wdiff draft-thubert-6lo-rfc6775-update-reqs-05.txt draft-thubert-6lo-rfc6775-update-reqs-06.txt

6Lo P. Thubert, Ed.
Internet-Draft cisco
Intended status: Standards Track October 27, 2014 P. van der Stok
Expires: April 28, July 18, 2015 consultant
January 14, 2015

Requirements for an update to 6LoWPAN ND
draft-thubert-6lo-rfc6775-update-reqs-05
draft-thubert-6lo-rfc6775-update-reqs-06

Abstract

Work presented at the ROLL, 6lo, 6TiSCH and 6MAN Working Groups
suggest that enhancements to the 6LoWPAN ND mechanism are now needed.
This document elaborates on those requirements and suggests
approaches to serve them.

Status of this This Memo

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5 6
4.1. Requirements Related to Mobility . . . . . . . . . . . . . 5 6
4.2. Requirements Related to Routing Protocols . . . . . . . . 6 7
4.3. Requirements Related to the Variety of Low-Power Link
types 6
4.4. Requirements Related to Proxy Operations . . . . . . . . . 7
4.5. Requirements Related to Security . . . . . . . . . . . . . 7
4.6. . . . . 8
4.4. Requirements Related to Low-Power devices Proxy Operations . . . . . . . . 8
4.7.
4.5. Requirements Related to Security . . . . . . . . . . . . 9
4.6. Requirements Related to Scalability . . . . . . . . . . . 8 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 9 11
8.2. Informative References . . . . . . . . . . . . . . . . . . 10 12
Appendix A. Suggested Changes to Protocol Elements . . . . . . . . 12
Appendix 14
A.1. ND Neighbor Solicitation (NS) . . . . . . . . . . 12
Appendix . . . . 14
A.2. ND Router Advertisement (RA) . . . . . . . . . . 12
Appendix . . . . 15
A.3. RPL DODAG Information Object (DIO) . . . . . . . 13
Appendix . . . . 15
A.4. ND Enhanced Address Registration Option (EARO) . 13
Author's Address . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14 . . 17

1. Introduction

A number of use cases, including the Industrial Internet, require a
large scale deployment of sensors that can not be realized with wires
and is only feasible over wireless Low power and Lossy Network (LLN)
technologies. When simpler hub-and-spoke topologies are not
sufficient for the expected throughput and density, mesh networks
must be are
deployed, which implies the concepts routing of hosts and routers,
whether packets over the mesh,
operated at either Layer-2 or Layer-3.

The

For routing over a mesh at layer-3, the IETF has designed the LLN host-to-router and router-to-router
protocol that supports address assignment and the router-to-router
protocol that supports reachability across Route-Over LLNs in
different Areas. It was clear for both efforts that the scalability
requirements could only be met with IPv6 [RFC2460], and there is no
fundamental contradiction between those protocols to that regard.

While
Routing Protocol over LLN (RPL) [RFC6550].

To assign routable addresses, DHCPv6 is still a viable option in LLNs,
LLNs. However, the new IETF standard that supports address assignment
specifically for LLNs is 6LoWPAN ND, the Neighbor Discovery
Optimization for Low-power and Lossy Networks [RFC6775]. 6LoWPAN ND
was designed as a stand-alone mechanism separately from its IETF
routing counterpart, the IPv6 Routing Protocol for Low power and
Lossy Networks [RFC6550] (RPL), and the interaction between the 2
protocols was not defined.

The 6TiSCH WG is now considering an architecture [I-D.ietf-6tisch-
architecture]
[I-D.ietf-6tisch-architecture] whereby a 6LowPAN ND host could
connect to the Internet via a RPL Network, but this requires
additions to the 6LOWPAN ND protocol to support mobility and
reachability in a secured and manageable environment.

At the same time, new work at 6MAN on Efficiency aware IPv6 Neighbor
Discovery Optimizations [I-D.chakrabarti-nordmark-6man-efficient-nd]
suggests that 6LoWPAN ND can be extended to other types of networks
on top of the Low power and Lossy Networks (LLNs) for which it was
already defined. The value of such extension is especially apparent
in the case of mobile wireless devices, to reduce the multicast
operations that are related to classical ND ([RFC4861], [RFC4862])
and plague the wireless medium. In this context also, there is a
need for additions to the protocol. 6LOWPAN ND.

The Optimistic Duplicate Address Detection [RFC4429] (ODAD)
specification details how an address can be used before a Duplicate
Address Detection (DAD) is complete, and insists that an address that
is TENTATIVE should not be associated to a Source Link-Layer Address
Option in a Neighbor Solicitation message. As we expect the 6LoWPAN
ND protocol for a more general use, it can make sense Applying this rule to keep
respecting that rule, which is
6LOWPAN ND implies another change to the its specification.

In [I-D.richardson-6tisch--security-6top], the 6tisch working group
considers the use of layer-2 security. It develops a network
bootstrap protocol that provides secure link connections at the same
rate that nodes are discovered. This approach needs the presence of
a routing protocol to route packets from a joining node to a security
providing node (e.g. a PCE or commissioning tool).

This document suggests a limited evolution to [RFC6775] so as to
allow operation of a 6LoWPAN ND node as a leaf in while a RPL network. routing protocol (in
first instance RPL) is present and operational. It also suggests a
more generalized use of the information in the ARO option outside of the ND
messages outside the strict LLN domain, for instance over a converged
backbone.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

Readers are expected to be familiar with all the terms and concepts
that are discussed in "Neighbor Discovery for IP version 6"
[RFC4861], "IPv6 Stateless Address Autoconfiguration" [RFC4862],
"IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals" [RFC4919],
Neighbor Discovery Optimization for Low-power and Lossy Networks
[RFC6775] and "Transmission of IPv6 Packets over IEEE 802.15.4
Networks" [RFC4944].

Additionally, this document uses terminology from 6TiSCH [I-D.ietf-
6tisch-terminology]
[I-D.ietf-6tisch-terminology] and ROLL [RFC7102].

3. Overview

This document is mostly motivated by the work ongoing in the 6TiSCH
working group. The 6TiSCH architecture
[I-D.ietf-6tisch-architecture] expects that
a 6LoWPAN device can connect as a leaf to a RPL network, where the
leaf support is draft explains the minimal functionality to connect as a host to a
RPL network without the need to participate to the full routing
protocol. The support
architecture of leaf can be implemented as a minor
increment to 6LoWPAN ND, with the additional capability to carry a
sequence number that 6TiSCH network. This architecture is used to track for the movements
remainder of the device,
and optionally some information about the RPL topology that this
device will join. document.

The scope of the 6TiSCH Architecture is a Backbone Link that
federates multiple LLNs (mesh) as a single IPv6 Multi-Link Subnet.
Each LLN in the subnet is anchored at a Backbone Router (6BBR). The
Backbone Routers interconnect the LLNs over the Backbone Link and
emulate that the LLN nodes are present on the Backbone by proxy-ND operations. thus creating
a so-called: Multi-Link Subnet. An LLN node can move freely from an
LLN Route-Over mesh anchored at a Backbone Router to another LLN anchored at a the same
or a different Backbone Router inside the Multi-Link Subnet and
conserve its addresses.

Figure 1: 6TiSCH architecture

The root of 6LBR is the RPL topology border router that is placed between the LLN and
nodes outside the LLN. The 6LBR is logically separated from the 6BBR
that is used to connect the RPL topology LLN to the backbone. The RPL
root 6LBR can use
Efficient ND as the interface to register an LLN node in its topology
to the 6BBR for whatever operation the 6BBR performs, such as ND
proxy operations, or injection in a routing protocol. It results
that, as illustrated in Figure 2, the periodic signaling could start
at the leaf node with 6LoWPAN ND, then would be carried
over RPL routed to the RPL root, 6LBR,
and then with Efficient-ND to the 6BBR. Efficient ND being an
adaptation of 6LoWPAN ND, it makes sense to keep those two
homogeneous in the way they use the source and the target addresses
in the Neighbor Solicitation (NS) messages for registration, as well
as in the options that they use for that process.

6LoWPAN Node host 6LR 6LBR 6BBR
(RPL leaf) (router) (root)

| | | |
| 6LoWPAN ND |6LoWPAN ND+RPL | 6LoWPAN ND | Efficient ND | IPv6 ND
| LLN link |Route-Over mesh| | IPv6 route | IPv6 link | Backbone
| | | |
| NS(ARO) | | |
|-------------->| | |
| 6LoWPAN ND | DAR (then DAO)| |
| |-------------->| |
| | | NS(ARO) |
| | |-------------->|
| | | | DAD
| | | |------>
| | | |
| | | NA(ARO) |
| | |<--------------|
| | DAC | |
| |<--------------| |
| NA(ARO) | | |
|<--------------| | |

Figure 2: (Re-)Registration Flow over Multi-Link Subnet

As the network builds up, a node should start LoWPAN host starts as a leaf to join the
RPL network,
LLN, and may later turn into both a RPL-capable router and a 6LR, so as to accept leaf other nodes to
recursively join the network. LLN.

Section 5 of the 6TiSCH architecture [I-D.ietf-6tisch-architecture]
provides more information on the need to update the protocols that
sustain the requirements in the next section.

4. Requirements

4.1. Requirements Related to Mobility

Due to the unstable nature of LLN networks, links, even in a LLN of immobile
nodes a fixed 6LoWPAN Node may change its point of attachment (a 6LR) to a 6LR, say
6LR-a, and may not be able to notify
the 6LR that it has disconnected from. It results that the previous
6LR 6LR-a. Consequently, 6LR-a may
still attract traffic that it cannot deliver any more. When
the links to
a 6LR changes, change state, there is thus a need to identify stale states in
a 6LR and restore reachability timely. in a timely fashion.

Req1.1: Upon a change of point of attachment, connectivity via a new
6LR MUST be restored timely without the need to de-register from the
previous 6LR.

Req1.2: For that purpose, the protocol MUST enable to differentiate
between multiple registrations from a same one 6LoWPAN Node and
registrations from two different 6LoWPAN Nodes claiming a the same address.

Req1.3: This information Stale states MUST be passed from the 6LR to the 6LBR, and
the 6LBR SHOULD be able to clean cleaned up the stale state asynchronously in
the previous 6LR. 6LRs.

Req1.4: A 6LoWPAN Node SHOULD also be capable to register a same its Address
to multiple 6LRs, and this, concurrently.

4.2. Requirements Related to Routing Protocols

The point of attachment of a 6LoWPAN Node may be a 6LR in an LLN
mesh. An IPv6 routing in a LLN route-over mesh is typically can be based on RPL, which is the
routing protocol that was defined at the IETF for this particular
purpose. It derives that in this scenario, Other routing protocols than RPL are also considered by
Standard Defining Organizations (SDO) on the 6LR would classically
support RPL. One goal basis of the expected
network characteristics. It is required that a 6LoWPAN Node attached
via ND to a
RPL-capable 6LR would not need to participate to in the RPL selected routing
protocol to obtain reachability via the 6LR. An additional goal would be

Next to
obtain reachability via the 6LBR unicast address registered by ND, other addresses
including multicast addresses are needed as well. For example a
routing protocols through protocol often uses a same ND-
based abstraction. multicast address to register changes
to established paths. ND needs to register such a multicast address
to enable routing concurrently with discovery.

Multicast is needed for groups. Groups MAY be formed by device type
(e.g. routers, street lamps), location (Geography, RPL sub-tree), or
both.

The Bit Index Explicit Replication (BIER) Architecture
[I-D.wijnands-bier-architecture] proposes an optimized technique to
enable multicast in a LLN with a very limited requirement for routing
state in the nodes.

Related requirements are:

Req2.1: The ND registration method SHOULD be extended in such a
fashion that the 6LR MAY advertise the Address of a 6LoWPAN Node over
RPL
the selected routing protocol and obtain reachability to that Address over
using the RPL domain. selected routing protocol.

Req2.2: The Considering RPL, the Address Registration Option that is used
in the ND registration SHOULD be extended to carry enough information
to generate a DAO message as specified in [RFC6550] section 6.4, in
particular the capability to compute a DAOSequence and, as an option,
a RPLInstanceID.

Req2.3: Depending on their applicability to LLNs, other standard mesh
/MANET protocols MAY be considered as well.

Req2.4: Multicast operations SHOULD be supported and optimized.
Groups MAY be formed by device type (e.g. routers, street lamps),
location (Geography, RPL sub-tree), optimized, for
instance using BIER or both. RPL already has the
capability to advertise multicast groups; whether MPL. Whether ND is appropriate for the
registration to the 6BBR is to be defined, considering the additional
burden of supporting the Multicast Listener Discovery Version 2
[RFC3810] (MLDv2) for IPv6.

4.3. Requirements Related to the Variety of Low-Power Link types

6LoWPAN ND [RFC6775] was defined with a focus on IEEE802.15.4 and in
particular the capability to derive a unique Identifier from a
globally unique MAC-64 address. At this point, the 6lo Working Group
is extending the 6LoWPAN Header Compression (HC) [RFC6282] technique
to other link types ITU-T G.9959 [I-D.brandt-6man-lowpanz], Master-
Slave/Token-Passing [I-D.ietf-6lo-6lobac], DECT Ultra Low Energy [I-D
.ietf-6lo-dect-ule],
[I-D.ietf-6lo-dect-ule], Near Field Communication [I-D.hong-6lo-ipv6
-over-nfc],
[I-D.hong-6lo-ipv6-over-nfc], as well as IEEE1901.2 Narrowband
Powerline Communication Networks
[I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks] and BLUETOOTH(R)
Low Energy [I-D.ietf-6lo-btle].

Related requirements are:

Req3.1: The support of the registration mechanism SHOULD be extended
to more LLN links, links than IEEE 802.15.4, matching at least the LLN links that are considered by
6lo
for which an "IPv6 over foo" specification exists, as well as other popular Low-Power links such as Low-Power Low-
Power Wi-Fi.

Req3.2: As part of this extension, a mechanism to compute a unique
Identifier should be provided, with the capability to form a Link-
Local Address that can not be a duplicate. The Identifier SHOULD be unique at least to within the domain where an Address formed LLN connected
to a 6LBR discovered by this device
may be advertised through ND mechanisms. in each node within the LLN.

Req3.3: The Address Registration Option used in the ND registration
SHOULD be extended to carry the relevant forms of unique Identifier.

Req3.4: The Neighbour Discovery should specify the formation of a
site-local address that follows the security recommendations from
[RFC7217].

4.4. Requirements Related to Proxy Operations

Sleeping

Duty-cycled devices may not be able to answer themselves to a lookup
from a node that uses classical ND on a backbone and may need a proxy
operation by a 6BBR.
proxy. Additionally, the duty-cycled device may need to rely on the
6LBR to perform that registration to the 6BBR.

The ND registration method SHOULD defend the addresses of duty-cycled
devices that are sleeping most of the time and not capable to defend
their own Addresses.

Related requirements are:

Req4.1: The registration mechanism SHOULD enable a third party to
proxy register an Address on behalf of a 6LoWPAN node that may be
sleeping or located deeper in an LLN mesh.

Req4.2: The registration mechanism SHOULD be applicable to a duty-
cycled device regardless of the link type, and enable a 6BBR to
operate as a proxy to defend the registered Addresses on its behalf.

Req4.3: The registration mechanism SHOULD enable long sleep
durations, in the order of multiple days to a month.

4.5. Requirements Related to Security

In order to guarantee the operations of the 6LoWPAN ND flows, the
spoofing of the 6LR, 6LBR and 6BBRs roles should be avoided. Once a
node successfully registers an address, 6LoWPAN ND should provide
energy-efficient means for the 6LBR to protect that ownership even if
when the node that registered the address is sleeping.

In particular, the 6LR and the 6LBR then should be able to verify
whether a subsequent registration for a same given Address comes from the
original node.

In a same node LLN it makes sense to base security on layer-2 security. During
bootstrap of the LLN, nodes join the network after authorization by a
Joining Assistant (JA) or is a duplicate. Commissioning Tool (CT). After joining
nodes communicate with each other via secured links. The keys for
the layer-2 security are distributed by the JA/CT. The JA/CT can be
part of the LLN or be outside the LLN. In both cases it is needed
that packets are routed between JA/CT and the joining node.

Related requirements are:

Req5.1: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for
the 6LR, 6LBR and 6BBR to authenticate and authorize one another for
their respective roles, as well as with the 6LoWPAN Node for the role
of 6LR.

Req5.2: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for
the 6LR and the 6LBR to validate whether a new registration
corresponds to a same 6LoWPAN Node, and, if not, determine the
rightful owner, and deny or clean-up the registration that is deemed
in excess. of authorized
nodes. Joining of unauthorized nodes MUST be impossible.

Req5.3: 6LoWPAN ND security mechanisms SHOULD lead to small packet
sizes. In particular, the NS, NA, DAR and DAC messages for a re-
registration flow SHOULD NOT exceed 80 octets so as to fit in a
secured IEEE802.15.4 frame.

Req5.4: Recurrent 6LoWPAN ND security operations MUST NOT be
computationally intensive on the LoWPAN Node CPU. When a Key hash
calculation is employed, a mechanism lighter than SHA-1 SHOULD be
preferred.

Req5.5: The number of Keys that the 6LoWPAN Node needs to manipulate
SHOULD be minimized.

Req5.6: The 6LoWPAN ND security mechanisms SHOULD enable CCM* for use
at both Layer 2 and Layer 3, and SHOULD enable the reuse of security
code that has to be present on the device for upper layer security
such as TLS.

Req5.7: Public key and signature sizes SHOULD be minimized while
maintaining adequate confidentiality and data origin authentication
for multiple types of applications with various degrees of
criticality.

4.6. Requirements Related to Low-Power devices

The ND registration method is designed to save energy on Low-Power
devices, and in particular enable duty-cycled devices that are
sleeping most

Req5.8: Routing of packets should continue when links pass from the time and not capable
unsecured to defend their own
Addresses against always-on devices.

Related requirements are:

Req6.1: The registration mechanism the secured state.

Req5.9: 6LoWPAN ND security mechanisms SHOULD be applicable to provide a Low-
Power device regardless of mechanism for
the link type, 6LR and enable a 6BBR to
operate as a proxy to defend the registered Addresses on its behalf.

Req6.2: The registration mechanism SHOULD enable long sleep
durations, in the order of multiple days 6LBR to validate whether a month, new registration for devices
capable of operating over a
given address corresponds to the course of ten or more years without same 6LoWPAN Node that registered it
initially, and, if not, determine the
need to recharge rightful owner, and deny or replace
clean-up the batteries.

4.7. registration that is duplicate.

4.6. Requirements Related to Scalability

Use cases from Automatic Meter Reading (AMR, collection tree
operations) and Advanced Metering Infrastructure (AMI, bi-directional
communication to the meters) indicate the needs for a large number of
LLN nodes pertaining to a single RPL DODAG (e.g. 5000) and connected
to the 6LBR over a large number of LLN hops (e.g. 15).

Related requirements are:

Req7.1:

Req6.1: The registration mechanism SHOULD enable a single 6LBR to
register multiple thousands of devices.

Req7.2:

Req6.2: The timing of the registration operation should allow for a
large latency such as found in LLNs with ten and more hops.

5. Security Considerations

This specification expects that the link layer is sufficiently
protected, either by means of physical or IP security for the Backbone Link or
MAC sublayer cryptography. In particular, it is expected that the
LLN MAC provides secure unicast to/from the Backbone Router and
secure broadcast from the Backbone Router in a way that prevents tempering
tampering with or replaying the RA messages. Still, Section 4.5 has
a requirement for a mutual authentication and authorization for a
role for 6LRs, 6LBRs and 6BBRs.

This documents also suggests in Appendix Appendix A.4 that a 6LoWPAN Node
could form a single Unique Interface ID (CUID) based on cryptographic
techniques similar to CGA. The CUID would be used as Unique
Interface Identifier in the ARO option and new Secure ND procedures
would be proposed to use it as opposed to the source IPv6 address to
secure the binding between an Address and its owning Node, and
enforce First/Come-First/Serve at the 6LBR.

6. IANA Considerations

This draft does not require an IANA action.

7. Acknowledgments

The author wishes acknowledge the contributions by Samita
Chakrabarti, Erik Normark, JP Vasseur, Eric Levy-Abegnoli, Patrick
Wetterwald, Thomas Watteyne, and Behcet Sarikaya.

8. References

8.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2460] Deering, S.E. S. and R.M. R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.

[RFC3775] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.

[RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.

[RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD)
for IPv6", RFC 4429, April 2006.

[RFC4443] Conta, A., Deering, S. S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.

[RFC4861] Narten, T., Nordmark, E., Simpson, W. W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.

[RFC4862] Thomson, S., Narten, T. T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.

[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J. J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, September 2007.

[RFC6275] Perkins, C., Johnson, D. D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.

[RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
September 2011.

[RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
Levis, P., Pister, K., Struik, R., Vasseur, JP. JP., and R.
Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
Lossy Networks", RFC 6550, March 2012.

[RFC6655] McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for
Transport Layer Security (TLS)", RFC 6655, July 2012.

[RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E. E., and C. Bormann,
"Neighbor Discovery Optimization for IPv6 over Low-Power
Wireless Personal Area Networks (6LoWPANs)", RFC 6775,
November 2012.

[RFC6830] Farinacci, D., Fuller, V., Meyer, D. and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830, January
2013.

8.2. Informative References

[I-D.brandt-6man-lowpanz]
Brandt, A. and J. Buron, "Transmission of IPv6 packets
over ITU-T G.9959 Networks", Internet-Draft draft-brandt-
6man-lowpanz-02, draft-brandt-6man-lowpanz-02
(work in progress), June 2013.

[I-D.chakrabarti-nordmark-6man-efficient-nd]
Chakrabarti, S., Nordmark, E., Thubert, P. P., and M.
Wasserman, "Wired and Wireless IPv6 "IPv6 Neighbor Discovery
Optimizations", Internet-Draft Optimizations for
Wired and Wireless Networks", draft-chakrabarti-nordmark-
6man-efficient-nd-04, October 2013.
6man-efficient-nd-06 (work in progress), July 2014.

[I-D.hong-6lo-ipv6-over-nfc]
Hong, Y., Choi, Y., Youn, J., Kim, D. Y. and J. Choi, Youn, "Transmission of IPv6 Packets over
Near Field Communication", Internet-Draft draft-hong-6lo-ipv6-over-
nfc-01, August draft-hong-6lo-ipv6-over-nfc-03
(work in progress), November 2014.

[I-D.ietf-6lo-6lobac]
Lynn, K., Martocci, J., Neilson, C. C., and S. Donaldson,
"Transmission of IPv6 over MS/TP Networks", Internet-Draft
draft-ietf-6lo-6lobac-00, draft-ietf-
6lo-6lobac-00 (work in progress), July 2014.

[I-D.ietf-6lo-btle]
Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
Shelby, Z. Z., and C. Gomez, "Transmission of IPv6 Packets
over BLUETOOTH(R) Low Energy", Internet-Draft draft-ietf-
6lo-btle-02, June 2014. draft-ietf-6lo-btle-06
(work in progress), January 2015.

[I-D.ietf-6lo-dect-ule]
Mariager, P., Petersen, J., Shelby, Z., Logt, M. M., and D.
Barthel, "Transmission of IPv6 Packets over DECT Ultra Low
Energy", Internet-Draft draft-ietf-6lo-dect-ule-00, draft-ietf-6lo-dect-ule-00 (work in progress),
June 2014.

[I-D.ietf-6tisch-architecture]
Thubert, P., Watteyne, T. T., and R. Assimiti, "An
Architecture for IPv6 over the TSCH mode of IEEE
802.15.4e", Internet-Draft draft-ietf-6tisch-
architecture-01, February draft-ietf-6tisch-architecture-04 (work in
progress), October 2014.

[I-D.ietf-6tisch-terminology]
Palattella, M., Thubert, P., Watteyne, T. T., and Q. Wang,
"Terminology in IPv6 over the TSCH mode of IEEE
802.15.4e", Internet-Draft draft-ietf-6tisch-
terminology-00, November 2013. draft-ietf-6tisch-terminology-03 (work in
progress), January 2015.

[I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks]
Popa, D. and J. Hui, "6LoPLC: Transmission of IPv6 Packets
over IEEE 1901.2 Narrowband Powerline Communication
Networks", Internet-Draft draft-popa-6lo-6loplc-ipv6-over-
ieee19012-networks-00,
ieee19012-networks-00 (work in progress), March 2014.

[I-D.richardson-6tisch--security-6top]
Richardson, M., "6tisch secure join using 6top", draft-
richardson-6tisch--security-6top-04 (work in progress),
November 2014.

[I-D.wijnands-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-wijnands-bier-architecture-02 (work in
progress), December 2014.

[RFC3610] Whiting, D., Housley, R. R., and N. Ferguson, "Counter with
CBC-MAC (CCM)", RFC 3610, September 2003.

[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A. A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.

[RFC3971] Arkko, J., Kempf, J., Zill, B. B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.

[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.

[RFC4389] Thaler, D., Talwar, M. M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, April 2006.

[RFC4919] Kushalnagar, N., Montenegro, G. G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals", RFC
4919, August 2007.

[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830, January
2013.

[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, January 2014.

[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217, April 2014.

Appendix A. Suggested Changes to Protocol Elements

Appendix

A.1. ND Neighbor Solicitation (NS)

The NS message used for registration should use a source address that
respects the rules in [RFC6775], [RFC4861], and [RFC4429] for DAD.
The SLLA Option may be present but only if the address passed DAD,
and it is used to allow the 6LR to respond as opposed to as a
registration mechanism.

The address that is being registered is the target address in the NS
message and the TLLA Option must be present.

Appendix

A.2. ND Router Advertisement (RA)

[I-D.chakrabarti-nordmark-6man-efficient-nd] adds an 'E' bit in the
Router Advertisement flag, as well as a new Registrar Address Option
(RAO). These fields are probably pertinent to LLNs inclusion into a
revised 6LoWPAN ND should be studied. If the new 6LoWPAN flows
require a change of behaviour (e.g. registering the Target of the NS
message) then the RA must indicate that the router supports the new
capability, and the NS must indicate that the Target is registered as
opposed to the Source in an unequivocal fashion.

There is some amount of duplication between the options in the RPL
DIO [RFC6550] and the options in the ND RA messages. At the same
time, there are a number of options, including the 6LoWPAN Context
Option (6CO) [RFC6775], the MTU and the SLLA Options [RFC4861] that
can only be found in the RA messages. Considering that these options
are useful for a joining node, the recommendation would be to
associate the RA messages to the join beacon, and make them rare when
the network is stable. On the other hand, the DIO message is to be
used as the propagated heartbeat of the RPL network and provide the
sense of time and liveliness.

RAs should also be issued and the information therein propagated when
a change occurs in the information therein, such as a router or a
prefix lifetime.

Appendix

A.3. RPL DODAG Information Object (DIO)

If the RPL root serves as 6LBR, it makes sense to add at least a bit
of information in the DIO to signal so. A Registrar Address Option
(RAO) may also be considered for addition.

Appendix

A.4. ND Enhanced Address Registration Option (EARO)

The ARO option contains a Unique ID that is supposed to identify the
device across multiple registrations. It is envisioned that the
device could form a single CGA-based Unique Interface ID (CUID) to
securely bind all of its addresses. The CUID would be used as Unique
Interface Identifier in the ARO option and to form a Link-Local
address that would be deemed unique regardless of the Link type.
Provided that the relevant cryptographic material is passed to the
6LBR upon the first registration or on-demand at a later time, the
6LBR can validate that a Node is effectively the owner of a CUID, and
ensure that the ownership of an Address stays with the CUID that
registered it first.

This option is designed to be used with standard NS and NA messages
between backbone Routers as well as between nodes and 6LRs over the
LLN and between the 6LBR and the 6BBR over whatever IP link they use
to communicate.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Status | RPLInstanceID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Res|P|N| IDS |T| TID | Registration Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Unique Interface Identifier (variable length) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: EARO

The representation above is based on [I-D.chakrabarti-nordmark-6man-
efficient-nd].
[I-D.chakrabarti-nordmark-6man-efficient-nd]. Only the proposed
changes from that specification are discussed below but the
expectation is that 6LoWPAN ND and Efficient ND converge on the ARO
format.

Status: 8-bit integer. A new value of 3 is suggested to indicate a
rejection due to an obsolete TID, typically an indication of a
movement.

RPLInstanceID: 8-bit integer. This field is set to 0 when unused.
Otherwise it contains the RPLInstanceID for which this address is
registered, as specified in RPL [RFC6550], and discussed in
particular in section 3.1.2.

P: One bit flag. When the bit is set, the address being registered
is Target of the NS as opposed to the Source, for instance to
enable ND proxy operation.

N: One bit flag. Set if the device moved. If not set, the 6BBR will
refrain from sending gratuitous NA(O) or other form of distributed
ND cache clean-up over the backbone. For instance, the flag
should be reset after the DAD operation upon address formation.

Author's Address

Authors' Addresses

Pascal Thubert, editor Thubert (editor)
Cisco Systems, Inc
Building D
45 Allee des Ormes - BP1200
MOUGINS - Sophia Antipolis, Antipolis 06254
FRANCE

Phone: +33 497 23 26 34
Email: pthubert@cisco.com

Peter van der Stok
consultant

Phone: +31-492474673 (Netherlands), +33-966015248 (France)
Email: consultancy@vanderstok.org
URI: www.vanderstok.org