6LoWPAN Working Group J. Nieminen, Ed.
Internet-Draft B. Patil
Intended status: Standards Track T. Savolainen
Expires: January 2, 2012 M. Isomaki
Nokia
Z. Shelby
Sensinode
C. Gomez
Universitat Politecnica de
Catalunya/i2CAT
July 1, 2011
Transmission of IPv6 Packets over Bluetooth Low Energy
draft-ietf-6lowpan-btle-01
Abstract
Bluetooth Low Energy is a low power air interface technology defined
by the Bluetooth Special Interest Group (BT SIG). The standard
Bluetooth radio has been widely implemented and available in mobile
phones, notebook computers, audio headsets and many other devices.
The low power version of Bluetooth is a new specification and enables
the use of this air interface with devices such as sensors, smart
meters, appliances, etc. The low power variant of Bluetooth is
commonly specified in revision 4.0 of the bluetooth specifications
and commonly refered to as bluetooth 4.0. This document describes
how IPv6 is transported over Bluetooth Low Energy using 6LoWPAN
techniques.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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 January 2, 2012.
Copyright Notice
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Copyright (c) 2011 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Bluetooth Low Energy . . . . . . . . . . . . . . . . . . . . . 4
2.1. Protocol stack . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Link layer roles and topology . . . . . . . . . . . . . . 5
3. Specificaion of IPv6 over Bluetooth Low Energy . . . . . . . . 5
3.1. Protocol stack . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Link model . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2.1. IPv6 Address configuration . . . . . . . . . . . . . . 6
3.2.2. Unicast and Multicast address mapping . . . . . . . . 7
3.3. Internet connectivity scenarios . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Additional contributors . . . . . . . . . . . . . . . . . . . 9
7. Normative References . . . . . . . . . . . . . . . . . . . . . 9
Appendix A. Bluetooth Low Energy basics . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
Bluetooth Low Energy (BT-LE) is a radio technology targeted for
devices that operate with coin cell batteries or minimalistic power
sources, which means that low power consumption is essential. BT-LE
is an especially attractive technology for the Internet of Things
applications, such as health monitors, environmental sensing,
proximity applications and many others.
Considering the expected explosion in the number of sensors and
Internet connected devices and things, IPv6 is an ideal protocol due
to the large address space it provides. In addition, IPv6 provides
tools for autoconfiguration,which is particularly suitable for sensor
network applications and nodes which have very limited processing
power or a full-fledged operating system.
[RFC4944] specifies the transmission of IPv6 over IEEE 802.15.4. The
Bluetooth Low Energy link in many respects has similar
characteristics to that of IEEE 802.15.4. Many of the mechanisms
defined in [RFC4944] can be applied to the transmission of IPv6 on
Bluetooth Low Energy links. This document specifies the details of
IPv6 transmission over Bluetooth Low Energy links.
1.1. 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].
1.2. Terminology
Bluetooth Low Energy
Bluetooth low energy is a low power air interface technology
specified by the Bluetooth Special Interest Group (SIG). BT-LE is
specified in Revision 4.0 of the bluetooth specifications.
Gateway
Network element connecting the BT-LE sensors to the Internet. Can
be e.g a home gateway or a mobile device.
6LR and 6LBR
These terms correspond to those defined in [I-D.ietf-6lowpan-nd]
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2. Bluetooth Low Energy
BT-LE is designed for transferring small amounts of data (in most
cases less than 10 bytes) infrequently (e.g. every 500 ms) at modest
data rates (e.g. 300 kbps) at a very low cost per bit.
BT-LE is an integral part of the BT4.0 specification. Devices such
as mobile phones, notebooks, tablets and other handheld computing
devices which will include BT4.0 chipsets in the near future will
have the low-energy functionality of bluetooth. BT-LE will also be
included in many different types of accessories that collaborate with
mobile devices such as phones, tablets and notebook computers. An
example of a use case for a BT-LE accessory is a heart rate monitor
that sends data via the mobile phone to a server on the Internet.
2.1. Protocol stack
The lower layer of the BT-LE stack consists of the Physical (PHY) and
the Link Layer (LL). Link Layer is responsible for managing the
channels and Physical Layer transmits and receives the actual
packets. The upper layer consists of the Logical Link Control and
Adaptation Protocol (L2CAP), Generic Attribute protocol (GATT) and
Generic Attribute profile (GAP) as shown in Figure 1. GATT and BT-LE
profiles together enable the creation of applications in a
standardized way without using IP. L2CAP provides multiplexing
capability by multiplexing the data channels from the above layers.
L2CAP also provides fragmentation and reassembly for larger data
packets.
+----------------------------------------+
| Applications |
+----------------------------------------+
| Generic Access Profile |
+----------------------------------------+
| Generic Attribute Profile |
+----------------------------------------+
| Attribute Protocol |Security Manager |
+--------------------+-------------------+
| Logical Link Control and Adaptation |
+--------------------+-------------------+
| Host Controller Interface |
+--------------------+-------------------+
| Link Layer | Direct Test Mode |
+--------------------+-------------------+
| Physical Layer |
+--------------------+-------------------+
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Figure 1: BT-LE Protocol Stack
2.2. Link layer roles and topology
BT-LE defines two Link Layer roles: the Master Role and the Slave
Role. A device in the Master Role, which is called master, can
manage multiple simultaneous connections with a number of devices in
the Slave Role, called slaves. A slave can only be connected to a
single master. Hence, a BT-LE network (i.e. a BT-LE piconet) follows
a star topology.
A master is assumed to be less constrained than a slave. Hence,
master and slave can correspond with 6LoWPAN Border Router (6LBR) and
host, respectively.
In BT-LE, communication only takes place between a master and a
slave. Hence, in a BT-LE network using IP, a radio hop is equivalent
to an IP link and vice versa.
3. Specificaion of IPv6 over Bluetooth Low Energy
BT-LE technology sets strict requirements for low power consumption
and thus limits the allowed protocol overhead. 6LoWPAN standard
[RFC4944] provides useful generic functionality like header
compression, link-local IPv6 addresses, Neighbor Discovery and
stateless IP-address autoconfiguration for reducing the overhead in
802.15.4 networks. This functionality can be partly applied to
BT-LE.
A significant difference between IEEE 802.15.4 and BT-LE is that the
former supports the mesh topology (and requires a routing protocol),
whereas BT-LE does not currently support the formation of multihop
networks. In consequence, the mesh header defined in [RFC4944] for
mesh under routing SHOULD NOT be used in BT-LE networks. On the
other hand, a BT-LE device MUST NOT play the role of a 6LoWPAN
Router.
When BT-LE is applied in sensors, generated data usually fits into
one Link Layer packet (23 bytes, maximum L2CAP payload size) that is
transferred to the collector device periodically. IP data packets
may be much larger and hence MTU size should be the size of the IP
data packet. Larger L2CAP packets can be transferred with the
Segmentation And Reassembly (SAR) feature of the Link Layer. This
specification requires that SAR functionality MUST be provided in the
Link Layer up to the IPv6 MTU of 1280 bytes. Therefore, the 6LoWPAN
fragmentation functinoality defined in [RFC4944] SHOULD NOT be used
in BT-LE neworks.
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3.1. Protocol stack
In order to enable transmission of IPv6 packets over BT-LE, a new
fixed channel ID SHOULD be reserved for IPv6 traffic in the BT-SIG.
This specification defines the use of channel ID 0x07 for this
purpose. Figure 2 illustrates IPv6 over BT-LE stack.
+-------------------+
| UDP/TCP |
+-------------------+
| IPv6 |
+-------------------+
| 6LoWPAN |
+-------------------+
| BT-LE L2CAP |
+-------------------+
| BT-LE Link Layer |
+-------------------+
| BT-LE Physical |
+-------------------+
Figure 2: IPv6 over BT-LE Stack
3.2. Link model
3.2.1. IPv6 Address configuration
The Interface Identifier for a BT-LE interface MUST be formed from
the 48-bit public device Bluetooth address as per the "IPv6 over
Ethernet" specification [RFC2464]. An IPv6 prefix used for stateless
autoconfiguration [RFC4862] of a BT-LE interface MUST have a length
of 64 bits.
The IPv6 link-local address [RFC4291] for a BT-LE interface is formed
by appending the Interface Identifier, as defined above, to the
prefix FE80::/64, as depicted in Figure 3.
10 bits 54 bits 64 bits
+----------+-----------------+----------------------+
|1111111010| zeros | Interface Identifier |
+----------+-----------------+----------------------+
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Figure 3: IPv6 link-local address in BT-LE
In a link-local communication, both the IPv6 source and destination
addresses can be elided. In fact, the node that receives a data
channel PDU through a Link Layer connection MAY infer that the IPv6
destination address of the packet is its own IPv6 address. If a node
knows the IID of the other endpoint of the Link Layer connection, the
IPv6 source address MAY also be elided. A device MAY learn the IID
of the other endpoint of a Link Layer connection e.g. from the RS/RA/
NS/NA Neighbor Discovery (ND) message exchange. The device MAY
maintain a Neighbor Cache, in which the entries include both the IID
of the neighbor and the Access Address that identifies the Link Layer
connection with the neighbor. A device MAY also derive the IID of
the other endpoint of a Link Layer connection from the Link Layer
connection establishment messages.
When a BT-LE slave transmits an IPv6 packet to a remote destination
using global IPv6 addresses, the slave MAY elide the IPv6 source
address. This is possible since 1) the master/6LBR has previously
assigned the prefix to the slaves; and 2) the master/6LBR maintains a
Neighbor Cache that relates the Access Address of each Link Layer
connection and the Interface Identifier of the corresponding slave.
The slave MAY also elide the prefix of the destination IPv6 address
if a context is defined for the IPv6 destination address.
When a master/6LBR receives an IPv6 packet sent by a remote node
outside the BT-LE network, and the destination of the packet is a
slave, the master/6LBR MAY elide the Interface Identifier of the IPv6
destination address by exploiting the information contained in the
table mentioned above. The prefixes of the IPv6 destination and
source addresses MAY also be elided if a context is defined for them.
3.2.2. Unicast and Multicast address mapping
In BT-LE, address resolution should be used for finding the Access
Address of the LL connection with the target node. The master cannot
simultaneously transmit a packet to multiple slaves (each slave
listens at different times). One option is: when a master has to
transmit an IPv6 multicast packet, it unicasts the corresponding
BT-LE packet to each of its slaves. However, if the master is
battery-powered, this may not be energy-efficient. In the opposite
direction, a slave can only transmit data to a single destination
(i.e. the master). Hence, if a slave transmits an IPv6 multicast
packet, the slave can unicast the corresponding BT-LE packet to the
master.
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3.3. Internet connectivity scenarios
In a typical scenario, BT-LE network is connected to the Internet.
h ____________
\ / \
h ---- 6LBR --- | Internet |
/ \____________/
h
h: host
<-- BT-LE --> 6LBR: 6LoWPAN Border Router
Figure 4: BT-LE network connected to the Internet
In some scenarios, the BT-LE network may transiently or permanently
be an isolated network.
h h h: host
\ / 6LBR: 6LoWPAN Border Router
h --- 6LBR -- h
/ \
h h
Figure 5: Isolated BT-LE network
4. IANA Considerations
This document does not have any IANA requests at this time. This may
change with further development of the specification.
5. Security Considerations
The transmission of IPv6 over bluetooth low energy links has similar
requirements and concerns for security as for IEEE 802.15.4.
Security at the IP layer needs to be reviewed as part of the
development of the IPv6 over Bluetooth Low Energy specification.
BT-LE Link Layer supports encryption and authentication by using the
CCM mechanism and a 128-bit AES block cipher. Upper layer security
mechanisms may exploit this functionality when it is available.
(Note: CCM does not consume bytes from the maximum per-packet L2CAP
data size, since the link layer data unit has a specific field for
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them when they are used.)
Key management in BT-LE is provided by the Security Manager Protocol
(SMP).
6. Additional contributors
Kanji Kerai, Jari Mutikainen,David Canfeng-Chen and Minjun Xi from
Nokia have contributed significantly to this document.
7. Normative References
[I-D.ietf-6lowpan-hc]
Hui, J. and P. Thubert, "Compression Format for IPv6
Datagrams in Low Power and Lossy Networks (6LoWPAN)",
draft-ietf-6lowpan-hc-15 (work in progress),
February 2011.
[I-D.ietf-6lowpan-nd]
Shelby, Z., Chakrabarti, S., and E. Nordmark, "Neighbor
Discovery Optimization for Low Power and Lossy Networks
(6LoWPAN)", draft-ietf-6lowpan-nd-17 (work in progress),
June 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, December 1998.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[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.
[RFC4994] Zeng, S., Volz, B., Kinnear, K., and J. Brzozowski,
"DHCPv6 Relay Agent Echo Request Option", RFC 4994,
September 2007.
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Appendix A. Bluetooth Low Energy basics
This section will provide background material on the basics of
bluetooth low energy.
Authors' Addresses
Johanna Nieminen (editor)
Nokia
Itaemerenkatu 11-13
FI-00180 Helsinki
Finland
Email: johanna.1.nieminen@nokia.com
Basavaraj Patil
Nokia
6021 Connection drive
Irving, TX 75039
USA
Email: basavaraj.patil@nokia.com
Teemu Savolainen
Nokia
Hermiankatu 12 D
FI-33720 Tampere
Finland
Email: teemu.savolainen@nokia.com
Markus Isomaki
Nokia
Keilalahdentie 2-4
FI-02150 Espoo
Finland
Email: markus.isomaki@nokia.com
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Zach Shelby
Sensinode
Hallituskatu 13-17D
FI-90100 Oulu
Finland
Email: zach.shelby@sensinode.com
Carles Gomez
Universitat Politecnica de Catalunya/i2CAT
C/Esteve Terradas, 7
Castelldefels 08860
Spain
Email: carlesgo@entel.upc.edu
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