draft-ietf-6man-rdnss-rfc6106bis-16.txt   rfc8106.txt 
Network Working Group J. Jeong Internet Engineering Task Force (IETF) J. Jeong
Internet-Draft Sungkyunkwan University Request for Comments: 8106 Sungkyunkwan University
Obsoletes: 6106 (if approved) S. Park Obsoletes: 6106 S. Park
Intended status: Standards Track Samsung Electronics Category: Standards Track Samsung Electronics
Expires: August 12, 2017 L. Beloeil ISSN: 2070-1721 L. Beloeil
France Telecom R&D Orange
S. Madanapalli S. Madanapalli
NTT Data NTT Data
February 8, 2017 March 2017
IPv6 Router Advertisement Options for DNS Configuration IPv6 Router Advertisement Options for DNS Configuration
draft-ietf-6man-rdnss-rfc6106bis-16
Abstract Abstract
This document specifies IPv6 Router Advertisement (RA) options This document specifies IPv6 Router Advertisement (RA) options
(called DNS RA options) to allow IPv6 routers to advertise a list of (called "DNS RA options") to allow IPv6 routers to advertise a list
DNS recursive server addresses and a DNS Search List to IPv6 hosts. of DNS Recursive Server Addresses and a DNS Search List to IPv6
hosts.
This document, which obsoletes RFC 6106, defines a higher default This document, which obsoletes RFC 6106, defines a higher default
value of the lifetime of the DNS RA options to reduce the likelihood 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 of expiry of the options on links with a relatively high rate of
packet loss. packet loss.
Status of This Memo Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
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The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at This document is a product of the Internet Engineering Task Force
http://www.ietf.org/shadow.html. (IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on August 12, 2017. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8106.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................3
1.1. Applicability Statements . . . . . . . . . . . . . . . . . 3 1.1. Applicability Statements ...................................3
1.2. Coexistence of RA Options and DHCP Options for DNS 1.2. Coexistence of RA Options and DHCP Options for DNS
Configuration . . . . . . . . . . . . . . . . . . . . . . 4 Configuration ..............................................4
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 2. Requirements Language ...........................................4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology .....................................................4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Overview ........................................................5
5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5 5. Neighbor Discovery Extension ....................................5
5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 5 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. DNS Configuration Procedure ................................8
5.3.1. Procedure in IPv6 Hosts . . . . . . . . . . . . . . . 8 5.3.1. Procedure in IPv6 Hosts .............................9
5.3.2. Warnings for DNS Options Configuration . . . . . . . . 9 5.3.2. Warnings for DNS Options Configuration ..............9
6. Implementation Considerations . . . . . . . . . . . . . . . . 10 6. Implementation Considerations ..................................10
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
Repository . . . . . . . . . . . . . . . . . . . . . . . . 11 Resolver Repository .......................................11
6.3. Synchronization between DNS Search List and Resolver 6.3. Synchronization between DNS Search List and
Repository . . . . . . . . . . . . . . . . . . . . . . . . 12 Resolver 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. References .....................................................14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9.1. Normative References ......................................14
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9.2. Informative References ....................................14
10.2. Informative References . . . . . . . . . . . . . . . . . . 14 Appendix A. Changes from RFC 6106 .................................17
Appendix A. Changes from RFC 6106 . . . . . . . . . . . . . . . . 16 Acknowledgements ..................................................18
Authors' Addresses ................................................19
1. Introduction 1. Introduction
The purpose of this document is to standardize IPv6 Router The purpose of this document is to standardize IPv6 Router
Advertisement (RA) options (DNS RA options) for DNS Recursive Server Advertisement (RA) options (DNS RA options) for DNS Recursive Server
Addresses used for the DNS name resolution in IPv6 hosts, and also Addresses used for DNS name resolution in IPv6 hosts, and also for a
for a DNS Search List of domain suffixes. DNS Search List (DNSSL) of domain suffixes.
Neighbor Discovery (ND) for IP version 6 and IPv6 Stateless Address IPv6 Neighbor Discovery (ND) and IPv6 Stateless Address
Autoconfiguration (SLAAC) provide ways to configure either fixed or Autoconfiguration (SLAAC) provide ways to configure either fixed or
mobile nodes with one or more IPv6 addresses, default routers, and mobile nodes with one or more IPv6 addresses, default routers, and
some other parameters [RFC4861][RFC4862]. some other parameters [RFC4861] [RFC4862].
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
spaces would not be available to the host if it were to run its own namespaces would not be available to the host if it were to run its
recursive name server directly connected to the global DNS. own recursive name server directly connected to the global DNS.
The DNS information can also be provided through DHCPv6 [RFC3315] The DNS information can also be provided through DHCPv6 [RFC3315]
[RFC3736][RFC3646]. However, the access to DNS is a fundamental [RFC3736] [RFC3646]. However, access to DNS is a fundamental
requirement for almost all hosts, so IPv6 stateless autoconfiguration requirement for almost all hosts, so IPv6 SLAAC cannot stand on its
cannot stand on its own as an alternative deployment model in any own as an alternative deployment model in any practical network
practical network without any support for DNS configuration. 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 DNS RA options to allow IPv6 document defines a mechanism based on DNS RA options to allow IPv6
hosts to perform the automatic DNS configuration. hosts to perform automatic DNS configuration.
1.1. Applicability Statements 1.1. Applicability Statements
RA-based DNS configuration is a useful alternative in networks where RA-based DNS configuration is a useful alternative in networks where
an IPv6 host's address is autoconfigured through IPv6 stateless an IPv6 host's address is autoconfigured through IPv6 SLAAC and where
address autoconfiguration and where there is either no DHCPv6 either (i) there is no DHCPv6 infrastructure at all or (ii) some
infrastructure at all or some hosts do not have a DHCPv6 client. The hosts do not have a DHCPv6 client. The intention is to enable the
intention is to enable the full configuration of basic networking full configuration of basic networking information for hosts without
information for hosts without requiring DHCPv6. However, for requiring DHCPv6. However, for networks that need to distribute
networks that need to distribute additional information, DHCPv6 is additional information, DHCPv6 is likely to be employed. In these
likely to be employed. In these networks, RA-based DNS configuration networks, RA-based DNS configuration may not be needed.
may not be needed.
RA-based DNS configuration allows an IPv6 host to acquire the DNS RA-based DNS configuration allows an IPv6 host to acquire the DNS
configuration (i.e., DNS recursive server addresses and DNS Search configuration (i.e., DNS Recursive Server Addresses and the DNSSL)
List) for the link(s) to which the host is connected. Furthermore, for the link(s) to which the host is connected. Furthermore, the
the host learns this DNS configuration from the same RA message that 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 specified in this document and the RA options specified in this document and the DHCPv6 options
DHCPv6 options specified in [RFC3646]. They can be used together. specified in [RFC3646]. They can be used together. The rules
The rules governing the decision to use stateful configuration governing the decision to use stateful configuration mechanisms are
mechanisms are specified in [RFC4861]. Hosts conforming to this specified in [RFC4861]. Hosts conforming to this specification MUST
specification MUST extract DNS information from Router Advertisement extract DNS information from RA messages, unless static DNS
messages, unless static DNS configuration has been specified by the configuration has been specified by the user. If there is DNS
user. If there is DNS information available from multiple Router information available from multiple RAs and/or from DHCP, the host
Advertisements and/or from DHCP, the host MUST maintain an ordered MUST maintain an ordered list of this information as specified in
list of this information as specified in Section 5.3.1. 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 defined in [RFC4861] and This document uses the terminology defined in [RFC4861] and
[RFC4862]. In addition, four new terms are defined below: [RFC4862]. In addition, six new terms are defined below:
o Recursive DNS Server (RDNSS): Server that provides a recursive DNS o Recursive DNS Server (RDNSS): A server that provides a recursive
resolution service for translating domain names into IP addresses DNS resolution service for translating domain names into IP
or resolving PTR records, as defined in [RFC1034] and [RFC1035]. addresses 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: An IPv6 RA option to deliver the RDNSS information
IPv6 hosts [RFC4861]. to 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: An IPv6 RA option to deliver the DNSSL information
IPv6 hosts. to IPv6 hosts.
o DNS Repository: Two data structures for managing DNS Configuration o DNS Repository: Two data structures for managing DNS configuration
Information in the IPv6 protocol stack in addition to Neighbor information in the IPv6 protocol stack, in addition to the
Cache and Destination Cache for Neighbor Discovery [RFC4861]. The Neighbor Cache and Destination Cache for Neighbor Discovery
first data structure is the DNS Server List for RDNSS addresses
and the second is the DNS Search List for DNS search domain names. [RFC4861]. The first data structure is the DNS Server List for
RDNSS addresses, and the second is the DNSSL for DNS search domain
names.
o Resolver Repository: Configuration repository with RDNSS addresses o Resolver Repository: Configuration repository with RDNSS addresses
and a DNS Search List that a DNS resolver on the host uses for DNS and a DNSSL that a DNS resolver on the host uses for DNS name
name resolution; for example, the Unix resolver file (i.e., /etc/ resolution -- for example, the UNIX resolver file (i.e.,
resolv.conf) and Windows registry. /etc/resolv.conf) and the Windows registry.
4. Overview 4. Overview
This document standardizes the ND option called the RDNSS option that This document standardizes an ND option called the "RDNSS option",
contains the addresses of recursive DNS servers. This document also which contains the addresses of RDNSSes. This document also
standardizes the ND option called the DNSSL option that contains the standardizes an ND option called the "DNSSL option", which contains
Domain Search List. This is to maintain parity with the DHCPv6 the DNSSL. This is to maintain parity with the DHCPv6 options and to
options and to ensure that there is necessary functionality to ensure that there is necessary functionality to determine the search
determine the search domains. domains.
The existing ND message (i.e., Router Advertisement) is used to carry The existing ND message (i.e., RA) is used to carry this information.
this information. An IPv6 host can configure the IPv6 addresses of An IPv6 host can configure the IPv6 addresses of one or more RDNSSes
one or more RDNSSes via RA messages. Through the RDNSS and DNSSL via RA messages. Through the RDNSS and DNSSL options, along with the
options, along with the prefix information option based on the ND Prefix Information option based on the ND protocol [RFC4861]
protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the [RFC4862], an IPv6 host can perform the network configuration of its
network configuration of its IPv6 address and the DNS information IPv6 address and the DNS information simultaneously without needing
simultaneously without needing DHCPv6 for the DNS configuration. The DHCPv6 for the DNS configuration. The RA options for RDNSS and DNSSL
RA options for RDNSS and DNSSL can be used on networks that support can be used on networks that support the use of ND.
the use of ND.
This approach requires the manual configuration or other automatic This approach requires manual configuration or automatic mechanisms
mechanisms (e.g., DHCPv6 or vendor proprietary configuration (e.g., DHCPv6 or vendor-proprietary configuration mechanisms) to
mechanisms) to configure the DNS information in routers sending the configure the DNS information in routers sending the advertisements.
advertisements. The automatic configuration of RDNSS addresses and a The automatic configuration of RDNSS addresses and a DNSSL in routers
DNS Search List in routers is out of scope for this document. is out of scope for this document.
5. Neighbor Discovery Extension 5. Neighbor Discovery Extension
The IPv6 DNS configuration mechanism in this document needs two ND The IPv6 DNS configuration mechanism described in this document needs
options in Neighbor Discovery: (i) the Recursive DNS Server (RDNSS) two ND options in Neighbor Discovery: (i) the RDNSS option and
option and (ii) the DNS Search List (DNSSL) option. (ii) the DNSSL option.
5.1. Recursive DNS Server Option 5.1. Recursive DNS Server Option
The RDNSS option contains one or more IPv6 addresses of recursive DNS The RDNSS option contains one or more IPv6 addresses of RDNSSes. All
servers. All of the addresses share the same Lifetime value. If it of the addresses share the same Lifetime value. If it is desirable
is desirable to have different Lifetime values, multiple RDNSS to have different Lifetime values, multiple RDNSS options can be
options can be used. Figure 1 shows the format of the RDNSS option. used. Figure 1 shows the format of the RDNSS option.
0 1 2 3 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 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 | | Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
: Addresses of IPv6 Recursive DNS Servers : : Addresses of IPv6 Recursive DNS Servers :
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Recursive DNS Server (RDNSS) Option Format Figure 1: RDNSS Option Format
Fields: 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 Type 8-bit identifier of the RDNSS option type as assigned by
(including the Type and Length fields) is in units of IANA: 25
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 Length 8-bit unsigned integer. The length of the option
seconds (relative to the time the packet is received) (including the Type and Length fields) is in units of
over which these RDNSS addresses MAY be used for name 8 octets. The minimum value is 3 if one IPv6 address is
resolution. The value of Lifetime SHOULD by default contained in the option. Every additional RDNSS address
be at least 3 * MaxRtrAdvInterval where increases the length by 2. The Length field is used by
MaxRtrAdvInterval is the Maximum RA Interval defined the receiver to determine the number of IPv6 addresses in
in [RFC4861]. A value of all one bits (0xffffffff) the option.
represents infinity. A value of zero means that the
RDNSS addresses MUST no longer be used.
Addresses of IPv6 Recursive DNS Servers Lifetime 32-bit unsigned integer. The maximum time in seconds
One or more 128-bit IPv6 addresses of the recursive (relative to the time the packet is received) over which
DNS servers. The number of addresses is determined these RDNSS addresses MAY be used for name resolution.
by the Length field. That is, the number of The value of Lifetime SHOULD by default be at least
addresses is equal to (Length - 1) / 2. 3 * MaxRtrAdvInterval, where MaxRtrAdvInterval is the
maximum RA interval as 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.
Note: The addresses for recursive DNS servers in the RDNSS option Addresses of IPv6 Recursive DNS Servers
MAY be link-local addresses. Such link-local addresses SHOULD be One or more 128-bit IPv6 addresses of the RDNSSes. The
registered into the resolver repository along with the number of addresses is determined by the Length field.
corresponding link zone indices of the links that receive the That is, the number of addresses is equal to
RDNSS option(s) for them. The link-local addresses MAY be (Length - 1) / 2.
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 Note: The addresses for RDNSSes in the RDNSS option MAY be link-local
follows. Router Lifetime set by AdvDefaultLifetime has the addresses. Such link-local addresses SHOULD be registered in
default of 3 * MaxRtrAdvInterval in [RFC4861], so such a default the Resolver Repository along with the corresponding link zone
or a larger default can allow for the reliability of DNS options indices of the links that receive the RDNSS option(s) for them.
even under the loss of RAs on links with a relatively high rate of The link-local addresses MAY be represented in the Resolver
packet loss. Note that the ratio of AdvDefaultLifetime to Repository with their link zone indices in the textual format
MaxRtrAdvInterval is the number of unsolicited multicasted RAs for scoped addresses as described in [RFC4007]. When a
sent by the router. Since the DNS option entries can survive for resolver sends a DNS query message to an RDNSS identified by a
at most three consecutive losses of RAs containing DNS options, link-local address, it MUST use the corresponding link.
the default value of the Lifetime lets the DNS option entries be
resilient to packet-loss environments. The rationale of the default value of the Lifetime field is as
follows. The Router Lifetime field, set by AdvDefaultLifetime,
has the default of 3 * MaxRtrAdvInterval as specified 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 multicast 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 5.2. DNS Search List Option
The DNSSL option contains one or more domain names of DNS suffixes. 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 All of the domain names share the same Lifetime value. If it is
desirable to have different Lifetime values, multiple DNSSL options desirable to have different Lifetime values, multiple DNSSL options
can be used. Figure 2 shows the format of the DNSSL option. can be used. Figure 2 shows the format of the DNSSL option.
0 1 2 3 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 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 | | Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lifetime | | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
: Domain Names of DNS Search List : : Domain Names of DNS Search List :
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DNSSL Option Format
Figure 2: DNS Search List (DNSSL) Option Format
Fields: 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 Type 8-bit identifier of the DNSSL option type as assigned by
(including the Type and Length fields) is in units of IANA: 31
8 octets. The minimum value is 2 if at least one
domain name is contained in the option. The Length
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 Length 8-bit unsigned integer. The length of the option
seconds (relative to the time the packet is received) (including the Type and Length fields) is in units of
over which these DNSSL domain names MAY be used for 8 octets. The minimum value is 2 if at least one domain
name resolution. The Lifetime value has the same name is contained in the option. The Length field is set
semantics as with the RDNSS option. That is, to a multiple of 8 octets to accommodate all the domain
Lifetime SHOULD by default be at least names in the "Domain Names of DNS Search List" field.
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 Lifetime 32-bit unsigned integer. The maximum time in seconds
One or more domain names of DNS Search List that MUST (relative to the time the packet is received) over which
be encoded as described in Section 3.1 of [RFC1035]. these DNSSL domain names MAY be used for name resolution.
By this technique, each domain name is represented as The Lifetime value has the same semantics as the
a sequence of labels ending in a zero octet, defined semantics for the RDNSS option. That is, Lifetime SHOULD
as domain name representation. For more than one by default be at least 3 * MaxRtrAdvInterval. A value of
domain name, the corresponding domain name all one bits (0xffffffff) represents infinity. A value
representations are concatenated as they are. Note of zero means that the DNSSL domain names MUST no longer
that for the simple decoding, the domain names MUST be used.
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 Domain Names of DNS Search List
One or more domain names of the DNSSL that MUST be
encoded as described in Section 3.1 of [RFC1035]. With
this technique, each domain name is represented as a
sequence of labels ending in a zero octet, defined as a
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 the
compressed form 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.
The procedure of DNS configuration through the RDNSS and DNSSL 5.3. DNS Configuration Procedure
options is the same as with any other ND option [RFC4861].
The procedure for DNS configuration through the RDNSS and DNSSL
options is the same as it is with any other ND option [RFC4861].
5.3.1. Procedure in IPv6 Hosts 5.3.1. Procedure in IPv6 Hosts
When an IPv6 host receives DNS options (i.e., RDNSS and DNSSL When an IPv6 host receives DNS options (i.e., RDNSS and DNSSL
options) through RA messages, it processes the options as follows: options) 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;
is, the value of the Length field in the RDNSS option is greater that is, the value of the Length field in the RDNSS option is
than or equal to the minimum value (3), and satisfies that (Length greater than or equal to the minimum value (3) and satisfies the
- 1) % 2 == 0. The value of the Length field in the DNSSL option requirement that (Length - 1) % 2 == 0. The value of the Length
is greater than or equal to the minimum value (2). Also, the field in the DNSSL option is greater than or equal to the minimum
validity of the RDNSS option is checked with the "Addresses of value (2). Also, the validity of the RDNSS option is checked with
IPv6 Recursive DNS Servers" field; that is, the addresses should the "Addresses of IPv6 Recursive DNS Servers" field; that is, the
be unicast addresses. 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 information of RDNSS and DNSSL can be 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 obtained from multiple sources, such as RAs and DHCP, the IPv6 host
SHOULD keep some DNS options from all sources. Unless explicitly SHOULD keep some DNS options from all sources. Unless explicitly
specified for the discovery mechanism, the exact number of addresses specified for the discovery mechanism, the exact number of addresses
and domain names to keep is a matter of local policy and and domain names to keep is a matter of local policy and
implementation choice as a local configuration option. However, in implementation choice as a local configuration option. However, in
the case of multiple sources, the ability to store a total of at the case of multiple sources, the ability to store a total of at
least three RDNSS addresses (or DNSSL domain names) from the multiple least three RDNSS addresses (or DNSSL domain names) from the multiple
sources is RECOMMENDED. The DNS options from Router Advertisements sources is RECOMMENDED. The DNS options from RAs and DHCP SHOULD be
and DHCP SHOULD be stored into the DNS Repository and Resolver stored in the DNS Repository and Resolver Repository so that
Repository so that information from DHCP appears there first and information from DHCP appears there first and therefore takes
therefore takes precedence. Thus, the DNS information from DHCP precedence. Thus, the DNS information from DHCP takes precedence
takes precedence over that from RA for DNS queries. On the other over that from RAs for DNS queries. On the other hand, for DNS
hand, for DNS options announced by RA, if some RAs use the Secure options announced by RAs, if some RAs use the Secure Neighbor
Neighbor Discovery (SEND) protocol [RFC3971] for RA security, they Discovery (SEND) protocol [RFC3971] for RA security, they MUST be
MUST be preferred over those that do not use SEND. Also, DNS options preferred over those that do not use SEND. Also, DNS options
announced by RA via SEND MUST be preferred over those announced by announced by RAs via SEND MUST be preferred over those announced by
un-authenticated DHCP [RFC3118]. Refer to Section 7 for the detailed unauthenticated DHCP [RFC3118]. Refer to Section 7 for a detailed
discussion on SEND for DNS RA options. discussion of SEND for DNS RA 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., RAs and DHCP), an IPv6 host can configure its IP addresses
these sources. In this case, it is not possible to control how the from these sources. In this case, it is not possible to control how
host uses DNS information and what source addresses it uses to send the host uses DNS information and what source addresses it uses to
DNS queries. As a result, configurations where different information send DNS queries. As a result, configurations where different
is provided by different mechanisms for autoconfiguration may lead to information is provided by different mechanisms for autoconfiguration
problems. Therefore, the network administrator needs to carefully may lead to problems. Therefore, the network administrator needs to
configure different DNS options in the multiple mechanisms for carefully configure different DNS options in the multiple mechanisms
autoconfiguration in order to minimize the impact of such problems for autoconfiguration in order to minimize the impact of such
[DHCPv6-SLAAC]. 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 from multiple interfaces [RFC6418] [RFC6419] and standardized a
solution for RDNSS selection for multi-interfaced nodes in [RFC6731], DHCP-based solution for RDNSS selection for multi-interfaced nodes as
which is based on DHCP. described in [RFC6731].
6. Implementation Considerations 6. Implementation Considerations
The implementation considerations in this document include the The implementation considerations in this document include the
following three: (i) DNS repository management, (ii) synchronization following three: (i) DNS repository management, (ii) synchronization
between DNS server list and resolver repository, and (iii) between the DNS Server List and the Resolver Repository, and
synchronization between DNS search list and resolver repository. (iii) synchronization between the DNSSL and the Resolver Repository.
Note: The implementations that are updated according to this Note: The implementations that are updated according to this document
document will still interoperate with the existing implementations will still interoperate with the existing implementations
according to [RFC6106]. This is because the main change of this according to [RFC6106]. This is because the main change in
document is the increase of the default Lifetime of DNS options, this document is the increase of the default Lifetime of DNS
considering lossy links. options, considering lossy links.
6.1. DNS Repository Management 6.1. DNS Repository Management
For DNS repository management, the following two data structures For DNS repository management, the following two data structures
SHOULD be synchronized with the resolver repository: (i) DNS Server SHOULD be synchronized with the Resolver Repository: (i) the DNS
List that keeps the list of RDNSS addresses and (ii) DNS Search List Server List, which keeps the list of RDNSS addresses and (ii) the
that keeps the list of DNS search domain names. Each entry in these DNSSL, which keeps the list of DNS search domain names. Each entry
two lists consists of a pair of an RDNSS address (or DNSSL domain in these two lists consists of a pair of an RDNSS address (or DNSSL
name) and Expiration-time as follows: 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 RDNSS that
DNS Server which is available for recursive DNS resolution service is available for recursive DNS resolution service in the network
in the network advertising the RDNSS option. advertising the RDNSS option.
o DNSSL domain name for DNS Search List: DNS suffix domain name o DNSSL domain name for DNSSL: DNS suffix domain name that is used
which is used to perform DNS query searches for short, unqualified to perform DNS query searches for short, unqualified domain names.
domain names.
o Expiration-time for DNS Server List or DNS Search List: The time o Expiration-time for DNS Server List or DNSSL: The time when this
when this entry becomes invalid. Expiration-time is set to the entry becomes invalid. Expiration-time is set to the value of the
value of the Lifetime field of the RDNSS option or DNSSL option Lifetime field of the RDNSS option or DNSSL option plus the
plus the current time. Whenever a new RDNSS option with the same current time. Whenever a new RDNSS option with the same address
address (or DNSSL option with the same domain name) is received on (or DNSSL option with the same domain name) is received on the
the same interface as a previous RDNSS option (or DNSSL option), same interface as a previous RDNSS option (or DNSSL option), this
this field is updated to have a new Expiration-time. When the field is updated to have a new Expiration-time. When the current
current time becomes larger than Expiration-time, this entry is time becomes larger than Expiration-time, this entry is regarded
regarded as expired, so it should not be used any more. Note that as expired, so it should not be used any more. Note that the DNS
the DNS information for the RDNSS and DNSSL options need not be information for the RDNSS and DNSSL options need not be dropped if
dropped if the expiry of the RA router lifetime happens. This is the expiry of the RA router lifetime happens. This is because
because these options have their own lifetime values. 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) in 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
follows: follows:
Step (a): Receive and parse the RDNSS option(s). For the RDNSS o Step (a): Receive and parse the RDNSS option(s). For the RDNSS
addresses in each RDNSS option, perform Steps (b) through (d). addresses in each RDNSS option, perform Steps (b) through (d).
Step (b): For each RDNSS address, check the following: If the o Step (b): For each RDNSS address, check the following: If the
RDNSS address already exists in the DNS Server List and the RDNSS RDNSS address already exists in the DNS Server List and the RDNSS
option's Lifetime field is set to zero, delete the corresponding option's Lifetime field is set to zero, delete the corresponding
RDNSS entry from both the DNS Server List and the Resolver RDNSS entry from both the DNS Server List and the Resolver
Repository in order to prevent the RDNSS address from being used Repository in order to prevent the RDNSS address from being used
any more for certain reasons in network management, e.g., the any more for certain reasons in network management, e.g., the
termination of the RDNSS or a renumbering situation. That is, the termination of the RDNSS or a renumbering scenario. That is, the
RDNSS can resign from its DNS service because the machine running RDNSS can resign from its DNS service because the machine running
the RDNSS is out of service intentionally or unintentionally. the RDNSS is out of service intentionally or unintentionally.
Also, under the renumbering situation, the RDNSS's IPv6 address Also, in the renumbering scenario, the RDNSS's IPv6 address will
will be changed, so the previous RDNSS address should not be used be changed, so the previous RDNSS address should not be used any
any more. The processing of this RDNSS address is finished here. more. The processing of this RDNSS address is finished here.
Otherwise, go to Step (c). Otherwise, go to Step (c).
Step (c): For each RDNSS address, if it already exists in the DNS o 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 Server List and the RDNSS option's Lifetime field is not set to
zero, then just update the value of the Expiration-time field zero, then just update the value of the Expiration-time field
according to the procedure specified in the third bullet of according to the procedure specified in the third bullet of
Section 6.1. Otherwise, go to Step (d). Section 6.1. Otherwise, go to Step (d).
Step (d): For each RDNSS address, if it does not exist in the DNS o 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, register the RDNSS address and Lifetime with the DNS
Server List and then insert the RDNSS address as the first one in 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 Resolver Repository. In the case where the data structure for
the DNS Server List is full of RDNSS entries (that is, has more the DNS Server List is full of RDNSS entries (that is, has more
RDNSSes than the sufficient number discussed in Section 5.3.1), RDNSSes than the sufficient number discussed in Section 5.3.1),
delete from the DNS Server List the entry with the shortest delete from the DNS Server List the entry with the shortest
Expiration-time (i.e., the entry that will expire first). The Expiration-time (i.e., the entry that will expire first). The
corresponding RDNSS address is also deleted from the Resolver corresponding RDNSS address is also deleted from the Resolver
Repository. For the ordering of RDNSS addresses in an RDNSS Repository. For the ordering of RDNSS addresses in an RDNSS
option, position the first RDNSS address in the RDNSS option as option, position the first RDNSS address in the RDNSS option as
the first one in the Resolver Repository, the second RDNSS address the first one in the Resolver Repository, the second RDNSS address
in the option as the second one in the repository, and so on. 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 This ordering allows the RDNSS addresses in the RDNSS option to be
preferred according to their order in the RDNSS option for the DNS preferred according to their order in the RDNSS option for DNS
name resolution. The processing of these RDNSS addresses is name resolution. The processing of these RDNSS addresses is
finished here. finished here.
The handling of expired RDNSSes is as follows: Whenever an entry The handling of expired RDNSSes is as follows: Whenever an entry
expires in the DNS Server List, the expired entry is deleted from the expires in the DNS Server List, the expired entry is deleted from the
DNS Server List, and also the RDNSS address corresponding to the DNS Server List, and also the RDNSS address corresponding to the
entry is deleted from the Resolver Repository. entry is deleted from the Resolver Repository.
6.3. Synchronization between DNS Search List and Resolver Repository 6.3. Synchronization between DNS Search List and Resolver Repository
When an IPv6 host receives the information of multiple DNSSL domain When an IPv6 host receives the information of multiple DNSSL domain
names within a network through an RA message with DNSSL option(s), it 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 stores the DNSSL domain names (in order) in both the DNSSL and the
List and the Resolver Repository. The processing of the DNSSL Resolver Repository. The processing of the DNSSL consists of (i) the
consists of (i) the processing of DNSSL option(s) included in an RA processing of DNSSL option(s) included in an RA message and (ii) the
message and (ii) the handling of expired DNSSLs. The processing of handling of expired DNSSLs. The processing of DNSSL option(s) is the
DNSSL option(s) is the same with that of RDNSS option(s) in Section same as the processing of RDNSS option(s) as described in
6.2. Section 6.2.
7. Security Considerations 7. Security Considerations
In this section, we analyze security threats related to DNS options In this section, we analyze security threats related to DNS options
and then suggest recommendations to cope with such security threats. and then make recommendations to cope with such security threats.
7.1. Security Threats 7.1. Security Threats
For the RDNSS option, an attacker could send an RA with a fraudulent For the RDNSS option, an attacker could send an RA with a fraudulent
RDNSS address, misleading IPv6 hosts into contacting an unintended RDNSS address, misleading IPv6 hosts into contacting an unintended
DNS server for DNS name resolution. Also, for the DNSSL option, an 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 attacker can let IPv6 hosts resolve a hostname without a DNS suffix
into an unintended host's IP address with a fraudulent DNS Search into an unintended host's IP address with a fraudulent DNSSL. These
List. These attacks are similar to ND attacks specified in [RFC4861] attacks are similar to ND attacks specified in [RFC4861] that use
that use Redirect or Neighbor Advertisement messages to redirect Redirect or Neighbor Advertisement messages to redirect traffic to
traffic to individual addresses of malicious parties. 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. attached to a LAN can do.
7.2. Recommendations 7.2. Recommendations
The Secure Neighbor Discovery (SEND) protocol [RFC3971] is designed The Secure Neighbor Discovery (SEND) protocol [RFC3971] is designed
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
automatically signed with digital signatures. be automatically signed with digital signatures.
It is common for network devices such as switches to include It is common for network devices such as switches to include
mechanisms to block unauthorized ports from running a DHCPv6 server mechanisms to block unauthorized ports from running a DHCPv6 server
to provide protection from rogue DHCPv6 servers [RFC7610]. That to provide protection from rogue DHCPv6 servers [RFC7610]. That
means that an attacker on other ports cannot insert bogus DNS servers means that an attacker on other ports cannot insert bogus DNS servers
using DHCPv6. The corresponding technique for network devices is using DHCPv6. The corresponding technique for network devices is
RECOMMENDED to block rogue Router Advertisement messages including RECOMMENDED to block rogue RA messages that include the RDNSS and
the RDNSS and DNSSL options from unauthorized nodes [RFC6104] DNSSL options from unauthorized nodes [RFC6104] [RFC6105].
[RFC6105].
An attacker may provide a bogus DNS Search List option in order to An attacker may provide a bogus DNSSL option in order to cause the
cause the victim to send DNS queries to a specific DNS server when victim to send DNS queries to a specific DNS server when the victim
the victim queries non-FQDNs (fully qualified domain names). For queries non-FQDNs (fully qualified domain names). For this attack,
this attack, the DNS resolver in IPv6 hosts can mitigate the the DNS resolver in IPv6 hosts can mitigate the vulnerability with
vulnerability with the recommendations mentioned in [RFC1535], the recommendations mentioned in [RFC1535], [RFC1536], and [RFC3646].
[RFC1536], and [RFC3646].
8. IANA Considerations 8. IANA Considerations
The RDNSS option defined in this document uses the IPv6 Neighbor The RDNSS option defined in this document uses the IPv6 Neighbor
Discovery Option type assigned by the IANA as follows: Discovery Option type assigned by IANA as follows:
Option Name Type Option Name Type
Recursive DNS Server Option 25 -----------------------------------
Recursive DNS Server Option 25
The DNSSL option defined in this document uses the IPv6 Neighbor The DNSSL option defined in this document uses the IPv6 Neighbor
Discovery Option type assigned by the IANA as follows: Discovery Option type assigned by 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, Option Name Type
Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik -----------------------------------
Nordmark, Dan Wing, Jari Arkko, Ben Campbell, Vincent Roca, Tony DNS Search List Option 31
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 & These options are registered in the "IPv6 Neighbor Discovery Option
communications Technology Promotion (IITP) grant funded by the Korea Formats" registry [ICMPv6].
government (MSIP) [10041244, Smart TV 2.0 Software Platform].
10. References 9. References
10.1. Normative References 9.1. 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,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
Soliman, "Neighbor Discovery for IP version 6 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
(IPv6)", RFC 4861, September 2007. DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Stateless Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
September 2007. DOI 10.17487/RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>.
[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, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
and B. Zill, "IPv6 Scoped Address Architecture", B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
RFC 4007, March 2005. DOI 10.17487/RFC4007, March 2005,
<http://www.rfc-editor.org/info/rfc4007>.
10.2. Informative References 9.2. Informative References
[RFC1034] Mockapetris, P., "Domain Names - Concepts and [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
Facilities", STD 13, RFC 1034, November 1987. STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration C., and M. Carney, "Dynamic Host Configuration Protocol
Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315,
July 2003, <http://www.rfc-editor.org/info/rfc3315>.
[RFC3736] Droms, R., "Stateless Dynamic Host Configuration [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol
Protocol (DHCP) Service for IPv6", RFC 3736, (DHCP) Service for IPv6", RFC 3736, DOI 10.17487/RFC3736,
April 2004. April 2004, <http://www.rfc-editor.org/info/rfc3736>.
[RFC3646] Droms, R., "DNS Configuration options for Dynamic [RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)", Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
RFC 3646, December 2003. DOI 10.17487/RFC3646, December 2003,
<http://www.rfc-editor.org/info/rfc3646>.
[RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, [RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS "IPv6 Router Advertisement Options for DNS Configuration",
Configuration", RFC 6106, November 2010. RFC 6106, DOI 10.17487/RFC6106, November 2010,
<http://www.rfc-editor.org/info/rfc6106>.
[RFC4339] Jeong, J., "IPv6 Host Configuration of DNS Server [RFC4339] Jeong, J., Ed., "IPv6 Host Configuration of DNS Server
Information Approaches", RFC 4339, February 2006. Information Approaches", RFC 4339, DOI 10.17487/RFC4339,
February 2006, <http://www.rfc-editor.org/info/rfc4339>.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971, "SEcure Neighbor Discovery (SEND)", RFC 3971,
March 2005. DOI 10.17487/RFC3971, March 2005,
<http://www.rfc-editor.org/info/rfc3971>.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP [RFC3118] Droms, R., Ed., and W. Arbaugh, Ed., "Authentication for
Messages", RFC 3118, June 2001. DHCP Messages", RFC 3118, DOI 10.17487/RFC3118, June 2001,
<http://www.rfc-editor.org/info/rfc3118>.
[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router [RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
Advertisement Problem Statement", RFC 6104, Problem Statement", RFC 6104, DOI 10.17487/RFC6104,
February 2011. February 2011, <http://www.rfc-editor.org/info/rfc6104>.
[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
and J. Mohacsi, "IPv6 Router Advertisement Guard", Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
RFC 6105, February 2011. DOI 10.17487/RFC6105, February 2011,
<http://www.rfc-editor.org/info/rfc6105>.
[RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6- [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield:
Shield: Protecting against Rogue DHCPv6 Servers", Protecting against Rogue DHCPv6 Servers", BCP 199,
RFC 7610, August 2015. RFC 7610, DOI 10.17487/RFC7610, August 2015,
<http://www.rfc-editor.org/info/rfc7610>.
[RFC1535] Gavron, E., "A Security Problem and Proposed [RFC1535] Gavron, E., "A Security Problem and Proposed Correction
Correction With Widely Deployed DNS Software", With Widely Deployed DNS Software", RFC 1535,
RFC 1535, October 1993. DOI 10.17487/RFC1535, October 1993,
<http://www.rfc-editor.org/info/rfc1535>.
[RFC1536] Kumar, A., Postel, J., Neuman, C., Danzig, P., and S. [RFC1536] Kumar, A., Postel, J., Neuman, C., Danzig, P., and S.
Miller, "Common DNS Implementation Errors and Miller, "Common DNS Implementation Errors and Suggested
Suggested Fixes", RFC 1536, October 1993. Fixes", RFC 1536, DOI 10.17487/RFC1536, October 1993,
<http://www.rfc-editor.org/info/rfc1536>.
[DHCPv6-SLAAC] Liu, B., Jiang, S., Gong, X., Wang, W., and E. Rey, [DHCPv6-SLAAC]
"DHCPv6/SLAAC Interaction Problems on Address and DNS Liu, B., Jiang, S., Gong, X., Wang, W., and E. Rey,
Configuration", "DHCPv6/SLAAC Interaction Problems on Address and
draft-ietf-v6ops-dhcpv6-slaac-problem-07 (work in DNS Configuration", Work in Progress,
progress), August 2016. draft-ietf-v6ops-dhcpv6-slaac-problem-07, August 2016.
[RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and [RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and
Provisioning Domains Problem Statement", RFC 6418, Provisioning Domains Problem Statement", RFC 6418,
November 2011. DOI 10.17487/RFC6418, November 2011,
<http://www.rfc-editor.org/info/rfc6418>.
[RFC6419] Wasserman, M. and P. Seite, "Current Practices for [RFC6419] Wasserman, M. and P. Seite, "Current Practices for
Multiple-Interface Hosts", RFC 6419, November 2011. Multiple-Interface Hosts", RFC 6419, DOI 10.17487/RFC6419,
November 2011, <http://www.rfc-editor.org/info/rfc6419>.
[RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved [RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved
Recursive DNS Server Selection for Multi-Interfaced Recursive DNS Server Selection for Multi-Interfaced
Nodes", RFC 6731, December 2012. Nodes", RFC 6731, DOI 10.17487/RFC6731, December 2012,
<http://www.rfc-editor.org/info/rfc6731>.
[ICMPv6] ICMPv6 Parameters Registry, "http://www.iana.org/ [ICMPv6] IANA, "Internet Control Message Protocol version 6
assignments/icmpv6-parameters/ (ICMPv6) Parameters",
icmpv6-parameters.xhtml#icmpv6-parameters-5". <http://www.iana.org/assignments/icmpv6-parameters/>.
Appendix A. 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 This document allows a higher default value of the lifetime of the 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 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 of the options on links with a relatively high rate of packet
loss, and also making additional clarifications. The lifetime's loss; at the same time, this document also makes additional
lower bound of 2 * MaxRtrAdvInterval was shown to lead to the clarifications. The lifetime's lower bound of
expiry of these options on links with a relatively high rate of 2 * MaxRtrAdvInterval was shown to lead to the expiry of these
packet loss. This revision relaxes the lower bound and sets a options on links with a relatively high rate of packet loss. To
higher default value of 3 * MaxRtrAdvInterval to avoid this avoid this problem, this revision relaxes the lower bound and sets
problem. a higher default value of 3 * MaxRtrAdvInterval.
o The generation of Router Solicitation to ensure that the RDNSS o The text regarding the generation of a Router Solicitation message
information is fresh before the expiry of the RDNSS option is to ensure that the RDNSS information is fresh before the expiry of
removed in order to prevent multicast traffic on the link from the RDNSS option is removed in order to prevent multicast traffic
increasing. on the link from increasing.
o The addresses for recursive DNS servers in the RDNSS option can be o The addresses for RDNSSes in the RDNSS option can be not only
not only global addresses, but also link-local addresses. The global addresses but also link-local addresses. The link-local
link-local addresses for RDNSSes should be registered into the addresses for RDNSSes should be registered in the Resolver
resolver repository along with the corresponding link zone Repository along with the corresponding link zone indices.
indices.
o RFC 6106 recommended that the number of RDNSS addresses that o RFC 6106 recommended that the number of RDNSS addresses that
should be learned and maintained through the RDNSS RA option should be learned and maintained through the RDNSS RA option
should be limited to three. This document removes that should be limited to three. This document removes that
recommendation, thus the number of RDNSS addresses to maintain is recommendation; thus, the number of RDNSS addresses to maintain is
determined by an implementer's local policy. determined by an implementer's local policy.
o RFC 6106 recommended that the number of DNS search domains that o RFC 6106 recommended that the number of DNS search domains that
should be learned and maintained through the DNSSL RA option should be learned and maintained through the DNSSL RA option
should be limited to three. This document removes that should be limited to three. This document removes that
recommendation, thus when the set of unique DNSSL values are not recommendation; thus, when the set of unique DNSSL values are not
equivalent, none of them may be ignored for hostname lookups equivalent, none of them may be ignored for hostname lookups
according to an implementer's local policy. according to an implementer's local policy.
o The guidance of the specific implementation for the o The guidance of the specific implementation for the
synchronization of the DNS Repository and Resolver Repository on synchronization of the DNS Repository and Resolver Repository in
the kernel space and user space is removed. the kernel space and user space is removed.
o The usage of the keywords of SHOULD and RECOMMENDED in RFC 2119 is o The key words "SHOULD" and "RECOMMENDED" (RFC 2119) are removed in
removed in the recommendation of using SEND for secure ND. the recommendation of using SEND as a security mechanism for ND.
Instead of using these keywords, SEND is specified as only a Instead of using these key words, SEND is specified as only a
possible solution for secure ND. possible security mechanism for ND.
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 an Institute for Information &
communications Technology Promotion (IITP) grant funded by the Korean
government (MSIP) [10041244, Smart TV 2.0 Software Platform].
Authors' Addresses Authors' Addresses
Jaehoon Paul Jeong Jaehoon Paul Jeong
Department of Software Department of Software
Sungkyunkwan University Sungkyunkwan University
2066 Seobu-Ro, Jangan-Gu 2066 Seobu-Ro, Jangan-Gu
Suwon, Gyeonggi-Do 16419 Suwon, Gyeonggi-Do 16419
Republic of Korea Republic of Korea
Phone: +82 31 299 4957 Phone: +82 31 299 4957
Fax: +82 31 290 7996 Fax: +82 31 290 7996
EMail: pauljeong@skku.edu Email: pauljeong@skku.edu
URI: http://iotlab.skku.edu/people-jaehoon-jeong.php URI: http://iotlab.skku.edu/people-jaehoon-jeong.php
Soohong Daniel Park Soohong Daniel Park
Software R&D Center Software R&D Center
Samsung Electronics Samsung Electronics
Seoul R&D Campus D-Tower, 56, Seongchon-Gil, Seocho-Gu Seoul R&D Campus D-Tower, 56, Seongchon-Gil, Seocho-Gu
Seoul 06765 Seoul 06765
Republic of Korea Republic of Korea
EMail: soohong.park@samsung.com Email: soohong.park@samsung.com
Luc Beloeil Luc Beloeil
France Telecom R&D Orange
42, rue des coutures 5 rue Maurice Sibille
BP 6243 BP 44211
14066 CAEN Cedex 4 44042 Nantes Cedex 1
France France
Phone: +33 2 40 44 97 40 Phone: +33 2 28 56 11 84
EMail: luc.beloeil@orange-ftgroup.com Email: luc.beloeil@orange.com
Syam Madanapalli Syam Madanapalli
NTT Data NTT Data
#H304, Shriram Samruddhi, Thubarahalli #H304, Shriram Samruddhi, Thubarahalli
Bangalore - 560066 Bangalore 560066
India India
Phone: +91 959 175 7926 Phone: +91 959 175 7926
EMail: smadanapalli@gmail.com Email: smadanapalli@gmail.com
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