6lpwa X. Vilajosana, Ed.
Internet-Draft Worldsensing
Intended status: Standards Track M. Dohler
Expires: January 9, 2017 King's College London
A. Yegin
Actility
July 8, 2016
Transmission of IPv6 Packets over LoRaWAN
draft-vilajosana-lpwan-lora-hc-00
Abstract
This document describes how IPv6 is transmitted over LoRaWAN using
6LowPAN techniques. LoRaWAN is a wireless communication system for
long-range low-power low-data-rate applications. LoRaWAN networks
typically are laid out in a star topology in the field with gateways
relaying messages between end-devices and a central network server in
the backend, the complete system referred to as star of stars
network.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 9, 2017.
Copyright Notice
Copyright (c) 2016 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
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Overview of LoRaWAN Technology . . . . . . . . . . . . . . . 3
4. Specification of IPv6 over LoRaWAN . . . . . . . . . . . . . 3
4.1. Protocol stack . . . . . . . . . . . . . . . . . . . . . 4
4.2. Link Model . . . . . . . . . . . . . . . . . . . . . . . 4
4.3. Stateless Address Auto-configuration . . . . . . . . . . 5
4.3.1. LoRaWAN Addressing . . . . . . . . . . . . . . . . . 5
4.3.2. Address Auto-Configuration . . . . . . . . . . . . . 6
4.4. Neighbour Discovery . . . . . . . . . . . . . . . . . . . 7
4.5. Header Compression in LoRaWAN . . . . . . . . . . . . . . 9
4.6. Fragmentation in LoRaWAN . . . . . . . . . . . . . . . . 9
5. Internet Connectivity Scenarios . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. External Informative References . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
LoRa is a wireless technology for long-range low-power low-data-rate
applications developed by Semtech, which is used in LoRaWAN networks.
LoRaWAN networks typically are organized in a star-of-stars topology
in which gateways relay messages between end-devices and a central
network server in the backend. Gateways are connected to the network
server via IP links while end-devices use single-hop LoRaWAN
communication to one or many gateways. All communication is
generally bi-directional, although uplink communication from end-
devices to the network server are strongly favoured.
Communication between end-devices and gateways is spread out among
different frequency channels and so-called spreading factors.
Selecting a spreading factor is a trade-off between required link
budget and data rate. Spreading factors create virtual and
orthogonal non-interfering communication channels that enable
simultaneous transmissions. Depending on the used spreading factor,
LoRaWAN data rates range from 0.3 kbps to 50 kbps. To maximize both
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battery life of end-devices and overall network capacity, the LoRaWAN
network infrastructure manages the data rate and RF output for each
end-device individually by means of an adaptive data rate (ADR)
scheme. End-devices may transmit on any channel available at any
time, using any available data rate.
The consolidation of that technology and its important impact in the
M2M market, is triggering the need for end to end IP connectivity
from end devices to the backend server without the need of proxying
roles taken at Gateways. Due to the constrained nature of LoRaWAN
devices, the compression techniques developed by 6LowPAN become
mandatory. The present document specifies how IPv6 and the 6LowPAN
architecture run on top of the LoRaWAN MAC layer.
2. Requirements Language
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 RFC 2119 [RFC2119].
3. Overview of LoRaWAN Technology
TODO briefly describe the technology. Phy layer and modulation. MAC
operation and frame formats.
Figure 1: LoRaWAN Class A transmission and reception window.
|----------------------------| |--------| |--------|
| Tx | | Rx | | Rx |
|----------------------------| |--------| |--------|
|---------|
Rx delay 1
|------------------------|
Rx delay 2
4. Specification of IPv6 over LoRaWAN
The LoRaWAN technology enables low power wide area network coverage
at the cost of reduced data rate and to obey to strict spectrum
occupancy regulations. This imposes strict communication limitations
that make applications using LoRaWAN to contain the amount of data
that is transmitted. 6LoWPAN standards RFC4944, RFC6775, and RFC6282
enable IP connectivity while leverage the overhead of fully IPv6
headers. They also provides standard Internet connectivity by
enabling IPv6 addressing and stateless IPv6 address auto-
configuration, Neighbour Discovery and most importantly Header
Compression. The main difference between IEEE 802.15.4 and LoRaWAN
is that LoRaWAN builds stars and star of stars networks not requiring
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a routing protocol nor multi-hop operation. At the same time LoRaWAN
is subject to bandwidth, data rate, radio duty-cycle regulations and
frame size constraints that impose strict limitation in the protocol
overhead that is supported when compared to IEEE 802.15.4.
4.1. Protocol stack
Figure 2: Protocol Stack for IPv6 over LoRaWAN
+----------------------------------------+ ------------------
| | Transport and
| Upper Layer Protocols | Application Layer
+----------------------------------------+ ------------------
| | |
| IPv6 | |
| | Network
+----------------------------------------+ Layer
|Adaptation Layer for IPv6 over LoRaWAN | |
+----------------------------------------+ ------------------
| |
| IPv6-LOR Addressing Binding | LoRaWAN Link Layer
| | |
+----------------------------------------+ ------------------
| | |
| Activities | LoRaWAN
| Digital Protocol | Physical Layer
| RF Analog | |
| | |
+----------------------------------------+ ------------------
Adaptation layer for IPv6 over LoRaWAN SHALL support neighbour discovery,
address auto-configuration, header compression, and fragmentation and
reassembly.
4.2. Link Model
According to RFC 4861 [RFC4861] a link is "a communication facility
or medium over which nodes can communicate at the link layer, i.e.,
the layer immediately below IPv6."
In LoRaWAN the IPv6 layer is designed to enable transmission of IPv6
packets over LoRaWAN links. The LoRaWAN protocol is in charge of
establishing the pairwise communication between the LoRaWAN gateway
and the LoRaWAN device. The IPv6 adaptation layer however is in
charge of managing header compression and packet fragmentation in
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order to deal with different spreading factors and allowed packet
payload at the underlying MAC layer.
Per this specification, the IPv6 header compression format specified
in RFC 6282 MUST be used [RFC6282] but more drastic compression based
on provisioning an extended context in the Neighbor Solicitation (NS)
is expected in the upcoming revision. The IPv6 payload length can be
derived from the LoRaWAN MAC header length and the possibly elided
IPv6 address can be reconstructed from the link-layer address, used
at the time of LoRaWAN connection establishment. As described in
Section 4.5 context information or more aggressive compression
formats such as RoHC [RFC3095] SHOULD be used at the 6LBR in order to
compress well-known network prefixes and indicated at the specific
field of the IPHC header. This compression will be defined in the
upcomming revisions.
LoRaWAN networks form star topologies or star of stars, having a
point-to-point nature. Address assignment is managed by the 6LBR
that ensures that collisions do not occur. Broadcast features are
used mainly by the 6LBR. 6LN to 6LN communications are always
carried out through the 6LBR and hence it is in charge of relaying
link local packets.
After the LoRaWAN node and the LoRaWAN gateway have established the
LoRaWAN connection, the link is enabled and IPv6 address
configuration and subsequent transmission are able to start.
4.3. Stateless Address Auto-configuration
Nodes (both hosts and routers) in a LoRaWAN network MAY use the
address auto-configuration process. This process relies in the
ability for a node to generate a link-local address for the
communication interface. A link-local address is formed by appending
an identifier of the interface to the well-known link-local prefix
[RFC4291]. Before the link-local address can be assigned to an
interface and used, a node must attempt to verify that this
"tentative" address is not already in use by another node on the
link. This section describes how LoRaWAN nodes determine the address
to be used and how this address is bound to the 6LBR node (or
Gateway).
4.3.1. LoRaWAN Addressing
The DevEUI is a global end-device ID in IEEE EUI64 address space that
uniquely identifies the end-device. The DevEUI is preconfigured at
each node.
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A LoRaWAN device addressing can be conducted in two ways. Over the
air activation (OTAA) and Activation by personalization (ABP). The
former requires 2 MAC layer messages to establish the network address
and security keys (join-request and join-response). The latter
assumes that device address and security keys are pre-programmed at
the nodes and the DevEUI is not mandatory. Lately, the LoRa Alliance
is considering to mandate DevEUI in ABP mode.
Figure 3: DevEUI
+------------+----------------+
| Bit# | [63..0] |
+------------+----------------+
| DevEUI | DevEUI |
+------------+----------------+
4.3.2. Address Auto-Configuration
A LoRaWAN end device performs stateless address auto-configuration as
per [RFC4862]. A 64-bit Interface identifier (IID) for a LoRaWAN
interface MAY be formed by utilizing the 64-bit LoRaWAN DevEUI. That
IID MAY guarantee a stable IPv6 address and MUST be used along the
lifetime of the network.
According to [RFC7136], interface IIDs of all unicast addresses for
LoRaWAN-enabled devices MUST be formed on the basis of 64 bits long
and constructed using the EUI-64 format. LoRaWAN End Device
Addresses MUST follow a stateless address auto-configuration with the
64 bit DevEUI.
[RFC4291] indicates the use of a "Universal/Local" scope bit that
identifies the network device to be locally accessible or globally
accessible. The former SHOULD be followed and LoRaWAN end-devices
SHOULD set to 0 the "Universal/Local" bit. In the case that a
Universally accessible IPv6 address needs to be used a Neighbor
Discovery mechanism and a network commissioning procedure is
required. This procedure is described in Section 4.4.
LoRaWAN IPv6 Network Prefix is build using the link-local prefix
FE80::/64. The IPv6 link-local address for a LoRaWAN-enabled device
is formed by appending the IID, to the prefix, as depicted in
Figure 4.
Duplicate address detection for link-local addresses is performed by
the 6LBR.
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Once a 6LN has established its own link-local address, it starts
sending Router Solicitation messages as described in [RFC4861]
Section 6.3.7.
For non-link-local addresses a 64-bit IID MAY be formed by utilizing
the 64-bit LoRaWAN DevEUI as described in this section. A 6LN can
also use a the EUI-64 generated IID from the MAC Layer. The non-
link-local addresses generated by the 6LN MUST be registered with the
6LBR.
The mechanism by which the 6LBR obtains an IPv6 prefix is out of
scope of this document but can for example be accomplished by using
Unique Local IPv6 Unicast Addresses (ULA) [RFC4193]. As 6LNs MUST
always communicate to the 6LBR, the "on-link" flag (L) MUST be set to
zero in the Prefix Information Option [RFC4861]. This will always
happen even when the destination is another 6LN using the same
prefix.
Figure 4: IPv6 link-local address in LoRaWAN
0 0 0 0 1
0 1 6 9 2
0 0 4 6 7
+----------+-----------------+---------------+----------------+
|1111111010| zeros | DevEUI |
+----------+-----------------+---------------+----------------+
| |
| /-------------------------- 128 bits ----------------------/|
| |
4.4. Neighbour Discovery
Neighbour Discovery is addressed following the classical ND approach
as defined by [RFC4861] , [RFC4862] and [RFC6775]. As LoRaWAN
networks can be organized in star topologies or star of stars
topologies the LoRaWAN manager can take two differentiated roles.
For single star topologies the LoRaWAN manager will act as a 6LBR and
MUST keep track of the nodes addresses within the link, otherwise it
acts as 6LR and forwards Node Solicitation and ARO requests to the
6LBR in the network.
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Figure 5: ND Procedure for a single star topology
LoRaWAN node LoRaWAN 6LR/6LBR
| Router Solicitation (RS) |
|-------------------------------->|
| |
| Router Advertisement (RA) |
|<--------------------------------|
| |
| Neighbour Solicitation (NS) |
|-------------------------------->|
| |
| Neighbour Advertisement (NA) |
|<--------------------------------|
| |
When a LoRaWAN node joins a network, it sends an RS to the 6LR
containing its IID as described in Section 4.3.2. The 6LBR router
answers with a RA containing its IIDs and prefixes. Hosts receive
Router Advertisement messages containing the Authoritative Border
Router Option (ABRO), the IIDs of the 6LR or 6LBR and MAY optionally
contain one or more 6LoWPAN Context Options (6COs). They also
contain the existing Prefix Information Options (PIOs) as described
in [RFC4861].
When a host has configured a non-link-local IPv6 address, it
registers that address with one or more of its default routers using
the Address Registration Option (ARO) in an NS message. The host
chooses a lifetime of the registration and repeats the ARO
periodically (before the lifetime runs out) to maintain the
registration. The host needs to refresh its prefix and context
information by sending a new unicast NS. As LoRaWAN might use very
low data rates it is recommended to use large Lifetime configurations
assuming that LoRaWAN devices are not mobile. According to [RFC6775]
the maximum Router Lifetime is about 18 hours, whereas the maximum
Registration Lifetime is about 45.5 days.
Future versions of this document should consider the ND approach
described in [efficient-nd]
The ND Procedure for star of stars follows the multi-hop ND approach
described by [RFC6775]. The multihop distribution relies on RS
messages and RA messages sent between routers, and using the ABRO
version number to control the propagation of the information
(prefixes and context information) that is being sent in the RAs.
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Figure 6: ND Procedure for star of stars in LoRaWAN.
LoRaWAN node LoRaWAN 6LR LoRaWAN 6LBR
| Router Solicitation (RS) | |
|------------------------------->| |
| | |
| Router Advertisement (RA) | |
|<-------------------------------| |
| | |
| Node Registration (NR) | |
|------------------------------->| |
| | Neighbour Solicitation (NS) |
| |--------------------------------->|
| | |
| | Neighbour Advertisement (NA) |
| |<---------------------------------|
| Node Confirmation (NC) | |
|<-------------------------------| |
| | |
4.5. Header Compression in LoRaWAN
TODO.
4.6. Fragmentation in LoRaWAN
TODO.
5. Internet Connectivity Scenarios
TODO.
6. Security Considerations
The transmission of IPv6 over LoRaWAN links has similar requirements
and concerns for security as for IEEE 802.15.4. LoRaWAN Link Layer
security considerations are covered by the LoRaWAN Specification
[LoRaSpec].
7. IANA Considerations
There are no IANA considerations related to this document.
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8. Acknowledgements
The authors would like to acknowledge the guidance and input provided
by Pascal Thubert.
9. References
9.1. Normative References
[RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6
Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
February 2014, <http://www.rfc-editor.org/info/rfc7136>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<http://www.rfc-editor.org/info/rfc6775>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011,
<http://www.rfc-editor.org/info/rfc6282>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<http://www.rfc-editor.org/info/rfc4193>.
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[RFC3095] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
Hannu, H., Jonsson, L-E., Hakenberg, R., Koren, T., Le,
K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
Compression (ROHC): Framework and four profiles: RTP, UDP,
ESP, and uncompressed", RFC 3095, DOI 10.17487/RFC3095,
July 2001, <http://www.rfc-editor.org/info/rfc3095>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
9.2. External Informative References
[LoRaSpec]
LoRa Alliance, "LoRaWAN Specification Rev.3", April 2014.
[efficient-nd]
Thubert, P., Nordmark, E., and S. Chakrabarti, "An Update
to 6LoWPAN ND", draft-thubert-6lo-rfc6775-update-00 , May
2016.
Authors' Addresses
Xavier Vilajosana (editor)
Worldsensing
483 Arago 4th floor
Barcelona, Catalonia 08013
Spain
Email: xvilajosana@worldsensing.com
Mischa Dohler
King's College London
London, London
UK
Email: mischa.dohler@kcl.ac.uk
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Alper Yegin
Actility
Paris, Paris
FR
Email: alper.yegin@actility.com
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