1. A Review of Current Routing Potocols for Ad-Hoc Mobile Wireless Networks Yibo Sun sunyibo@gmail.com

2. “A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks” Elizabeth M.Royer, C-K Toh Link: http://bingweb.binghamton.edu/~ysun6/review-current-routing-prot.pdf

3. Ad-Hoc, Mobile, Wireless Infrastructureless networks : no fixed routers All nodes are capable of movement and can be connected dynamically Interconnections between nodes are changing on a continual basis

4. E.G Emergency search-and rescue operations Meetings in which persons wish to quickly share information Data acquisition operations in inhospitable terrains

5. A brief view of Ad-Hoc Routing Protocols

6. Table-Driven Routing Protocols Basic idea: Maintain consistent, up-to-date routing information from each node to every other node in the network. Each node:  Maintains one or more tables to store routing information  Respond to changes in network topology by propagating updates throughout the network

7. Destintion-Sequenced Distance-Vector Routing (DSDV) Based on classical Bellman-Ford routing mechanism Improvement : freedom from loops in routing table Table Record Structure  All possible destinations and the hop count  Each entry with a sequence number assigned by the destination node (to distinguish stale routes from new ones, thereby avoiding the formation of routing loops)

8. Route update mechanism “full dump” packet  All available routing information and can require multiple network protocol data units (NPDUs)  Periodically, or on certain event “incremental” packet  Routes changed since last full dump  Contains the address of the destination, the hop count to reach it, the sequence number, and a new unique sequence number Both packets are sent in broadcast way, and should fit into a standard size NPDU, to decrease traffic.

9. Route update mechanism (contd.) Route labeled with the most recent sequence number is always used Route with smaller metric is used to shorten the path, when two updates have the same sequence number Drawback: cares 0 about power saving, link state changing, few on fault-tolerant, and lack of scalability (each node maintain a whole routing table)

10. Clusterhead Gateway Switch Routing (CGSR) CGSR uses DSDV as the underlying routing scheme, but differed in type of addressing and network organization  Layered infrastructure “Cluster head” node: a node controlling a group of ad-hoc nodes “Gateway” node: node within communication range of two or more cluster heads  LCC (Least Cluster Change) algorithm Cluster heads only change when two cluster heads come into contact, or when a node moves out of contact of all other cluster heads.

11. Head-to-Gateway

12. Node cache  A routing table  Cluster member table Routing procedure On receiving a packet, a node  First, consult its cluster member table and routing table to determine the nearest cluster head along the route to destination.  Next, check its routing table to determine the node in order to reach the selected cluster head  Last, transmit

13. Wireless Routing Protocol (WRP) Node Cache  Distance table  Routing table  Link-cost table (cares about link-state)  Message retransmission list (MRL) table Sequence number of the update message Retransmission counter Acknowledgment-required flag vector List of updates sent to neighbor

14. Route update mechanism When link changes, a node send its neighbors the update message contains:  The destination  The distance to the destination  The predecessor of the destination Send “Hello” message to ensure connectivity, if no packets to send

16. Source-Initiated On-demand Routing Routes only when desired by the source node. Include two parts:  Route discovery  Route maintenance

17. Ad-hoc On-Demand Distance Vector Routing (AODV) AODV is built on DSDV, while improved by minimizing the number of required broadcasts, by creating routes on an on- demand basis. The author of AODV classify it as a pure on-demand route acquisition system.

18. Node cache  Broadcast ID  Sequence number Route discovery  First, broadcast a route request (RREQ) packet to its neighbor  Then, it is forwarded to their neighbors, and so on  Till the destination is found, or an inter node with a “fresh enough” route to the destination is found  During forwarding, the inter nodes record in their route table the address of the neighbor, from which the first copy of the broadcast packet is received, thereby establishing a reverse path

19. Route maintenance  Source move: Reinitiate the route discovery protocol to find a new route to the destination  Inter node move: The upstream neighbor propagates a link failure notification message to each of its active upstream neighbors to inform them of the erasure of that part of the route And it is forwarded, and so on, till the source is reached The source then reinitiate the route discovery procedure  “Hello” message

20. Dynamic Source Routing (DSR) Based on the concept of source routing  Mobile nodes are required to maintain route caches that contain the source routes of which the mobile is aware

21. Temporally-ordered Routing Algorithm (TORA) For highly dynamic mobile networking environment, hence the key design concept is: localization of control message to a small set of nodes near the occurrence of a topological change. Based on link reversal TORA includes 3 parts  Route creation  Route Maintenance  Route erasure

23. Associativity-Based Routing (ABR) ABR uses a totally new routing metric called: degree of association stability, defined by connection stability of one route, hence to derive longer-lived routes. Each node periodically generates a beacon to signify its existence. The neighbors then update the associativity table, increase the corresponding entry’s associativity tick. High associativity tick = low mobility

24. Route discovery  Source broadcast query and await-reply (BQ-REPLY cycle)  All nodes receiving query append their address, associativity ticks with their neighbor with Qos information to the query packet  A successor node erases its upstream node neighbors’ associativity tick entries and retains only the entry concerned with itself and its upstream node  The destination can choose the best path (first consider overall degree, then the shortest path), then send a reply packet

25. Route re-construction (RRC)  Source Move cause Route discovery again  Destination Move: Upstream node erases its route and determines if the node is still reachable by a localized query (LQ[H]) If destination receive LQ, replies the best partial path; or if timeout, then backtrack to upstream node, along with LN[0] message to inform erase the route Route deletion

28. Thanks