draft-ietf-ngtrans-isatap-15.txt   draft-ietf-ngtrans-isatap-16.txt 
Network Working Group F. Templin Network Working Group F. Templin
Internet-Draft Nokia Internet-Draft Nokia
Expires: March 10, 2004 T. Gleeson Expires: April 14, 2004 T. Gleeson
Cisco Systems K.K. Cisco Systems K.K.
M. Talwar M. Talwar
D. Thaler D. Thaler
Microsoft Corporation Microsoft Corporation
September 10, 2003 October 15, 2003
Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
draft-ietf-ngtrans-isatap-15.txt draft-ietf-ngtrans-isatap-16.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on March 10, 2004. This Internet-Draft will expire on April 14, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This document specifies an Intra-Site Automatic Tunnel Addressing This document specifies an Intra-Site Automatic Tunnel Addressing
Protocol (ISATAP) that connects IPv6 hosts and routers within IPv4 Protocol (ISATAP) that connects IPv6 hosts and routers within IPv4
sites. ISATAP treats the site's IPv4 unicast infrastructure as a link sites. ISATAP treats the site's IPv4 unicast infrastructure as a
layer for IPv6. ISATAP enables intra-site automatic IPv6-in-IPv4 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 tunneling whether globally assigned or private IPv4 addresses are
used. used.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Basic IPv6 Operation . . . . . . . . . . . . . . . . . . . . . 4 4. Basic IPv6 Operation . . . . . . . . . . . . . . . . . . . . . 4
5. Automatic Tunneling . . . . . . . . . . . . . . . . . . . . . 5 5. Automatic Tunneling . . . . . . . . . . . . . . . . . . . . . 6
6. Neighbor Discovery . . . . . . . . . . . . . . . . . . . . . . 6 6. Neighbor Discovery . . . . . . . . . . . . . . . . . . . . . . 8
7. Address Autoconfiguration . . . . . . . . . . . . . . . . . . 9 7. Address Autoconfiguration . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Security considerations . . . . . . . . . . . . . . . . . . . 9 9. Security considerations . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
Normative References . . . . . . . . . . . . . . . . . . . . . 10 Normative References . . . . . . . . . . . . . . . . . . . . . 13
Informative References . . . . . . . . . . . . . . . . . . . . 11 Informative References . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 15
A. Major Changes . . . . . . . . . . . . . . . . . . . . . . . . 12 A. Major Changes . . . . . . . . . . . . . . . . . . . . . . . . 15
B. Rationale for Interface Identifier Construction . . . . . . . 14 B. Interface Identifier Construction . . . . . . . . . . . . . . 16
C. Deployment Considerations . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . . 18
D. Other Considerations . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . 17
1. Introduction 1. Introduction
This document presents a simple approach called the Intra-Site This document specifies a simple mechanism called the Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP) that enables Automatic Tunnel Addressing Protocol (ISATAP) that enables
incremental deployment of IPv6 [RFC2460] within IPv4 [RFC0791] sites. incremental deployment of IPv6 [RFC2460] within IPv4 [RFC0791] sites.
ISATAP allows dual-stack nodes that do not share a link with an IPv6 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 router to automatically tunnel packets to the IPv6 next-hop address
through IPv4, i.e., the site's IPv4 infrastructure is treated as a through IPv4, i.e., the site's IPv4 infrastructure is treated as a
link layer for IPv6. link layer for IPv6.
Specific details for the operation of IPv6 and automatic tunneling The main objectives of this document are to: 1) specify operational
using ISATAP are given, including an interface identifier format that details for automatic tunneling of IPv6 over IPv4 using ISATAP, 2)
embeds an IPv4 address. This format supports IPv6 address specify the format of IPv6 interface identifiers using an embedded
configuration and simple link-layer address mapping. Also specified IPv4 address, 3) specify the operation of Neighbor Discovery and
is the operation of IPv6 Neighbor Discovery and deployment/security Address Autoconfiguration, and 4) discuss security considerations.
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 2. Requirements
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC2119]. document, are to be interpreted as described in [RFC2119].
This document also makes use of internal conceptual variables to This document also makes use of internal conceptual variables to
describe protocol behavior and external variables that an describe protocol behavior and external variables that an
implementation must allow system administrators to change. The implementation must allow system administrators to change. The
specific variable names, how their values change, and how their specific variable names, how their values change, and how their
settings influence protocol behavior are provided to demonstrate settings influence protocol behavior are provided to demonstrate
protocol behavior. An implementation is not required to have them in protocol behavior. An implementation is not required to have them in
the exact form described here, so long as its external behavior is the exact form described here, so long as its external behavior is
consistent with that described in this document. consistent with that described in this document.
3. Terminology 3. Terminology
The terminology of [RFC2460] applies to this document. The following The terminology of [RFC2460][RFC2461][RFC2462] applies to this
additional terms are defined: document. The following additional terms are defined:
site: site:
same as defined in [RFC3582], which is intended to be equivalent same as defined in [RFC3582], which is intended to be equivalent
to "enterprise" as defined in [RFC1918]. to "enterprise" as defined in [RFC1918].
link, on-link, off-link:
same as defined in ([RFC2461], section 2.1).
underlying link:
a link layer that supports IPv4 (for ISATAP), and MAY also support
IPv6 natively.
ISATAP interface: ISATAP interface:
an interface configured over one or more underlying links. 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.
advertising ISATAP interface: advertising ISATAP interface:
same meaning as "advertising interface" in ([RFC2461], section same meaning as advertising interface in ([RFC2461], section
6.2.2). 6.2.2).
ISATAP address: ISATAP address:
an address with an on-link prefix assigned on an ISATAP interface an address with an on-link prefix assigned on an ISATAP interface
and with an interface identifier constructed as specified in and with an interface identifier constructed as specified in
Section 4.1. Section 4.1.
4. Basic IPv6 Operation 4. Basic IPv6 Operation
ISATAP interfaces automatically tunnel IPv6 packets using the site's ISATAP interfaces automatically tunnel IPv6 packets in IPv4 using the
IPv4 infrastructure as a link layer for IPv6, i.e., IPv6 treats 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) site's IPv4 infrastructure as a Non-Broadcast, Multiple Access (NBMA)
link layer, with properties similar to [RFC2491]. The following link layer with properties similar to [RFC2491]. The following
ISATAP-specific considerations are noted for basic IPv6 operation: sections specify details for basic IPv6 operation on ISATAP
interfaces:
4.1 Interface Identifiers and Unicast Addresses 4.1 Interface Identifiers and Unicast Addresses
ISATAP interface identifiers use "modified EUI-64" format ([RFC3513], Interface identifiers for ISATAP are constructed in Modified EUI-64
section 2.5.1) and are formed by appending an IPv4 address assigned format as specified in ([ADDR-ARCH], section 2.5.1). They are formed
to an underlying link to the 32-bit string '00-00-5E-FE'. Appendix B by appending a 32-bit IPv4 address to the 32-bit leading token
includes non-normative rationale for this construction rule. '0000:5EFE', then setting the universal/local ("u") bit as follows:
IPv6 global and local-use ([RFC3513], sections 2.5.4, 2.5.6) ISATAP When the IPv4 address is globally unique (i.e., provider-assigned),
addresses are constructed as follows: 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 | | 64 bits | 32 bits | 32 bits |
+------------------------------+---------------+----------------+ +------------------------------+---------------+----------------+
| global/local unicast prefix | 0000:5EFE | IPv4 Address | | global/link-local prefix | 000[0/2]:5EFE | IPv4 Address |
+------------------------------+---------------+----------------+ +------------------------------+---------------+----------------+
4.2 ISATAP Interface Configuration (Appendix B provides additional non-normative details.)
ISATAP interfaces are configured over one or more underlying links 4.2 ISATAP Interface Management
that support IPv4 for tunneling within a site; each IPv4 address
assigned to an underlying link is seen as a link-layer address for The IP Tunnel MIB [MIB] is used, with the following additions for
ISATAP. ISATAP interfaces:
o For each IPv4 address an ISATAP interface is configured over, a
tuple consisting of the IPv4 address and ifIndex for the
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 4.3 Multicast and Anycast
ISATAP interfaces recognize an IPv6 node's required addresses ISATAP interfaces recognize an IPv6 node's required addresses
([RFC3513], section 2.8), including certain multicast/anycast ([ADDR-ARCH], section 2.8). The following multicast mappings are
addresses. defined for packets sent on ISATAP interfaces:
Mechanisms for multicast/anycast emulation on ISATAP interfaces o When the IPv6 destination address is the 'All-Routers'
(e.g., MARS [RFC2022], etc.) are out of scope. ([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 |
+-------+-------+-------+-------+-------+-------+-------+--------+
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 5. Automatic Tunneling
The common tunneling mechanisms specified in ([MECH], sections 2 and ISATAP interfaces use the basic transition mechanisms specified in
3) are used, with the following noted considerations for ISATAP: [MECH] with the following exceptions:
5.1 Tunnel MTU and Fragmentation 5.1 Tunnel MTU and Fragmentation
ISATAP automatic tunnel interfaces may be configured over multiple The specification in ([MECH], section 3.2) is not used; the
underlying links with diverse maximum transmission units (MTUs). The specification in this section is used instead.
minimum MTU for IPv6 interfaces is 1280 bytes ([RFC2460], Section 5),
but the following considerations apply for ISATAP interfaces: 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 o Nearly all IPv4 nodes connect to physical links with MTUs of 1500
bytes or larger (e.g., Ethernet) bytes or larger (e.g., Ethernet)
o Sub-IPv4 layer encapsulations (e.g., VPN) may occur on some paths o Sub-IPv4 layer encapsulations (e.g., VPN) may occur on some paths
o Commonly-deployed VPN interfaces use an MTU of 1400 bytes o Commonly-deployed VPN interfaces use an MTU of 1400 bytes
To maximize efficiency and minimize IPv4 fragmentation for the To maximize efficiency and minimize IPv4 fragmentation for the
predominant deployment case, LinkMTU ([RFC2461], Section 6.3.2) for predominant deployment case, LinkMTU for ISATAP interfaces SHOULD be
the ISATAP interface SHOULD be set to no more than 1380 bytes (1400 set to no more than 1380 bytes (1400 minus 20 bytes for IPv4
minus 20 bytes for IPv4 encapsulation). encapsulation).
LinkMTU MAY be set to larger values when a dynamic link layer MTU LinkMTU MAY be set to larger values when a dynamic link layer (IPv4)
discovery mechanism is used or when a static MTU assignment is used MTU discovery mechanism is used, or when a static MTU assignment is
and the anticipated/measured level of fragmentation in the site's used and the anticipated/measured level of fragmentation in the
IPv4 network is deemed acceptable. site's IPv4 network is deemed acceptable.
When a dynamic link layer MTU discovery mechanism is not used, the When a dynamic link layer MTU discovery mechanism is not used, the
ISATAP interface MUST NOT encapsulate IPv6 packets with the Don't Don't Fragment (DF) bit MUST NOT be set in the encapsulating IPv4
Fragment (DF) bit set in the encapsulating IPv4 header. 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
occur.)
5.2 Handling IPv4 ICMP Errors 5.2 Handling IPv4 ICMP Errors
ARP failures and persistent ICMPv4 errors SHOULD be processed as ARP failures and persistent ICMPv4 errors SHOULD be processed as
link-specific information indicating that a path to a neighbor has link-specific information indicating that a path to a neighbor has
failed ([RFC2461], section 7.3.3). failed ([RFC2461], section 7.3.3).
5.3 Local-Use IPv6 Unicast Addresses 5.3 Link-Local Addresses
The specification in ([MECH], section 3.7) is not used; the The specification in ([MECH], section 3.7) is not used; the
specification in Section 4.1 is used instead. specification in Section 4.1 of this document is used instead.
5.4 Ingress Filtering 5.4 Neighbor Discovery over Tunnels
The specification in ([MECH], section 3.9) is used. The specification in ([MECH], section 3.8) is not used; the
specifications in Section 6 and Section 7 of this document are used
instead.
Additionally, packets received on an ISATAP interface with an ISATAP 5.5 Decapsulation/Filtering
network-layer (IPv6) source address that does not embed the
link-layer (IPv4) source address in the interface identifier are The specifications in ([MECH], sections 3.6, 3.9 and 4.1) are used.
silently discarded.
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
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 6. Neighbor Discovery
The specification in ([MECH], section 3.8) applies only to configured ISATAP interfaces use the neighbor discovery mechanisms specified in
tunnels. [RFC2461] provides the following guidelines for [RFC2461] with the following exceptions:
non-broadcast multiple access (NBMA) link support:
"Redirect, Neighbor Unreachability Detection and next-hop 6.1 Conceptual Model Of A Host
determination should be implemented as described in this document.
Address resolution and the mechanism for delivering Router
Solicitations and Advertisements on NBMA links is not specified in
this document."
ISATAP interfaces SHOULD implement Redirect, Neighbor Unreachability To the list of Conceptual Data Structures ([RFC2461], section 5.1),
Detection, and next-hop determination exactly as specified in ISATAP interfaces add:
[RFC2461]. Address resolution and the mechanisms for delivering
Router Solicitations and Advertisements are not specified by
[RFC2461]; instead, they are specified in the following sections of
this document.
6.1 Address Resolution and Neighbor Unreachability Detection 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.
ISATAP addresses are resolved to link-layer (IPv4) addresses by a 6.2 Router and Prefix Discovery
static computation, i.e., the last four octets are treated as an IPv4
address.
Hosts SHOULD perform an initial reachability confirmation by sending 6.2.1 Message Validation
Neighbor Solicitation (NS) message(s) and receiving a Neighbor
Advertisement (NA) message as specified in ([RFC2461], section 7.2).
Unless otherwise specified in a future document, solicitations are
sent to the target's unicast address.
Hosts SHOULD additionally perform Neighbor Unreachability Detection 6.2.1.1 Validation of Router Solicitation Messages
(NUD) as specified in ([RFC2461], section 7.3). Routers MAY perform
these reachability confirmation and NUD procedures, but this might
not scale in all environments.
All ISATAP nodes MUST send solicited neighbor advertisements To the list of validity checks for Router Soliciation messages
([RFC2461], section 7.2.4). ([RFC2461], section 6.1.1), ISATAP interfaces add:
6.2 Duplicate Address Detection o If the message includes a Source Link Layer Address Option, the
message also includes an IP authentication Header.
Duplicate Address Detection ([RFC2462], section 5.4) is not required 6.2.1.2 Validation of Router Advertisement Messages
for ISATAP addresses, since duplicate address detection is assumed to
have been already performed for the IPv4 addresses from which they
derive.
6.3 Router and Prefix Discovery To the list of validity checks for Router Advertisement messages
([RFC2461], section 6.1.1), ISATAP interfaces add:
The following sections describe mechanisms to support the router and o IP Source Address is an ISATAP link-local address that embeds
prefix discovery process ([RFC2461], section 6): V4ADDR(i) for some PRL(i).
6.3.1 Conceptual Data Structures o If the message includes a Source Link Layer Address Option, the
message also includes an IP authentication Header.
ISATAP nodes use the conceptual data structures Prefix List and 6.2.2 Router Specification
Default Router List exactly as in ([RFC2461], section 5.1). ISATAP
adds a new conceptual data structure "Potential Router List" (PRL) As permitted by ([RFC2461], section 6.2.6), advertising ISATAP
and the following new configuration variable: 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 PrlRefreshInterval
Time in seconds between successive refreshments of the PRL after Time in seconds between successive refreshments of the PRL after
initialization. It SHOULD be no less than 3,600 seconds. The initialization. It SHOULD be no less than 3600 seconds. The
designated value of all 1's (0xffffffff) represents infinity. designated value of all 1's (0xffffffff) represents infinity.
Default: 3,600 seconds Default: 3600 seconds
A PRL is associated with every ISATAP interface and supports the MinRouterSolicitInterval
mechanisms specified in Section 6.3.4. Each entry in the PRL Minimum time in seconds between successive solicitations of the
("PRL(i)") has an associated timer ("TIMER(i)"), and an IPv4 address same advertising ISATAP interface. It SHOULD be no less than 900
("V4ADDR(i)") that represents a site border router's advertising 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.)
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. ISATAP interface.
When a node enables an ISATAP interface, it initializes the PRL with Additionally, hosts reset TIMER(i) to schedule the next solicitation
IPv4 addresses. The addresses MAY be discovered via a DHCPv4 event (see: Section 6.2.3.4). Let "MIN_LIFETIME" be the minimum value
[RFC2131] option for ISATAP, manual configuration, or an unspecified in the Router Lifetime or the lifetime(s) encoded in options included
alternate method (e.g., DHCPv4 vendor-specific option, etc.). in the RA message. Then, TIMER(i) is reset as follows:
When no other mechanisms are available, a DNS fully-qualified domain TIMER(i) = MAX((0.5 * MIN_LIFETIME), MinRouterSolicitInterval)
name (FQDN) [RFC1035] established by an out-of-band method (e.g.,
DHCPv4, manual configuration, etc.) MAY be used. The FQDN is resolved
into IPv4 addresses for the PRL through a static host file, a
site-specific name service, querying a DNS server within the site, or
an unspecified alternate method. There are no mandatory rules for the
selection of a FQDN, but manual configuration MUST be supported. When
DNS is used, client resolvers use the IPv4 transport.
After initialization, nodes periodically refresh the PRL (i.e., using 6.2.3.4 Sending Router Solicitations
one or more of the methods described above) after PrlRefreshInterval.
6.3.2 Validation of Router Advertisements Messages To the list of events after which RSs may be sent ([RFC2461], section
6.3.2), ISATAP interfaces add:
The specification in ([RFC2461], section 6.1.2) is used. o TIMER(i) for some PRL(i) expires.
6.3.3 Router Specification 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.
Routers with advertising ISATAP interfaces behave the same as 6.3 Address Resolution and Neighbor Unreachability Detection
described in ([RFC2461], section 6.2). As permitted by ([RFC2461],
section 6.2.6), advertising ISATAP interfaces SHOULD send unicast RA
messages to a soliciting host's unicast address when the
solicitation's source address is not the unspecified address.
6.3.4 Host Specification 6.3.1 Message Validation
Hosts behave the same as described in ([RFC2461], section 6.3) with 6.3.1.1 Validation of Neighbor Solicitations
the following additional considerations for ISATAP:
6.3.4.1 Soliciting Router Advertisements To the list of validity checks for Neighbor Solicitation (NS)
messages ([RFC2461], section 7.1.1), ISATAP interfaces add:
Hosts solicit Router Advertisements (RAs) by sending Router o If the message includes a Source Link Layer Address Option, the
Solicitations (RSs) to advertising ISATAP interfaces in the PRL. The message also includes an IP authentication Header.
manner of selecting PRL(i)'s for solicitation is up to the
implementation. Hosts add the following variable to support the
solicitation process:
MinRouterSolicitInterval 6.3.1.2 Validation of Neighbor Solicitations
Minimum time in seconds between successive solicitations of the
same advertising ISATAP interface. It SHOULD be no less than 900
seconds.
Default: 900 seconds To the list of validity checks for Neighbor Advertisement (NA)
messages ([RFC2461], section 7.1.2), ISATAP interfaces add:
RS messages use a link-local unicast address from the ISATAP o If the message includes a Target Link Layer Address Option, the
interface as the IPv6 source address. message also includes an IP authentication Header.
6.3.4.2 Router Advertisement Processing 6.3.2 Address Resolution
RAs received from a member of the PRL (i.e., RAs with an ISATAP IPv6 The specification in ([RFC2461], section 7.2) is used. NS and NA
source address that embeds V4ADDR(i) for some PRL(i)) are processed messages MAY omit the source/target link layer address option when
exactly as specified in ([RFC2461], section 6.3.4). Additionally, the source/target is an ISATAP address. ISATAP addresses for which
hosts reset TIMER(i) to schedule the next solicitation event (see: the neighbor's link-layer address cannot otherwise be determined
Section 6.3.4.1). Let "MIN_LIFETIME" be the minimum value in the (i.e., from the neighbor cache or a link layer address option in a
Router Lifetime or the lifetime(s) encoded in options included in the received packet) are resolved to link-layer addresses by a static
RA message. Then, TIMER(i) is reset as follows: computation, i.e., the last four octets are treated as an IPv4
address.
TIMER(i) = MAX((0.5 * MIN_LIFETIME), MinRouterSolicitInterval) 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.
RAs received from a router other than a member of the PRL are As specified in ([RFC2461], section 7.2.4), all nodes MUST send
processed as specified in ([RFC2461], section 6.3.4) except that any solicited neighbor advertisements on ISATAP interfaces.
RA contents ([RFC2461], section 6.2.3) that would alter ISATAP link
parameters are silently ignored. In particular, non-zero values in 6.3.3 Neighbor Unreachability Detection
the Router Lifetime, M and O flags, Cur Hop Limit, Reachable Time,
and Retrans Timer as well as prefix options with the L and/or A bits Hosts SHOULD perform Neighbor Unreachability Detection as specified
set are ignored. If the MTU option is present, the option's value in ([RFC2461], section 7.3). Routers MAY perform neighbor
SHOULD be stored in a per-neighbor cache entry for the source of the unreachability detection, but this might not scale in all
RA; it MUST NOT be copied into LinkMTU for the ISATAP link. environments.
6.4 Redirect Function
To the list of validity checks for Redirect messages (([RFC2461],
section 8.1), ISATAP interfaces add:
o If the message includes a Target Link Layer Address Option, the
message also includes an IP authentication Header.
7. Address Autoconfiguration 7. Address Autoconfiguration
Hosts invoke stateless address autoconfiguration under the conditions ISATAP interfaces use the address autoconfiguration mechanisms
specified in ([RFC2462], sections 5.5). specified in [RFC2462] with the following exceptions:
Hosts invoke stateful address autoconfiguration under the conditions 7.1 Address Lifetime Expiry
specified in ([RFC2462], section 5.5). When DHCPv6 [RFC3315] is used,
hosts send messages to the "All_DHCP_Relay_Agents_and_Servers"
multicast address ([RFC3315], sections 1.2 and 1.3). Sending
implementations map the "All_DHCP_Relay_Agents_and_Servers" multicast
address to a link-layer (IPv4) address by selecting V4ADDR(i) for
some PRL(i).
When the site supports the DHCPv6 service, the server/relay function The specification in ([RFC2462], section 5.5.4) is used, except that
MUST be deployed equally on each router that is a member of the PRL. 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 8. IANA Considerations
The IANA is advised to specify construction rules for IEEE EUI-64 The IANA is advised to specify construction rules for IEEE EUI-64
addresses formed from the Organizationally Unique Identifier (OUI) addresses formed from the Organizationally Unique Identifier (OUI)
"00-00-5E" in the IANA "ethernet-numbers" registry. The non-normative "00-00-5E" in the IANA "ethernet-numbers" registry. The non-normative
text in Appendix B is offered as an example specification. text in Appendix B is offered as an example specification.
9. Security considerations 9. Security considerations
ISATAP site border routers MUST implement IPv6 and IPv4 ingress The security considerations in [RFC2461][RFC2462][MECH] apply.
filtering and in particular MUST discard any packets originating from
outside of the site that use an IP address from the site as the
source address. Additionally, site border routers MUST implement
ip-protocol-41 filtering by not allowing packets for that protocol in
and out of the site. Finally, site border routers MUST NOT forward
any packets with local-use source or destination addresses outside of
the site ([RFC3513], section 2.5.6).
Even with IPv4 and IPv6 ingress filtering, reflection attacks can
originate from compromised nodes within an ISATAP site that spoof
IPv6 source addresses. Security mechanisms for reflection attack
mitigation SHOULD be used in routers with advertising ISATAP
interfaces. At a minimum, site border routers SHOULD log potential
source address spoofing cases.
Site administrators maintain a list of IPv4 addresses representing
advertising ISATAP interfaces and make them available via one or more
of the mechanisms described in Section 6.3.1. The list can include
IPv4 anycast address(es) but administrators are advised to consider
operational implications of anycast (e.g., see: [RFC1546]).
ISATAP addresses do not support privacy extensions for stateless Additionally, site administrators MUST ensure that lists of IPv4
address autoconfiguration [RFC3041]. addresses representing the advertising ISATAP interfaces of PRL
members are well maintained.
10. Acknowledgements 10. Acknowledgments
Portions of this work were derived from SRI International internal Most of the basic ideas in this document are not original; the
funds and government contracts. Government sponsors include Monica 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. Farah-Stapleton and Russell Langan (U.S. Army CECOM ASEO), and Dr.
Allen Moshfegh (U.S. Office of Naval Research). SRI International Allen Moshfegh (U.S. Office of Naval Research). SRI International
sponsors include Dr. Mike Frankel, J. Peter Marcotullio, Lou sponsors include Dr. Mike Frankel, J. Peter Marcotullio, Lou
Rodriguez, and Dr. Ambatipudi Sastry. Rodriguez, and Dr. Ambatipudi Sastry.
The following are acknowledged for providing peer review input: Jim The following are acknowledged for providing peer review input: Jim
Bound, Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader, Bound, Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader,
Ole Troan, Vlad Yasevich. Ole Troan, Vlad Yasevich.
The following additional individuals are acknowledged for their The following are acknowledged for their significant contributions:
contributions: Rich Draves, Alain Durand, Nathan Lutchansky, Karen Alain Durand, Hannu Flinck, Jason Goldschmidt, Nathan Lutchansky,
Nielsen, Mohan Parthasarathy, Art Shelest, Pekka Savola, Margaret Karen Nielsen, Mohan Parthasarathy, Chirayu Patel, Art Shelest, Pekka
Wasserman, Brian Zill. Savola, Margaret Wasserman, Brian Zill.
The authors also acknowledge the work of Quang Nguyen [VET] under the The authors acknowledge the work of Quang Nguyen [VET] under the
guidance of Dr. Lixia Zhang that proposed very similar ideas to those guidance of Dr. Lixia Zhang that proposed very similar ideas to those
that appear in this document. This work was first brought to the that appear in this document. This work was first brought to the
authors' attention on September 20, 2002. authors' attention on September 20, 2002.
Normative References 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 [MECH] Gilligan, R. and E. Nordmark, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", draft-ietf-v6ops-mech-v2-00 for IPv6 Hosts and Routers", draft-ietf-v6ops-mech-v2-00
(work in progress), February 2003. (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 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981. 1981.
[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, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998. (IPv6) Specification", RFC 2460, December 1998.
[RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor [RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998. 1998.
[RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998. Autoconfiguration", RFC 2462, December 1998.
[RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6
(IPv6) Addressing Architecture", RFC 3513, April 2003.
Informative References 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 [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[RFC1546] Partridge, C., Mendez, T. and W. Milliken, "Host [RFC1122] Braden, R., "Requirements for Internet Hosts -
Anycasting Service", RFC 1546, November 1993. Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and
E. Lear, "Address Allocation for Private Internets", BCP E. Lear, "Address Allocation for Private Internets", BCP
5, RFC 1918, February 1996. 5, RFC 1918, February 1996.
[RFC2022] Armitage, G., "Support for Multicast over UNI 3.0/3.1
based ATM Networks", RFC 2022, November 1996.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC2491] Armitage, G., Schulter, P., Jork, M. and G. Harter, "IPv6 [RFC2491] Armitage, G., Schulter, P., Jork, M. and G. Harter, "IPv6
over Non-Broadcast Multiple Access (NBMA) networks", RFC over Non-Broadcast Multiple Access (NBMA) networks", RFC
2491, January 1999. 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 [RFC3041] Narten, T. and R. Draves, "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6", RFC 3041, Stateless Address Autoconfiguration in IPv6", RFC 3041,
January 2001. January 2001.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
M. Carney, "Dynamic Host Configuration Protocol for IPv6 M. Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003. (DHCPv6)", RFC 3315, July 2003.
[RFC3582] Abley, J., Black, B. and V. Gill, "Goals for IPv6 [RFC3582] Abley, J., Black, B. and V. Gill, "Goals for IPv6
Site-Multihoming Architectures", RFC 3582, August 2003. Site-Multihoming Architectures", RFC 3582, August 2003.
skipping to change at page 12, line 45 skipping to change at page 15, line 45
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052-6399 Redmond, WA 98052-6399
US US
Phone: +1 425 703 8835 Phone: +1 425 703 8835
EMail: dthaler@microsoft.com EMail: dthaler@microsoft.com
Appendix A. Major Changes Appendix A. Major Changes
changes from version 14 to version 15: Major changes from earlier versions to version 16:
o several editorial changes
o revised Security; IANA considerations
o revised Section 6.3.4.2
o added new section on ingress filtering
o revised stateful autoconfiguration and moved to new section
o removed overly-restrictive text at end of Section 6.3.4.1
changes from version 13 to version 14:
o removed applicability statement; applicability TBD by v6ops
o updated deployment/site admin sections; moved to appendices
o new text on "L" bit in prefix options in section 7.3.4.2
o removed extraneous text in Security Considerations
o fixed "layering bug" in section 7.3.4.3
o revised "ISATAP address" definition
o updated references for RFC 3315; 3513
changes from earlier versions to version 13:
o Revised ISATAP interface/link terminology
o Returned to using symbolic reference names
o Revised MTU section; moved non-normative MTU text to separate
document
o Added multicast/anycast subsection
o Revised PRL initialization
o Updated neighbor discovery, security consideration sections
o Rearranged/revised sections 5, 6, 7
o Added stateful autoconfiguration mechanism
o Normative references to RFC 2491, RFC 2462
o Moved non-normative MTU text to appendix C o dropped "underlying link" from terminology.
o clarified address resolution, Neighbor Unreachability Detection o specified multicast mappings.
o specified MTU/MRU requirements
o Addressed operational issues identified in 05 based on discussion o specified layer address option format.
between co-authors
o Clarified ambiguous text per comments from Hannu Flinck; Jason o specified setting of "u" bit in interface id's.
Goldschmidt
o Moved historical text in section 4.1 to Appendix B in response to o removed obsoleted appendix sections.
comments from Pekka Savola
o Identified operational issues for anticipated deployment scenarios o re-organized major sections to match normative references.
o Included reference to Quang Nguyen work o revised neighbor discovery, address autoconfiguration, security
considerations sections. Added new subsections on interface
management, decapsulation/filtering, address lifetime expiry.
Appendix B. Rationale for Interface Identifier Construction Appendix B. Interface Identifier Construction
ISATAP specifies an EUI64-format address construction for the This section provides an example specification for constructing EUI64
Organizationally-Unique Identifier (OUI) owned by the Internet addresses from the Organizationally-Unique Identifier (OUI) owned by
Assigned Numbers Authority (IANA). This format (given below) is used the Internet Assigned Numbers Authority (IANA). It can be used to
to construct both native EUI64 addresses for general use and modified construct both modified EUI-64 format interface identifiers for IPv6
EUI-64 format interface identifiers for IPv6 unicast addresses: unicast addresses ([ADDR-ARCH], section 2.5.1) and "native" EUI64
addresses for future use:
|0 2|2 3|3 3|4 6| |0 2|2 3|3 3|4 6|
|0 3|4 1|2 9|0 3| |0 3|4 1|2 9|0 3|
+------------------------+--------+--------+------------------------+ +------------------------+--------+--------+------------------------+
| OUI ("00-00-5E"+u+g) | TYPE | TSE | TSD | | OUI ("00-00-5E"+u+g) | TYPE | TSE | TSD |
+------------------------+--------+--------+------------------------+ +------------------------+--------+--------+------------------------+
Where the fields are: Where the fields are:
OUI IANA's OUI: 00-00-5E with 'u' and 'g' bits (3 octets) OUI IANA's OUI: 00-00-5E with "u" and "g" bits (3 octets)
TYPE Type field; specifies use of (TSE, TSD) (1 octet) TYPE Type field; specifies use of (TSE, TSD) (1 octet)
TSE Type-Specific Extension (1 octet) TSE Type-Specific Extension (1 octet)
TSD Type-Specific Data (3 octets) TSD Type-Specific Data (3 octets)
And the following interpretations are specified based on TYPE: And the following interpretations are specified based on TYPE:
TYPE (TSE, TSD) Interpretation TYPE (TSE, TSD) Interpretation
---- ------------------------- ---- -------------------------
0x00-0xFD RESERVED for future IANA use 0x00-0xFD RESERVED for future IANA use
0xFE (TSE, TSD) together contain an embedded IPv4 address 0xFE (TSE, TSD) together contain an IPv4 address
0xFF TSD is interpreted based on TSE as follows: 0xFF TSD is interpreted based on TSE as follows:
TSE TSD Interpretation TSE TSD Interpretation
--- ------------------ --- ------------------
0x00-0xFD RESERVED for future IANA use 0x00-0xFD RESERVED for future IANA use
0xFE TSD contains 24-bit EUI-48 intf id 0xFE TSD contains 24-bit EUI-48 intf id
0xFF RESERVED by IEEE/RAC 0xFF RESERVED by IEEE/RAC
Thus, if TYPE=0xFE, TSE is an extension of TSD. If TYPE=0xFF, TSE is Using this example specification, if TYPE=0xFE, then TSE is an
an extension of TYPE. Other values for TYPE (thus, other extension of TSD. If TYPE=0xFF, then TSE is an extension of TYPE.
interpretations of TSE, TSD) are reserved for future IANA use. (Other values for TYPE, and other interpretations of TSE, TSD are
reserved for future IANA use.) When TYPE='0xFE' the EUI64 address
The above specification is compatible with all aspects of EUI64, embeds an IPv4 address, encoded in network byte order.
including support for encapsulating legacy EUI-48 interface
identifiers (e.g., an IANA EUI-48 format multicast address such as:
'01-00-5E-01-02-03' is encapsulated as: '01-00-5E-FF-FE-01-02-03').
But, the specification also provides a special TYPE (0xFE) to
indicate an IPv4 address is embedded. Thus, when the first four
octets of an IPv6 interface identifier are: '00-00-5E-FE' (note: the
'u/l' bit MUST be 0) the interface identifier is said to be in
"ISATAP format" and the next four octets embed an IPv4 address
encoded in network byte order.
Appendix C. Deployment Considerations
Hosts can enable ISATAP, e.g., when native IPv6 service is
unavailable. When native IPv6 service is acquired, hosts can
discontinue the ISATAP router solicitation process (Section 6.3.4)
and/or allow associated state to expire (see: [RFC2461], section 5.3
and [RFC2462], section 5.5.4). In this case, any associated addresses
added to the DNS should also be removed.
Routers can configure both native IPv6 and ISATAP interfaces over the
same physical link. The prefixes used on each interface will be
distinct, and normal IPv6 routing between the interfaces can occur.
Routers can obtain IPv6 prefix delegations from a server via an
ISATAP interface and advertise the delegated prefix(es) on other IPv6
interface(s).
Responsible administration can reduce control traffic overhead
associated with router and prefix discovery.
Appendix D. Other Considerations
The Potential Router List (PRL) contains the IPv4 addresses of
advertising ISATAP interfaces on site border routers, and the
specification mandates that nodes only accept Router Advertisement
(RA) parameters that alter the ISATAP link (e.g., default router
list, on-link prefix list, LinkMTU, etc.) if they are sent by a
member of the PRL. However, the specification allows any node on the
ISATAP link to send "other" parameters in RAs and also allows any
node on the ISATAP link to act as a (non-default) IPv6 router, e.g.,
if the node is configured as a router for its other IPv6 links.
These aspects of the specification allow useful functionality,
including the ability for ISATAP nodes other than PRL members to
serve as routers for "stub" IPv6 networks, the ability for ISATAP
nodes to send IPv6 packets with non-ISATAP source addresses (e.g.,
RFC 3401 privacy addresses), etc. But, allowing this functionality
prevents ISATAP nodes from perform effective ingress filtering for
IPv6 source addresses in packets they receive. Instead, the nodes
must trust that: 1) site border routers are performing ingress
filtering, and 2) malicious nodes are effectively denied access to
the link.
Additionally, the specification expects that that IPv4 addresses are For Modified EUI64 format interface identifiers in IPv6 unicast
uniquely assigned within the ISATAP site. 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".
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
 End of changes. 

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