The Internet has been a great success over the past 20 years, growing from a small academic network into a global, ubiquitous network used regularly by over 1.4 billion people. It was the power of the Internet paradigm, tying heterogeneous networks together, and the innovative World Wide Web (WWW) model of uniform resource locators (URLs), the hypertext transfer protocol (HTTP) and universal content markup with the hypertext markup language (HTML) that made this possible.
Grass-roots innovation has however been the most powerful driver behind the Internet success story. The Internet is open to innovation like no other telecommunication system before it. This has allowed all groups involved, from Internet architects to communication engineers, IT staff and everyday users to innovate, quickly adding new protocols, services and uses for Internet technology.
As the Internet of routers, servers and personal computers has been maturing, another Internet revolution has been going on – The Internet of Things. The vision behind the Internet of Things is that embedded devices, also called smart objects, are universally becoming IP enabled, and an integral part of the Internet. Examples of embedded devices and systems using IP today range from mobile phones, personal health devices and home automation, to industrial automation, smart metering and environmental monitoring systems.
The scale of the Internet of Things is already estimated to be immense, with the potential of trillions of devices becoming IP-enabled. The impact of the Internet of Things will be significant, with the promise of better environmental monitoring, energy savings, smart grids, more efficient factories, better logistics, better healthcare and smart homes.
The Internet of Things revolution started in the 1990s with industrial automation systems. Early proprietary networks in industrial automation were quickly replaced by different forms of industrial Ethernet, and Internet protocols became widely used between embedded automation devices and back-end systems. This trend has continued in all other automation segments, with Ethernet and IP becoming ubiquitous.
Machine-to-machine (M2M) telemetry made a breakthrough already in the early 2000s, with the use of cellular modems and IP to monitor and control a wide range of equipment from vending machines to water pumps. Building automation systems have gone from legacy control to making wide use of wired IP communications through the Building Automation and Control Network (BACnet) and Open Building Information Exchange (oBIX) standards.
More recently, automatic metering infrastructures and smart grids are being deployed at a rapid rate, largely depending on the scalability and universal availability of IP technology. Finally, mobile phones have become almost universally IP-enabled embedded devices currently making up the largest body of devices belonging to the Internet of Things.
An equally important development has been happening in the services that are used to monitor and control embedded devices. Today these services are almost universally built on Internet technology, and more commonly are implemented using web-based services. Web Service technologies have completely changed the way business and enterprise applications are designed and deployed. It is this combination of Internet-connected embedded devices and Web-based services which makes the Internet of Things a powerful paradigm.
Hundreds of millions of embedded devices are already IP-enabled, but the Internet of Things is still in its infancy in 2009. Although the capabilities of processor, power and communications technology have continuously increased, so has the complexity of communications standards, protocols and services. Thus, so far, it has been possible to use Internet capabilities in only the most powerful embedded devices. Additionally, lowpower wireless communications limits the practical bandwidth and duty-cycle available. Throughout the 1990s and early 2000s we have seen a large array of proprietary low-power embedded wireless radio and networking technologies. This has fragmented the market and slowed down the deployment of such technology.
The Institute of Electrical and Electronics Engineers (IEEE) released the 802.15.4 low-power wireless personal area network (WPAN) standard in 2003, which was a major milestone, providing the first global low-power radio standard. Soon after, the ZigBee Alliance developed a solution for ad hoc control networks over IEEE 802.15.4, and has produced a lot of publicity about the applications of wireless embedded technology.
ZigBee and proprietary networking solutions that are vertically bound to a link-layer and application profiles only solve a small portion of the applications for wireless embedded networking. They also have problems with scalability, evolvability and Internet integration. A new paradigm was needed to enable low-power wireless devices with limited processing capabilities (see Figure 1.1) to participate in the Internet of Things, forming what we call the Wireless Embedded Internet.
Figure 1.1 Wireless embedded 6LoWPAN device.
This book introduces a set of Internet standards which enable the use of IPv6 over lowpower wireless area networks (6LoWPAN)1, which is the key to realizing the Wireless Embedded Internet. 6LoWPAN breaks down the barriers to using IPv6 in low-power, processing-limited embedded devices over low-bandwidth wireless networks. IPv6, which is the newest version of the Internet Protocol, was developed in the late 1990s as a solution to the rapid growth and challenges facing the Internet. The further growth of the Internet of Things will be made possible thanks to IPv6.
In this chapter we give an overview of 6LoWPAN. First the Internet of Things is introduced, followed by the ideas behind 6LoWPAN, IETF standardization, related trends and applications of 6LoWPAN technology in Section 1.1. The overall 6LoWPAN architecture is then introduced in Section 1.2. A comprehensive overview of 6LoWPAN basic mechanisms and the link-layer are given in Section 1.3, followed by a 6LoWPAN network example in Section 1.4.
1The 6LoWPAN acronym has been redefined on purpose in this book, as “Personal” is no longer relevant to the technology. WPAN originally referred to IEEE 802.15.4 Wireless Personal Area Network.