draft-ietf-6man-rdnss-rfc6106bis-07.txt   draft-ietf-6man-rdnss-rfc6106bis-08.txt 
skipping to change at page 1, line 14 skipping to change at page 1, line 14
Internet-Draft Sungkyunkwan University Internet-Draft Sungkyunkwan University
Obsoletes: 6106 (if approved) S. Park Obsoletes: 6106 (if approved) S. Park
Intended status: Standards Track Korean Bible University Intended status: Standards Track Korean Bible University
Expires: September 7, 2016 L. Beloeil Expires: September 7, 2016 L. Beloeil
France Telecom R&D France Telecom R&D
S. Madanapalli S. Madanapalli
iRam Technologies iRam Technologies
March 6, 2016 March 6, 2016
IPv6 Router Advertisement Options for DNS Configuration IPv6 Router Advertisement Options for DNS Configuration
draft-ietf-6man-rdnss-rfc6106bis-07 draft-ietf-6man-rdnss-rfc6106bis-08
Abstract Abstract
This document specifies IPv6 Router Advertisement options to allow This document specifies IPv6 Router Advertisement options to allow
IPv6 routers to advertise a list of DNS recursive server addresses IPv6 routers to advertise a list of DNS recursive server addresses
and a DNS Search List to IPv6 hosts. and a DNS Search List to IPv6 hosts.
This document obsoletes RFC 6106 and allows a higher default value of This document obsoletes RFC 6106 and allows a higher default value of
the lifetime of the RA DNS options to avoid the frequent expiry of the lifetime of the RA DNS options to avoid the frequent expiry of
the options on links with a relatively high rate of packet loss. the options on links with a relatively high rate of packet loss.
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4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5 5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5
5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 6 5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 6
5.2. DNS Search List Option . . . . . . . . . . . . . . . . . . 7 5.2. DNS Search List Option . . . . . . . . . . . . . . . . . . 7
5.3. Procedure of DNS Configuration . . . . . . . . . . . . . . 8 5.3. Procedure of DNS Configuration . . . . . . . . . . . . . . 8
5.3.1. Procedure in IPv6 Host . . . . . . . . . . . . . . . . 8 5.3.1. Procedure in IPv6 Host . . . . . . . . . . . . . . . . 8
5.3.2. Warnings for DNS Options Configuration . . . . . . . . 9 5.3.2. Warnings for DNS Options Configuration . . . . . . . . 9
6. Implementation Considerations . . . . . . . . . . . . . . . . 9 6. Implementation Considerations . . . . . . . . . . . . . . . . 9
6.1. DNS Repository Management . . . . . . . . . . . . . . . . 10 6.1. DNS Repository Management . . . . . . . . . . . . . . . . 10
6.2. Synchronization between DNS Server List and Resolver 6.2. Synchronization between DNS Server List and Resolver
Repository . . . . . . . . . . . . . . . . . . . . . . . . 10 Repository . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3. Synchronization between DNS Search List and Resolver 6.3. Synchronization between DNS Search List and Resolver
Repository . . . . . . . . . . . . . . . . . . . . . . . . 12 Repository . . . . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7.1. Security Threats . . . . . . . . . . . . . . . . . . . . . 12 7.1. Security Threats . . . . . . . . . . . . . . . . . . . . . 12
7.2. Recommendations . . . . . . . . . . . . . . . . . . . . . 12 7.2. Recommendations . . . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14 10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . . 14 10.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Changes from RFC 5006 . . . . . . . . . . . . . . . . 15 Appendix A. Changes from RFC 6106 . . . . . . . . . . . . . . . . 16
Appendix B. Changes from RFC 6106 . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
The purpose of this document is to standardize an IPv6 Router The purpose of this document is to standardize an IPv6 Router
Advertisement (RA) option for DNS Recursive Server Addresses used for Advertisement (RA) option for DNS Recursive Server Addresses used for
the DNS name resolution in IPv6 hosts. This RA option was originally the DNS name resolution in IPv6 hosts. This RA option was originally
specified in an earlier Experimental specification [RFC5006]. This specified in an earlier Experimental specification [RFC5006] and was
document obsoletes [RFC6106], allowing a higher default value of the later published as a Standards Track in [RFC6106]. This document
lifetime of the RA DNS options to avoid the frequent expiry of the obsoletes [RFC6106], allowing a higher default value of the lifetime
options on links with a relatively high rate of packet loss, and also of the RA DNS options to avoid the frequent expiry of the options on
making additional clarifications, see Appendix B for details. links with a relatively high rate of packet loss, and also making
additional clarifications, see Appendix B for details.
Neighbor Discovery (ND) for IP version 6 and IPv6 stateless address Neighbor Discovery (ND) for IP version 6 and IPv6 Stateless Address
autoconfiguration provide ways to configure either fixed or mobile Autoconfiguration (SLAAC) provide ways to configure either fixed or
nodes with one or more IPv6 addresses, default routers, and some mobile nodes with one or more IPv6 addresses, default routers, and
other parameters [RFC4861][RFC4862]. Most Internet services are some other parameters [RFC4861][RFC4862]. Most Internet names are
identified by using a DNS name. The two RA options defined in this 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 document provide the DNS information needed for an IPv6 host to reach
Internet services. Internet names.
It is infeasible to manually configure nomadic hosts each time they It is infeasible to manually configure nomadic hosts each time they
connect to a different network. While a one-time static connect to a different network. While a one-time static
configuration is possible, it is generally not desirable on general- configuration is possible, it is generally not desirable on general-
purpose hosts such as laptops. For instance, locally defined name purpose hosts such as laptops. For instance, locally defined name
spaces would not be available to the host if it were to run its own spaces would not be available to the host if it were to run its own
name server software directly connected to the global DNS. recursive name server directly connected to the global DNS.
The DNS information can also be provided through DHCP [RFC3315] The DNS information can also be provided through DHCPv6 [RFC3315]
[RFC3736][RFC3646]. However, the access to DNS is a fundamental [RFC3736][RFC3646]. However, the access to DNS is a fundamental
requirement for almost all hosts, so IPv6 stateless autoconfiguration requirement for almost all hosts, so IPv6 stateless autoconfiguration
cannot stand on its own as an alternative deployment model in any cannot stand on its own as an alternative deployment model in any
practical network without any support for DNS configuration. practical network without any support for DNS configuration.
These issues are not pressing in dual-stack networks as long as a DNS These issues are not pressing in dual-stack networks as long as a DNS
server is available on the IPv4 side, but they become more critical server is available on the IPv4 side, but they become more critical
with the deployment of IPv6-only networks. As a result, this with the deployment of IPv6-only networks. As a result, this
document defines a mechanism based on IPv6 RA options to allow IPv6 document defines a mechanism based on IPv6 RA options to allow IPv6
hosts to perform the automatic DNS configuration. hosts to perform the automatic DNS configuration.
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the host learns this DNS configuration from the same RA message that the host learns this DNS configuration from the same RA message that
provides configuration information for the link. provides configuration information for the link.
The advantages and disadvantages of the RA-based approach are The advantages and disadvantages of the RA-based approach are
discussed in [RFC4339] along with other approaches, such as the DHCP discussed in [RFC4339] along with other approaches, such as the DHCP
and well-known anycast address approaches. and well-known anycast address approaches.
1.2. Coexistence of RA Options and DHCP Options for DNS Configuration 1.2. Coexistence of RA Options and DHCP Options for DNS Configuration
Two protocols exist to configure the DNS information on a host, the Two protocols exist to configure the DNS information on a host, the
Router Advertisement options described in this document and the Router Advertisement options specified in this document and the
DHCPv6 options described in [RFC3646]. They can be used together. DHCPv6 options specified in [RFC3646]. They can be used together.
The rules governing the decision to use stateful configuration The rules governing the decision to use stateful configuration
mechanisms are specified in [RFC4861]. Hosts conforming to this mechanisms are specified in [RFC4861]. Hosts conforming to this
specification MUST extract DNS information from Router Advertisement specification MUST extract DNS information from Router Advertisement
messages, unless static DNS configuration has been specified by the messages, unless static DNS configuration has been specified by the
user. If there is DNS information available from multiple Router user. If there is DNS information available from multiple Router
Advertisements and/or from DHCP, the host MUST maintain an ordered Advertisements and/or from DHCP, the host MUST maintain an ordered
list of this information as specified in Section 5.3.1. list of this information as specified in Section 5.3.1.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Terminology 3. Terminology
This document uses the terminology described in [RFC4861] and This document uses the terminology defined in [RFC4861] and
[RFC4862]. In addition, four new terms are defined below: [RFC4862]. In addition, four new terms are defined below:
o Recursive DNS Server (RDNSS): Server that provides a recursive DNS o Recursive DNS Server (RDNSS): Server that provides a recursive DNS
resolution service for translating domain names into IP addresses resolution service for translating domain names into IP addresses
as defined in [RFC1034] and [RFC1035]. or resolving PTR records, as defined in [RFC1034] and [RFC1035].
o RDNSS Option: IPv6 RA option to deliver the RDNSS information to o RDNSS Option: IPv6 RA option to deliver the RDNSS information to
IPv6 hosts [RFC4861]. IPv6 hosts [RFC4861].
o DNS Search List (DNSSL): The list of DNS suffix domain names used o DNS Search List (DNSSL): The list of DNS suffix domain names used
by IPv6 hosts when they perform DNS query searches for short, by IPv6 hosts when they perform DNS query searches for short,
unqualified domain names. unqualified domain names.
o DNSSL Option: IPv6 RA option to deliver the DNSSL information to o DNSSL Option: IPv6 RA option to deliver the DNSSL information to
IPv6 hosts. IPv6 hosts.
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ensure that there is necessary functionality to determine the search ensure that there is necessary functionality to determine the search
domains. domains.
The existing ND message (i.e., Router Advertisement) is used to carry The existing ND message (i.e., Router Advertisement) is used to carry
this information. An IPv6 host can configure the IPv6 addresses of this information. An IPv6 host can configure the IPv6 addresses of
one or more RDNSSes via RA messages. Through the RDNSS and DNSSL one or more RDNSSes via RA messages. Through the RDNSS and DNSSL
options, along with the prefix information option based on the ND options, along with the prefix information option based on the ND
protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the
network configuration of its IPv6 address and the DNS information network configuration of its IPv6 address and the DNS information
simultaneously without needing DHCPv6 for the DNS configuration. The simultaneously without needing DHCPv6 for the DNS configuration. The
RA options for RDNSS and DNSSL can be used on any network that RA options for RDNSS and DNSSL can be used on the network that
supports the use of ND. supports the use of ND.
This approach requires the manual configuration or other automatic This approach requires the manual configuration or other automatic
mechanisms (e.g., DHCPv6 or vendor proprietary configuration mechanisms (e.g., DHCPv6 or vendor proprietary configuration
mechanisms) to configure the DNS information in routers sending the mechanisms) to configure the DNS information in routers sending the
advertisements. The automatic configuration of RDNSS addresses and a advertisements. The automatic configuration of RDNSS addresses and a
DNS Search List in routers is out of scope for this document. DNS Search List in routers is out of scope for this document.
5. Neighbor Discovery Extension 5. Neighbor Discovery Extension
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The procedure of DNS configuration through the RDNSS and DNSSL The procedure of DNS configuration through the RDNSS and DNSSL
options is the same as with any other ND option [RFC4861]. options is the same as with any other ND option [RFC4861].
5.3.1. Procedure in IPv6 Host 5.3.1. Procedure in IPv6 Host
When an IPv6 host receives DNS options (i.e., RDNSS option and DNSSL When an IPv6 host receives DNS options (i.e., RDNSS option and DNSSL
option) through RA messages, it processes the options as follows: option) through RA messages, it processes the options as follows:
o The validity of DNS options is checked with the Length field; that o The validity of DNS options is checked with the Length field; that
is, the value of the Length field in the RDNSS option is greater is, the value of the Length field in the RDNSS option is greater
than or equal to the minimum value (3), and the value of the than or equal to the minimum value (3), and satisfies that (Length
Length field in the DNSSL option is greater than or equal to the - 1) % 2 == 0. The value of the Length field in the DNSSL option
minimum value (2). is greater than or equal to the minimum value (2). Also, the
validity of the RDNSS option is checked with the "Addresses of
IPv6 Recursive DNS Servers" field; that is, the addresses should
be unicast addresses.
o If the DNS options are valid, the host SHOULD copy the values of 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 the options into the DNS Repository and the Resolver Repository in
order. Otherwise, the host MUST discard the options. Refer to order. Otherwise, the host MUST discard the options. Refer to
Section 6 for the detailed procedure. Section 6 for the detailed procedure.
In the case where the DNS options of RDNSS and DNSSL can be obtained In the case where the DNS options of RDNSS and DNSSL can be obtained
from multiple sources, such as RA and DHCP, the IPv6 host SHOULD keep from multiple sources, such as RA and DHCP, the IPv6 host SHOULD keep
some DNS options from all sources. Unless explicitly specified for some DNS options from all sources. Unless explicitly specified for
the discovery mechanism, the exact number of addresses and domain the discovery mechanism, the exact number of addresses and domain
names to keep is a matter of local policy and implementation choice. names to keep is a matter of local policy and implementation choice
However, the ability to store at least three RDNSS addresses (or as a local configuration option. However, in the case of multiple
DNSSL domain names) from at least two different sources is sources, the ability to store a total of at least three RDNSS
addresses (or DNSSL domain names) from the multiple sources is
RECOMMENDED. The DNS options from Router Advertisements and DHCP RECOMMENDED. The DNS options from Router Advertisements and DHCP
SHOULD be stored into the DNS Repository and Resolver Repository so SHOULD be stored into the DNS Repository and Resolver Repository so
that information from DHCP appears there first and therefore takes that information from DHCP appears there first and therefore takes
precedence. Thus, the DNS information from DHCP takes precedence precedence. Thus, the DNS information from DHCP takes precedence
over that from RA for DNS queries. On the other hand, for DNS over that from RA for DNS queries. On the other hand, for DNS
options announced by RA, if some RAs use the Secure Neighbor options announced by RA, if some RAs use the Secure Neighbor
Discovery (SEND) protocol [RFC3971] for RA security, they MUST be Discovery (SEND) protocol [RFC3971] for RA security, they MUST be
preferred over those that do not use SEND. Refer to Section 7 for preferred over those that do not use SEND. Refer to Section 7 for
the detailed discussion on SEND for RA DNS options. the detailed discussion on SEND for RA DNS options.
5.3.2. Warnings for DNS Options Configuration 5.3.2. Warnings for DNS Options Configuration
There are two warnings for DNS options configuration: (i) warning for There are two warnings for DNS options configuration: (i) warning for
multiple sources of DNS options and (ii) warning for multiple network multiple sources of DNS options and (ii) warning for multiple network
interfaces. First, in the case of multiple sources for DNS options interfaces. First, in the case of multiple sources for DNS options
(e.g., RA and DHCP), an IPv6 host can configure its IP addresses from (e.g., RA and DHCP), an IPv6 host can configure its IP addresses from
these sources. In this case, it is not possible to control how the these sources. In this case, it is not possible to control how the
host uses DNS information and what source addresses it uses to send host uses DNS information and what source addresses it uses to send
DNS queries. As a result, configurations where different information DNS queries. As a result, configurations where different information
is provided by different sources may lead to problems. Therefore, is provided by different sources may lead to problems. Therefore,
the network administrator needs to configure DNS options in multiple the network administrator needs to configure different DNS options in
sources in order to prevent such problems from happening. the multiple sources in order to minimize the impact of such problems
[DHCPv6-SLAAC].
Second, if different DNS information is provided on different network Second, if different DNS information is provided on different network
interfaces, this can lead to inconsistent behavior. The IETF worked interfaces, this can lead to inconsistent behavior. The IETF worked
on solving this problem for both DNS and other information obtained on solving this problem for both DNS and other information obtained
by multiple interfaces [RFC6418][RFC6419], and standardized the by multiple interfaces [RFC6418][RFC6419], and standardized the
solution for RDNSS selection for multi-interfaced nodes in [RFC6731], solution for RDNSS selection for multi-interfaced nodes in [RFC6731],
which is based on DHCP. which is based on DHCP.
6. Implementation Considerations 6. Implementation Considerations
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For the configuration and management of DNS information, the For the configuration and management of DNS information, the
advertised DNS configuration information can be stored and managed in advertised DNS configuration information can be stored and managed in
both the DNS Repository and the Resolver Repository. both the DNS Repository and the Resolver Repository.
In environments where the DNS information is stored in user space and In environments where the DNS information is stored in user space and
ND runs in the kernel, it is necessary to synchronize the DNS ND runs in the kernel, it is necessary to synchronize the DNS
information (i.e., RDNSS addresses and DNS search domain names) in information (i.e., RDNSS addresses and DNS search domain names) in
kernel space and the Resolver Repository in user space. In these kernel space and the Resolver Repository in user space. In these
environments, a user space application cannot receive RA via an environments, a user space application cannot receive RA via an
ICMPv6 socket using the standard advanced socket application program ICMPv6 socket using the standard advanced socket Application Program
interface (API) in [RFC3542]. For the synchronization, an Interface (API) in [RFC3542]. For the synchronization, an
implementation where ND works in the kernel should provide a write implementation where ND works in the kernel should provide a write
operation for updating DNS information from the kernel to the operation for updating DNS information from the kernel to the
Resolver Repository. One simple approach is to have a daemon (or a Resolver Repository. One simple approach is to have a daemon (or a
program that is called at defined intervals) that keeps monitoring program that is called at defined intervals) that keeps monitoring
the Lifetimes of RDNSS addresses and DNS search domain names all the the Lifetimes of RDNSS addresses and DNS search domain names all the
time. Whenever there is an expired entry in the DNS Repository, the time. Whenever there is an expired entry in the DNS Repository, the
daemon can delete the corresponding entry from the Resolver daemon can delete the corresponding entry from the Resolver
Repository. Repository.
6.1. DNS Repository Management 6.1. DNS Repository Management
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addresses and (ii) DNS Search List that keeps the list of DNS search 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 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: RDNSS address (or DNSSL domain name) and Expiration-time as follows:
o RDNSS address for DNS Server List: IPv6 address of the Recursive o RDNSS address for DNS Server List: IPv6 address of the Recursive
DNS Server, which is available for recursive DNS resolution DNS Server, which is available for recursive DNS resolution
service in the network advertising the RDNSS option. service in the network advertising the RDNSS option.
o DNSSL domain name for DNS Search List: DNS suffix domain names, o DNSSL domain name for DNS Search List: DNS suffix domain names,
which are used to perform DNS query searches for short, which are used to perform DNS query searches for short,
unqualified domain names in the network advertising the DNSSL unqualified domain names for the RDNSS address, which is
option. advertised by the same RA message having the DNSSL option, in the
network advertising the DNSSL option.
o Expiration-time for DNS Server List or DNS Search List: The time o Expiration-time for DNS Server List or DNS Search List: The time
when this entry becomes invalid. Expiration-time is set to the when this entry becomes invalid. Expiration-time is set to the
value of the Lifetime field of the RDNSS option or DNSSL option value of the Lifetime field of the RDNSS option or DNSSL option
plus the current system time. Whenever a new RDNSS option with plus the current time. Whenever a new RDNSS option with the same
the same address (or DNSSL option with the same domain name) is address (or DNSSL option with the same domain name) is received on
received on the same interface as a previous RDNSS option (or the same interface as a previous RDNSS option (or DNSSL option),
DNSSL option), this field is updated to have a new Expiration- this field is updated to have a new Expiration-time. When the
time. When Expiration-time becomes less than the current system current time becomes larger than Expiration-time, this entry is
time, this entry is regarded as expired. regarded as expired. Note that the DNS information for the RDNSS
and DNSSL options need not be dropped if the expiry of the RA
router lifetime happens. This is because these options have their
own lifetime values.
6.2. Synchronization between DNS Server List and Resolver Repository 6.2. Synchronization between DNS Server List and Resolver Repository
When an IPv6 host receives the information of multiple RDNSS When an IPv6 host receives the information of multiple RDNSS
addresses within a network (e.g., campus network and company network) addresses within a network (e.g., campus network and company network)
through an RA message with RDNSS option(s), it stores the RDNSS through an RA message with RDNSS option(s), it stores the RDNSS
addresses (in order) into both the DNS Server List and the Resolver addresses (in order) into both the DNS Server List and the Resolver
Repository. The processing of the RDNSS consists of (i) the Repository. The processing of the RDNSS consists of (i) the
processing of RDNSS option(s) included in an RA message and (ii) the processing of RDNSS option(s) included in an RA message and (ii) the
handling of expired RDNSSes. The processing of RDNSS option(s) is as handling of expired RDNSSes. The processing of RDNSS option(s) is as
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into an unintended host's IP address with a fraudulent DNS Search into an unintended host's IP address with a fraudulent DNS Search
List. These attacks are similar to ND attacks specified in [RFC4861] List. These attacks are similar to ND attacks specified in [RFC4861]
that use Redirect or Neighbor Advertisement messages to redirect that use Redirect or Neighbor Advertisement messages to redirect
traffic to individual addresses of malicious parties. traffic to individual addresses of malicious parties.
However, the security of these RA options for DNS configuration does However, the security of these RA options for DNS configuration does
not affect ND protocol security [RFC4861]. This is because learning not affect ND protocol security [RFC4861]. This is because learning
DNS information via the RA options cannot be worse than learning bad DNS information via the RA options cannot be worse than learning bad
router information via the RA options. Therefore, the vulnerability router information via the RA options. Therefore, the vulnerability
of ND is not worse and is a subset of the attacks that any node of ND is not worse and is a subset of the attacks that any node
attached to a LAN can do independently of ND. attached to a LAN can do.
7.2. Recommendations 7.2. Recommendations
The Secure Neighbor Discovery (SEND) protocol [RFC3971] MAY be used The Secure Neighbor Discovery (SEND) protocol [RFC3971] MAY be used
as a security mechanism for ND. In this case, ND can use SEND to as a security mechanism for ND. In this case, ND can use SEND to
allow all the ND options including the RDNSS and DNSSL options to be allow all the ND options including the RDNSS and DNSSL options to be
automatically included in the signatures. Other approaches specified automatically included in the signatures. Other approaches specified
in [RFC4861] can be used for securing the RA options for DNS in [RFC4861] can be used for securing the RA options for DNS
configuration. configuration.
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Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik
Nordmark, Dan Wing, Jari Arkko, Ben Campbell, Vincent Roca, Tony Nordmark, Dan Wing, Jari Arkko, Ben Campbell, Vincent Roca, Tony
Cheneau, Fernando Gont, Jen Linkova, Ole Troan, Mark Smith, Tatuya Cheneau, Fernando Gont, Jen Linkova, Ole Troan, Mark Smith, Tatuya
Jinmei, Lorenzo Colitti, Tore Anderson, David Farmer, and Bing Liu. Jinmei, Lorenzo Colitti, Tore Anderson, David Farmer, and Bing Liu.
The authors sincerely appreciate their contributions. The authors sincerely appreciate their contributions.
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H.
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, Soliman, "Neighbor Discovery for IP version 6
September 2007. (IPv6)", RFC 4861, September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6
Address Autoconfiguration", RFC 4862, September 2007. Stateless Address Autoconfiguration", RFC 4862,
September 2007.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E.,
B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, and B. Zill, "IPv6 Scoped Address Architecture",
March 2005. RFC 4007, March 2005.
10.2. Informative References 10.2. Informative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and
STD 13, RFC 1034, November 1987. facilities", STD 13, RFC 1034, November 1987.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "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., "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.
[RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
RFC 6106, November 2010.
[RFC4339] Jeong, J., "IPv6 Host Configuration of DNS Server
Information Approaches", RFC 4339, February 2006.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
Problem Statement", RFC 6104, February 2011.
[RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield:
Protecting against Rogue DHCPv6 Servers", RFC 7610,
August 2015.
[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. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins,
Miller, "Common DNS Implementation Errors and Suggested C., and M. Carney, "Dynamic Host Configuration
Fixes", RFC 1536, October 1993. Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and [RFC3736] Droms, R., "Stateless Dynamic Host Configuration
Provisioning Domains Problem Statement", RFC 6418, Protocol (DHCP) Service for IPv6", RFC 3736,
November 2011. April 2004.
[RFC6419] Wasserman, M. and P. Seite, "Current Practices for [RFC3646] Droms, R., "DNS Configuration options for Dynamic
Multiple-Interface Hosts", RFC 6419, November 2011. Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3646, December 2003.
[RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved [RFC5006] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
Recursive DNS Server Selection for Multi-Interfaced "IPv6 Router Advertisement Option for DNS
Nodes", RFC 6731, December 2012. Configuration", RFC 5006, September 2007.
[RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei, [RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"Advanced Sockets Application Program Interface (API) for "IPv6 Router Advertisement Options for DNS
IPv6", RFC 3542, May 2003. Configuration", RFC 6106, November 2010.
Appendix A. Changes from RFC 5006 [RFC4339] Jeong, J., "IPv6 Host Configuration of DNS Server
Information Approaches", RFC 4339, February 2006.
The following changes were made from RFC 5006 "IPv6 Router [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander,
Advertisement Option for DNS Configuration": "SEcure Neighbor Discovery (SEND)", RFC 3971,
March 2005.
o Added the DNS Search List (DNSSL) option to support the [RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router
advertisement of DNS suffixes used in the DNS search along with Advertisement Problem Statement", RFC 6104,
RDNSS option in RFC 5006. February 2011.
o Clarified the coexistence of RA options and DHCP options for DNS [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-
configuration. Shield: Protecting against Rogue DHCPv6 Servers",
RFC 7610, August 2015.
o Modified the procedure in IPv6 host: [RFC1535] Gavron, E., "A Security Problem and Proposed
Correction With Widely Deployed DNS Software",
RFC 1535, October 1993.
* Clarified the procedure for DNS options in an IPv6 host. [RFC1536] Kumar, A., Postel, J., Neuman, C., Danzig, P., and S.
Miller, "Common DNS Implementation Errors and
Suggested Fixes", RFC 1536, October 1993.
* Specified a sufficient number of RDNSS addresses or DNS search [DHCPv6-SLAAC] Liu, B., Jiang, S., Gong, X., Wang, W., and E. Rey,
domain names as three. "DHCPv6/SLAAC Interaction Problems on Address and DNS
Configuration", Work in Progress, February 2016.
* Specified a way to deal with DNS options from multiple sources, [RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and
such as RA and DHCP. Provisioning Domains Problem Statement", RFC 6418,
November 2011.
o Modified the implementation considerations for DNSSL option [RFC6419] Wasserman, M. and P. Seite, "Current Practices for
handling. Multiple-Interface Hosts", RFC 6419, November 2011.
o Modified the security considerations to consider more attack [RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved
scenarios and the corresponding possible solutions. Recursive DNS Server Selection for Multi-Interfaced
Nodes", RFC 6731, December 2012.
o Modified the IANA considerations to require another IPv6 Neighbor [RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
Discovery Option type for the DNSSL option. "Advanced Sockets Application Program Interface (API)
for IPv6", RFC 3542, May 2003.
Appendix B. Changes from RFC 6106 Appendix A. Changes from RFC 6106
The following changes were made from RFC 6106 "IPv6 Router The following changes were made from RFC 6106 "IPv6 Router
Advertisement Options for DNS Configuration": Advertisement Options for DNS Configuration":
o The generation of Router Solicitation to ensure that the RDNSS o The generation of Router Solicitation to ensure that the RDNSS
information is fresh before the expiry of the RDNSS option is information is fresh before the expiry of the RDNSS option is
removed in order to prevent multicast traffic on the link from removed in order to prevent multicast traffic on the link from
increasing. increasing.
o The lifetime's upper bound of 2 * MaxRtrAdvInterval was shown to o The lifetime's upper bound of 2 * MaxRtrAdvInterval was shown to
lead to the expiry of these options on links with a relatively lead to the expiry of these options on links with a relatively
high rate of packet loss. This revision relaxes the upper bound high rate of packet loss. This revision relaxes the upper bound
and sets a higher default value to avoid this problem. and sets a higher default value to avoid this problem.
o The lifetimes of RDNSS and DNSSL options are decoupled from Router
Lifetime. An RA router lifetime of zero does not cause the RDNSS
and DNSSL options to be considered invalid because these options
have their own lifetime values. Thus, due to the expiry of the RA
router lifetime, the lists in the RDNSS and DNSSL options are not
guaranteed to be reachable at any point in time.
o The addresses for recursive DNS servers in the RDNSS option can be o The addresses for recursive DNS servers in the RDNSS option can be
not only global addresses, but also link-local addresses. The not only global addresses, but also link-local addresses. The
link-local addresses for RDNSSes should be registered into the link-local addresses for RDNSSes should be registered into the
resolver repository along with the corresponding link zone resolver repository along with the corresponding link zone
indices. indices.
o The recommendation that at most three RDNSS addresses to maintain o The recommendation that at most three RDNSS addresses to maintain
by RDNSS options should be limited is removed. By this removal, by RDNSS options should be limited is removed. By this removal,
the number of RDNSSes to maintain is up to an implementer's local the number of RDNSSes to maintain is up to an implementer's local
policy. policy.
 End of changes. 45 change blocks. 
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