6LoWPAN: The wireless embedded Internet - Part 4: Addressing, etc. & a network example

[Part 1 reviews the concept of the Internet of Things - and its subset, the wireless embedded Internet - and answers the question "Why 6LoWPAN?" Part 2 discusses 6LoWPAN's history and standardization, its relation to other trends like ZigBee and wireless sensor networks, and some application examples. Part 3 reviews the 6LoWPAN architecture, and then examines its protocol stack and three link-layer technologies used with 6LoWPAN.]

1.3.3 Addressing
IP addressing with 6LoWPAN works just like in any IPv6 network, and is similar to addressing over Ethernet networks as defined by [RFC2464]. IPv6 addresses are typically formed automatically from the prefix of the LoWPAN and the link-layer address of the wireless interfaces. The difference in a LoWPAN is with the way low-power wireless technologies support link-layer addressing; a direct mapping between the link-layer address and the IPv6 address is used for achieving compression. This will be explained in Section 1.3.4.

Low-power wireless radio links typically make use of flat link-layer addressing for all devices, and support both unique long addresses (e.g. EUI-64) and configurable short addresses (usually 8–16 bits in length). The IEEE 802.15.4 standard, for example, supports unique EUI-64 addresses carried in all radio chips, along with configurable 16-bit short addresses. These networks by nature also support broadcast (address 0xFFFF in IEEE 802.15.4), but do not support native multicast.

IPv6 addresses are 128 bits in length, and (in the cases relevant here) consist of a 64-bit prefix part and a 64-bit interface identifier (IID) [RFC4291]. Stateless address autoconfiguration (SAA) [RFC4862] is used to form the IPv6 interface identifier from the link-layer address of the wireless interface as per [RFC4944]. For simplicity and compression, 6LoWPAN networks assume that the IID has a direct mapping to the link layer address, therefore avoiding the need for address resolution. The IPv6 prefix is acquired through Neighbor Discovery Router Advertisement (RA) messages [ID-6lowpan-nd] as on a normal IPv6 link.

The construction of IPv6 addresses in 6LoWPAN from known prefix information and known link-layer addresses, is what allows a high header compression ratio. 6LoWPAN addressing is discussed in detail in Chapter 2. A reference for IPv6, including the IPv6 addressing model, is provided in Appendix A.