Routing in Large Scale Ad Hoc and Sensor

Routing in Large Scale Ad Hoc and Sensor Networks Ten H. Lai Ohio State University

Two Approaches n Traditional routing algorithms adapted to ad hoc networks n Geographical routing 2

Review of Routing n Next-hop routing n Source routing n Flooding 3

Next-Hop Routing destination x y. . . next hop a c cost 3 5 X a ? y c Which neighbor (next hop)? 4

Source Routing destination x y. . . path (a, b, c) a cost b c X Which path? 5

Link-State Routing n Each node periodically broadcasts the link states of its outgoing links to the entire network (by flooding). n As a node receives this information, it updates its view of the network topology and routing table. 2 5 3 4 1 4 3 6

Distance-Vector Routing least-cost(A, B) = min {cost(A, x) + least-cost(x, B): for all neighbors, x, of A} n Neighbors exchange distance vectors n Destination A B C D Distance 0 10 … x A E F G B C 7

Routing in MANETs n Every node works as a router 8

Challenges n Quick topology changes n Scalability 9

Two Approaches n Table-driven v Like existing Internet routing protocols n On-demand 10

Table-Driven Routing Protocols l Also called proactive routing protocols l Continuously evaluate the routes l Attempt to maintain consistent, up-to-date routing information Øwhen a route is needed, it is ready immediately l When the network topology changes Øthe protocol responds by propagating updates throughout the network to maintain a consistent view 11

On-Demand Routing Protocols v Also called reactive routing protocols v Discover routes when needed by the source node. v Longer delay 12

Early Ad Hoc Routing Protocols 13

DSDV: Destination Sequence Distance Vector n “Highly Dynamic Destination-Sequence Distance-Vector Routing (DSDV) for Mobile Computers” n Charles E. Perkins & Pravin Bhagwat n Computer Communications Review, 1994 n pp. 234 -244 14

DSDV Overview n DSDV = destination-sequenced distance- vector n Distance-vector routing n Each entry is tagged with a sequence number originated by the destination node. Destination A B C D Distance 0 10 … Sequence # E F G 15

DSDV Route Advertisement n Each node periodically broadcasts its distance vector. v “broadcast” is limited to one hop. v sequence numbers ØFor the sender’s entry: Sender’s new sequence number (typically, +1) ØFor other entries: originally “stamped” by the destination nodes Destination A B C D Distance 0 10 … Sequence # E F G 16

DSDV Route Updating Rules n Paths with more recent seq. nos. are always preferred. n least-cost(A, B) = min {cost(A, x) + least-cost(x, B): for all neighbors, x, of A} x A B C 17

(Source-Initiated) On-Demand Routing Protocols n. DSR n. AODV n. ABR n. SSR n. ZRP 18

DSR: Dynamic Source Routing n “Dynamic Source Routing in Ad-Hoc Wireless Networks” n D. B. Johnson and D. A. Maltz n Mobile Computing, 1996 n pp. 153 -181 19

DSR : Outline n Source Routing n On-demand n Each host maintains a route cache containing all routes it has learned. n Two major parts: v route discovery v route maintenance 20

Route Discovery of DSR n To send a packet, a source node first consults its route cache. v If there is an unexpired route, use it. v Otherwise, initiate a route discovery. n Route Discovery: v Source node launches a ROUTE_REQUEST by flooding. v A ROUTE_REPLY is generated when Ø the route request reaches the destination Ø an intermediate node has an unexpired route to the destination 21

Stale Route Cache Problem n Definition: v A cached route may become stale before it expires. x x 22

Route Maintenance of DSR n When a node detects a link breakage, it generates a ROUTE_ERROR packet. v The packet traverses to the source in the backward direction. v The source removes all contaminated routes, and if necessary, initiates another ROUTE_REQUEST. x x B 23

AODV: Ad-Hoc On-Demand Distance Vector Routing n “Ad-hoc On-Demand Distance Vector Routing” n Charles E Perkins, Elizabeth M Royer n Proc. 2 nd IEEE Wksp. Mobile Comp. Sys. and Apps. , Feb. 1999. 24

AODV : Outline n Next-hop Routing (cf. DSR: source routing) n On-demand n Each host maintains a routing table n Two major parts: v route discovery (by flooding) v route maintenance 25

AODV vs. DSR n DSR: Routes are discovered and cached n AODV: Next-hop info is stored n “Performance Comparison of Two On-Demand Routing Protocols for Ad Hoc Networks, ” Personal Communications, February 2001 26

ABR: Associativity-Based Routing n “Associativity-Based Routing for Ad-Hoc Mobile Networks, ” C. K. Toh. n ABR considers the stability of a link. vcalled the degree of association stability. vmeasured by the number of beacons received from the other end of the link. v. The higher degree of a link’s stability, the lower mobility of the node at the link’s other end. 27

ABR Outline n Route Discovery: v Same as DSR except the following. v Each ROUTE_REQUEST packet collects the association stability information along its path to the destination. v The destination node selects the best route in terms of association stability. 28

n Route Reconstruction: v On route error, a node performs a local search in hope of repairing the path. v If the local search fails, a ROUTE_ERROR is reported to the source local searched zone destination 29

SSA: Signal Stability-Based Adaptive Routing n “Signal Stability-Based Adaptive Routing (SSA) for Ad Hoc Wireless Networks” n University of Maryland n R. Dube, C. D. Rais, K. -Y. Wang & S. K. Tripathi n IEEE Personal Communications, ‘ 97 30

Basic Idea of SSA n Observation: v The ABR only considers the connectivity stability. n Two more metrics: v signal stability: Øthe strength of signal over a link v location stability Øhow fast a host moves 31

ZRP: Zone Routing Protocol n The Zone Routing Protocol (ZRP) for Ad Hoc Networks n Cornell University n Z. J. Haas and M. R. Pearlman n draft-ietf-manet-zone-zrp-01. txt, 1998 32

ZRP Outline n Hybrid of table-driven and on-demand!! n Each node is associated with a zone. n Within a zone: table-driven (proactive) routing. n Inter-zone: on-demand routing (similar to DSR). 33

Route Discovery n By an operation called “boardercast”: v sending the route-request to boarder nodes 34

ZRP Example 35

Scalability Problem in Large-Scale Network Routing n Internet solution 36

Geographic Routing n Make use of location information in routing

Assumptions n Each node knows of its own location. v outdoor positioning device: ØGPS: global positioning system Øaccuracy: in about 5 to 50 meters v indoor positioning device: ØInfrared Øshort-distance radio n The destination’s location is also known. v How? (via a location service) 38

LAR: Location-Aided Routing n Location-Aided Routing (LAR) in mobile ad hoc networks n Young-Bae Ko and Nitin H. Vaidya n Texas A&M University n Wireless Networks 6 (2000) 307– 321 39

Basic Idea of LAR n All packets carry sender’s current location. n This info enables nodes to learn of each other’s location. 40

Basic Idea of LAR (cont. ) n Same as DSR, except that if the destination’s location is known, the ROUTE_REQ is only flooded over the “route search zone. ” D Expected zone of D S Route search zone 41

DREAM n. A Distance Routing Effect Algorithm for Mobility (DREAM) n S. Basagni, I. Chlamtac, V. R. Syrotiuk, B. A. Woodward n The University of Texas at Dallas n Mobicom’ 98 42

Basic Idea of DREAM n Dissemination of location information: v Each node periodically advertises its location (and movement information) by flooding. v This way, nodes have knowledge of one another’s location. 43

Basic Idea of DREAM n Data Packet carries D’s and S’s locations. n Forwarded toward only a certain direction. D Expected zone of D S 44

GRID Routing n “GRID: A Fully Location-Aware Routing Protocol for Mobile Ad Hoc Networks” n Wen-Hwa Liao, Yu-Chee Tseng, Jang-Ping Sheu n NCTU n Telecommunication Systems, 2001. 45

Basic Idea of GRID Routing n Partition the physical area into d x d squares called grids. 46

Protocol Overview n In each grid, a leader is elected, called gateway. n Responsibility of gateways: v forward route discovery packets v propagate data packets to neighbor grids v maintain routes which passes the grid n Routing is performed in a grid-by-grid manner. 47

Route Search Range Options 48

Strength of Grid Routing x x 49

Gateway Election in a Grid n Any “leader election” protocol in distributed computing can be used. n Multiple leaders in a grid are acceptable. n Preference in electing a gateway: v near the physical center of the grid Ølikely to remain in the grid for longer time v once elected, a gateway remains so until leaving the grid 50

Taxonomy of Geographic Routing Algorithms n Also called position-based routing n Three major components of geographic routing: v Location services (dissemination of location information) ØNext topic v Forwarding strategies v Recovery schemes 51

Forwarding Strategies n Basic greedy methods n Directional flooding n Geographical source routing n Power-aware routing 52

Basic greedy methods n Most Forward within Radius (C), 1984 n Nearest Forward Progress (A), 1986 n Compass Routing (B) , 1999 n Random Progress (X), 1984 n The above schemes’ 2 -hop variants 53

Directional Flooding n DREAM (in data packet routing) n LAR (in route discovery) n GRID (in route discovery) 54

Geographical Source Routing n Source specifies a geographical path v Needs an anchor path discovery protocol Terminode routing n GRID n 55

Terminode Routing n “Self Organized Terminode Routing, ” Blazevic, Giordano, Le Boudec Cluster Computing Journal, Vol. 5, No. 2, April 2002 n Remote destinations: v Use geographical routing n Local destinations: v Use non-geographical, proactive routing n Similar to Zone Routing in this sense 56

Terminode Routing n Remote Routing v Anchored Geodesic Packet Forwarding v Geodesic Packet Forwarding (if no anchored path known) v Friend Assisted Path Discovery ØBased on Small World Graphs 57

Small World Graphs n Two nodes are connected if they are acquainted n Sparse, small diameter 58

Terminode routing 59

Power-Aware Routing n “Geographical and Energy Aware Routing: a recursive data dissemination protocol for wireless sensor networks” n Y. Yu, R. Govindan, D. Estrin n UCLA 60

Recovery Schemes With any of the above forwarding strategies, packets may get stuck (hitting a hole). n A recovery scheme is invoked to get around the hole. n v Initiate a route discovery v GPSR (enter the perimeter mode) D S Stuck, initiating a recovery procedure 61

GPSR n “GPSR: Greedy Perimeter Stateless Routing for Wireless Networks” n Brad Karp, H. T. Kung n Harvard University n Mobi. Com 2000 n Two modes: v Greedy (for regular forwarding) v Perimeter (for recovery) 62

Perimeter Mode of GPSR n Suppose nodes x and D are connected by a planar graph. n The graph divides the plane into faces. n Line x. D crosses one or more faces. D x 63

Planar Graphs n Graphs without crossing edges. Not Planar 64

Planar Subgraph n G: communication graph n Relative neighborhood graph (RNG): v Subgraph of G v Keep edge (u, v) iff there are no nodes in the overlapped area. n RNG is planar u v 65

Evolution n Distance Vector, Link State n Proactive n On demand n Hybrid (zone routing) n Geographical routing v Location Service v Location-based Forwarding v Recovery 66

Next? n Location service n Geographical routing without location services n Geocasting: v sending a message to every node within a region. Geocast region Geocast group 67