Wireless Routing Protocols

1. Wireless Routing Protocols Matt Cleveland

2. Mobile network types • Infrastructured network is a network, such as this campus, with fixed and wired gateways • Ad-hoc network, has no fixed routers, all nodes are capable of movement and all may function as routers (emergency search and rescue operations, conventions where people wish to quickly share information, and data acquisition in inhospitable terrain)

3. Ad-Hoc Network types • Table driven

4. Ad-Hoc Network types • On-demand

5. Table-Driven Protocols • Have consistent overview of the network • Table contains routing information to every other node in the network • Typically broadcasts a specified beacon “hello” to network at fixed intervals of time and updates its connection table accordingly • Destination Sequence Distance Vector (DSDV), Wireless Routing Protocol (WRP), and Cluster-head Gateway Switch Routing (CGSR) are common protocols using this technique

6. Destination Sequence Distance Vector (DSDV) • Routing table contains list to all available destinations, number of hops required to reach each destination, and the sequence number (last updated) • Periodically transmit updated table information to neighboring machines, or in the event of a change, do so as well

7. Destination Sequence Distance Vector (DSDV) • Full dump – transmit entire contents of routing table to neighbors • Incremental update – transmits only pertinent table updates to neighbors • Full dump occur in rapidly-changing network where incremental updates are used in relatively stable networks to avoid extra traffic

8. Wireless Routing Protocol (WRP) • Each node contains a Distance table, a Routing table, a Link-Cost table, and a Message-Retransmission list • Distance table contains distance between the node and a given node y from each of current node’s neighbors • Routing table contains list of distances between the node and a given node y from given node x, along with the predecessors and successors of x

9. Wireless Routing Protocol (WRP) • Link-Cost table contains the cost of connecting to each of the node’s neighbors, along with information regarding timeouts • Message Retransmission List has information regarding which nodes need to be resent information (like stop-N-wait)

10. Clusterhead Gateway Switch Routing (CGSR) protocol • Is based on the DSDV protocol • Nodes are combined into clusters with a specified cluster-head • Nodes that lie in overlapping clusters are designated as Gateway nodes

11. Clusterhead Gateway Switch Routing (CGSR) diagram

12. Clusterhead Gateway Switch Routing (CGSR) • Requested packets are transmitted to cluster-head, then transmitted to the gateway node • Receiving end does this in reverse order • Nodes contain table of paths to other nodes on network using DSDV algorithm

13. Advantages of Table-Driven Protocol • Having up-to-date list of all possible connections to devices on network

14. Disadvantages of Table-Driven Protocols • Continuous table updating may be redundant and unnecessary (wastes CPU and battery, which are extremely limited commodities in a mobile device) • Tables updating causes unnecessary network overhead in many instances

15. On-Demand routing protocols • When path is needed to given source, must wait until path is discovered • AODV, DSR, and ABR are common protocols using this strategy

16. Ad-Hoc On Demand Vector Routing (AODV) • To find path to destination, source broadcasts a request packet • Packet is rebroadcast by neighbors and neighbors’ neighbors until it either reaches the destination or finds a node with recent routing information regarding the destination • Request is returned, and each node in path appends its routing information in the request

17. Ad-Hoc On Demand Vector Routing (AODV)

18. Dynamic Source Routing (DSR) • Nodes contain path routes in cache, which are updated when new information is discovered • When a message is sent, a node checks its cache to see if the destination is known, if so, message is sent, otherwise a request is broadcast to neighbors asking for path

19. Associativity-Based Routing (ABR) • Routes are selected based on degree of association stability of given nodes. • Nodes periodically generate beacons to acknowledge is alive. • Beacon is received and nodes are updated with node’s information (degree of association stability).

20. Associativity-Based Routing (ABR) • Has three phases • Route Discovery – • Broadcasts query: sends request for path to destination node, nodes with information respond, appending their information (associativity) on the query for a full path • The path to the destination with the best associativity is chosen

21. Associativity-Based Routing (ABR) • Route reconstruction – prompted by moving or new nodes, which causes change in associativity • Partial route discovery • Invalid route erasure • Valid route updates • New route discovery • Route Deletion – when a path is found to be no longer valid, a route delete (RD) broadcast is sent to other nodes so that they can update their information

22. Advantages of On-Demand Protocols • Only have to determine routing path when necessary • Highly dynamic and adaptable, doesn’t rely on a stable network

23. Disadvantages of On-Demand Protocols • Takes longer to discover routing path than it does to look it up on an IP table

24. Bibliography • http://www.computingunplugged.com/issues/issue200407/00001326001.html • http://citeseer.ist.psu.edu/cache/papers/cs/16265/http:zSzzSzusers.ece.gatech.eduzSz~cktohzSzroyer-ck.pdf/royer99review.pdf • http://www.cse.ohio-state.edu/~jain/cis788-99/ftp/adhoc_routing/index.html