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					                         Routing Protocols
                               in MANETs

             Presentation by: Irabatti Swapnil Narsingh
                                      Class: T.E(C.S.E)
                                          Roll No: 3139


Guided by:    Prof.R.Maheshwar


                                        March 2012
Features of MANET
 Self-configuring network.
 Infrastructure-less: by the nodes.
 Dynamic topology, Multi-hop routing.
 Limited Bandwidth & Limited Power.
What’s unique about a MANET ?


 Moving nodes
  o  changing in topology
 Wireless links
    Bandwidth and throughput
 cheap devices
   Power constraints
Routing Protocols in MANET
 Reactive (On-demand) protocols
  Discover routes when needed
  Source-initiated route discovery
 Proactive protocols
  Traditional distributed shortest-path protocols
  Based on periodic updates. High routing overhead
 Hybrid protocols
  Routing protocols of globally reactive and locally
   proactive states.
Reactive Routing

 Key Goal:
 minimize time delay.
 maximize network throughput.
 maximize network life span.
 maximize energy efficiency.



 Two key protocols: DSR and AODV
Dynamic Source Routing (DSR)
 source routing
 on-demand
 Detectable packet error
 Unidirectional or bidirectional link
 Not an timer-based activity
 Two Methods:
1.   route discovery
2. route maintenance
Reactive Routing – Source initiated

 Source floods the network with a route request
  packet when a route is required to a destination
    Flood is propagated outwards from the source
    Pure flooding = every node transmits the request only
     once
 Destination replies to request
    Reply uses reversed path of route request
    sets up the forward path
Route Discovery                                             RREQ FORMAT

                    B                                           Initiator ID
                         A-B-D-G
                                        A-B-D-G   G            Initiator seq#
  A-B-D-G
                        A-B                                      Target ID
            A                     D       A-B-D
                                                                Partial route

    A
                                  A-C-E

        A                     E                       H       A-B-C
                                         A-C-E
                                                          Route Request (RREQ)
                                      A-C-E
                C       A-C                                    A-B-C
                                         F                Route Reply (RREP)


 Route Discovery is issued with exponential back-off intervals.
Route Discovery: at source A
                                   A need to send to G


                             Lookup Cache for route A to G


  Start Route                     no        Route
   Discovery       Buffer                   found
                   packet                     ?
   Protocol
                                                yes
                 Continue
                  normal
                             yes
     wait




                processing              Write route in
                                        packet header
                         Packet
      Route                in
    Discovery            buffer                   Send
     finished              ?           no
                                                packet to
                                  done          next-hop
 Route Maintenance

                           B
                               RERR
             RERR                                 G

                                      D
                                                          G

             A


                   A                      A-C-E
                                 E                    H


                       C
Route Cache (A)
G: A, B, D, G                             F
G: A, C, E, H, G
F: B, C, F
Ad hoc On-demand Distance Vector
Routing Protocol (AODV)
The AODV Routing protocol uses an on-
 demand approach for finding routes
Flow for data packet transmission.
Uses a destination sequence number to
 determine an up-to-date path.
Recovers the route errors and link
 failures
   AODV Routing Protocol
Broadcast transmission

                             S       E
                                             F
                   A
                                 C

                                         G       D
                         B
          Represents a node that has received RREQ(routing request
         -massage ).


           Represents transmission of RREQ
AODV Route Discovery

                      S       E
                                      F
              A
                          C

                                  G       D
                  B




 Node C ,A&E sends RREP(routing reply -massage) to node S
 Reverse paths are formed when a node hears a route
  request.
AODV Route Discovery

                     S       E
                                     F
             A
                         C

                                 G       D
                 B


 Similarly as before C & E sends the RREQ(routing
  request -massage ) to B,G&F
AODV Route Discovery

                     S       E
                                     F
             A
                         C

                                 G       D
                 B

 Uses hop-by-hop routing.
 Each node forwards the request only once (pure
  flooding).
 Reverse paths are formed when a node hears a route
  request.
AODV Route Discovery

                    S       E
                                    F
            A
                        C

                                G       D
                B


 Route reply forwarded via the reverse path.
AODV Route Discovery

                  S       E
                                  F
          A
                      C

                              G       D
              B

 thus forming the forward path.
 The forward path is used to route data
  packets.
Route Expiry

                 S       E
                                 F
         A
                     C

                             G       D
             B


Unused paths expire based on a timer.
Path Maintenance
                         3’                            3’

         1       3                         1
                         Destination                   Destination

             2                                 2
Source               4            Source           4

 Movement not along active path triggers no action
    If source moves, reinitiate route discovery
 When destination or intermediate node moves
     upstream node of break broadcasts Route Error (RERR)
     RERR contains list of all destinations no longer reachable due
      to link break
     RERR propagated until node with no precursors for
      destination is reached
 Applications
 military applications.
Public internet access.
campus-area communication networks
sensor networks.
Intelligent file transfer system.
     Advantages
Route is established only when it is required.
Eliminating the periodic table-update.
Supports unidirectional links as well as bidirectional
links.
Capable of both unicast and multicast routing.
Uses low bandwidth and low power.
Infrastructure-less.
     Disadvantages

Not scalable: Packet header size grows linearly with
route length.
Route maintenance mechanism does not globally repair
a broken link.
Cache information could also result in inconsistencies
during the route reconstruction phase.
The performance degrades rapidly with increasing
mobility.
Conclusion
 MANET are an ideal technology to establish in an instant
  communication infrastructure-less. MANETs require a reliable,
  efficient, scalable and most importantly, a secure protocol as
  they are highly insecure, self-organizing, rapidly deployed and
  they use dynamic routing which is totally possible with DSR &
  AODV Routing Protocols.
Questions…




THANK
YOU………

				
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