Routing over MultiHop Wireless Network of Mobile Computers

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Routing over Multi-Hop Wireless Network of Mobile
Computers

• Charles E. Perkins and Pravin Bhagwat
• KAIST COMPUTER ARCHITECTUR LAB
• MS1 KIM YU-SUNG

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Content

• Introduction
• Overview of Routing Methods
• Destination-Sequenced Distance Vector(DSDV)
  Protocol
• Future Work

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Introduction

• ad-hoc network
• collection of wireless mobile hosts forming a
  temporary network without the aid of any
  established infrastructure or centralized
  administration
• topology of interconnections may be dynamic
• self-starting
• usually no administrator
• broadcasting
• not fully connected

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Overview of Routing Methods

• Link-State
• each node maintains a view of the network
  topology with a cost for each link
• each node periodically broadcasts the link costs
  of its adjacent links, to all nodes

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• Distance-Vector (Distribute Bellman-Ford
  Algorithm)
• each node maintains for each destination, a set
  of distance over every neighbor
• each node periodically broadcast its view of the
  distance to all nodes, to each of its neighbors
• compared to link-state
• computationally efficient, easy to implement
• long-lived loop lt propagation speed
• gt many modifications to DBF algorithm
• effective only when topological change rare
• gt Destination-Sequenced Distance
  Vector(DSDV)

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• Bellman-Ford algorithm
• Bellman-Ford(G,w,s)
• Initialize-Single-Source(G,s)
• for i 1 to VG -1
• do for each edge (u,v) in EG
• do Relax(u,v,w)
• for each edge (u,v) in EG
• do if dv gt du w(u,v)
• then return false

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Destination-Sequenced Distance Vector(DSDV)
Protocol

• Approach strategies
• tag each route table entry with a sequence number
  so that nodes can quickly distinguish stale
  routes from the new ones
• gt avoid loop
• Protocol Overview
• each host have routing table
• destinations address
• next hop for each destination
• number of hop for each destination
• sequence number

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• table maintenance
• broadcasting (packet type) - initiator
• periodic full information packet (full dump)
• update packet when significant new information is
  available (incremental packet)
• packet content
• destinations address
• number of hop for each destination
• sequence number
• update - receiver
• recent sequence number
• if same sequence number the smaller metric
• rebroadcasting - receiver
• add 1 to metric and rebroadcast

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• Damping Fluctuations
• cause - difference of propagation speed
• solution
• keep about the length of time between arrival of
  the first and best route for each particular
  destination
• Extending Base Station Coverage
• connection beyond the range imposed by their
  wireless transmitters by participation base
  stations

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Future Work

• more sophisticated cost function
• alternative design
• route discovery on a need-to-know
• many parameters of interest
• frequency of broadcast
• proper using of two packet type
• importance of change that triggering immediate
  incremental packet