this case, one CTEP Addr field in the CTEP
option without Subnet Mask field is used for configured tunnel
service.
The list of end-points can be installed as the default routes and
the routes will be tried in a round robin fashion if the IPv6 host
load-sharing is honored [5]. Instead there can be specific default
routes for the different destination.
Generally, there may not be a need for installing multiple
configured tunnel end-points unless administrator wants two for
redundancy purposes. It is out of scope of this draft.
5. Security Considerations
A rouge DHCP server can issue invalid or incorrect configured tunnel
end-points. This may cause denial of service due to unreachability
or makes the client to reach incorrect destination.
The latter has very severe security issues as the tunnel end-point
is on-the-path towards all the IPv6 destinations, and can trivially
act as a man-in-the-middle attacker.
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6. IANA Considerations
IANA is requested to an assign value for the Configured Tunnel End
Point option code in accordance with RFC 2939 [3].
Option Name Value Described in
OPTION_CTEP TBD Section 3.
7. References
7.1 Normative References
[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
Bucknell University, March 1997.
[2] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[3] Droms, R.,"Procedures and IANA Guidelines for Definition of
New DHCP Options and Message Types", RFC 2939, September 2000.
7.2 Informative Reference
[4] Nordmark, E. and Gilligan, R.E., "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 2893, August 2000.
[5] Hinden B. and Thaler D., "IPv6 Host to Router Load Sharing",
Internet-Draft (work in progress), January 2004.
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8. Authors' Addresses
Soohong Daniel Park
Mobile Platform Laboratory, Samsung Electronics.
416. Maetan-Dong, Yeongtong-Gu, Suwon
Korea
Phone: +81 31 200 4508
Email: soohong.park@samsung.com
Pyungsoo Kim
Mobile Platform Laboratory, Samsung Electronics.
416. Maetan-Dong, Yeongtong-Gu, Suwon
Korea
Phone: +81 31 200 4635
Email: kimps@samsung.com
9. Acknowledgements
Special thanks to Pekka Savola and Vijayabhaskar A K for their many
valuable revisions and comments. In particular, Pekka Savola kindly
clarified the multiple tunnel end point considerations with his good
experience as well.
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