JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III Year FUNDAMENTALS OF INTERNET OF THINGS Previous Question Paper (February - 2023 - R18)

6LoWPAN stands for IPv6 over Low-Power Wireless Personal Area Networks. It is an adaptation layer defined by the IETF (Internet Engineering Task Force) that enables the transmission of IPv6 packets over resource-constrained networks, specifically those based on the IEEE 802.15.4 standard.

Key characteristics include:

• Header Compression: Reduces the overhead of IPv6 headers (which are typically 40 bytes) to fit within the small maximum transmission unit (MTU) of 127 bytes defined by IEEE 802.15.4.
• Fragmentation and Reassembly: Since IPv6 requires a minimum MTU of 1280 bytes, 6LoWPAN provides a mechanism to fragment larger packets into smaller frames and reassemble them at the destination.
• Mesh Routing: Supports multi-hop communication, allowing data to traverse multiple nodes to reach a gateway or sink.
• Interoperability: By bringing IPv6 to low-power devices, it allows IoT sensors and actuators to communicate directly with the internet using standard IP protocols.

The Transport Layer in the IoT architecture serves as the critical communication bridge responsible for end-to-end data delivery between devices, gateways, and cloud servers. Its primary function is to ensure that data packets are transmitted reliably, efficiently, and in the correct order across heterogeneous networks.

• Reliability and Flow Control: It manages data integrity by implementing mechanisms for error detection, retransmission of lost packets, and flow control to prevent network congestion, ensuring that the receiver is not overwhelmed by the sender.
• Segmentation and Reassembly: It breaks down large data streams from the application layer into smaller, manageable segments or datagrams that can be transmitted over the network and reassembles them correctly at the destination.
• Multiplexing: Through the use of port numbers, it enables multiple applications on a single IoT device to communicate simultaneously over the network by directing data to the specific process or service intended.
• Key Protocols:
  • TCP (Transmission Control Protocol): Provides connection-oriented, reliable communication with error checking and ordered delivery, ideal for applications where data accuracy is critical, such as firmware updates or configuration commands.
  • UDP (User Datagram Protocol): A connectionless, lightweight protocol that prioritizes speed and low latency over reliability, commonly used in real-time IoT sensor data streaming where occasional packet loss is acceptable.
  • MQTT-SN and CoAP: While often associated with the application layer, these protocols rely heavily on the transport layer (typically UDP for CoAP) to facilitate lightweight messaging in resource-constrained IoT environments.