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Versions: 00                                                            
Network Working Group                                      M. Richardson
Internet-Draft                                                       SSW
Expires: August 17, 2003                               February 16, 2003


         A method for configuration of IPsec clients using DHCP
              draft-richardson-ipsec-dhcp-over-ike-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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

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   This Internet-Draft will expire on August 17, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.


















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Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   2. Time sequence diagram  . . . . . . . . . . . . . . . . . . . . . 5
   3. Comparisons with mode-cfg  . . . . . . . . . . . . . . . . . . . 6
   4. Comparisons with DHCP-over-IPsec . . . . . . . . . . . . . . . . 7
      References . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
      Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
      Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 9










































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Abstract

   IPsec technology is frequently used for remote access scenarios.  A
   tunnel is established from a mobile node (such as a laptop) and an
   IPsec gateway located at the Enterprise.  The mobile node's tunnel
   outer address is potentially any IP address on the Internet.  The
   mobile node's tunnel inner address should be an address from within
   the enterprise.  The assignment of this address should ideally be
   done dynamically.

   This document specifies a configuration mode called "DHCP over IKE".
   The document specifies that the payload of a DHCP exchange should be
   carried over an IKE phase 1 exchange.






































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1. Introduction

   Intro about problem space for configuring clients with addresses.  We
   use [1] to with [2].















































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2. Time sequence diagram

   The setup consists of:

   +--------+                 +---------+         +--------+
   | client |=================| Security|---------|  DHCP  |
   +--------+                 | gateway |         | server |
                              +---------+         +--------+

     HDR, SAi1, KEi, Ni  -->
     <--    HDR, SAr1, KEr, Nr, [CERTREQ]

   HDR, SK {IDi, [CERT,] [CERTREQ,] [IDr,]
    AUTH, DHCP(disc)} -->

                                       ---DHCP Discovery->
                                       <--DHCP Offer------

     <--    HDR, SK {IDr, [CERT,] AUTH, DHCP(offer))}

     HDR, SK{SAi2, TSi, TSr, DHCP(request)}-->
                                       ---DHCP request-->
                                       <--DHCP ACK-------

     <--    HDR, SK {SAr2, TSi, TSr, DHCP(ack)}

   later, upon rekey, one does:

     HDR, SK {SAi2, TSi, TSr, DHCP(request)}-->
                                       ---DHCP request-->
                                       <--DHCP ACK-------

     <--    HDR, SK {SAr2, TSi, TSr, DHCP(ack)}


















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3. Comparisons with mode-cfg

   From the point of view of the IKE implementor, this proposal is very
   similar to mode configuration.  There are two major differences:
   inclusion of a DHCP client state machine into the client IKE, and the
   IKEv2 gateway must encapsulate the DHCP payloads into a UDP packet
   and relay them to a DHCP server.  The gateway SHOULD also append DHCP
   relay options to the end to signal to the DHCP server that it came
   via IKEv2.

   The major advantage of DHCP-over-IKE vs mode-cfg is that it leverages
   all of the DHCP protocol infrastructure for configuration of the end
   host.  Further, it naturally interacts with the DHCP infrastructure
   at the enterprise end.





































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4. Comparisons with DHCP-over-IPsec

   The DHCP-over-IKE situation appears more complicated due to the
   inclusion of the DHCP state machines into IKEv2.  The major
   complexity appears to be on the client.  Note that this is an
   illusion - in the DHCP-over-IPsec, the IKE on the client needs to
   know what state the DHCP client it is so that it may act accordingly.
   As such, the states are simply represented twice.  Unless the
   implementor is able to take advantage of an existing DHCP client
   present on the OS, there is little savings in actual code.

   DHCP-over-IPsec requires that a very strange IPsec SA be configured
   for: 0.0.0.0/0:udp/67 <->0.0.0.0/0:udp/68.  Note that extreme care
   must be taken to make sure that this does not also catch packets
   destined to the DHCP server on the physical wire.  This SA MUST be be
   torn down before any traffic is mis-directed on it.  Further, it is
   very difficult to configure a mobile system that must maintain
   tunnels to two enterprises.

































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References

   [1]  Droms, R., "Dynamic Host Configuration Protocol", RFC 1531,
        October 1993.

   [2]  Maughan, D., Schneider, M. and M. Schertler, "Internet Security
        Association and Key Management Protocol (ISAKMP)", RFC 2408,
        November 1998.


Author's Address

   Michael C. Richardson
   Sandelman Software Works
   470 Dawson Avenue
   Ottawa, ON  K1Z 5V7
   CA

   EMail: mcr@sandelman.ottawa.on.ca
   URI:   http://www.sandelman.ottawa.on.ca/































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Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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