1. Grid: Scalable Ad-Hoc Wireless Networking Robert Morris LCS http://pdos.lcs.mit.edu/grid

2. Goal: Networks out of Chaos AFDBECGJIH

3. Solution: Multi-hop Forwarding AFDBECGJIH “A to J: Hello!”

4. System Status Software distributions for Linux, BSD PC, iPaq Works with unmodified Internet software Two Grid nets deployed

5. LCS Grid Net 5 5 5 5 5 5 5 555 5 6 6 6 6 6 6 17 static nodes on 5 th /6 th floors A dozen iPaq hand-helds wired gateway

6. Roof-Top Grid Net LCS 5 4 3 1 2 6

7. Completed Research Scalable routing: Geographic forwarding Distributed P2P location database Low-power forwarding Understanding capacity limits Avoiding malicious nodes

8. Does Grid Find Useful Paths? AFDBECGJIH

9. Mistake: Shortest-Path Routes AFDBECGJIH A’s max range

10. Link Quality Isn’t Bi-modal

11. Obstacles to Better Routing Use low-loss paths, but… Loss rate masked by 802.11 re-sends Changes quickly with time, motion What’s the best metric to minimize? Expected total packet transmissions Fight strong bias towards shortest paths

12. Grid Summary Grid routing protocols are Self-configuring Easy to deploy Scalable http://www.pdos.lcs.mit.edu/grid

14. Application: Smart Devices Internet Access Point Print E-Mail Share Remote Control

15. Application: Rooftop Nets Game server School/Homework Server Internet Access

16. Application: Disaster Services Disaster may have damaged phone system &c Want to avoid N 2 plans for N services to communicate

17. Direct Contact Scales Badly AFDBECGJIH “Hello J!”

18. Design Challenges Cope with mobile nodes Finding routes Conserving battery power Coping with malicious/faulty nodes Scaling to large networks

19. Topology Distribution Scales Badly 1. “C can reach A and B.” ABCDF 3. Data from F to B. 2. “D can reach A, B, and C.” G

20. Geographic Forwarding Scales Well Longitude Latitude AFDBECG “Send towards lat G / lon G.”

21. Location Database Longitude Latitude AFDBECG DB 1. “G is at lat G / lon G” 2. “Where is G?”

22. Distributed Location Database Each node is DB for a few other nodes How to find a node’s location server(s)? Every node has an unchanging ID hash(ID) maps ID to position in unit square

23. G’s Location Server is a Point G hash(G) = 0.1,0.9 x (0,0) H I

24. Spatial Grid Hierarchy All nodes agree on the global origin of the Grid hierarchy

25. Multiple Servers per Node G c ba

26. Lookups Expand in Scope G c ba A ?

27. Grid Protocol Overhead Grows Slowly Protocol packets include: Grid update, Grid query/reply. Number of nodes Protocol Overhead (packets per second)