draft-ietf-v6ops-nd-cache-init-01.txt   draft-ietf-v6ops-nd-cache-init-02.txt 
v6ops J. Linkova v6ops J. Linkova
Internet-Draft Google Internet-Draft Google
Intended status: Informational December 10, 2019 Intended status: Informational June 9, 2020
Expires: June 12, 2020 Expires: December 11, 2020
Neighbor Cache Entries on First-Hop Routers: Operational Considerations Neighbor Cache Entries on First-Hop Routers: Operational Considerations
draft-ietf-v6ops-nd-cache-init-01 draft-ietf-v6ops-nd-cache-init-02
Abstract Abstract
Neighbor Discovery (RFC4861) is used by IPv6 nodes to determine the Neighbor Discovery (RFC4861) is used by IPv6 nodes to determine the
link-layer addresses of neighboring nodes as well as to discover and link-layer addresses of neighboring nodes as well as to discover and
maintain reachability information. This document discusses how the maintain reachability information. This document discusses how the
neighbor discovery state machine on a first-hop router is causing neighbor discovery state machine on a first-hop router is causing
user-visible connectivity issues when a new (not being seen on the user-visible connectivity issues when a new (not being seen on the
network before) IPv6 address is being used. network before) IPv6 address is being used.
skipping to change at page 1, line 35 skipping to change at page 1, line 35
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 12, 2020. This Internet-Draft will expire on December 11, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 4 2. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Solution Requirements . . . . . . . . . . . . . . . . . . 4 2.1. Solution Requirements . . . . . . . . . . . . . . . . . . 5
2.2. Solution Overview . . . . . . . . . . . . . . . . . . . . 5 2.2. Solution Overview . . . . . . . . . . . . . . . . . . . . 5
3. Solutions Considered but Discarded . . . . . . . . . . . . . 6 3. Solutions Considered but Discarded . . . . . . . . . . . . . 6
3.1. Do Nothing . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Do Nothing . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Change to the Registration-Based Neighbor Discovery . . . 7 3.2. Change to the Registration-Based Neighbor Discovery . . . 7
3.3. Host Sending NS to the Router Address from Its GUA . . . 7 3.3. Host Sending NS to the Router Address from Its GUA . . . 7
3.4. Host Sending Router Solicitation from its GUA . . . . . . 7 3.4. Host Sending Router Solicitation from its GUA . . . . . . 8
3.5. Routers Populating Their Caches by Gleaning From Neighbor 3.5. Routers Populating Their Caches by Gleaning From Neighbor
Discovery Packets . . . . . . . . . . . . . . . . . . . . 8 Discovery Packets . . . . . . . . . . . . . . . . . . . . 8
3.6. Initiating Hosts2Routers Communication . . . . . . . . . 9 3.6. Initiating Hosts-to-Routers Communication . . . . . . . . 9
3.7. Transit Dataplane Traffic From a New Address Triggering 3.7. Transit Dataplane Traffic From a New Address Triggering
Address Resolution . . . . . . . . . . . . . . . . . . . 9 Address Resolution . . . . . . . . . . . . . . . . . . . 9
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
The section 7.2.5 of [RFC4861] states: "When a valid Neighbor The section 7.2.5 of [RFC4861] states: "When a valid Neighbor
Advertisement is received (either solicited or unsolicited), the Advertisement is received (either solicited or unsolicited), the
Neighbor Cache is searched for the target's entry. If no entry Neighbor Cache is searched for the target's entry. If no entry
exists, the advertisement SHOULD be silently discarded. There is no exists, the advertisement SHOULD be silently discarded. There is no
need to create an entry if none exists, since the recipient has need to create an entry if none exists, since the recipient has
apparently not initiated any communication with the target." apparently not initiated any communication with the target."
This approach is perfectly suitable for host2host communications This approach is perfectly suitable for host-to-host communications,
which are in most cases bi-directional and it could be expected that which are in most cases bi-directional, and it could be expected that
if a host A has an ND cache entry for the host B IPv6 address, the if a host A has an ND cache entry for the host B IPv6 address, host B
host B also has the corresponding ND entry for the host A address in also has the corresponding ND entry for the host A address in its
its cache. However when a host communicates to off-link destinations cache. However when a host communicates to off-link destinations via
via its first-hop router that logic does not apply. The most typical its first-hop router, that logic does not apply. The most typical
scenario when the problem may arise is a host joining the network, scenario when the problem may arise is a host joining the network,
forming a new address and using that address for accessing the forming a new address and using that address for accessing the
Internet: Internet:
1. A host joins the network and receives a Router Advertisement 1. A host joins the network and receives a Router Advertisement (RA(
packet from the first-hop router (either a periodic unsolicited packet from the first-hop router (either a periodic unsolicited
RA or a response to an RS sent by the host). The RA contains RA or a response to a Router Solicitation sent by the host). The
information the host needs to perform SLAAC and to configure its RA contains information the host needs to perform SLAAC and to
network stack. As in most cases the RA also contains the Source configure its network stack. As in most cases the RA also
link-layer address of the router, the host can populate its contains the Source link-layer address of the router, the host
Neighbor Cache with the router link-local and link-layer can populate its Neighbor Cache with the router's link-local and
addresses. link-layer addresses.
2. The host starts opening connections to off-link destinations. 2. The host starts opening connections to off-link destinations. A
Very common use case is a mobile device sending probes to detect very common use case is a mobile device sending probes to detect
the Internet connectivity and/or the captive portals presence on the Internet connectivity and/or the captive portals presence on
the network. To speed up that process many implementations use the network. To speed up that process many implementations use
the Optimistic Duplicate Address Detection [RFC4429] which allows Optimistic Duplicate Address Detection [RFC4429] which allows
them to send probes from their GUA before the DAD process is them to send probes from their GUA before the DAD process is
completed. At that moment the device ND cache contains all completed. At that moment the device ND cache contains all
information required to send those probes (such as the default information required to send those probes (such as the default
gateway LLA and the link-layer address). The router ND cache, gateway LLA and the link-layer address). The router ND cache,
however, might contain an entry for the device link-local address however, might contain an entry for the device link-local address
(if the device has been performing the ND process for the roiter (if the device has been performing the address resolution for the
LLA) but there are no entries for the device GUA. router LLA) but there are no entries for the device GUA.
3. Return traffic is received by the first-hop router. As the 3. Return traffic is received by the first-hop router. As the
router does not have any ND cache entry for the host GUA yet, the router does not have any ND cache entry for the host GUA yet, the
router starts the neighbor discovery process by creating an router starts the neighbor discovery process by creating an
INCOMPLETE cache entry and then sending an NS to the Solicited INCOMPLETE cache entry and then sending an NS to the Solicited
Node Multicast Address. Most router implementations buffer only Node Multicast Address. Most router implementations buffer only
one data packet while performing the neighbor discovery for the one data packet while resolving the packet destination address,
packet destination address, so it would drop all subsequent so it would drop all subsequent packets for the host GUA, until
packets for the host GUA, until the address resolution process is the address resolution process is completed.
completed.
4. If the host sends multiple probes in parallel it would considered 4. If the host sends multiple probes in parallel it would consider
all but one of them failed. It leads to user-visible delay in all but one of them failed. It leads to user-visible delay in
connecting to the network, especially if the host implements some connecting to the network, especially if the host implements some
form of backoff mechanism and does not retransmit the porbes as form of backoff mechanism and does not retransmit the probes as
soon as possible. soon as possible.
This scenario illustrates the problem happening when the device This scenario illustrates the problem happening when the device
connects to the network for the first time or after a timeout long connects to the network for the first time or after a timeout long
enough for the device address to be removed from the router neighbor enough for the device address to be removed from the router's
cache. However the same sequence of events happen when the host neighbor cache. However the same sequence of events happen when the
starts using the new GUA previously unseen by the router, such as a host starts using a new GUA previously unseen by the router, such as
new privacy address [RFC4941] or if the router Neighbor Cache has a new privacy address [RFC4941] or if the router's Neighbor Cache has
been flushed. been flushed.
While in dual-stack networks this problem might hidden by Happy While in dual-stack networks this problem might be hidden by Happy
Eyeballs [RFC8305] it manifest quite clearly in IPv6-only Eyeballs [RFC8305] it manifests quite clearly in IPv6-only
environments, especially wireless ones, leading to poor user environments, especially wireless ones, leading to poor user
experience and contributing to negative perception of IPv6-only experience and contributing to negative perception of IPv6-only
solutions as unstable and non-deployable. solutions as unstable and non-deployable.
This document discusses operational implications of not proactively
creating Neighbor Cache entries on first-hop routers and summarizes
various approaches to mitigate the problem.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
1.2. Terminology 1.2. Terminology
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TLLA: Target link-layer Address, an option in the ND packets TLLA: Target link-layer Address, an option in the ND packets
containing the link-layer address of the target, [RFC4861]. containing the link-layer address of the target, [RFC4861].
GUA: Global Unicast Address, [RFC4291]. GUA: Global Unicast Address, [RFC4291].
DAD: Duplicate Address Detection, [RFC4862]. DAD: Duplicate Address Detection, [RFC4862].
Optimistic DAD: a modification of DAD, [RFC4429]. Optimistic DAD: a modification of DAD, [RFC4429].
2. Proposed Solution 2. Proposed Solution
2.1. Solution Requirements 2.1. Solution Requirements
It would be highly desirable to improve the Neighbor Discovery It would be highly desirable to improve the Neighbor Discovery
mechanics so routers have a usable cache entry for a host address by mechanics so routers have a usable cache entry for a host address by
the time the first packet for that address is received by the router. the time the first packet for that address is received by the router.
In particular, In particular,
o If the router does not have a Neighbor Cache entry for the o If the router does not have a Neighbor Cache entry for the
address, a STALE entry needs to be created. address, a STALE entry needs to be created.
o The solution needs to work for Optimistic addresses as well. o The solution needs to work for Optimistic addresses as well.
Devices implementing the Optimistic DAD usually attempt to Devices implementing the Optimistic DAD usually attempt to
minimize the delay in connecting to the network and therefore are minimize the delay in connecting to the network and therefore are
more likely to be affected by the problem described in this more likely to be affected by the problem described in this
document. document.
o In case of duplicate addresses present in the network the proposed o In case of duplicate addresses present in the network, the
solution MUST NOT override the existing entry. proposed solution MUST NOT override the existing entry.
o In topologies with multiple first hop routers the cache needs to o In topologies with multiple first hop routers the cache needs to
be updated on all of them, as traffic might be asymmetric: be updated on all of them, as traffic might be asymmetric:
outgoing flows leaving the network via one router while the return outgoing flows leaving the network via one router while the return
traffic enters the segment via another one. traffic enters the segment via another one.
2.2. Solution Overview 2.2. Solution Overview
The Neighbor Discovery is designed to allow IPv6 nodes to discover The Neighbor Discovery is designed to allow IPv6 nodes to discover
neighboring nodes reachability and learn IPv6 to link-layer addresses neighboring nodes reachability and learn IPv6 to link-layer addresses
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"A node sends Neighbor Advertisements in response to Neighbor "A node sends Neighbor Advertisements in response to Neighbor
Solicitations and sends unsolicited Neighbor Advertisements in order Solicitations and sends unsolicited Neighbor Advertisements in order
to (unreliably) propagate new information quickly." to (unreliably) propagate new information quickly."
Propagating information about new GUA as quickly as possible is Propagating information about new GUA as quickly as possible is
exactly what is required to solve the problem outlined in this exactly what is required to solve the problem outlined in this
document. Therefore the host might send an unsolicited NA with the document. Therefore the host might send an unsolicited NA with the
target link-layer address option to advertize its GUA as soon as the target link-layer address option to advertize its GUA as soon as the
said address enters Optimistic or Preferred state. said address enters Optimistic or Preferred state.
The proposed solution is discussed in [I-D.linkova-6man-grand]. In The proposed solution is discussed in [I-D.ietf-6man-grand]. In
summary the follwing changes to [RFC4861] are suggested: summary the following changes to [RFC4861] are suggested:
o Hosts SHOULD send at least one unsolicited NA packet to all- o Hosts SHOULD send at least one unsolicited NA packet with the
routers multicast address (ff02::2) as soon as one of the Override flag cleared to all-routers multicast address (ff02::2)
following events happens: as soon as one of the following events happens:
* (if Optimistic DAD is used): a new Optimistic GUA is assigned * (if Optimistic DAD is used): a new Optimistic GUA is assigned
to the host interface. to the host interface.
* (if Optimistic DAD is not used): a GUA changes the state from * (if Optimistic DAD is not used): a GUA changes the state from
tentative to preferred. tentative to preferred.
o Routers SHOULD create a new ND cache entry upon receiving o Routers SHOULD create a new STALE ND cache entry upon receiving
unsolicited NAs. unsolicited NAs.
It should be noted that some routing and switching platforms have It should be noted that some routing and switching platforms have
implemented such behaviour already. Administrators could enable implemented such behaviour already. Administrators could enable
creating neighbor discovery cache entries based on unsolicited NA creating neighbor discovery cache entries based on unsolicited NA
packets sent from the previously unknown neighbors on that interface. packets sent from the previously unknown neighbors on that interface.
Network devices implementing First-Come, First-Served Source Address
Validation (FCFS SAVI, [RFC6620]) might drop Neighbor Advertisements
received through a Validating Port which is in the TENTATIVE state
(see Section 2.3.2 of[RFC6620]). Therefore hosts using Optimistic
DAD might not benefit from the proposed solution if FCFS SAVI is
implemeneted on the network infrastructure. [I-D.ietf-6man-grand]
discusses in more details how the proposed solution interacts with
SAVI.
3. Solutions Considered but Discarded 3. Solutions Considered but Discarded
The problem could be addressed from different angles. Possible The problem could be addressed from different angles. Possible
approaches are: approaches are:
o Just do nothing. o Just do nothing.
o Migrate from the "reactive" Neighbor Discovery ([RFC4861]) to the o Migrate from the "reactive" Neighbor Discovery ([RFC4861]) to the
registration-based mechanisms ([RFC8505]). registration-based mechanisms ([RFC8505]).
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o Many support tickets. o Many support tickets.
o More resistance to deploy IPv6 and IPv6-Only networks. o More resistance to deploy IPv6 and IPv6-Only networks.
3.2. Change to the Registration-Based Neighbor Discovery 3.2. Change to the Registration-Based Neighbor Discovery
The most radical approach would be to move away from the reactive ND The most radical approach would be to move away from the reactive ND
as defined in [RFC4861] and expand the registration-based ND as defined in [RFC4861] and expand the registration-based ND
([RFC6775], [RFC8505]) used in Low-Power Wireless Personal Area ([RFC6775], [RFC8505]) used in Low-Power Wireless Personal Area
Networks (6LoWPANs) to the rest of IPv6 deployments. This option Networks (6LoWPANs) to the rest of IPv6 deployments. This option
required some investigation and discussions and seems to be an requires some investigation and discussions and seems to be an
overkill for the problem described in this document. overkill for the problem described in this document.
3.3. Host Sending NS to the Router Address from Its GUA 3.3. Host Sending NS to the Router Address from Its GUA
The host could force creating a STALE entry for its GUA in the router The host could force creating a STALE entry for its GUA in the router
ND cache by sending the following Neighbor Solicitation message: ND cache by sending the following Neighbor Solicitation message:
o The NS source address is the host GUA. o The NS source address is the host GUA.
o The destination address is the default router IPv6 address.
o The Source Link-Layer Address option contains the host link-layer o The Source Link-Layer Address option contains the host link-layer
address. address.
o The target address is the host default gateway address (the o The target address is the host default gateway address (the
default router address the host received in the RA). default router address the host received in the RA).
The main disadvantages of this approach are: The main disadvantages of this approach are:
o Would not work for Optimistic addresses as section 2.2 of o Would not work for Optimistic addresses as section 2.2 of
[RFC4429] explicitly prohibits sending Neighbor Solicitations from [RFC4429] explicitly prohibits sending Neighbor Solicitations from
an Optimistic Address. an Optimistic Address.
o If first-hop redundancy is deployed in the network, the NS would o If first-hop redundancy is deployed in the network, the NS would
reach the active router only, so all backup routers (or all active reach the active router only, so all backup routers (or all active
routers ex. one) would not get their neighbor cache updated. routers ex. one) would not get their neighbor cache updated.
o Some wireless devices are known to fiddle with ND packets and o Some wireless devices are known to alter ND packets and perform
perform various non-obvious forms of ND proxy actions. In some various non-obvious forms of ND proxy actions. In some cases
cases unsolicited NAs might not even reach the routers. unsolicited NAs might not even reach the routers.
3.4. Host Sending Router Solicitation from its GUA 3.4. Host Sending Router Solicitation from its GUA
The host could send a router solicitation message to 'all routers' The host could send a router solicitation message to 'all routers'
multicast address, using its GUA as a source. If the host link-layer multicast address, using its GUA as a source. If the host link-layer
address is included in the Source Link-Layer Address option, the address is included in the Source Link-Layer Address option, the
router would create a STALE entry for the host GUA as per the section router would create a STALE entry for the host GUA as per the section
6.2.6 of [RFC4861]. However this approach can not be used if the GUA 6.2.6 of [RFC4861]. However this approach can not be used if the GUA
is in optimistic state: the section 2.2 of [RFC4429] explicitly is in optimistic state: the section 2.2 of [RFC4429] explicitly
prohibits using an Optimistic Address as the source address of a prohibits using an Optimistic Address as the source address of a
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The same solution was proposed in The same solution was proposed in
[I-D.halpern-6man-nd-pre-resolve-addr]. Some routing vendors support [I-D.halpern-6man-nd-pre-resolve-addr]. Some routing vendors support
such optimization already. However this approach has a number of such optimization already. However this approach has a number of
drawbacks and therefore should not be used as the only solution: drawbacks and therefore should not be used as the only solution:
o Routers need to receive all multicast Neighbor Discovery packets o Routers need to receive all multicast Neighbor Discovery packets
which might negatively impact the routers CPU. which might negatively impact the routers CPU.
o If the router starts the address resolution as soon as it receives o If the router starts the address resolution as soon as it receives
the DAD Neighbor Solicitation the host might be still performing the DAD Neighbor Solicitation the host might be still performing
the DAD and the target address might be tentative. In that case DAD and the target address might be tentative. In that case the
the host SHOULD silently ignore the received Neighbor Solicitation host SHOULD silently ignore the received Neighbor Solicitation
from the router as per the Section 5.4.3 of [RFC4862]. As a from the router as per the Section 5.4.3 of [RFC4862]. As a
result the router might not be able to complete the address result the router might not be able to complete the address
resolution before the return traffic arrives. resolution before the return traffic arrives.
3.6. Initiating Hosts2Routers Communication 3.6. Initiating Hosts-to-Routers Communication
The host may trigger the router to start the address resolution by The host may force the router to start address resolution by sending
sending a data packet such as ping or traceroute to its default a data packet such as ping or traceroute to its default router link-
router link-local address, using the GUA as a source address. As the local address, using the GUA as a source address. As the RTT to the
RTT to the default gateway is lower than RTT to any off-link default gateway is lower than RTT to any off-link destinations it's
destinations it's quite likely that the router would start the quite likely that the router would start the neighbor discovery
neighbor discovery process for the host GUA before the first packet process for the host GUA before the first packet of the returning
of the returning traffic arrives. traffic arrives.
The downside of this approach includes: The downside of this approach includes:
o Data packets to the router LLA could be blocked by security policy o Data packets to the router LLA could be blocked by security policy
or control plane protection mechanism. or control plane protection mechanism.
o Additional overhead for routers control plane (in addition to o Additional overhead for routers control plane (in addition to
processing ND packets, the data packet needs to be processed as processing ND packets, the data packet needs to be processed as
well). well).
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4. IANA Considerations 4. IANA Considerations
This memo asks the IANA for no new parameters. This memo asks the IANA for no new parameters.
5. Security Considerations 5. Security Considerations
This memo documents the operational issue and does not introduce any This memo documents the operational issue and does not introduce any
new security considerations. Security considerations of the proposed new security considerations. Security considerations of the proposed
solution are discussed in the corresponding section of solution are discussed in the corresponding section of
[I-D.linkova-6man-grand]. [I-D.ietf-6man-grand].
6. Acknowledgements 6. Acknowledgements
Thanks to the following people (in alphabetical order) for their Thanks to the following people (in alphabetical order) for their
review and feedback: Lorenzo Colitti, Igor Gashinsky, Tatuya Jinmei, review and feedback: Mikael Abrahamsson, Lorenzo Colitti, Owen
Erik Kline, Warren Kumari, Michael Richardson, Pascal Thubert, DeLong, Igor Gashinsky, Fernando Gont, Tatuya Jinmei, Erik Kline,
Warren Kumari, Michael Richardson, Dave Thaler, Pascal Thubert,
Loganaden Velvindron, Eric Vyncke. Loganaden Velvindron, Eric Vyncke.
7. References 7. References
7.1. Normative References 7.1. Normative References
[I-D.linkova-6man-grand] [I-D.ietf-6man-grand]
Linkova, J., "Gratuitous Neighbor Discovery: Creating Linkova, J., "Gratuitous Neighbor Discovery: Creating
Neighbor Cache Entries on First-Hop Routers", draft- Neighbor Cache Entries on First-Hop Routers", draft-ietf-
linkova-6man-grand-01 (work in progress), November 2019. 6man-grand-00 (work in progress), March 2020.
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>. 2006, <https://www.rfc-editor.org/info/rfc4291>.
skipping to change at page 10, line 46 skipping to change at page 11, line 19
[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,
DOI 10.17487/RFC4861, September 2007, DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>. <https://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007, DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>. <https://www.rfc-editor.org/info/rfc4862>.
[RFC6620] Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS
SAVI: First-Come, First-Served Source Address Validation
Improvement for Locally Assigned IPv6 Addresses",
RFC 6620, DOI 10.17487/RFC6620, May 2012,
<https://www.rfc-editor.org/info/rfc6620>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)", Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012, RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>. <https://www.rfc-editor.org/info/rfc6775>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
 End of changes. 40 change blocks. 
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