Internet DRAFT - draft-jeong-dnsop-ipv6-dns-discovery
draft-jeong-dnsop-ipv6-dns-discovery
Network Working Group J. Jeong, Ed.
Internet-Draft ETRI/University of Minnesota
Intended status: Standards Track S. Park
Expires: November 17, 2007 SAMSUNG Electronics
L. Beloeil
France Telecom R&D
S. Madanapalli
SAMSUNG ISO
May 16, 2007
IPv6 Router Advertisement Option for DNS Configuration
draft-jeong-dnsop-ipv6-dns-discovery-12.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of 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-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on November 17, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document specifies a new IPv6 Router Advertisement option to
allow IPv6 routers to advertise DNS recursive server addresses to
IPv6 hosts.
Jeong, et al. Expires November 17, 2007 [Page 1]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Applicability Statements . . . . . . . . . . . . . . . . . 3
1.2. Coexistence of RDNSS Option and DHCP Option . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5
5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 5
5.2. Procedure of DNS Configuration . . . . . . . . . . . . . . 6
5.2.1. Procedure in IPv6 Host . . . . . . . . . . . . . . . . 6
6. Implementation Considerations . . . . . . . . . . . . . . . . 7
6.1. DNS Server List Management . . . . . . . . . . . . . . . . 7
6.2. Synchronization between DNS Server List and Resolver
Repository . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 13
Jeong, et al. Expires November 17, 2007 [Page 2]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
1. Introduction
Neighbor Discovery (ND) for IP Version 6 and IPv6 Stateless Address
Autoconfiguration provide ways to configure either fixed or mobile
nodes with one or more IPv6 addresses, default routes and some other
parameters [2][3]. To support the access to additional services in
the Internet that are identified by a DNS name, such as a web server,
the configuration of at least one recursive DNS server is also needed
for DNS name resolution.
It is infeasible for nomadic hosts, such as laptops, to have to enter
a DNS resolver each time they connect to a different wireless LAN
(WLAN) such as IEEE 802.11 a/b/g [12]-[15]. Normally, DHCP [6]-[8]
is used to locate such resolvers. This document provides an
alternate, experimental mechanism which uses a new IPv6 Router
Advertisement (RA) option to allow IPv6 routers to advertise DNS
recursive server addresses to IPv6 hosts.
1.1. Applicability Statements
The only standards-track DNS configuration mechanism in the IETF is
DHCP, and its support in hosts and routers is necessary for reasons
of interoperability.
RA-based DNS configuration is a useful, optional alternative in
networks where an IPv6 host's address is autoconfigured through IPv6
stateless address autoconfiguration, and where the delays in
acquiring server addresses and communicating with the servers are
critical. RA-based DNS configuration allows the host to acquire the
nearest server addresses on every link. Furthermore, it learns these
addresses from the same RA message that provides configuration
information for the link, thereby avoiding an additional protocol
run. This can be beneficial in some mobile environments, such as
with Mobile IPv6 [10].
The advantages and disadvantages of the RA-based approach are
discussed in [9] along with other approaches, such as the DHCP and
Well-known anycast addresses approaches.
1.2. Coexistence of RDNSS Option and DHCP Option
The RDNSS option and DHCP option can be used together [9]. To order
the RA and DHCP approaches, the O (Other stateful configuration) flag
can be used in the RA message [2]. If no RDNSS option is included,
an IPv6 host may perform DNS configuration through DHCPv6 [6]-[8]
regardless of whether the O flag is set or not.
Jeong, et al. Expires November 17, 2007 [Page 3]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
2. Definitions
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 [1].
3. Terminology
This document uses the terminology described in [2] and [3]. In
addition, four new terms are defined below:
o Recursive DNS Server (RDNSS): Server which provides a recursive
DNS resolution service for translating domain names into IP
addresses as defined in [4] and [5].
o RDNSS Option: IPv6 RA Option to deliver the RDNSS information to
the IPv6 hosts [2].
o DNS Server List: Data structure for managing DNS Server
Information existing in IPv6 protocol stack in addition to
Neighbor Cache and Destination Cache for Neighbor Discovery [2].
o Resolver Repository: Configuration repository with RDNSS addresses
which a DNS resolver on the host uses for DNS name resolution,
such as Unix resolver file (i.e., /etc/resolv.conf) and Windows
registry.
4. Overview
This document defines a new ND option called RDNSS option that
contains the addresses of recursive DNS servers. Existing ND
transport mechanisms (i.e., advertisements and solicitations) are
used. This works in the same way that hosts learn about routers and
prefixes. An IPv6 host can configure the IPv6 addresses of one or
more RDNSSes via RA message periodically sent by router or solicited
by a Router Solicitation (RS).
Through the RDNSS option along with the prefix information option
based on the ND protocol ([2] and [3]), an IPv6 host can perform its
network configuration of its IPv6 address and RDNSS simultaneously
without needing a separate message exchange for the RDNSS
information. The RA option for RDNSS can be used on any network that
supports the use of ND.
This approach requires RDNSS information to be configured in the
routers sending the advertisements. The configuration of RDNSS
Jeong, et al. Expires November 17, 2007 [Page 4]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
addresses in the routers can be done by manual configuration. The
automatic configuration or redistribution of RDNSS information is
possible by running a DHCPv6 client running on the router [6]-[8].
The automatic configuration of RDNSS addresses in the routers is out
of scope in this document.
5. Neighbor Discovery Extension
The IPv6 DNS configuration mechanism in this document needs a new ND
option in Neighbor Discovery, Recursive DNS Server (RDNSS) option.
5.1. Recursive DNS Server Option
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 RDNSS 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Addresses of IPv6 Recursive DNS Servers :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Recursive DNS Server (RDNSS) Option Format
Fields:
Type 8-bit identifier of the option type (TBD: IANA)
Option Name Type
RDNSS option (TBD)
Length 8-bit unsigned integer. The length of the
option (including the type and length fields)
in units of 8 octets. The minimum value is 0x03
if one IPv6 address is contained in the option.
Every additional RDNSS address increases the
length by 0x02. The length field is used by
the receiver to determine the number of IPv6
addresses in the option.
Jeong, et al. Expires November 17, 2007 [Page 5]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
Lifetime 32-bit unsigned integer. The maximum time, in
seconds (relative to the time the packet is sent),
over which this RDNSS MAY be used for name
resolution. Hosts MAY send a Router Solicitation
to ensure the RDNSS information is fresh before
the interval expires. In order to provide fixed
hosts with the stable DNS service and allow mobile
hosts to prefer local RDNSSes to remote RDNSSes,
the value of lifetime should be at least as long
as the Maximum RA Interval (MaxRtrAdvInterval) in
RFC 2461, and be at most as long as two times
MaxRtrAdvInterval; Lifetime SHOULD be bounded as
follows:
MaxRtrAdvInterval<=Lifetime<=2*MaxRtrAdvInterval.
A value of all one bits (0xffffffff) represents
infinity. A value of zero means that the RDNSS
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.
5.2. Procedure of DNS Configuration
The procedure of DNS configuration through RDNSS option is the same
as any other ND option [2].
5.2.1. Procedure in IPv6 Host
When an IPv6 host receives RDNSS option through RA, it checks whether
the option is valid;
o If the RDNSS option is present, the host SHOULD copy the option's
value into the DNS Server List and the Resolver Repository as long
as the value of Length field is greater than or equal to the
minimum value (0x03). The host MAY ignore additional RDNSS
addresses within an RDNSS option and/or additional RDNSS options
within an RA when it has gathered a sufficient number of RDNSSes.
o If the RDNSS option is present but invalid (e.g., it has the
length less than 0x03), the host SHOULD discard the option.
Jeong, et al. Expires November 17, 2007 [Page 6]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
6. Implementation Considerations
Note
This non-normative section gives some hints for implementing the
processing of RDNSS option in IPv6 host.
For the configuration and management of RDNSS information, the
advertised RDNSS addresses can be stored and managed in both the DNS
Server List and the Resolver Repository.
In environments where the RDNSS information is stored in user space
and ND runs in the kernel, it is necessary to synchronize the DNS
Server List for RDNSSes in kernel space and the Resolver Repository
in user space. For the synchronization, the implementation where ND
works in the kernel should provide the write operation for updating
RDNSS information from the kernel to the Resolver Repository. One
simple approach to perform this is to have a daemon around (or a
program that is called at the defined intervals) that keeps
monitoring the lifetime of RDNSSes all the time. Whenever there is
an expired entry in the DNS Server List, the daemon can delete the
corresponding entry from the Resolver Repository.
6.1. DNS Server List Management
The kernel or user-space process (depending on where RAs are
processed) should maintain a data structure called DNS Server List
which keeps the list of RDNSSes. Each entry of DNS Server List
consists of RDNSS address and Expiration-time as follows:
o RDNSS address: IPv6 address of Recursive DNS Server which is
available for recursive DNS resolution service in the network
advertising the RDNSS option; such a network is called site in
this document.
o Expiration-time: Expiration time field giving the time when this
entry becomes invalid. Expiration-time is set to the value of
Lifetime field of RDNSS option plus the current system time.
Whenever a new RDNSS option with the same address is received,
this field is updated to have a new expiration time. When
Expiration-time becomes less than the current system time, this
entry is regared as expired.
Note
An RDNSS MUST be used only as long as both the RA router lifetime and
Jeong, et al. Expires November 17, 2007 [Page 7]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
the RDNSS option lifetime have not expired. The reason is that the
RDNSS may not be currently reachable or may not provide service to
the host's current address (e.g., due to the network ingress
filtering [16][17]).
6.2. Synchronization between DNS Server List and Resolver Repository
When an IPv6 host receives the information of multiple RDNSSes within
a site 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 option included in
RA message is as follows:
Step (a): Receive and parse RDNSS option(s). For the RDNSS
addresses in each RDNSS option, perform Step (b) through Step (d).
Note that Step (e) is performed whenever an entry expires in the
DNS Server List.
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 let the RDNSS be not used any more for
certain reasons in network management, e.g., the breakdown of the
RDNSS or a renumbering situation. 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, then just update the value of "Expiration-time" field
to have a new expiration time with the RDNSS option's "Lifetime"
field and the current system time. 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 in front of the
Resolver Repository. In the case where the data structure for the
DNS Server List is full of RDNSS entries, delete from the DNS
Server List the entry with the smallest expiration time that will
expire first. The corresponding RDNSS address is also deleted
from the Resolver Repository. In the order in the RDNSS option,
position the newly added RDNSS addresses in the front of the
Resolver Repository so that the RDNSS addresses may be preferred
according to their order in the RDNSS option for the DNS name
resolution. The processing of these RDNSS addresses is finished
here. Note that, in the case where there are several routers
advertising RDNSS option(s) in a subnet, the RDNSSes announced
lately are more preferred.
Jeong, et al. Expires November 17, 2007 [Page 8]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
Step (e): Delete each expired entry from DNS Server List and the
RDNSS address corresponding to the entry from the Resolver
Repository.
7. Security Considerations
The security of RA option for RDNSS might be worse than ND protocol
security [2]. However, any new vulnerability is not known yet in
this RA option. In this context, it can be claimed that the
vulnerability of ND is not worse and is a subset of the attacks that
any node attached to a LAN can do independently of ND. A malicious
node on a LAN can promiscuously receive packets for any router's MAC
address and send packets with the router's MAC address as the source
MAC address in the L2 header. As a result, the L2 switches send
packets addressed to the router to the malicious node. Also, this
attack can send redirects that tell the hosts to send their traffic
somewhere else. The malicious node can send unsolicited RA or NA
replies, answer RS or NS requests, etc. Also, an attacker could
configure a host to send out RA with a fraudulent RDNSS address,
which is presumably an easier avenue of attack than becoming a rogue
router and having to process all traffic for the subnet. It is
necessary to disable the RA RDNSS option in both routers and clients
administratively to avoid this problem. All of this can be done
independently of implementing ND. Therefore, it can be claimed that
the RA option for RDNSS has vulnerabilities similar to those existing
in current mechanisms.
If Secure Neighbor Discovery (SEND) protocol is used as the security
mechanism for ND, all the ND options including RDNSS option are also
automatically included in the signatures [11], so the RDNSS transport
is integrity-protected. However, since any valid SEND node can still
insert RDNSS options, SEND cannot verify who is or is not authorized
to send the options.
8. IANA Considerations
The IANA is requested to assign a new IPv6 Neighbor Discovery Option
type for the RDNSS option defined in this document.
Option Name Type
RDNSS option (TBD)
The IANA registry for these options is:
http://www.iana.org/assignments/icmpv6-parameters
Jeong, et al. Expires November 17, 2007 [Page 9]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
9. Acknowledgements
This draft has greatly benefited from inputs by Robert Hinden, Pekka
Savola, Iljitsch van Beijnum, Brian Haberman and Tim Chown. The
authors appreciate their contribution.
10. References
10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998.
[3] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
10.2. Informative References
[4] Mockapetris, P., "Domain Names - Concepts and Facilities",
RFC 1034, November 1987.
[5] Mockapetris, P., "Domain Names - Implementation and
Specification", RFC 1035, November 1987.
[6] Droms, R., Ed., "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[7] Droms, R., "Stateless Dynamic Host Configuration Protocol
(DHCP) Service for IPv6", RFC 3736, April 2004.
[8] Droms, R., Ed., "DNS Configuration options for Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
December 2003.
[9] Jeong, J., Ed., "IPv6 Host Configuration of DNS Server
Information Approaches", RFC 4339, February 2006.
[10] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[11] Arkko, J., Ed., "SEcure Neighbor Discovery (SEND)", RFC 3971,
March 2005.
[12] ANSI/IEEE Std 802.11, "Part 11: Wireless LAN Medium Access
Jeong, et al. Expires November 17, 2007 [Page 10]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
Control (MAC) and Physical Layer (PHY) Specifications",
March 1999.
[13] IEEE Std 802.11a, "Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) specifications: High-speed
Physical Layer in the 5 GHZ Band", September 1999.
[14] IEEE Std 802.11b, "Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) specifications: Higher-Speed
Physical Layer Extension in the 2.4 GHz Band", September 1999.
[15] IEEE P802.11g/D8.2, "Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY) specifications: Further
Higher Data Rate Extension in the 2.4 GHz Band", April 2003.
[16] Damas, J. and F. Neves, "Preventing Use of Nameservers in
Reflector Attacks",
draft-ietf-dnsop-reflectors-are-evil-03.txt (Work in Progress),
February 2007.
[17] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000.
Authors' Addresses
Jaehoon Paul Jeong (editor)
ETRI/Department of Computer Science and Engineering
University of Minnesota
117 Pleasant Street SE
Minneapolis, MN 55455
USA
Phone: +1 651 587 7774
Fax: +1 612 625 0572
Email: jjeong@cs.umn.edu
URI: http://www.cs.umn.edu/~jjeong/
Jeong, et al. Expires November 17, 2007 [Page 11]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
Soohong Daniel Park
Mobile Platform Laboratory
SAMSUNG Electronics
416 Maetan-3dong, Yeongtong-Gu
Suwon, Gyeonggi-Do 443-742
Korea
Phone: +82 31 200 4508
Email: soohong.park@samsung.com
Luc Beloeil
France Telecom R&D
42, rue des coutures
BP 6243
14066 CAEN Cedex 4
France
Phone: +33 02 3175 9391
Email: luc.beloeil@francetelecom.com
Syam Madanapalli
SAMSUNG India Software Operations
J. P. Techno Park, 3/1
Millers Road
Bangalore 560052
India
Phone: +91 80 51197777
Email: smadanapalli@gmail.com
Jeong, et al. Expires November 17, 2007 [Page 12]
Internet-Draft IPv6 RA Option for DNS Configuration May 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Jeong, et al. Expires November 17, 2007 [Page 13]
