DNS Operations WG                                          J. Jeong, Ed.Internet-Draft                              ETRI/University of MinnesotaExpires: November 6, 2005                                    May 5, 2005      IPv6 Host Configuration of DNS Server Information Approaches             draft-ietf-dnsop-ipv6-dns-configuration-06.txtStatus 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.   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 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 aJeong                   Expires November 6, 2005                [Page 1]Internet-Draft    IPv6 Host Configuration of DNS Server         May 2005   guideline for IPv6 host DNS configuration.Jeong                   Expires November 6, 2005                [Page 2]Internet-Draft    IPv6 Host Configuration of DNS Server         May 2005Table 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  . . . . . 32Jeong                   Expires November 6, 2005                [Page 3]Internet-Draft    IPv6 Host Configuration of DNS Server         May 2005       Intellectual Property and Copyright Statements . . . . . . . . 33Jeong                   Expires November 6, 2005                [Page 4]Internet-Draft    IPv6 Host Configuration of DNS Server         May 20051.  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.Jeong                   Expires November 6, 2005                [Page 5]Internet-Draft    IPv6 Host Configuration of DNS Server         May 20052.  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.Jeong                   Expires November 6, 2005                [Page 6]Internet-Draft    IPv6 Host Configuration of DNS Server         May 20053.  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