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Versions: (draft-ietf-6lowpan-btle) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 RFC 7668

6Lo Working Group                                            J. Nieminen
Internet-Draft                                             T. Savolainen
Intended status: Standards Track                              M. Isomaki
Expires: November 16, 2015                                         Nokia
                                                                B. Patil
                                                                    AT&T
                                                               Z. Shelby
                                                                     Arm
                                                                C. Gomez
                              Universitat Politecnica de Catalunya/i2CAT
                                                            May 15, 2015


                   IPv6 over BLUETOOTH(R) Low Energy
                         draft-ietf-6lo-btle-12

Abstract

   Bluetooth Smart is the brand name for the Bluetooth low energy
   feature in the Bluetooth specification defined by the Bluetooth
   Special Interest Group.  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 specification that enables the use of this air interface with
   devices such as sensors, smart meters, appliances, etc.  The low
   power variant of Bluetooth is standardized since the revision 4.0 of
   the Bluetooth specifications, although version 4.1 or newer is
   required for IPv6.  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 November 16, 2015.





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Copyright Notice

   Copyright (c) 2015 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 and restrictions with respect
   to this document.  Code Components extracted from this document must
   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology and Requirements Language . . . . . . . . . .   3
   2.  Bluetooth Low Energy  . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Bluetooth LE stack  . . . . . . . . . . . . . . . . . . .   4
     2.2.  Link layer roles and topology . . . . . . . . . . . . . .   5
     2.3.  Bluetooth LE device addressing  . . . . . . . . . . . . .   5
     2.4.  Bluetooth LE packets sizes and MTU  . . . . . . . . . . .   5
   3.  Specification of IPv6 over Bluetooth Low Energy . . . . . . .   6
     3.1.  Protocol stack  . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Link model  . . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.1.  Stateless address autoconfiguration . . . . . . . . .   8
       3.2.2.  Neighbor discovery  . . . . . . . . . . . . . . . . .  10
       3.2.3.  Header compression  . . . . . . . . . . . . . . . . .  10
         3.2.3.1.  Remote destination example  . . . . . . . . . . .  12
         3.2.3.2.  Example of registration of multiple-addresses . .  13
       3.2.4.  Unicast and Multicast address mapping . . . . . . . .  13
     3.3.  Subnets and Internet connectivity scenarios . . . . . . .  13
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   6.  Additional contributors . . . . . . . . . . . . . . . . . . .  15
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Bluetooth low energy (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.  Bluetooth LE is



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   especially attractive technology for Internet of Things applications,
   such as health monitors, environmental sensing, proximity
   applications and many others.

   Considering the potential for the exponential growth in the number of
   sensors and Internet connected devices, IPv6 is an ideal protocol due
   to the large address space it provides.  In addition, IPv6 provides
   tools for stateless address autoconfiguration, which is particularly
   suitable for sensor network applications and nodes which have very
   limited processing power or lack a full-fledged operating system.

   RFC 4944 [RFC4944] specifies the transmission of IPv6 over IEEE
   802.15.4.  The Bluetooth LE link in many respects has similar
   characteristics to that of IEEE 802.15.4.  Many of the mechanisms
   defined in the RFC 4944 can be applied to the transmission of IPv6 on
   Bluetooth LE links.  This document specifies the details of IPv6
   transmission over Bluetooth LE links.

1.1.  Terminology and 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].

   The terms 6LN, 6LR and 6LBR are defined as in [RFC6775], with an
   addition that Bluetooth LE central and Bluetooth LE peripheral (see
   Section 2.2) can both be either 6LN or 6LBR.

2.  Bluetooth Low Energy

   Bluetooth LE is designed for transferring small amounts of data
   infrequently at modest data rates at a very low cost per bit.
   Bluetooth Special Interest Group (Bluetooth SIG) has introduced two
   trademarks, Bluetooth Smart for single-mode devices (a device that
   only supports Bluetooth LE) and Bluetooth Smart Ready for dual-mode
   devices (devices that support both Bluetooth and Bluetooth LE).  In
   the rest of the document, the term Bluetooth LE refers to both types
   of devices.

   Bluetooth LE was introduced in Bluetooth 4.0, enhanced in Bluetooth
   4.1 [BTCorev4.1], and developed even further in successive versions.
   Bluetooth SIG has also published Internet Protocol Support Profile
   (IPSP) [IPSP], which includes Internet Protocol Support Service
   (IPSS).  The IPSP enables discovery of IP-enabled devices and
   establishment of link-layer connection for transporting IPv6 packets.
   IPv6 over Bluetooth LE is dependent on both Bluetooth 4.1 and IPSP
   1.0 or newer.




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   Devices such as mobile phones, notebooks, tablets and other handheld
   computing devices which will include Bluetooth 4.1 chipsets will also
   have the low-energy functionality of Bluetooth.  Bluetooth 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 Bluetooth LE accessory is
   a heart rate monitor that sends data via the mobile phone to a server
   on the Internet.

2.1.  Bluetooth LE stack

   The lower layer of the Bluetooth LE stack consists of the Physical
   (PHY) and the Link Layer (LL).  The Physical Layer transmits and
   receives the actual packets.  The Link Layer is responsible for
   providing medium access, connection establishment, error control and
   flow control.  The upper layer consists of the Logical Link Control
   and Adaptation Protocol (L2CAP), Attribute Protocol (ATT), Generic
   Attribute Profile (GATT) and Generic Access Profile (GAP) as shown in
   Figure 1.  The device internal Host Controller Interface (HCI)
   separates the lower layers, often implemented in the Bluetooth
   controller, from higher layers, often implemented in the host stack.
   GATT and Bluetooth 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
   large data packets.


        +-------------------------------------------------+
        |              Applications                       |
        +---------------------------------------+---------+
        |        Generic Attribute Profile      | Generic |
        +--------------------+------------------+ Access  |
        | Attribute Protocol | Security Manager | Profile |
        +--------------------+------------------+---------+
        |  Logical Link Control and Adaptation Protocol   |
   - - -+-----------------------+-------------------------+- - - HCI
        |      Link Layer       |    Direct Test Mode     |
        +-------------------------------------------------+
        |             Physical Layer                      |
        +-------------------------------------------------+


                   Figure 1: Bluetooth LE Protocol Stack







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2.2.  Link layer roles and topology

   Bluetooth LE defines two GAP roles of relevance herein: the Bluetooth
   LE central role and the Bluetooth LE peripheral role.  A device in
   the central role, which is called central from now on, has
   traditionally been able to manage multiple simultaneous connections
   with a number of devices in the peripheral role, called peripherals
   from now on.  A peripheral is commonly connected to a single central,
   but since Bluetooth 4.1 can also connect to multiple centrals.  In
   this document for IPv6 networking purposes the Bluetooth LE network
   (i.e. a Bluetooth LE piconet) follows a star topology shown in the
   Figure 2, where the router typically implements the Bluetooth LE
   central role and nodes implement the Bluetooth LE peripheral role.
   In the future mesh networking may be defined for IPv6 over Bluetooth
   LE.

                  Peripheral --.      .-- Peripheral
                                \    /
                Peripheral ---- Central ---- Peripheral
                                /    \
                  Peripheral --'      '-- Peripheral

                   Figure 2: Bluetooth LE Star Topology

   In Bluetooth LE, direct communication only takes place between a
   central and a peripheral.  This means that inherently the Bluetooth
   LE star represents a hub and spokes link model.

2.3.  Bluetooth LE device addressing

   Every Bluetooth LE device is identified by a 48-bit device address.
   The Bluetooth specification describes the device address of a
   Bluetooth LE device as:"Devices are identified using a device
   address.  Device addresses may be either a public device address or a
   random device address."  [BTCorev4.1].  The public device addresses
   are based on the IEEE 802-2001 standard [IEEE802-2001].  The random
   device addresses are generated as defined in the Bluetooth
   specification.  This typically happens at every power cycle of a
   device.  In random addresses all 48 bits are randomized.  Bluetooth
   LE does not support device address collision avoidance or detection.
   However, these 48 bit random device addresses have a very small
   probability of being in conflict within a typical deployment.

2.4.  Bluetooth LE packets sizes and MTU

   Optimal MTU defined for L2CAP fixed channels over Bluetooth LE is 27
   bytes including the L2CAP header of four bytes.  Default MTU for
   Bluetooth LE is hence defined to be 27 bytes.  Therefore, excluding



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   L2CAP header of four bytes, protocol data unit (PDU) size of 23 bytes
   is available for upper layers.  In order to be able to transmit IPv6
   packets of 1280 bytes or larger, link layer fragmentation and
   reassembly solution is provided by the L2CAP layer.  The IPSP defines
   means for negotiating up a link-layer connection that provides MTU of
   1280 bytes or higher for the IPv6 layer [IPSP].  The link-layer MTU
   is negotiated separately for each direction.  Implementations that
   require single link-layer MTU value SHALL use the smallest of the
   possibly different MTU values.

3.  Specification of IPv6 over Bluetooth Low Energy

   Bluetooth LE technology sets strict requirements for low power
   consumption and thus limits the allowed protocol overhead. 6LoWPAN
   standards [RFC6775], and [RFC6282] provide useful functionality for
   reducing overhead, which are applied to Bluetooth LE.  This
   functionality comprises of link-local IPv6 addresses and stateless
   IPv6 address autoconfiguration (see Section 3.2.1), Neighbor
   Discovery (see Section 3.2.2) and header compression (see
   Section 3.2.3).  Fragmentation features from 6LoWPAN standards are
   not used due Bluetooth LE's link layer fragmentation support (see
   Section 2.4).

   A significant difference between IEEE 802.15.4 and Bluetooth LE is
   that the former supports both star and mesh topology (and requires a
   routing protocol), whereas Bluetooth LE does not currently support
   the formation of multihop networks at the link layer.

   In Bluetooth LE a central node is assumed to be less constrained than
   a peripheral node.  Hence, in the primary deployment scenario central
   and peripheral will act as 6LoWPAN Border Router (6LBR) and a 6LoWPAN
   Node (6LN), respectively.

   Before any IP-layer communications can take place over Bluetooth LE,
   Bluetooth LE enabled nodes such as 6LNs and 6LBRs have to find each
   other and establish a suitable link-layer connection.  The discovery
   and Bluetooth LE connection setup procedures are documented by
   Bluetooth SIG in the IPSP specification [IPSP].

   In the rare case of Bluetooth LE random device address conflict, a
   6LBR can detect multiple 6LNs with the same Bluetooth LE device
   address, as well as a 6LN with the same Bluetooth LE address as the
   6LBR.  The 6LBR MUST ignore 6LNs with the same device address the
   6LBR has, and the 6LBR MUST have at most one connection for a given
   Bluetooth LE device address at any given moment.  This will avoid
   addressing conflicts within a Bluetooth LE network.  The IPSP depends
   on Bluetooth version 4.1, and hence both Bluetooth version 4.1, or




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   newer, and IPSP version 1.0, or newer, are required for IPv6
   communications.

3.1.  Protocol stack

   Figure 3 illustrates IPv6 over Bluetooth LE stack including the
   Internet Protocol Support Service.  UDP and TCP are provided as
   examples of transport protocols, but the stack can be used by any
   other upper layer protocol capable of running atop of IPv6.  The
   6LoWPAN layer runs on top of Bluetooth LE L2CAP layer.

          +---------+  +----------------------------+
          |  IPSS   |  |       UDP/TCP/other        |
          +---------+  +----------------------------+
          |  GATT   |  |            IPv6            |
          +---------+  +----------------------------+
          |  ATT    |  |  6LoWPAN for Bluetooth LE  |
          +---------+--+----------------------------+
          |          Bluetooth LE L2CAP             |
     -  - +-----------------------------------------+- - - HCI
          |        Bluetooth LE Link Layer          |
          +-----------------------------------------+
          |         Bluetooth LE Physical           |
          +-----------------------------------------+

                  Figure 3: IPv6 over Bluetooth LE Stack

3.2.  Link model

   The concept of IPv6 link (layer 3) and the physical link (combination
   of PHY and MAC) needs to be clear and the relationship has to be well
   understood in order to specify the addressing scheme for transmitting
   IPv6 packets over the Bluetooth LE link.  RFC 4861 [RFC4861] defines
   a link as "a communication facility or medium over which nodes can
   communicate at the link layer, i.e., the layer immediately below
   IPv6."

   In the case of Bluetooth LE, 6LoWPAN layer is adapted to support
   transmission of IPv6 packets over Bluetooth LE.  The IPSP defines all
   steps required for setting up the Bluetooth LE connection over which
   6LoWPAN can function [IPSP], including handling the link-layer
   fragmentation required on Bluetooth LE, as described in Section 2.4.
   Even though MTUs larger than 1280 bytes can be supported, use of 1280
   byte is RECOMMENDED in order to avoid need for Path MTU discovery
   procedures.






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   While Bluetooth LE protocols, such as L2CAP, utilize little-endian
   byte orderering, IPv6 packets MUST be transmitted in big endian order
   (network byte order).

   This specification requires IPv6 header compression format specified
   in RFC 6282 to be used [RFC6282].  It is assumed that the IPv6
   payload length can be inferred from the L2CAP header length and the
   possibly elided IPv6 address can be inferred from the link-layer
   address, at the time of Bluetooth LE connection establishment, from
   the HCI Connection Handle during connection, and from context if any.

   Bluetooth LE connections used to build a star topology are point-to-
   point in nature, as Bluetooth broadcast features are not used for
   IPv6 over Bluetooth LE.  For Bluetooth LE multilink model has been
   chosen.  Because of this, link-local multicast communications can
   happen only within a single Bluetooth LE connection, and thus 6LN-to-
   6LN communications using link-local addresses are not possible. 6LNs
   connected to the same 6LBR has to communicate with each other by
   using the shared prefix used on the subnet.  The 6LBR ensures address
   collisions do not occur (see Section 3.2.2).

   After the peripheral and central have connected at the Bluetooth LE
   level, the link can be considered up and IPv6 address configuration
   and transmission can begin.

3.2.1.  Stateless address autoconfiguration

   At network interface initialization, both 6LN and 6LBR SHALL generate
   and assign to the Bluetooth LE network interface IPv6 link-local
   addresses [RFC4862] based on the 48-bit Bluetooth device addresses
   (see Section 2.3) that were used for establishing underlying
   Bluetooth LE connection.  Following guidance of [RFC7136], a 64-bit
   Interface Identifier (IID) is formed from 48-bit Bluetooth device
   address by inserting two octets, with hexadecimal values of 0xFF and
   0xFE in the middle of the 48-bit Bluetooth device address as shown in
   Figure 4.  In the Figure letter 'b' represents a bit from Bluetooth
   device address, copied as is without any changes on any bit.  This
   means that no bit in IID indicates whether the underlying Bluetooth
   device address is public or random.












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   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |bbbbbbbbbbbbbbbb|bbbbbbbb11111111|11111110bbbbbbbb|bbbbbbbbbbbbbbbb|
   +----------------+----------------+----------------+----------------+


         Figure 4: Formation of IID from Bluetooth device adddress

   The IID is then appended with prefix fe80::/64, as described in RFC
   4291 [RFC4291] and as depicted in Figure 5.  The same link-local
   address SHALL be used for the lifetime of the Bluetooth LE L2CAP
   channel.  (After Bluetooth LE logical link has been established, it
   is referenced with a Connection Handle in HCI.  Thus possibly
   changing device addresses do not impact data flows within existing
   L2CAP channel.  Hence there is no need to change IPv6 link-local
   addresses even if devices change their random device addresses during
   L2CAP channel lifetime).


             10 bits        54 bits             64 bits
           +----------+-----------------+----------------------+
           |1111111010|       zeros     | Interface Identifier |
           +----------+-----------------+----------------------+


             Figure 5: IPv6 link-local address in Bluetooth LE

   A 6LN MUST join the all-nodes multicast address.  There is no need
   for 6LN to join the solicited-node multicast address, since 6LBR will
   know device addresses and hence link-local addresses of all connected
   6LNs.  The 6LBR will ensure no two devices with the same Bluetooth LE
   device address are connected at the same time.  Effectively duplicate
   address detection for link-local addresses is performed by the 6LBR's
   software responsible of discovery of IP-enabled Bluetooth LE nodes
   and of starting Bluetooth LE connection establishment procedures.
   This approach increases complexity of 6LBR, but reduces power
   consumption on both 6LN and 6LBR at link establishment phase by
   reducing number of mandatory packet transmissions.

   After link-local address configuration, 6LN sends 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 48-bit Bluetooth device address.  A 6LN can also use a randomly
   generated IID (see Section 3.2.2), for example, as discussed in
   [I-D.ietf-6man-default-iids], or use alternatice schemes such as
   Cryptographically Generated Addresses (CGA) [RFC3972], privacy



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   extensions [RFC4941], Hash-Based Addresses (HBA, [RFC5535]), or
   DHCPv6 [RFC3315].  The non-link-local addresses 6LN generates MUST be
   registered with 6LBR as described in Section 3.2.2.

   The tool for a 6LBR to obtain an IPv6 prefix for numbering the
   Bluetooth LE network is out of scope of this document, but can be,
   for example, accomplished via DHCPv6 Prefix Delegation [RFC3633] or
   by using Unique Local IPv6 Unicast Addresses (ULA) [RFC4193].  Due to
   the link model of the Bluetooth LE (see Section 2.2) the 6LBR MUST
   set the "on-link" flag (L) to zero in the Prefix Information Option
   [RFC4861].  This will cause 6LNs to always send packets to the 6LBR,
   including the case when the destination is another 6LN using the same
   prefix.

3.2.2.  Neighbor discovery

   'Neighbor Discovery Optimization for IPv6 over Low-Power Wireless
   Personal Area Networks (6LoWPANs)' [RFC6775] describes the neighbor
   discovery approach as adapted for use in several 6LoWPAN topologies,
   including the mesh topology.  Bluetooth LE does not support mesh
   networks and hence only those aspects that apply to a star topology
   are considered.

   The following aspects of the Neighbor Discovery optimizations
   [RFC6775] are applicable to Bluetooth LE 6LNs:

   1.  A Bluetooth LE 6LN MUST NOT register its link-local address.  A
   Bluetooth LE 6LN MUST register its non-link-local addresses with the
   6LBR by sending a Neighbor Solicitation (NS) message with the Address
   Registration Option (ARO) and process the Neighbor Advertisement (NA)
   accordingly.  The NS with the ARO option MUST be sent irrespective of
   the method used to generate the IID.  If the 6LN registers for a same
   compression context multiple addresses that are not based on
   Bluetooth device address, the header compression efficiency will
   decrease (see Section 3.2.3).

   2.  For sending Router Solicitations and processing Router
   Advertisements the Bluetooth LE 6LNs MUST, respectively, follow
   Sections 5.3 and 5.4 of the [RFC6775].

3.2.3.  Header compression

   Header compression as defined in RFC 6282 [RFC6282], which specifies
   the compression format for IPv6 datagrams on top of IEEE 802.15.4, is
   REQUIRED in this document as the basis for IPv6 header compression on
   top of Bluetooth LE.  All headers MUST be compressed according to RFC
   6282 [RFC6282] encoding formats.




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   The Bluetooth LE's star topology structure and ARO can be exploited
   in order to provide a mechanism for address compression.  The
   following text describes the principles of IPv6 address compression
   on top of Bluetooth LE.

   The ARO option requires use of EUI-64 identifier [RFC6775].  In the
   case of Bluetooth LE, the field SHALL be filled with the 48-bit
   device address used by the Bluetooth LE node converted into 64-bit
   Modified EUI-64 format [RFC4291].

   To enable efficient header compression, the 6LBR MUST include 6LoWPAN
   Context Option (6CO) [RFC6775] for all prefixes the 6LBR advertises
   in Router Advertisements for use in stateless address
   autoconfiguration.

   When a 6LN is sending a packet to or through a 6LBR, it MUST fully
   elide the source address if it is a link-local address.  A non-link-
   local source address 6LN has registered with ARO to the 6LBR for the
   indicated prefix MUST be fully elided if the source address is the
   latest address 6LN has registered for the indicated prefix.  If a
   source non-link-local address is not the latest registered, then the
   64-bits of the IID SHALL be fully carried in-line (SAC=01) or if the
   first 48-bits of the IID match with the latest registered address,
   then the last 16-bits of the IID SHALL be carried in-line (SAC=10).
   That is, if SAC=0 and SAM=11 the 6LN MUST be using the link-local
   IPv6 address derived from Bluetooth LE device address, and if SAC=1
   and SAM=11 the 6LN MUST have registered the source IPv6 address with
   the prefix related to compression context and the 6LN MUST be
   referring to the latest registered address related to compression
   context.  The IPv6 address MUST be considered to be registered only
   after the 6LBR has sent Neighbor Advertisement with ARO having status
   field set to success.  The destination IPv6 address MUST be fully
   elided if the destination address is 6LBR's link-local-address based
   on the 6LBR's Bluetooth device address (DAC=0, DAM=11).  The
   destination IPv6 address MUST be fully or partially elided if context
   has been set up for the destination address.  For example, DAC=0 and
   DAM=01 when destination prefix is link-local, and DAC=1 and DAM=01 if
   compression context has been configured for the used destination
   prefix.

   When a 6LBR is transmitting packets to 6LN, it MUST fully elide the
   source IID if the source IPv6 address is the link-local address based
   on 6LBR's Bluetooth device address (SAC=0, SAM=11), and it MUST elide
   the source prefix or address if a compression context related to the
   IPv6 source address has been set up.  The 6LBR also MUST fully elide
   the destination IPv6 address if it is the link-local-address based on
   6LN's Bluetooth device address (DAC=0, DAM=11), or if the destination
   address is the latest registered by the 6LN with ARO for the



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   indicated context (DAC=1, DAM=11).  If the destination address is a
   non-link-local address and not the latest registered, then 6LN MUST
   either include the IID part fully in-line (DAM=01) or, if the first
   48-bits of IID match to the latest registered address, then elide
   those 48-bits (DAM=10).

3.2.3.1.  Remote destination example

   When a 6LN transmits an IPv6 packet to a remote destination using
   global Unicast IPv6 addresses, if a context is defined for the 6LN's
   global IPv6 address, the 6LN has to indicate this context in the
   corresponding source fields of the compressed IPv6 header as per
   Section 3.1 of RFC 6282 [RFC6282], and has to elide the full IPv6
   source address previously registered with ARO (if using the latest
   registered address, otherwise full or part of IID may have to be
   transmitted in-line).  For this, the 6LN MUST use the following
   settings in the IPv6 compressed header: SAC=1 and SAM=11.  The CID
   may be set 0 or 1, depending which context is used.  In this case,
   the 6LBR can infer the elided IPv6 source address since 1) the 6LBR
   has previously assigned the prefix to the 6LNs; and 2) the 6LBR
   maintains a Neighbor Cache that relates the Device Address and the
   IID the device has registered with ARO.  If a context is defined for
   the IPv6 destination address, the 6LN has to also indicate this
   context in the corresponding destination fields of the compressed
   IPv6 header, and elide the prefix of or the full destination IPv6
   address.  For this, the 6LN MUST set the DAM field of the compressed
   IPv6 header as DAM=01 (if the context covers a 64-bit prefix) or as
   DAM=11 (if the context covers a full, 128-bit address).  DAC MUST be
   set to 1.  Note that when a context is defined for the IPv6
   destination address, the 6LBR can infer the elided destination prefix
   by using the context.

   When a 6LBR receives an IPv6 packet sent by a remote node outside the
   Bluetooth LE network, and the destination of the packet is a 6LN, if
   a context is defined for the prefix of the 6LN's global IPv6 address,
   the 6LBR has to indicate this context in the corresponding
   destination fields of the compressed IPv6 header.  The 6LBR has to
   elide the IPv6 destination address of the packet before forwarding
   it, if the IPv6 destination address is inferable by the 6LN.  For
   this, the 6LBR will set the DAM field of the IPv6 compressed header
   as DAM=11 (if the address is the latest 6LN has registered).  DAC
   needs to be set to 1.  If a context is defined for the IPv6 source
   address, the 6LBR needs to indicate this context in the source fields
   of the compressed IPv6 header, and elide that prefix as well.  For
   this, the 6LBR needs to set the SAM field of the IPv6 compressed
   header as SAM=01 (if the context covers a 64-bit prefix) or SAM=11
   (if the context covers a full, 128-bit address).  SAC is to be set to
   1.



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3.2.3.2.  Example of registration of multiple-addresses

   As described above, a 6LN can register multiple non-link-local
   addresses that map to a same compression context.  From the multiple
   address registered, only the latest address can be fully elided
   (SAM=11, DAM=11), and the IIDs of previously registered addresses
   have to be transmitted fully in-line (SAM=01, DAM=01) or in the best
   case can be partially elided (SAM=10, DAM=10).  This is illustred in
   an example below.

   1) A 6LN registers first address 2001:db8::1111:2222:3333:4444 to a
   6LBR.  At this point the address can be fully elided using SAC=1/
   SAM=11 or DAC=1/DAM=11.

   2) The 6LN registers second address 2001:db8::1111:2222:3333:5555 to
   the 6LBR.  As the second address is now the latest registered, it can
   be fully elided using SAC=1/SAM=11 or DAC=1/DAM=11.  The first
   address can now be partially elided using SAC=1/SAM=10 or DAC=1/
   DAM=10, as the first 112 bits of the address are the same between the
   first and the second registered addresses.

   3) Expiration of registration time for the first or the second
   address has no impact on the compression.  Hence even if secondly
   registered address expires, the first address can only be partially
   elided (SAC=1/SAM=10, DAC=1/DAM=10).  The 6LN can register a new
   address, or re-register an expired address, to become able to again
   fully elide an address.

3.2.4.  Unicast and Multicast address mapping

   The Bluetooth LE link layer does not support multicast.  Hence
   traffic is always unicast between two Bluetooth LE nodes.  Even in
   the case where a 6LBR is attached to multiple 6LNs, the 6LBR cannot
   do a multicast to all the connected 6LNs.  If the 6LBR needs to send
   a multicast packet to all its 6LNs, it has to replicate the packet
   and unicast it on each link.  However, this may not be energy-
   efficient and particular care must be taken if the master is battery-
   powered.  In the opposite direction, a 6LN always has to send packets
   to or through 6LBR.  Hence, when a 6LN needs to transmit an IPv6
   multicast packet, the 6LN will unicast the corresponding Bluetooth LE
   packet to the 6LBR.

3.3.  Subnets and Internet connectivity scenarios

   In a typical scenario, the Bluetooth LE network is connected to the
   Internet as shown in the Figure 6.  In this scenario, the Bluetooth
   LE star is deployed as one subnet, using one /64 IPv6 prefix, with




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   each spoke representing individual link.  The 6LBR is acting as
   router and forwarding packets between 6LNs and to and from Internet.

                                             /
            .---------------.               /
           /           6LN   \             /
          /               \   \           /
         |                 \   |         /
         | 6LN -----------   6LBR ----- |  Internet
         |     <--Link-->  /   |         \
          \               /   /           \
           \           6LN   /             \
            '---------------'               \
                                             \

          <------ Subnet -----><-- IPv6 connection -->
                                      to Internet


         Figure 6: Bluetooth LE network connected to the Internet

   In some scenarios, the Bluetooth LE network may transiently or
   permanently be an isolated network as shown in the Figure 7.  In this
   case the whole star consist of a single subnet with multiple links,
   where 6LBR is at central routing packets between 6LNs.


                    .-------------------.
                   /                     \
                  /     6LN      6LN      \
                 /        \      /         \
                |          \    /           |
                |   6LN --- 6LBR --- 6LN    |
                |          /    \           |
                 \        /      \         /
                  \     6LN      6LN      /
                   \                     /
                    '-------------------'
                <--------- Subnet ---------->

                  Figure 7: Isolated Bluetooth LE network

   It is also possible to have point-to-point connection between two
   6LNs, one of which being central and another being peripheral.
   Similarly, it is possible to have point-to-point connections between
   two 6LBRs, one of which being central and another being peripheral.





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   At this point in time mesh networking with Bluetooth LE is not
   specified.

4.  IANA Considerations

   There are no IANA considerations related to this document.

5.  Security Considerations

   The transmission of IPv6 over Bluetooth LE links has similar
   requirements and concerns for security as for IEEE 802.15.4.
   Bluetooth LE Link Layer security considerations are covered by the
   IPSP [IPSP].

   Bluetooth LE Link Layer supports encryption and authentication by
   using the Counter with CBC-MAC (CCM) mechanism [RFC3610] 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 them when they are
   used.)

   Key management in Bluetooth LE is provided by the Security Manager
   Protocol (SMP), as defined in [BTCorev4.1].

   The IPv6 link-local address configuration described in Section 3.2.1
   strictly binds the privacy level of IPv6 link-local address to the
   privacy level device has selected for the Bluetooth LE.  This means
   that a device using Bluetooth privacy features will retain the same
   level of privacy with generated IPv6 link-local addresses.
   Respectively, device not using privacy at Bluetooth level will not
   have privacy at IPv6 link-local address either.  For non-link local
   addresses implementations have a choice to support, for example,
   [I-D.ietf-6man-default-iids], [RFC3972], [RFC4941] or [RFC5535].

6.  Additional contributors

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

7.  Acknowledgements

   The Bluetooth, Bluetooth Smart and Bluetooth Smart Ready marks are
   registred trademarks owned by Bluetooth SIG, Inc.

   Samita Chakrabarti, Brian Haberman, Marcel De Kogel, Jouni Korhonen,
   Erik Nordmark, Erik Rivard, Dave Thaler, Pascal Thubert, and Victor
   Zhodzishsky have provided valuable feedback for this draft.



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   Authors would like to give special acknowledgements for Krishna
   Shingala, Frank Berntsen, and Bluetooth SIG's Internet Working Group
   for providing significant feedback and improvement proposals for this
   document.

8.  References

8.1.  Normative References

   [BTCorev4.1]
              Bluetooth Special Interest Group, "Bluetooth Core
              Specification Version 4.1", December 2013.

   [IPSP]     Bluetooth Special Interest Group, "Bluetooth Internet
              Protocol Support Profile Specification Version 1.0.0",
              December 2014.

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

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

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

   [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.

   [RFC7136]  Carpenter, B. and S. Jiang, "Significance of IPv6
              Interface Identifiers", RFC 7136, February 2014.

8.2.  Informative References








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   [I-D.ietf-6man-default-iids]
              Gont, F., Cooper, A., Thaler, D., and S. LIU,
              "Recommendation on Stable IPv6 Interface Identifiers",
              draft-ietf-6man-default-iids-03 (work in progress), May
              2015.

   [IEEE802-2001]
              Institute of Electrical and Electronics Engineers (IEEE),
              "IEEE 802-2001 Standard for Local and Metropolitan Area
              Networks: Overview and Architecture", 2002.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

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

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

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

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, 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.

   [RFC5535]  Bagnulo, M., "Hash-Based Addresses (HBA)", RFC 5535, June
              2009.

Authors' Addresses

   Johanna Nieminen
   Nokia

   Email: johannamaria.nieminen@gmail.com






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   Teemu Savolainen
   Nokia
   Visiokatu 3
   Tampere  33720
   Finland

   Email: teemu.savolainen@nokia.com


   Markus Isomaki
   Nokia
   Otaniementie 19
   Espoo  02150
   Finland

   Email: markus.isomaki@nokia.com


   Basavaraj Patil
   AT&T
   1410 E. Renner Road
   Richardson, TX  75082
   USA

   Email: basavaraj.patil@att.com


   Zach Shelby
   Arm
   Hallituskatu 13-17D
   Oulu  90100
   Finland

   Email: zach.shelby@arm.com


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

   Email: carlesgo@entel.upc.edu








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