draft-ietf-dnsop-ipv6-dns-configuration-06.txt

非常好的dns解析软件

DNS Operations WG                                          J. Jeong, Ed.
Internet-Draft                              ETRI/University of Minnesota
Expires: November 6, 2005                                    May 5, 2005


      IPv6 Host Configuration of DNS Server Information Approaches
             draft-ietf-dnsop-ipv6-dns-configuration-06.txt

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

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   This Internet-Draft will expire on November 6, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes three approaches for IPv6 recursive DNS
   server address configuration.  It details the operational attributes
   of three solutions: RA option, DHCPv6 option, and Well-known anycast
   addresses for recursive DNS servers.  Additionally, it suggests the
   deployment scenarios in four kinds of networks, such as ISP,
   Enterprise, 3GPP, and Unmanaged networks, considering multi-solution
   resolution.  Therefore, this document will give the audience a



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   guideline for IPv6 host DNS configuration.


















































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  IPv6 DNS Configuration Approaches  . . . . . . . . . . . . . .  7
     3.1   RA Option  . . . . . . . . . . . . . . . . . . . . . . . .  7
       3.1.1   Advantages . . . . . . . . . . . . . . . . . . . . . .  8
       3.1.2   Disadvantages  . . . . . . . . . . . . . . . . . . . .  8
       3.1.3   Observations . . . . . . . . . . . . . . . . . . . . .  9
     3.2   DHCPv6 Option  . . . . . . . . . . . . . . . . . . . . . .  9
       3.2.1   Advantages . . . . . . . . . . . . . . . . . . . . . . 11
       3.2.2   Disadvantages  . . . . . . . . . . . . . . . . . . . . 12
       3.2.3   Observations . . . . . . . . . . . . . . . . . . . . . 12
     3.3   Well-known Anycast Addresses . . . . . . . . . . . . . . . 12
       3.3.1   Advantages . . . . . . . . . . . . . . . . . . . . . . 13
       3.3.2   Disadvantages  . . . . . . . . . . . . . . . . . . . . 14
       3.3.3   Observations . . . . . . . . . . . . . . . . . . . . . 14
   4.  Interworking among IPv6 DNS Configuration Approaches . . . . . 15
   5.  Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 16
     5.1   ISP Network  . . . . . . . . . . . . . . . . . . . . . . . 16
       5.1.1   RA Option Approach . . . . . . . . . . . . . . . . . . 16
       5.1.2   DHCPv6 Option Approach . . . . . . . . . . . . . . . . 17
       5.1.3   Well-known Anycast Addresses Approach  . . . . . . . . 17
     5.2   Enterprise Network . . . . . . . . . . . . . . . . . . . . 17
     5.3   3GPP Network . . . . . . . . . . . . . . . . . . . . . . . 18
       5.3.1   Currently Available Mechanisms and Recommendations . . 19
       5.3.2   RA Extension . . . . . . . . . . . . . . . . . . . . . 19
       5.3.3   Stateless DHCPv6 . . . . . . . . . . . . . . . . . . . 20
       5.3.4   Well-known Addresses . . . . . . . . . . . . . . . . . 21
       5.3.5   Recommendations  . . . . . . . . . . . . . . . . . . . 21
     5.4   Unmanaged Network  . . . . . . . . . . . . . . . . . . . . 22
       5.4.1   Case A: Gateway does not provide IPv6 at all . . . . . 22
       5.4.2   Case B: A dual-stack gateway connected to a
               dual-stack ISP . . . . . . . . . . . . . . . . . . . . 22
       5.4.3   Case C: A dual-stack gateway connected to an
               IPv4-only ISP  . . . . . . . . . . . . . . . . . . . . 22
       5.4.4   Case D: A gateway connected to an IPv6-only ISP  . . . 23
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 24
     6.1   RA Option  . . . . . . . . . . . . . . . . . . . . . . . . 25
     6.2   DHCPv6 Option  . . . . . . . . . . . . . . . . . . . . . . 25
     6.3   Well-known Anycast Addresses . . . . . . . . . . . . . . . 25
   7.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     9.1   Normative References . . . . . . . . . . . . . . . . . . . 29
     9.2   Informative References . . . . . . . . . . . . . . . . . . 29
       Author's Address . . . . . . . . . . . . . . . . . . . . . . . 31
   A.  Link-layer Multicast Acknowledgements for RA Option  . . . . . 32



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       Intellectual Property and Copyright Statements . . . . . . . . 33


















































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1.  Introduction

   Neighbor Discovery (ND) for IP Version 6 and IPv6 Stateless Address
   Autoconfiguration provide the ways to configure either fixed or
   mobile nodes with one or more IPv6 addresses, default routes and some
   other parameters [3][4].  To support the access to additional
   services in the Internet that are identified by a DNS name, such as a
   web server, the configuration of at least one recursive DNS server is
   also needed for DNS name resolution.

   This document describes three approaches of recursive DNS server
   address configuration for IPv6 host: (a) RA option [8], (b) DHCPv6
   option [5]-[7], and (c) Well-known anycast addresses for recursive
   DNS servers [9].  Also, it suggests the applicable scenarios for four
   kinds of networks: (a) ISP network, (b) Enterprise network, (c) 3GPP
   network, and (d) Unmanaged network.

   This document is just an analysis of each possible approach, and does
   not make any recommendation on a particular one or on a combination
   of particular ones.  Some approaches may even not be adopted at all
   as a result of further discussion.

   Therefore, the objective of this document is to help the audience
   select the approaches suitable for IPv6 host configuration of
   recursive DNS servers.


























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2.  Terminology

   This document uses the terminology described in [3]-[9].  In
   addition, a new term is defined below:

   o  Recursive DNS Server (RDNSS): A Recursive DNS Server is a name
      server that offers the recursive service of DNS name resolution.












































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3.  IPv6 DNS Configuration Approaches

   In this section, the operational attributes of the three solutions
   are described in detail.

3.1  RA Option

   The RA approach is to define a new ND option called the RDNSS option
   that contains a recursive DNS server address.  Existing ND transport
   mechanisms (i.e., advertisements and solicitations) are used.  This
   works in the same way that nodes learn about routers and prefixes.
   An IPv6 host can configure the IPv6 addresses of one or more RDNSSes
   via RA message periodically sent by a router or solicited by a Router
   Solicitation (RS) [8].

   This approach needs RDNSS information to be configured in the routers
   doing the advertisements.  The configuration of RDNSS addresses can
   be performed manually by an operator or other ways, such as automatic
   configuration through a DHCPv6 client running on the router.  When
   advertising more than one RDNSS option, an RA message includes as
   many RDNSS options as RDNSSes.

   Through the ND protocol and RDNSS option along with a prefix
   information option, an IPv6 host can perform its network
   configuration of its IPv6 address and RDNSS simultaneously [3][4].
   The RA option for RDNSS can be used on any network that supports the
   use of ND.

   However, it is worth noting that some link layers, such as Wireless
   LANs (e.g., IEEE 802.11 a/b/g), do not support reliable multicast,
   which means that they cannot guarantee the timely delivery of RA