JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV ADHOC AND SENSOR NETWORKS Previous Question Paper (July/August - 2022 - R16)

Mobile Ad-hoc Networks (MANETs) are autonomous, self-configuring networks of mobile nodes connected by wireless links. Their key characteristics include:

• Dynamic Network Topology: Nodes are free to move independently, causing frequent changes in network topology and link availability.
• Autonomous Infrastructure: MANETs operate without a centralized administration or fixed infrastructure like base stations or access points.
• Multi-hop Routing: Communication between nodes that are not within transmission range occurs through intermediate nodes acting as routers.
• Resource Constraints: Nodes typically rely on batteries, leading to limitations in energy, processing power, and memory.
• Distributed Operation: Control and management functions are distributed among all nodes, ensuring no single point of failure.
• Fluctuating Link Quality: Wireless links are affected by interference, signal fading, and obstacles, leading to variable link capacity.
• Scalability: The network must support a varying number of nodes, which may join or leave the network dynamically.

Dynamic Source Routing (DSR) is a reactive, source-initiated routing protocol designed specifically for multi-hop wireless ad-hoc networks. It allows the network to be completely self-organizing and self-configuring.

DSR operates through two primary mechanisms:

1. Route Discovery: When a source node needs to send a packet to a destination but has no route in its cache, it broadcasts a Route Request (RREQ) packet. Each intermediate node appends its address to the route record in the packet. When the destination receives the RREQ, it sends back a Route Reply (RREP) containing the accumulated path.
2. Route Maintenance: If a node detects a broken link while forwarding a packet, it sends a Route Error (RERR) packet back to the source. The source then removes the invalid route from its cache and may initiate a new route discovery if needed.

The primary advantage of DSR is that it eliminates the need for periodic routing table updates, as the source node explicitly specifies the entire path in the packet header. This reduces overhead in networks with low mobility, though it can increase packet header size in long paths.