path: root/doc/draft/draft-park-ipv6-extensions-dns-pnp-00.txt

  
  
  
  INTERNET-DRAFT                                       S. Daniel Park
  Expires: October 2003                              Syam Madanapalli
  File:                                           SAMSUNG Electronics
  draft-park-ipv6-extensions-dns-pnp-00.txt                April 2003
  
  
  
  
                 IPv6 Extensions for DNS Plug and Play
  
  
  
  Status of This Memo   
  
  This document is an Internet-Draft and is in full conformance with
  all provisions of Section 10 of RFC2026.

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

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

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

  The list of Internet-Draft Shadow Directories can be accessed at
  http://www.ietf.org/shadow.html.
  
  
  
  Abstract  
  
  This document proposes automatic configuration of domain name (FQDN)
  for IPv6 nodes using Domain Name Auto-Configuration (called 6DNAC) as
  a part of IPv6 plug and play feature. 6DNAC allows the automatic
  registration of domain name and corresponding IPv6 Addresses with
  the DNS server. In order to provide 6DNAC function, Neighbor Discovery
  Protocol [2461] will be used. Moreover, 6DNAC does not require any
  changes to the existing DNS system.
  
  
  Table of Contents 
  
  1.       Introduction .............................................  3
  2.       Terminology ..............................................  3
  3.       6DNAC Design Principles ..................................  4
  4.       6DNAC Overview ...........................................  4
  5.       6DNAC Requirements .......................................  5
  5.1.     6DANR Client Requirements ................................  5
  5.2.     6DNAC Server Requirements ................................  6
    
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  6.       6DNAC Messages and Option Formats ........................  6
  6.1.     Router Advertisement (RA) Message Format .................  6
  6.2.     Neighbor Solicitation (NS) Message Format ................  7
  6.3.     Neighbor Advertisement (NA) Message Format ...............  8
  6.4.     Option Formats ...........................................  8
  6.4.1.   DNS Zone Suffix Information Option Format ................  8
  6.4.2.   Domain Name (FQDN) Option Format .........................  9
  6.4.3.   Router Alert Option for 6DNAC ............................ 10
  7.       6DNAC Operation .......................................... 10
  7.1.     6DNAC Network Topology ................................... 11
  7.2.     6DNAC Operational Scenarios .............................. 12
  7.2.1.   Domain Name Registration-Success Case .................... 12
  7.2.2.   Domain Name Registration-with DupAddrDetectTransmits=2.... 14
  7.2.3.   Domain Name Registration-Defend Case ..................... 16
  7.2.4.   Domain Name Registration in Retry Mode ................... 19
  7.2.5.   Domain Name Registration when DAD Fails .................. 20
  7.3.     DNS Zone Suffix Discovery and FQDN Construction .......... 22
  7.3.1.   Sending Router Advertisement Messages .................... 22
  7.3.2.   Processing Router Advertisement Messages ................. 22
  7.3.3.   FQDN Lifetime expiry ..................................... 23
  7.3.4.   Host Naming Algorithm .................................... 23
  7.4.     Duplicate Domain Name Detection .......................... 23
  7.4.1.   DAD with All Nodes Multicast Address ..................... 24
  7.4.1.1. Sending Neighbor Solicitation Messages ................... 24
  7.4.1.2. Processing Neighbor Solicitation Messages ................ 24
  7.4.1.3. Sending Neighbor Advertisement Messages .................. 25
  7.4.1.4. Processing Neighbor Advertisement Messages ............... 25
  7.4.1.5. Pros and Cons ............................................ 25
  7.4.2.   DAD with Router Alert Option for 6DNAC ................... 25
  7.4.2.1. Sending Neighbor Solicitation Messages ................... 25
  7.4.2.2. Processing Neighbor Solicitation Messages ................ 26
  7.4.2.3. Sending Neighbor Advertisement Messages .................. 26
  7.4.2.4. Processing Neighbor Advertisement Messages ............... 26
  7.4.2.5. Pros and Cons ............................................ 26
  7.4.3.   Explicit Detection of Duplicate Domain Name .............. 26
  7.4.3.1. Sending Neighbor Solicitation Messages ................... 26
  7.4.3.2. Processing Neighbor Solicitation Messages ................ 26
  7.4.3.3. Sending Neighbor Advertisement Messages .................. 27
  7.4.3.4. Processing Neighbor Advertisement Messages ............... 27
  7.4.3.5. Pros and Cons ............................................ 27
  7.4.4.   Retry Mode for Re-registering Domain Name ................ 27
  7.5.     Domain Name Registration ................................. 27
  8.       Security Consideration ................................... 27
  9.       IANA Consideration ....................................... 28
  10.      Acknowledgement .......................................... 28
  11.      Intellectual Property .................................... 28
  12.      Copyright ................................................ 28
  13.      References ............................................... 29
  14.      Author's Addresses ....................................... 30








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  1. Introduction 
  
  Today, most networks use DNS[1034][1035] for convenience. In case of
  IPv6, DNS is more important element because of IPv6 long addresses
  which are difficult to remember. In addition, small networks like home
  networks using IPv6, should be able to make network easily without
  manual configuration. Also, these small networks may not have DHCP
  Server, DNS Server etc. that are used to configure the network. This
  document discusses IPv6 Domain Name Auto-Configuration(6DNAC) procedure
  for generating and registering the Domain Name and IPv6 addresses with
  the DNS Server automatically. In order to use 6DNAC, IPv6 nodes are
  required to implement lightweight functions specified in this document.
  6DNAC can be applied to all defined IPv6 unicast addresses except Link
  local IPv6 addresses, viz: Site-local and Global addresses.
  
  6DNAC uses Neighbor Discovery Protocol [2461] with new additions
  (defined in section 6) and DAD procedures for generating and 
  registering the Domain Name with the DNS server automatically.
  
  
  2. Terminology

  6DNAC         - IPv6 Domain Name Auto Configuration. It can provide
                  IPv6 hosts with Domain Name Generation and 
                  Registration automatically.
  
  6DNAC Client  - An IPv6 node that can generate its own unique Domain
                  Name. Section 3 identifies the new requirements that
                  6DNAC places on an IPv6 node to be a 6DNAC node.
                  
  6DNAC Server  - An IPv6 node that can collect and registrate Domain
                  Name and IPv6 addresses automatically. 6DNAC server
                  uses the information from the DAD operation messages
                  with newly defined options for the registration of the 
                  Domain Name and IPv6 Addresses. Section 3 identifies
                  the new requirements that 6DNAC places on an IPv6 
                  node to be a 6DNAC server. Also 6DNAC server can have 
                  various other functions depending on network 
                  environment and the network operator. For instance 
                  6DNAC Server can acts as a Gateway as well Home Server
                  in Home Networks.
 
  DAD           - Duplicate Address Detection (is defined [2461]) 
  
  DFQDND        - Duplicate Domain Name Detection

  FQDN          - Fully Qualified Domain Name - FQDN and Domain Name are 
                  used interchangeably in this document.
  
  NA            - Neighbor Advertisement message (is defined [2461]) 
  
  NS            - Neighbor Solicitation message (is defined [2461])

  RA            - Router Advertisement message (is defined [2461]) 

  SLAAC         - Stateless Address Autoconfiguration [2462].

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  3. 6DNAC Design Principles
  
  This section discusses the design principles of 6DNAC mechanism.
  
  1. The new procedures for plug and play DNS should not cause changes
     to existing DNS system. 6DNAC requires lightweight functions to be 
     implemented only at the client side of the DNS system, and uses the 
     existing DDNS UPDATE [2136] to communicate with DNS Servers.
  
  2. Introducing a new protocol will always introduce new problems. 
     6DNAC uses the existing protocols NDP [2461] with minor extensions 
     for generating and registering the domain name automatically 
     without defining a new protocol
  
  3. Reusing proven and well understood design principles/patterns 
     will always yield a robust system. 6DNAC is based on IPv6 Address 
     Auotoconfiguration principle, where routers advertise the prefix
     and host adds the interface ID to the prefix and forms the IPv6 
     address. Domain Name (FQDN) also contains two parts: host name 
     and DNS zone suffix. Routers can advertise the DNS zone suffix 
     on a particular link in Router Advertisements (RA Messages) and 
     hosts can prefix their preferred host name to the DNS zone suffix
     and form the fully qualified domain name. Also the detection of
     duplicate domain name is similar to Duplicate Address Detection
     (DAD) and can be part of DAD operation itself.
  
  
  4. 6DNAC Overview
  
  6DNAC proposes minor extensions to NDP [2461] for automatic generation
  and registration of domain name with the DNS server. It introduces two
  new options: DNS Zone Suffix and Fully Qualified Domain Name. DNS Zone
  Suffix option is carried in Router Advertisement (RA) messages for
  notifying IPv6 nodes about the valid DNS Zone Suffix on the link and
  FQDN option in Neighbor Solicitation (NS) and Neighbor Advertisement
  (NA) messages to detect duplicate domain name. 6DNAC consists of two
  components: 6DNAC Client and 6DNAC Server. 6DNAC Clients generate the
  domain name based on DNS Zone Suffix using Host Naming Algorithm (see
  section 7.3.1) and 6DNAC Server collects and registers the DNS
  information with the DNS Server on behalf of 6DNAC Clients.

  The automatic configuration of domain name using 6DNAC consists of
  three parts.

     - DNS Zone Suffix Discovery and FQDN Construction:

       IPv6 Nodes collect DNS Zone Suffix information from Router
       Advertisements and constructs FQDN by prefixing host name to the
       DNS Zone Suffix. The IPv6 Nodes are required to implement Host 
       Naming Algorithm for generating host part of the FQDN in the 
       absence of administrator.

  Generation of node's FQDN within the node itself has advantages. Nodes
  can provide forward and reverse name lookups independent of the DNS
  System by sending queries directly to IPv6 nodes [NIQ]. Moreover Domain
  Name is some thing that is owned by the node.

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     - Duplicate Domain Name Detection

       All nodes are expected to go for DAD for all new IPv6 unicast
       addresses, regardless of whether they are obtained through 
       stateful, stateless or manual configuration. 6DNAC uses the DAD 
       messages with new option for carrying the Domain Name along with 
       the new IPv6 Address. 6DNAC Server captures this information and
       updates DNS Server provided that the IPv6 Address and its domain
       name are not duplicate. If the domain name is already in use, 
       the 6DNAC server replies to the sender with FQDN Option in NA 
       message indicating that the domain name is duplicate. Then the
       node is expected to generate another domain name using host 
       naming algorithm and go for DAD. This time the DAD is only for
       duplicate domain name detection (DFQDND). In order to avoid
       confusion with the normal NDP processing, the target address 
       field of the NS message must carry the unspecified address 
       in retry mode.  This can be repeated depending on number of
       retries defined by the administrator in the host naming algorithm.

  
     - Domain Name Registration

       6DNAC Server detects the DNS information (IPv6 Address and 
       corresponding FQDN) from DAD/DFQDND messages and updates DNS 
       Server using existing protocol DDNS UPDATE [2136] provided that
       the IPv6 Address and its domain name are not duplicate.
  
  If an IPv6 Address is duplicate, the IPv6 node cannot perform
  stateless address autoconfiguration repeatedly. Unlike IPv6 stateless 
  address autoconfiguration, 6DNAC allows the automatic configuration of
  domain name repeatedly if the domain name is duplicate depending on 
  number of retries defined by the administrator in the host naming 
  algorithm.
  
  
  5. 6DNAC Requirements 
  
  Depending on the 6DNAC functionality, the IPv6 nodes implement, they
  are called either 6DNAC Clients or 6DNAC Servers. The following 
  sections lists the requirements that the 6DNAC Client and 6DNAC server
  must support.
   
   
  5.1. 6DANC Client Requirements
  
        - 6DNAC Client must recognize and process the following NDP 
          extensions

              - DNS Zone Suffix option in RA messages for generating its
                domain name (FQDN).

              - Domain Name option in NS and NA messages for detecting 
                the duplicate domain name
 
 
 

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        - It must generate its domain name (FQDN) based on the DNS 
          suffix that it got from the router advertisement. And it must 
          have a host naming algorithm for generating the host part of
          the FQDN.

        - If NA message is received with unspecified target address and
          FQDN option, then the node must treat that the domain is 
          duplicate.
  
  
  5.2. 6DNAC Server Requirements
  
        - 6DNAC Server must recognize and process the following NDP
          extensions
      
              - If the 6DNAC Server is a router on the link, then it
                must advertise DNS Zone Suffix option in RA messages
                for hosts to generate their domain name (FQDN).

              - FQDN option in NS messages for detecting new DNS
                information for of nodes on the link for which it
                must update the AAAA RR and PTR RR in DNS Server.

              - FQDN option in NA messages for notifying duplicate
                domain name with unspecified target address.
  
        - 6DNAC server must update the DNS Server (both AAAA RR and
          PTR RR) dynamically using DDNS UPDATE [2136].
  
        - 6DNAC server must cache this (newly detected) FQDN, Link
          Layer Address, and IPv6 Address information, so that it can
          decide whether it really needs to update DNS Server or not,
          to avoid redundant updates. This information will also be
          used for notifying the duplicate domain name.
  
  
  6. 6DNAC Messages and Option Formats
  
  In order to achieve the plug and play DNS, 6DNAC proposes new 
  extensions to the NDP [2461]. This section specifies the new
  additions to NDP messages and formats of new options.
  
  
  6.1. Router Advertisement (RA) Message Format
  
  Routers send out Router Advertisement (RA) message periodically, or
  in response to a Router Solicitation. 6DNAC does not modify the format
  of the RA message, but proposes new option (DNS Zone Suffix Information)
  to be carried in RA messages.








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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Cur Hop Limit |M|O|  Reserved |       Router Lifetime         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Reachable Time                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Retrans Timer                        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Options ...                                                 |
     /                                                               /
     |                  DNS Zone Suffix Information                  |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
  
                          <Figure: 1 RA message>
  
  
  
  6.2. Neighbor Solicitation (NS) Message Format 
  
  6DNAC does not modify the format of the Neighbor Solicitation (NS)
  message, but proposes new option (FQDN Option) to be carried in NS
  messages. When a node is going for DAD, the node must include FQDN
  option in NS message to participate in plug and play DNS. If the
  node is going for Explicit Detection of Duplicate Domain Name, the
  node must use FQDN option in NS message and unspecified address in
  the target address field.
  
  
      0                   1                   2                   3 
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Reserved                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                       Target Address                          +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Options ...                                                 |
     /                                                               /
     |                         Domain Name                           |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
  
                         <Figure: 2 NS message>
  
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  6.3. Neighbor Advertisement (NA) Message Format 
  
  6DNAC does not modify the format of the Neighbor Advertisement (NA)
  message, but proposes new option (FQDN Option) to be carried in NA
  messages. 6DNAC Server sends NA message with FQDN option to 6DNAC
  Client that is performing duplicate domain name detection in case
  the domain name found to be duplicate.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |     Code      |          Checksum             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |R|S|O|                     Reserved                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                       Target Address                          +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Options ...                                                 |
     /                                                               /
     |                         FQDN Option                           |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
  
                          <Figure: 3 NA message> 
  
  
  6.4 Option Formats
  
  6.4.1. DNS Zone Suffix Information Option Format
  
  IPv6 nodes require DNS Zone Suffix for constructing their FQDN.
  6DNAC introduces new option for routers to advertise the DNS Zone
  Suffix Information for IPv6 nodes on the link. The suffix information
  should be configured into routers manually.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |          Reserved             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Valid Lifetime                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     /                       DNS Zone Suffix                         /
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
  
                   <Figure: 4 DNS Zone Suffix Information>

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  Type              [TBD]
  
  Length            8-bit unsigned integer. The length of the option
                    (including the type and length fields) in units of
                    8 octets.
  
  Reserved          This field is unused. It must be initialized to zero
                    by the sender and must be ignored by the receiver.
  
  Valid Life Time   32-bit signed integer.  The maximum time, in 
                    seconds, over which this suffix is valid. Nodes 
                    should treat this as the life time for their domain
                    name. Nodes should contact the source of this
                    information before expiry of this time interval.
                    A value of all one bits (0xFFFFFFFF) represents
                    infinity.
  
  DNS Zone Suffix   The suffix part of the FQDN. The data in the DNS 
                    Zone Suffix field should be encoded according to 
                    DNS encoding rules specified in [1035].
  
  
  
  6.4.2. Domain Name (FQDN) Option Format
  
  
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |          Reserved             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Valid Lifetime                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                                                               |
     +                       FQDN Target Address                     +
     |                                                               |
     +                                                               +
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     /                         Domain Name                           /
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  
  
                      <Figure: 5 FQDN Information>
  
  Type                 [TBD]
  
  Length               8-bit unsigned integer. The length of the option
                       (including the type and length fields) in units 
                       of 8 octets.  It must be greater than 3.
                       
                       

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  Reserved             This field is unused. It must be initialized to
                       zero by the sender and must be ignored by the
                       receiver.
  
  Valid Life Time      32-bit signed integer.  The maximum time, in 
                       seconds, over which this domain name is valid
                       6DNAC should deregister this domain name at
                       the expiry of this interval. 6DNAC clients
                       should send updates by the expiry of this 
                       interval. A value of all one bits (0xFFFFFFFF)
                       represents infinity.

  FQDN Target Address  The Address for which the FQDN maps to.  It 
                       should be same as Target Address field of the 
                       NS message in case of DAD & duplicate FQDN are
                       running in parallel.

  Domain Name          The domain name (FQDN) of the node. The data in
                       the domain name should be encoded according to
                       DNS encoding rules specified in [1035].
  
  
  6.4.3. Router Alert Option for 6DNAC

  Router Alert Option for 6DNAC is new option within the IPv6 Hop-by-Hop
  Header for using in NDP messages.  The presence of this option in NS
  message informs the router that this NS message is carrying Domain
  Name information and must be processed by the 6DNAC Server on the router.
  6DNAC Clients can use this option for sending DAD packets instead
  of addressing the DAD packets to the all-nodes multicast address
  when 6DNAC Server is implemented on router.
 
  The Router Alert option has the following format:

  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |0 0 0|0 0 1 0 1|0 0 0 0 0 0 1 0|        Value (2 octets)       |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Length = 2

  Values are registered and maintained by the IANA. For 6DNAC, the 
  value has to be assigned by IANA.

  Further information about this option can be obtained from 
  IPv6 Router Alert Option [2711].


  7. 6DNAC Operation
  
  6DNAC provides mechanisms for automatic generation of domain name
  and registering it with the DNS Server for IPv6 nodes. 6DNAC consists
  of two components: 6DNAC Client and 6DNAC Server. All nodes that want
  to participate in plug and play DNS are required to implement 6DNAC
  Client functionality, and one of the IPv6 nodes is required to 
  implement 6DNAC Server functionality. The IPv6 node that implements 
  the 6DNAC Server functionality must know the location of the DNS 
  Server and must be a trusted node to send DDNS UPDATE [2136] messages.

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  7.1. 6DNAC Network Topology
  
  This section identifies the possible locations for the 6DNAC Server.
  Note that, all nodes are required to implement 6DNAC Client 
  functionality for constructing the domain name from the DNS Zone 
  Suffix Information advertised by the router.  Figure 6 illustrates 
  IPv6 host (H4) implementing 6DNAC Server functionality. In this case 
  H4 can serve only one link (that it belongs to) for automatic 
  registration of domain name. H4 must observe the DAD packets on the 
  link to detect the DNS information, this requires all nodes on the 
  link must belong to same solicited node multicast address. In general,
  this may not be the case. So the node that is going for DAD must use
  all nodes multicast address for DAD packets, so that the 6DNAC Server
  (H4) can observe the DAD packets, detects IPv6 address and 
  corresponding domain name, checks if this domain name is duplicate 
  and finally registers the domain name with the DNS Server.
 
  
                          6DNAC Server
      +---+                   +---+                     +----------+
      | H1|                   | H4|<--- DDNS UPDATE --->|DNS Server|
      +-+-+                   +-+-+                     +----+-----+
        |                       |           +----+       +---/
        |                       |           |    |      /
     ---+-----+-----------+-----+-----------+ R1 +-----+
              |           |                 |    |
              |           |                 +----+
            +-+-+       +-+-+
            | H2|       | H3|
            +---+       +---+
  
  
  H1, H2, H3 - 6DNAC Clients
  H4         - 6DNAC Server
  R1         - Router
  
  
                  <Figure: 6 Example of 6DNAC Topology>
  
  
  Figure 7 shows the 6DNAC Server implemented on a router R1. In this
  case a single 6DNAC server can serve multiple links for automatic
  configuration of the domain name. This topology also has flexibility
  of using DAD packets with Router Alert option instead of sending DAD
  packets to all nodes multicast address. The routers are required to
  process all the packets with Router Alert option as per [2711].

  In case of Home Networks, R1 is will acts as a Home Gateway (CPE)
  connected to ISP. R1 delegates the prefix from the ISP edge router.
  After delegating the prefix the CPE can advertise the DNS Zone suffix
  along with the prefix information to the nodes on the links to which
  the router is connected to. Note that the R1 must be configured with
  the DNS Zone suffix Information manually. 




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                         +---+       +---+ 
                         | H3+       | H4|
                         +-+-+       +-+-+
                           |           |
                           |   LINK2   |
      +---+             ---+--------+--+--          +----------+
      | H1|                         |               |DNS Server|
      +-+-+                         |               +----+-----+
        |                        +--+-+           -------/
        |         LINK 1         |    |          /
     ---+-----+------------------+ R1 +---------+
              |                  |    |      DDNS UPDATE
              |                  +----+
            +-+-+             6DNAC Server
            | H2|
            +---+
  
  
  H1, H2 - 6DNAC Clients on Link1
  H3, H4 - 6DNAC Clients on Link2
  R1     - Router with 6DNAC Server, serving both Link1 and Link2
  
  
       <Figure: 7 Example of 6DNAC Server serving multiple links>
  
  
  7.2. 6DNAC Operational Scenarios
  
  This section provides message sequence charts for various 6DNAC
  operational scenarios assuming that the 6DNAC Server is implemented
  on a router. All the scenarios assume that the normal boot up time
  stateless address autoconfiguration of Link Local address derived
  from the Interface Identifier has been completed successfully. And
  it is also assumed that the router is already configured with the
  DNS Zone Suffix Information.

  
  Legend:
  
  6DNAC-A, B, C  : 6DNAC Clients
  6DNAC-S        : 6DNAC Server/Router
  DAD            : Duplicate Address Detection
  DFQDND         : Duplicate Domain Name Detection
  DNS-S          : DNS Server
  
  
  7.2.1. Domain Name Registration-Successful Case 

  This scenario starts when a 6DNAC Client receives RA message with
  DNS Zone Suffix and other parameters including address prefix as
  specified in NDP [2461] and wants configure its IPv6 address (Global
  or Site Local) and domain name. It is Assumed that the 
  DupAddrDetectTransmits is set to 1.




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   +---------+      +---------+      +---------+
   | 6DNAC-C |      | 6DNAC-S |      |  DNS-S  |
   +----+----+      +----+----+      +----+----+
        |                |                |
        |     RA with    |                |
        | DNS Suffix Opt |                |
        |<---------------|                |
        |       #1       |                |
        |---+            |                |
  Construct |#2          |                |
    FQDN    |            |                |
        |<--+            |                |
DAD/DFQDND Starts        |                |
        |                |                |
        |                |                |
        |    NS With     |                |
        |    FQDN Opt    |                |
        |--------------->|                |
        |       #3       |                |
        |                |                |
        |                |------+         |
        |          Create FQDN  | #4      |
        |            <FQDN,C>   |         |
        |                |<-----+         |
        |                |                |
        |                |  Register FQDN |
        |                |--------------->|
        |                |       #5       |
        |   #6           |                |
        |--------+       |                |
   No Response   |       |                |
  DFQDND-Success |       |                |
        |<-------+       |                |
        |                |                |
        |                |                |
        v                V                v  


          <Figure: 8 Domain Name Generation and Registration>
           
  
  #1. 6DNAC Server (Router) sends out router advertisement with DNS
      Suffix information along with other parameters as specified in
      NDP [2461].
  
  #2. 6DNAC Client processes the router advertisement and constructs
      the FQDN by prefixing hostname to the DNS Zone Suffix. It also
      constructs IPv6 address from the autoconfiguration prefix
      information option.

  #3. 6DNAC Client starts duplicate address & FQDN detection for the
      IPv6 address & FQDN constructed and sends out a Neighbor
      Solicitation message with FQDN option. 

      Note that the DAD packets must be addressed to all nodes multicast
      address if Router Alert option is not used. 
      
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  #4. 6DNAC Server processes the Neighbor Solicitation message sent by
      6DNAC Client as part of duplicate FQDN detection procedure and
      creates a FQDN entry in its FQDN Cache (assuming that there is no
      entry <FQDN,C>), where C is Link Layer Address of the 6DNAC Client.

  #5.  6DNAC Server then registers FQDN and corresponding IPv6 address
       through the existing protocol DDNS UPDATE.

  #6.  6DNAC Client times out and observes that there is no response to
       defend its duplicate FQDN detection procedure and the node is
       successful in configuring its domain name.
  
  Note that, Stateless Address Autoconfiguration DAD procedure is not
  depicted in the following message sequence chart, which simultaneously
  happens along with duplicate FQDN detection.
  

  7.2.2. Domain Name Registration-with DupAddrDetectTransmits=2 

  This scenario starts when a 6DNAC Client receives RA message with
  DNS Zone Suffix and other parameters including address prefix as
  specified in NDP [2461] and wants configure its IPv6 address (Global
  or Site Local) and domain name. The node is configured with 
  DupAddrDetectTransmits = 2 for reliability in delivering DAD messages.

































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   +---------+      +---------+      +---------+
   | 6DNAC-C |      | 6DNAC-S |      |  DNS-S  |
   +----+----+      +----+----+      +----+----+
        |                |                |
        |     RA with    |                |
        | DNS Suffix Opt |                |
        |<---------------|                |
        |       #1       |                |
        |---+            |                |
  Construct |#2          |                |
    FQDN    |            |                |
        |<--+            |                |
DAD/DFQDND Starts        |                |
        |                |                |
        |                |                |
        |    NS With     |                |
        |    FQDN Opt    |                |
        |--------------->|                |
        |       #3       |                |
        |                |                |
        |                |------+         |
        |          Create FQDN  | #4      |
        |            <FQDN,C>   |         |
        |                |<-----+         |
        |                |                |
        |                |  Register FQDN |
        |                |--------------->|
        |                |       #5       |
        |    NS With     |                |
        |    FQDN Opt    |                |
        |--------------->|                |
        |      #6        |                |
        |                |                |
        |          Lookup FQDN            |
        |          Entry exists           |
        |                |------+         |
        |             Ignore    | #7      |
        |                |<-----+         |
        |   #8           |                |
        |--------+       |                |
   No Response   |       |                |
  DFQDND-Success |       |                |
        |<-------+       |                |
        |                |                |
        |                |                |
        v                V                v  

  
  
            <Figure: 9 Verification of duplicated Domain Name>


  Steps from #1 to #5 are same as that of scenario.7.2.1.
  
  #6. 6DNAC Client sends out second Neighbor Solicitation message with
      FQDN option as part of duplicate FQDN detection.
      
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  #7. 6DNAC Server receives and observes that the FQDN Cache exactly
      matches with that of the NS information and ignores the NS message.

  #8. 6DNAC Client times out and observes that there is no response to
      defend its duplicate FQDN detection procedure and the node is
      successful in configuring its domain name..

  
  7.2.3. Domain Name Registration-Defend Case 

  This scenario starts when two 6DNAC Client receive RA message with
  DNS Zone Suffix and other parameters including address prefix as
  specified in NDP [2461] and both the nodes want configure their IPv6
  address (Global or Site Local) and domain name. In this scenario both
  the nodes want to have same domain name.










































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   +---------+      +---------+      +---------+      +---------+
   | 6DNAC-A |      | 6DNAC-S |      | 6DNAC-B |      |  DNS-S  |
   +----+----+      +----+----+      +----+----+      +----+----+
        |                |                |                |
        |     RA with    |     RA with    |                |
        | DNS Suffix Opt | DNS Suffix Opt |                |
        |<---------------|--------------->|                |
        |       #1       |       #1       |                |
        |---+            |                |---+            |
  Construct | #2         |          Construct | #2         |
      FQDN  |            |              FQDN  |            |
        |<--+            |                |<--+            |
 DAD/DFQDND Starts       |         DAD/DFQDND Starts       |
        |                |            <DELAYED>            |
        |                |                |                |
        |    NS with     |                |                |
        |    FQDN Opt    |                |                |
        |--------------->|                |                |
        |      #3        |                |                |
        |            No Entry             |                |
        |                |------+         |                |
        |          Create FQDN  | #4      |                |
        |            <FQDN,A>   |         |                |
        |                |<-----+         |                |
        |                |                |                |
        |                |         Register FQDN #5        |
        |                |-------------------------------->|
        |                |                |                |
        |                |    NS with     |                |
        |                |    FQDN Opt    |                |
        |                |<---------------|                |
        |                |       #6       |                |
        |                |------+         |                |
        |         FQDN is in use|         |                |
        |          Defend DFQDND| #7      |                |
        |                |<-----+         |                |
        |                |                |                |
        |                |    NA with     |                |
        |                |    D-flag Set  |                |
        |                |--------------->|                |
        |                |       #8       |                |
        |------+         |                |---+            |
 No Response   | #9      |            Enter   | #10        |
 DFQDND Success|         |          Retry Mode|            |
        |<-----+         |                |<--+            |
        |                |                |                |
        v                v                v                v

         
       <Figure: 10 Multiple Hosts Requesting Same Domain Name>





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  #1. 6DNAC Server (Router) sends out router advertisement with DNS
      Suffix information.
      
  #2. 6DNAC Clients A&B process the router advertisement and construct
      their FQDN by prefixing hostname to the DNS Zone Suffix.  They
      also construct IPv6 address from the autoconfiguration prefix
      information option.
      
      When each host is trying to go for DAD, all hosts must have
      random delay to avoid the traffic congestion according to [2461].
      So here it is assumed that 6DNAC Client-A starts DAD first and
      6DNAC Client-B starts DAD later.

  #3. 6DNAC Client-A starts duplicate address & FQDN detection for the
      IPv6 address & FQDN constructed and sends out a Neighbor
      Solicitation message with FQDN option.
   
  #4. 6DNAC Server processes the Neighbor Solicitation message sent by
      6DNAC Client-A as part of duplicate FQDN detection procedure and
      creates a FQDN entry in its FQDN Cache (assuming that there is no
      entry <FQDN,A>), where A is Link Layer Address of the 6DNAC Client-A.

  #5. 6DNAC Server then registers FQDN and corresponding IPv6 address
      through the existing protocol DDNS UPDATE.

  #6. 6DNAC Client-B starts duplicate address & FQDN detection for the
      IPv6 address & FQDN constructed and sends out a Neighbor Solicitation
      message with FQDN option. 

  #7. 6DNAC Server processes the Neighbor Solicitation message sent by
      6DNAC Client-B as part of duplicate FQDN detection procedure and 
      finds that the domain name is already in use by the 6DNAC Client-A.
      Hence, concludes to defend the duplicate FQDN detection of 6DNAC
      Client-B.

  #8. 6DNAC Server sends out Neighbor Advertisement message with FQDN
      option to 6DNAC Client-B to defend its duplicate FQDN detection.

  #9. 6DNAC Client-A times out and observes that there is no response to
      defend its duplicate FQDN detection procedure and the node is 
      successful in configuring its domain name.

  #10. 6DNAC Client-B observes that there is a NA with FQDN option
       indicating that the domain name is duplicate and enters Retry
       Mode. In retry mode, 6DNAC Client constructs another FQDN based
       on Host Naming Algorithm. The number of retries is defined by the
       administrator and must be a configurable value.
  









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  7.2.4. Domain Name Registration in Retry Mode

  Pre-Conditions:

  1. Duplicate Address Detection has succeeded 
  2. Duplicate FQDN Detection FAILED
  3. FQDN is the first FQDN one constructed and FAILED
  4. FQDN2 is the second FQDN to be constructed
  5. The Neighbor Solicitation in the 'Retry Mode'
    carries unspecified address in its target field (NS*).

   +---------+      +---------+      +---------+
   | 6DNAC-C |      | 6DNAC-S |      |  DNS-S  |
   +----+----+      +----+----+      +----+----+
        |                |                |
        |--------+       |                |
    Construct    | #1    |                |
    new FQDN2    |       |                |
        |<-------+       |                |
        |                |                |
  DFQDND Restarts        |                |
        |                |                |
        |                |                |
        |    NS* With    |                |
        |    FQDN Opt    |                |
        |--------------->|                |
        |       #2       |                |
        |                |                |
        |            No Entry             |
        |                |------+         |
        |          Create FQDN  | #3      |
        |            <FQDN2,C>  |         |
        |                |<-----+         |
        |                |                |
        |                | Register FQDN2 |
        |                |--------------->|
        |                |       #4       |
        |                |                |
        |--------+       |                |
   No Response   | #5    |                |
  DFQDND-Success |       |                |
        |<-------+       |                |
        |                |                |
        v                V                v

                
                <Figure: 11 Regeneration of Domain Name>
                









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  #1. 6DNAC Client constructs the FQDN again as per Host Naming Algorithm,
      the DNS Zone Suffix, and it is FQDN2.
  #2. It then starts Duplicate Detection only for Domain Name. 6DNAC
      Client sends out NS with FQDN option and unspecified target
      address.

  #3. 6DNAC Server processes the Retry Mode NS message and finds that
      the FQDN2 is not in use and creates Cache entry as <FQDN2, C>.

  #4. It then starts registration procedures with the DNS Server.

  #5. Meanwhile, 6DNAC Client timesout and observes that there is no
      defending NA for its DFQDND NS sent out and successfully
      configures its domain name.


  7.2.5. Domain Name Registration when DAD Fails

  Duplicate domain name detection and subsequent registration starts 
  if and only if the DAD for IPv6 address succeeds. If the DAD for
  IPv6 address fails then no actions are taken for domain name. When
  DAD fails for stateless address autoconfiguration, then the domain
  configuration starts only when the address has been configured using 
  Stateful Address Configuration methods and the node is going on DAD
  for this address.

  This scenario starts when a 6DNAC Client receives RA message with
  DNS Zone Suffix and other parameters including address prefix as
  specified in NDP [2461] and wants configure its IPv6 address (Global
  or Site Local) and domain name.



























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   +---------+      +---------+      +---------+      +---------+
   | 6DNAC-A |      | 6DNAC-S |      | 6DNAC-B |      |  DNS-S  |
   +----+----+      +----+----+      +----+----+      +----+----+
        |                |                |                |
        |                |                |                |
        |     RA with    |                |                |
        | DNS Suffix Opt |                |                |
        |<---------------|                |                |
        |       #1       |                |                |
        |-----+          |                |                |
    Construct |          |                |                |
      FQDN&   | #2       |                |                |
    IPv6 Addr |          |                |                |
        |<----+          |                |                |
 DAD/DFQDND Starts       |                |                |
        |                |                |                |
        |                |                |                |
        |    NS with     |                |                |
        |    FQDN Opt    |                |                |
        |--------------->+--------------->|                |
        |       #3       |        #3      |                |
        |            No Entry             |                |
        |                |------+         |                |
        |          Create FQDN  |         |                |
        |            <FQDN,A>   | #4      |                |
        |                |<-----+         |                |
        |                |                |                |
        |                |                |------+         |
        |                |           My IPv6 Addr| #5      |
        |                |                |<-----+         |
        |                |   Defend DAD   |                |
        |                |    with NA     |                |
        |<---------------+<---------------|                |
        |      #6        |       #6       |                |
        |              Entry              |                |
        |                |------+         |                |
        |          Delete FQDN  | #7      |                |
        |                |<-----+         |                |
        |                |                |                |
        |----+           |                |                |
  DAD Failed | #8        |                |                |
 Stop DFQDND |           |                |                |
        |<---+           |                |                |
        |                |                |                |
        v                v                v                v

                     <Figure: 12 DAD failure>

  #1. 6DNAC Server sends out Router Advertisement to 6DNAC Client-A.

  #2. 6DNAC Client-A constructs IPv6 Address based on the prefix and
      FQDN as per Host Naming Algorithm. 

  #3. It then starts Duplicate address & FQDN Detection, for the newly 
      constructed IPv6 address and FQDN, and sends out DAD/DFQDND NS
      with FQDN option.  

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  #4. 6DNAC Server processes the DAD/DFQDND NS message and finds 
      that there is no entry for the FQDN in its cache. And,
      creates Cache entry as <FQDN, A> and starts a Registration
      timer with RegistrationWaitTime seconds.

  #5. 6DNAC Client-B finds that the DAD/DFQDND-NS target address is 
      in its unicast address list.  

  #6. It then starts defending DAD by sending NA to all-nodes multicast.

  #7. 6DNAC Server finds that the DAD has failed for 6DNAC Client-A.  
      And, deletes its FQDN Cache entry <FQDN,A>.
      
  #8. 6DNAC Client gets defending DAD-NA and desists from DAD. 
      And also, stops Duplicate FQDN Detection as well.
      At this point the address must be configured using stateful 
      methods and the domain name registration starts with the DAD
      for the newly constructed IPv6 address.
  
  7.3. DNS Zone Suffix Discovery and FQDN Construction
  
  7.3.1. Sending Router Advertisement Messages

  Routers send out Router Advertisement message periodically, 
  or in response to a Router Solicitation. Router should include 
  the DNS Zone Suffix Option in their advertisements. If the DNS
  Zone Suffix changes (similar to Site Renumbering), then it should
  advertise the Old Zone Suffix with zero Valid Lifetime and New
  Zone Suffix with proper non-zero Valid Lifetime.  In any other
  case, a router should not send this option twice in a single
  router advertisement.

  7.3.2. Processing Router Advertisement Messages  

  For each DNS Zone Suffix Option in Router Advertisement,

  a. 6DNAC node stores the Zone Suffix information in its local
     database.  Also, constructs FQDN as per Host Naming Algorithm.

  b. If the node has not configured FQDN yet,

     1. If the node is going to perform DAD for either Site local or 
        Global Address, then it should include FQDN option to perform
        Duplicate FQDN Detection in parallel with DAD.

     2. If the node has already got either Site local or Global 
        address, then it should send out NS with FQDN option and 
        unspecified target address to perform Duplicate FQDN 
        Detection.

  c. If the node has already configured FQDN, and if the 
     advertisement carries two DNS Zone Suffix Options,
     First DNS Zone Suffix should match with the configured FQDN 
     Suffix and its Valid Lifetime must be zero. Second DNS Zone



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     Suffix should have non-zero Valid Lifetime. In this case, the
     node constructs new FQDN based on the new DNS Zone Suffix (from
     second DNS Zone Suffix option), and perform Duplicate FQDN 
     Detection with unspecified target address.  Also, it should
     overwrite the old FQDN with the newly constructed FQDN.
     

  7.3.3. FQDN Lifetime expiry

  6DNAC Server:  
  It should delete the FQDN cache entry and should de-register from
  the DNS Server.

  6DNAC Client:
  It should send update to 6DNAC Server by restarting the Duplicate 
  FQDN Detection. 
  
  7.3.4. Host Naming Algorithm
 
  A node constructs FQDN by combining DNS Zone Suffix and the hostname
  as depicted in the following diagram.

     +------------------+----------------------------------+
     |     Host Name    |          Advertised Suffix       |
     +------------------+----------------------------------+

          <Figure 13: Fully Qualified Domain Name format>

  A node can choose Host Name using any of the following methods:
 
  a. String form of random number generated from the Interface 
     Identifier.
     
  b. List of configured Host Names provided by the administrator.

  
  The number of retries must be specified in this algorithm in 
  case of domain name duplication.
  
    
  7.4. Duplicate Domain Name Detection
  
  The procedure for detecting duplicated FQDNs uses Neighbor
  Solicitation and Advertisement messages as described below.

  If a duplicate FQDN is detected during the procedure, the
  FQDN cannot be assigned to the node.

  An FQDN on which the DFQDND Procedure is applied is said 
  to be tentative until the procedure has completed successfully.  
  A tentative FQDN is not considered "assigned to the node" in the 
  traditional sense.  That is, the node must accept Neighbor 
  Advertisement message containing the tentative FQDN in the FQDN 
  Option.


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  It should also be noted that DFQDN must be performed prior to 
  registering with DNS Server to prevent multiple nodes from using 
  the same FQDN simultaneously. All the Duplicate Address Detection 
  Neighbor Solicitation messages must carry Source Link Layer Address 
  Option as specified in NDP [2461]. 

  The detection of duplicate FQDN can be achieved through one of the
  following three types of procedures.
  
  1. DAD with All Nodes Multicast Address
  2. DAD with Router Alert Option for 6DNAC.
  3. Explicit Detection of Duplicate Domain Name
   
  Even though three solutions are listed, authors prefer only one 
  procedure to be followed in future based on further analysis and
  comments received from others. 
  
  7.4.1. DAD with All Nodes Multicast Address
  
  7.4.1.1. Sending Neighbor Solicitation Messages

  6DNAC Client sends Neighbor Solicitation Messages as part
  of Duplicate Address Detection SLAAC [2462] with the following 
  extra information and modifications:

  a. Include FQDN Option in the DAD Neighbor Solicitation Message
  b. Destination Address is set to All Nodes Multicast Address

  There may be a case where DAD has succeeded but DFQDND is in Retry 
  Mode. In such case, the Neighbor Solicitation must carry unspecified 
  address in the ICMP target address field and new domain name in FQDN
  option to re-try the registration of the domain name.

  7.4.1.2. Processing Neighbor Solicitation Messages

  6DNAC Clients must ignore the FQDN option found in any of the
  neighbor solicitation messages.

  6DNAC Server processes FQDN Option found in the Duplicate Address 
  Detection Neighbor Solicitation Messages as described below:

  Lookup FQDN Cache for the domain name in FQDN Option.

  If the entry exists and 
   i. Link Layer Address matches with SLLA option, this is the case, 
      where node has changed its IPv6 address or updating the valid 
      life time. 6DNAC Server updates its cache and also updates DNS
      Server using DDNS-UPDATE. If there is no change in IPv6 address
      or life time then no updates are sent to the DNS server. 

  ii. Link Layer Address differs with SLLA option, defend the duplicate 
      FQDN Detection by sending Neighbor Advertisement Message as 
      described in $7.4.1.3$.



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  else,
    Lookup FQDN Cache for the Link Layer Address in SLLA Option.

    If the entry exists, update the FQDN Cache and update DNS Server 
    using DDNS-UPDATE. This is the case, where node has changed its
    domain name (similar to Site Re-numbering).

    If then entry does not exists, then it means that this is the new 
    registration. It must create a cache entry and start Registration    
    
    timer with RegistrationWaitTime. At the expiry of the Registration
    timer, it should update DNS Server with DDNS-UPDATE.

  7.4.1.3. Sending Neighbor Advertisement Messages

  6DNAC Server sends Neighbor Advertisement Messages as part
  of Duplicate Address Detection SLAAC [2462] with the FQDN Option 
  in Neighbor Advertisement message to defend duplicate FQDN 
  detection.

  There may be the case where defending of duplicate address detection 
  is not required but defending of FQDN is required.  In such instance, 
  the defending Neighbor Advertisement must carry FQDN and unspecified
  address in the ICMP target address field.

  7.4.1.4. Processing Neighbor Advertisement Messages

  6DNAC Server must ignore the any FQDN option found any of 
  the neighbor advertisement messages.  If the Neighbor Advertisement
  is a DAD defending, then it must delete its FQDN Cache entry created 
  on the reception of DAD Neighbor Solicitation message.

  When 6DNAC Clients gets the duplicate address detection neighbor
  advertisement messages with FQDN option set it means that its
  duplicate FQDN detection failed and enters Retry Mode.

  7.4.1.5. Pros and Cons
  
  The advantage of this procedure is that it does not need any 
  extension header options to be included. The disadvantage of this 
  procedure is that, it needs change in the existing DAD procedure.
  The change is only that the DAD neighbor solicitations are to be 
  addressed to all nodes multicast address instead of solicited 
  node multicast address. The another disadvantage is that, it needs 
  the existence of Duplicate Address Detection Procedure to 
  perform duplicate FQDN detection. 
  
  7.4.2. DAD with Router Alert Option for 6DNAC

  7.4.2.1. Sending Neighbor Solicitation Messages

  6DNAC Client sends Neighbor Solicitation Messages as part
  of Duplicate Address Detection SLAAC [2462] with the following 
  extra information:


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  a. Include Hop-by-Hop extension Header with Router Alert Option
     for 6DNAC as described in IPv6 Router Alert Option[2711].

  b. Include FQDN Option in the DAD Neighbor Solicitation Message

  7.4.2.2. Processing Neighbor Solicitation Messages

  This is same as described in $7.4.1.2$. 

  7.4.2.3. Sending Neighbor Advertisement Messages

  This is same as described in $7.4.1.3$. 

  7.4.2.4. Processing Neighbor Advertisement Messages

  This is same as described in $7.4.1.4$.

  7.4.2.5. Pros and Cons

  The advantage of this procedure is that it does not disturb
  the existing implementation and their way of processing the 
  packets.  The disadvantage is that, it needs the existence 
  of Duplicate Address Detection Procedure to perform duplicate 
  FQDN detection. Another disadvantage is that this procedure 
  requires 6DNAC Server functionality to be implemented on Router.
  However, in this case 6DNAC Server can serve multiple links.
  
  7.4.3. Explicit Detection of Duplicate Domain Name

  In this procedure Duplicate FQDN Detection starts after completion
  of successful Site local or Global Address configuration.
  
  7.4.3.1. Sending Neighbor Solicitation Messages

  6DNAC Client sends Neighbor Solicitation Messages as part
  of Duplicate FQDN Detection with the following information:

  a. Include FQDN Option in the Neighbor Solicitation Message

  b. Destination Address is set to All Nodes Multicast Address
     or uses Router Alert Option for 6DNAC, when 6DNAC Server is 
     implemented on router.

  c. Target Address is set to Unspecified Address

  d. Other fields are set as per DAD SLAAC [2462].

  7.4.3.2. Processing Neighbor Solicitation Messages

  This is same as described in $7.4.1.2$.






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  7.4.3.3. Sending Neighbor Advertisement Messages

  This is same as described in $7.4.1.3$.

  7.4.3.4. Processing Neighbor Advertisement Messages

  This is same as described in $7.4.1.4$.

  7.4.3.5. Pros and Cons

  The advantage of this procedure is that it does not need the
  existing duplicate address detection procedure.  This is introduced
  as the DAD procedure is found to be redundant in when IPv6 addresses
  are constructed from the interface ID [DIID].

  Note that, if 6DNAC Clients know the address of 6DNAC Server then
  they can directly send DFQDND-NS to 6DNAC Server. 

  7.4.4. Retry Mode for Re-registering Domain Name

  In retry mode, nodes construct new FQDN as per Host Naming Algorithm.
  Then they restart Duplicate FQDN Detection as described in $7.4.3$.


  7.5. Domain Name Registration
  
  6DNAC Server must be an authenticated to update the DNS Server.
  6DNAC Server must also be configured with the DNS Server 
  information.

  6DNAC Server detects the DNS information (IPv6 Address and 
  corresponding FQDN) from DAD/DFQDND messages and caches the
  information. It also have an associated Registration Timer with 
  RegistrationWaitTime to wait for the successful completion of 
  DFQDND and update DNS Server using existing protocol DDNS UPDATE 
  [2136].
  
                 
  8. Security Consideration
   
  If someone wants to hijack correct Domain Name registration, they 
  could send a NS message with incorrect or same Domain Name to the
  6DNAC server repeatedly and server would start the Domain Name 
  registration through above mechanism, which is a security hole. 
  As described in [2461], a host can check validity of NDP messages.
  If the NDP message include an IP Authentication Header, the message
  authenticates correctly. For DNS UPDATE processing, secure DNS
  Dynamic Update is described in [3007].
  







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  9. IANA Consideration
  
  Values in the Router Alert Option are registered and maintained by
  IANA. For 6DNAC, the value has to be assigned by IANA. Also IANA is
  required to assign the Type values for DNS Zone Suffix Information
  option and FADN option.

  
  10. Acknowledgement
  
  Special thanks are due to Badrinarayana N.S. and Christian Huitema for
  many helpful suggestions and revisions. 
  
  
  11. Intellectual Property

  The following notice is copied from RFC 2026 [Bradner, 1996],
  Section 10.4, and describes the position of the IETF concerning
  intellectual property claims made against this document.

  The IETF takes no position regarding the validity or scope of any
  intellectual property or other rights that might be claimed to
  pertain to the implementation or use other technology described in

  this document or the extent to which any license under such rights
  might or might not be available; neither does it represent that it
  
  has made any effort to identify any such rights.  Information on the
  IETF's procedures with respect to rights in standards-track and
  standards-related documentation can be found in BCP-11.  Copies of
  claims of rights made available for publication and any assurances
  of licenses to be made available, or the result of an attempt made
  to obtain a general license or permission for the use of such
  proprietary rights by implementers or users of this specification
  can be obtained from the IETF Secretariat.

  The IETF invites any interested party to bring to its attention any
  copyrights, patents or patent applications, or other proprietary
  rights which may cover technology that may be required to practice
  this standard.  Please address the information to the IETF Executive
  Director.
  
  
  12. Copyright

  The following copyright notice is copied from RFC 2026 [Bradner,
  1996], Section 10.4, and describes the applicable copyright for this
  document.

  Copyright (C) The Internet Society July 12, 2001. All Rights
  Reserved.
  
  This document and translations of it may be copied and furnished to
  others, and derivative works that comment on or otherwise explain it
  or assist in its implementation may be prepared, copied, published

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  and distributed, in whole or in part, without restriction of any
  kind, provided that the above copyright notice and this paragraph
  are included on all such copies and derivative works.  However, this
  
  document itself may not be modified in any way, such as by removing
  the copyright notice or references to the Internet Society or other
  Internet organizations, except as needed for the purpose of
  developing Internet standards in which case the procedures for
  copyrights defined in the Internet Standards process must be
  followed, or as required to translate it into languages other than
  English.

  The limited permissions granted above are perpetual and will not be
  revoked by the Internet Society or its successors or assignees.

  This document and the information contained herein is provided on an
  "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
  BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
  HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
  
  
  13. References
   
  [2373]        Hinden, R. and S. Deering, "IP Version 6 Addressing 
                Architecture", RFC 2373, July 1998. 
       
  [2460]        Deering, S. abd R. Hinden, "Internet Protocol, 
                Version 6 (IPv6) Specification", RFC 2460, 
                December 1998. 
               
  [2461]        Narten, T., Nordmark, E. and W. Simpson, "Neighbor 
                Discovery for IP version 6(IPv6)", RFC 2461, December 
                1998. 

  [2462]        S. Thomson and Narten T, "IPv6 Stateless Address Auto- 
                Configuration", RFC 2462, December 1998. 
               
  [2711]        C. Patridge and A.Jackson, "IPv6 Router Alert Option",
                RFC 2711, October 1999. 
             
  [1034]        P. Mockapetris, "DOMAIN NAMES - CONCEPTS AND 
                FACILITIES", RFC 1034, November 1987. 
               
  [1035]        P. Mockapetris, "Domain Names - Implementation and 
                Specification" RFC 1035, November 1987. 

  [2136]        P. Vixie et al., "Dynamic Updates in the Domain Name
                System (DNS UPDATE)", RFC2136, April 1997.
                
  [3007]        B. Wellington, "Secure Domain Name System (DNS) Dynamic 
                Update", RFC 3007, November 2000.



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  [DIID]        yokohama-dad-vs-diid.pdf
                at http://playground.sun.com/ipng/presentations/July2002/
                
  [DNSISSUES]   Durand, A., "IPv6 DNS transition issues", draft-ietf-              
                dnsop-ipv6-dns-issues-00.txt, work in progress.
                
  [PREFIX]      S. Miyakawa, R. Droms, "Requirements for IPv6 prefix
                delegation", draft-ietf-ipv6-prefix-delegation-
                requirement-01.txt, work in progress.
   
  [Autoreg]     H. Kitamura, "Domain Name Auto-Registration for 
                Plugged-in IPv6 Nodes", draft-ietf-dnsext-ipv6-name-
                auto-reg-00.txt, work in progress.

  [NIQ]         Matt Crawford, "IPv6 Node Information Queries", <draft-
                ietf-ipngwg-icmp-name-lookups-09.txt>, work in progress.
                  
  
  14. Author's Addresses 
  
  Soohong Daniel Park 
  Mobile Platform Laboratory, SAMSUNG Electronics, KOREA 
  Phone: +82-31-200-3728 
  Email:soohong.park@samsung.com
  
  Syam Madanapalli
  Network Systems Division, SAMSUNG India Software Operations, INDIA
  Phone: +91-80-5550555
  Email:syam@samsung.com
  


























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