[Docs] [txt|pdf] [Tracker] [WG] [Email] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 RFC 6106

Network Working Group                                      J. Jeong, Ed.
Internet-Draft                                              Brocade/ETRI
Obsoletes: 5006 (if approved)                                    S. Park
Intended status: Standards Track                     SAMSUNG Electronics
Expires: October 7, 2010                                      L. Beloeil
                                                      France Telecom R&D
                                                          S. Madanapalli
                                                      Ordyn Technologies
                                                           April 5, 2010


  IPv6 Router Advertisement Options for DNS Configuration RFC 5006-bis
                   draft-ietf-6man-dns-options-bis-00

Abstract

   This document specifies IPv6 Router Advertisement options to allow
   IPv6 routers to advertise a list of DNS recursive server addresses
   and a DNS search list to IPv6 hosts.

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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

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

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

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

   This Internet-Draft will expire on October 7, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




Jeong, et al.            Expires October 7, 2010                [Page 1]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Applicability Statements . . . . . . . . . . . . . . . . .  3
     1.2.  Coexistence of RA Options and DHCP Options for DNS
           Configuration  . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   5.  Neighbor Discovery Extension . . . . . . . . . . . . . . . . .  6
     5.1.  Recursive DNS Server Option  . . . . . . . . . . . . . . .  6
     5.2.  DNS Search List Option . . . . . . . . . . . . . . . . . .  7
     5.3.  Procedure of DNS Configuration . . . . . . . . . . . . . .  8
       5.3.1.  Procedure in IPv6 Host . . . . . . . . . . . . . . . .  8
   6.  Implementation Considerations  . . . . . . . . . . . . . . . .  9
     6.1.  DNS Repository Management  . . . . . . . . . . . . . . . .  9
     6.2.  Synchronization between DNS Server List and Resolver
           Repository . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.3.  Synchronization between DNS Search List and Resolver
           Repository . . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
     10.2. Informative References . . . . . . . . . . . . . . . . . . 14















Jeong, et al.            Expires October 7, 2010                [Page 2]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


1.  Introduction

   The purpose of this document is to standardize IPv6 Router
   Advertisement (RA) option for DNS configuration in IPv6 hosts
   specified in [RFC5006] and also to define a new RA option for Domain
   Name Search lists.

   Neighbor Discovery (ND) for IP Version 6 and IPv6 Stateless Address
   Autoconfiguration provide ways to configure either fixed or mobile
   nodes with one or more IPv6 addresses, default routers and some other
   parameters [RFC4861][RFC4862].  Most Internet services are identified
   by using a DNS name.  The two RA options defined in this document
   provide the DNS information needed for an IPv6 host to reach Internet
   services.

   It is infeasible for nomadic hosts, such as laptops, to be configured
   manually with a DNS resolver each time they connect to a different
   wireless LAN (WLAN) such as IEEE 802.11 a/b/g [IEEE-802.11]
   [IEEE-802.11a][IEEE-802.11b][IEEE-802.11g].  This document defines a
   mechanism based on IPv6 RA options to allow IPv6 hosts to perform the
   automatic DNS configuration.  As an alternative to the DNS
   configuration provided by DHCP [RFC3315][RFC3736][RFC3646], the RA-
   based DNS configuration can allow network operators or users to
   select an appropriate automatic DNS configuration for IPv6 hosts,
   depending on the types of their networks [RFC4339].

1.1.  Applicability Statements

   RA-based DNS configuration is a useful alternative in networks where
   an IPv6 host's address is autoconfigured through IPv6 stateless
   address autoconfiguration, where the delays in acquiring server
   addresses and communicating with the servers are critical, or where
   the network operator or host operator does not want the additional
   operational complexity of running DHCPv6 to provide the same
   information to all hosts on the network.  RA-based DNS configuration
   allows the host to acquire the DNS configuration (i.e., DNS recursive
   server addresses and DNS search list) for the link(s) to which the
   host is connected.  Furthermore, it learns this DNS configuration
   from the same RA message that provides configuration information for
   the link, thereby avoiding also running DHCPv6.  This can be
   beneficial in some mobile environments, such as with Mobile IPv6
   [RFC3775].

   The advantages and disadvantages of the RA-based approach are
   discussed in [RFC4339] along with other approaches, such as the DHCP
   and well-known anycast addresses approaches.





Jeong, et al.            Expires October 7, 2010                [Page 3]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


1.2.  Coexistence of RA Options and DHCP Options for DNS Configuration

   Two protocols exist to configure the DNS information on a host, the
   Router Advertisement options described in this document and the
   DHCPv6 options described in [RFC3646].  They can be used together
   [RFC4339].  To order the RA and DHCP approaches, the O (Other
   stateful configuration) flag can be used in the RA message [RFC4861].
   The O flag is defined along with the M (Managed address
   configuration) flag in the Router Advertisement Message Format of
   [RFC4861] as follows:

   Fields:

     M             1-bit "Managed address configuration" flag.  When
                   set, it indicates that addresses are available via
                   Dynamic Host Configuration Protocol (DHCPv6) in
                   [RFC3315].

                   If the M flag is set, the O flag is redundant and
                   can be ignored because DHCPv6 will return all
                   available configuration information.

     O             1-bit "Other configuration" flag.  When set, it
                   indicates that other configuration information is
                   available via DHCPv6.  Examples of such information
                   are DNS-related information or information on other
                   servers within the network.

       Note: If neither M nor O flags are set, this indicates that no
       information is available via DHCPv6.

   Based on the definition of the O flag above, if RA options for DNS
   configuration are included in the RA messages, an IPv6 host may
   perform another DNS configuration through DHCPv6 only when the O flag
   is set.  On the other hand, if no RA options for DNS configuration
   are included in the RA messages, an IPv6 host may perform DNS
   configuration through DHCPv6 regardless of whether the O flag is set
   or not.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].







Jeong, et al.            Expires October 7, 2010                [Page 4]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


3.  Terminology

   This document uses the terminology described in [RFC4861] and
   [RFC4862].  In addition, four new terms are defined below:

   o  Recursive DNS Server (RDNSS): Server which provides a recursive
      DNS resolution service for translating domain names into IP
      addresses as defined in [RFC1034] and [RFC1035].

   o  RDNSS Option: IPv6 RA option to deliver the RDNSS information to
      IPv6 hosts [RFC4861].

   o  DNS Search List (DNSSL): The list of DNS suffix domain names used
      by IPv6 hosts when they perform DNS query searches for short,
      unqualified domain names.

   o  DNSSL Option: IPv6 RA option to deliver the DNSSL information to
      IPv6 hosts.

   o  DNS Repository: Two data structures for managing DNS Configuration
      Information in the IPv6 protocol stack in addition to Neighbor
      Cache and Destination Cache for Neighbor Discovery [RFC4861].  The
      first data structure is the DNS Server List for RDNSS addresses
      and the second is the DNS Search List for DNS search domain names.

   o  Resolver Repository: Configuration repository with RDNSS addresses
      and a DNS search list that a DNS resolver on the host uses for DNS
      name resolution; for example, the Unix resolver file (i.e., /etc/
      resolv.conf) and Windows registry.

4.  Overview

   This document standardizes the ND option called RDNSS option defined
   in [RFC5006] that contains the addresses of recursive DNS servers.
   This document also defines a new ND option called DNSSL option for
   Domain Search List.  This is for two reasons for the new option, the
   first is to maintain parity with the DHCPv6 options for DNS
   configuration [RFC3646], so that RA and DHCPv6 do not unnecessarily
   diverge and so that RA can provide the same DNS configuration as
   DHCPv6.  The second reason is that a Domain Search List is useful to
   support multi-homed hosts querying DNS servers which provide
   different answers [ID-savolainen].

   Existing ND transport mechanisms (i.e., advertisements and
   solicitations) are used.  This works in the same way that hosts learn
   about routers and prefixes.  An IPv6 host can configure the IPv6
   addresses of one or more RDNSSes via RA messages periodically sent by
   a router or solicited by a Router Solicitation (RS).



Jeong, et al.            Expires October 7, 2010                [Page 5]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


   Through the RDNSS and DNSSL options, along with the prefix
   information option based on the ND protocol ([RFC4861] and
   [RFC4862]), an IPv6 host can perform the network configuration of its
   IPv6 address and the DNS information simultaneously without needing
   DHCPv6 for the DNS configuration.  The RA options for RDNSS and DNSSL
   can be used on any network that supports the use of ND.

   This approach requires the manual configuration or other automatic
   mechanisms (e.g., DHCPv6 or vendor proprietary configuration
   mechanisms) to configure the DNS information in routers sending the
   advertisements.  The automatic configuration of RDNSS addresses and a
   DNS search list in routers is out of scope for this document.

5.  Neighbor Discovery Extension

   The IPv6 DNS configuration mechanism in this document needs two new
   ND options in Neighbor Discovery: (i) the Recursive DNS Server
   (RDNSS) option and (ii) the DNS Search List (DNSSL) option.

5.1.  Recursive DNS Server Option

   The RDNSS option contains one or more IPv6 addresses of recursive DNS
   servers.  All of the addresses share the same lifetime value.  If it
   is desirable to have different lifetime values, multiple RDNSS
   options can be used.  Figure 1 shows the format of the RDNSS option.

      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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Lifetime                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     :            Addresses of IPv6 Recursive DNS Servers            :
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 1: Recursive DNS Server (RDNSS) Option Format

   Fields:

     Type          8-bit identifier of the RDNSS option type as assigned
                   by the IANA: 25

     Length        8-bit unsigned integer.  The length of the option
                   (including the Type and Length fields) is in units of
                   8 octets.  The minimum value is 3 if one IPv6 address



Jeong, et al.            Expires October 7, 2010                [Page 6]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


                   is contained in the option.  Every additional RDNSS
                   address increases the length by 2.  The Length field
                   is used by the receiver to determine the number of
                   IPv6 addresses in the option.

     Lifetime      32-bit unsigned integer.  The maximum time, in
                   seconds (relative to the time the packet is sent),
                   over which this RDNSS address MAY be used for name
                   resolution.  Hosts MAY send a Router Solicitation to
                   ensure the RDNSS information is fresh before the
                   interval expires.  In order to provide fixed hosts
                   with stable DNS service and allow mobile hosts to
                   prefer local RDNSSes to remote RDNSSes, the value of
                   Lifetime should be at least as long as the Maximum RA
                   Interval (MaxRtrAdvInterval) in [RFC4861], and be at
                   most as long as two times MaxRtrAdvInterval; Lifetime
                   SHOULD be bounded as follows:  MaxRtrAdvInterval <=
                   Lifetime <= 2*MaxRtrAdvInterval.  A value of all one
                   bits (0xffffffff) represents infinity.  A value of
                   zero means that the RDNSS address MUST no longer be
                   used.

     Addresses of IPv6 Recursive DNS Servers
                   One or more 128-bit IPv6 addresses of the recursive
                   DNS servers.  The number of addresses is determined
                   by the Length field.  That is, the number of
                   addresses is equal to (Length - 1) / 2.

5.2.  DNS Search List Option

   The DNSSL option contains one or more domain names of DNS suffixes.
   All of the domain names share the same lifetime value.  If it is
   desirable to have different lifetime values, multiple DNSSL options
   can be used.  Figure 2 shows the format of the DNSSL option.

      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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Lifetime                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     :                Domain Names of DNS Search List                :
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: DNS Search List (DNSSL) Option Format



Jeong, et al.            Expires October 7, 2010                [Page 7]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


   Fields:

     Type          8-bit identifier of the RDNSS option type as assigned
                   by the IANA: (TBD)

     Length        8-bit unsigned integer.  The length of the option
                   (including the Type and Length fields) is in units of
                   8 octets.  The minimum value is 2 if at least one
                   domain name is contained in the option.  The Length
                   field is set to a multiple of 8 octets to accommodate
                   all the domain names in the field of Domain Names of
                   DNS Search List.

     Lifetime      32-bit unsigned integer.  The maximum time, in
                   seconds (relative to the time the packet is sent),
                   over which this DNSSL domain name MAY be used for
                   name resolution.  The Lifetime value has the same
                   semantics as with RDNSS option.  That is, Lifetime
                   SHOULD be bounded as follows:  MaxRtrAdvInterval <=
                   Lifetime <= 2*MaxRtrAdvInterval.  A value of all one
                   bits (0xffffffff) represents infinity.  A value of
                   zero means that the DNSSL domain name MUST no longer
                   be used.

     Domain Names of DNS Search List
                   One or more domain names of DNS search list that MUST
                   be encoded in the non-compressed form, using the
                   technique described in Section 3.1 of [RFC1035].  The
                   size of this field is a multiple of 8 octets.  The
                   remaining octets other than the encoding parts for
                   the domain names are padded with zeros.

5.3.  Procedure of DNS Configuration

   The procedure of DNS configuration through the RDNSS and DNSSL
   options is the same as with any other ND option [RFC4861].

5.3.1.  Procedure in IPv6 Host

   When an IPv6 host receives DNS options (i.e., RDNSS option and DNSSL
   option) through RA messages, it checks whether the options are valid
   or not as follow:

   o  If the DNS options are valid, the host SHOULD copy the values of
      the options into the DNS Repository and the Resolver Repository in
      order; the value of the Length field in the RDNSS option is
      greater than or equal to the minimum value (3) and also the value
      of the Length field in the DNSSL option is greater than or equal



Jeong, et al.            Expires October 7, 2010                [Page 8]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


      to the minimum value (2).

   o  If the DNS options are invalid, the host MUST discard the options;
      for example, the Length field in the RDNSS option has a value less
      than 3 or the Length field in the DNSSL option has a value less
      than 2.

   When the IPv6 host has gathered a sufficient number of RDNSS
   addresses (or DNS search domain names), it MAY ignore additional
   RDNSS addresses (or DNS search domain names) within an RDNSS (or
   DNSSL) option and/or additional RDNSS (or DNSSL) options within an
   RA.

6.  Implementation Considerations

   Note:  This non-normative section gives some hints for implementing
      the processing of the RDNSS and DNSSL options in an IPv6 host.

   For the configuration and management of DNS information, the
   advertised DNS configuration information can be stored and managed in
   both the DNS Repository and the Resolver Repository.

   In environments where the DNS information is stored in user space and
   ND runs in the kernel, it is necessary to synchronize the DNS
   information (i.e., RDNSS addresses and DNS search domain names) in
   kernel space and the Resolver Repository in user space.  For the
   synchronization, an implementation where ND works in the kernel
   should provide a write operation for updating DNS information from
   the kernel to the Resolver Repository.  One simple approach is to
   have a daemon (or a program that is called at defined intervals) that
   keeps monitoring the lifetimes of RDNSS addresses and DNS search
   domain names all the time.  Whenever there is an expired entry in the
   DNS Repository, the daemon can delete the corresponding entry from
   the Resolver Repository.

6.1.  DNS Repository Management

   For DNS repository management, the kernel or user-space process
   (depending on where RAs are processed) should maintain two data
   structures: (i) DNS Server List that keeps the list of RDNSS
   addresses and (ii) DNS Search List that keeps the list of DNS search
   domain names.  Each entry in these two lists consists of a pair of an
   RDNSS address (or DNSSL domain name) and Expiration-time as follows:

   o  RDNSS address for DNS Server List: IPv6 address of the Recursive
      DNS Server, which is available for recursive DNS resolution
      service in the network advertising the RDNSS option; such a
      network is called "site" in this document.



Jeong, et al.            Expires October 7, 2010                [Page 9]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


   o  DNSSL domain name for DNS Search List: DNS suffix domain names,
      which is used to perform DNS query searches for short, unqualified
      domain names in the network advertising the DNSSL option; such a
      network is called "site" in this document.

   o  Expiration-time for DNS Server List or DNS Search List: The time
      when this entry becomes invalid.  Expiration-time is set to the
      value of the Lifetime field of the RDNSS option or DNSSL option
      plus the current system time.  Whenever a new RDNSS option with
      the same address (or DNSSL option with the same domain name) is
      received on the same interface as a previous RDNSS option (or
      DNSSL option), this field is updated to have a new expiration
      time.  When Expiration-time becomes less than the current system
      time, this entry is regarded as expired.

   Note:  An RDNSS address or a DNSSL domain name MUST be used only as
      long as both the RA router lifetime and the option lifetime have
      not expired.  The reason is that the RDNSS may not be currently
      reachable, that the DNSSL domain name is not valid any more, or
      that these options do not provide service to the host's current
      address (e.g., due to network ingress filtering
      [RFC2827][RFC5358]).

6.2.  Synchronization between DNS Server List and Resolver Repository

   When an IPv6 host receives the information of multiple RDNSS
   addresses within a site through an RA message with RDNSS option(s),
   it stores the RDNSS addresses (in order) into both the DNS Server
   List and the Resolver Repository.  The processing of the RDNSS
   option(s) included in an RA message is as follows:

      Step (a): Receive and parse the RDNSS option(s).  For the RDNSS
      addresses in each RDNSS option, perform Step (b) through Step (d).
      Note that Step (e) is performed whenever an entry expires in the
      DNS Server List.

      Step (b): For each RDNSS address, check the following: If the
      RDNSS address already exists in the DNS Server List and the RDNSS
      option's Lifetime field is set to zero, delete the corresponding
      RDNSS entry from both the DNS Server List and the Resolver
      Repository in order to prevent the RDNSS address from being used
      any more for certain reasons in network management, e.g., the
      termination of the RDNSS or a renumbering situation.  The
      processing of this RDNSS address is finished here.  Otherwise, go
      to Step (c).

      Step (c): For each RDNSS address, if it already exists in the DNS
      Server List, then just update the value of the Expiration-time



Jeong, et al.            Expires October 7, 2010               [Page 10]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


      field according to the procedure specified in the second bullet of
      Section 6.1.  Otherwise, go to Step (d).

      Step (d): For each RDNSS address, if it does not exist in the DNS
      Server List, register the RDNSS address and lifetime with the DNS
      Server List and then insert the RDNSS address in front of the
      Resolver Repository.  In the case where the data structure for the
      DNS Server List is full of RDNSS entries, delete from the DNS
      Server List the entry with the shortest expiration time (i.e., the
      entry that will expire first).  The corresponding RDNSS address is
      also deleted from the Resolver Repository.  In the order in the
      RDNSS option, position the newly added RDNSS addresses in front of
      the Resolver Repository so that the new RDNSS addresses may be
      preferred according to their order in the RDNSS option for the DNS
      name resolution.  The processing of these RDNSS addresses is
      finished here.  Note that, in the case where there are several
      routers advertising RDNSS option(s) in a subnet, the RDNSSes that
      have been announced recently are preferred.

      Step (e): Delete each expired entry from the DNS Server List, and
      delete the RDNSS address corresponding to the entry from the
      Resolver Repository.

6.3.  Synchronization between DNS Search List and Resolver Repository

   When an IPv6 host receives the information of multiple DNSSL domain
   names within a site through an RA message with DNSSL option(s), it
   stores the DNSSL domain names (in order) into both the DNS Search
   List and the Resolver Repository.  The processing of the DNSSL
   option(s) included in an RA message is as follows:

      Step (a): Receive and parse the DNSSL option(s).  For the DNSSL
      domain names in each DNSSL option, perform Step (b) through Step
      (d).  Note that Step (e) is performed whenever an entry expires in
      the DNS Search List.

      Step (b): For each DNSSL domain name, check the following: If the
      DNSSL domain name already exists in the DNS Search List and the
      DNSSL option's Lifetime field is set to zero, delete the
      corresponding DNSSL entry from both the DNS Search List and the
      Resolver Repository in order to prevent the DNSSL domain name from
      being used any more for certain reasons in network management,
      e.g., the termination of the RDNSS or a renaming situation.  The
      processing of this DNSSL domain name is finished here.  Otherwise,
      go to Step (c).

      Step (c): For each DNSSL domain name, if it already exists in the
      DNS Server List, then just update the value of the Expiration-time



Jeong, et al.            Expires October 7, 2010               [Page 11]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


      field according to the procedure specified in the second bullet of
      Section 6.1.  Otherwise, go to Step (d).

      Step (d): For each DNSSL domain name, if it does not exist in the
      DNS Search List, register the DNSSL domain name and lifetime with
      the DNS Search List and then insert the DNSSL domain name in front
      of the Resolver Repository.  In the case where the data structure
      for the DNS Search List is full of DNSSL domain name entries,
      delete from the DNS Server List the entry with the shortest
      expiration time (i.e., the entry that will expire first).  The
      corresponding DNSSL domain name is also deleted from the Resolver
      Repository.  In the order in the DNSSL option, position the newly
      added DNSSL domain names in front of the Resolver Repository so
      that the new DNSSL domain names may be preferred according to
      their order in the DNSSL option for the DNS domain name used by
      the DNS query.  The processing of these DNSSL domain name is
      finished here.  Note that, in the case where there are several
      routers advertising DNSSL option(s) in a subnet, the DNSSL domain
      names that have been announced recently are preferred.

      Step (e): Delete each expired entry from the DNS Search List, and
      delete the DNSSL domain name corresponding to the entry from the
      Resolver Repository.

7.  Security Considerations

   The security of the RA options for DNS configuration does not affect
   ND protocol security [RFC4861].  This is because learning DNS
   information via the RA options cannot be worse than learning bad
   router information via the RA options.  It can be claimed that the
   vulnerability of ND is not worse and is a subset of the attacks that
   any node attached to a LAN can do independently of ND.  A malicious
   node on a LAN can promiscuously receive packets for any router's MAC
   address and send packets with the router's MAC address as the source
   MAC address in the L2 header.  As a result, L2 switches send packets
   addressed to the router to the malicious node.  Also, this attack can
   send redirects that tell the hosts to send their traffic somewhere
   else.  The malicious node can send unsolicited RA or Neighbor
   Advertisement (NA) replies, answer RS or Neighbor Solicitation (NS)
   requests, etc.  Also, an attacker could configure a host to send out
   an RA with a fraudulent RDNSS address, which is presumably an easier
   avenue of attack than becoming a rogue router and having to process
   all traffic for the subnet.  It is necessary to disable the RA RDNSS
   option or DNSSL option in both routers and clients administratively
   to avoid this problem.  All of this can be done independently of
   implementing ND.  Therefore, it can be claimed that the RA options
   for RDNSS and DNSSL has vulnerabilities similar to those existing in
   unauthenticated DHCPv6.



Jeong, et al.            Expires October 7, 2010               [Page 12]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


   It is common for network devices such as switches to include
   mechanisms to block unauthorized ports from running a DHCPv6 server
   to provide protection from rogue DHCP servers.  That means that an
   attacker on other ports cannot insert bogus DNS servers using DHCPv6.
   The corresponding technique for network devices is recommended to
   block rogue Router Advertisement messages including the RDNSS and
   DNSSL options from unauthorized nodes.

   An attacker may provide a bogus DNS Search List option in order to
   cause the victim to send DNS queries to a specific DNS server when
   the victim queries non-fully qualified domain names.  For this
   attack, the DNS resolver in IPv6 hosts can mitigate the vulnerability
   with the recommendations in [RFC1535], [RFC1536], and [RFC3646].

   If the Secure Neighbor Discovery (SEND) protocol is used as a
   security mechanism for ND, all the ND options including the RDNSS and
   DNSSL options are automatically included in the signatures [RFC3971],
   so the transport for the RA options is integrity-protected.  However,
   since any valid SEND node can still insert RDNSS and DNSSL options,
   SEND cannot verify who is or is not authorized to send the options.

8.  IANA Considerations

   The RDNSS option defined in this document is using the IPv6 Neighbor
   Discovery Option type in RFC 5006 [RFC5006] assigned by the IANA as
   follows:

                 Option Name               Type
                 RDNSS option              25

   The IANA is requested to assign a new IPv6 Neighbor Discovery Option
   type for the DNSSL option defined in this document:

                 Option Name               Type
                 DNSSL option              (TBD)

   The IANA registry for these options is:

       http://www.iana.org/assignments/icmpv6-parameters

9.  Acknowledgements

   This document has greatly benefited from inputs by Robert Hinden,
   Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik
   Nordmark, and Dan Wing.  The authors sincerely appreciate their
   contributions.

10.  References



Jeong, et al.            Expires October 7, 2010               [Page 13]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


10.1.  Normative References

   [RFC2119]        Bradner, S., "Key words for use in RFCs to Indicate
                    Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4861]        Narten, T., Nordmark, E., Simpson, W., and H.
                    Soliman, "Neighbor Discovery for IP Version 6
                    (IPv6)", RFC 4861, September 2007.

   [RFC4862]        Thomson, S., Narten, T., and T. Jinmei, "IPv6
                    Stateless Address Autoconfiguration", RFC 4862,
                    September 2007.

10.2.  Informative References

   [RFC1034]        Mockapetris, P., "Domain Names - Concepts and
                    Facilities", RFC 1034, November 1987.

   [RFC1035]        Mockapetris, P., "Domain Names - Implementation and
                    Specification", RFC 1035, November 1987.

   [RFC3315]        Droms, R., Ed., "Dynamic Host Configuration Protocol
                    for IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3736]        Droms, R., "Stateless Dynamic Host Configuration
                    Protocol (DHCP) Service for IPv6", RFC 3736,
                    April 2004.

   [RFC3646]        Droms, R., Ed., "DNS Configuration options for
                    Dynamic Host Configuration Protocol for IPv6
                    (DHCPv6)", RFC 3646, December 2003.

   [RFC5006]        Jeong, J., Park, S., Beloeil, L., and S.
                    Madanapalli, "IPv6 Router Advertisement Option for
                    DNS Configuration", RFC 5006, September 2007.

   [RFC4339]        Jeong, J., Ed., "IPv6 Host Configuration of DNS
                    Server Information Approaches", RFC 4339,
                    February 2006.

   [RFC3775]        Johnson, D., Perkins, C., and J. Arkko, "Mobility
                    Support in IPv6", RFC 3775, June 2004.

   [RFC3971]        Arkko, J., Ed., "SEcure Neighbor Discovery (SEND)",
                    RFC 3971, March 2005.

   [IEEE-802.11]    ANSI/IEEE Std 802.11, "Part 11: Wireless LAN Medium
                    Access Control (MAC) and Physical Layer (PHY)



Jeong, et al.            Expires October 7, 2010               [Page 14]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


                    Specifications", March 1999.

   [IEEE-802.11a]   IEEE Std 802.11a, "Part 11: Wireless LAN Medium
                    Access Control (MAC) and Physical Layer (PHY)
                    specifications: High-speed Physical Layer in the 5
                    GHZ Band", September 1999.

   [IEEE-802.11b]   IEEE Std 802.11b, "Part 11: Wireless LAN Medium
                    Access Control (MAC) and Physical Layer (PHY)
                    specifications: Higher-Speed Physical Layer
                    Extension in the 2.4 GHz Band", September 1999.

   [IEEE-802.11g]   IEEE P802.11g/D8.2, "Part 11: Wireless LAN Medium
                    Access Control (MAC) and Physical Layer (PHY)
                    specifications: Further Higher Data Rate Extension
                    in the 2.4 GHz Band", April 2003.

   [RFC5358]        Damas, J. and F. Neves, "Preventing Use of Recursive
                    Nameservers in Reflector Attacks", BCP 140,
                    RFC 5358, October 2008.

   [RFC2827]        Ferguson, P. and D. Senie, "Network Ingress
                    Filtering: Defeating Denial of Service Attacks which
                    employ IP Source Address Spoofing", BCP 38,
                    RFC 2827, May 2000.

   [ID-savolainen]  Savolainen, T., "Preventing Use of Recursive
                    Nameservers in Reflector Attacks", Work in Progress,
                    February 2010.

   [RFC1535]        Gavron, E., "A Security Problem and Proposed
                    Correction With Widely Deployed DNS Software",
                    RFC 1535, October 1993.

   [RFC1536]        Kumar, A., Postel, J., Neuman, C., Danzig, P., and
                    S. Miller, "Common DNS Implementation Errors and
                    Suggested Fixes", RFC 1536, October 1993.














Jeong, et al.            Expires October 7, 2010               [Page 15]


Internet-Draft      IPv6 RA DNS Options RFC 5006-bis          April 2010


Authors' Addresses

   Jaehoon Paul Jeong (editor)
   Brocade Communications Systems/ETRI
   6000 Nathan Ln N
   Plymouth, MN  55442
   USA

   Phone: +1 763 268 7173
   Fax:   +1 763 268 6800
   EMail: pjeong@brocade.com
   URI:   http://www.cs.umn.edu/~jjeong/


   Soohong Daniel Park
   Mobile Platform Laboratory
   SAMSUNG Electronics
   416 Maetan-3dong, Yeongtong-Gu
   Suwon, Gyeonggi-Do  443-742
   Korea

   Phone: +82 31 200 4508
   EMail: soohong.park@samsung.com


   Luc Beloeil
   France Telecom R&D
   42, rue des coutures
   BP 6243
   14066 CAEN Cedex 4
   France

   Phone: +33 02 3175 9391
   EMail: luc.beloeil@orange-ftgroup.com


   Syam Madanapalli
   Ordyn Technologies
   1st Floor, Creator Building, ITPL
   Bangalore - 560066
   India

   Phone: +91-80-40383000
   EMail: smadanapalli@gmail.com







Jeong, et al.            Expires October 7, 2010               [Page 16]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/