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INTERNET-DRAFT                                                  J. Bound
DHC Working Group                                 Digital Equipment Corp
Obsoletes: draft-ietf-dhc-dhcpv6-01.txt                          July 95



             Dynamic Host Configuration Protocol for IPv6

                      draft-ietf-dhc-dhcpv6-02.txt


Status of this Memo

   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

   DHCPv6 is an Internet application protocol that uses a Client/Server
   model to communicate between hosts.  DHCPv6 executes over the UDP
   [RFC-768] transport protocol, and the Internet Protocol Version 6
   (IPv6) [IPv6-SPEC]. DHCPv6 is an IPv6 specification for a statefull
   implementation of address autoconfiguration as referenced in IPv6
   Stateless Address Configuration [IPv6-ADDRCONF].  DHCPv6 supports
   mechanisms to autoconfigure host IPv6 addresseses, autoregister host
   names dynamically in the Domain Name System (DNS), and specifies the
   format to add future Configuration Parameter options to the protocol
   for extensibility.

   The work on this protocol will take place in the Dynamic Host
   Configuration (DHC) Working group. One may join the Working Group
   mail list by sending mail to host-conf-request@sol.eg.bucknell.edu.















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Table of Contents:

1.  Introduction................................................3
1.1 Requirements................................................3
2.  Terminology and Definitions.................................5
2.1 IPv6 Terminology............................................5
2.2 DHCPv6 Terminology..........................................6
3.  Protocol Design Model.......................................8
3.1 Related Work in IPv6........................................8
3.2 Design Goals................................................9
3.3 Request/Response Model.....................................10
3.4 Leased Address Model.......................................11
3.5 DNS Host Name Autoregistration Model.......................12
3.6 Defining Optional Configuration-Data.......................13
4.  Datagram and Data Formats..................................14
4.1 Datagram...................................................14
4.2 Data Formats...............................................14
5.  Client/Server Processing...................................16
5.1 Client Transmission........................................16
5.2 Server Transmission........................................16
5.3 Client/Server Bindings.....................................17
5.4 Client Requests............................................17
5.5 Server Response............................................18
5.6 Client Confirmations/Rejections............................19
6.  Relay-Agent Processing.....................................19
Draft ***Open Issues***........................................21
Change History.................................................22
Acknowledgements...............................................23
References.....................................................23
Authors' Addresses.............................................24






























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1.  Introduction

   DHCPv6 is an Internet application protocol that uses a Client/Server
   model to communicate between hosts.  DHCPv6 executes over the UDP
   [RFC-768] transport protocol, and the Internet Protocol Version 6
   (IPv6) [IPv6-SPEC]. DHCPv6 is an IPv6 specification for a statefull
   implementation of address autoconfiguration as referenced in IPv6
   Stateless Address Configuration [IPv6-ADDRCONF].  DHCPv6 supports
   mechanisms to autoconfigure host IPv6 addresseses, autoregister host
   names dynamically in the Domain Name System (DNS), and specifies the
   format to add future Configuration Parameter options to the protocol
   for extensibility.

   The IPv6 new version of the Internet Protocol, is being developed
   with 128bit addresses.  The IPv6 addressing architecture [IPv6-ADDR]
   and stateless address configuration [IPv6-ADDRCONF] specifications
   provide new functionality not present in the Internet Protocol
   version 4 (IPv4), which provide inherent benefits to autoconfigure
   IPv6 addresses for host nodes.  In addition the IETF DNS Working
   Group has work in progress to support Dynamic Updates to DNS [DYN-
   UPD], which can be used by a node to add, delete, and change host
   names dynamically.

   DHCPv6 uses the enhancements in IPv6 and DNS to define an efficient
   protocol, and is not required to support any IPv4 protocol for
   backward compatibility.  DHCPv6 does use many of the architectural
   principles in DHCP for IPv4 (DHCPv4) [DHCP-v4].  It is not within the
   scope of this document to compare and contrast DHCPv4 with DHCPv6.



1.1 Requirements

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

      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 impliciations 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


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      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.


















































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2.  Terminology and Definitions

   Terminology and Definitions are critical to the understanding of any
   IETF specification.  This Section will provide the terms and
   definitions used throughout this specification.  Relevant IPv6
   specification [IPv6-SPEC], IPv6 Addressing Architecture [IPv6-ADDR],
   and IPv6 Statelss Address Configuration [IPv6-ADDRCONF] terminology
   will be provided, then the DHCPv6 terminology.



2.1 IPv6 Terminology

   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.

   link: A communication facility or medium over which nodes can
   communicate at the link layer, i.e., the layer immediately below
   IPv6.  Examples are Ethernets (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 nodes's attachment to the link.

   address: An IPv6 layer identifier for an interface or a set of
   interfaces.

   packet: An IPv6 header plus payload.

   link MTU: The maximum transmission unit, i.e., maximum packet size in
   octets, that can be conveyed in one piece over a link.

   path MTU: The minimum link MTU of all the links in a path between a
   source node and a destination node.

   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-local address: The link-local address is for use on a single
   link.  On initialization of an interface, a host forms a link-local
   address by concatenating a well-known link-local prefix to a token
   that is unique per link.  For example, in the case of a host attached
   to a link that uses IEEE 802 addresses, the token is an IEEE 802
   address associated with the interface.

   validation-lifetime: This is the address lifetime for a single
   address provided to a host.  The validation-timer is in absolute time


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   and in seconds (e.g. 3 hours would have the value 10800).

   deprecation-liftetime: This is the lifetime for a single address the
   host uses to begin the deprecation of an address prior to the
   validation-lifetime expiring, so that the host can determine if the
   address can receive a new validation-lifetime.  The deprecation-
   lifetime is in absolute time and in seconds (e.g. 3 hours would have
   the value 10800).  The deprecation-lifetime MUST be no greater than
   the validation-lifetime.

   deprecated-address: This is a single address that is in the
   deprecated state on a host because the deprecation-lifetime period
   has expired.

   invalid-address:  This is a single address whose validation-lifetime
   has expired.



2.2 DHCPv6 Terminology

   configuration-type: Configuration Type defines an optional
   configuration parameter in the DHCPv6 protocol.

   configuration-data: Configuration Data is information a host can use
   to configure a host on a network, so that the host can interoperate
   with other hosts on a network.  Configuration Data will vary in
   length depending on the configuration type.

   client: A Client is a host that initiates requests on a link to
   obtain: addresses, DNS host name processing, or configuration-data.

   server: A Server is a host that responds to requests from clients on
   a link to provide: addresses, DNS host name processing, or
   configuration-data.

   relay-agent: A Relay-Agent is a router that listens on the link for
   clients requests, and then forwards the request to a server on the
   network.  The server will respond back to the Relay-Agent, who will
   forward the reply to the client on the Relay-Agents link.

   message-type: The Message-Type defines the DHCPv6 protocol operation
   for this packet.

   message-code: The Message-Code defines a notification for a message-
   type from a client or server.

   name-length: The Name-Length defines the length of the host name
   provided by a client or a server for DNS Autoregistration of host
   names.

   interface-token: The Interface-Token is specified by the client and
   is a unique opaque identifer for a clients interface, and must be
   accessbile after a client reboots (e.g. IEEE 802 MAC address).

   address-count: The address-count is specified by the client with any
   request sent to a server, and represents the number of addresses the
   client has received from a server for a specified interface-token.


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   client-address: The Client-Address is the field in the DHCPv6
   protocol that contains the address for the clients interface-token.

   server-address: The Server-Address is the field in the DHCPv6
   protocol that contains the address of the server responding to the
   clients request.

   gateway-address: The Gateway-Address is the field in the DHCPv6
   protocol that contains the relay-agents address, so a server, that
   may be multiple relay-agent hops away from the orginal relay-agent,
   can respond directly to the relay-agent that forwarded the request,
   by extracting the Gateway- Address to be used as the server packets
   destination address.

   client-link-address: The client-link-address is the field in the
   DHCPv6 protocol the relay-agents use to save the clients source
   address in the IPv6 header, so they can respond back to the server on
   the link.

   transaction-ID: The Transaction-ID is specified by the client as an
   opaque transaction identifier, which uniquely identifies the current
   operation between the client and the server.  The server may utilize
   this transaction identifier in order to detect duplicate transactions
   and to provide context between messages in a multi-message exchange
   with a client who has multiple requests for the same interface-token.

   host-name:  The Host-Name is the name to be associated with an
   address.  If the name-length is zero then the Host-Name is not
   present in the DHCPv6 request or response.

   binding:  The Binding in DHCPv6 is a N-tuple that a client and server
   MUST maintain in DHCPv6 for each completed transaction, where N is
   the number of configuration-data identifiers for a client.  An
   implementation MUST support at least a 4-tuple Binding consisting of
   the clients interface-token, address, validation-lifetime, and
   deprecation-lifetime for that address.  An example of a completed
   transaction in DHCPv6 is when the client requests an address for an
   interface-token and receives an address and lease for that token.  It
   is implementation defined if greater than a 4-tuple Binding is
   supported by an implementation, and is not prohibited by this
   specification.



















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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.  It provides
   related work in IPv6 that influenced the protocol design and the
   design goals.  The request/response protocol model is discussed and
   the objective of this model in the design.  The leased address
   strategy and purpose is discussed. The objective of the
   autoregistration for DNS Host Names is discussed and the capabilities
   that are possible in this specification.  The client/server model is
   discussed to prepare an implementor for the client/server processing
   provided later in the specification.  Then the configuration options
   are defined and how they are used to build additional extensible
   configuration-data for DHCPv6.




3.1 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 Configuration
   [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 statefull
   autoconfiguration and autoregistration of DNS Host Names.  In
   addition related work for DHCP for IPv4 is directly related to
   DHCPv6.

   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 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 ascertain 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 will be
   discussed later in the specification locate a DHCPv6 server or
   relay-agent.

   The IPv6 Stateless Address Configuration Specification (addrconf)


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   defines how a host can autoconfigure addresses based on neighbor
   discovery router advertisements, and the use of a validation-lifetime
   and a deprecation-lifetime for addresses.  In addition the addrconf
   specification defines the protocol interaction for a host to begin
   stateless or statefull autoconfiguration.  DHCPv6 is one vehicle to
   perform statefull autoconfiguration.  Compatibility with addrconf is
   a design goal of DHCPv6 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.  This will be discussed
   further later in this section of the specification.  An implementor
   cannot implement DHCPv6 without understanding Dyanmic Updates to DNS.



3.2 Design Goals

   The following list gives general design goals for DHCPv6.  Most
   DHCPv4 Design Goals [DHCP-v4] are kept in this specification.

      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 Configuration.

      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


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      protocol.

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

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

      Retain host configuration across host reboot.  A client should,
      whenever possible, be assigned the same configuration-data in
      response to each 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.

      Clients must not assume that addresses are updated to the DNS,
      unless the server provides a host-name with an address to a
      client.



3.3 Request/Response Model

   DHCPv6 uses a message type to define whether the packet orginated
   from a DHCPv6 Server or Client.

   The message types are as follows:

      01 - client-configuration-request
      02 - client-confirm-response
      03 - client-reject-response
      04 - server-configuration-response

   Request/Response Model States

      1. Request (client)
      2. Response with configuration-data or error found (server).
      3. Confirmation Response or reject (client).

   The time out period for a client or server to wait for a response
   MUST NOT exceed 3 minutes.  When a client or server times out waiting
   for a response to a packet sent, the implementation MUST NOT commit
   any binding based on the configuration-data sent in the packet.  It
   is implementation defined if the client or server packet is


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   retransmitted.



3.4 Leased Address Model

   An address returned to a client has a validation-lifetime and
   deprecation-lifetime.  The lifetimes represent the lease for a single
   address for a client.  The server MUST provide a validation-lifetime
   and SHOULD provide a deprecation-lifetime to a client in a server
   response packet to a clients request for an address.

   The client may suggest a value for the lifetimes in an address
   request to a server, or leave them as zero. The client MUST use the
   lifetimes provided by the server response if the values are different
   than the lifetimes requested by the client.

   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,
   and the server MAY provide that address to another client requesting
   an address.

   If the the client has a deprecation-lifetime for an address the
   processing of the lease SHOULD be as follows:

      When the deprecation-lifetime of an address expires, the clients
      address becomes a deprecated-address.  A deprecated address SHOULD
      NOT be used as a source address in new communications. However, a
      deprecated-address SHOULD continue to be used as a source address
      if it is in use in existing communications.  Implementors of
      DHCPv6 SHOULD coordinate the use of the validation-lifetime and
      deprecation-lifetime for layers below the DHCPv6 application layer
      with their implementation of IPv6 Stateless Address Configuration
      [IPv6-ADDRCONF].

      An address is a deprecated-address until its invalidation-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 in incoming communications.

   If the clients deprecation-lifetime is zero for an address the
   processing for the lease SHOULD be as follows:

      There is no concept of a deprecated-address for a client if the
      deprecation-lifetime is zero when provided to the client in a
      server response.  The address for the client is valid until the
      validation-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 in incoming communications.






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3.5 DNS Host Name Autoregistration Model

   DHCPv6 supports the autoregistration of DNS Host names and providing
   DNS Host Names with addresses for clients.  Autoregistration is
   supported by the presence of the name field in DHCPv6, which the
   client may provide to the server in a request.  In addition a server
   may provide a DNS Host Name with an IPv6 address to a client in a
   response.

   If the name-length field is zero, there is no name field contained in
   the packet.

   DHCPv6 only specifies the name-field, and not the actual protocol or
   primitives to interact with DNS.  The functions that the server uses
   to interact with the DNS to provide autoregistration is defined in
   Dynamic Updates to DNS [DYN-UPD].  DHCPv6 servers SHOULD support
   Dynamic Updates to DNS.

   If the client provides a Host Name (HN) or a Fully Qualified Domain
   Name (FQDN) [RFC 1034&1035]:

      The server SHOULD perform a DNS query for the HN or FQDN IPv6 DNS
      AAAA resource record [IPv6-DNS]:

      If the name is found and the address does not match the clients
      address for the name provided by the client, the server SHOULD add
      this address to the DNS name record (multiple addresses are
      supported for names at this time in DNS and the client may want to
      use the same name for multiple addresses on an interface).

      If the name is not found the client supplied name SHOULD be added
      to the DNS.

      In either condition above the server MUST add the associated DNS
      inverse address mapping as an IP6.INT domain PTR record [IPv6-DNS]
      for this clients address and name.

      If the server returns a name after updating the DNS it MUST return
      a FQDN to the client.

   If the client does not request a HN or FQDN from a server, the server
   MAY provide, in its response with the address to a client, a FQDN the
   client can use for that address.  The server MUST NOT provide a
   client with a server generated FQDN, unless the associated IPv6 AAAA
   record and IP6.INT domain PTR record exists in the DNS.

   When a clients address invalidation-lifetime expires on the server,
   the server SHOULD delete the clients IPv6 AAAA record and IP6.INT
   domain PTR record from the DNS.











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3.6 Defining Optional Configuration-Data

   Optional configuration-data MUST be specified for DHCPv6 as follows
   and aligned on an integer multiple of 8 octets:

      option-type: 1 Octet

      This field permits 254 options for DHCPv6 and will represent the
      tag for the option.  The values of 0 and 1 are used for pad
      options discussed below.

      option-length: 2 Octets

      This field specifies the length of the configuration-data not
      including the the option-type and and option-length fields.

      option-data:  Variable number of Octets

      The option-data is the configuration-data that immediately follows
      the option-length field.

   If the server does not support an option-type requested it MUST
   return the option-type and the option-length set to zero in the
   response to the client.

   A server implementation MUST start any options after the first option
   returned to a client on an integer multiple of 8 octets.  This is an
   architectural REQUIREMENT, and the client when parsing options can
   assume the next option, if it exists will begin on the next integer
   multiple of 8 octets boundary.

   This specification does not define any options.  DHCPv6 options are
   defined in XXXXXXXXX.  It is permissible for options to also create
   new message-types and message-codes as required.


























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4.  Datagram and Data Formats



4.1 Datagram


                           DHCPv6 Datagram

     0               8               16              24              31
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  msg-type     |    msg-code   |   name-lgth   | addr-count    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      transaction-ID                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     interface-token                           |
     |                       (8 Octets)                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       client-address                          |
     |                        (16 Octets)                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       server-address                          |
     |                        (16 Octets)                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       gateway-address                         |
     |                        (16 Octets)                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   client-link-address                         |
     |                        (16 Octets)                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      validation-lifetime                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      deprecation-lifetime                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         host-name                             |
     |                    (variable octets 0-255)                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  option-type  |  option-lgth  | option-data (variable octets) |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



4.2 Data Formats


  All fields in the datagram MUST be initialized to binary zeroes
  by both the client and server messages unless otherwise noted
  in Section 5. Client and Server processing of messages.

  msg-type              : 1  Octet integer value (message-type)

    Value    Description

     1    -  Client request for configuration data.
     2    -  Server response with configuration data.
     3    -  Client confirmation of server response.
     4    -  Client rejection of server response.



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  msg-code              : 1  Octet integer value (message-code)

    Value    Description

     1    -  Server Response - Client address-count is in error.
     2    -  Server Response - Dynamic Updates to DNS not supported.

  name-lgth             : 1  Octet integer value (name-length)

  addr-count            : 1  Octet integer value (address-count)

  transaction-ID        : 4  Octets integer value

  interface-token       : 4  Octets integer value

  client-address        : 16 Octets address

  server-address        : 16 Octets address

  gateway-address       : 16 Octets address

  client-link-address   : 16 Octets address

  validation-lifetime   : 4  Octets integer value

  deprecation-lifetime  : 4  Octets integer value

  host-name             : 0-255 Octets character(s) value(s)

  option-type           : 1  Octet integer value

  option-length         : 1  Octet integer value

  option-data           : Variable Octets variant value(s)


























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5.  Client/Server Processing



5.1 Client Transmission

   UDP DHCPv6 Server Port 546 MUST be used by the client to send UDP
   datagrams to the server.

   If the client knows its address it MUST be put in the source address
   field of the IPv6 Header.  Otherwise the clients link-local address
   MUST be used as the source address field in the IPv6 Header [IPv6-
   ADDRCONF].

   If the client knows the address of the server on its link it MUST put
   that address in the destination address field of the IPv6 Header.
   Otherwise the client MUST put the DHCP Server/Relay-Agent well-known
   multicast address FF02:0:0:0:0:0:1:0 using link-local scope [IPv6-
   ADDR] as the destination address field in the IPv6 Header.

   The client MUST set msg-type to 1 to transmit a request to the
   server.

   The client MUST set msg type to 3 to confirm the acceptance of packet
   from a server response.

   The client MUST set msg type to 4 to reject a packet from a server
   response.

   The client MUST use UDP DHCPv6 Client Port 546 as the UDP port to
   accept server responses in an implementation.




5.2 Server Transmission

   UDP DHCPv6 Client Port 546 MUST be used by the server to send UDP
   datagrams to the client.

   A server, 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 not on the same link are discussed
   in Section 6 Relay-Agent Processing.

   The server MUST set msg type to 2 to transmit a response to a client.

   The server MUST use UDP DHCPv6 Server Port 547 as the UDP port to
   accept client requests in an implementation.

   The server MUST join the DHCP Server/Relay-Agent mulicast group
   well-known multicast address FF02:0:0:0:0:0:1:0 using link-local
   scope [IPv6-ADDR], to listen for client requests, that do not know
   the address of a server on the clients link.






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5.3 Client/Server Bindings

   Client and server bindings MUST be maintained at least as a 4-tuple
   consisting of the clients interface-token, address, validation-
   lifetime, and deprecation-lifetime in an implementaiton.  It is
   critical for the interoperability of DHCPv6 that the clients bindings
   remain consistent with the servers bindings across reboots.

   When a client sends a request it MUST enter in the addr-count field
   the number of addresses that it has for a particular interface-token
   in the clients bindings.

   When the server receives the client request, it MUST verify that the
   addr-count field provided by the client matches the number of
   addresses the server has for that clients binding, for the
   interface-token provided by the client.  If the server has a
   different addr-count than the client for a particular interface
   token, the server MUST send a response to the client setting msg-code
   to 1 informing the client addr-count at the server is not in synch
   with the client.

   Once the client receives a response with a msg-code set to 1 it MUST
   set addr-count to zero on subsequent requests to the server, for that
   interface-token.

   When a server receives a request from a client and the addr-count is
   set to zero, but the client has a binding for that interface-token,
   the server MUST reissue the configuration-data in those bindings to
   the client.



5.4 Client Requests

   The client sets the following fields for a request for
   configuration-data:

      msg-type: Set to 1.

      name-lgth: Set to the length of the host-name if provided.

      addr-count: Set to the number of addresses the client has for the
      interface-token specified in this request.

      transaction-ID: Set to a unqiue integer value.

      interface-token: Set to a unqiue opaque identifier.

      client-address: Set ONLY if the client is requesting a host name
      for a particular address, else not set.

      validation-lifetime: Set to the value the client would like the
      server to use, else not set.

      deprecation-lifetime: Set to the value the client would like the
      server to use, else not set.

      host-name: Set only if name-lgth is greater than zero otherwise


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      this field is not present.

      option-type: Set to a future option request for configuration-
      data, otherwise the field is not present.  Multiple option-types
      may be set adjacent to each other.



5.5 Server Response

   The server sets the following fields for a response to a client for
   configuration-data:

      msg-type: Set to 2.

      msg-code: Set to 1 if addr-count not equal to servers bindings for
      the clients specified interface-token.  Set to 2 if the server
      cannot support Dynamic Updates to DNS because the client requested
      a host-name for an address provided, or from the servers set of
      addresses.

         If the server determines that addr-count is not equal to its
         bindings it stops all other DHCPv6 processing, hence, the
         server would not be in the situation of setting msg-code to
         both 1 and 2.  The server sets msg-code to 1 and MUST put all
         other values supplied by the clients request in the response
         packet except the msg-type and msg-code fields.

         Processing of msg-code set to 1 for the client and server is
         done as specified in 5.3 Client/Server Bindings.

      name-lgth: Set to the length of the host-name if present.

      addr-count: Set to the same value specified by the client.

      transaction-ID: Set to the same value specified by the client.

      interface-token: Set to the same value specified by the client.

      client-address: If the client-address from the request packet is
      zero the server sets the client-address to the next available
      address for this interface-token. If there is a client-address in
      the request packet the client is requesting a host-name for this
      address, and the server MUST return the address provided by the
      client if the server supports Dynmic Updates to DNS, and has
      updated the DNS with a host-name for that address.

      server-address: The server MUST set this field to its address in
      all response packets.

      validation-lifetime:  The server sets this address to the
      validation-lifetime of the servers configuration database. It is
      implementation defined if the server will use the validiation-
      lifetime if specified by a client request packet.

      deprecation-lifetime:  The server sets this address to the
      deprecation-lifetime of the servers configuration database. It is
      implementation defined if the server will use the deprecation-


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      lifetime if specified by a client request packet.

      host-name: The server returns a hostname or msg-code set to 2, if
      the name-lgth field is greater than zero.  Processing of host-name
      is specified in Section 3.5 DNS Host Name Autoregistration Model.

      option-type: The server returns the same option-types specified by
      the client requests.

      option-lgth: The server returns the length of the configuration-
      data or zeroes if the option is not supported.

      option-data: The server returns the configuration-data requested
      by the client.



5.6 Client Confirmations/Rejections

   The client sets the following fields for a confirmation or rejection
   after receiving configuration-data from the server. configuration-
   data:

      msg-type: Set to 3 if the client is confirming a servers response.
      Set to 4 if the client is rejecting a servers response.

         When the server receives a rejection msg-type 4 from a client
         the server MUST assume the client is using another server.  The
         server then MUST remove any bindings for that client it may
         have created, and MUST delete any DNS HN or FQDN records it may
         have added on behalf of the client.

      transaction-ID: Same value as specified in the servers response.

      interface-token: Same value as specified in the servers response.

      client-address: Same value as specified in the servers response.



6.  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 mulicast group
   well-known multicast address FF02:0:0:0:0:0:1:0 using link-local
   scope [IPv6-ADDR], to listen for client requests.

   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 IPv6 address in the gateway-address field
         of the clients request packet.

         Put the the source address from the IPv6 Header of the clients


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         request packet in the client-link-address.

      All relay-agents MUST:

         Put their relay-agent address as the source address for the
         IPv6 Header.

         Put the next relay-agent or known server address as the
         destination address in the IPv6 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 test the gateway-address is not zero, to determine if the
   clients request is from a remote link.

   The server responds as specified in 5.5 Server Response, but uses the
   gateway-address as the destination address in the IPv6 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 IPv6 Header.



































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Draft ***Open Issues***

   1.  The present model uses UDP with a client request, server
   response, and then client confirmation or rejection.  The server will
   set state or remove state based on this model.  There is always the
   possibility of the classic transactional error when the client-to-
   server response is not received by the server, or the client assumes
   the server received the response and it did not (see the draft).

      This can be greatly alleviated by using TCP instead of UDP for the
      transaction.  This would have great benefits such as:

         1.  Guranteed virtual link, hence if the transaction completes
         the server and client know immediately upon return to the
         application.

         2.  PATH MTU Discovery for TCP is inherent in an implementation
         and the DHCPv6 application does not have to adjust for IPv6
         fragmentation model.

   We can also use UDP to locate servers and TCP for the transaction.

   2.  Dynamic Updates to DNS need careful review for clarity and what
   is required for just host name processing in DHCPv6.

   3.  We need to determine the integration required with IPv6 Stateless
   Address Configuration when both stateless and statefull is being used
   by a client host.

   4.  In the Design Goals section should the MUSTs, SHOULDs, etc be
   capitalized and REQUIRED?  Its not in DHCPv4?

   5.  Charlie Perkins will be doing our option spec for DHCPv6. We need
   to make sure it synchs up with this spec.


























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Change History

   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.

      Re-Defined transaction-ID and interface-token.

      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 Configuration.

      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 acroynym 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 Ralph Droms, Thomas Narten, Jack Mccann, and Charlie
   Perkins.   A big warm and extended thanks to Sue Thomson, Yakov
   Rehkter, and Phil Wells, who spent many hours in person and on the
   phone with the author to get the work done.

   Sue Thomson and Yakov Rehkter were co-authors on the first
   specification, and with the author have since March 1994 kept a
   consistent view and belief that autoregistration MUST be part of the
   Next Generation Internet Protocol version 6 and integrated into
   autoconfiguration.

   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 to work
   on DHCPv6 and IPv6 in general.



References

   [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, "IPv6 Stateless Address Configuration"
       Internet Draft, June 1995 <draft-ietf-addrconf-ipv6-auto-02.txt>

   [IPv6-ND]
       T. Narten, E. Nordmark, and W. A. Simpson, "IPv6 Neighbor
   Discovery"
       Internet Draft, June 1995
       <draft-ietf-ipngwg-discovery-00.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



Authors' Addresses

    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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