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new draft
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Mark Andrews
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doc/draft/draft-ietf-ipngwg-rfc2553bis-07.txt
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doc/draft/draft-ietf-ipngwg-rfc2553bis-07.txt
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Network Working Group Alain Durand
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INTERNET-DRAFT SUN Microsystems, inc.
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June 14, 2002 Jun-ichiro itojun Hagino
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Expires December 2002 IIJ Research Laboratory
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August 21, 2002 Jun-ichiro itojun Hagino
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Expires February 2002 IIJ Research Laboratory
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Dave Thaler
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Microsoft
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@@ -9,11 +9,11 @@ Expires December 2002 IIJ Research Laboratory
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Well known site local unicast addresses for DNS resolver
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<draft-ietf-ipv6-dns-discovery-05.txt>
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<draft-ietf-ipv6-dns-discovery-06.txt>
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Status of this Memo
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Status of this memo
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This document is an Internet-Draft and is in full conformance with
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all provisions of Section 10 of RFC2026.
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@@ -37,16 +37,18 @@ Abstract
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This documents specifies a method for nodes to find a DNS resolver
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with minimum configuration in the network and without running a
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discovery protocol on the nodes.
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discovery protocol on the nodes. This method is to be used in last
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resort, when no other information about the addresses of DNS
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resolvers is available.
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Copyright Notice
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Copyright notice
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Copyright (C) The Internet Society (2002). All Rights Reserved.
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1. Introduction
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1. Introduction
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RFC 2462 [ADDRCONF] provides a way to autoconfigure nodes with one or
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more IPv6 address and default routes.
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@@ -99,29 +101,41 @@ Copyright Notice
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participation of the end node in the DNS resolver discovery
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mechanism.
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The mechanism described here is to be used as a last resort, when no
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other configuration information is available.
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The mechanism described here is to be used as a last resort, in the
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absence of any information about the addresses of DNS resolvers. If
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other configuration mechanisms are available, they should be tried
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first.
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Note to implementors:
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Implementing only the mechanism described in this memo may end up
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causing some interoperability problems when operating in networks
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where no DNS resolver is configured with the well known addresses.
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Thus, it is recommended to implement also other mechanisms for
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overriding this default, for example: manual configuration, L2
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mechanisms and/or DHCPv6.
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3. Reserved Prefix and addresses
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The basic idea of this proposal is to reserve a well known IPv6 site
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local prefix and three well known IPv6 addresses for DNS resolvers
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and then have the routing system forward the DNS request to those DNS
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resolvers.
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3. Reserved prefix and addresses
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IPv6 nodes will be pre-configured (hard coded) with those three IPv6
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addresses as DNS resolver.
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The basic idea of this proposal is to reserve three well known IPv6
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site local addresses for DNS resolvers and then have the routing
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system forward the DNS request to them.
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Each local DNS resolvers should be configured with one of those three
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IPv6 stub-resolvers implementing this proposal are pre-configured
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with those three IPv6 addresses as DNS resolver.
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Local DNS resolvers should be configured with one of those three
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addresses to enable clients to switch from one to the other if one
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fails. Host routes for each of those resolvers should be injected in
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the local routing system. Example methods for injecting host routes
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and a brief discussion of their fate sharing properties is presented
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here:
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fails.
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A solution to enable clients to reach the DNS resolvers is to inject
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host routes in the local routing system. Examples of methods for
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injecting host routes and a brief discussion of their fate sharing
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properties are presented here:
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a) Manual injection of routes by a router on the same subnet.
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If the node running the DNS resolver goes down, the router may or
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@@ -138,10 +152,16 @@ Copyright Notice
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threads, similar concerns as above are true.
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d) Having an "announcement" protocol that the DNS resolver could
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use to advertize the host route to the nearby router.
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Details of such a protocols are out of scope of this document, but
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something similar to [MLD] is possible.
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use to advertize the host route to the nearby router. Details of
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such a protocols are out of scope of this document, but something
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similar to [MLD] is possible.
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An alternate solution is to configure a link with the well known
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prefix and position the three DNS resolvers on that link. The
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advantage of this method is that host routes are not necessary , the
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well known prefix is advertized to the routing system by the routers
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on the link. However, in the event of a problem on the physical link,
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all resolvers will become unreachable.
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IANA considerations for this prefix are covered in Section 6.
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@@ -162,13 +182,6 @@ Copyright Notice
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are first sent to a DNS resolver located within the site perimeter
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increase their likelyhood of success.
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Note: there is currently some discussions about the usefulness of
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site local addresses in the IPv6 architecture. Depending on the
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outcome of this discussion, this section will need to be revisited.
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If a global prefix was chosen for this mechanism, concerns raised in
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a) could be addressed using a simple access list on the site exit
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routers and concerns raised in b) would disappear.
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5. Examples of use
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@@ -219,8 +232,7 @@ Copyright Notice
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customers share the same definition of site.
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In this scenario, the home/small office network is connected to the
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ISP router (PE) via an edge router (CPE). Prefix delegation is
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performed out of band is is out of scope of this memo.
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ISP router (PE) via an edge router (CPE).
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-------------
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/ |
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@@ -255,8 +267,8 @@ Copyright Notice
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5.3 DNS forwarder with DHCPv6 interactions
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In this variant scenario, DHCPv6 could be used between the PE and CPE
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to do prefix delegation [DELEG] and DNS resolver discovery.
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In this variant scenario, DHCPv6 is be used between the PE and CPE to
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do prefix delegation [DELEG] and DNS resolver discovery.
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-------------
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/ |
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@@ -269,13 +281,12 @@ Copyright Notice
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-------------
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This example will show how DHCPv6 and well known site local unicast
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addresses can be used at the same time within a site to discover the
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address of the DNS forwarder.
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addresses cooperate to enable the internal nodes to access DNS.
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The customer router CPE could be configured on its internal interface
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with one of the reserved site local addresses and listen for DNS
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queries. It would act as a DNS forwarder, forwarding those queries to
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the DNS resolver pointed out by the ISP in the DHCPv6 exchange.
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The customer router CPE is configured on its internal interface with
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one of the reserved site local addresses and listen for DNS queries.
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It would act as a DNS forwarder, as in 5.2, forwarding those queries
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to the DNS resolver pointed out by the ISP in the DHCPv6 exchange.
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-------------
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/ |
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@@ -288,8 +299,8 @@ Copyright Notice
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-------------
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The same CPE router could also act as a local DHCPv6 server,
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advertising either itself as DNS forwarder.
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The same CPE router could also implement a local DHCPv6 server and
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advertises itself as DNS forwarder.
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-------------
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/ |
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@@ -305,8 +316,8 @@ Copyright Notice
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Within the site:
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a) DHCPv6 aware clients could use DHCPv6 to obtain the address of
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the DNS forwarder...
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a) DHCPv6 aware clients use DHCPv6 to obtain the address of the
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DNS forwarder...
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-------------
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/ |
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@@ -320,8 +331,8 @@ Copyright Notice
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(The address of the DNS forwarder is aquired via DHCPv6.)
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b) other nodes may simply send their DNS request to the reserved
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site local addresses.
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b) other nodes simply send their DNS request to the reserved site
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local addresses.
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-------------
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/ |
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@@ -347,7 +358,7 @@ Copyright Notice
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of the site local fec0::/10 prefix.
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The unicast addresses fec0:000:0000:ffff::1, fec0:000:0000:ffff::2
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and fec0:000:0000:ffff::2 are to be reserved for DNS resolver
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and fec0:000:0000:ffff::3 are to be reserved for DNS resolver
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configuration.
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All other addresses within the fec0:0000:0000:ffff::/64 are reserved
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@@ -518,16 +529,6 @@ Copyright (C) The Internet Society (2002). All Rights Reserved.
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