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A Review of Current Routing Potocols for Ad-Hoc Mobile Wireless Networks

A Review of Current Routing Potocols for Ad-Hoc Mobile Wireless Networks. Yibo Sun sunyibo@gmail.com. “ A Review of Current Routing Protocols for Ad-Hoc Mobile Wireless Networks ” Elizabeth M.Royer, C-K Toh Link:

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A Review of Current Routing Potocols for Ad-Hoc Mobile Wireless Networks

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  1. A Review of Current Routing Potocols for Ad-Hoc MobileWireless 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

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

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. Thanks

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