Contents • Introduction • Types of wireless network • Adhoc network • Characteristics of Ad hoc network • Why is Routing Different in Ad hoc • Adhoc Routing Protocols • Comparison • Application • Conclusion • References
Types of Wireless Networks • Infrastructure based(Cellular Network). • Infrastructureless Network(Mobile Ad hoc Network) (MANET).
Characteristics of an Ad-hoc network • Collection of mobile nodes forming a temporary network. • Network topology changes frequently and unpredictably. • No centralized administration or standard support services. • Host is also function as router.
Why is Routing Different in Ad Hoc ??? • Host mobility • Dynamic topology • link failure/repair due to mobility • Distributed Environment • Bandwidth constrained • Energy constrained
Table Driven Routing Protocol • Proactive. • Each node maintains one or more tables containing routing information to every other node in the network. • Tables need to be consistent and up-to-date view of the network. • Updates propagate through the network.
Source Initiated On demand routing protocol • Reactive. • on-demand style: create routes only when it is desired by the source node. • When a node requires a route to a destination, it initiates a route discovery process. • Route is maintained until destination becomes unreachable, or source no longer is interested in destination.
Destination-Sequenced Distance Vector Protocol (DSDV) • Basic Routing Protocol. • Based on Bellman ford routing algorithm with some Improvement. • Each node maintains a list of all destinations and number of hops to each destination. • Each entry is marked with a sequence number. • Periodically send table to all neighbors to maintain topology. • Two ways to update neighbors: • Full dump • Incremental update
Example of DSDV A’s Routing Table Before Change A’s Routing Table After Change
Clusterhead Gateway Switch Routing (CGSR) • Similar to DSDV. • Based on concept of clusters and cluster heads. • Routing is done via the cluster heads and gateways. • A routing table among cluster heads are Maintained.
Example of CGSR Data forwarding steps: • from cluster head to cluster head. • in a hierarchical manner • then from cluster head to cluster members. • between two cluster heads, gateways are used to forward the packets.
Ad hoc On-demand Distance Vector Routing(AODV) • Pure on-demand protocol. • Node does not need to maintain knowledge of another node unless it communicates with it. • AODV includes route discovery and route maintenance. • AODV minimizes the number of broadcasts by creating routes on-demand. • AODV uses only symmetric links because the route reply packet. • follows the reverse path of route request packet. • AODV uses hello messages to know its neighbors and to ensure symmetric links.
Path discovery • In the path discovery (RREQ) phase, source broadcasts RREQ message. • Intermediate nodes record in their route tables the address of neighbor from which RREQ is received to establish a reverse path. • When RREQ reaches destination or an intermediate node responds by unicasting a route reply (RREP) back to neighbor.
Path maintenance • If source node moves, reestablish the path. • If destination or intermediate node moves, send link failure notification message to each of its active upstream. • Then reinitiate path discovery .
Dynamic Source Routing Protocol (DSR) • on-demand. • A node maintains route cache containing the routes it knows. • Two main phases • Route discovery • Route maintenance • Basic Operation is similar to AODV. • Main difference • To use routing cache for link failure. • When route discovery phase, node send route request message with its own address.
Zone Routing Protocol • Hybrid of table-driven and on-demand!! • From each node, there is a concept of “zone”. • Within each zone, the routing is performed in a table-driven manner (proactive). • However, a node does not try to keep global routing information. • For inter-zone routing, on-demand routing is used.
Example of ZPR • Three types of nodes: • Border Nodes • Peripherals Nodes • Interior Nodes
Applications • Virtual classroom • Deployment of sensors • Conferences • Exhibitions • Military
Conclusion • Several existing routing protocols for ad hoc wireless networks were described. • So, network context and goal must be kept in mind before choosing any routing protocol. • In terms of metrics: Throughput: The proactive protocols perform better than the reactive protocols. End to End delay:The proactive protocols perform better than reactive protocols. Routing Load: The reactive protocols perform better than the proactive protocols.
References • Elizabeth M. Royer, Chai-Keong Toh, A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks,Proc. IEEE,1999. • David B. Johnson, " Routing in Ad hoc Networks of Mobile Hosts", Proc IEEE Workshop on Mobile Computing Systems and Applications. • Nicklas Beijar “Zone Routing Protocol“. • www.cse.wustl.edu/~jain/cis788-99/adhoc_routing/ • http://www.comp.brad.ac.uk/~sburuha1/index.htm • www.computingunplugged.com/ issues/issue200407/00001326001.html • http://www.ietf.org/rfc/rfc3561.txt