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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 4702

DHC Working Group                                               M. Stapp
Internet-Draft                                                Y. Rekhter
Expires: January 12, 2001                            Cisco Systems, Inc.
                                                           July 14, 2000


                      The DHCP Client FQDN Option
                  <draft-ietf-dhc-fqdn-option-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
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on January 12, 2001.

Copyright Notice

   Copyright (C) The Internet Society (2000). All Rights Reserved.

Abstract

   DHCP provides a powerful mechanism for IP host configuration.
   However, the configuration capability provided by DHCP does not
   include updating DNS, and specifically updating the name to address
   and address to name mappings maintained in the DNS.

   This document specifies a DHCP option which can be used to exchange
   information about a DHCP client's fully-qualified domain name, or
   'FQDN'.






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Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Models of Operation  . . . . . . . . . . . . . . . . . . . . .  3
   4.  The Client FQDN Option . . . . . . . . . . . . . . . . . . . .  5
   4.1 The Flags Field  . . . . . . . . . . . . . . . . . . . . . . .  5
   4.2 The RCODE Fields . . . . . . . . . . . . . . . . . . . . . . .  6
   4.3 The Domain Name Field  . . . . . . . . . . . . . . . . . . . .  6
   5.  DHCP Client behavior . . . . . . . . . . . . . . . . . . . . .  7
   6.  DHCP Server behavior . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
       References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12
       Full Copyright Statement . . . . . . . . . . . . . . . . . . . 14



































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1. Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119[6].

2. Introduction

   DNS (RFC1034[1], RFC1035[2]) maintains (among other things) the
   information about mapping between hosts' Fully Qualified Domain
   Names (FQDNs) RFC1594[4] and IP addresses assigned to the hosts. The
   information is maintained in two types of Resource Records (RRs): A
   and PTR. The A RR contains mapping from a FQDN to an IP address; the
   PTR RR contains mapping from an IP address to a FQDN.  The Dynamic
   DNS Updates specification (RFC2136[5]) describes a mechanism that
   enables DNS information to be updated over a network.

   DHCP RFC2131[3] provides a mechanism by which a host (a DHCP client)
   can acquire certain configuration information, along with its IP
   address(es). However, DHCP does not provide any mechanisms to update
   the DNS RRs that contain the information about mapping between the
   host's FQDN and its IP address(es) (A and PTR RRs). Thus the
   information maintained by DNS for a DHCP client may be incorrect - a
   host (the client) could acquire its address by using DHCP, but the A
   RR for the host's FQDN wouldn't reflect the address that the host
   acquired, and the PTR RR for the acquired address wouldn't reflect
   the host's FQDN.

   The Dynamic DNS Update protocol can be used to maintain consistency
   between the information stored in the A and PTR RRs and the actual
   address assignment done via DHCP. When a host with a particular FQDN
   acquires its IP address via DHCP, the A RR associated with the
   host's FQDN would be updated (by using the Dynamic DNS Updates
   protocol) to reflect the new address. Likewise, when an IP address
   is assigned to a host with a particular FQDN, the PTR RR associated
   with this address would be updated (using the Dynamic DNS Updates
   protocol) to reflect the new FQDN.

   Although this document refers to the A and PTR DNS record types and
   to DHCP assignment of IPv4 addresses, the same procedures and
   requirements apply for updates to the analogous RR types that are
   used when clients are assigned IPv6 addresses via DHCPv6.

3. Models of Operation

   When a DHCP client acquires a new address, a site's administrator
   may desire that one or both of the A RR for the client's FQDN and
   the PTR RR for the acquired address be updated. Therefore, two
   separate Dynamic DNS Update transactions occur. Acquiring an address


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   via DHCP involves two entities: a DHCP client and a DHCP server. In
   principle each of these entities could perform none, one, or both of
   the transactions. However, in practice not all permutations make
   sense. The DHCP client FQDN option is intended to operate in the
   following two cases:

   1.  DHCP client updates the A RR, DHCP server updates the PTR RR
   2.  DHCP server updates both the A and the PTR RRs

   The only difference between these two cases is whether the FQDN to
   IP address mapping is updated by a DHCP client or by a DHCP server.
   The IP address to FQDN mapping is updated by a DHCP server in both
   cases.

   The reason these two are important, while others are unlikely, has
   to do with authority over the respective DNS domain names. A DHCP
   client may be given authority over mapping its own A RRs, or that
   authority may be restricted to a server to prevent the client from
   listing arbitrary addresses or associating its address with
   arbitrary domain names. In all cases, the only reasonable place for
   the authority over the PTR RRs associated with the address is in the
   DHCP server that allocates the address.

   In any case, whether a site permits all, some, or no DHCP servers
   and clients to perform DNS updates into the zones which it controls
   is entirely a matter of local administrative policy. This document
   does not require any specific administrative policy, and does not
   propose one. The range of possible policies is very broad, from
   sites where only the DHCP servers have been given credentials that
   the DNS servers will accept, to sites where each individual DHCP
   client has been configured with credentials which allow the client
   to modify its own domain name. Compliant implementations MAY support
   some or all of these possibilities. Furthermore, this specification
   applies only to DHCP client and server processes: it does not apply
   to other processes which initiate dynamic DNS updates.

   This document describes a new DHCP option which a client can use to
   convey all or part of its domain name to a DHCP server.
   Site-specific policy determines whether DHCP servers use the names
   that clients offer or not, and what DHCP servers may do in cases
   where clients do not supply domain names.  Two other documents,
   "Resolving Name Conflicts"[14] and "Update Procedures"[15], provide
   additional guidance about the use of this new DHCP option.
   "Resolving Name Conflicts"[14] defines a protocol for arbitrating
   conflicts when collisions occur in the use of FQDNs by DHCP clients.
   "Update Procedures"[15] recommends a procedure which may be used to
   update DNS RRs for DHCP clients.




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4. The Client FQDN Option

   To update the IP address to FQDN mapping a DHCP server needs to know
   the FQDN of the client to which the server leases the address. To
   allow the client to convey its FQDN to the server this document
   defines a new DHCP option, called "Client FQDN". The FQDN Option
   also contains Flags and RCode fields which DHCP servers can use to
   convey information about DNS updates to clients.

   Clients MAY send the FQDN option, setting appropriate Flags values,
   in both their DISCOVER and REQUEST messages. If a client sends the
   FQDN option in its DISCOVER message, it MUST send the option in
   subsequent REQUEST messages.

   The code for this option is 81. Its minimum length is 4.

   The Format of the FQDN Option:


        Code   Len    Flags  RCODE1 RCODE2   Domain Name
       +------+------+------+------+------+------+--
       |  81  |   n  |      |      |      |       ...
       +------+------+------+------+------+------+--


4.1 The Flags Field


        0 1 2 3 4 5 6 7
       +-+-+-+-+-+-+-+-+
       |   MBZ   |E|O|S|
       +-+-+-+-+-+-+-+-+


   When a DHCP client sends the FQDN option in its DHCPDISCOVER and/or
   DHCPREQUEST messages, it sets the right-most bit (labelled "S") to
   indicate that it will not perform any Dynamic DNS updates, and that
   it expects the DHCP server to perform any FQDN-to-IP (the A RR) DNS
   update on its behalf. If this bit is clear, the client indicates
   that it intends to maintain its own FQDN-to-IP mapping update.

   If a DHCP server intends to take responsibility for the A RR update
   whether or not the client sending the FQDN option has set the "S"
   bit, it sets both the "O" bit and the "S" bit, and sends the FQDN
   option in its DHCPOFFER and/or DHCPACK messages.

   The data in the Domain Name field may appear in one of two formats:
   ASCII, or DNS-style binary encoding (without compression, of
   course), as described in RFC1035[2]. A client which sends the FQDN


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   option MUST set the "E" bit to indicate that the data in the Domain
   Name field is DNS binary encoded. If a server receives an FQDN
   option from a client, and intends to include an FQDN option in its
   reply, it MUST use the same encoding that the client used. The DNS
   encoding is recommended. The use of ASCII-encoded domain-names is
   fragile, and the use of ASCII encoding in this option should be
   considered deprecated.

   The remaining bits in the Flags field are reserved for future
   assignment. DHCP clients and servers which send the FQDN option MUST
   set the MBZ bits to 0, and they MUST ignore values in the part of
   the field labelled "MBZ".

4.2 The RCODE Fields

   The RCODE1 and RCODE2 fields are used by a DHCP server to indicate
   to a DHCP client the Response Code from any A or PTR RR Dynamic DNS
   Updates it has performed. The server may also use these fields to
   indicate whether it has attempted such an update before sending the
   DHCPACK message. Each of these fields is one byte long.

   Implementors should note that EDNS0 describes a mechanism for
   extending the length of a DNS RCODE to 12 bits. EDNS0 is specified
   in RFC2671[8]. Only the least-significant 8 bits of the RCODE from a
   Dynamic DNS Update will be carried in the Client FQDN DHCP Option.
   This provides enough number space to accomodate the RCODEs defined
   in the Dynamic DNS Update specification.

4.3 The Domain Name Field

   The Domain Name part of the option carries all or part of the FQDN
   of a DHCP client. A client may be configured with a fully-qualified
   domain name, or with a partial name that is not fully-qualified. If
   a client knows only part of its name, it MAY send a single label,
   indicating that it knows part of the name but does not necessarily
   know the zone in which the name is to be embedded. The data in the
   Domain Name field may appear in one of two formats: ASCII (with no
   terminating NULL), or DNS encoding as specified in RFC1035[2]. If
   the DHCP client wishes to use DNS encoding, it MUST set the
   third-from-rightmost bit in the Flags field (the "E" bit); if it
   uses ASCII encoding, it MUST clear the "E" bit.

   A DHCP client that can only send a single label using ASCII encoding
   includes a series of ASCII characters in the Domain Name field,
   excluding the "." (dot) character. The client SHOULD follow the
   character-set recommendations of RFC1034[1] and RFC1035[2]. A client
   using DNS binary encoding which wants to suggest part of its FQDN
   MAY send a non-terminal sequence of labels in the Domain Name part
   of the option.


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5. DHCP Client behavior

   The following describes the behavior of a DHCP client that
   implements the Client FQDN option.

   If a client that owns/maintains its own FQDN wants to be responsible
   for updating the FQDN to IP address mapping for the FQDN and
   address(es) used by the client, then the client MUST include the
   Client FQDN option in the DHCPREQUEST message originated by the
   client. A DHCP client MAY choose to include the Client FQDN option
   in its DISCOVER messages as well as its REQUEST messages. The
   rightmost ("S") bit in the Flags field in the option MUST be set to
   0. Once the client's DHCP configuration is completed (the client
   receives a DHCPACK message, and successfully completes a final check
   on the parameters passed in the message), the client MAY originate
   an update for the A RR (associated with the client's FQDN). The
   update MUST be originated following the procedures described in
   RFC2136[5] and "Resolving Name Conflicts"[14]. If the DHCP server
   from which the client is requesting a lease includes the FQDN option
   in its ACK message, and if the server sets both the "S" and the "O"
   bits (the two rightmost bits) in the option's flags field, the DHCP
   client MUST NOT initiate an update for the name in the Domain Name
   field.

   A client can choose to delegate the responsibility for updating the
   FQDN to IP address mapping for the FQDN and address(es) used by the
   client to the server.  In order to inform the server of this choice,
   the client SHOULD include the Client FQDN option in its DHCPREQUEST
   message. The rightmost (or "S") bit in the Flags field in the option
   MUST be set to 1. A client which delegates this responsibility MUST
   NOT attempt to perform a Dynamic DNS update for the name in the
   Domain Name field of the FQDN option. The client MAY supply an FQDN
   in the Client FQDN option, or it MAY supply a single label (the
   most-specific label), or it MAY leave that field empty as a signal
   to the server to generate an FQDN for the client in any manner the
   server chooses.

   Since there is a possibility that the DHCP server may be configured
   to complete or replace a domain name that the client was configured
   to send, the client might find it useful to send the FQDN option in
   its DISCOVER messages. If the DHCP server returns different Domain
   Name data in its OFFER message, the client could use that data in
   performing its own eventual A RR update, or in forming the FQDN
   option that it sends in its REQUEST message. There is no requirement
   that the client send identical FQDN option data in its DISCOVER and
   REQUEST messages. In particular, if a client has sent the FQDN
   option to its server, and the configuration of the client changes so
   that its notion of its domain name changes, it MAY send the new name
   data in an FQDN option when it communicates with the server again.


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   This may allow the DHCP server to update the name associated with
   the PTR record, and, if the server updated the A record representing
   the client, to delete that record and attempt an update for the
   client's current domain name.

   A client that delegates the responsibility for updating the FQDN to
   IP address mapping to a server might not receive any indication
   (either positive or negative) from the server whether the server was
   able to perform the update. In this case the client MAY use a DNS
   query to check whether the mapping is updated.

   A client MUST set the RCODE1 and RCODE2 fields in the Client FQDN
   option to 0 when sending the option.

   If a client releases its lease prior to the lease expiration time
   and the client is responsible for updating its A RR, the client
   SHOULD delete the A RR (following the procedures described in
   "Resolving Name Conflicts"[14]) associated with the leased address
   before sending a DHCP RELEASE message. Similarly, if a client was
   responsible for updating its A RR, but is unable to renew its lease,
   the client SHOULD attempt to delete the A RR before its lease
   expires. A DHCP client which has not been able to delete an A RR
   which it added (because it has lost the use of its DHCP IP address)
   should attempt to notify its administrator.

6. DHCP Server behavior

   When a server receives a DHCPREQUEST message from a client, if the
   message contains the Client FQDN option, and the server replies to
   the message with a DHCPACK message, the server may be configured to
   originate an update for the PTR RR (associated with the address
   leased to the client). Any such update MUST be originated following
   the procedures described in "Resolving Name Conflicts"[14]. The
   server MAY complete the update before the server sends the DHCPACK
   message to the client. In this case the RCODE from the update MUST
   be carried to the client in the RCODE1 field of the Client FQDN
   option in the DHCPACK message. Alternatively, the server MAY send
   the DHCPACK message to the client without waiting for the update to
   be completed.  In this case the RCODE1 field of the Client FQDN
   option in the DHCPACK message MUST be set to 255.  The choice
   between the two alternatives is entirely determined by the
   configuration of the DHCP server. Servers SHOULD support both
   configuration options.

   When a server receives a DHCPREQUEST message containing the Client
   FQDN option, the server MUST ignore the values carried in the RCODE1
   and RCODE2 fields of the option.

   In addition, if the Client FQDN option carried in the DHCPREQUEST


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   message has the "S" bit in its Flags field set, then the server MAY
   originate an update for the A RR (associated with the FQDN carried
   in the option) if it is configured to do so by the site's
   administrator, and if it has the necessary credentials. The server
   MAY be configured to use the name supplied in the client's FQDN
   option, or it MAY be configured to modify the supplied name, or
   substitute a different name.

   Any such update MUST be originated following the procedures
   described in "Resolving Name Conflicts"[14]. The server MAY
   originate the update before the server sends the DHCPACK message to
   the client. In this case the RCODE from the update [RFC2136] MUST be
   carried to the client in the RCODE2 field of the Client FQDN option
   in the DHCPACK message.  Alternatively the server MAY send the
   DHCPACK message to the client without waiting for the update to be
   completed. In this case the RCODE2 field of the Client FQDN option
   in the DHCPACK message MUST be set to 255. The choice between the
   two alternatives is entirely up to the DHCP server. In either case,
   if the server intends to perform the DNS update and the client's
   REQUEST message included the FQDN option, the server SHOULD include
   the FQDN option in its ACK message, and MUST set the "S" bit in the
   option's Flags field.

   Even if the Client FQDN option carried in the DHCPREQUEST message
   has the "S" bit in its Flags field clear (indicating that the client
   wants to update the A RR), the server MAY be configured by the local
   administrator to update the A RR on the client's behalf. A server
   which is configured to override the client's preference SHOULD
   include an FQDN option in its ACK message, and MUST set both the "O"
   and "S" bits in the FQDN option's Flags field. The update MUST be
   originated following the procedures described in "Resolving Name
   Conflicts"[14]. The server MAY originate the update before the
   server sends the DHCPACK message to the client. In this case the
   RCODE from the update [RFC2136] MUST be carried to the client in the
   RCODE2 field of the Client FQDN option in the DHCPACK message.
   Alternatively, the server MAY send the DHCPACK message to the client
   without waiting for the update to be completed. In this case the
   RCODE2 field of the Client FQDN option in the DHCPACK message MUST
   be set to 255. Whether the DNS update occurs before or after the
   DHCPACK is sent is entirely up to the DHCP server's configuration.

   When a DHCP server sends the Client FQDN option to a client in the
   DHCPACK message, the DHCP server SHOULD send its notion of the
   complete FQDN for the client in the Domain Name field. The server
   MAY simply copy the Domain Name field from the Client FQDN option
   that the client sent to the server in the DHCPREQUEST message. The
   DHCP server MAY be configured to complete or modify the domain name
   which a client sent, or it MAY be configured to substitute a
   different name. If the server initiates a DDNS update which is not


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   complete until after the server has replied to the DHCP client, the
   server's The server MUST use the same encoding format (ASCII or DNS
   binary encoding) that the client used in the FQDN option in its
   DHCPREQUEST, and MUST set the "E" bit in the option's Flags field
   accordingly.

   If a client's DHCPREQUEST message doesn't carry the Client FQDN
   option (e.g., the client doesn't implement the Client FQDN option),
   the server MAY be configured to update either or both of the A and
   PTR RRs. The updates MUST be originated following the procedures
   described in "Resolving Name Conflicts"[14].

   If a server detects that a lease on an address that the server
   leases to a client has expired, the server SHOULD delete any PTR RR
   which it added via dynamic update. In addition, if the server added
   an A RR on the client's behalf, the server SHOULD also delete the A
   RR. The deletion MUST follow the procedures described in "Resolving
   Name Conflicts"[14].

   If a server terminates a lease on an address prior to the lease's
   expiration time, for instance by sending a DHCPNAK to a client, the
   server SHOULD delete any PTR RR which it associated with the address
   via DNS Dynamic Update. In addition, if the server took
   responsibility for an A RR, the server SHOULD also delete that A RR.
   The deletion MUST follow the procedures described in "Resolving Name
   Conflicts"[14].

7. Security Considerations

   Unauthenticated updates to the DNS can lead to tremendous confusion,
   through malicious attack or through inadvertent misconfiguration.
   Administrators should be wary of permitting unsecured DNS updates to
   zones which are exposed to the global Internet. Both DHCP clients
   and servers SHOULD use some form of update request origin
   authentication procedure (e.g., Simple Secure DNS Update[11]) when
   performing DNS updates.

   Whether a DHCP client may be responsible for updating an FQDN to IP
   address mapping or whether this is the responsibility of the DHCP
   server is a site-local matter. The choice between the two
   alternatives may be based on the security model that is used with
   the Dynamic DNS Update protocol (e.g., only a client may have
   sufficient credentials to perform updates to the FQDN to IP address
   mapping for its FQDN).

   Whether a DHCP server is always responsible for updating the FQDN to
   IP address mapping (in addition to updating the IP to FQDN mapping),
   regardless of the wishes of an individual DHCP client, is also a
   site-local matter. The choice between the two alternatives may be


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   based on the security model that is being used with dynamic DNS
   updates. In cases where a DHCP server is performing DNS updates on
   behalf of a client, the DHCP server should be sure of the DNS name
   to use for the client, and of the identity of the client.

   Currently, it is difficult for DHCP servers to develop much
   confidence in the identities of its clients, given the absence of
   entity authentication from the DHCP protocol itself. There are many
   ways for a DHCP server to develop a DNS name to use for a client,
   but only in certain relatively unusual circumstances will the DHCP
   server know for certain the identity of the client. If DHCP
   Authentication[10] becomes widely deployed this may become more
   customary.

   One example of a situation which offers some extra assurances is one
   where the DHCP client is connected to a network through an MCNS
   cable modem, and the CMTS (head-end) ensures that MAC address
   spoofing simply does not occur. Another example of a configuration
   that might be trusted is one where clients obtain network access via
   a network access server using PPP. The NAS itself might be obtaining
   IP addresses via DHCP, encoding a client identification into the
   DHCP client-id option.  In this case, the network access server as
   well as the DHCP server might be operating within a trusted
   environment, in which case the DHCP server could be configured to
   trust that the user authentication and authorization procedure of
   the remote access server was sufficient, and would therefore trust
   the client identification encoded within the DHCP client-id.

8. Acknowledgements

   Many thanks to Mark Beyer, Jim Bound, Ralph Droms, Robert Elz, Peter
   Ford, Edie Gunter, Andreas Gustafsson, R. Barr Hibbs, Kim Kinnear,
   Stuart Kwan, Ted Lemon, Ed Lewis, Michael Lewis, Josh Littlefield,
   Michael Patton, and Glenn Stump for their review and comments.

References

   [1]   Mockapetris, P., "Domain names - Concepts and Facilities", RFC
         1034, Nov 1987.

   [2]   Mockapetris, P., "Domain names - Implementation and
         Specification", RFC 1035, Nov 1987.

   [3]   Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
         March 1997.

   [4]   Marine, A., Reynolds, J. and G. Malkin, "FYI on Questions and
         Answers to Commonly asked ``New Internet User'' Questions",
         RFC 1594, March 1994.


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   [5]   Vixie, P., Thomson, S., Rekhter, Y. and J. Bound, "Dynamic
         Updates in the Domain Name System", RFC 2136, April 1997.

   [6]   Bradner, S., "Key words for use in RFCs to Indicate
         Requirement Levels", RFC 2119, March 1997.

   [7]   Eastlake, D., "Domain Name System Security Extensions", RFC
         2535, March 1999.

   [8]   Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671,
         August 1999.

   [9]   Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington,
         "Secret Key Transaction Authentication for DNS (TSIG)
         (draft-ietf-dnsext-tsig-*)", July 1999.

   [10]  Droms, R. and W. Arbaugh, "Authentication for DHCP Messages
         (draft-ietf-dhc-authentication-*)", June 1999.

   [11]  Wellington, B., "Simple Secure DNS Dynamic Updates
         (draft-ietf-dnsext-simple-secure-update-*)", June 1999.

   [12]  Stapp, M., Gustafsson, A. and T. Lemon, "A DNS RR for encoding
         DHCP Information (draft-ietf-dnsext-dhcid-rr-*)", July 2000.

   [13]  Rivest, R., "The MD5 Message Digest Algorithm", RFC 1321,
         April 1992.

   [14]  Stapp, M., "Resolution of DNS Name Conflicts Among DHCP
         Clients (draft-ietf-dhc-ddns-resolution-*.txt)", July 2000.

   [15]  Stapp, M., "Recommended Procedures for DHCP Updates of DNS RRs
         (draft-ietf-dhc-ddns-procedure-*.txt)", July 2000.


Authors' Addresses

   Mark Stapp
   Cisco Systems, Inc.
   250 Apollo Dr.
   Chelmsford, MA  01824
   US

   Phone: 978.244.8498
   EMail: mjs@cisco.com






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   Yakov Rekhter
   Cisco Systems, Inc.
   170 Tasman Dr.
   San Jose, CA  95134
   US

   Phone: 914.235.2128
   EMail: yakov@cisco.com











































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Acknowledgement

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