Atmel AVR2070 - Manual (Page 59)

AVR2070
59
8240B-AVR-06/09
Appendix C - IPv6 / 6LoWPAN Background
Using IPv6 and 6LowPAN will be easier if an understanding of the underlying
technologies is in place. This section assumes familiarity with the RUM network
outlined in Appendix A.
C.1 The problem with RF-Only Networks
Atmel® provides the RUM network layer as a very easy method of passing messages
around the wireless network. Problems occur when messages need to be passed
outside the wireless network. Any wireless protocol designed specifically for the
802.15.4 radios (RUM included) will have poor support outside the physical wireless
network. This means passing messages outside the physical radio network requires
either specialized software on connected computers, or translating the RF protocol to
some well-known network protocol.
C.2 Why IP?
IP is used in the biggest computer networks in existence, proving its ability to scale
across global networks. IP is already supported by almost every desktop computer,
meaning that accessing a sensor network using IP would require no specialized tools.
Setting up a wireless sensor network could be managed by the IT department of a
company where no special knowledge outside of normal network setup is needed.
Since IP is such a general-purpose protocol, it is not optimized for low-cost, low-
power nodes. At first glance it would seem crazy to attempt to use such a versatile
high-power protocol for tiny sensor nodes. However IP is very flexible, and many of
the benefits of IP can be obtained with a minimum of resources required.
C.3 6LoWPAN to the Rescue
6LoWPAN is a working group at the Internet Engineering Task Force (IETF), which
has a number of RFC’s documenting a method of transmitting IPv6 across Low
power Wireless Personal Area Networks.
6LoWPAN specifies how the IP packets can be passed across the 802.15.4 links.
This includes how to compress IP headers to eliminate redundant information,
fragmentation to pass messages larger than a single 802.15.4 frame, and how to
guarantee interoperability between this low-power IPv6 network and the greater
internet.
A huge advantage of 6LoWPAN is that nodes from different vendors, running at
different radio frequencies or on different channels, can all be interconnected through
an IPv6 link.
C.4 A Crash Course in IPv6
An understanding of IPv6, and how it differs from IPv4 is needed to run this demo. A
quick overview is given here in order to educate a user with this new version of the
Internet Protocol.
C.4.1 IPv6 Addressing
IPv6 addresses are 128-bits long, and are written in hexadecimal notation. A typical
IPv6 address written out might look like:
2001:0DB8:0000:0000:0008:0800:200C:417A