LLNS

Low-Power and Lossy Networks (LLNs) refer to networks composed of inexpensive, resource-constrained devices that rely on links with limited reliability and capacity. These networks are designed to operate for long periods on small batteries or energy harvesting, with constrained CPU, memory, and radio capabilities. LLNs typically feature low data rates, frequent intermittent connectivity, and variable latency, yet they aim to deliver reliable communication through multi-hop routing and efficient protocol design. They are widely used in Internet of Things applications, including sensor networks, building automation, and industrial monitoring.

Topology and devices. LLNs may include end devices that generate data, routers or forwarders that relay packets, and gateways that connect the LLN to broader networks. Because links are lossy and devices energy-limited, LLNs rely on energy-aware routing and opportunistic communication strategies. Common topologies include mesh and tree-like structures, with multi-hop routes spanning large areas while attempting to balance energy consumption.

Standards and protocols. LLNs are standardized around technologies that support IPv6 in constrained networks, such as 6LoWPAN, which compresses IPv6 headers for low-power links. Routing is often handled by RPL (Routing Protocol for LLNs), which builds a destination-oriented rooted acyclic graph. Other related technologies include IEEE 802.15.4 as the physical and MAC layer, Thread and Zigbee IP as upper-layer implementations, and the time-slotted approach of 6TiSCH in some deployments.

Applications and challenges. LLNs enable sensing and actuation in smart buildings, agriculture, and industrial environments. Challenges include energy management, reliability over lossy links, device discovery, scalable routing, and security constrained by device limits. Proper commissioning, firmware updates, authentication, and encryption are critical to maintaining integrity in LLNs.