Behave WG J. Korhonen
Internet-Draft Nokia Siemens Networks
Intended status: Standards Track T. Savolainen, Ed.
Expires: March 28, 2011 Nokia
September 24, 2010
EDNS0 Option for Indicating AAAA Record Synthesis and Format
draft-korhonen-edns0-synthesis-flag-01.txt
Abstract
Advanced hosts and applications benefit of the knowledge of an IPv6
address, AAAA record, synthesis taking place in the network. This
draft proposes new ENDS0 option for communicating the synthesis is
taking place, used address format, and the IPv6 prefix and suffix
used by the DNS64. The communicated information enables hosts to
perform local IPv6 address synthesis.
Status of this Memo
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This Internet-Draft will expire on March 28, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements and Terminology . . . . . . . . . . . . . . . . . 3
2.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 3
3. EDNS0 option for indicating address synthesis . . . . . . . . . 3
4. Host behavior . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
As the networks transition to IPv6, connectivity to IPv4-only domains
have to be provided. NAT64 [I-D.ietf-behave-v6v4-xlate-stateful] and
DNS64 [I-D.ietf-behave-dns64] technologies can be utilized to make
IPv4-only peers look like being reachable over IPv6. The DNS64
utilizes IPv6 address synthesis to create local IPv6 presentations of
peers having only IPv4 addresses. Applications utilizing DNS for
resolving peers' IPv6 addresses can work seamlessly through protocol
translation taking place at NAT64.
The DNS64 cannot serve applications not using DNS, such as those
receiving IPv4 addresses as referrals. Such applications could
nevertheless be able to work through NAT64, provided they are able to
create locally valid IPv6 presentations of peers' IPv4 addresses.
This document describes a method for advanced applications to learn
the information required to perform local IPv6 address synthesis.
The knowledge of IPv6 address synthesizing taking place may also be
useful if DNS64 is present in dual-stack network access. In such
cases hosts may choose to use IPv4 addresses instead of synthesized
IPv6 addresses, and hence avoid traversal through NAT64.
2. Requirements and Terminology
2.1. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. EDNS0 option for indicating address synthesis
The mechanism for informing AAAA record synthesis taking place and
the used addressing format is communicated in an EDNS0 option in a
DNS response. The option has three bits indicating the formats
described in [I-D.ietf-behave-address-format]. The option and bits
are structured as follows:
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+0 (MSB) +1 (LSB)
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
0: | OPTION-CODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
2: | OPTION-LENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
4: | SY | Reserved |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
OPTION-CODE (Assigned by IANA)
OPTION-LENGTH 2 (Length of payload in octets)
Possible values for SY-bits are:
000 reserved
001 prefix length /32
010 prefix length /40
011 prefix length /48
100 prefix length /56
101 prefix length /64
110 prefix length /96
111 address is not synthesized
Reserved Initialized to zero
Figure 1
The prefix length corresponds to the address formats documented in
"IPv6 Addressing of IPv4/IPv6 Translators document"
[I-D.ietf-behave-address-format] section 2.2.
Absence of EDNS0 option means that either no synthesis took place or
the DNS64 does not support this specification. Either way, when the
EDNS0 option is missing, the host cannot conclude for certain whether
the AAAA response was synthesized or not. The host may additionally
utilize method described in
[I-D.savolainen-heuristic-nat64-discovery].
4. Host behavior
A host requiring information for local IPv6 address synthesis or
NAT64 avoidance shall send a DNS query for AAAA record of a well-
known IPv4-only fully qualified domain name. This well-known name
does not have to be in global DNS system. It is enough that DNS64
recognizes the name and replies to it.
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The host may query for well-known name, for example, at the moment
the host is configured an IPv6 address of a DNS server. This may
also happen at the time first DNS query for AAAA record is initiated.
If a host receives negative reply, it learns there are no NAT64 in
the network.
If a host receives AAAA reply, it knows the network is utilizing IPv6
address synthesis. If the received IPv6 address has well-known
prefix, the host can use that information for local IPv6 address
synthesis. If the prefix is not the well-known, the host reads the
flag values on the ENDS0 option to learn the used address format, and
with that information fetches from the received IPv6 address the
information used by the network for IPv6 address synthesis (prefix,
suffix, u-bit).
The information required for local IPv6 address synthesis should be
made available for applications to utilize.
5. Security Considerations
No security considerations have been identified.
6. IANA Considerations
IANA should define a name and an IPv4 address for a well-known IPv4-
only name.
IANA should allocate new OPTION-CODE for this option.
7. Acknowledgements
The authors would like to acknowledge Andrew Sullivan for presenting
general idea of ENDS0 option and SY-bit in behave WG mailing list.
8. References
8.1. Normative References
[I-D.ietf-behave-address-format]
Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators",
draft-ietf-behave-address-format-10 (work in progress),
August 2010.
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[I-D.ietf-behave-dns64]
Bagnulo, M., Sullivan, A., Matthews, P., and I. Beijnum,
"DNS64: DNS extensions for Network Address Translation
from IPv6 Clients to IPv4 Servers",
draft-ietf-behave-dns64-10 (work in progress), July 2010.
[I-D.ietf-behave-v6v4-xlate-stateful]
Bagnulo, M., Matthews, P., and I. Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers",
draft-ietf-behave-v6v4-xlate-stateful-12 (work in
progress), July 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
RFC 2671, August 1999.
8.2. Informative References
[I-D.savolainen-heuristic-nat64-discovery]
Savolainen, T. and J. Korhonen, "Heuristic discovery of
NAT64 and Network-Specific Prefix",
draft-savolainen-heuristic-nat64-discovery-00 (work in
progress), September 2010.
Authors' Addresses
Jouni Korhonen
Nokia Siemens Networks
Linnoitustie 6
FI-02600 Espoo
Finland
Email: jouni.nospam@gmail.com
Teemu Savolainen (editor)
Nokia
Hermiankatu 12 D
FI-33720 Tampere
Finland
Email: teemu.savolainen@nokia.com
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