new draft

doc/draft/draft-ietf-ipv6-dns-discovery-06.txt

@@ -1,7 +1,7 @@
 Network Working Group                                 Alain Durand
 INTERNET-DRAFT                              SUN Microsystems, inc.
-June 14, 2002                             Jun-ichiro itojun Hagino
+August 21, 2002                           Jun-ichiro itojun Hagino
-Expires December 2002                      IIJ Research Laboratory
+Expires February 2002                      IIJ Research Laboratory
                                                        Dave Thaler
                                                          Microsoft
 
@@ -9,11 +9,11 @@ Expires December 2002                      IIJ Research Laboratory
 
 
         Well known site local unicast addresses for DNS resolver
-                 <draft-ietf-ipv6-dns-discovery-05.txt>
+                 <draft-ietf-ipv6-dns-discovery-06.txt>
 
 
 
-                          Status of this Memo
+                          Status of this memo
 
    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026.
@@ -37,16 +37,18 @@ Abstract
 
    This documents specifies a method for nodes to find a DNS resolver
    with minimum configuration in the network and without running a
-   discovery protocol on the nodes.
+   discovery protocol on the nodes. This method is to be used in last
+   resort, when no other information about the addresses of DNS
+   resolvers is available.
 
 
 
-Copyright Notice
+Copyright notice
 
    Copyright (C) The Internet Society (2002).  All Rights Reserved.
 
 
-1.  Introduction
+1. Introduction
 
    RFC 2462 [ADDRCONF] provides a way to autoconfigure nodes with one or
    more IPv6 address and default routes.
@@ -99,29 +101,41 @@ Copyright Notice
    participation of the end node in the DNS resolver discovery
    mechanism.
 
-   The mechanism described here is to be used as a last resort, when no
+   The mechanism described here is to be used as a last resort, in the
-   other configuration information is available.
+   absence of any information about the addresses of DNS resolvers.  If
+   other configuration mechanisms are available, they should be tried
+   first.
+
+   Note to implementors:
+
+   Implementing only the mechanism described in this memo may end up
+   causing some interoperability problems when operating in networks
+   where no DNS resolver is configured with the well known addresses.
+   Thus, it is recommended to implement also other mechanisms for
+   overriding this default, for example: manual configuration, L2
+   mechanisms and/or DHCPv6.
 
 
 
 
-3. Reserved Prefix and addresses
 
-   The basic idea of this proposal is to reserve a well known IPv6 site
+3. Reserved prefix and addresses
-   local prefix and three well known IPv6 addresses for DNS resolvers
-   and then have the routing system forward the DNS request to those DNS
-   resolvers.
 
-   IPv6 nodes will be pre-configured (hard coded) with those three IPv6
+   The basic idea of this proposal is to reserve three well known IPv6
-   addresses as DNS resolver.
+   site local addresses for DNS resolvers and then have the routing
+   system forward the DNS request to them.
 
-   Each local DNS resolvers should be configured with one of those three
+   IPv6 stub-resolvers implementing this proposal are pre-configured
+   with those three IPv6 addresses as DNS resolver.
+
+   Local DNS resolvers should be configured with one of those three
    addresses to enable clients to switch from one to the other if one
-   fails.  Host routes for each of those resolvers should be injected in
+   fails.
-   the local routing system. Example methods for injecting host routes
-   and a brief discussion of their fate sharing properties is presented
-   here:
 
+   A solution to enable clients to reach the DNS resolvers is to inject
+   host routes in the local routing system. Examples of methods for
+   injecting host routes and a brief discussion of their fate sharing
+   properties are presented here:
 
       a) Manual injection of routes by a router on the same subnet.
       If the node running the DNS resolver goes down, the router may or
@@ -138,10 +152,16 @@ Copyright Notice
       threads, similar concerns as above are true.
 
       d) Having an "announcement" protocol that the DNS resolver could
-      use to advertize the host route to the nearby router.
+      use to advertize the host route to the nearby router.  Details of
-      Details of such a protocols are out of scope of this document, but
+      such a protocols are out of scope of this document, but something
-      something similar to [MLD] is possible.
+      similar to [MLD] is possible.
 
+   An alternate solution is to configure a link with the well known
+   prefix and position the three DNS resolvers on that link.  The
+   advantage of this method is that host routes are not necessary , the
+   well known prefix is advertized to the routing system by the routers
+   on the link. However, in the event of a problem on the physical link,
+   all resolvers will become unreachable.
 
    IANA considerations for this prefix are covered in Section 6.
 
@@ -162,13 +182,6 @@ Copyright Notice
       are first sent to a DNS resolver located within the site perimeter
       increase their likelyhood of success.
 
-   Note: there is currently some discussions about the usefulness of
-   site local addresses in the IPv6 architecture. Depending on the
-   outcome of this discussion, this section will need to be revisited.
-   If a global prefix was chosen for this mechanism, concerns raised in
-   a) could be addressed using a simple access list on the site exit
-   routers and concerns raised in b) would disappear.
-
 
 
 5. Examples of use
@@ -219,8 +232,7 @@ Copyright Notice
    customers share the same definition of site.
 
    In this scenario, the home/small office network is connected to the
-   ISP router (PE) via an edge router (CPE). Prefix delegation is
+   ISP router (PE) via an edge router (CPE).
-   performed out of band is is out of scope of this memo.
 
                                                      -------------
                                                     /            |
@@ -255,8 +267,8 @@ Copyright Notice
 
 5.3 DNS forwarder with DHCPv6 interactions
 
-   In this variant scenario, DHCPv6 could be used between the PE and CPE
+   In this variant scenario, DHCPv6 is be used between the PE and CPE to
-   to do prefix delegation [DELEG] and DNS resolver discovery.
+   do prefix delegation [DELEG] and DNS resolver discovery.
 
                                                      -------------
                                                     /            |
@@ -269,13 +281,12 @@ Copyright Notice
                                                      -------------
 
    This example will show how DHCPv6 and well known site local unicast
-   addresses can be used at the same time within a site to discover the
+   addresses cooperate to enable the internal nodes to access DNS.
-   address of the DNS forwarder.
 
-   The customer router CPE could be configured on its internal interface
+   The customer router CPE is configured on its internal interface with
-   with one of the reserved site local addresses and listen for DNS
+   one of the reserved site local addresses and listen for DNS queries.
-   queries. It would act as a DNS forwarder, forwarding those queries to
+   It would act as a DNS forwarder, as in 5.2,  forwarding those queries
-   the DNS resolver pointed out by the ISP in the DHCPv6 exchange.
+   to the DNS resolver pointed out by the ISP in the DHCPv6 exchange.
 
                                                    -------------
                                                   /            |
@@ -288,8 +299,8 @@ Copyright Notice
                                                    -------------
 
 
-   The same CPE router could also act as a local DHCPv6 server,
+   The same CPE router could also implement a local DHCPv6 server and
-   advertising  either itself as DNS forwarder.
+   advertises itself as DNS forwarder.
 
                                                      -------------
                                                     /            |
@@ -305,8 +316,8 @@ Copyright Notice
 
    Within the site:
 
-      a) DHCPv6 aware clients could use DHCPv6 to obtain the address of
+      a) DHCPv6 aware clients use DHCPv6 to obtain the address of the
-      the DNS forwarder...
+      DNS forwarder...
 
                                                    -------------
                                                   /            |
@@ -320,8 +331,8 @@ Copyright Notice
           (The address of the DNS forwarder is aquired via DHCPv6.)
 
 
-      b) other nodes may simply send their DNS request to the reserved
+      b) other nodes simply send their DNS request to the reserved site
-      site local addresses.
+      local addresses.
 
                                                    -------------
                                                   /            |
@@ -347,7 +358,7 @@ Copyright Notice
    of the site local fec0::/10 prefix.
 
    The unicast addresses fec0:000:0000:ffff::1, fec0:000:0000:ffff::2
-   and fec0:000:0000:ffff::2 are to be reserved for DNS resolver
+   and fec0:000:0000:ffff::3 are to be reserved for DNS resolver
    configuration.
 
    All other addresses within the fec0:0000:0000:ffff::/64 are reserved
@@ -518,16 +529,6 @@ Copyright (C) The Internet Society (2002).  All Rights Reserved.
 
 
 
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