Requirements for an update to 6LoWPAN ND
draft-thubert-6lo-rfc6775-update-reqs-05
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| Document | Type |
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| Author | Pascal Thubert | ||
| Last updated | 2014-10-27 | ||
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draft-thubert-6lo-rfc6775-update-reqs-05
6Lo P. Thubert, Ed.
Internet-Draft cisco
Intended status: Standards Track October 27, 2014
Expires: April 28, 2015
Requirements for an update to 6LoWPAN ND
draft-thubert-6lo-rfc6775-update-reqs-05
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 Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 28, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (http://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5
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4.1. Requirements Related to Mobility . . . . . . . . . . . . . 5
4.2. Requirements Related to Routing Protocols . . . . . . . . 6
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. Requirements Related to Low-Power devices . . . . . . . . 8
4.7. Requirements Related to Scalability . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . . 10
Appendix A. Suggested Changes to Protocol Elements . . . . . . . . 12
Appendix A.1. ND Neighbor Solicitation (NS) . . . . . . . . . . 12
Appendix A.2. ND Router Advertisement (RA) . . . . . . . . . . 12
Appendix A.3. RPL DODAG Information Object (DIO) . . . . . . . 13
Appendix A.4. ND Enhanced Address Registration Option (EARO) . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
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 deployed, which implies the concepts of hosts and routers,
whether operated at Layer-2 or 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 DHCPv6 is still a viable option in LLNs, 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] whereby a 6LowPAN ND host could connect to the Internet
via a RPL Network, but this requires additions to the protocol to
support mobility and reachability in a secured and manageable
environment.
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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.
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 to keep
respecting that rule, which is another change to the specification.
This document suggests a limited evolution to [RFC6775] so as to
allow operation of a 6LoWPAN ND node as a leaf in a RPL network. It
also suggests a more generalized use of the information in the ARO
option outside of 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] and ROLL [RFC7102].
3. Overview
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 the minimal functionality to connect as a host to a
RPL network without the need to participate to the full routing
protocol. The support of leaf can be implemented as a minor
increment to 6LoWPAN ND, with the additional capability to carry a
sequence number that is used to track the movements of the device,
and optionally some information about the RPL topology that this
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device will join.
The scope of the 6TiSCH Architecture is a Backbone Link that
federates multiple LLNs 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. An
LLN node can move freely from an LLN Route-Over mesh anchored at a
Backbone Router to another anchored at a same or a different Backbone
Router inside the Multi-Link Subnet and conserve its addresses.
---+------------------------
| Plant Network
|
+-----+
| | Gateway
| |
+-----+
|
| Backbone Link (with VLANs)
+--------------------+------------------+
| | |
+-----+ +-----+ +-----+
| | Backbone | | Backbone | | Backbone
| | router | | router | | router
+-----+ +-----+ +-----+
| | | | | |
0 0 0 0 0 (6LBR == RPL root)
o o o o o o o o o o o o o o
o o o o o o o o o o (6LR == RPL router)
o o o o o o o z
o o o o o z
RPL Instances (6LoWPAN Host == RPL leaf)
The root of the RPL topology is logically separated from the 6BBR
that is used to connect the RPL topology to the backbone. The RPL
root 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 to the RPL root, 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.
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6LoWPAN Node 6LR 6LBR 6BBR
(RPL leaf) (router) (root)
| | | |
| 6LoWPAN ND |6LoWPAN ND+RPL | Efficient ND | IPv6 ND
| LLN link |Route-Over mesh| IPv6 link | Backbone
| | | |
| NS(ARO) | | |
|-------------->| | |
| 6LoWPAN ND | DAR (then DAO)| |
| |-------------->| |
| | | NS(ARO) |
| | |-------------->|
| | | | DAD
| | | |------>
| | | |
| | | NA(ARO) |
| | |<--------------|
| | DAC | |
| |<--------------| |
| NA(ARO) | | |
|<--------------| | |
As the network builds up, a node should start as a leaf to join the
RPL network, and may later turn into both a RPL-capable router and a
6LR, so as to accept leaf nodes to recursively join the network.
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 nature of LLN networks, even a fixed 6LoWPAN Node may
change its point of attachment (a 6LR) and may not be able to notify
the 6LR that it has disconnected from. It results that the previous
6LR may still attract traffic that it cannot deliver any more. When
the 6LR changes, there is thus a need to identify stale states and
restore reachability timely.
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
multiple registrations from a same 6LoWPAN Node from two different
6LoWPAN Nodes claiming a same address.
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Req1.3: This information MUST be passed from the 6LR to the 6LBR, and
the 6LBR SHOULD be able to clean up the stale state asynchronously in
the previous 6LR.
Req1.4: A 6LoWPAN Node SHOULD also be capable to register a same
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 LLN route-over mesh is typically based on RPL, which is the
routing protocol that was defined at the IETF for this particular
purpose. It derives that in this scenario, the 6LR would classically
support RPL. One goal is that a 6LoWPAN Node attached via ND to a
RPL-capable 6LR would not need to participate to the RPL protocol to
obtain reachability via the 6LR. An additional goal would be to
obtain reachability via other routing protocols through a same ND-
based abstraction.
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 and obtain reachability to that Address over the RPL domain.
Req2.2: 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), or both. RPL already has the
capability to advertise multicast groups; 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
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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], Near Field Communication [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, matching at least the links that are considered by
6lo as well as other popular Low-Power links such as 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 the domain where an Address formed by this device
may be advertised through ND mechanisms.
Req3.3: The Address Registration Option used in the ND registration
SHOULD be extended to carry the relevant forms of unique Identifier.
4.4. Requirements Related to Proxy Operations
Sleeping 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. Additionally, the device may need to rely on the
6LBR to perform that registration to the 6BBR.
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.
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 to protect that ownership even if the node is
sleeping. In particular, the 6LR and the 6LBR then should be able to
verify whether a subsequent registration for a same Address comes
from a same node or is a duplicate.
Related requirements are:
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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.
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 of the time and not capable to defend their own
Addresses against always-on devices.
Related requirements are:
Req6.1: The registration mechanism SHOULD be applicable to a Low-
Power device regardless of the link type, 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 to a month, for devices
capable of operating over the course of ten or more years without the
need to recharge or replace the batteries.
4.7. Requirements Related to Scalability
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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: The registration mechanism SHOULD enable a single 6LBR to
register multiple thousands of devices.
Req7.2: 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 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. and R.M. Hinden, "Internet Protocol, Version
6 (IPv6) Specification", RFC 2460, December 1998.
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[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. 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. and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4862] Thomson, S., Narten, T. and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J. and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, September 2007.
[RFC6275] Perkins, C., Johnson, 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. 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. 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
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[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, June 2013.
[I-D.chakrabarti-nordmark-6man-efficient-nd]
Chakrabarti, S., Nordmark, E., Thubert, P. and M.
Wasserman, "Wired and Wireless IPv6 Neighbor Discovery
Optimizations", Internet-Draft draft-chakrabarti-nordmark-
6man-efficient-nd-04, October 2013.
[I-D.hong-6lo-ipv6-over-nfc]
Hong, Y., Choi, Y., Youn, J., Kim, D. and J. Choi,
"Transmission of IPv6 Packets over Near Field
Communication", Internet-Draft draft-hong-6lo-ipv6-over-
nfc-01, August 2014.
[I-D.ietf-6lo-6lobac]
Lynn, K., Martocci, J., Neilson, C. and S. Donaldson,
"Transmission of IPv6 over MS/TP Networks", Internet-Draft
draft-ietf-6lo-6lobac-00, July 2014.
[I-D.ietf-6lo-btle]
Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
Shelby, Z. and C. Gomez, "Transmission of IPv6 Packets
over BLUETOOTH(R) Low Energy", Internet-Draft draft-ietf-
6lo-btle-02, June 2014.
[I-D.ietf-6lo-dect-ule]
Mariager, P., Petersen, J., Shelby, Z., Logt, M. and D.
Barthel, "Transmission of IPv6 Packets over DECT Ultra Low
Energy", Internet-Draft draft-ietf-6lo-dect-ule-00, June
2014.
[I-D.ietf-6tisch-architecture]
Thubert, P., Watteyne, 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 2014.
[I-D.ietf-6tisch-terminology]
Palattella, M., Thubert, P., Watteyne, 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.
[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, March 2014.
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[RFC3610] Whiting, D., Housley, R. and N. Ferguson, "Counter with
CBC-MAC (CCM)", RFC 3610, September 2003.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A. and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.
[RFC3971] Arkko, J., Kempf, J., Zill, 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. and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, April 2006.
[RFC4919] Kushalnagar, N., Montenegro, G. and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals", RFC
4919, August 2007.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, January 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.
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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) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The representation above is based on [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
Pascal Thubert, editor
Cisco Systems, Inc
Building D
45 Allee des Ormes - BP1200
MOUGINS - Sophia Antipolis, 06254
FRANCE
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
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