draft-ietf-dna-hosts-01.txt   draft-ietf-dna-hosts-02.txt 
DNA Working Group S. Narayanan DNA Working Group S. Narayanan
Internet-Draft Panasonic Internet-Draft Panasonic
Expires: December 25, 2005 G. Daley Expires: April 27, 2006 G. Daley
Monash University CTIE Monash University CTIE
N. Montavont N. Montavont
LSIIT - ULP LSIIT - ULP
June 23, 2005 October 24, 2005
Detecting Network Attachment in IPv6 - Best Current Practices for hosts. Detecting Network Attachment in IPv6 - Best Current Practices for hosts.
draft-ietf-dna-hosts-01.txt draft-ietf-dna-hosts-02.txt
Status of this Memo Status of this Memo
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skipping to change at page 1, line 37 skipping to change at page 1, line 37
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This Internet-Draft will expire on December 25, 2005. This Internet-Draft will expire on April 27, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
Hosts experiencing rapid link-layer changes may require efficient IP Hosts experiencing rapid link-layer changes may require efficient IP
configuration change detection procedures than traditional fixed configuration change detection procedures than traditional fixed
hosts. DNA is defined as the process by which a host collects hosts. DNA is defined as the process by which a host collects
appropriate information and detects the identity of its currently appropriate information and detects the identity of its currently
attached link to ascertains the validity of its IP configuration. attached link to ascertain the validity of its IP configuration.
This document details best current practice for Detecting Network This document details best current practice for Detecting Network
Attachment in IPv6 hosts using existing Neighbor Discovery Attachment in IPv6 hosts using existing Neighbor Discovery
procedures. Since there is no explicit link identification mechanism procedures. Since there is no explicit link identification mechanism
in the existing Neighbor Discovery for IP Version 6, the document in the existing Neighbor Discovery for IP Version 6, the document
describes implicit mechanisms for identifying the current link. describes implicit mechanisms for identifying the current link.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Structure of this Document . . . . . . . . . . . . . . . . 5 1.1 Structure of this Document . . . . . . . . . . . . . . . . 4
2. Terms and Abbreviations . . . . . . . . . . . . . . . . . . . 5 2. Terms and Abbreviations . . . . . . . . . . . . . . . . . . . 4
3. Background & Motivation for DNA . . . . . . . . . . . . . . . 6 3. Background & Motivation for DNA . . . . . . . . . . . . . . . 5
3.1 Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Detecting Network Attachment Steps . . . . . . . . . . . . . . 7 4. Detecting Network Attachment Steps . . . . . . . . . . . . . . 6
4.1 Making use of Prior Information . . . . . . . . . . . . . 7 4.1 Making use of Prior Information . . . . . . . . . . . . . 7
4.2 Duplicate Address Detection . . . . . . . . . . . . . . . 8 4.2 Link identification . . . . . . . . . . . . . . . . . . . 8
4.3 Link identification . . . . . . . . . . . . . . . . . . . 9 4.2.1 Same link . . . . . . . . . . . . . . . . . . . . . . 8
4.3.1 Same link . . . . . . . . . . . . . . . . . . . . . . 9 4.2.2 Link change . . . . . . . . . . . . . . . . . . . . . 8
4.3.2 Link change . . . . . . . . . . . . . . . . . . . . . 10 4.3 IP Hosts Configuration . . . . . . . . . . . . . . . . . . 9
4.4 Multicast Listener State . . . . . . . . . . . . . . . . . 10 4.4 Duplicate Address Detection . . . . . . . . . . . . . . . 9
4.5 Reachability detection . . . . . . . . . . . . . . . . . . 10 4.5 Multicast Listener State . . . . . . . . . . . . . . . . . 10
4.6 Reachability detection . . . . . . . . . . . . . . . . . . 10
5. Initiation of DNA Procedures . . . . . . . . . . . . . . . . . 11 5. Initiation of DNA Procedures . . . . . . . . . . . . . . . . . 11
5.1 Actions Upon Hint Reception . . . . . . . . . . . . . . . 12 5.1 Actions Upon Hint Reception . . . . . . . . . . . . . . . 12
5.2 Hints Due to Network Layer Messages . . . . . . . . . . . 12 5.2 Hints Due to Network Layer Messages . . . . . . . . . . . 12
5.3 Handling Hints from Other Layers . . . . . . . . . . . . . 13 5.3 Handling Hints from Other Layers . . . . . . . . . . . . . 12
5.4 Timer and Loss Based Hints . . . . . . . . . . . . . . . . 13 5.4 Timer and Loss Based Hints . . . . . . . . . . . . . . . . 13
5.5 Simultaneous Hints . . . . . . . . . . . . . . . . . . . . 14 5.5 Simultaneous Hints . . . . . . . . . . . . . . . . . . . . 13
5.6 Hint Validity and Hysteresis . . . . . . . . . . . . . . . 14 5.6 Hint Management for Inactive Hosts . . . . . . . . . . . . 14
5.7 Hint Management for Inactive Hosts . . . . . . . . . . . . 15
6. IP Hosts Configuration . . . . . . . . . . . . . . . . . . . . 15
6.1 Router and Prefix list . . . . . . . . . . . . . . . . . . 15
6.2 IPv6 Addresses . . . . . . . . . . . . . . . . . . . . . . 16
6.2.1 Autoconfiguration . . . . . . . . . . . . . . . . . . 16
6.2.2 Dynamic Host Configuration . . . . . . . . . . . . . . 16
6.3 Neighbor cache . . . . . . . . . . . . . . . . . . . . . . 17
6.4 Mobility Management . . . . . . . . . . . . . . . . . . . 17
7. Complications to Detecting Network Attachment . . . . . . . . 18
7.1 Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 18
7.2 Router Configurations . . . . . . . . . . . . . . . . . . 18
7.3 Overlapping Coverage . . . . . . . . . . . . . . . . . . . 18
7.4 Multicast Snooping . . . . . . . . . . . . . . . . . . . . 19
7.5 Link Partition . . . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 6. Complications to Detecting Network Attachment . . . . . . . . 14
8.1 Authorization and Detecting Network Attachment . . . . . . 20 6.1 Packet Loss . . . . . . . . . . . . . . . . . . . . . . . 14
8.2 Addressing . . . . . . . . . . . . . . . . . . . . . . . . 20 6.2 Router Configurations . . . . . . . . . . . . . . . . . . 15
6.3 Overlapping Coverage . . . . . . . . . . . . . . . . . . . 15
6.4 Multicast Snooping . . . . . . . . . . . . . . . . . . . . 15
6.5 Link Partition . . . . . . . . . . . . . . . . . . . . . . 16
9. Constants . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 21 7.1 Authorization and Detecting Network Attachment . . . . . . 16
7.2 Addressing . . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 8. Constants . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1 Normative References . . . . . . . . . . . . . . . . . . . 21
11.2 Informative References . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 23 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1 Normative References . . . . . . . . . . . . . . . . . . . 17
10.2 Informative References . . . . . . . . . . . . . . . . . . 18
A. Example State Transition Diagram . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . 25 Intellectual Property and Copyright Statements . . . . . . . . 21
1. Introduction 1. Introduction
When operating in changing environments, IPv6 hosts may experience When operating in changing environments, IPv6 hosts may experience
variations in reachability or configuration state over time. For variations in reachability or configuration state over time. For
hosts accessing the Internet over wireless media, such changes may be hosts accessing the Internet over wireless media, such changes may be
caused by changes in wireless propagation or host motion. caused by changes in wireless propagation or host motion.
Detecting Network Attachment (DNA) in IPv6 is the task of checking Detecting Network Attachment (DNA) in IPv6 is the task of checking
for changes in the validity of a host's IP configuration [15]. for changes in the validity of a host's IP configuration [15].
Changes may occur on establishment or disconnection of a link-layer. Changes may occur on establishment or disconnection of a link-layer.
For newly connected interfaces, they may be on a link different from For newly connected interfaces, they may be on a link different from
the existing configuration of the node. the existing configuration of the node.
In these and other cases, IP addressing and default routing In such cases, IP addressing and default routing configuration of the
configuration of the node may become invalid preventing packet node may become invalid preventing packet transfer. DNA uses IPv6
transfer. DNA uses IPv6 Neighbour Discovery to provide information Neighbour Discovery to provide information about the reachability and
about the reachability and identity of the link. identity of the link.
DNA focuses on determining whether the current configuration is DNA focuses on determining whether the current configuration is
valid, leaving the actual practice of re-configuration to other valid, leaving the actual practice of re-configuration to other
subsystems, if the current configuration is invalid. subsystems, if the current configuration is invalid.
This document presents the best current practices for IPv6 hosts to This document presents the best current practices for IPv6 hosts to
address the task of Detecting Network Attachment in changing and address the task of Detecting Network Attachment in changing and
wireless environments. wireless environments.
1.1 Structure of this Document 1.1 Structure of this Document
Section 3 of this document provides background and motivation for Section 3 of this document provides background and motivation for
Detecting Network Attachment. Detecting Network Attachment.
Elaboration of specific practices for hosts in detecting network Elaboration of specific practices for hosts in detecting network
attachment continues in Section 4, while Section 5 discuss the attachment continues in Section 4, while Section 5 discuss the
initiation of DNA procedures. initiation of DNA procedures.
Section 6 describes interactions with other protocols, particularly Section 7 provides security considerations, and details a number of
upon link-change, while Section 7 describes environmental challenges
to detection of network attachment.
Section 8 provides security considerations, and details a number of
issues which arise due to wireless connectivity and the changeable issues which arise due to wireless connectivity and the changeable
nature of DNA hosts' Internet connections. nature of DNA hosts' Internet connections.
2. Terms and Abbreviations 2. Terms and Abbreviations
Access network: A network where hosts are present. Especially, a Access network: A network where hosts are present. Especially, a
network used for the support of visiting wireless hosts. network used for the support of visiting wireless hosts.
Attachment: The process of entering a new cell. Attachment (and Attachment: The process of entering a new cell. Attachment (and
detachment) may cause a link-change. detachment) may cause a link-change.
Cell: A system constituted by the propagation range of a wireless Cell: A system constituted by the propagation range of a wireless
base station and its serviced hosts. Dependent on topology, one base station and its serviced hosts. Dependent on topology, one
or many cells may be part of the same link. or many cells may be part of the same link.
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Wireless Medium: A physical layer which incorporates free space Wireless Medium: A physical layer which incorporates free space
electromagnetic or optical propagation. Such media are electromagnetic or optical propagation. Such media are
susceptible to mobility and interference effects, potentially susceptible to mobility and interference effects, potentially
resulting in high packet loss probabilities. resulting in high packet loss probabilities.
3. Background & Motivation for DNA 3. Background & Motivation for DNA
Hosts on the Internet may be connected by various media. It has Hosts on the Internet may be connected by various media. It has
become common that hosts have access through wireless media and are become common that hosts have access through wireless media and are
mobile, and have a variety of interfaces through which internet mobile. The frequency of configuration change for wireless and
connectivity is provided. The frequency of configuration change for nomadic devices are high due to the vagaries of wireless propagation
wireless and nomadic devices are high due to the vagaries of wireless or the motion of the hosts themselves. Detecting Network Attachment
propagation or the motion of the hosts themselves. Detecting Network is a strategy to assist such rapid configuration changes by
Attachment is a strategy to assist such rapid configuration changes determining whether they are required.
by determining whether they are required.
Due to these frequent link-layer changes, an IP configuration change Due to these frequent link-layer changes, an IP configuration change
detection mechanism for DNA needs to be efficient and rapid to avoid detection mechanism for DNA needs to be efficient and rapid to avoid
unnecessary configuration delays upon link-change. unnecessary configuration delays upon link-change.
In an wireless environment, there will typically be a trade-off In a wireless environment, there will typically be a trade-off
between configuration delays and the channel bandwidth utilized or between configuration delays and the channel bandwidth utilized or
host's energy used to transmit packets. This trade-off affects host's energy used to transmit packets. This trade-off affects
choices as to whether hosts probe for configuration information, or choices as to whether hosts probe for configuration information, or
wait for network information. DNA seeks to assist hosts by providing wait for network information. DNA seeks to assist hosts by providing
information about network state, which may allow hosts to information about network state, which may allow hosts to
appropriately make decisions regarding such trade-offs. appropriately make decisions regarding such trade-offs.
Even though DNA is restricted to determining whether change is Even though DNA is restricted to determining whether change is
needed, in some circumstances the process of obtaining information needed, in some circumstances the process of obtaining information
for the new configuration may occur simultaneously with the detection for the new configuration may occur simultaneously with the detection
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The default router address is link-local address and hence may The default router address is link-local address and hence may
only be unique within one link [1]. only be unique within one link [1].
While neighbor cache entries are valid only on a single link, While neighbor cache entries are valid only on a single link,
link-local addresses may be duplicated across many links, and only link-local addresses may be duplicated across many links, and only
global addressing can be used to identify if there is a link global addressing can be used to identify if there is a link
change. change.
4. Detecting Network Attachment Steps 4. Detecting Network Attachment Steps
An IPv6 host SHOULD follow the following steps when they receive a
hint (see Section 5) indicating the possibility of link change.
Try making use of prior information stored related to the links
the host visited in the past (see Section 4.1).
If the prior information implies no link change, the host MAY
conduct reachability detection (see Section 4.6) to one of the
default routers it is using, otherwise no action is needed.
If the prior information implies that there is a link change or
there is no useful prior information available, follow the
procedure below.
Mark all the IPv6 addresses in use as optimistic.
Conduct link identification. (See Section 4.2).
If the link has changed
Change the IP configuration parameters of the host (see
Section 4.3).
Configure new address and conduct duplicate address detection
(see Section 4.4).
Conduct multicast listner discovery (see Section 4.5).
If the link has NOT changed
Restore the address configuration state of all the IPv6
addresses known to be on the link.
Conduct reachability detection to one of the default routers
(see Section 4.6).
4.1 Making use of Prior Information 4.1 Making use of Prior Information
A device that has recently been attached to a particular wireless A device that has recently been attached to a particular wireless
base station may still have state regarding the IP configuration base station may still have state regarding the IP configuration
valid for use on that link. This allows a host to begin any valid for use on that link. This allows a host to begin any
configuration procedures before checking the ongoing validity and configuration procedures before checking the ongoing validity and
security of the parameters. security of the parameters.
The experimental protocols FMIPv6 [19] and CARD [20] each provide The experimental protocols FMIPv6 [19] and CARD [20] each provide
ways to generate such information using network-layer signaling, ways to generate such information using network-layer signaling,
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A IP host MAY store L2 to L3 mapping information for the links for a A IP host MAY store L2 to L3 mapping information for the links for a
period of time in order to use the information in the future. When a period of time in order to use the information in the future. When a
host attaches itself to a point-of-attachment for which it has an L2 host attaches itself to a point-of-attachment for which it has an L2
to L3 mapping, if the stored record doesn't contain the prefix the to L3 mapping, if the stored record doesn't contain the prefix the
host is using, the host SHOULD conclude that it has changed link and host is using, the host SHOULD conclude that it has changed link and
initiate a new configuration procedure. initiate a new configuration procedure.
If the host finds the prefix it is using in the stored record, a host If the host finds the prefix it is using in the stored record, a host
MAY conclude that it is on the same link, but SHOULD undertake MAY conclude that it is on the same link, but SHOULD undertake
reachability testing as described in Section 4.5. In this case, the reachability testing as described in Section 4.6. In this case, the
host MUST undertake Duplicate Address Detection [3][8] to confirm host MUST undertake Duplicate Address Detection [3][8] to confirm
that there are no duplicate addresses on the link. that there are no duplicate addresses on the link.
The host MUST age this cached information based on the possibility The host MUST age this cached information based on the possibility
that the link's configuration has changed and MUST NOT store that the link's configuration has changed and MUST NOT store
information beyond either the remaining router or address lifetime or information beyond either the remaining router or address lifetime or
(at the outside) MAC_CACHE_TIME time-units. (at the outside) MAC_CACHE_TIME time-units.
If the assumptions attached to the stored configuration are incorrect 4.2 Link identification
the configuration cost may be increased, or even cause disruption of
services to other devices. Hosts MUST NOT cause any disruption of
the IP connectivity to other devices due to the invalidity or
staleness of their configuration.
4.2 Duplicate Address Detection
When a host connects to a new link, it needs to create a link-local
address. But to ensure that the link-local address is unique on a
link, Duplication Address Detection (DAD) MUST be performed [3] by
sending NS targeted at the link-local address undergoing validation.
Optimistic Duplicate Address Detection allows addresses to be used
while they are being checked, without marking addresses as tentative.
Procedures defined in optimistic DAD [8] ensure that persistent
invalid neighbour cache entries are not created. This may allow
faster DNA procedures, by avoiding use of unspecified source
addresses in RS's and consequently allowing unicast Router
Advertisements responses [8]. It is RECOMMENDED that hosts follow
the recommendations of optimistic DAD [8] to reduce the DAD delay.
Link-local addresses SHOULD be treated as either optimistic or
tentative, and globally unique addresses SHOULD NOT be used in a way
which creates neighbor cache state on their peers, while DNA
procedures are underway.
While hosts performing DNA do not know if they have arrived on a new
link, they SHOULD treat their addresses as if they were. The
different treatment of IP addressing comes from the fact that on the
global addresses cannot have an address conflict if they move to a
topologically incorrect network where link-local addresses may. Even
though global addresses will not collide, the incorrect creation of
neighbor cache entries on legacy peers may cause them some harm.
In the case that the host has not changed link and if the time
elapsed since the hint is less than the DAD completion time (minus a
packet transmission and propagation time), the host MAY reclaim the
address by sending Neighbor Advertisement messages as if another host
had attempted DAD while the host was away. This will prevent DAD
completion by another node upon NA reception.
If a host has not been present on a link to defend its address, and
has been absent for a full DAD delay (minus transmission time) the
host MUST undertake the full DAD procedure for each address from that
link it wishes to configure [3][8].
4.3 Link identification
4.3.1 Same link 4.2.1 Same link
An IP host MUST conclude that it is on the same link if any of the An IP host MUST conclude that it is on the same link if any of the
following events happen. following events happen.
Reception of a RA with the prefix known to be on the link from one Reception of a RA with the prefix known to be on the link from one
of its default router address, even if it is the link-local of its default router address, even if it is the link-local
address of the router. address of the router.
Reception of a RA from a known router's global address, present in Reception of a RA from a known router's global address, present in
a Prefix Information Option containing the R-"Router Address" flag a Prefix Information Option containing the R-"Router Address" flag
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Reception of a RA with a prefix that is known to be on the current Reception of a RA with a prefix that is known to be on the current
link. link.
Reception of data packets addressed to its current global address Reception of data packets addressed to its current global address
if the message was sent from or through a device which is known to if the message was sent from or through a device which is known to
be fixed (such as a router). be fixed (such as a router).
Confirmation of a global address entry with the Router 'R' flag Confirmation of a global address entry with the Router 'R' flag
set in its neighbor cache[1]. set in its neighbor cache[1].
4.3.2 Link change 4.2.2 Link change
A host makes use of Router Discovery messages to determine that it A host makes use of Router Discovery messages to determine that it
has moved to a new link. Since the content of an existing received has moved to a new link. Since the content of an existing received
RA is not sufficient to identify the absence of any other prefix, RA is not sufficient to identify the absence of any other prefix,
additional inference is required for fast and accurate link-change additional inference is required for fast and accurate link-change
detection. detection.
Complete Prefix Lists provide a robust mechanism for link-change Complete Prefix Lists provide a robust mechanism for link-change
detection with even unmodified non-DNA routers if link-layer detection if link-layer indications are available [24][18]. These
indications are available [24][18]. These procedures provide procedures provide mechanisms to build confidence that a host knows
mechanisms to build confidence that a host knows all of a link's all of a link's prefixes and so may rapidly identify a newly received
prefixes and so may rapidly identify a newly received RA as being RA as being from a different link.
from a different link.
A host SHOULD maintain a complete prefix list as recommended by A host SHOULD maintain a complete prefix list as recommended by
[24] to identify if the link has changed. [24] to identify if the link has changed.
4.4 Multicast Listener State 4.3 IP Hosts Configuration
Various protocols within IPv6 provide their own configuration
processes. A host will have collected various configuration
information using these protocols during its presence on a link.
Following is the list of steps the host needs to take if a link-
change has occured.
Invalidation of router and prefix list: On determining that link-
change has occurred, the host SHOULD remove entries from the
default router list removed which are related to unreachable
routers. Destination cache entries using information from these
routers SHOULD be removed [1]. If no eligible default routers are
in the default router list, Router Solicitations MAY be sent, in
order to discover new routers.
Invalidation of IPv6 addresses: Addresses which relate to invalidated
prefix list entries SHOULD be removed.
Removing neighbor cache entries: When link change occurs, the
reachability of all existing neighbor cache entries is likely to
be invalidated, if link change prevents packet reception from an
old link. For these links, the neighbor cache entries SHOULD be
removed when a host moves to a new link (although it MAY be
possible to keep keying and authorization information for such
hosts cached on a least-recently-used basis [7]).
Completion of DAD for Link-Local Addresses: Link-local addresses used
for DNA purposes may be tentative or optimistic at the completion
of change detection procedures. Where link-change has occurred,
these processes SHOULD continue to completion, as described in [3]
and [8].
Initiating mobility signaling: Any signaling required to restore end-
to-end communications occurs after DNA, if link-change has
occurred.
4.4 Duplicate Address Detection
When a host connects to a new link, it needs to create a link-local
address. But to ensure that the link-local address is unique on a
link, Duplication Address Detection (DAD) MUST be performed [3] by
sending NS targeted at the link-local address undergoing validation.
Optimistic Duplicate Address Detection allows addresses to be used
while they are being checked, without marking addresses as tentative.
Procedures defined in optimistic DAD [8] ensure that persistent
invalid neighbour cache entries are not created. This may allow
faster DNA procedures, by avoiding use of unspecified source
addresses in RS's and consequently allowing unicast Router
Advertisements responses [8]. It is RECOMMENDED that hosts follow
the recommendations of optimistic DAD [8] to reduce the DAD delay.
4.5 Multicast Listener State
Multicast routers on a link are aware of which groups are in use Multicast routers on a link are aware of which groups are in use
within a link. This information is used to undertake initiation of within a link. This information is used to undertake initiation of
multicast routing for off-link multicast sources to the link [9] multicast routing for off-link multicast sources to the link [9]
[11]. [11].
When a node arrives on a link, it may need to send Multicast Listener When a node arrives on a link, it MAY need to send Multicast Listener
Discovery (MLD) reports, if the multicast stream is not already being Discovery (MLD) reports, if the multicast stream is not already being
received on the link. If it is an MLDv2 node it SHOULD send state received on the link. If it is an MLDv2 node it SHOULD send state
change reports upon arrival on a link [11]. change reports upon arrival on a link [11].
Since the identity of the link is tied to the presence and identity Since the identity of the link is tied to the presence and identity
of routers, initiation of these procedures may be undertaken when DNA of routers, initiation of these procedures may be undertaken when DNA
procedures have been completed. In the absence of received data procedures have been completed. In the absence of received data
packets from a multicast stream, it is unlikely that a host will be packets from a multicast stream, it is unlikely that a host will be
able to determine if the multicast stream is being received on a new able to determine if the multicast stream is being received on a new
link, and will have to send state change reports, in addition to link, and will have to send state change reports, in addition to
responses to periodic multicast queries [9] [11]. responses to periodic multicast queries [9] [11].
For link scoped multicast, reporting needs to be done to ensure that For link scoped multicast, reporting needs to be done to ensure that
packet reception in the link is available due to multicast snoopers. packet reception in the link is available due to multicast snoopers.
Some interaction is possible when sending messages for the purpose of Some interaction is possible when sending messages for the purpose of
DNA on a network where multicast snooping is in use. This issue is DNA on a network where multicast snooping is in use. This issue is
described in Section 7.4. described in Section 6.4.
4.5 Reachability detection 4.6 Reachability detection
If an IP node needs to confirm bi-directional reachability to its If an IP node needs to confirm bi-directional reachability to its
default router either a NS-NA or an RS-RA message exchange can be default router either a NS-NA or an RS-RA message exchange can be
used to conduct reachability testing. It is notable that the choice used to conduct reachability testing. It is notable that the choice
of whether the messages are addressed to multicast or unicast address of whether the messages are addressed to multicast or unicast address
will have different reachability implications. The reachability will have different reachability implications. The reachability
implications from the hosts' perspective for the four different implications from the hosts' perspective for the four different
message exchanges defined by RFC 2461 [1] are presented in the table message exchanges defined by RFC 2461 [1] are presented in the table
below. The host can confirm bi-directional reachability from the below. The host can confirm bi-directional reachability from the
neighbor discovery or router discovery message exchanges except when neighbor discovery or router discovery message exchanges except when
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In some cases, hints will carry significant information (for example In some cases, hints will carry significant information (for example
a hint indicating PPP IPv6CP open state [4]), although details of the a hint indicating PPP IPv6CP open state [4]), although details of the
configuration parameters may be available only after other IP configuration parameters may be available only after other IP
configuration procedures. Implementers are encouraged to treat hints configuration procedures. Implementers are encouraged to treat hints
as though they may be incorrect, and require confirmation. as though they may be incorrect, and require confirmation.
Hosts MUST ensure that untrusted hints do not cause unnecessary Hosts MUST ensure that untrusted hints do not cause unnecessary
configuration changes, or significant consumption of host resources configuration changes, or significant consumption of host resources
or bandwidth. In order to achieve this aim, a host MAY implement or bandwidth. In order to achieve this aim, a host MAY implement
hysteresis mechanisms such as token buckets, hint weighting or hysteresis mechanisms such as token buckets, hint weighting or
holddown timers in order to limit the effect of excessive hints (see holddown timers in order to limit the effect of excessive hints.
Section 5.6).
5.1 Actions Upon Hint Reception 5.1 Actions Upon Hint Reception
Upon reception of a hint that link change detection may have Upon reception of a hint that link change detection may have
occurred, a host SHOULD send Router Solicitation messages to occurred, a host SHOULD send Router Solicitation messages to
determine the routers and prefixes which exist on a link. Hosts determine the routers and prefixes which exist on a link. Hosts
SHOULD apply rate limiting and/or hysteresis to this behaviour as SHOULD apply rate limiting and/or hysteresis to this behaviour as
appropriate to the link technology subject to the reliability of the appropriate to the link technology subject to the reliability of the
hints. hints.
skipping to change at page 12, line 43 skipping to change at page 12, line 30
Hint reception may be due to network-layer messages such as Hint reception may be due to network-layer messages such as
unexpected Router Advertisements, multicast listener queries or unexpected Router Advertisements, multicast listener queries or
ICMPv6 error messages [1][9][6]. In these cases, the authenticity of ICMPv6 error messages [1][9][6]. In these cases, the authenticity of
the messages MUST be verified before expending resources to initiate the messages MUST be verified before expending resources to initiate
DNA procedure. DNA procedure.
When a host arrives on a new link, hints received due to external IP When a host arrives on a new link, hints received due to external IP
packets will typically be due to multicast messages. Actions based packets will typically be due to multicast messages. Actions based
on multicast reception from untrusted sources are dangerous due to on multicast reception from untrusted sources are dangerous due to
the threat of multicast response flooding. This issue is discussed the threat of multicast response flooding. This issue is discussed
further in Section 8. further in Section 7.
State changes within the network-layer itself may initiate link- State changes within the network-layer itself may initiate link-
change detection procedures. Existing subsystems for router and change detection procedures. Existing subsystems for router and
neighbor discovery, address leasing and multicast reception maintain neighbor discovery, address leasing and multicast reception maintain
their own timers and state variables. Changes to the state of one or their own timers and state variables. Changes to the state of one or
more of these mechanisms may hint that link change has occurred, and more of these mechanisms may hint that link change has occurred, and
initiate detection of network attachment. initiate detection of network attachment.
5.3 Handling Hints from Other Layers 5.3 Handling Hints from Other Layers
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While these hints come from the host's own stack, such hints may While these hints come from the host's own stack, such hints may
actually be due to packet reception or non-reception events at the actually be due to packet reception or non-reception events at the
originating layers. As such, it may be possible for other devices to originating layers. As such, it may be possible for other devices to
instigate hint delivery on a host or multiple hosts deliberately, in instigate hint delivery on a host or multiple hosts deliberately, in
order to prompt packet transmission, or configuration modification. order to prompt packet transmission, or configuration modification.
Therefore, hosts SHOULD NOT change their configuration state based on Therefore, hosts SHOULD NOT change their configuration state based on
hints from other protocol layers. A host MAY adopt an appropriate hints from other protocol layers. A host MAY adopt an appropriate
link change detection strategy based upon hints received from other link change detection strategy based upon hints received from other
layers, with suitable caution and hysteresis, as described in layers, with suitable caution and hysteresis.
Section 5.6.
5.4 Timer and Loss Based Hints 5.4 Timer and Loss Based Hints
Other hints may be received due to timer expiry, particularly In some Other hints may be received due to timer expiry, particularly In some
cases the expiry of these timers may be a good hint that DNA cases the expiry of these timers may be a good hint that DNA
procedures are necessary. procedures are necessary.
Since DNA is likely to be used when communicating with devices over Since DNA is likely to be used when communicating with devices over
wireless links, suitable resilience to packet loss SHOULD be wireless links, suitable resilience to packet loss SHOULD be
incorporated into the DNA initiation system. Notably, non-reception incorporated into the DNA initiation system. Notably, non-reception
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Where a host considers it may be on a new link and learns this from a Where a host considers it may be on a new link and learns this from a
hint generated by a multicast message, the host SHOULD defer 0-1000ms hint generated by a multicast message, the host SHOULD defer 0-1000ms
in accordance with [1][3]. Please note though that a single in accordance with [1][3]. Please note though that a single
desynchronization is required for any number of transmissions desynchronization is required for any number of transmissions
subsequent to a hint, regardless of which messages need to be sent. subsequent to a hint, regardless of which messages need to be sent.
In link-layers where sufficient serialization occurs after an event In link-layers where sufficient serialization occurs after an event
experienced by multiple hosts, each host MAY avoid the random delays experienced by multiple hosts, each host MAY avoid the random delays
before sending solicitations specified in [1]. before sending solicitations specified in [1].
5.6 Hint Validity and Hysteresis 5.6 Hint Management for Inactive Hosts
In some cases, hints can be generated by lower-layer protocols at an
elevated rate, which do not reflect actual changes in IP
configuration. In other cases, hints may also be received prior to
the availability of the medium for network-layer packets.
Additionally, since packet reception at the network and other layers
are a source for hints, it is possible for traffic patterns on the
link to create hints, through chance or malicious intent. Therefore,
it may be necessary to classify hint sources and types for their
relevance and recent behavior.
When experiencing a large number of hints, a host SHOULD employ
hysteresis techniques to prevent excessive use of network resources.
The host MAY change the weight of particular hints, to devalue them
if their accuracy has been poor, they suggest invalid configurations,
or are suspicious (refer to Section 8).
It is notable, that such hysteresis may cause sub-optimal change
detection performance, and may themselves be used to block legitimate
hint reception.
5.7 Hint Management for Inactive Hosts
If a host does not expect to send or receive packets soon, it MAY If a host does not expect to send or receive packets soon, it MAY
choose to defer detection of network attachment. This may preserve choose to defer detection of network attachment. This may preserve
resources on latent hosts, by removing any need for packet resources on latent hosts, by removing any need for packet
transmission when a hint is received. transmission when a hint is received.
These hosts SHOULD delay 0-1000ms before sending a solicitation, and These hosts SHOULD delay 0-1000ms before sending a solicitation, and
MAY choose to wait up to twice the advertised Router Advertisement MAY choose to wait up to twice the advertised Router Advertisement
Interval (plus the random delay) before sending a solicitation [5]. Interval (plus the random delay) before sending a solicitation [5].
skipping to change at page 15, line 29 skipping to change at page 14, line 39
tests, the number of devices actively probing for data simultaneously tests, the number of devices actively probing for data simultaneously
is reduced to those hosts which currently support active data is reduced to those hosts which currently support active data
sessions. sessions.
When a device begins sending packets, it will be necessary to test When a device begins sending packets, it will be necessary to test
bidirectional reachability with the router (whose current Neighbor bidirectional reachability with the router (whose current Neighbor
Cache state is STALE). As described in [1], the host will delay Cache state is STALE). As described in [1], the host will delay
before probing to allow for the probability that upper layer packet before probing to allow for the probability that upper layer packet
reception confirms reachability. reception confirms reachability.
6. IP Hosts Configuration 6. Complications to Detecting Network Attachment
Various protocols within IPv6 provide their own configuration
processes. A host will have collected various configuration
information using these protocols during its presence on a link.
Following is the list of steps the host needs to take if a link-
change has occured.
Invalidation of router and prefix list
Invalidation of IPv6 addresses
Removing neighbor cache entries
Completion of DAD for Link-Local Addresses.
Initiating mobility signaling
The following sub-sections elaborate on these steps.
6.1 Router and Prefix list
Router Discovery is designed to provide hosts with a set of locally
configurable prefixes and default routers. These may then be
configured by hosts for access to the Internet [1].
It allows hosts to discover routers and manage lists of eligible next
hop gateways, and is based on IPv6 Neighbor Discovery. When one of
the routers in the router list is determined to be no longer
reachable, its destination cache entry is removed, and new router is
selected from the list. If a currently configured router is
unreachable, it is quite likely that other devices on the same link
are no longer reachable.
On determining that link-change has occurred, the default router list
SHOULD have entries removed which are related to unreachable routers,
and consequently these routers' destination cache entries SHOULD be
removed [1]. If no eligible default routers are in the default
router list, Router Solicitations MAY be sent, in order to discover
new routers.
6.2 IPv6 Addresses
6.2.1 Autoconfiguration
Unicast source addresses are required to send all packets on the
Internet, except a restricted subset of local signaling such as
router and neighbor solicitations.
In dynamic environments, hosts need to undertake automatic
configuration of addresses, and select which addresses to use based
on prefix information advertised in Router Advertisements. Such
configurations may be based on either Stateless Address
Autoconfiguration [3] or DHCPv6 [13].
For any configured address, Duplicate Address Detection (DAD) MUST be
performed [3]. DAD defines that an address is treated tentatively
until either series of timeouts expire after probe transmissions or
an address owner defends its address. Tentative addresses cannot
modify peers' neighbor cache entries, nor can they receive packets.
As described in Section 4.2, messages used in DNA signaling should be
treated as unconfirmed, due to the chance of link change. Optimistic
DAD is designed to allow use of addressing while they are being
checked for validity. Careful use of these addresses may contribute
to faster DNA operation [8].
6.2.2 Dynamic Host Configuration
Dynamic Host Configuration Procedures for IPv6 define their own
detection procedures [13]. In order to check if the current set of
configuration is valid, a host can send a 'Confirm' message with a
sample of its current configuration, which is able to be responded to
by any DHCP relay on a link.
If the replying relay knows it is not on the same link, it may
respond, indicating that the host's configuration is invalid.
Current use of this technique is hampered by the lack of wide scale
deployment of DHCPv6 and hence the detection mechanism doesn't work
when the host moves to a link which doesn't contain DHCP relays or
servers.
Upon link change, any configuration learned from DHCP which is link
or administrative domain specific may have become invalid.
Subsequent operation of DHCP on the new link may therefore be
necessary.
6.3 Neighbor cache
Neighbor caches allow for delivery of packets to peers on the same
link. Neighbor cache entries are created by router or neighbor
discovery signaling, and may be updated either by upper-layer
reachability confirmations or explicit neighbor discovery exchanges.
In order to determine which link-layer address a peer is at, nodes
send solicitations to the link-local solicited-node multicast address
of their peer. If hosts are reachable on this address, then they
will respond to the solicitation with a unicast response.
Information from these responses are stored in neighbour cache
entries.
When link change occurs, the reachability of all existing neighbor
cache entries is likely to be invalidated, if link change prevents
packet reception from an old link. For these links, the neighbor
cache entries SHOULD be removed when a host moves to a new link
(although it MAY be possible to keep keying and authorization
information for such hosts cached on a least-recently-used basis
[7]).
Reachability of a single node may support the likelihood of reaching
the rest of the link, for example if a particular access technology
relays such messages through wireless base stations.
6.4 Mobility Management
Mobile IPv6 provides global mobility signaling for hosts wishing to
preserve sessions when their configured address becomes topologically
incorrect [5]. This system relies upon signaling messages and tunnel
movement to provide reachability at a constant address, while
directing packets to its visited network.
The Mobile IPv6 RFC3775 [5] defines 'movement detection' procedures,
which themselves rely upon Neighbor Discovery, to initiate mobility
signaling. These procedures allow for some modification of Neighbor
Discovery to enable faster change or movement detection. When a host
identifies that it is on a new link, if it is Mobile-IPv6 enabled
host, it MAY initiate mobility signaling with its home agent and
correspondent node.
7. Complications to Detecting Network Attachment
Detection of network attachment procedures can be delayed or may be Detection of network attachment procedures can be delayed or may be
incorrect due to different factors. This section gives some examples incorrect due to different factors. This section gives some examples
where complications may interfere with DNA processing. where complications may interfere with DNA processing.
7.1 Packet Loss 6.1 Packet Loss
Generally, packet loss introduces significant delays in validation of Generally, packet loss introduces significant delays in validation of
current configuration or discovery of new configuration. Because current configuration or discovery of new configuration. Because
most of the protocols rely on timeout to consider that a peer is not most of the protocols rely on timeout to consider that a peer is not
reachable anymore, packet loss may lead to erroneous conclusions. reachable anymore, packet loss may lead to erroneous conclusions.
Additionally, packet loss rates for particular transmission modes Additionally, packet loss rates for particular transmission modes
(multicast or unicast) may differ, meaning that particular classes of (multicast or unicast) may differ, meaning that particular classes of
DNA tests have higher chance of failure due to loss. Hosts SHOULD DNA tests have higher chance of failure due to loss. Hosts SHOULD
attempt to verify tests through retransmission where packet loss is attempt to verify tests through retransmission where packet loss is
prevalent. prevalent.
7.2 Router Configurations 6.2 Router Configurations
Each router can have its own configuration with respect to sending Each router can have its own configuration with respect to sending
RA, and the treatment of router and neighbor solicitations. RA, and the treatment of router and neighbor solicitations.
Different timers and constants might be used by different routers, Different timers and constants might be used by different routers,
such as the delay between Router Advertisements or delay before such as the delay between Router Advertisements or delay before
replying to an RS. If a host is changing its IPv6 link, the new replying to an RS. If a host is changing its IPv6 link, the new
router on that link may have a different configuration and may router on that link may have a different configuration and may
introduce more delay than the previous default router of the host. introduce more delay than the previous default router of the host.
The time needed to discover the new link can then be longer than The time needed to discover the new link can then be longer than
expected by the host. expected by the host.
7.3 Overlapping Coverage 6.3 Overlapping Coverage
If a host can be attached to different links at the same time with If a host can be attached to different links at the same time with
the same interface, the host will probably listen to different the same interface, the host will probably listen to different
routers, at least one on each link. To be simultaneously attached to routers, at least one on each link. To be simultaneously attached to
several links may be very valuable for a MN when it moves from one several links may be very valuable for a MN when it moves from one
access network to another. If the node can still be reachable access network to another. If the node can still be reachable
through its old link while configuring the interface for its new through its old link while configuring the interface for its new
link, packet loss can be minimized. link, packet loss can be minimized.
Such a situation may happen in a wireless environment if the link Such a situation may happen in a wireless environment if the link
layer technology allows the MN to be simultaneously attached to layer technology allows the MN to be simultaneously attached to
several points of attachment and if the coverage area of access several points of attachment and if the coverage area of access
points are overlapping. points are overlapping.
For the purposes of DNA, it is necessary to treat each of these For the purposes of DNA, it is necessary to treat each of these
points-of-attachment separately, otherwise incorrect conclusions of points-of-attachment separately, otherwise incorrect conclusions of
link-change may be made even if another of the link-layer connections link-change may be made even if another of the link-layer connections
is valid. is valid.
7.4 Multicast Snooping 6.4 Multicast Snooping
When a host is participating in DNA on a link where multicast When a host is participating in DNA on a link where multicast
snooping is in use, multicast packets may not be delivered to the snooping is in use, multicast packets may not be delivered to the
LAN-segment to which the host is attached until MLD signaling has LAN-segment to which the host is attached until MLD signaling has
been performed [9][11] [17]. Where DNA relies upon multicast packet been performed [9][11] [17]. Where DNA relies upon multicast packet
delivery (for example, if a router needs to send a Neighbor delivery (for example, if a router needs to send a Neighbor
Solicitation to the host), its function will be degraded until after Solicitation to the host), its function will be degraded until after
an MLD report is sent. an MLD report is sent.
Where it is possible that multicast snooping is in operation, hosts Where it is possible that multicast snooping is in operation, hosts
MUST send MLD group joins (MLD reports) for solicited nodes' MUST send MLD group joins (MLD reports) for solicited nodes'
addresses swiftly after starting DNA procedures. addresses swiftly after starting DNA procedures.
7.5 Link Partition 6.5 Link Partition
Link partitioning occurs when a link's internal switching or relaying Link partitioning occurs when a link's internal switching or relaying
hardware fails, or if the internal communications within a link are hardware fails, or if the internal communications within a link are
prevented due to topology changes or wireless propagation. prevented due to topology changes or wireless propagation.
When a host is on a link which partitions, only a subset of the When a host is on a link which partitions, only a subset of the
addresses or devices it is communicating with may still be available. addresses or devices it is communicating with may still be available.
Where link partitioning is rare (for example, with wired Where link partitioning is rare (for example, with wired
communication between routers on the link), existing router and communication between routers on the link), existing router and
neighbor discovery procedures may be sufficient for detecting change. neighbor discovery procedures may be sufficient for detecting change.
8. Security Considerations 7. Security Considerations
Detecting Network Attachment is a mechanism which allows network Detecting Network Attachment is a mechanism which allows network
messages to change the node's belief about its IPv6 configuration messages to change the node's belief about its IPv6 configuration
state. As such, it is important that the need for rapid testing of state. As such, it is important that the need for rapid testing of
link change does not lead to situations where configuration is link change does not lead to situations where configuration is
invalidated by malicious third parties, nor that information passed invalidated by malicious third parties, nor that information passed
to configuration processes exposes the host to other attacks. to configuration processes exposes the host to other attacks.
Since DNA relies heavily upon IPv6 Neighbor Discovery,the threats Since DNA relies heavily upon IPv6 Neighbor Discovery,the threats
which are applicable to those procedures also affect Detecting which are applicable to those procedures also affect Detecting
Network Attachment. These threats are described in [12]. Network Attachment. These threats are described in [12].
Some additional threats are outlined below. Some additional threats are outlined below.
8.1 Authorization and Detecting Network Attachment 7.1 Authorization and Detecting Network Attachment
Hosts connecting to the Internet over wireless media may be exposed Hosts connecting to the Internet over wireless media may be exposed
to a variety of network configurations with differing robustness, to a variety of network configurations with differing robustness,
controls and security. controls and security.
When a host is determining if link change has occurred, it may When a host is determining if link change has occurred, it may
receive messages from devices with no advertised security mechanisms receive messages from devices with no advertised security mechanisms
purporting to be routers, nodes sending signed router advertisements purporting to be routers, nodes sending signed router advertisements
but with unknown delegation, or routers whose credentials need to be but with unknown delegation, or routers whose credentials need to be
checked [12]. Where a host wishes to configure an unsecured router, checked [12]. Where a host wishes to configure an unsecured router,
skipping to change at page 20, line 33 skipping to change at page 17, line 8
MUST mark the device as unsecured as described in [7]. MUST mark the device as unsecured as described in [7].
In any case, a secured router SHOULD be preferred over an unsecured In any case, a secured router SHOULD be preferred over an unsecured
one, except where other factors (unreachability) make the router one, except where other factors (unreachability) make the router
unsuitable. Since secured routers' advertisement services may be unsuitable. Since secured routers' advertisement services may be
subject to attack, alternative (secured) reachability mechanisms from subject to attack, alternative (secured) reachability mechanisms from
upper layers, or secured reachability of other devices known to be on upper layers, or secured reachability of other devices known to be on
the same link may be used to check reachability in the first the same link may be used to check reachability in the first
instance. instance.
8.2 Addressing 7.2 Addressing
While a DNA host is checking for link-change, and observing DAD, it While a DNA host is checking for link-change, and observing DAD, it
may receive a DAD defense NA from an unsecured source. may receive a DAD defense NA from an unsecured source.
SEND says that DAD defenses MAY be accepted even from non SEND nodes SEND says that DAD defenses MAY be accepted even from non SEND nodes
for the first configured address [7]. for the first configured address [7].
While this is a valid action in the case where a host collides with While this is a valid action in the case where a host collides with
another address owner after arrival on a new link, In the case that another address owner after arrival on a new link, In the case that
the host returns immediately to the same link, such a DAD defense NA the host returns immediately to the same link, such a DAD defense NA
message can only be a denial-of-service attempt. message can only be a denial-of-service attempt.
If a non-SEND node forges a DAD defense for an address which is still 8. Constants
in peers' neighbor cache entries, a host may send a SEND protected
unicast neighbor solicitation without a source link-layer address
option to one of its peers (which also uses SEND). If this peer is
reachable, it will not have registered the non-SEND DAD defense NA in
its neighbor cache, and will send a direct NA back to the soliciting
host. Such an NA reception disproves the DAD defense NA's validity.
Therefore, a SEND host performing DNA which receives a DAD defense
from a non-SEND node SHOULD send a unicast Neighbor Solicitation to a
STALE or REACHABLE secure neighbor cache entry, omitting source link-
layer address options. In this case, the host should pick an entry
which is likely to have a corresponding entry on the peer. If the
host responds within a RetransTimer interval, then the DAD defense
was an attack, and the host SHOULD inform its systems administrator
without disabling the address.
9. Constants
MAC_CACHE_TIME: 30 minutes MAC_CACHE_TIME: 30 minutes
10. Acknowledgments 9. Acknowledgments
Thanks to JinHyeock Choi and Erik Nordmark for their significant Thanks to JinHyeock Choi and Erik Nordmark for their significant
contributions. Bernard Aboba's work on DNA for IPv4 strongly contributions. Bernard Aboba's work on DNA for IPv4 strongly
influenced this document. influenced this document.
11. References 10. References
11.1 Normative References 10.1 Normative References
[1] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery [1] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998. for IP Version 6 (IPv6)", RFC 2461, December 1998.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[3] Thomson, S. and T. Narten, "IPv6 Stateless Address [3] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998. Autoconfiguration", RFC 2462, December 1998.
skipping to change at page 22, line 5 skipping to change at page 18, line 13
(ICMPv6) for the Internet Protocol Version 6 (IPv6) (ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification", RFC2463 2463, December 1998. Specification", RFC2463 2463, December 1998.
[7] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure [7] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005. Neighbor Discovery (SEND)", RFC 3971, March 2005.
[8] Moore, N., "Optimistic Duplicate Address Detection for IPv6", [8] Moore, N., "Optimistic Duplicate Address Detection for IPv6",
draft-ietf-ipv6-optimistic-dad-02 (work in progress), draft-ietf-ipv6-optimistic-dad-02 (work in progress),
September 2004. September 2004.
11.2 Informative References 10.2 Informative References
[9] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener [9] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener
Discovery (MLD) for IPv6", RFC 2710, October 1999. Discovery (MLD) for IPv6", RFC 2710, October 1999.
[10] Haberman, B., "Source Address Selection for the Multicast [10] Haberman, B., "Source Address Selection for the Multicast
Listener Discovery (MLD) Protocol", RFC 3590, September 2003. Listener Discovery (MLD) Protocol", RFC 3590, September 2003.
[11] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 [11] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2
(MLDv2) for IPv6", RFC 3810, June 2004. (MLDv2) for IPv6", RFC 3810, June 2004.
skipping to change at page 24, line 15 skipping to change at page 21, line 5
LSIIT - Univerity Louis Pasteur LSIIT - Univerity Louis Pasteur
Pole API, bureau C444 Pole API, bureau C444
Boulevard Sebastien Brant Boulevard Sebastien Brant
Illkirch 67400 Illkirch 67400
FRANCE FRANCE
Phone: (33) 3 90 24 45 87 Phone: (33) 3 90 24 45 87
Email: montavont@dpt-info.u-strasbg.fr Email: montavont@dpt-info.u-strasbg.fr
URI: http://www-r2.u-strasbg.fr/~montavont/ URI: http://www-r2.u-strasbg.fr/~montavont/
Appendix A. Example State Transition Diagram
Below is an example state diagram which indicates relationships
between the practices in this document.
+---------+ +----------+
| Test |< - - - - -| Init |===>
|Reachable|<-\ | Config |\
+---------+ +----------+ \
| \ New ^ \
| ID | \
V \ | |
+---------+ +----------+ |
| *Idle | \--| Link ID | |
| |<==========| Check | |
+---------+Same ID +----------+ |
^ |Hint Creds^ |
Timer| |Recv OK | |
| | | |
| | | |
| V | |
+----------+ Hint +----------+ |
|Hysteresis| Recv | Authorize| |
| |<--\ | Check | |
+----------+ \-/ +----------+ |
| ^ | |
|Threshold RA | |Bad /
| Recv| |Auth /
V | V /
+----------+ Solicit +----------+L
| Init |=========>|Await |
| DNA |<=========|Rtr Advert|
+----------+ Timer +----------+
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 Rights or other rights that might be claimed to Intellectual Property Rights 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; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
 End of changes. 52 change blocks. 
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