6LoWPAN Working Group                                   J. Nieminen, Ed.
Internet-Draft                                                  B. Patil
Intended status: Standards Track                           T. Savolainen
Expires: January 2, 2012                                      M. Isomaki
                                                               Z. Shelby
                                                                C. Gomez
                                              Universitat Politecnica de
                                                            July 1, 2011

         Transmission of IPv6 Packets over Bluetooth Low Energy


   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

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
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   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
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   include Simplified BSD License text as described in Section 4.e of
   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",
   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.


      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

                  |              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

   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

   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

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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:      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

6.  Additional contributors

   Kanji Kerai, Jari Mutikainen,David Canfeng-Chen and Minjun Xi from
   Nokia have contributed significantly to this document.

7.  Normative References

              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.

              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)
   Itaemerenkatu 11-13
   FI-00180 Helsinki

   Email: johanna.1.nieminen@nokia.com

   Basavaraj Patil
   6021 Connection drive
   Irving, TX  75039

   Email: basavaraj.patil@nokia.com

   Teemu Savolainen
   Hermiankatu 12 D
   FI-33720 Tampere

   Email: teemu.savolainen@nokia.com

   Markus Isomaki
   Keilalahdentie 2-4
   FI-02150 Espoo

   Email: markus.isomaki@nokia.com

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   Zach Shelby
   Hallituskatu 13-17D
   FI-90100 Oulu

   Email: zach.shelby@sensinode.com

   Carles Gomez
   Universitat Politecnica de Catalunya/i2CAT
   C/Esteve Terradas, 7
   Castelldefels  08860

   Email: carlesgo@entel.upc.edu

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