Network Working Group F. Templin
Internet-Draft Nokia
Expires: April 14, 2004 T. Gleeson
Cisco Systems K.K.
M. Talwar
D. Thaler
Microsoft Corporation
October 15, 2003
Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
draft-ietf-ngtrans-isatap-16.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on April 14, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document specifies an Intra-Site Automatic Tunnel Addressing
Protocol (ISATAP) that connects IPv6 hosts and routers within IPv4
sites. ISATAP treats the site's IPv4 unicast infrastructure as a
Non-Broadcast, Multiple Access (NBMA) link layer for IPv6 with no
requirement for IPv4 multicast. ISATAP enables automatic IPv6-in-IPv4
tunneling whether globally assigned or private IPv4 addresses are
used.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Basic IPv6 Operation . . . . . . . . . . . . . . . . . . . . . 4
5. Automatic Tunneling . . . . . . . . . . . . . . . . . . . . . 6
6. Neighbor Discovery . . . . . . . . . . . . . . . . . . . . . . 8
7. Address Autoconfiguration . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Security considerations . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
Normative References . . . . . . . . . . . . . . . . . . . . . 13
Informative References . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 15
A. Major Changes . . . . . . . . . . . . . . . . . . . . . . . . 15
B. Interface Identifier Construction . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . . 18
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1. Introduction
This document specifies a simple mechanism called the Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP) that enables
incremental deployment of IPv6 [RFC2460] within IPv4 [RFC0791] sites.
ISATAP allows dual-stack nodes that do not share a link with an IPv6
router to automatically tunnel packets to the IPv6 next-hop address
through IPv4, i.e., the site's IPv4 infrastructure is treated as a
link layer for IPv6.
The main objectives of this document are to: 1) specify operational
details for automatic tunneling of IPv6 over IPv4 using ISATAP, 2)
specify the format of IPv6 interface identifiers using an embedded
IPv4 address, 3) specify the operation of Neighbor Discovery and
Address Autoconfiguration, and 4) discuss security considerations.
The specification in this document is very similar to [RFC2529], with
the primary distinction that ISATAP does not require IPv4 multicast
support within the site.
2. Requirements
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC2119].
This document also makes use of internal conceptual variables to
describe protocol behavior and external variables that an
implementation must allow system administrators to change. The
specific variable names, how their values change, and how their
settings influence protocol behavior are provided to demonstrate
protocol behavior. An implementation is not required to have them in
the exact form described here, so long as its external behavior is
consistent with that described in this document.
3. Terminology
The terminology of [RFC2460][RFC2461][RFC2462] applies to this
document. The following additional terms are defined:
site:
same as defined in [RFC3582], which is intended to be equivalent
to "enterprise" as defined in [RFC1918].
ISATAP interface:
an interface used for automatic IPv6-in-IPv4 tunneling and
configured over one or more IPv4 addresses assigned to one or more
of the node's IPv4 interfaces that belong to the same site.
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advertising ISATAP interface:
same meaning as advertising interface in ([RFC2461], section
6.2.2).
ISATAP address:
an address with an on-link prefix assigned on an ISATAP interface
and with an interface identifier constructed as specified in
Section 4.1.
4. Basic IPv6 Operation
ISATAP interfaces automatically tunnel IPv6 packets in IPv4 using the
site's IPv4 infrastructure as a link layer, i.e., IPv6 treats the
site's IPv4 infrastructure as a Non-Broadcast, Multiple Access (NBMA)
link layer with properties similar to [RFC2491]. The following
sections specify details for basic IPv6 operation on ISATAP
interfaces:
4.1 Interface Identifiers and Unicast Addresses
Interface identifiers for ISATAP are constructed in Modified EUI-64
format as specified in ([ADDR-ARCH], section 2.5.1). They are formed
by appending a 32-bit IPv4 address to the 32-bit leading token
'0000:5EFE', then setting the universal/local ("u") bit as follows:
When the IPv4 address is globally unique (i.e., provider-assigned),
the "u" bit is set to 1 and the leading token becomes '0200:5EFE'.
When the IPv4 address is from a private allocation [RFC1918], the "u"
bit is set to 0 and the leading token remains as '0000:5EFE'.
Global and link-local IPv6 unicast addresses ([ADDR-ARCH], sections
2.5.4, 2.5.6) for ISATAP are constructed as follows:
| 64 bits | 32 bits | 32 bits |
+------------------------------+---------------+----------------+
| global/link-local prefix | 000[0/2]:5EFE | IPv4 Address |
+------------------------------+---------------+----------------+
(Appendix B provides additional non-normative details.)
4.2 ISATAP Interface Management
The IP Tunnel MIB [MIB] is used, with the following additions for
ISATAP interfaces:
o For each IPv4 address an ISATAP interface is configured over, a
tuple consisting of the IPv4 address and ifIndex for the
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corresponding IPv4 interface ([RFC2863], section 3.1.5) is added
to ifRcvAddressTable ([MIB], section 3.1.2).
o tunnelIfRemoteInetAddress in the tunnelIfEntry object ([MIB],
section 4) is set to 0.0.0.0 for ISATAP interfaces.
When an IPv4 address over which an ISATAP interface is configured is
removed from its IPv4 interface, the corresponding (IPv4 addres,
ifIndex)-tuple MUST be removed from the ISATAP interface
ifRcvAddressTable. If the IPv4 address is also used as
tunnelIfLocalInetAddress ([MIB], section 5) in the ISATAP interface
tunnelIfEntry, the interface MUST either set tunnelIfLocalInetAddress
to a different IPv4 address or be disabled.
When a new IPv4 address is added to an IPv4 interface an ISATAP
interface is configured over, a new (IPv4 address, ifIndex)-tuple MAY
be added to ifRcvAddressTable and tunnelIfLocalInetAddress MAY be set
to the new address.
4.3 Multicast and Anycast
ISATAP interfaces recognize an IPv6 node's required addresses
([ADDR-ARCH], section 2.8). The following multicast mappings are
defined for packets sent on ISATAP interfaces:
o When the IPv6 destination address is the 'All-Routers'
([ADDR-ARCH], section 2.7.1) or
'All_DHCP_Relay_Agents_and_Servers' ([RFC3315], section 1.2)
multicast address, it is mapped to V4ADDR(i) for one or more
PRL(i)'s (see: Section 6.1). The manner of selecting PRL(i)'s is
up to the implementation.
Other multicast mappings, and mechanisms for general-purpose
multicast/anycast emulation on ISATAP interfaces are beyond the scope
of this document.
4.4 Source/Target Link Layer Address Options
Source/Target Link Layer Address Options ([RFC2461], section 4.6.1)
for ISATAP have the following format:
+-------+-------+-------+-------+-------+-------+-------+--------+
| Type |Length | 0 | 0 | IPv4 Address |
+-------+-------+-------+-------+-------+-------+-------+--------+
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Type:
1 for Source Link-layer address.
2 for Target Link-layer address.
Length:
1 (in units of 8 octets).
IPv4 Address:
The 32 bit IPv4 address, in network byte order.
5. Automatic Tunneling
ISATAP interfaces use the basic transition mechanisms specified in
[MECH] with the following exceptions:
5.1 Tunnel MTU and Fragmentation
The specification in ([MECH], section 3.2) is not used; the
specification in this section is used instead.
The minimum MTU for IPv6 interfaces is 1280 bytes ([RFC2460], Section
5), but the following operational considerations are noted:
o Nearly all IPv4 nodes connect to physical links with MTUs of 1500
bytes or larger (e.g., Ethernet)
o Sub-IPv4 layer encapsulations (e.g., VPN) may occur on some paths
o Commonly-deployed VPN interfaces use an MTU of 1400 bytes
To maximize efficiency and minimize IPv4 fragmentation for the
predominant deployment case, LinkMTU for ISATAP interfaces SHOULD be
set to no more than 1380 bytes (1400 minus 20 bytes for IPv4
encapsulation).
LinkMTU MAY be set to larger values when a dynamic link layer (IPv4)
MTU discovery mechanism is used, or when a static MTU assignment is
used and the anticipated/measured level of fragmentation in the
site's IPv4 network is deemed acceptable.
When a dynamic link layer MTU discovery mechanism is not used, the
Don't Fragment (DF) bit MUST NOT be set in the encapsulating IPv4
header of packets sent on the ISATAP interface. In this case, black
holes may in rare instances occur along some paths even when the
tunnel interface uses the IPv6 minimum MTU of 1280 bytes. (This
concern is not specific to ISATAP interfaces, but applies to all
tunnels for which nested levels of sub link-layer encapsulation may
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occur.)
5.2 Handling IPv4 ICMP Errors
ARP failures and persistent ICMPv4 errors SHOULD be processed as
link-specific information indicating that a path to a neighbor has
failed ([RFC2461], section 7.3.3).
5.3 Link-Local Addresses
The specification in ([MECH], section 3.7) is not used; the
specification in Section 4.1 of this document is used instead.
5.4 Neighbor Discovery over Tunnels
The specification in ([MECH], section 3.8) is not used; the
specifications in Section 6 and Section 7 of this document are used
instead.
5.5 Decapsulation/Filtering
The specifications in ([MECH], sections 3.6, 3.9 and 4.1) are used.
In addition, the decapsulator MUST determine the correct tunnel
interface to receive each IPv4 protocol-41 packet via a table lookup
for the tuple consisting of the packet's IPv4 source and destination
address, and ifIndex for the receiving IPv4 interface. (Note that
ISATAP interfaces match all IPv4 source addresses by default; if a
tunnel interface with a more-specific match on the IPv4 source
address exists, it is selected to receive the packet as for
longest-prefix-match.) Packets for which the correct tunnel interface
cannot be determined are discarded; in this case, the decapsulator
MAY also send an ICMPv4 Destination Unreachable message with code 3
(Port Unreachable) ([RFC1122], section 3.2.2.1) to the IPv4 source
address in the packet's outer header.
After determining the correct tunnel interface, the decapsulator MUST
also verify that the packet's link-layer (IPv4) source address is
correct for the network-layer (IPv6) source address. For ISATAP
interfaces, the packet's link-layer source address is correct if one
(or more) of the following are true:
o the network-layer source address is an ISATAP address that embeds
the link-layer source address in its interface identifier.
o the network-layer source address is an IPv6 neighbor within the
same site as the receiving ISATAP interface, and the link-layer
source address matches the link layer address in the neighbor
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cache.
o the link-layer source address is a member of the Potential Router
List for the site (see: Section 6.1).
Packets for which the link-layer source address is incorrect are
discarded, and an ICMPv6 Destination Unreachable message ([ICMPV6],
section 3.1) SHOULD be sent to the IPv6 source in the inner header of
the encapsulated packet (subject to rate limiting as in [ICMPV6],
section 2.4, paragraph f).
6. Neighbor Discovery
ISATAP interfaces use the neighbor discovery mechanisms specified in
[RFC2461] with the following exceptions:
6.1 Conceptual Model Of A Host
To the list of Conceptual Data Structures ([RFC2461], section 5.1),
ISATAP interfaces add:
Potential Router List
A set of entries about potential routers for the site; used to
support the mechanisms specified in Section 6.2.3. Each entry
("PRL(i)") has an associated timer ("TIMER(i)"), and an IPv4
address ("V4ADDR(i)") that represents a router's advertising
ISATAP interface.
6.2 Router and Prefix Discovery
6.2.1 Message Validation
6.2.1.1 Validation of Router Solicitation Messages
To the list of validity checks for Router Soliciation messages
([RFC2461], section 6.1.1), ISATAP interfaces add:
o If the message includes a Source Link Layer Address Option, the
message also includes an IP authentication Header.
6.2.1.2 Validation of Router Advertisement Messages
To the list of validity checks for Router Advertisement messages
([RFC2461], section 6.1.1), ISATAP interfaces add:
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o IP Source Address is an ISATAP link-local address that embeds
V4ADDR(i) for some PRL(i).
o If the message includes a Source Link Layer Address Option, the
message also includes an IP authentication Header.
6.2.2 Router Specification
As permitted by ([RFC2461], section 6.2.6), advertising ISATAP
interfaces SHOULD unicast Router Advertisement messages to the
soliciting host's address when the solicitation's source address is
not the unspecified address.
6.2.3 Host Specification
6.2.3.1 Host Variables
To the list of host variables ([RFC2461], section 6.3.2), ISATAP
interfaces add:
PrlRefreshInterval
Time in seconds between successive refreshments of the PRL after
initialization. It SHOULD be no less than 3600 seconds. The
designated value of all 1's (0xffffffff) represents infinity.
Default: 3600 seconds
MinRouterSolicitInterval
Minimum time in seconds between successive solicitations of the
same advertising ISATAP interface. It SHOULD be no less than 900
seconds. The designated value of alll 1's (0xffffffff) represents
infinity.
Default: 900 seconds
6.2.3.2 Interface Initialization
The host joins the all-nodes multicast address on ISATAP interfaces,
as for multicast-capable interfaces ([RFC2461], section 6.3.3).
Additionally, the host provisions the ISATAP interface's PRL with
IPv4 addresses it discovers via manual configuration, a DNS
fully-qualified domain name (FQDN) [RFC1035], a DHCPv4 option for
ISATAP [ISDHCP], a DHCPv4 vendor-specific option, or an unspecified
alternate method. (Support for manual configuration is REQUIRED;
other methods are OPTIONAL.)
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When FQDNs are used, the host establishes the FQDN via manual
configuration or an unspecified alternate method. (Support for manual
configuration is REQUIRED; other methods are OPTIONAL.) The host
resolves the FQDN into IPv4 addresses through lookup in a static host
file, a site-specific name service, querying the site's DNS service,
or an unspecified alternate method. When DNS is used, client
resolvers use the IPv4 transport.
After the host provisions the ISATAP interface's PRL with IPv4
addresses, it sets PrlRefreshIntervalTimer to PrlRefreshInterval
seconds. The host re-initializes the PRL (i.e., as specified above)
when PrlRefreshIntervalTimer expires, or when an asynchronous
re-initialization event occurs. When the host re-initializes the PRL,
it resets PrlRefreshIntervalTimer to PrlRefreshInterval seconds.
6.2.3.3 Processing Received Router Advertisements
Router Advertisements (RAs) are processed exactly as specified in
([RFC2461], section 6.3.4) except that, if the MTU option is present,
the option's value SHOULD be stored in a per-neighbor cache entry for
the source of the RA; it MUST NOT be copied into LinkMTU for the
ISATAP interface.
Additionally, hosts reset TIMER(i) to schedule the next solicitation
event (see: Section 6.2.3.4). Let "MIN_LIFETIME" be the minimum value
in the Router Lifetime or the lifetime(s) encoded in options included
in the RA message. Then, TIMER(i) is reset as follows:
TIMER(i) = MAX((0.5 * MIN_LIFETIME), MinRouterSolicitInterval)
6.2.3.4 Sending Router Solicitations
To the list of events after which RSs may be sent ([RFC2461], section
6.3.2), ISATAP interfaces add:
o TIMER(i) for some PRL(i) expires.
Additionally, hosts MAY send Router Solicitations to an ISATAP
link-local address that embeds V4ADDR(i) for some PRL(i) instead of
the All-Routers multicast address.
6.3 Address Resolution and Neighbor Unreachability Detection
6.3.1 Message Validation
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6.3.1.1 Validation of Neighbor Solicitations
To the list of validity checks for Neighbor Solicitation (NS)
messages ([RFC2461], section 7.1.1), ISATAP interfaces add:
o If the message includes a Source Link Layer Address Option, the
message also includes an IP authentication Header.
6.3.1.2 Validation of Neighbor Solicitations
To the list of validity checks for Neighbor Advertisement (NA)
messages ([RFC2461], section 7.1.2), ISATAP interfaces add:
o If the message includes a Target Link Layer Address Option, the
message also includes an IP authentication Header.
6.3.2 Address Resolution
The specification in ([RFC2461], section 7.2) is used. NS and NA
messages MAY omit the source/target link layer address option when
the source/target is an ISATAP address. ISATAP addresses for which
the neighbor's link-layer address cannot otherwise be determined
(i.e., from the neighbor cache or a link layer address option in a
received packet) are resolved to link-layer addresses by a static
computation, i.e., the last four octets are treated as an IPv4
address.
Hosts SHOULD perform an initial reachability confirmation by sending
NS message(s) and receiving a NA message; NS messages are sent to the
target's unicast address. Routers MAY perform an initial reachability
confirmation, but this might not scale in all environments.
As specified in ([RFC2461], section 7.2.4), all nodes MUST send
solicited neighbor advertisements on ISATAP interfaces.
6.3.3 Neighbor Unreachability Detection
Hosts SHOULD perform Neighbor Unreachability Detection as specified
in ([RFC2461], section 7.3). Routers MAY perform neighbor
unreachability detection, but this might not scale in all
environments.
6.4 Redirect Function
To the list of validity checks for Redirect messages (([RFC2461],
section 8.1), ISATAP interfaces add:
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o If the message includes a Target Link Layer Address Option, the
message also includes an IP authentication Header.
7. Address Autoconfiguration
ISATAP interfaces use the address autoconfiguration mechanisms
specified in [RFC2462] with the following exceptions:
7.1 Address Lifetime Expiry
The specification in ([RFC2462], section 5.5.4) is used, except that
an ISATAP address also becomes deprecated when the IPv4 address
embedded in its interface identifier is removed from an IPv4
interface over which the ISATAP interface is configured. (This
deprecation rule applies to all ISATAP addresses, including
link-local addresses.)
7.2 Stateful Address Autoconfiguration
When the site uses DHCPv6 [RFC3315] as the stateful address
autoconfiguration mechanism, the server/relay function MUST be
deployed equally on each router that is a member of the PRL.
8. IANA Considerations
The IANA is advised to specify construction rules for IEEE EUI-64
addresses formed from the Organizationally Unique Identifier (OUI)
"00-00-5E" in the IANA "ethernet-numbers" registry. The non-normative
text in Appendix B is offered as an example specification.
9. Security considerations
The security considerations in [RFC2461][RFC2462][MECH] apply.
Additionally, site administrators MUST ensure that lists of IPv4
addresses representing the advertising ISATAP interfaces of PRL
members are well maintained.
10. Acknowledgments
Most of the basic ideas in this document are not original; the
authors acknowledge the original architects of those ideas. Portions
of this work were sponsored through SRI International internal
projects and government contracts. Government sponsors include Monica
Farah-Stapleton and Russell Langan (U.S. Army CECOM ASEO), and Dr.
Allen Moshfegh (U.S. Office of Naval Research). SRI International
sponsors include Dr. Mike Frankel, J. Peter Marcotullio, Lou
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Rodriguez, and Dr. Ambatipudi Sastry.
The following are acknowledged for providing peer review input: Jim
Bound, Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader,
Ole Troan, Vlad Yasevich.
The following are acknowledged for their significant contributions:
Alain Durand, Hannu Flinck, Jason Goldschmidt, Nathan Lutchansky,
Karen Nielsen, Mohan Parthasarathy, Chirayu Patel, Art Shelest, Pekka
Savola, Margaret Wasserman, Brian Zill.
The authors acknowledge the work of Quang Nguyen [VET] under the
guidance of Dr. Lixia Zhang that proposed very similar ideas to those
that appear in this document. This work was first brought to the
authors' attention on September 20, 2002.
Normative References
[ADDR-ARCH]
Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", draft-ietf-ipv6-addr-arch-v4-00 (work in
progress), October 2003.
[ICMPV6] Conta, A. and S. Deering, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", draft-ietf-ipngwg-icmp-v3 (work in
progress), November 2001.
[MECH] Gilligan, R. and E. Nordmark, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", draft-ietf-v6ops-mech-v2-00
(work in progress), February 2003.
[MIB] Thaler, D., "IP Tunnel MIB", draft-thaler-inet-tunnel-mib
(work in progress), September 2003.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998.
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[RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
Informative References
[ISDHCP] Templin, F., "Dynamic Host Configuration Protocol (DHCPv4)
Option for the Intra-Site Automatic Tunnel Addressing
Protocol (ISATAP)", draft-templin-isatap-dhcp (work in
progress), October 2003.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and
E. Lear, "Address Allocation for Private Internets", BCP
5, RFC 1918, February 1996.
[RFC2491] Armitage, G., Schulter, P., Jork, M. and G. Harter, "IPv6
over Non-Broadcast Multiple Access (NBMA) networks", RFC
2491, January 1999.
[RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529, March 1999.
[RFC2827] 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.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, June 2000.
[RFC3041] Narten, T. and R. Draves, "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC 3041,
January 2001.
[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.
[RFC3582] Abley, J., Black, B. and V. Gill, "Goals for IPv6
Site-Multihoming Architectures", RFC 3582, August 2003.
[VET] Nguyen, Q., "http://irl.cs.ucla.edu/vet/report.ps", spring
1998.
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Authors' Addresses
Fred L. Templin
Nokia
313 Fairchild Drive
Mountain View, CA 94110
US
Phone: +1 650 625 2331
EMail: ftemplin@iprg.nokia.com
Tim Gleeson
Cisco Systems K.K.
Shinjuku Mitsu Building
2-1-1 Nishishinjuku, Shinjuku-ku
Tokyo 163-0409
Japan
EMail: tgleeson@cisco.com
Mohit Talwar
Microsoft Corporation
One Microsoft Way
Redmond, WA> 98052-6399
US
Phone: +1 425 705 3131
EMail: mohitt@microsoft.com
Dave Thaler
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
US
Phone: +1 425 703 8835
EMail: dthaler@microsoft.com
Appendix A. Major Changes
Major changes from earlier versions to version 16:
o dropped "underlying link" from terminology.
o specified multicast mappings.
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o specified layer address option format.
o specified setting of "u" bit in interface id's.
o removed obsoleted appendix sections.
o re-organized major sections to match normative references.
o revised neighbor discovery, address autoconfiguration, security
considerations sections. Added new subsections on interface
management, decapsulation/filtering, address lifetime expiry.
Appendix B. Interface Identifier Construction
This section provides an example specification for constructing EUI64
addresses from the Organizationally-Unique Identifier (OUI) owned by
the Internet Assigned Numbers Authority (IANA). It can be used to
construct both modified EUI-64 format interface identifiers for IPv6
unicast addresses ([ADDR-ARCH], section 2.5.1) and "native" EUI64
addresses for future use:
|0 2|2 3|3 3|4 6|
|0 3|4 1|2 9|0 3|
+------------------------+--------+--------+------------------------+
| OUI ("00-00-5E"+u+g) | TYPE | TSE | TSD |
+------------------------+--------+--------+------------------------+
Where the fields are:
OUI IANA's OUI: 00-00-5E with "u" and "g" bits (3 octets)
TYPE Type field; specifies use of (TSE, TSD) (1 octet)
TSE Type-Specific Extension (1 octet)
TSD Type-Specific Data (3 octets)
And the following interpretations are specified based on TYPE:
TYPE (TSE, TSD) Interpretation
---- -------------------------
0x00-0xFD RESERVED for future IANA use
0xFE (TSE, TSD) together contain an IPv4 address
0xFF TSD is interpreted based on TSE as follows:
TSE TSD Interpretation
--- ------------------
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0x00-0xFD RESERVED for future IANA use
0xFE TSD contains 24-bit EUI-48 intf id
0xFF RESERVED by IEEE/RAC
Using this example specification, if TYPE=0xFE, then TSE is an
extension of TSD. If TYPE=0xFF, then TSE is an extension of TYPE.
(Other values for TYPE, and other interpretations of TSE, TSD are
reserved for future IANA use.) When TYPE='0xFE' the EUI64 address
embeds an IPv4 address, encoded in network byte order.
For Modified EUI64 format interface identifiers in IPv6 unicast
addresses ([ADDR-ARCH], Appendix A) using IANA's OUI, when TYPE=0xFE
and the IPv4 address is a globally unique (i.e., provider-assigned)
unicast address, the "u" bit is set to 1 to indicate universal scope.
When TYPE=0xFE and the IPv4 address is from a private allocation, the
"u" bit is set to 0 to indicate local scope. Thus, when the first
four octets of the interface identifier in an IPv6 unicast address
are either: '02-00-5E-FE' or: '00-00-5E-FE', the next four octets
embed an IPv4 address and the interface identifier is said to be in
"ISATAP format".
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