During IETF 90, the 6TiSCH, 6lo, and ROLL working groups (WGs) hosted the Low-power Lossy Networks (LLN) Plugfest—an event designed to bring together IETF participants interested in gaining hands-on experience with Internet of Things (IoT) technology. Eight teams presented implementations of Request for Comments (RFCs), Internet Drafts (I-Ds), tools, and hardware related to technology standardized by the 6TiSCH, 6lo and ROLL WGs. The focus of the implementations was on IEEE802.15.4e Timeslotted Channel Hopping (TSCH), the 6TiSCH architecture, IPv6 over Low-power Wireless Personal Area Networks (6LoWPAN)1, and Routing Protocol for Low-Power and Lossy Networks (RPL)2. This article explains the technical challenges and outcomes of the event, the importance of running code, and the federating role of such events across IoT-related WGs.
Several WGs design solutions for wireless networks of constrained devices, also known as low-power and lossy networks, the cornerstone of the Internet of Things.
- The 6lo (WPAN) WGs has standardized an adaptation layer to efficiently carry (long) IPv6 packets over (short) IEEE802.15.4 frames, and other link-layer technologies.
- The ROLL WG has defined the RPL routing protocol, which enables multihop topologies in those constrained networks.
- The 6TiSCH WG is chartered to enable an IPv6-based upper-stack to run on top of the IEEE802.15.4 TSCH link layer. TSCH technology, widely deployed in low-power wireless industrial monitoring solutions, enables ultra-low power and high reliability, and introduces determinism to LLNs.
- Other groups in the LLN space include the CoRE, ACE, DICE, and LWIG WGs.
Each of the aforementioned WGs focuses on a subset of the IoT. For this reason, it is important that we also keep the big picture in mind, that we continuously integrate RFCs and I-Ds from these WGs into one working network to enable the flagging of potential conflicts or missing work. To that end, the 6TiSCH, 6lo, and ROLL WGs cohosted Plugfest3 at IETF 90, cochaired by Xavier Vilajosana from the Universitat Oberta de Catalunya and Ines Robles from LMF Ericsson.
Pascal Thubert from Cisco Systems4 and Thomas Watteyne from Linear Technology5 presented a joint implementation of the multi-LLN architecture defined by the 6TiSCH WG. They interconnected two SmartMesh IP wireless networks through two Cisco i3000 industrial switches. Linear Technology’s SmartMesh IP is a commercial product which implements 6LoWPAN and IEEE802.15.4e TSCH, and uses techniques similar to the ones being standardized by 6TiSCH. The Cisco switches play the role of 6LoWPAN Backbone Router6, federating the two independent SmartMesh IP wireless networks under a single IPv6 prefix.
The University of California, Berkeley’s OpenWSN7 project is an open-source implementation of the protocol stack standardized by the 6TiSCH WG, ported on a variety of hardware and software platforms. Nicola Accettura (University of California, Berkeley), Pere Tuset and Xavier Vilajosana (Universitat Oberta de Catalunya), Qin Wang and Tengfei Chang (University of Science and Technology Beijing), Marcelo Barros and Vitor Garbellini (Universidade Federal de Uberlândia), and Thomas Watteyne (OpenWSN project coordinator) showed a 10-mote network of OpenMote devices implementing the latest I-Ds developed by the 6TiSCH WG.8,9,10,11 The demonstration consisted of a Constrained Application Protocol (CoAP) client triggering the reservation of link-layer cells along a multihop route.
OpenMote12 is a startup company that provides an ecosystem of hardware for the Internet of Things. At its core is the OpenMote, a fully programmable and easy-to-use IEEE802.15.4-embedded communication platform. Multiple open-source implementations, including OpenWSN, fully support the OpenMote. Cofounders Pere Tuset and Xavier Vilajosana demonstrated how an OpenMote can be turned into a wireless packet-capture device for Wireshark, and discussed ongoing work supporting the FreeRTOS operating system in tickless mode.
Cedric Adjih from Inria gave a live demonstration of FIT-IoT’s IoT-LAB13 testbed. This open testbed comprises 2,728 wireless devices deployed on six sites across France. A RESTful web interface enables a user to remotely reserve a number of devices, reprogram them with custom firmware, and monitor their activity. Several open-source implementations, including OpenWSN and RIOT14, can be used on the IoT-LAB platforms.
Oliver Hahm (Inria) and Thomas Eichinger (FU Berlin) presented RIOT, the friendly operating system for the IoT. They gave a live demonstration of the RIOT operating system running the protocol stack from the OpenWSN project on the IoT-LAB_M3 board.
Jürgen Schönwälder (Jacobs University Bremen) demonstrated an implementation of the 6loWPAN-MIB15 in Contiki, running on the AVR Raven. This I-D defines a set of counters for monitoring the behavior of a 6LoWPAN stack implementation for packets, errors, compression, fragmentation parameters, etc. The demonstration involved retrieving those counters both through Simple Network Management Protocol (SNMP) and CoAP on 6lo16 devices.
Vincent Ladeveze17 is developing Wireshark dissectors for IEEE802.15.4e TSCH and other I-Ds from the 6TiSCH WG. He is building a 16-channel IEEE802.15.4 sniffer by connecting 16 devices running custom OpenWSN firmware to a computer on which there is software that aggregates these streams of captured packets and forwards them to Wireshark. The ability to simultaneously sniff 16 IEEE802.15.4 frequencies is necessary for debugging channel hopping solutions, such as IEEE802.15.4e TSCH.
Nestor Tiglao (University of the Philippines) presented Sewio’s open sniffer solution, in which multiple wireless devices can be scattered around an area and report, through the Ethernet subnet, the different wireless packets they have captured to a single Wireshark instance. This enables the debugging of wireless networks that are geographically spread apart.
The success of the IETF 90 LLN Plugfest underscores the importance of running code early in the standardization process. In the case of ongoing standardization work in the 6TiSCH WG, having implementations running when the documents are still at the I-D stage enables both verification of what is being proposed and iterative improvement and reconsideration of decisions taken to improve the quality of the documents being produced. Because the ability to formally acknowledge implementations increases the quality of the produced I-Ds or RFCs, we support efforts that do so, such as the CodeMatch outreach program.
Moreover, in the LLN standardization space, multiple WGs are focused on a subset of the standardization space. The Plugfest reinforced the importance of continuously integrating the I-Ds and RFCs produced by different WGs, and verified that this kind of integration is a complete and conflict-free solution. It also suggests that the IETF considers creating a body that oversees the IoT-related WGs to flag potential conflicts early-on in the standardization process, probably well before implementers could.
We thank WG Chairs Michael Richardson, Pascal Thubert, Samita Chakrabarti, and Ulrich Herberg for hosting the event; IETF Chair Jari Arkko and Area Directors Adrian Farrel, Alia Atlas, and Ted Lemon for making the event possible; Stephanie McCammon for helping to organize the event; and particularly acknowledge the teams who participated in the Plugfest, whose sleepless nights made the event a great success.
- “Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks” [RFC 6282]
- “RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks” [RFC 6550]
- Guidelines and additional details are available at https://bitbucket.org/6tisch/meetings/wiki/140720a_ietf90_toronto_plugfest
- http:// www.linear.com/dust
- 6LoWPAN Backbone Router [draft-thubert-6lowpan-backbone-router-03, work-in-progress]
- Minimal 6TiSCH Configuration [draft-ietf-6tisch-minimal-02, work-in-progress]
- 6TiSCH Operation Sublayer (6top) [draft-wang-6tisch-6top-sublayer-01, work-in-progress]
- 6TiSCH On-the-Fly Scheduling [draft-dujovne-6tisch-on-the-fly-03, work-in-progress]
- The IPv6 Flow Label within a RPL domain [draft-thubert-6man-flow-label-for-rpl-03, work-in-progress]
- Definition of Managed Objects for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) [draft-ietf-6lo-6lowpan-mib-01, work-in-progress]
- A 6lo stack is based on 6LoWPAN (RFC 4944, RFC 6282, RFC 6775) supporting different Link-layers
- Presented by Thomas Watteyne, on behalf of Vincent Ladeveze.