83 IEEE Network • November/December 2014 0890-8044/14/$25.00 © 2014 IEEE he Internet has grown exponentially over the last three decades and has expanded into almost every aspect of daily life. The next wave of Internet expan- sion is expected to be the networking of sensors, actuators, and appliances, which rather than interacting with humans, measure and react to physical properties such as temperature, power consumption, or heart rate. This type of networking is referred to as the Internet of Things (IoT). In the IoT vision, “Things” use the Internet Protocol (IP) and are counted in tens of billions. IPv6 is well suited for the IoT given its vast address space and autoconfiguration capabili- ties [1]. A plethora of low-power radio technologies suitable for IoT already exist, including Bluetooth Low Energy (Bluetooth LE), IEEE 802.15.4, Z-Wave, ANT, Dash7, Wave2M, and low power variants of IEEE 802.11 [2]. Some of them already sup- port IP, including 6LoWPAN, which defines how to run IPv6 over 802.15.4, and 802.11. The low-power radio technology with perhaps the highest potential for IoT use that is still missing IP capability is Bluetooth LE, which is projected to be incorporat- ed in billions of consumer electronics devices (e.g. smart- phones, tablets, Google glass, etc.). Accordingly, the capability to run IPv6 over Bluetooth LE opens new doors to the IoT and leverages Bluetooth LE toward new application areas. Among these, an outstanding use case is exploiting the smartphone as a gateway for providing Internet connectivity to surrounding Bluetooth LE-enabled sensors. For instance, this approach makes it possible to remotely and ubiquitously monitor medical parameters from body sensors. In another example application, vehicle health messages can be sent by vehicular sensors through the smartphone of the driver to remote Intelligent Transportation System (ITS) control centers in order to pre- vent accidents. Similar applications can be found in other domains including home, urban, and industrial automation. Furthermore, enabling IPv6 over Bluetooth LE contributes to interoperability between IoT devices that utilize different low- power radio technologies. This is particularly important since the Internet Engineering Task Force (IETF) standardization work is currently progressing toward extending the family of low-power technologies with IPv6 support [3]. This paradigm is the key to a dramatic increase of IoT capilarity and to allowing generic IoT application development (i.e. avoiding the need to take into account specific features of different link and physical layer technologies). Using Bluetooth LE for Internet connectivity and applica- tions poses challenges beyond IPv6 packet transport, including gateway operation, application protocol efficiency, and securi- ty. In this article we present a holistic solution for integrating Bluetooth LE devices with the IoT. A central piece of this solution is the IPv6 over Bluetooth LE specification that is currently being produced by the IETF [4] and is expected to become a standard in the near future. However, the specifica- tion is targeted to implementers, and therefore neither moti- vates the related design choices nor is written in a style comprehensible to readers outside the specialty. On the other hand, this article focuses on the whole protocol stack, high- lighting aspects from all layers that are crucial to understand the capabilities and performance trade-offs of the solution. The rest of this article is structured as follows. The follow- ing section reviews Bluetooth LE. The third section describes 6LoWPAN and our proposal for enabling IPv6 over Blue- T Abstract The next wave driving the expansion of the Internet will come from the Internet of Things. Bluetooth LE is a rapidly emerging ultra-low-power radio technology expect- ed to be incorporated in billions of IoT devices in the next few years. Consequently, it is particularly important to specify Internet connectivity solutions for Bluetooth LE. In this article we present such solutions based on the ongoing standardization work in the IETF and Bluetooth Special Interest Group. We prove the feasibility of a complete IP-based protocol stack on constrained devices and illustrate its perfor- mance, highlighting key trade-offs. In addition, we discuss gateway operation cov- ering global IPv6 connectivity and proxy-cache functionality. Networking Solutions for Connecting Bluetooth Low Energy Enabled Machines to the Internet of Things Johanna Nieminen, Carles Gomez, Markus Isomaki, Teemu Savolainen, Basavaraj Patil, Zach Shelby, Minjun Xi, and Joaquim Oller T Johanna Nieminen is with TeliaSonera. Carles Gomez and Joaquim Oller are with Universitat Politècnica de Catalunya/Fundació i2CAT. Markus Isomaki, Teemu Savolainen, and Minjun Xi are with Nokia. Basavaraj Patil is with AT&T Mobility. Zach Shelby is with ARM.