249  Ad Hoc Routing: Reactive (DSR)

249.1 Overview

Dynamic Source Routing (DSR) is a reactive (on-demand) protocol where routes are discovered only when needed for active communication. Unlike proactive protocols that maintain routes continuously, DSR eliminates periodic overhead by discovering routes on-demand through network-wide flooding.

This topic is covered across three focused chapters:

249.2 Chapter Guide

249.2.1 DSR Fundamentals and Route Discovery

Core DSR concepts and the route discovery process

  • DSR protocol overview and unique characteristics
  • Route Request (RREQ) flooding mechanism
  • Route Reply (RREP) options and path selection
  • Source routing packet format
  • Complete route discovery example with sequence diagrams

Best for: Understanding how DSR works at the protocol level

249.2.2 DSR Caching and Route Maintenance

Route caching strategies and error handling

  • Route caching through overhearing
  • Cache management strategies (timeout, LRU, adaptive)
  • The stale cache problem in mobile networks
  • Route Error (RERR) mechanism
  • DSR advantages, disadvantages, and optimal use cases
  • Optimization techniques for IoT deployments

Best for: Understanding cache trade-offs and when DSR is appropriate

249.2.3 DSR Worked Examples and Practice

Practical calculations and real-world scenarios

  • Route discovery latency in emergency response networks
  • Cache timeout optimization for mobile asset tracking
  • Energy trade-off analysis for wildlife monitoring
  • Route error recovery in disaster response
  • Practice problems with detailed solutions

Best for: Applying DSR concepts to real-world IoT deployments

249.3 Learning Path

TipRecommended Sequence
  1. First: Read DSR Fundamentals to understand the protocol mechanics
  2. Then: Study Caching and Maintenance for operational considerations
  3. Finally: Work through Examples and Practice to apply your knowledge

Prerequisites: Before starting, ensure you’ve covered: - Ad Hoc Routing: Proactive (DSDV) - for contrast with table-driven approach - Multi-Hop Fundamentals - for path discovery concepts

249.4 Quick Reference

Aspect DSR Characteristic
Type Reactive (on-demand)
Route Storage Source routing (complete path in packet header)
Discovery RREQ flood, RREP unicast
Maintenance RERR on link failure
Overhead When Idle Zero (no periodic updates)
Discovery Latency Network diameter × per-hop delay
Best For Sparse communication, battery-powered sensors
Avoid For Real-time applications, dense traffic