Mobile Ad-hoc Networks -- Overview and a case study Yinzhe Yu Oct. 8, 2003

Introduction on MANET Recent research topics Case study: Dynamic Source Routing Contents

What is a MANET ? Mobile nodes, wireless links Infrastructure-less: by the nodes,… Multi-hop routing: …,and for the nodes Minimal administration: no hassles

Hmm, A MANET makes sense. Dad, you can use Nelson if I am too fast. Hi, Marge. I miss you. I can hear u, Lisa. Can u hear me? Yes. What are you doing, Nelson? Be home early, Homer. Application Example – The Simpson's

Why a MANET? Fast deployment of ad-hoc networks Special events/conference, military combat/emergency rescue What about also cheaper ? sensor dust, home networking

What’s unique about a MANET ? Moving nodes  ever changing topology Wireless links  various and volatile link quality Pervasive (cheap) devices  Power constraints Security  Confidentiality, other attacks

MANET Protocol Zoo Topology based routing Proactive approach, e.g., DSDV. Reactive approach, e.g., DSR, AODV, TORA. Hybrid approach, e.g., Cluster, ZRP. Position based routing Location Services: DREAM, Quorum-based, GLS, Home zone etc. Forwarding Strategy: Greedy, GPSR, RDF, Hierarchical, etc.

Recent Research Topics Routing Better metric, higher throughput A high-throughput path metric for multi-hop wireless routing. MobiCom 03. Transport Layer TCP performance: throughput, fairness, etc. Enhancing TCP fairness in ad-hoc networks using neighborhood RED. MobiCom 03. Improving fairness among TCP flows crossing wireless ad-hoc and wired networks. MobiHoc 03. MAC Layer MAC protocol for directional antennas A MAC protocol for full exploitation of directional antennas in ad-hoc wireless networks. MobiHoc 03.

Recent Research Topics (cont.) Security Reliable routing against malicious nodes Ariadne: A secure on-demand routing protocol for ad-hoc networks. MobiCom Power Management Power saving and power control Asynchronous wakeup for ad hoc networks. MobiHoc A power control MAC protocol for ad hoc network. MobiCom 2002.

A Case study: Dynamic Source Routing On-demand Source Routing Route Discovery Route Request Route Reply Route Maintenance

Assumption: Cooperative nodes Relatively small network diameter (5-10 hops) Detectable packet error Unidirectional or bidirectional link Promiscuous mode (optional)

A B C E D G H F A A A-B A-C A-C-E A-B-DA-B-D-G Route Discovery A-B-C Route Request (RREQ) Route Reply (RREP) Route Discovery is issued with exponential back-off intervals. Initiator ID Initiator seq# Target ID Partial route RREQ FORMAT

Route Discovery: at source A A need to send to G Lookup Cache for route A to G Route found ? Start Route Discovery Protocol Continue normal processing Route Discovery finished Packet in buffer ? Send packet to next-hop don e Buffer packet no Write route in packet header yes no wait

Route Discovery: At an intermediate node Accept route request packet in recently seen requests list? Discard route request yes no Host’s address already in patrial route Discard route request yes Store in list Broadcast packet Send route reply packet done myAdd r=targ et no Append myAddr to partial route no yes

A B C E D G H F Route Maintenance G RERR Route Cache (A) G: A, B, D, G G: A, C, E, H, G F: B, C, F

Additional feature #1: Caching Overheard Routes ABCDE VWXYZ Node A Cache E: A, B, C, D, E Node C Cache E: C, D, E E: C, D, E A: C, B, A E: C, D, E A: C, B, A Z: C, X, Y, Z V: C, X, W, V

Additional feature #2: RREP with Cached Routes A B C E D H F G RERR Route Cache (A) G: A, B, D, G F: B, C, F RREQ Route Cache (C) G: C, E, H, G RREP G:A,C,E,H,G Route Cache (C) G: C, E, D, G RREQ (! D-G) RREQ (! D-G) RREQ (! D-G)

A B C E D G H F Additional feature #3: Packet Salvage G RERR Route Cache (D) G: D, E, H, G Caution: No double salvage allowed !!!

A Summary of DSR Entirely on-demand, potentially zero control message overhead Trivially loop-free with source routing Conceptually supports unidirectional links as well as bidirectional links High packet delays/jitters associated with on-demand routing Space overhead in packets and route caches Promiscuous mode operations consume excessive amount of power