In the Internet a packet passes through many different interconnected networks on its way from source to destination. Thus, considering the link layer technology of each traversed network, there is need of an ``IP-over-X'' specification (i.e., of an adaptation layer) to define how to transport IP packets. Following this need, in the process of shaping the IoT world, the IETF IPv6 over Low power WPAN (6LoWPAN) working group [6LoWPAN WG] started in 2007 to work on specifications for transmitting IPv6 over IEEE 802.15.4 networks [IEEE802.15.4].
Typically, Low power WPANs are characterized by: small packet sizes, support for addresses with different lengths, low bandwidth, star and mesh topologies, battery supplied devices, low cost, large number of devices, unknown node positions, high unreliability, and long idle periods during when communications interfaces are turned off to save energy.
Given the aforementioned features, it is clear that the adoption of IPv6 on top of a Low power WPAN is not straightforward, but poses strong requirements for the optimization of this adaptation layer. For instance, due to the IPv6 default minimum MTU size (i.e., 1280 bytes), a no-fragmented IPv6 packet would be too large to fit in an IEEE 802.15.4 frame. Moreover, the overhead due to the 40 bytes long IPv6 header would waste the scarce bandwidth available at the PHY layer.
For these reasons, the 6LoWPAN working group has devoted huge efforts for defining an effective adaptation layer in [rfc4944,6lowpanhc]. Further issues encompass the auto-configuration of IPv6 addresses [rfc2464], the compliance with the recommendation on supporting link-layer subnet broadcast in shared networks [rfc3819], the reduction of routing and management overhead, the adoption of lightweight application protocols (or novel data encoding techniques), and the support for security mechanisms (i.e., confidentiality and integrity protection, device bootstrapping, key establishment and management).
[IEEE802.15.4] IEEE std. 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks(LR-WPANs), Standard for Information Technology Std., 2011.
[rfc4944] G. Montenegro, N. Kushalnagar, J. Hui, and D. Culler, Transmission of IPv6 Packets over IEEE 802.15.4 Networks, RFC 4944, Internet Engineering Task Force RFC 4944, September 2007. - Updated by: 6282, 6775
[6lowpanhc] J. Hui and P. Thubert, Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks, RFC 6282, Internet Engineering Task Force RFC 6282, September 2011.
[rfc2464] M. Crawford, Transmission of IPv6 Packets over Ethernet Networks, RFC 2464, Internet Engineering Task Force RFC 2464, December 1998. - Updated by: 6085
[rfc3819] P. Karn, C. Bormann, G. Fairhurst, D. Grossman, R. Ludwig, J.Mahdavi, G. Montenegro, J. Touch, and L. Wood, Advice for Internet Subnetwork Designers, RFC 3819, Internet Engineering Task Force RFC 3819, July 2004.
[6LoWPAN book] Z. Shelby and C. Bormann, 6LoWPAN: The Wireless Embedded Internet, ser. Wiley Series on Communications Networking & Distributed Systems. John Wiley & Sons, 2010.