Grid: Scalable Ad-Hoc Wireless Networking Robert Morris LCS

Goal: Networks out of Chaos AFDBECGJIH

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

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

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

Roof-Top Grid Net LCS

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

Does Grid Find Useful Paths? AFDBECGJIH

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

Link Quality Isn’t Bi-modal

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

Grid Summary Grid routing protocols are Self-configuring Easy to deploy Scalable

Application: Smart Devices Internet Access Point Print Share Remote Control

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

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

Direct Contact Scales Badly AFDBECGJIH “Hello J!”

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

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

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

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

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

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

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

Multiple Servers per Node G c ba

Lookups Expand in Scope G c ba A ?

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