draft-ietf-6man-enhanced-dad-02.txt   draft-ietf-6man-enhanced-dad-03.txt 
Network Working Group R. Asati Network Working Group R. Asati
Internet-Draft H. Singh Internet-Draft H. Singh
Updates: 4862 (if approved) W. Beebee Updates: 4862, 4861 (if approved) W. Beebee
Intended status: Standards Track Cisco Systems, Inc. Intended status: Standards Track Cisco Systems, Inc.
Expires: August 9, 2013 E. Dart Expires: November 25, 2013 E. Dart
Lawrence Berkeley National Lawrence Berkeley National Laboratory
Laboratory
W. George W. George
Time Warner Cable Time Warner Cable
C. Pignataro C. Pignataro
Cisco Systems, Inc. Cisco Systems, Inc.
February 5, 2013 May 24, 2013
Enhanced Duplicate Address Detection Enhanced Duplicate Address Detection
draft-ietf-6man-enhanced-dad-02 draft-ietf-6man-enhanced-dad-03
Abstract Abstract
Appendix A of the IPv6 Duplicate Address Detection (DAD) document in Appendix A of the IPv6 Duplicate Address Detection (DAD) document in
RFC 4862 discusses Loopback Suppression and DAD. However, RFC 4862 RFC 4862 discusses Loopback Suppression and DAD. However, RFC 4862
does not settle on one specific automated means to detect loopback of does not settle on one specific automated means to detect loopback of
Neighbor Discovery (ND of RFC 4861) messages used by DAD. Several Neighbor Discovery (ND of RFC 4861) messages used by DAD. Several
service provider communities have expressed a need for automated service provider communities have expressed a need for automated
detection of looped backed ND messages used by DAD. This document detection of looped backed ND messages used by DAD. This document
includes mitigation techniques and then outlines the Enhanced DAD includes mitigation techniques and then outlines the Enhanced DAD
algorithm to automate detection of looped back IPv6 ND messages used algorithm to automate detection of looped back IPv6 ND messages used
by DAD. For network loopback tests, the Enhanced DAD algorithm by DAD. For network loopback tests, the Enhanced DAD algorithm
allows IPv6 to self-heal after a loopback is placed and removed. allows IPv6 to self-heal after a loopback is placed and removed.
Further, for certain access networks the document automates resolving Further, for certain access networks the document automates resolving
a specific duplicate address conflict. a specific duplicate address conflict.
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 9, 2013. This Internet-Draft will expire on November 25, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Operational Mitigation Options . . . . . . . . . . . . . . . . 4 3. Operational Mitigation Options . . . . . . . . . . . . . . . 4
3.1. Disable DAD on Interface . . . . . . . . . . . . . . . . . 5 3.1. Disable DAD on Interface . . . . . . . . . . . . . . . . 4
3.2. Dynamic Disable/Enable of DAD Using Layer 2 Protocol . . . 5 3.2. Dynamic Disable/Enable of DAD Using Layer 2 Protocol . . 5
3.3. Operational Considerations . . . . . . . . . . . . . . . . 6 3.3. Operational Considerations . . . . . . . . . . . . . . . 5
4. The Enhanced DAD Algorithm . . . . . . . . . . . . . . . . . . 6 4. The Enhanced DAD Algorithm . . . . . . . . . . . . . . . . . 6
4.1. General Rules . . . . . . . . . . . . . . . . . . . . . . 7 4.1. General Rules . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Processing Rules for Senders . . . . . . . . . . . . . . . 7 4.2. Processing Rules for Senders . . . . . . . . . . . . . . 7
4.3. Processing Rules for Receivers . . . . . . . . . . . . . . 8 4.3. Processing Rules for Receivers . . . . . . . . . . . . . 7
4.4. Impact on SEND . . . . . . . . . . . . . . . . . . . . . . 8 4.4. Impact on SEND . . . . . . . . . . . . . . . . . . . . . 8
4.5. Changes to RFC 4862 . . . . . . . . . . . . . . . . . . . 8 4.5. Changes to RFC 4862 . . . . . . . . . . . . . . . . . . . 8
5. Actions to Perform on Detecting a Genuine Duplicate . . . . . 9 4.6. Changes to RFC 4861 . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5. Actions to Perform on Detecting a Genuine Duplicate . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Normative References . . . . . . . . . . . . . . . . . . . . . 10 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
Appendix A. Changes from the -01 version . . . . . . . . . . . . 10 9. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Terminology 1. Terminology
o DAD-failed state - Duplication Address Detection failure as o DAD-failed state - Duplication Address Detection failure as
specified in [RFC4862]. Failure also includes if the Target specified in [RFC4862]. Failure also includes if the Target
Address is optimistic. Optimistic DAD is specified in [RFC4429]. Address is optimistic. Optimistic DAD is specified in [RFC4429].
o Looped back message - also referred to as a reflected message. o Looped back message - also referred to as a reflected message.
The message sent by the sender is received by the sender due to The message sent by the sender is received by the sender due to
the network or a Upper Layer Protocol on the sender looping the the network or a Upper Layer Protocol on the sender looping the
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circuit to which the router's interface is connected) is looped circuit to which the router's interface is connected) is looped
back or connected to itself. Loopback causes packets sent by the back or connected to itself. Loopback causes packets sent by the
interface to be received by the interface, and results in interface to be received by the interface, and results in
interface unavailability for regular data traffic forwarding. See interface unavailability for regular data traffic forwarding. See
more details in section 9.1 of [RFC1247]. The Loopback function more details in section 9.1 of [RFC1247]. The Loopback function
is commonly used in an interface context to gain information on is commonly used in an interface context to gain information on
the quality of the interface, by employing mechanisms such as the quality of the interface, by employing mechanisms such as
ICMPv6 pings, bit-error tests, etc. In a circuit context, it is ICMPv6 pings, bit-error tests, etc. In a circuit context, it is
used in wide area environments including optical dense wave used in wide area environments including optical dense wave
division multiplexing (DWDM) and SONET/SDH for fault isolation division multiplexing (DWDM) and SONET/SDH for fault isolation
(e.g. by placing a loopback at different geographic locations (e.g. by placing a loopback at different geographic locations
along the path of a wide area circuit to help locate a circuit along the path of a wide area circuit to help locate a circuit
fault). The Loopback function may be employed locally or fault). The Loopback function may be employed locally or
remotely. remotely.
o NS(DAD) - shorthand notation to denote an NS with unspecified IPv6 o NS(DAD) - shorthand notation to denote an Neighbor Solicitation
source-address issued during DAD. (NS) with unspecified IPv6 source-address issued during DAD.
2. Introduction 2. Introduction
Appendix A of [RFC4862] discusses Loopback Suppression and Duplicate Appendix A of [RFC4862] discusses Loopback Suppression and Duplicate
Address Detection (DAD). However, [RFC4862] does not settle on one Address Detection (DAD). However, [RFC4862] does not settle on one
specific automated means to detect loopback of ND messages used by specific automated means to detect loopback of ND messages used by
DAD. One specific DAD message is a Neighbor Solicitation (NS), DAD. One specific DAD message is a Neighbor Solicitation (NS),
specified in [RFC4861]. The NS is issued by the network interface of specified in [RFC4861]. The NS is issued by the network interface of
an IPv6 node for DAD. Another message involved in DAD is a Neighbor an IPv6 node for DAD. Another message involved in DAD is a Neighbor
Advertisement (NA). The Enhanced DAD algorithm proposed in this Advertisement (NA). The Enhanced DAD algorithm proposed in this
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interfaces that may be in loopback for long periods of time (such interfaces that may be in loopback for long periods of time (such
as while awaiting turn-up or during long-duration intrusive bit as while awaiting turn-up or during long-duration intrusive bit
error rate tests). error rate tests).
3.3. Operational Considerations 3.3. Operational Considerations
The mitigation options discussed in the document do not require the The mitigation options discussed in the document do not require the
devices on both ends of the circuit to support the mitigation devices on both ends of the circuit to support the mitigation
functionality simultaneously, and do not propose any capability functionality simultaneously, and do not propose any capability
negotiation. The mitigation options discussed in this document are negotiation. The mitigation options discussed in this document are
effective for unidirectional circuit or interface loopback (i.e. the effective for unidirectional circuit or interface loopback (i.e. the
the loopback is placed in one direction on the circuit, rendering the the loopback is placed in one direction on the circuit, rendering the
other direction non-operational). other direction non-operational).
The mitigation options may not be effective for the bidirectional The mitigation options may not be effective for the bidirectional
loopback (i.e. the loopback is placed in both directions of the loopback (i.e. the loopback is placed in both directions of the
circuit interface, so as to identify the faulty segment) if only one circuit interface, so as to identify the faulty segment) if only one
device followed a mitigation option specified in this document, since device followed a mitigation option specified in this document, since
the other device would follow current behavior and disable IPv6 on the other device would follow current behavior and disable IPv6 on
that interface due to DAD until manual intervention restores it. that interface due to DAD until manual intervention restores it.
This is nothing different from what happens today (without the This is nothing different from what happens today (without the
solutions proposed by this document) in case of unidirectional solutions proposed by this document) in case of unidirectional
loopback. Hence, it is expected that an operator would resort to loopback. Hence, it is expected that an operator would resort to
manual intervention for the devices not compliant with this document, manual intervention for the devices not compliant with this document,
as usual. as usual.
skipping to change at page 6, line 40 skipping to change at page 6, line 23
The Enhanced DAD algorithm covers detection of a looped back NS(DAD) The Enhanced DAD algorithm covers detection of a looped back NS(DAD)
message. The document proposes use of the Nonce Option specified in message. The document proposes use of the Nonce Option specified in
the SEND document of [RFC3971]. The nonce is a random number as the SEND document of [RFC3971]. The nonce is a random number as
specified in [RFC3971]. If SEND is enabled on the router and the specified in [RFC3971]. If SEND is enabled on the router and the
router also supports the Enhanced DAD algorithm (specified in this router also supports the Enhanced DAD algorithm (specified in this
document), there is integration with the Enhanced DAD algorithm and document), there is integration with the Enhanced DAD algorithm and
SEND. See more details in the Impact on SEND section. Since a nonce SEND. See more details in the Impact on SEND section. Since a nonce
is used only once, DAD for each IPv6 address of an interface uses a is used only once, DAD for each IPv6 address of an interface uses a
different nonce. different nonce.
When the IPv6 network interface issues a NS(DAD) message, the The interface follows [RFC4862] behavior by issuing
interface includes the Nonce Option in the NS(DAD) message and saves DupAddrDetectTransmits (see [RFC4862]) probes spaced RetransTimer
the nonce in local store. Subsequently if the interface receives an (see [RFC4861]) apart. When the IPv6 network interface issues a
identical NS(DAD) message, the interface logs a system management NS(DAD) message, the interface includes the Nonce Option in the
message, updates any statistics counter, and drops the looped back NS(DAD) message and saves the nonce in local store. Subsequently if
NS(DAD). Additionally the interface continues to issue subsequent the interface receives an identical NS(DAD) message, the interface
probes until a termination condition (to be defined) is detected. logs a system management message, updates any statistics counter,
The DupAddrDetectTransmits value is ignored by the algorithm on drops the looped back NS(DAD), and moves the Target Address to
detection of a looped back NS(DAD). Note [RFC4861] already assigned state. If any probe is looped back within RetransTimer
randomizes issuing the first probe and issues up to three probes; milliseconds after having sent DupAddrDetectTransmits NS(DAD)
note [I-D.ietf-6man-impatient-nud] has intentions to change probe messages, the interface continues with another MAX_MULTICAST_SOLICIT
behavior of [RFC4861]. Additionally, certain networks take a few number of NS(DAD) messages spaced RetransTimer apart. If no probe is
minutes to loop back a packet to a sender. Hence a variable is looped back within RetransTimer milliseconds after
needed to help the interface decide how long to wait for the DAD MAX_MULTICAST_SOLICIT NS(DAD) messages are sent, the probing stops
process to complete. For example, [RFC4862] waits for two seconds to else a new MAX_MULTICAST_SOLICIT number of NS(DAD) messages sequence
see if any message is received to signal a DAD failure, and if not, is initiated. The MAX_MULTICAST_SOLICIT number of NS(DAD) messages
DAD is completed. This document defines a new variable in sequence continues until the stop condition is reached. The
WAIT_TIME_LOOPBACK. For example, WAIT_TIME_LOOPBACK is two seconds RetransTimer may be overidden by a link-specific document if a node
for [RFC4862] behavior and five minutes for another network. The supports the Enhanced DAD algorithm. Note
interface also uses an exponentially backoff algorithm (pick one of [I-D.ietf-6man-impatient-nud] has intentions to change probe behavior
several available) to issue probes. of [RFC4861]. The RetransTimer value may be overridden by a link-
type specific document.
If the interface receives a NS(DAD) message with a different nonce If the interface receives a NS(DAD) message with a different nonce
but TargetAddress matches a tentative or optimistic address on the but the Target Address matches a tentative or optimistic address on
interface, the interface logs a DAD-failed system management message, the interface, the interface logs a DAD-failed system management
updates any statistics, and behaves identical to the behavior message, updates any statistics, and behaves identical to the
specified in [RFC4862] for DAD failure. behavior specified in [RFC4862] for DAD failure.
Six bytes of random nonce is sufficiently large for nonce collisions. Six bytes of random nonce is sufficiently large for nonce collisions.
However if there is a collision because two nodes generated the same However if there is a collision because two nodes generated the same
random nonce (that are using the same Target address in their random nonce (that are using the same Target Address in their
NS(DAD)), then the algorithm will incorrectly detect a looped back NS(DAD)), then the algorithm will incorrectly detect a looped back
NS(DAD) when the NS(DAD) was issued to signal a genuine duplicate. NS(DAD) when the NS(DAD) was issued to signal a genuine duplicate.
Since each looped back NS(DAD) event is logged to system management, Since each looped back NS(DAD) event is logged to system management,
the administrator of the network will have to intervene manually. the administrator of the network will have to intervene manually.
The algorithm is capable of detecting any ND solicitation (NS and The algorithm is capable of detecting any ND solicitation (NS and
Router Solicitation) or advertisement (NA and Router Advertisement) Router Solicitation) or advertisement (NA and Router Advertisement)
that is looped back. However, saving a nonce and nonce related data that is looped back. However, saving a nonce and nonce related data
for all ND messages has impact on memory of the node and also adds for all ND messages has impact on memory of the node and also adds
the algorithm state to a substantially larger number of ND messages. the algorithm state to a substantially larger number of ND messages.
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If an IPv6 node implements the Enhanced DAD algorithm, the node MUST If an IPv6 node implements the Enhanced DAD algorithm, the node MUST
implement detection of looped back NS(DAD) messages during DAD for an implement detection of looped back NS(DAD) messages during DAD for an
interface address. interface address.
4.2. Processing Rules for Senders 4.2. Processing Rules for Senders
If a node has been configured to use the Enhanced DAD algorithm, when If a node has been configured to use the Enhanced DAD algorithm, when
sending a NS(DAD) for a tentative or optimistic interface address the sending a NS(DAD) for a tentative or optimistic interface address the
sender MUST generate a random nonce associated with the interface sender MUST generate a random nonce associated with the interface
address, MUST save the nonce, and MUST include the nonce in the Nonce address, MUST save the nonce, and MUST include the nonce in the Nonce
Option included in the NS(DAD). If a looped back NS(DAD) is detected Option included in the NS(DAD). If any probe is looped back within
by the interface, the interface ignores the DupAddrDetectTransmits RetransTimer milliseconds after having sent DupAddrDetectTransmits
and issues subsequent probes forever in an exponential backoff NS(DAD) messages, the interface continues with another
transmission until a termination condition is detected. MAX_MULTICAST_SOLICIT number of NS(DAD) messages spaced RetransTimer
apart. If no probe is looped back within RetransTimer milliseconds
after MAX_MULTICAST_SOLICIT NS(DAD) messages are sent, the probing
stops else a new MAX_MULTICAST_SOLICIT number of NS(DAD) messages
sequence is initiated. The MAX_MULTICAST_SOLICIT number of NS(DAD)
messages sequence continues until the stop condition is reached.
4.3. Processing Rules for Receivers 4.3. Processing Rules for Receivers
If the node has been configured to use the Enhanced DAD algorithm and If the node has been configured to use the Enhanced DAD algorithm and
an interface on the node receives any NS(DAD) message where the an interface on the node receives any NS(DAD) message where the
target address matches the interface address (in tentative or Target Address matches the interface address (in tentative or
optimistic state), the receiver compares the nonce, if any, is optimistic state), the receiver compares the nonce, if any, is
included in the message with any saved nonce on the receiving included in the message with any saved nonce on the receiving
interface. If a match is found, the node SHOULD log a system interface. If a match is found, the node SHOULD log a system
management message, SHOULD update any statistics counter, and MUST management message, SHOULD update any statistics counter, MUST drop
drop the received message. If the received NS(DAD) message includes the received message, and move the Target Address to assigned state.
a nonce and no match is found with any saved nonce, the node SHOULD
log a system management message for DAD-failed and SHOULD update any If the received NS(DAD) message includes a nonce and no match is
statistics counter. TODO: Define termination condition. found with any saved nonce, the node SHOULD log a system management
message for DAD-failed and SHOULD update any statistics counter.
4.4. Impact on SEND 4.4. Impact on SEND
The SEND document uses the Nonce Option in the context of matching an The SEND document uses the Nonce Option in the context of matching an
NA with an NS. However, no text in SEND has an explicit mention of NA with an NS. However, no text in SEND has an explicit mention of
detecting looped back ND messages. If this document updates detecting looped back ND messages. If this document updates
[RFC4862], SEND should be updated to integrate with the Enhanced DAD [RFC4862], SEND should be updated to integrate with the Enhanced DAD
algorithm. A minor update to SEND would be to explicitly mention algorithm. A minor update to SEND would be to explicitly mention
that the nonce in SEND is also used by SEND to detect looped back NS that the nonce in SEND is also used by SEND to detect looped back NS
messages during DAD operations by the node. In a mixed SEND messages during DAD operations by the node. In a mixed SEND
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address and if the DAD probe is reflected back to the interface, the address and if the DAD probe is reflected back to the interface, the
interface is stuck in DAD failed state and IPv6 services to the 100 interface is stuck in DAD failed state and IPv6 services to the 100
thousand clients is denied. Disabling DAD for such an IPv6 interface thousand clients is denied. Disabling DAD for such an IPv6 interface
on an access concentrator is not an option because the network also on an access concentrator is not an option because the network also
needs to detect genuine duplicates in the interface downstream needs to detect genuine duplicates in the interface downstream
network. The Enhanced DAD algorithm also facilitates detecting a network. The Enhanced DAD algorithm also facilitates detecting a
genuine duplicate for the interface on the access concentrator. See genuine duplicate for the interface on the access concentrator. See
the Actions to Perform on Detecting a Genuine Duplicate section of the Actions to Perform on Detecting a Genuine Duplicate section of
the Enhanced DAD document. the Enhanced DAD document.
4.6. Changes to RFC 4861
1. The RetransTimer may be overridden by a link-specific document if
a node supports the Enhanced DAD algorithm.
2. If a node has been configured to use the Enhanced DAD algorithm,
an NS with an unspecified source address adds the Nonce option to
the message and implements the state machine of the Enhanced DAD
algorithm.
5. Actions to Perform on Detecting a Genuine Duplicate 5. Actions to Perform on Detecting a Genuine Duplicate
As described in paragraphs above the nonce can also serve to detect As described in paragraphs above the nonce can also serve to detect
genuine duplicates even when the network has potential for looping genuine duplicates even when the network has potential for looping
back ND messages. When a genuine duplicate is detected, the node back ND messages. When a genuine duplicate is detected, the node
follows the manual intervention specified in section 5.4.5 of follows the manual intervention specified in section 5.4.5 of
[RFC4862]. However, in certain networks such as an access network if [RFC4862]. However, in certain networks such as an access network if
the genuine duplicate matches the tentative or optimistic IPv6 the genuine duplicate matches the tentative or optimistic IPv6
address of a network interface of the access concentrator, automated address of a network interface of the access concentrator, automated
actions are proposed. actions are proposed.
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security issue before a remote node on the link can issue reflected security issue before a remote node on the link can issue reflected
NS(DAD) messages. Again, SEND is recommended for this exploit. NS(DAD) messages. Again, SEND is recommended for this exploit.
7. IANA Considerations 7. IANA Considerations
None. None.
8. Acknowledgements 8. Acknowledgements
Thanks (in alphabetical order by first name) to Dmitry Anipko, Eric Thanks (in alphabetical order by first name) to Dmitry Anipko, Eric
Levy-Abegnoli, Erik Nordmark, Fred Templin, Michael Sinatra, Ray Levy-Abegnoli, Erik Nordmark, Fred Templin, Michael Sinatra, Ole
Hunter, Suresh Krishnan, and Tassos Chatzithomaoglou for their Troan, Ray Hunter, Suresh Krishnan, and Tassos Chatzithomaoglou for
guidance and review of the document. Thanks to Thomas Narten for their guidance and review of the document. Thanks to Thomas Narten
encouraging this work. Thanks to Steinar Haug and Scott Beuker for for encouraging this work. Thanks to Steinar Haug and Scott Beuker
describing the use cases. for describing the use cases.
9. Normative References 9. Normative References
[I-D.ietf-6man-impatient-nud] [I-D.ietf-6man-impatient-nud]
Nordmark, E. and I. Gashinsky, "Neighbor Unreachability Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection is too impatient", Detection is too impatient", draft-ietf-6man-impatient-
draft-ietf-6man-impatient-nud-05 (work in progress), nud-06 (work in progress), April 2013.
October 2012.
[RFC1247] Moy, J., "OSPF Version 2", RFC 1247, July 1991. [RFC1247] Moy, J., "OSPF Version 2", RFC 1247, July 1991.
[RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
RFC 1661, July 1994. RFC 1661, July 1994.
[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.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
skipping to change at page 10, line 39 skipping to change at page 10, line 35
[RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD)
for IPv6", RFC 4429, April 2006. for IPv6", RFC 4429, April 2006.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007. September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007. Address Autoconfiguration", RFC 4862, September 2007.
Appendix A. Changes from the -01 version
1. Changed the algorithm in section 4 and other sections to not
suppress subsequent probes and instead probe forever subject to a
termination condition.
2. Minor edits were made for more clarified text.
Authors' Addresses Authors' Addresses
Rajiv Asati Rajiv Asati
Cisco Systems, Inc. Cisco Systems, Inc.
7025 Kit Creek road 7025 Kit Creek road
Research Triangle Park, NC 27709-4987 Research Triangle Park, NC 27709-4987
USA USA
Email: rajiva@cisco.com Email: rajiva@cisco.com
URI: http://www.cisco.com/ URI: http://www.cisco.com/
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