DHCPv6 Dynamic DNS Reconfiguration
draft-wing-dhc-dns-reconfigure-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|
|---|---|---|---|
| Authors | Dan Wing , Tirumaleswar Reddy.K , Prashanth Patil , Mohamed Boucadair | ||
| Last updated | 2013-06-07 | ||
| Replaced by | draft-ietf-dhc-conn-status | ||
| RFC stream | (None) | ||
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| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
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| Send notices to | (None) |
draft-wing-dhc-dns-reconfigure-01
DHC Working Group D. Wing
Internet-Draft T. Reddy
Intended status: Standards Track P. Patil
Expires: December 09, 2013 Cisco
M. Boucadair
France Telecom
June 07, 2013
DHCPv6 Dynamic DNS Reconfiguration
draft-wing-dhc-dns-reconfigure-01
Abstract
Some networks are expected to support IPv4-only, dual-stack, and
IPV6-only hosts at the same time. This makes prioritizing the DNS
servers for hosts tricky due to a heterogeneous mix of protocol
stacks causing optimal behavior to occur only when the host stack re-
initializes. The networks infrastructure is usually well equipped to
be aware of single/dual-stack nature of hosts. This specification
extends DHCPv6 so that a DHCPv6 Relay Agent can dynamically influence
the priority of DNS servers provided to the host, so that the host
can use an optimal DNS server for resolution.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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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."
This Internet-Draft will expire on December 09, 2013.
Copyright Notice
Copyright (c) 2013 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
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(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. DNS_RECONFIG option . . . . . . . . . . . . . . . . . . . . . 3
5. DHCPv6 Relay Agent Behaviour . . . . . . . . . . . . . . . . 4
6. DHCPv6 Server Behaviour . . . . . . . . . . . . . . . . . . . 5
7. Host Tracking . . . . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The default address selection rules [RFC6724] prefers IPv6 over IPv4.
If a dual-stack host is configured to use a DNS64 server, that DNS64
server will synthesize a AAAA response if there is an A record.
Thus, the dual-stack host will always use IPv6 if a DNS lookup was
involved, even if IPv4 could have been used more optimally. If NAT44
and NAT64 are deployed on the same network, it is preferable to use
NAT44 over NAT64 because of scale, performance and application
incompatibility issues (e.g., FTP) [RFC6384]. At the same time,
native IPv6 can still be preferred over IPv4. The DHCPv6 Relay Agent
can observe host characteristics on a network to determine if the
host is IPV4-only, dual-stack or IPV6-only and also determine
transitions from single to dual-stack or vice-versa. In this
document we propose a specification that allows the DHCPv6 Relay
Agent to influence the DHCPv6 Server to send appropriately
prioritized DNS Servers to the client as per host characteristics.
2. Terminology
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].
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DNS server : DNS server using an IPv4-mapped IPv6 address (that is,
an IPv6 address starting with ::ffff:/96 IPv4-mapped prefix). Hosts
can communicate with the DNS server only using IPv4 packets
[RFC6052], section 4.2.
DNS64 server : DNS server using an IPv6 address and synthesizes AAAA
records from A records [RFC6147]
3. Mechanism
This document describes a new DHCPv6 Option that can be used with the
DHCPv6 RECONFIGURE_REQUEST [I-D.ietf-dhc-triggered-reconfigure] by
the DHCPv6 Relay Agent to indicate to the DHCPv6 Server of the
priority of DNS servers to be provided to the specified host. The
DHCPv6 Server then sends a Reconfigure message to the host providing
updated/re-ordered DNS server list as suggested by the Relay Agent.
The idea is for the DHCPv6 Relay Agent to dynamically send the
reconfigure message based on host characteristics.
1. *IPv6-only transition to Dual-Stack* : In case a host is
IPv6-only to start off, it is provided a DNS64 Server. When
transitioning to dual-stack, an IPv4 DNS Server is assigned as a
consequence of obtaining an IPv4 Address. The DHCPv6 Relay Agent
can detect this and send a RECONFIGURE_REQUEST message to the
DHCPv6 Server indicating that the host needs to be provided with
a regular DNS Server followed by DNS64 server. In lieu of this
mechanism, the host would continue to use the DNS64 server until
the host stack reinitializes.
2. *Dual-Stack to IPv6-only* : In case a host is dual-stack, it is
provided with a regular DNS server followed by DNS64 server.
When transitioning to IPv6-only, the DHCPv6 Relay Agent can
detect this and send a RECONFIGURE_REQUEST message to the DHCPv6
Server indicating that the host needs to be assigned a DNS64
server only. In lieu of this mechanism, the host would continue
to use the regular DNS Server which is inaccessible and
eventually time out to fail over to the DNS64 Server. The host
will take additional time to fully initialize causing delays in
connection.
3. *Dual-Stack to IPv4-only* : In case a host is dual-stack, it is
provided with a regualr DNS server followed by DNS64 server.
When transitioning to IPv4-only, no change is required because
the host continues to use regular DNS server.
4. DNS_RECONFIG option
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The DNS_RECONFIG option is to be used only in a RECONFIGURE_REQUEST
message and identifies the query being performed. The option
includes a flag that determines the DNS server list to be provided by
the DHCPv6 server to the respective client.
The option is defined below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_DNS_RECONFIG | Option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Info-flags | |
-----------------------------------------------------------------
OPTION_DNS_RECONFIG : 16-bit option code
Option-length : 16-bit unsigned integer indicating length
in octets of this option
Info-flags : Flag indicating the type of DNS Server
+------+--------------------------------
|Value | Name |
+------+--------------------------------
| 0x01 | IPV6_DNS64_SERV_ONLY |
| 0x02 | IPV6_HIGH_PROI_NORM_SERV |
+------+--------------------------------
IPV6_DNS64_SERV_ONLY - Provide only DNS64 address list to the client.
IPV6_HIGH_PROI_NORM_SERV - Provide DNS address list in this order to the client,
first regular DNS servers and then DNS64 servers.
Figure 1: DNS Reconfigure option message format
5. DHCPv6 Relay Agent Behaviour
DHCPv6 relay agents that implement this specification MUST be
configurable for sending the RECONFIGURE_REQUEST message. The Relay
Agent MUST set the "msg-type" field to RECONFIGURE_REQUEST. The
Relay Agent detects host characteristics using mechanisms discussed
in Section 7. For host transition from IPv6-only to dual-Stack or
IPv4-only to dual-stack Relay Agent will set Info-flags with
IPV6_HIG_PROI_NORM_SERV and for host transition from dual-stack to
IPv6 only Relay-Agent will set Info-flags with IPV6_DNS64_SERV_ONLY.
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6. DHCPv6 Server Behaviour
Upon receiving RECONFIGURE_REQUEST message containing the
DNS_RECONFIG Option, the DHCPv6 server processing is described below
depending on the Info-flag values:
o *IPV6_DNS64_SERV_ONLY* : The DHCPv6 server will select only IPv6
address list of DNS64 recursive name servers to be sent to the
client. The DHCPv6 server will send a reconfigure message to
inform the client that the server has updated configuration
information and the client initiates an Information-request with
the server. The updated configuration will now be sent as part of
Information-request reply by the DHCPv6 server.
o *IPV6_HIGH_PROI_NORM_SERV* : The DHCPv6 server will select DNS
servers in this order, first is the regular DNS servers and then
DNS64 servers. The DHCPv6 server will send a reconfigure message
to inform the client that the server has updated configuration
information and client initiates an Information-request with the
server. The updated configuration will now be sent as part of
Information-request reply by the DHCPv6 server. The order of DNS
servers provided by option OPTION_DNS_SERVERS determines the
preference for use by the DNS client resolver [RFC3646] thus
ensuring higher priority for regular DNS server list followed by
DNS64 servers.
DHCPv6 server will use the mechanism described in
[I-D.ietf-dhc-triggered-reconfigure] to create and send Reconfigure
message. The server will remember this configuration for the life of
the lease.
7. Host Tracking
Relay Agents can actively keep track of all IPv4/IPv6 addresses and
associated lease times assigned to hosts via the respective DHCP
servers. Relay Agents can thus detect transitions from single to
dual-stack and vice-versa efficiently. In addition to this
technique, which is to be primarily used, transitions can also be
detected using snooping mechanisms. Network devices today use
mechanisms such as ARP and NDP snooping to determine host
characteristics such as IPv4/IPv6 - MAC bindings. IPv4/IPv6 and MAC
counters are also used to determine host liveliness. These
mechanisms help determine if a particular IP address family is
inactive, has reverted to using a single stack even though it
initially had dual-stack capabilities and detect active dual-stack
usage after long periods of single-stack activity.
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8. Security Considerations
Security considerations described in
[I-D.ietf-dhc-triggered-reconfigure]are applicable to this mechanism.
9. IANA Considerations
IANA is requested to assign new option codes for OPTION_DNS_RECONFIG
from the option-code space as defined in section "DHCPv6 Options" of
[RFC3315].
10. References
10.1. Normative References
[I-D.ietf-dhc-triggered-reconfigure]
Boucadair, M. and X. Pougnard, "Reconfigure Triggered by
DHCPv6 Relay Agents", draft-ietf-dhc-triggered-
reconfigure-07 (work in progress), May 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC3646] Droms, R., "DNS Configuration options for Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
December 2003.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
April 2011.
[RFC6384] van Beijnum, I., "An FTP Application Layer Gateway (ALG)
for IPv6-to-IPv4 Translation", RFC 6384, October 2011.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012.
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10.2. Informative References
[I-D.wing-behave-dns64-config]
Wing, D., "IPv6-only and Dual Stack Hosts on the Same
Network with DNS64", draft-wing-behave-dns64-config-03
(work in progress), February 2011.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[RFC5007] Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
"DHCPv6 Leasequery", RFC 5007, September 2007.
Authors' Addresses
Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
Tirumaleswar Reddy
Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli
Sarjapur Marathalli Outer Ring Road
Bangalore, Karnataka 560103
India
Email: tireddy@cisco.com
Prashanth Patil
Cisco Systems, Inc.
Bangalore
India
Email: praspati@cisco.com
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Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
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