Internet DRAFT - draft-ietf-6man-rdnss-rfc6106bis
draft-ietf-6man-rdnss-rfc6106bis
Network Working Group J. Jeong
Internet-Draft Sungkyunkwan University
Obsoletes: 6106 (if approved) S. Park
Intended status: Standards Track Samsung Electronics
Expires: August 12, 2017 L. Beloeil
France Telecom R&D
S. Madanapalli
NTT Data
February 8, 2017
IPv6 Router Advertisement Options for DNS Configuration
draft-ietf-6man-rdnss-rfc6106bis-16
Abstract
This document specifies IPv6 Router Advertisement (RA) options
(called DNS RA options) to allow IPv6 routers to advertise a list of
DNS recursive server addresses and a DNS Search List to IPv6 hosts.
This document, which obsoletes RFC 6106, defines a higher default
value of the lifetime of the DNS RA options to reduce the likelihood
of expiry of the options on links with a relatively high rate of
packet loss.
Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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-
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Internet-Drafts are draft documents valid for a maximum of six months
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The list of current Internet-Drafts can be accessed at
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http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 12, 2017.
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Applicability Statements . . . . . . . . . . . . . . . . . 3
1.2. Coexistence of RA Options and DHCP Options for DNS
Configuration . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5
5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 5
5.2. DNS Search List Option . . . . . . . . . . . . . . . . . . 7
5.3. Procedure of DNS Configuration . . . . . . . . . . . . . . 8
5.3.1. Procedure in IPv6 Hosts . . . . . . . . . . . . . . . 8
5.3.2. Warnings for DNS Options Configuration . . . . . . . . 9
6. Implementation Considerations . . . . . . . . . . . . . . . . 10
6.1. DNS Repository Management . . . . . . . . . . . . . . . . 10
6.2. Synchronization between DNS Server List and Resolver
Repository . . . . . . . . . . . . . . . . . . . . . . . . 11
6.3. Synchronization between DNS Search List and Resolver
Repository . . . . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7.1. Security Threats . . . . . . . . . . . . . . . . . . . . . 12
7.2. Recommendations . . . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Changes from RFC 6106 . . . . . . . . . . . . . . . . 16
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1. Introduction
The purpose of this document is to standardize IPv6 Router
Advertisement (RA) options (DNS RA options) for DNS Recursive Server
Addresses used for the DNS name resolution in IPv6 hosts, and also
for a DNS Search List of domain suffixes.
Neighbor Discovery (ND) for IP version 6 and IPv6 Stateless Address
Autoconfiguration (SLAAC) provide ways to configure either fixed or
mobile nodes with one or more IPv6 addresses, default routers, and
some other parameters [RFC4861][RFC4862].
It is infeasible to manually configure nomadic hosts each time they
connect to a different network. While a one-time static
configuration is possible, it is generally not desirable on general-
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
recursive name server directly connected to the global DNS.
The DNS information can also be provided through DHCPv6 [RFC3315]
[RFC3736][RFC3646]. However, the access to DNS is a fundamental
requirement for almost all hosts, so IPv6 stateless autoconfiguration
cannot stand on its own as an alternative deployment model in any
practical network without any support for DNS configuration.
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
with the deployment of IPv6-only networks. As a result, this
document defines a mechanism based on DNS RA options to allow IPv6
hosts to perform the automatic DNS configuration.
1.1. Applicability Statements
RA-based DNS configuration is a useful alternative in networks where
an IPv6 host's address is autoconfigured through IPv6 stateless
address autoconfiguration and where there is either no DHCPv6
infrastructure at all or some hosts do not have a DHCPv6 client. The
intention is to enable the full configuration of basic networking
information for hosts without requiring DHCPv6. However, for
networks that need to distribute additional information, DHCPv6 is
likely to be employed. In these networks, RA-based DNS configuration
may not be needed.
RA-based DNS configuration allows an IPv6 host to acquire the DNS
configuration (i.e., DNS recursive server addresses and DNS Search
List) for the link(s) to which the host is connected. Furthermore,
the host learns this DNS configuration from the same RA message that
provides configuration information for the link.
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The advantages and disadvantages of the RA-based approach are
discussed in [RFC4339] along with other approaches, such as the DHCP
and well-known anycast address approaches.
1.2. Coexistence of RA Options and DHCP Options for DNS Configuration
Two protocols exist to configure the DNS information on a host, the
Router Advertisement options specified in this document and the
DHCPv6 options specified in [RFC3646]. They can be used together.
The rules governing the decision to use stateful configuration
mechanisms are specified in [RFC4861]. Hosts conforming to this
specification MUST extract DNS information from Router Advertisement
messages, unless static DNS configuration has been specified by the
user. If there is DNS information available from multiple Router
Advertisements and/or from DHCP, the host MUST maintain an ordered
list of this information as specified in Section 5.3.1.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Terminology
This document uses the terminology defined in [RFC4861] and
[RFC4862]. In addition, four new terms are defined below:
o Recursive DNS Server (RDNSS): Server that provides a recursive DNS
resolution service for translating domain names into IP addresses
or resolving PTR records, as defined in [RFC1034] and [RFC1035].
o RDNSS Option: IPv6 RA option to deliver the RDNSS information to
IPv6 hosts [RFC4861].
o DNS Search List (DNSSL): The list of DNS suffix domain names used
by IPv6 hosts when they perform DNS query searches for short,
unqualified domain names.
o DNSSL Option: IPv6 RA option to deliver the DNSSL information to
IPv6 hosts.
o DNS Repository: Two data structures for managing DNS Configuration
Information in the IPv6 protocol stack in addition to Neighbor
Cache and Destination Cache for Neighbor Discovery [RFC4861]. The
first data structure is the DNS Server List for RDNSS addresses
and the second is the DNS Search List for DNS search domain names.
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o Resolver Repository: Configuration repository with RDNSS addresses
and a DNS Search List that a DNS resolver on the host uses for DNS
name resolution; for example, the Unix resolver file (i.e., /etc/
resolv.conf) and Windows registry.
4. Overview
This document standardizes the ND option called the RDNSS option that
contains the addresses of recursive DNS servers. This document also
standardizes the ND option called the DNSSL option that contains the
Domain Search List. This is to maintain parity with the DHCPv6
options and to ensure that there is necessary functionality to
determine the search domains.
The existing ND message (i.e., Router Advertisement) is used to carry
this information. An IPv6 host can configure the IPv6 addresses of
one or more RDNSSes via RA messages. Through the RDNSS and DNSSL
options, along with the prefix information option based on the ND
protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the
network configuration of its IPv6 address and the DNS information
simultaneously without needing DHCPv6 for the DNS configuration. The
RA options for RDNSS and DNSSL can be used on networks that support
the use of ND.
This approach requires the manual configuration or other automatic
mechanisms (e.g., DHCPv6 or vendor proprietary configuration
mechanisms) to configure the DNS information in routers sending the
advertisements. The automatic configuration of RDNSS addresses and a
DNS Search List in routers is out of scope for this document.
5. Neighbor Discovery Extension
The IPv6 DNS configuration mechanism in this document needs two ND
options in Neighbor Discovery: (i) the Recursive DNS Server (RDNSS)
option and (ii) the DNS Search List (DNSSL) option.
5.1. Recursive DNS Server Option
The RDNSS option contains one or more IPv6 addresses of recursive DNS
servers. All of the addresses share the same Lifetime value. If it
is desirable to have different Lifetime values, multiple RDNSS
options can be used. Figure 1 shows the format of the RDNSS option.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Addresses of IPv6 Recursive DNS Servers :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Recursive DNS Server (RDNSS) Option Format
Fields:
Type 8-bit identifier of the RDNSS option type as assigned
by the IANA: 25
Length 8-bit unsigned integer. The length of the option
(including the Type and Length fields) is in units of
8 octets. The minimum value is 3 if one IPv6 address
is contained in the option. Every additional RDNSS
address increases the length by 2. The Length field
is used by the receiver to determine the number of
IPv6 addresses in the option.
Lifetime 32-bit unsigned integer. The maximum time in
seconds (relative to the time the packet is received)
over which these RDNSS addresses MAY be used for name
resolution. The value of Lifetime SHOULD by default
be at least 3 * MaxRtrAdvInterval where
MaxRtrAdvInterval is the Maximum RA Interval defined
in [RFC4861]. A value of all one bits (0xffffffff)
represents infinity. A value of zero means that the
RDNSS addresses MUST no longer be used.
Addresses of IPv6 Recursive DNS Servers
One or more 128-bit IPv6 addresses of the recursive
DNS servers. The number of addresses is determined
by the Length field. That is, the number of
addresses is equal to (Length - 1) / 2.
Note: The addresses for recursive DNS servers in the RDNSS option
MAY be link-local addresses. Such link-local addresses SHOULD be
registered into the resolver repository along with the
corresponding link zone indices of the links that receive the
RDNSS option(s) for them. The link-local addresses MAY be
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represented in the resolver repository with their link zone
indices in the textual format for scoped addresses as described in
[RFC4007]. When a resolver sends a DNS query message to an RDNSS
identified by a link-local address, it MUST use the corresponding
link.
The rationale of the default value of the Lifetime field is as
follows. Router Lifetime set by AdvDefaultLifetime has the
default of 3 * MaxRtrAdvInterval in [RFC4861], so such a default
or a larger default can allow for the reliability of DNS options
even under the loss of RAs on links with a relatively high rate of
packet loss. Note that the ratio of AdvDefaultLifetime to
MaxRtrAdvInterval is the number of unsolicited multicasted RAs
sent by the router. Since the DNS option entries can survive for
at most three consecutive losses of RAs containing DNS options,
the default value of the Lifetime lets the DNS option entries be
resilient to packet-loss environments.
5.2. DNS Search List Option
The DNSSL option contains one or more domain names of DNS suffixes.
All of the domain names share the same Lifetime value. If it is
desirable to have different Lifetime values, multiple DNSSL options
can be used. Figure 2 shows the format of the DNSSL option.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Domain Names of DNS Search List :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DNS Search List (DNSSL) Option Format
Fields:
Type 8-bit identifier of the DNSSL option type as assigned
by the IANA: 31
Length 8-bit unsigned integer. The length of the option
(including the Type and Length fields) is in units of
8 octets. The minimum value is 2 if at least one
domain name is contained in the option. The Length
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field is set to a multiple of 8 octets to accommodate
all the domain names in the field of Domain Names of
DNS Search List.
Lifetime 32-bit unsigned integer. The maximum time in
seconds (relative to the time the packet is received)
over which these DNSSL domain names MAY be used for
name resolution. The Lifetime value has the same
semantics as with the RDNSS option. That is,
Lifetime SHOULD by default be at least
3 * MaxRtrAdvInterval. A value of all one bits
(0xffffffff) represents infinity. A value of zero
means that the DNSSL domain names MUST no longer be
used.
Domain Names of DNS Search List
One or more domain names of DNS Search List that MUST
be encoded as described in Section 3.1 of [RFC1035].
By this technique, each domain name is represented as
a sequence of labels ending in a zero octet, defined
as domain name representation. For more than one
domain name, the corresponding domain name
representations are concatenated as they are. Note
that for the simple decoding, the domain names MUST
NOT be encoded in a compressed form, as described in
Section 4.1.4 of [RFC1035]. Because the size of this
field MUST be a multiple of 8 octets, for the minimum
multiple including the domain name representations,
the remaining octets other than the encoding parts of
the domain name representations MUST be padded with
zeros.
5.3. Procedure of DNS Configuration
The procedure of DNS configuration through the RDNSS and DNSSL
options is the same as with any other ND option [RFC4861].
5.3.1. Procedure in IPv6 Hosts
When an IPv6 host receives DNS options (i.e., RDNSS and DNSSL
options) through RA messages, it processes the options as follows:
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
than or equal to the minimum value (3), and satisfies that (Length
- 1) % 2 == 0. The value of the Length field in the DNSSL option
is greater than or equal to the minimum value (2). Also, the
validity of the RDNSS option is checked with the "Addresses of
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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
the options into the DNS Repository and the Resolver Repository in
order. Otherwise, the host MUST discard the options. Refer to
Section 6 for the detailed procedure.
In the case where the DNS information of RDNSS and DNSSL can be
obtained from multiple sources, such as RA and DHCP, the IPv6 host
SHOULD keep some DNS options from all sources. Unless explicitly
specified for the discovery mechanism, the exact number of addresses
and domain names to keep is a matter of local policy and
implementation choice as a local configuration option. However, in
the case of multiple 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 SHOULD be stored into the DNS Repository and Resolver
Repository so that information from DHCP appears there first and
therefore takes precedence. Thus, the DNS information from DHCP
takes precedence over that from RA for DNS queries. On the other
hand, for DNS options announced by RA, if some RAs use the Secure
Neighbor Discovery (SEND) protocol [RFC3971] for RA security, they
MUST be preferred over those that do not use SEND. Also, DNS options
announced by RA via SEND MUST be preferred over those announced by
un-authenticated DHCP [RFC3118]. Refer to Section 7 for the detailed
discussion on SEND for DNS RA options.
5.3.2. Warnings for DNS Options Configuration
There are two warnings for DNS options configuration: (i) warning for
multiple sources of DNS options and (ii) warning for multiple network
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
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
DNS queries. As a result, configurations where different information
is provided by different mechanisms for autoconfiguration may lead to
problems. Therefore, the network administrator needs to carefully
configure different DNS options in the multiple mechanisms for
autoconfiguration in order to minimize the impact of such problems
[DHCPv6-SLAAC].
Second, if different DNS information is provided on different network
interfaces, this can lead to inconsistent behavior. The IETF worked
on solving this problem for both DNS and other information obtained
by multiple interfaces [RFC6418][RFC6419], and standardized the
solution for RDNSS selection for multi-interfaced nodes in [RFC6731],
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which is based on DHCP.
6. Implementation Considerations
The implementation considerations in this document include the
following three: (i) DNS repository management, (ii) synchronization
between DNS server list and resolver repository, and (iii)
synchronization between DNS search list and resolver repository.
Note: The implementations that are updated according to this
document will still interoperate with the existing implementations
according to [RFC6106]. This is because the main change of this
document is the increase of the default Lifetime of DNS options,
considering lossy links.
6.1. DNS Repository Management
For DNS repository management, the following two data structures
SHOULD be synchronized with the resolver repository: (i) DNS Server
List that keeps the list of RDNSS 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 RDNSS address (or DNSSL domain
name) and Expiration-time as follows:
o RDNSS address for DNS Server List: IPv6 address of the Recursive
DNS Server which is available for recursive DNS resolution service
in the network advertising the RDNSS option.
o DNSSL domain name for DNS Search List: DNS suffix domain name
which is used to perform DNS query searches for short, unqualified
domain names.
o Expiration-time for DNS Server List or DNS Search List: The time
when this entry becomes invalid. Expiration-time is set to the
value of the Lifetime field of the RDNSS option or DNSSL option
plus the current time. Whenever a new RDNSS option with the same
address (or DNSSL option with the same domain name) is received on
the same interface as a previous RDNSS option (or DNSSL option),
this field is updated to have a new Expiration-time. When the
current time becomes larger than Expiration-time, this entry is
regarded as expired, so it should not be used any more. 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.
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6.2. Synchronization between DNS Server List and Resolver Repository
When an IPv6 host receives the information of multiple RDNSS
addresses within a network (e.g., campus network and company network)
through an RA message with RDNSS option(s), it stores the RDNSS
addresses (in order) into both the DNS Server List and the Resolver
Repository. The processing of the RDNSS consists of (i) 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
follows:
Step (a): Receive and parse the RDNSS option(s). For the RDNSS
addresses in each RDNSS option, perform Steps (b) through (d).
Step (b): For each RDNSS address, check the following: If the
RDNSS address already exists in the DNS Server List and the RDNSS
option's Lifetime field is set to zero, delete the corresponding
RDNSS entry from both the DNS Server List and the Resolver
Repository in order to prevent the RDNSS address from being used
any more for certain reasons in network management, e.g., the
termination of the RDNSS or a renumbering situation. That is, the
RDNSS can resign from its DNS service because the machine running
the RDNSS is out of service intentionally or unintentionally.
Also, under the renumbering situation, the RDNSS's IPv6 address
will be changed, so the previous RDNSS address should not be used
any more. The processing of this RDNSS address is finished here.
Otherwise, go to Step (c).
Step (c): For each RDNSS address, if it already exists in the DNS
Server List and the RDNSS option's Lifetime field is not set to
zero, then just update the value of the Expiration-time field
according to the procedure specified in the third bullet of
Section 6.1. Otherwise, go to Step (d).
Step (d): For each RDNSS address, if it does not exist in the DNS
Server List, register the RDNSS address and Lifetime with the DNS
Server List and then insert the RDNSS address as the first one in
the Resolver Repository. In the case where the data structure for
the DNS Server List is full of RDNSS entries (that is, has more
RDNSSes than the sufficient number discussed in Section 5.3.1),
delete from the DNS Server List the entry with the shortest
Expiration-time (i.e., the entry that will expire first). The
corresponding RDNSS address is also deleted from the Resolver
Repository. For the ordering of RDNSS addresses in an RDNSS
option, position the first RDNSS address in the RDNSS option as
the first one in the Resolver Repository, the second RDNSS address
in the option as the second one in the repository, and so on.
This ordering allows the RDNSS addresses in the RDNSS option to be
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preferred according to their order in the RDNSS option for the DNS
name resolution. The processing of these RDNSS addresses is
finished here.
The handling of expired RDNSSes is as follows: Whenever an entry
expires in the DNS Server List, the expired entry is deleted from the
DNS Server List, and also the RDNSS address corresponding to the
entry is deleted from the Resolver Repository.
6.3. Synchronization between DNS Search List and Resolver Repository
When an IPv6 host receives the information of multiple DNSSL domain
names within a network through an RA message with DNSSL option(s), it
stores the DNSSL domain names (in order) into both the DNS Search
List and the Resolver Repository. The processing of the DNSSL
consists of (i) the processing of DNSSL option(s) included in an RA
message and (ii) the handling of expired DNSSLs. The processing of
DNSSL option(s) is the same with that of RDNSS option(s) in Section
6.2.
7. Security Considerations
In this section, we analyze security threats related to DNS options
and then suggest recommendations to cope with such security threats.
7.1. Security Threats
For the RDNSS option, an attacker could send an RA with a fraudulent
RDNSS address, misleading IPv6 hosts into contacting an unintended
DNS server for DNS name resolution. Also, for the DNSSL option, an
attacker can let IPv6 hosts resolve a host name without a DNS suffix
into an unintended host's IP address with a fraudulent DNS Search
List. These attacks are similar to ND attacks specified in [RFC4861]
that use Redirect or Neighbor Advertisement messages to redirect
traffic to individual addresses of malicious parties.
However, the security of these RA options for DNS configuration does
not affect ND protocol security [RFC4861]. This is because learning
DNS information via the RA options cannot be worse than learning bad
router information via the RA options. Therefore, the vulnerability
of ND is not worse and is a subset of the attacks that any node
attached to a LAN can do.
7.2. Recommendations
The Secure Neighbor Discovery (SEND) protocol [RFC3971] is designed
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
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automatically signed with digital signatures.
It is common for network devices such as switches to include
mechanisms to block unauthorized ports from running a DHCPv6 server
to provide protection from rogue DHCPv6 servers [RFC7610]. That
means that an attacker on other ports cannot insert bogus DNS servers
using DHCPv6. The corresponding technique for network devices is
RECOMMENDED to block rogue Router Advertisement messages including
the RDNSS and DNSSL options from unauthorized nodes [RFC6104]
[RFC6105].
An attacker may provide a bogus DNS Search List option in order to
cause the victim to send DNS queries to a specific DNS server when
the victim queries non-FQDNs (fully qualified domain names). For
this attack, the DNS resolver in IPv6 hosts can mitigate the
vulnerability with the recommendations mentioned in [RFC1535],
[RFC1536], and [RFC3646].
8. IANA Considerations
The RDNSS option defined in this document uses the IPv6 Neighbor
Discovery Option type assigned by the IANA as follows:
Option Name Type
Recursive DNS Server Option 25
The DNSSL option defined in this document uses the IPv6 Neighbor
Discovery Option type assigned by the IANA as follows:
Option Name Type
DNS Search List Option 31
These options are registered in the "Internet Control Message
Protocol version 6 (ICMPv6) Parameters" registry [ICMPv6].
9. Acknowledgements
This document has greatly benefited from inputs by Robert Hinden,
Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik
Nordmark, Dan Wing, Jari Arkko, Ben Campbell, Vincent Roca, Tony
Cheneau, Fernando Gont, Jen Linkova, Ole Troan, Mark Smith, Tatuya
Jinmei, Lorenzo Colitti, Tore Anderson, David Farmer, Bing Liu, and
Tassos Chatzithomaoglou. The authors sincerely appreciate their
contributions.
This document was supported by Institute for Information &
communications Technology Promotion (IITP) grant funded by the Korea
government (MSIP) [10041244, Smart TV 2.0 Software Platform].
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10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H.
Soliman, "Neighbor Discovery for IP version 6
(IPv6)", RFC 4861, September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6
Stateless Address Autoconfiguration", RFC 4862,
September 2007.
[RFC1035] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, November 1987.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E.,
and B. Zill, "IPv6 Scoped Address Architecture",
RFC 4007, March 2005.
10.2. Informative References
[RFC1034] Mockapetris, P., "Domain Names - Concepts and
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.
[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,
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March 2005.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP
Messages", RFC 3118, June 2001.
[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router
Advertisement Problem Statement", RFC 6104,
February 2011.
[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C.,
and J. Mohacsi, "IPv6 Router Advertisement Guard",
RFC 6105, 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.
Miller, "Common DNS Implementation Errors and
Suggested Fixes", RFC 1536, October 1993.
[DHCPv6-SLAAC] Liu, B., Jiang, S., Gong, X., Wang, W., and E. Rey,
"DHCPv6/SLAAC Interaction Problems on Address and DNS
Configuration",
draft-ietf-v6ops-dhcpv6-slaac-problem-07 (work in
progress), August 2016.
[RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and
Provisioning Domains Problem Statement", RFC 6418,
November 2011.
[RFC6419] Wasserman, M. and P. Seite, "Current Practices for
Multiple-Interface Hosts", RFC 6419, November 2011.
[RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved
Recursive DNS Server Selection for Multi-Interfaced
Nodes", RFC 6731, December 2012.
[ICMPv6] ICMPv6 Parameters Registry, "http://www.iana.org/
assignments/icmpv6-parameters/
icmpv6-parameters.xhtml#icmpv6-parameters-5".
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Appendix A. Changes from RFC 6106
The following changes were made from RFC 6106 "IPv6 Router
Advertisement Options for DNS Configuration":
o This document allows a higher default value of the lifetime of the
DNS RA options than RFC 6106 in order to avoid the frequent expiry
of the options on links with a relatively high rate of packet
loss, and also making additional clarifications. The lifetime's
lower bound of 2 * MaxRtrAdvInterval was shown to lead to the
expiry of these options on links with a relatively high rate of
packet loss. This revision relaxes the lower bound and sets a
higher default value of 3 * MaxRtrAdvInterval to avoid this
problem.
o The generation of Router Solicitation to ensure that the RDNSS
information is fresh before the expiry of the RDNSS option is
removed in order to prevent multicast traffic on the link from
increasing.
o The addresses for recursive DNS servers in the RDNSS option can be
not only global addresses, but also link-local addresses. The
link-local addresses for RDNSSes should be registered into the
resolver repository along with the corresponding link zone
indices.
o RFC 6106 recommended that the number of RDNSS addresses that
should be learned and maintained through the RDNSS RA option
should be limited to three. This document removes that
recommendation, thus the number of RDNSS addresses to maintain is
determined by an implementer's local policy.
o RFC 6106 recommended that the number of DNS search domains that
should be learned and maintained through the DNSSL RA option
should be limited to three. This document removes that
recommendation, thus when the set of unique DNSSL values are not
equivalent, none of them may be ignored for hostname lookups
according to an implementer's local policy.
o The guidance of the specific implementation for the
synchronization of the DNS Repository and Resolver Repository on
the kernel space and user space is removed.
o The usage of the keywords of SHOULD and RECOMMENDED in RFC 2119 is
removed in the recommendation of using SEND for secure ND.
Instead of using these keywords, SEND is specified as only a
possible solution for secure ND.
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Authors' Addresses
Jaehoon Paul Jeong
Department of Software
Sungkyunkwan University
2066 Seobu-Ro, Jangan-Gu
Suwon, Gyeonggi-Do 16419
Republic of Korea
Phone: +82 31 299 4957
Fax: +82 31 290 7996
EMail: pauljeong@skku.edu
URI: http://iotlab.skku.edu/people-jaehoon-jeong.php
Soohong Daniel Park
Software R&D Center
Samsung Electronics
Seoul R&D Campus D-Tower, 56, Seongchon-Gil, Seocho-Gu
Seoul 06765
Republic of Korea
EMail: soohong.park@samsung.com
Luc Beloeil
France Telecom R&D
42, rue des coutures
BP 6243
14066 CAEN Cedex 4
France
Phone: +33 2 40 44 97 40
EMail: luc.beloeil@orange-ftgroup.com
Syam Madanapalli
NTT Data
#H304, Shriram Samruddhi, Thubarahalli
Bangalore - 560066
India
Phone: +91 959 175 7926
EMail: smadanapalli@gmail.com
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