Mobile Routing protocols MANET

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Mobile Routing protocolsMANET

• Lecture 4

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DIALOGUE CONTROL

• In any communication there are two types of user
  dialogues.
• long session-oriented transactions and
• short transaction.
• Going through a monolithic document page by page
  can be considered as a session-oriented
  transaction.
• Going to a particular page directly through an
  index can be considered as a short transaction.

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• Selection of the transaction mode will depend on
  the type of device we use.
• A session may be helpful in case of services
  offered through computers with large screens and
  mouse.
• For devices with limited input/ output like SMS
  for instance, short transactions may be desired.
• Let us consider an example of bank balance
  enquiry over the Internet.

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• In case of Internet banking through desktop
  computer, the user has to go through the
  following minimum dialogues
• Enter the URL of the bank site.
• 2. Enter the account number/password and Login
  into the application.
• 3. Select the balance enquiry dialogue and see
  the balance.
• 4. Logout from the internet banking.

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• The dialogue above is an example of
  session-oriented transaction.
• Using short transaction, the same objective can
  be met through one single dialogue.

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Ad-hoc Networks

• 'In Latin, ad hoc literally means 'for this
  purpose only'.
• An ad-hoc (or spontaneous) network is a small
  area network, especially one with wireless or
  temporary plug-in connections.
• In these networks some of the devices are part of
  the network only for the duration of a
  communication session.

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• An ad-hoc network is also formed when mobile, or
  portable devices, operate in close proximity of
  each other or with the rest of the network.
• When we beam a business card from our PDA
  (Personal Digital Assistant) to another, or use
  an IrDA (Infrared Data Association) port to print
  document from our laptop, we have formed an ad
  hoc network.

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• The term 'ad hoc' has been applied to networks in
  which new devices can be quickly added using, for
  example, Bluetooth or wireless LAN (802. 11x).
• In these networks devices communicate with the
  computer and other devices using wireless
  transmission.
• Typically based on short-range wireless
  technology, these networks don't require
  subscription services or carrier networks.

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• May need to traverse multiple links to reach a
  destination

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Mobile Ad Hoc Networks

• Mobility causes route changes

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Mobile Ad Hoc Networks

• Formed by wireless hosts which may be mobile
• Dont need a pre-existing infrastructure
• ie, dont need a backbone network, routers, etc.
• Routes between nodes potentially contain multiple
  hops

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Mobile Ad Hoc Networks

• Why MANET?
• Ease, speed of deployment
• Decreased dependence on infrastructure
• Can use in many scenarios where deployment of a
  wired network is impractical or impossible
• Lots of military applications, but there are
  others

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MANET Many Applications

• Personal area networking
• cell phone, laptop, ear phone, wrist watch
• Civilian environments
• meeting rooms
• sports stadiums
• groups of boats, small aircraft (wired REALLY
  impractical!!)
• Emergency operations
• search-and-rescue
• policing and fire fighting
• Sensor networks
• Groups of sensors embedded in the environment or
  scattered over a target area

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Many Variations

• Fully Symmetric Environment
• all nodes have identical capabilities and
  responsibilities
• Asymmetric Capabilities
• transmission ranges and radios may differ
• battery life at different nodes may differ
• processing capacity may be different at different
  nodes
• speed of movement different
• Asymmetric Responsibilities
• only some nodes may route packets
• some nodes may act as leaders of nearby nodes
  (e.g., cluster head)

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Many Variations

• Traffic characteristics may differ
• bandwidth
• timeliness constraints
• reliability requirements
• unicast / broadcast / multicast / geocast
• May co-exist (and co-operate) with an
  infrastructure-based network

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Many Variations

• Mobility patterns may be different
• people sitting at an airport lounge (little
  mobility)
• taxi cabs (highly mobile)
• military movements (mostly clustered?)
• personal area network (again, mostly clustered?)
• Mobility characteristics
• speed
• predictability
• direction of movement
• pattern of movement
• uniformity (or lack thereof) of mobility
  characteristics among different nodes

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Challenges

• Limited wireless transmission range
• Broadcast nature of the wireless medium
• Packet losses due to transmission errors
• Environmental issues (chop that tree!!)
• Mobility-induced route changes
• Mobility-induced packet losses
• Battery constraints
• Potentially frequent network partitions
• Ease of snooping on wireless transmissions
  (security hazard)
• Sensor networks very resource-constrained!

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Hidden Terminal Problem

• Nodes A and C cannot hear each other
• Transmissions by nodes A and C can collide at
  node B
• On collision, both transmissions are lost
• Nodes A and C are hidden from each other

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First Issue Routing

• Why is Ad hoc Routing Different?
• Host mobility
• link failure/repair due to mobility may have
  different characteristics than those due to other
  causes
• traditional routing algorithms assume relatively
  stable network topology, few router failures
• Rate of link failure/repair may be high when
  nodes move fast
• New performance criteria may be used
• route stability despite mobility
• energy consumption

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Routing Protocols

• Proactive protocols
• Determine routes independent of traffic pattern
• Traditional routing protocols for wired networks
  are proactive
• Proactive Approach (Table Driven)
• In this approach route calculation is a
  consistent process.
• Routing tables are maintained at every node.
• Every node exchange routing information timely
  with its neighbors.
• This approach uses large bandwidth to maintain
  unused route.

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• Reactive protocols
• Discover/maintain routes only if needed
• Reactive Approach (On Demand)
• The reactive protocols in contrast create routes,
  when it requires.
• Reactive protocols do not send periodic updates.
• Each node send control message to discover a
  route between source and destination, only when
  it is required.
• In this process route discovery takes a long
  time.

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Trade-Off Proactive vs. Reactive

• Latency of route discovery
• Proactive protocols may have lower latency since
  routes are maintained at all times
• Reactive protocols may have higher latency
  because a route from X to Y will be found only
  when X attempts to send to Y
• Overhead of route discovery/maintenance
• Reactive protocols may have lower overhead since
  routes are determined only if needed
• Proactive protocols can (but not necessarily)
  result in higher overhead due to continuous route
  updating
• Which approach achieves a better tradeoff depends
  on the traffic and mobility patterns