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INTERNET-DRAFT                                                  J. Bound
DHC Working Group                                 Digital Equipment Corp
Obsoletes: draft-ietf-dhc-dhcpv6-02.txt                    November 1995



         Dynamic Host Configuration Protocol for IPv6 (DHCPv6)

                      draft-ietf-dhc-dhcpv6-03.txt


Status of this Memo

   This document is a submission to the DHC Working Group of the
   Internet Engineering Task Force (IETF).  Comments should be submitted
   to the dhcp-v6@bucknell.edu mailing list.

   This document is an Internet-Draft.  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.''

   To learn the current status of any Internet-Draft, please check the
   ``1id-abstracts.txt'' listing contained in the Internet- Drafts
   Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
   munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
   ftp.isi.edu (US West Coast).

   Distribution of this document is unlimited.

Abstract

   This document is an Internet application protocol, for IP version 6
   (IPv6), that specifies a client/server model for communications
   between hosts to dynamically configure parameters for a network, and
   autoconfigure addresses within a stateful model.  This document
   supports the model for IPv6 Stateless Address Autoconfiguration,
   where there are clear integration points between stateless and
   stateful address autoconfiguration for IPv6.


















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Table of Contents:

1. Introduction.................................................3
1.1. Requirements...............................................3
2. Terminology and Definitions..................................4
2.1. IPv6 Terminology...........................................4
2.2. DHCPv6 Terminology.........................................6
3. Protocol Design Model........................................9
3.1. Design Goals...............................................9
3.2. Request/Response Model....................................10
3.3. Leased Address Model......................................11
3.3.1. Address Lifetimes.......................................11
3.3.2. Duplicate Address Detection.............................12
3.3.3. Releasing Infinite Lifetime Addresses...................13
3.4. DNS Host Name Autoregistration Model......................13
4. Request/Response Processing.................................13
4.1. Processing when Server Address is not Known...............14
4.2. Processing when Server Address is Known...................16
4.3. Retransmission and Configuation Variables.................16
5. Datagram and Field Definitions..............................18
5.1. Datagram..................................................18
5.2. Field Definitions.........................................19
6. Client/Server Message Formats...............................21
6.1. Client/Server UDP Ports, Multicast Group, and Addresses...21
6.2. Client DISCOVER and CONF-REQUEST Messages.................21
6.3. Server CONF-RESPONSE Message..............................23
6.4. Client ACCEPT Message.....................................24
6.5. Server SERVER-ACK Message.................................25
6.6. Client RELEASE Message....................................27
7. Relay-Agent Processing......................................28
8. Security Considerations.....................................29
Appendix A - Related Work in IPv6..............................29
Change History.................................................31
Acknowledgements...............................................33
References.....................................................33
Authors' Address...............................................34
























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1. Introduction

   DHCPv6 is an Internet application protocol, for IP version 6 (IPv6),
   that specifies a client/server model for communications between hosts
   to dynamically configure parameters for a network, and autoconfigure
   addresses within a stateful model.  DHCPv6 supports the model for
   IPv6 Stateless Address Autoconfiguration [IPv6-ADDRCONF], where there
   are clear integration points between stateless and stateful address
   autoconfiguration for IPv6.

   DHCPv6 uses a set of request/response messages to support a
   transaction processing model where a commit to the data can be
   verified by both the client and server.  This affords DHCPv6 the
   ability in the future to support dynamic updates to data located
   within a sites network.  In addition to the capability of verifying
   commits to transactions a recovery mechanism is specified, should
   commits need to be rolled back during the course of a DHCPv6
   transaction being processed.

   DHCPv6 supports optional configuration parameters and processing for
   hosts through its companion document Options for the Dynamic Host
   Configuration Protocol for IPv6 [DHCPv6-OPT].

   The IPv6 Addressing Architecture [IPv6-ADDR] and IPv6 Stateless
   Address Autoconfiguration specifications provide new functionality
   not present in IP version 4 (IPv4).  This new IPv6 functionality
   provides inherent benefits to autoconfigure IPv6 addresses for nodes.
   In addition the IETF DNS Working Group has defined a method to
   support Dynamic Updates to DNS [DYN-UPD], which can be used by a node
   to add, delete, and change node names dynamically.

   DHCPv6 used several of the architecture principles from DHCPv4
   [DHCP-v4], but it is beyond the scope of this document to contrast
   and compare DHCPv6 with DHCPv4.

   Section 2 provides definitions for terminology used throughout this
   document.  Section 3 provides a review of the protocol design model
   parts that are inherent in the specification.  Section 4 provides the
   request/response model and interaction between the set of messages
   and the semantics for those messages.  Section 5 provides the
   datagram packet format and field definitions for that datagram.
   Section 6 provides the message formats and field contents for
   processing the client and server messages.  Section 7 provides the
   specification of how relay-agents and servers interact with clients,
   when the server is not on the same link as the client.  Section 8
   provides the security specifications that can be used to support
   security in DHCPv6.  Appendix A provides a summary of related work in
   IPv6 that will help put DHCPv6 in the context of IPv6 for the reader,
   and is not part of this specification, but here for information
   purposes.



1.1. Requirements

   Throughout this document, the words that are used to define the
   significance of the particular requirements are capitalized.  These
   words are:


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      o "MUST"

      This word or the adjective "REQUIRED" means that the item is an
      absolute requirement of this specification.

      o "MUST NOT"

      This phrase means the item is an absolute prohibition of this
      specification.

      o "SHOULD"

      This word or the adjective "RECOMMENDED" means that there may
      exist valid reasons in particular circumstances to ignore this
      item, but the full implications should be understood and the case
      carefully weighed before choosing a different course.

      o "SHOULD NOT"

      This phrase means that there may exist valid reasons in particular
      circumstances when the listed behavior is acceptable or even
      useful, but the full implications should be understood and the
      case carefully weighted before implementing any behavior described
      with this label.

      o "MAY"

      This word or the adjective "OPTIONAL" means that this item is
      truly optional.  One vendor may choose to include the item because
      a particular marketplace requires it or because it enhances the
      product, for example, another vendor may omit the same item.



2. Terminology and Definitions

   Relevant terminology from the IPv6 Protocol [IPv6-SPEC], IPv6
   Addressing Architecture, and IPv6 Stateless Address Autoconfiguration
   will be provided, and then the DHCPv6 terminology.


2.1. IPv6 Terminology

   IP           - Internet Protocol Version 6 (IPv6).  The terms
                  IPv4 and IPv6 are used only in contexts where
                  necessary to avoid ambiguity.

   node         - A device that implements IPv6.

   router       - A node that forwards IPv6 packets not explicitly
                  addressed to itself.

   host         - Any node that is not a router.

   upper-layer  - A protocol layer immediately above IP. Examples are
                  transport protocols such as TCP and UDP, control
                  protocols such as ICMP, routing protocols such as
                  OSPF, and internet or lower-layer protocols being


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                  "tunneled" over (e.g. encapsulated in) IP such as
                  IPX, Appletalk, or IP itself.

   link         - A communication facility or medium over which nodes
                  can communicate at the link layer, i.e., the layer
                  immediately below IPv6.  Examples are Ethernet
                  (simple or bridged); PPP links, X.25, Frame Relay,
                  or ATM networks; and internet (or higher) layer
                  "tunnels", such as tunnels over IPv4 or IPv6 itself.

   neighbors    - Nodes attached to the same link.

   interface    - A node's attachment to the link.

   address      - An IP layer identifier for an interface or a set
                  of interfaces.

   packet       - An IP header plus payload.

   communication
                - Any packet exchange between nodes that requires
                  that the address of each node used in the exchange
                  remain the same for the duration of the packet
                  exchange.  Examples are a TCP connection or UDP
                  request/response.

   unicast address
                - An identifier for a single interface.  A packet sent
                  to a unicast address is delivered to the interface
                  identified by that address.

   multicast address
                - An identifier for a set of interfaces (typically
                  belonging to different nodes).  A packet sent to a
                  multicast address is delivered to all interfaces
                  identified by that address.

   link-layer identifier
                - a link-layer identifier for an interface.  Examples
                  include IEEE 802 addresses for Ethernet links,
                  and E.164 addresses for ISDN links.

   link-local address
                - An address having link-only scope that can be used
                  to reach neighboring nodes attached to the same link.
                  All interfaces have a link-local address.

   preferred address
                - An address assigned to an interface whose use by
                  upper layer protocols is unrestricted.  Preferred
                  addresses may be used as the source or destination
                  address of packets sent from or to the interface.

   deprecated address
                - An address assigned to an interface whose use is
                  discouraged, but not forbidden.  A deprecated
                  address should no longer be used as a source address
                  in new communications. but packets sent to a


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                  deprecated address are delivered as expected.
                  A deprecated address may continue to be used as a
                  source address for the duration of existing
                  communications.

   valid address
                - A preferred or deprecated address.  A valid address
                  may appear as the source or destination address of a
                  packet, and the internet routing system is expected to
                  be able to deliver packets sent to a valid address.

   invalid address
                - An address that is not assigned to any interface. A
                  valid address becomes invalid when its valid
                  lifetime expires.  Invalid addresses should not appear
                  as the source or destination of a packet.

   preferred lifetime
                - The length of time that a valid address is preferred.
                  When the preferred lifetime expires, the address
                  becomes deprecated.

   valid lifetime
                - The length of time the address remains in the valid
                  state. The valid lifetime MUST be greater than or
                  equal to the preferred lifetime.  When the valid
                  lifetime expires, the address becomes invalid.

   interface token
                - A link-dependent identifier for an interface that
                  is (at least) unique per link.  Stateless Address
                  Autoconfiguration combines an interface token with
                  a prefix to form an address.  From an address
                  autoconfiguration perspective, an interface token
                  is a bit string of known length.  The exact length
                  of an interface token and the way it is created is
                  defined in a separate link-specific document that
                  covers issues related to the transmission of IP
                  over a particular link type (e.g., [IPv6-ETHER]).
                  In many cases the token will be the same as the
                  link-layer address.


2.2. DHCPv6 Terminology

   configuration parameters
                - Is any parameter that can be used by a node to
                  configure their network environment so the node can
                  communicate on a link or on an internet.

   client       - A client is a host that initiates requests on a link
                  to obtain: addresses, dynamic updates to DNS, or
                  other configuration parameters.

   server       - A server is a node that responds to requests from
                  clients on a link to provide: addresses, dynamic
                  updates to DNS, or other configuration parameters.



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   relay-agent  - A relay-agent is a node that listens on a link for
                  client requests, and then forwards the packet to a
                  server on the network.  The server will respond back
                  to the relay-agent, who will forward the response to
                  the client on the relay-agents link.

   message-type - The message-type defines the DHCPv6 protocol type for
                  this packet.

   message-flag - The message-flag defines an optional processing
                  notification for DHCPv6.  The message-flag can also
                  be used by the Options for DHCPv6 specification.

   error-code   - The error-code specifies errors from a client or
                  server.  The error-code can also be used by the
                  Options for DHCPv6 specification.

   total-addresses
                -  The total-addresses specifies the total number of
                   addresses being provided from a server to a client.
                   For each address there is a preferred and valid
                   lifetime.

   completed-transaction
                -  A completed-transaction is a communications exchange
                   between a client and server, using the required set
                   of DHCPv6 request/response message-types, where the
                   final response message in the request/response set
                   has been received by the client and by the server.

   transaction-ID
                - The transaction-ID is an integer identifier specified
                  by the client and is used by the client and server as
                  a transaction identifier to define the set of
                  request/response messages between the client and
                  server, for a clients interface token.

   client-link address
                - The client-link address specifies the clients
                  link-local address. The client-link address
                  is used by a relay-agent to respond to a client
                  on a link, after receiving a server response.

   server address
                - The server address specifies the address for the
                  server responding to a client.

   gateway address
                - The gateway address specifies the address of the
                  relay-agent for a server, which may be multiple
                  relay-agent hops away from the original relay-agent.

   client address
                - The client address specifies an address from a
                  server to be used by a client.

   binding      - A binding in DHCPv6 is an N-tuple that a client
                  and server MUST maintain in DHCPv6 for a


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                  completed-transaction, where N is the number of
                  configuration parameters for a client. An
                  implementation MUST support at least a 5-tuple
                  binding consisting of a clients interface token,
                  client address, preferred lifetime and valid
                  lifetime for each client address, and the
                  transaction-ID.





















































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3. Protocol Design Model

   This section is provided for implementors to understand the DHCPv6
   protocol design model from an architectural perspective.  Any
   conceptual models presented in this specification that provide
   implementation examples are not a requirement of the DHCPv6 protocol.


3.1. Design Goals

   The following list gives general design goals for DHCPv6.

      DHCPv6 should be a mechanism rather than a policy.  DHCPv6 must
      allow local system administrators control over configuration
      parameters where desired; e.g., local system administrators should
      be able to enforce local policies concerning allocation and access
      to local resources where desired.

      Hosts should require no manual configuration.  Each host should be
      able to discover appropriate local configuration parameters
      without user intervention, and incorporate those parameters into
      its own configuration.

      Networks should require no hand configuration for individual
      hosts.  Under normal circumstances, the network manager should not
      have to enter any per-host configuration parameters.

      DHCPv6 should not require a server on each link.  To allow for
      scale and economy, DHCPv6 must work across relay agents.

      A DHCPv6 client must be prepared to receive multiple responses to
      a request for configuration parameters.  Some installations may
      include multiple, overlapping DHCPv6 servers to enhance
      reliability and increase performance.

      DHCPv6 must coexist with statically configured, non-participating
      hosts and with existing network protocol implementations.

      DHCPv6 should as much as possible be compatible with IPv6
      Stateless Address Autoconfiguration.

      DHCPv6 must support the requirements of automated renumbering of
      IPv6 addresses.

      DHCPv6 servers should be able to support Dynamic Updates to DNS
      [DYN-UPD].

      It is NOT a design goal of DHCPv6 to specify a server to server
      protocol.

      It is NOT a design goal of DHCPv6 to specify how a server
      configuration parameter database is maintained or determined.

   The following list gives design goals specific to the transmission of
   the network layer parameters.

      Guarantee that any specific network address will not be in use by
      more than one host at a time.


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      Guarantee that client addresses that are not provided by DHCPv6
      will not be added to a servers configuration parameter database or
      the servers binding for a clients interface token.

      Retain host configuration parameters across client reboots.  A
      client should, whenever possible, be assigned the same
      configuration parameters in response to a request.

      Retain host configuration across server reboots, and, whenever
      possible, a host should be assigned the same configuration
      parameters despite restarts of the DHCPv6 mechanism,

      Allow automatic assignment of configuration parameters to new
      hosts to avoid hand configuration for new hosts.

      Support fixed or permanent allocation of configuration parameters
      to specific hosts.


3.2. Request/Response Model

   DHCPv6 uses a message-type to define whether the packet originated
   from a DHCPv6 server or client.  The set of packets used to complete
   a DHCPv6 transaction are defined as the request and response set.

   The message types are as follows:

      01 DISCOVER

         The DISCOVER message is a DHCPv6 multicast packet from a client
         to locate and request configuration parameters on a network,
         when the client does not know the servers address.


      02 CONF-REQUEST

         The CONF-REQUEST is an IPv6 unicast packet from a client to a
         server, when the client knows the IPv6 unicast address of a
         server, to request configuration parameters on a network.

      03 CONF-RESPONSE

         The CONF-RESPONSE is an IPv6 unicast packet from a server in
         response to a client DISCOVER or CONF-REQUEST, which provides
         the requested configuration parameters.

      04 ACCEPT

         The ACCEPT is a client response to a server CONF-RESPONSE. When
         the client used DISCOVER to locate a server and request
         configuration parameters on a network, the ACCEPT should be
         sent using the DHCPv6 multicast address, which also serves to
         inform other servers that responded to the DISCOVER they were
         not selected.  When the client used CONF-RESPONSE to request
         configuration parameters from a server whose address was known,
         the ACCEPT should be sent as an IPv6 unicast packet.  The
         ACCEPT is also an implied acknowledgment to the server selected
         that the client has received the servers configuration


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         parameters from the CONF-RESPONSE.

      05 SERVER-ACK

         The SERVER-ACK is an IPv6 unicast packet sent by a server to
         inform a client that it received an ACCEPT. The SERVER-ACK is
         used by the server to inform the client it has received an
         acknowledgment that the client has received the configuration
         parameters from the server, and denotes a completed-transaction
         to a server.  The server at that point MUST commit its bindings
         and any updates it may do for the client. The SERVER-ACK for
         the client denotes a completed-transaction. The client at that
         point MUST commit its bindings.

      06 RELEASE

         The RELEASE is used by the client for two reasons:

            1. To inform the server that the client did not receive the
               SERVER-ACK required to complete the client transaction,
               and the server should delete that binding and any
               updates it may have done on behalf of the client.

            2. To inform the server that the client is releasing a
               particular address or set of addresses, even though the
               lifetimes for those addresses may not have become
               invalid.

      The processing and algorithms for the request/response set of
      message-types will be discussed in section 4.0.


3.3. Leased Address Model

   The leased address model specifies a set of lifetimes associated with
   addresses returned by the server.  These lifetimes are meant to
   support site renumbering, and are completely compatible with the
   leasing model in IPv6 Stateless Address Autoconfiguration.

   The DHCPv6 philosophy is that the client has the responsibility to
   renew a lease for an address that is about to expire, or request a
   new address or the same address before the lease actually expires.
   If the client does not request a new lease for an address, the server
   MUST assume the client does not want a new lease for that address.
   The server MAY provide that address to another client requesting an
   address, after all other addresses available to the server have been
   exhausted.



3.3.1. Address Lifetimes

   An address returned to a client has a preferred and valid lifetime.
   The lifetimes represent the lease for addresses provided to the
   client, from the server.

   The client MAY request a value for the lifetimes returned by a
   server, but the client MUST use the lifetimes provided by the server


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   response.

   When an address for a client interface becomes deprecated the
   processing of the lease MUST be as follows:

      When the preferred lifetime of an address expires, the clients
      address becomes a deprecated address.  A deprecated address can be
      used as a source address in new communications and existing
      communications. But a deprecated address means the node will soon
      have an address whose valid lifetime will expire, when this
      happens the address cannot be used in any communications.

      An address is a deprecated until its valid lifetime expires at
      which point the address becomes an invalid address. An invalid
      address MUST NOT be used as a source address in outgoing
      communications, and MUST NOT be recognized as a valid destination
      address for incoming communications.

      Once an address is deprecated an implementation SHOULD request a
      new lease or address for that interface.

   If the clients preferred lifetime is zero for an address the address
   is immediately deprecated.

   Implementors of DHCPv6 would find it beneficial to coordinate the use
   of the preferred lifetime and valid lifetime for layers below the
   DHCPv6 application layer with their implementation of Stateless
   Address Autoconfiguration.  It is suggested that implementations use
   the same modules to configure addresses for stateless and stateful
   address autoconfiguration.  Implementors might want to consider an
   option to stop all new communications for a deprecated address, to
   support a very robust renumbering strategy, but this cannot be the
   default behavior.


3.3.2. Duplicate Address Detection

   DHCPv6 clients MUST support Duplicate Address Detection as specified
   in IPv6 Stateless Address Autoconfiguration. This will provide a high
   guarantee that DHCPv6 client addresses are not duplicated on a link.

   It is an option for a server to inform the client it does not have to
   perform Duplicate Address Detection by the server setting a value of
   01 in the message-flag in client responses.  In this case it is
   assumed that the server implementation is providing the guarantee
   that the client addresses returned are unique on the link.  It is
   implementation defined how a server verifies the uniqueness of client
   addresses on a link.

   A conceptual model of an implementation for DHCPv6 duplicate address
   detection is that the client DHCPv6 module, which supports updating
   the network interfaces for a host, would use the same application
   configuration interface for DHCPv6 as is used for IPv6 Stateless
   Address Autoconfiguration on an IPv6 conforming implementation.  An
   implementation can integrate and reuse the same modules in the
   network operating system kernel to spawn duplicate address detection,
   address lifetime processing, and the processing of deprecated and
   invalid addresses for existing and new connections.


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3.3.3. Releasing Infinite Lifetime Addresses

   DHCPv6 specifies no behavior which would require a client to listen
   for asynchronous messages from servers on a well known UDP port.  The
   reason for this is that minimal implementations may not be able to
   support such a feature in a client.  But DHCPv6 does permit the
   client to request an infinite lease for addresses.  The problem in
   this case is that though the server has permitted an infinite lease
   for a client it may later be required that the client give up that
   lease or the addresses, for some organizational reason.

   This specification leaves it as implementation defined how this
   problem is solved in a DHCPv6 network environment.

   One solution to the problem is to define an SNMP MIB for DHCPv6
   clients that when set by a network management agent causes a client
   to revalidate all of its addresses with the DHCPv6 server or issue a
   RELEASE to the server.



3.4. DNS Host Name Autoregistration Model

   It is important that DHCPv6 provide a server implementation set of
   options for Dynamic Updates to DNS (DYNDNS), to support the
   autoregistration of addresses to names in IPv6.  DYNDNS SHOULD be
   supported as a set of options in DHCPv6 as specified in the Options
   for DHCPv6 specification.  The minimum requirements to support DYNDNS
   in DHCPv6 are as follows:

      1.  Clients SHOULD be able to request or change names for
          addresses.

      2.  Servers SHOULD be able to provide names for addresses
          provided to a client.

      3.  If servers support DYNDNS then they MUST support the
          following:

          a)  Create, Update, and Delete of IPv6 AAAA Records
              [IPv6-DNS] as specified in DYNDNS [DYN-UPD].

          b)  Create, Update, and Delete of IPv6 IP6.INT Domain PTR
              records for any IPv6 AAAA addresses defined in a client
              DYNDNS request, or that the server automatically generated
              for a client.


4. Request/Response Processing

   The request/response processing for DHCPv6 is transaction based and
   uses a best-effort set of messages to guarantee a completed-
   transaction. The case where the client does not know the servers
   address is depicted, and then the case where the client does know the
   servers address is depicted.  Then the timeout and retransmission
   guidelines and configuration variables are discussed.




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4.1. Processing when Server Address is not Known

   The processing for the DHCPv6 request/response model when the client
   does not know the server address is as follows:

                   Server          Client          Server
               (not selected)                    (selected)

                     v               v               v
                     |               |               |
                     |       Begin Transaction       |
                     |               |               |
                     | _____________ | _____________ |
                     |      DISCOVER | DISCOVER      |
                     |       (DHCPv6 Multicast)      |
                     |               |               |
      Determine Client Configuration | Determine Client Configuration
                     |           (Unicast)           |
                     |  ___________  | ____________  |
                     | CONF-RESPONSE | CONF-RESPONSE |
                     |               |               |
                     |       Collects replies        |
                     |               |               |
                     |     Selects configuration     |
                     |               |               |
                     | _____________ | _____________ |
                     |       ACCEPT  |   ACCEPT      |
                     |        (DHCPv6 Multicast)     |
                     |               |               |
                     |               |       Commits Client Bindings
                     |               |            (Unicast)
                     |               |               |
                     |               | _____________ |
                     |               |  SERVER-ACK   |
                     |               |               |
                     |       Transaction Complete    |
                     |       Client commits Bindings |
                     |               |               |
                     |       IF the Client did not   |
                     |       receive the SERVER-ACK  |
                     |       delete the Bindings     |
                     |            (Unicast)          |
                     |               |               |
                     |               | _____________ |
                     |               |  RELEASE      |
                     |               |               |
                     |               |    Server deletes the Bindings
                     |               |    and rolls back any updates that
                     |               |    that may have been done for the
                     |               |    client.
                     |               |               |
                     v               v               v

   DHCPv6 uses the UDP [RFC-768] protocol to communicate between clients
   and servers.  UDP is not reliable, but DHCPv6 must provide some
   reliabilty between clients and servers.  The network trade-off is
   time versus the reliability that the completed set of
   request/response messages were received by both the client and the


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   server to define a completed-transaction.

   The request/response set is always started by a client either with a
   DISCOVER when the client does not know the servers address, or a
   CONF-REQUEST when the client does know the servers address.  The
   second message is from the server and is the CONF-RESPONSE.  The
   client then acknowledges the servers CONF-RESPONSE with an ACCEPT.
   At this point in the flow all data has been received and additional
   messages are defined to insure the transaction is completed, and to
   provide a method of recovery if either the client or server do not
   receive the messages to complete the transaction.

   The server after receiving the ACCEPT sends a SERVER-ACK, which is an
   acknowledgment to the client the server has received the clients
   ACCEPT.  At that point the time vs reliability trade-off in DHCPv6 is
   for the server to commit its bindings, and perform any updates as a
   result of the client messages (e.g. Update DNS).  If the client
   receives the SERVER-ACK, then the client can commit its bindings.
   But if the client does not receive the SERVER-ACK then it should send
   the server a RELEASE to inform the server that any bindings should be
   deleted and any updates for the client should be rolled back.  The
   client RELEASE provides the final recovery check in the DHCPv6
   request/response set to complete a transaction.

   Retransmission of messages is discussed in section 4.3.

   The ACCEPT in the flow above is a multicast packet which serves an
   overloaded function, to respond to the selected server, and to inform
   other servers on the network the client is not selecting them.































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4.2. Processing when Server Address is Known

   The processing for the DHCPv6 request/response model when the client
   does knows the server address is as follows (all packets are
   Unicast):

                                  Client          Server

                     v               v               v
                     |               |               |
                     |       Begin Transaction       |
                     |               |               |
                     |               | _____________ |
                     |               | CONF-REQUEST  |
                     |               |               |
                     |               |  Determine Client Configuration
                     |               |               |
                     |               | ____________  |
                     |               | CONF-RESPONSE |
                     |               |               |
                     |               | _____________ |
                     |               | ACCEPT        |
                     |               |               |
                     |               |  Commits Client Bindings
                     |               |               |
                     |               | _____________ |
                     |               |  SERVER-ACK   |
                     |               |               |
                     |       Transaction Complete    |
                     |       Client commits Bindings |
                     |               |               |
                     |       IF the Client did not   |
                     |       receive the SERVER-ACK  |
                     |               |               |
                     |               | _____________ |
                     |               |  RELEASE      |
                     |               |               |
                     |               |    Server deletes the Bindings
                     |               |    and rolls back any updates that
                     |               |    that may have been done for the
                     |               |    client.
                     |               |               |
                     v               v               v

The processing above is the same as was discussed in 4.1, except the
CONF-REQUEST is used by the client to request configuration parameters
from the server, and the CONF-REQUEST and ACCEPT are unicast packets.



4.3. Retransmission and Configuation Variables

   Configuration variables for a DHCPv6 implementation that MUST be
   configurable by a client or server are as follows:

      Retranstimer - The time in seconds that a DHCPv6 client or server
                     should wait before retransmitting a message.



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                     Default: 3 seconds.

      Maxretrans   - The maximum retransmissions that a DHCPv6 client
                     or server should retransmit, before logging a
                     DHCPv6 System Error to the user.

                     Default: 3 retransmissions.

   The problem with retransmissions occurs when they are continually
   received by a client or server (e.g. duplicate bindings or updates).

   To support informing a client or server that a retransmission is
   being done a second set of message-types are supported in DHCPv6 as
   follows:

      20 - DISCOVER-Retrans
      21 - CONF-REQUEST-Retrans
      22 - CONF-RESPONSE-Retrans
      23 - ACCEPT-Retrans
      24 - SERVER-ACK-Retrans
      25 - RELEASE-Retrans

   When a client or server retransmits a DHCPv6 packet at the
   application layer over UDP, they MUST change the message-type to the
   same message-type with the Retrans suffix.

   A response to a retransmission SHOULD be a duplicate of a previous
   response to the client or server.  It is implementation defined how
   this is accomplished.

   One method of retransmitting duplicates in an implementation
   conceptually is to use the 5-Tuple binding for a client or server to
   search for a previous response.  At a minimum the client interface
   token and transaction-ID will be present in all messages; hence a
   binding can be searched (whether committed or in process) to verify
   if a previous response has been sent.
























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5. Datagram and Field Definitions



5.1. Datagram


                              DHCPv6 Datagram

        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |  msg-type     |    msg-flag   |   error-code  | total-addrs   |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |            RESERVED           |      transaction-ID           |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                     interface token                           |
        |                        (8 octets)                             |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                       server address                          |
        |                        (16 octets)                            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                       gateway address                         |
        |                        (16 octets)                            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                   client-link address                         |
        |                        (16 octets)                            |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                      preferred lifetime                       |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                      valid lifetime                           |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |                        client address                         |
        |                         (16 octets)                           |
        |        (can be multiple addresses and lifetimes present)      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |  options (variable number and length)                         |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
























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5.2. Field Definitions

   All fields in the datagram MUST be initialized to binary zeroes by
   both the client and server messages unless otherwise noted in Section
   6.

   msg-type            - 1 octet integer value (message-type)

      Value        Description

      01           DISCOVER
      02           CONF-REQUEST
      03           CONF-RESPONSE
      04           ACCEPT
      05           SERVER-ACK
      06           RELEASE
      07-19        RESERVED
      20           DISCOVER-Retrans
      21           CONF-REQUEST-Retrans
      22           CONF-RESPONSE
      23           ACCEPT-Retrans
      24           SERVER-ACK-Retrans
      25           RELEASE-Retrans
      26-255       RESERVED

   msg-flag            - 1 octet integer value (message-flag)

      Value        Description

      01           Server - Duplicate Address Detection not Required.
      02-255       RESERVED

   error-code          - 1 octet integer value

      Value        Description

      01           Server - Addresses are not available at this time.
      02           Server - Address not known by the Server
      03-255       RESERVED

   total-addrs         - 1 octet integer value (total-addresses)

   RESERVED            - 2 octets Reserved for future use.

   transaction-ID      - 2 octets integer value

   interface token     - 8 octets link-dependent identifier

   server address      - 16 octets address

   gateway address     - 16 octets address

   client-link address - 16 octets link-local address

   preferred lifetime  - 4 octets integer value in seconds

   valid lifetime      - 4 octets integer value in seconds



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   client address      - 16 octets address

   options             - variable number of octets [DHCPv6-OPT]

























































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6. Client/Server Message Formats



6.1. Client/Server UDP Ports, Multicast Group, and Addresses

   A client MUST transmit all messages over UDP using UDP Server Port 547.

   A server or relay-agent MUST transmit all messages over UDP using UDP
   Client Port 546.

   A client MUST receive all messages over UDP using UDP Client Port 546.

   A server or relay-agent MUST receive all messages over UDP using UDP
   Server Port 547.

   A server or relay-agent MUST join the DHCPv6 Server/Relay-Agent
   multicast group well-known multicast address FF02:0:0:0:0:0:1:0.

   Servers on the same link as the client MUST use the source address in
   the IPv6 header from the client as the destination address in the
   servers response packet.  Servers that respond to relay-agents and
   relay-agent processing are discussed in section 7.

   In the cases where a client or server must retransmit messages the
   msg-type codes in this section are used as stated in section 4.3 with
   the values that represent the Retrans suffix for the msg-types.



6.2. Client DISCOVER and CONF-REQUEST Messages

   msg-type:

   If the client does not know the server address or wants to locate a new
   server to receive configuration parameters the client sets the msg-type
   to DISCOVER.  In this case the client MUST use as the destination
   IP address the DHCPv6 Server/Relay-Agent multicast address
   FF02:0:0:0:0:0:1:0.

   If the client knows the server address the client sets the msg-type to
   CONF-REQUEST. In this case the client MUST use as the destination
   IP address the server address.

   msg-flag:

   Set to binary zeroes.

   error-code:

   Set to binary zeroes.

   total-addrs:

   Set to the number of addresses the client is requesting.

   transaction-ID:



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   Set to an integer value.

   interface token:

   Set to a unique link dependent identifier for the clients interface.

   server address:

   Set to binary zeroes for DISCOVER.
   Set to server address for CONF-REQUEST.

   gateway address:

   Set to binary zeroes.

   client-link address:

   Set to the clients link-local address for the link on which the client
   transmitted the packet.

   preferred lifetime:

   Set to binary zeroes if the client is not requesting a lifetime.
   Set to the number of seconds the client wants for the lifetime.
   Set to all 1's (oxffffffff) if the client wants an infinite lifetime.

   The client must provide a preferred lifetime for each address
   requested.

   valid lifetime:

   Set to binary zeroes if the client is not requesting a lifetime.
   Set to the number of seconds the client wants for the lifetime.
   Set to all 1's (oxffffffff) if the client wants an infinite lifetime.

   The client must provide a valid lifetime for each address
   requested.  The valid lifetime must be greater than or equal to the
   preferred lifetime.

   client address:

   Set to binary zeroes if the client is not requesting a renewal for an
   existing address it received from a server.
   Set to an address the client previously received from a server when the
   client is requesting a new set of lifetimes for the address.

   A client MUST NOT provide a server with an address that was not given
   to the client by a server.  DHCPv6 does not permit a server to create
   leases for manual configured addresses, or update leases for addresses
   created by IPv6 Stateless Address Autoconfiguration.

   options:

   See Options for DHCPv6 specification [DHCPv6-OPT].






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6.3. Server CONF-RESPONSE Message

   msg-type:

   Set msg-type to CONF-RESPONSE.

   msg-flag:

   Set to 01 if the server knows addresses provided are verified to be
   unique, otherwise set to binary zeroes.

   error-code:

   Set to 01 if the server cannot provide any addresses to the client at
   this time.
   Set to 02 if the server detects an address from the client it did not
   provide to the client.

   total-addrs:

   Set to the number of addresses the server is returning the client.

   transaction-ID:

   Set to the value the client provided in the DISCOVER or CONF-REQUEST
   msg-type.

   interface token:

   Set to a unique link dependent identifier for the clients interface as
   provided in the clients DISCOVER or CONF-REQUEST msg-type.

   server address:

   The address of the server responding.

   gateway address:

   Set to the same value that existed when the server received the packet.

   client-link address:

   Set to the same value that existed when the server received the packet.

   preferred lifetime:

   Set to the value requested by the client or the value required by the
   server.

   valid lifetime:

   Set to the value requested by the client or the value required by the
   server.

   The valid lifetime MUST be greater than or equal to the preferred
   lifetime.

   client address:


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   Set to an address provided by the server if the client is not attempting
   to renew existing addresses, meaning the address fields from the client
   have a value of binary zeroes.

   If the error-code is set to 02 the server will only return the addresses
   that the server can verify were provided by the server.  If no addresses
   could be verified the total-addrs field, lifetimes, and client address
   will be set to binary zeroes.  In the case as far as the server is
   concerned the DHCPv6 transaction is completed and the server will not
   expect a client ACCEPT message to its CONF-RESPONSE message.

   options:

   See Options for DHCPv6 specification [DHCPv6-OPT].



6.4. Client ACCEPT Message

   msg-type:

   Set msg-type to ACCEPT.

   If the client sent a DISCOVER to request configuration parameters on the
   link, then the client should use as the IP destination address the DHCPv6
   Server/Relay-Agent multicast address FF02:0:0:0:0:0:1:0.

   If the client sent a CONF-REQUEST to request configuration parameters on
   the link, then the client should use as the IP destination address the server
   address in the CONF-RESPONSE from the server.

   If the client sees an error-code of 02 and the total-addrs field is
   zero, the server cannot process any of the addresses requested and the
   client should not send an ACCEPT to the server.  If the client sees an
   error-code of 02 and total-addrs does not equal zero it means the server
   dropped addresses that it could not locate requested by the client.

   msg-flag:

   Set to binary zeroes.

   error-code:

   Set to binary zeroes.

   total-addrs:

   Set to 1.

   transaction-ID:

   Set to the integer value that the client used on its initial DISCOVER or
   CONF-REQUEST msg-type to the server.

   interface token:

   Set to the unique link dependent identifier for the clients interface
   that was used for the clients initial DISCOVER or CONF-REQUEST msg-type


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   to the server.

   server address:

   Set to the address provided by the servers CONF-RESPONSE.

   gateway address:

   Set to binary zeroes.

   client-link address:

   Set to the clients link-local address for the link on which the client
   transmitted the packet.

   preferred lifetime:

   Set to the first or only preferred lifetime returned for an address by
   the server.

   valid lifetime:

   Set to the first or only valid lifetime returned for an address by the
   server.

   The valid lifetime MUST be greater than or equal to the preferred
   lifetime.

   client address:

   Set to the first or only address provided by the server.

   If the client did receive more than one address and lifetime, it MUST
   store this data in an implementation defined manner, so that it can
   issue a complete RELEASE for all addresses provided from the server
   CONF-RESPONSE, if necessary later.  But the ACCEPT does not need to carry
   all those addresses to acknowledge the servers CONF-RESPONSE packet in
   an ACCEPT.

   options:

   No options are present.



6.5. Server SERVER-ACK Message

   msg-type:

   Set msg-type to SERVER-ACK.

   If the client sent the ACCEPT to acknowledge a servers CONF-RESPONSE
   message on the DHCPv6 Server/Relay-Agent multicast address
   FF02:0:0:0:0:0:1:0, the server MUST look at the server address in the
   packet to determine if the ACCEPT is for them or not.

   If the message is not for a particular server then this is an indirect
   message to that particular server the client is not accepting them as


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   their server for this transaction, and MUST NOT send a SERVER-ACK to the
   clients ACCEPT.

   msg-flag:

   Set to binary zeroes.

   error-code:

   Set to binary zeroes.

   total-addrs:

   Set to 1.

   transaction-ID:

   Set to the integer value that the client used on its initial DISCOVER or
   CONF-REQUEST msg-type to the server.

   interface token:

   Set to the unique link dependent identifier for the clients interface
   that was used for the clients initial DISCOVER or CONF-REQUEST msg-type
   to the server.

   server address:

   Set to the servers address.

   gateway address:

   Set to the same value that existed when the server received the packet.

   client-link address:

   Set to the same value that existed when the server received the packet.

   preferred lifetime:

   Set to the value provided by the client.

   valid lifetime:

   Set to the value provided by the client.

   The valid lifetime MUST be greater than or equal to the preferred
   lifetime.

   client address:

   Set to the address provided by the client.

   At this point the server MUST commit the configuration parameters
   provided to the client from the servers CONF-RESPONSE.

   options:



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   No options are present.



6.6. Client RELEASE Message

   msg-type:

   Set msg-type to RELEASE.

   If the client had sent an ACCEPT to the server and received a SERVER-ACK
   for that message then the client MUST commit the configuration
   parameters provided by the servers CONF-RESPONSE and a RELEASE message
   is not required.  But if the client did not receive a SERVER-ACK
   in response to the clients ACCEPT, then the client MUST issue a RELEASE
   to the server.

   If the client no longer needs an address or has been notified to return
   an address to the server, then the client SHOULD issue a RELEASE to the
   server.

   msg-flag:

   Set to binary zeroes.

   error-code:

   Set to binary zeroes.

   total-addrs:

   Set to the total number of addresses the client is releasing.  In the
   case of a RELEASE where the client did not receive the SERVER-ACK this
   value MUST equal the total number of addresses for the servers
   CONF-RESPONSE.

   transaction-ID:

   Set to the integer value that the client used on its initial DISCOVER or
   CONF-REQUEST msg-type to the server.

   interface token:

   Set to the unique link dependent identifier for the clients interface
   that was used for the clients initial DISCOVER or CONF-REQUEST msg-type
   to the server.

   server address:

   Set to binary zeroes.

   gateway address:

   Set to binary zeroes.

   client-link address:

   Set to the clients link-local address for the link on which the client


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   transmitted the packet.

   preferred lifetime:

   Set to the valid lifetime returned for an address by the server.

   valid lifetime:

   Set to the valid lifetime returned for an address by the server.

   The valid lifetime MUST be greater than or equal to the preferred
   lifetime.

   client address:

   Set to the address provided by the server.

   The client will return the number of addresses and associated lifetimes
   provided in the servers CONF-RESPONSE.

   options:

   No options are present.



7. Relay-Agent Processing

   The relay-agent MUST use UDP DHCPv6 Server Port 547 as the UDP port to
   accept client responses in an implementation.

   The relay-agent MUST join the DHCP Server/Relay-Agent multicast group
   well-known multicast address FF02:0:0:0:0:0:1:0.

   When a DHCPv6 Relay-Agent hears a request from a DHCPv6 Client it MUST:

      If the gateway address is NOT zero then the relay-agent MUST:

         Put the relay-agents IP address in the gateway address field of
         the clients request packet.


   All relay-agents MUST:

      Put their relay-agent address as the source address for the IP
      header.

      Put the next relay-agent or known server address as the
      destination address in the IP header.

      Forward the packet to the to the next hop relay-agent or
      known server.

   When the remote server receives the client request from the relay-agent
   it will know its a remote client request (not on the servers link),
   because there is a gateway address in the request.  So servers MUST
   verify the gateway address is not zero, to determine if the clients request
   is from a remote link.


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   The server responds as specified in section 6.0, but uses the
   gateway address as the destination address in the IP header.

   When the relay-agent receives the remote servers response, it MUST
   forward the packet to the client, by using the client-link address as
   the source address for the IP Header.



8. Security Considerations

Security for DHCPv6 can be used as specified in [IPv6-SA], [IPv6-AUTH],
and [IPv6-ESP], which are implementation requirements for IPv6.



Appendix A - Related Work in IPv6

   The related work in IPv6 that would best serve an implementor to study
   is the IPv6 Specification [IPv6-SPEC], the IPv6 Addressing Architecture
   [IPv6-ADDR], IPv6 Stateless Address Autoconfiguration [IPv6-ADDRCONF],
   IPv6 Neighbor Discovery Processing [IPv6-ND], and Dynamic Updates to DNS
   [DYN-UPD].  These specifications afford DHCPv6 to build upon the IPv6
   work to provide both robust stateful autoconfiguration and
   autoregistration of DNS Host Names.

   The IPv6 Specification provides the base architecture and design of
   IPv6.  A key point for DHCPv6 implementors to understand is that IPv6
   requires that every link in the internet have an MTU of 576 octets or
   greater (in IPv4 the requirement is 68 octets).  This means that a
   UDP datagram of 536 octets will always pass through an internet (less 40
   octets for the IPv6 header), as long as there are no IP options prior to
   the UDP datagram in the packet. But, IPv6 does not support
   fragmentation at routers and fragmentation must take place end-to-end
   between hosts.  If a DHCPv6 implementation needs to send a packet
   greater than 536 octets it can either fragment the UDP datagram in UDP
   or use Path MTU Discovery [IPv6-SPEC] to determine the size of the
   packet that will traverse a network path.  It is implementation defined
   how this is accomplished in DHCPv6.

   The IPv6 Addressing Architecture Specification provides the address
   scope that can be used in an IPv6 implementation, and the various
   configuration architecture guidelines for network designers of the IPv6
   address space. Two advantages of IPv6 is that multicast addressing is well
   defined and nodes can create link-local addresses during initialization
   of the nodes environment.  This means that a host immediately can configure
   an IPv6 address at initialization for an interface, before communicating in
   any manner on the link.  The host can then use a well-known multicast address
   to begin communications to discover neighbors on the link, or as was
   discussed in the specification to locate a DHCPv6 server or relay-agent.

   The IPv6 Stateless Address Autoconfiguration Specification (addrconf)
   defines how a host can autoconfigure addresses based on neighbor discovery
   router advertisements, and the use of a validation lifetime to support
   renumbering of addresses on the Internet. In addition the addrconf
   specification defines the protocol interaction for a host to begin stateless
   or stateful autoconfiguration.  DHCPv6 is one vehicle to perform stateful
   autoconfiguration.  Compatibility with addrconf is a design goal of DHCPv6


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   where possible.

   IPv6 Neighbor Discovery (ND) is the node discovery protocol in IPv6
   (replaces and enhances functions of IPv4 ARP Model).  To truly
   understand IPv6 and addrconf it is strongly recommended that
   implementors understand IPv6 ND.

   Dynamic Updates to DNS is a specification that supports the
   dynamic update of DNS records for both IPv4 and IPv6.  DHCPv6 can use
   the dynamic updates to DNS to now integrate addresses and name space to
   not only support autoconfiguration, but also autoregistration in IPv6.

















































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Change History

   Changes from July 95 to November 95 Drafts:

      Refined request/response codes and processing to support transaction
      processing model.

      Permit multiple addresses and lifetimes in a request and response.

      Moved Dynamic Updates to DNS as an Option to be defined in that
      specification.

      Settled on using UDP as it supports DHCP client server model as opposed
      to TCP which has overhead for this model.

      Reformatted specification to support analysis, packet formats, and
      processing in their own sections to make it easier for implementors to
      read.

      Removed address count as it is not necessary for synchronization.

      Added error-code, msg-flag, and total-addrs fields.

      Made transaction-ID 2 octets.

      Updated terminology to coordinate with IPv6 Stateless Address
      Autoconfiguration.

      Added more implementation notes.

      Moved IPv6 Related Work to an Appendix.

      Fixed various bugs in the spec from DHC WG input.

      Added Security reference pointers.

      Removed options format, which will be in the options spec.

      Added retransmission configuration variables, msg-types, and logic.

   Changes from March 95 to July 95 Drafts:

      Used integer values instead of bit values for type and code fields.

      Used message-type and message-code fields and rely on looking at
      the fields in the datagram instead of multiple over-lapping
      request/response codes.

      Added address-count field processing to be specified by the
      client as opposed to the server, and the processing for when
      client and server address-counts become disjoint.

      Added Requirements wording for MUST, SHOULD, MAY, etc.

      Added Design Goals section.

      Redefined transaction-ID and interface-token.



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      Added Client/Server Binding definition and processing
      section to handle those bindings.

      Added more terminology, definitions, and rationale.

      Added model to support Dynamic Updates to DNS for Host Names.

      Reduced the request/response model to 3 packets by not doing
      a server confirm to a clients confirm to a servers response.

      Added model to support like lifetime fields for lease
      management to coordinate with IPv6 Stateless Address
      Autoconfiguration.

      Added model and processing definitions for future DHCPv6 Options
      Specification.

      Added gateway-address and client-link-address for relay-agent
      processing.

      Removed excessive use of the acronym DHCPv6 for section titles
      and when referencing clients and servers.

      Added Draft ***Open Issues*** Section for review by the DHC Working
      Group.

      Added Change History.

































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Acknowledgements

   The DHC Working Group for their time and input into the specification.
   A special thanks for the consistent input, ideas, and review by (in
   alphabetical order) Brian Carpenter, Ralph Droms, Thomas Narten, Jack
   Mccann, Charlie Perkins, Yakov Rekhter, Matt Thomas, Sue Thomson, and
   Phil Wells.

   The author would also like to thank Steve Deering and Bob Hinden,
   who have consistently taken the time to discuss the more complex
   parts of the IPv6 specifications.

   The author MUST also thank his employer for the opportunity and funding
   to work on DHCPv6 and IPv6 in general as an individual in the IETF.



References

   [DHCPv6-OPT]
       C. Perkins, "Options for the Dynamic Host Configuration
       Protocol for IPv6 (ODHCPv6)" Internet Draft, November 1995
       <draft TBD>

   [IPv6-SPEC]
       S. Deering and R. Hinden, "Internet Protocol Version 6
       [IPv6] Specification" Internet Draft, June 1995
       <draft-ietf-ipngwg-ipv6-spec-02.txt>

   [IPv6-ADDR]
       R. Hinden, S. Deering, Editors, "IP Version 6 Addressing Architecture"
       Internet Draft, June 1995
       <draft-ietf-ipngwg-ipv6-addr-arch-03.txt>

   [IPv6-ADDRCONF]
       S. Thomson, T. Narten, "IPv6 Stateless Address Autoconfiguration"
       Internet Draft, November 1995
       <draft-ietf-addrconf-ipv6-auto-05.txt>

   [IPv6-ND]
       T. Narten, E. Nordmark, and W. A. Simpson, "IPv6 Neighbor Discovery"
       Internet Draft, September 1995
       <draft-ietf-ipngwg-discovery-02.txt>

   [IPv6-DNS]
       S. Thompson and C. Huitema, "DNS Extensions to support IP
       version 6", Internet Draft, March 1995
       <draft-ietf-ipngwg-dns-00.txt>

   [RFC-1034]
       P. Mockapetris, "Domain Names - implementation and specification"
       STD-13, 11/01/87








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   [RFC-1035]
       P. Mockapetris, "Domain Names - concepts and facilities"
       STD-13, 11/01/87

   [DYN-UPD]
       S. Thomson, Y. Rekhter, J. Bound, "Dynamic Updates in the Domain
       Name System (DNS)" Internet Draft, March 1995
       <draft-ietf-dnsind-dynDNS-01.txt>

   [RFC-768]
       J. Postel, "User Datagram Protocol"
       STD-6, 08/28/80.

   [DHCP-v4]
       R. Droms, "Dynamic Host Configuration Protocol"
       RFC 1541 Proposed Standard, October 1993

   [IPv6-Ether]
       M. Crawford, "A Method for the Transmission of IPv6 Packets over
       Ethernet Networks", Internet Draft, October 1995
       <draft-ietf-ipngwg-ethernet-ntwrks-01.txt>

   [IPv6-SA]
       R. Atkinson, "Security Architecture for the Internet Protocol"
       RFC 1825, August 1995

   [IPv6-AUTH]
       R. Atkinson, "IP Authentication Header"
       RFC 1826, August 1995

   [IPv6-ESP]
       R. Atkinson, "IP Encapsulating Security Payload (ESP)"
       RFC 1827, August 1995



Authors' Address

    Jim Bound
    Digital Equipment Corporation
    110 Spitbrook Road, ZKO3-3/U14
    Nashua, NH 03062
    Phone: (603) 881-0400
    Email: bound@zk3.dec.com
















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