IoT Network Topologies and Protocols

• Core principle of IoT is connecting physical devices to the internet to enable communication between users and devices.
• Constrained devices face physical limitations such as energy, size, and memory footprint.
• IoT developers must implement protocols to enable connectivity for constrained devices.
• Networking protocols in IoT are mapped to different layers of the TCP/IP stack.
• Competing IoT technologies from different vendors implement the same standard protocols.
• IEEE 802.15.4 describes low-rate wireless personal area networks (LR-WPANs) and is implemented by technologies like ZigBee, Z-Wave, SNAP, and 6LoWPAN.
• Traditional internet protocols like Ethernet and Wi-Fi can be used within IoT frameworks.
• New IoT-specific technologies are designed to address specific IoT challenges.

Network Topologies

• Topology is the structure of a network.
• Star topology involves devices connecting directly to a central gateway, simplifying network structure but risking a single point of failure.
• Mesh Topology sees devices interconnect with multiple neighboring nodes, increasing complexity but improving resilience and reliability.

Publish/Subscribe Pattern

• Involves indirect communication between a sender (publisher) and receiver (subscriber) via a broker (middleware).
• The broker manages message distribution from publishers to subscribers.
• Publishers and subscribers don't need to know each other's location or synchronization state, promoting loose coupling.
• Subject-based filtering sees messages tagged with topics, with subscribers receiving messages based on subscribed topics.
• Content-based filtering allows subscribers to receive messages that match specific content filters or queries.
• Type-based filtering sees messages filtered based on their type or class.
• Devices can focus on content generation, while brokers handle message distribution, which provides scalable and flexible communication.
• Faults are easier to isolate due to event/topic segmentation, which supports testing.
• Publishers are not notified if messages are successfully delivered.
• High traffic loads may increase system complexity and instability, which are potential network instabilizers.

Representational State Transfer (REST) Pattern

• Treats IoT resources (e.g., sensor data) as identifiable objects using Universal Resource Identifiers (URIs).
• Relies on HTTP protocol, using methods like GET, POST, PUT, and DELETE to manipulate resources with a client/server architecture.
• A GET request retrieves sensor data from a specified URI.
• Responses use JSON format with the requested data (e.g., temperature).
• Leverages existing HTTP protocols rather than creating new standards, which simplifies deployments.
• Clients and servers don't need to track each other's states, which forms a stateless system.
• REST can be implemented in any language capable of making HTTP requests, making it language-agnostic.
• Uses existing internet protocols (SSL/TLS) for encryption and secure data transfer.
• Request structures include HTTP method, headers, resource path, and optional data payload (for POST/PUT).
• Supports content types like JSON, XML, images, and PDFs.