Thread/OpenThread: A Compromise in Low-Power Wireless Multihop Network Architecture for the Internet of Things

Hyung-Sin Kim Networks

Extending an Internet subnet by connecting resource-constrained nodes (e.g., embedded sensors and actuators) over multiple wireless hops is necessary to support the future Internet of Things (IoT). RPL, the IPv6 routing standard for low-power and lossy networks, tried to achieve this goal but has not seen wide adoption in practice. As an alternative, Thread is a recently standardized low-power network protocol for IoT, driven by the Thread group, an industry consortium led by Google/Nest. We provide a comparative analysis of the technical aspects of RPL and Thread based on their specifications, explaining why using Thread, as opposed to RPL, may make sense for the future Internet. Specifically, the fundamental differences between RPL and Thread are their respective scopes and multihop more…

Authors: Hyung-Sin Kim, Sam Kumar, David Culler

ALICE: Autonomous Link-based Cell Scheduling for TSCH

Hyung-Sin Kim Networks

Although low-power lossy network (LLN), at its early stage, commonly used asynchronous link layer protocols for simple operation on resource-constrained nodes, development of embedded hardware and time synchronization technologies made Time-Slotted Channel Hopping (TSCH) viable in LLN (now part of IEEE 802.15.4e standard). TSCH has the potential to be a link layer solution for LLN due to its resilience to wireless interference (e.g., WiFi) and multipath fading. However, its slotted operation incurs non-trivial cell scheduling overhead: two nodes should wake up at a time-frequency cell together to exchange a packet. Efficient cell scheduling in dynamic multihop topology in wireless environments has been an open issue, preventing TSCH’s wide adoption in practice. This work introduces ALICE, a novel autonomous link-based cell more…

Authors: Seohyang Kim, Hyung-Sin Kim, Chongkwon Kim

System Architecture Directions for Post-SoC/32-bit Networked Sensors

Hyung-Sin Kim Networks, Systems

The emergence of low-power 32-bit Systems-on-Chip (SoCs), which integrate a 32-bit MCU, radio, and flash, presents an opportunity to re-examine design points and trade-offs at all levels of the system architecture of networked sensors. To this end, we develop a post-SoC/32-bit design point called Hamilton, showing that using integrated components enables a ∼$7 core and shifts hardware modularity to design time. We study the interaction between hardware and embedded OSes, identifying that (1) post-SoC motes provide lower idle current (5.9 µA) than traditional 16-bit motes, (2) 32-bit MCUs are a major energy consumer (e.g., tick increases idle current >50 times), comparable to radios, and (3) thread-based concurrency is viable, requiring only 8.3 µs of context switch time. We design a more…

Authors: Hyung-Sin Kim, Michael Andersen, Kaifei Chen, Sam Kumar, William J. Zhao, Kevin Ma, David Culler

Do Not Lose Bandwidth: Adaptive Transmission Power and Multihop Topology Control

Hyung-Sin Kim Networks

We show that a multihop wireless network can achieve better bandwidth and routing stability when transmission power and routing topology are jointly and adaptively controlled. Our experiments show that the predominant ‘fixed and uniform’ transmission power strategy with ‘link quality and hop distance’-based routing topology construction loses significant bandwidth due to hidden terminal and load imbalance problems. We design an adaptive and distributed control mechanism for transmission power and routing topology, PC-RPL, within the standard RPL routing protocol. We implement PC-RPL on real embedded devices and evaluate its performance on a 49-node multihop testbed. PC-RPL reduces total end-to-end packet losses ~7-fold without increasing hop distance compared to RPL with the highest transmission power at heavy load, resulting in 17% improvement in aggregate bandwidth and 64% for the worst-case node.

Authors: Hyung-Sin Kim, Jeongyeup Paek, David Culler, Saewoong Bahk

Challenging the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL): A Survey

Hyung-Sin Kim Networks

RPL is the IPv6 routing protocol for low-power and lossy networks, standardized by IETF in 2012 as RFC6550. Specifically, RPL is designed to be a simple and inter-operable networking protocol for resource-constrained devices in industrial, home, and urban environments, intended to support the vision of the Internet of Things with thousands of devices interconnected through multihop mesh networks. More than four-years have passed since the standardization of RPL, and we believe that it is time to examine and understand its current state. In this paper, we review the history of research efforts in RPL; what aspects have been (and have not been) investigated and evaluated, how they have been studied, what was (and was not) implemented, and what remains for more…

Authors: Hyung-Sin Kim, Jeonggil Ko, David Culler, Jeongyeup Paek

SafeBricks: Shielding Network Functions in the Cloud

Rishabh Poddar Networks, Security, Systems

With the advent of network function virtualization (NFV), outsourcing network processing to the cloud is growing in popularity amongst enterprises and organizations. Such outsourcing, however, poses a threat to the security of the client’s traffic because the cloud is notoriously susceptible to attacks. We present SafeBricks, a system that shields generic network functions (NFs) from an untrusted cloud. SafeBricks ensures that only encrypted traffic is exposed to the cloud provider, and preserves the integrity of both traffic and the NFs. At the same time, it enables clients to reduce their trust in NF implementations by enforcing least privilege across NFs deployed in a chain. SafeBricks does not require changes to TLS, and safeguards the interests of NF vendors as well more…

Authors: Rishabh Poddar, Chang Lan, Raluca Ada Popa, Sylvia Ratnasamy