Contiki is an open source operating system for the Internet of Things. It connects tiny low-cost, low-power microcontrollers to the Internet and provides powerful low-power Internet communication. Contiki supports fully standard IPv6 and IPv4, along with the recent low-power wireless standards: 6lowpan, RPL, CoAP.
The Contiki port for ARC is available from the embARC web site at http://www.embarc.org