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Lab 1 — Reactive vs proactive route maintenance

Goal. Explain what proactive route sampling buys and what it costs, and why the answer depends on the network. Time. 45 min. Site. The MANET world, seed 6, and the tuning bench.

← Classroom pack · Answer key

Background (5 min)

AntHocNet is a hybrid protocol. It finds a route reactively: when a source has data and no route, it floods forward ants. While a session runs, it also sends proactive ants every few seconds to re-sample the path, so the route follows nodes as they move. The switch for the second part is enableProactive (on by default). See ant types.

1. Predict (5 min)

Write down your answers before you run anything: 1. With proactive ants off, will delivery after 60 s be higher, lower, or the same? By how much? 2. Will the number of ant transmissions be higher, lower, or the same?

2. Run (15 min)

  1. Open #manet?seed=6: 30 devices on a field, two thirds of them moving, with three calls between them.
  2. Run to t = 60 s (use ▶▶▶ to speed up), then pause.
  3. Record ✓ (delivered / sent) and ants from the status bar.
  4. Open Tuning bench → Change a protocol parameter and set enableProactive to off. The world restarts with the change. A faint ghost of the same seed runs at the defaults beside it.
  5. Run to t = 60 s again, pause, and record ✓ and ants. The bench's table shows your run's PDR next to the ghost's.

3. Explain (10 min)

  1. Compare your results with your prediction. Which part surprised you?
  2. Proactive ants cost transmissions. On this field, what did they buy?
  3. The bench's ns-3 line shows the same change as an anthocnet-compare flag. What does it say?

4. Compare with ns-3 (10 min)

configuration.md records a 7-point sweep of the proactive interval (#248): the paper's MANET field, 20 seeds and 900 s per point, with full 802.11 PHY/MAC. 1. Which setting did ns-3 measure as best on the MANET field? Find it in the proactiveInterval row. 2. Why is proactive sampling still on by default? Hint: read the same row and network-regimes.md.