Review of Adhoc Mobile Network Technology

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					From the slides of ETH Zurich, Tutorial.
Adhoc Mobile Routing Protocols
    (layer 3) and UbiComp
  Ubiquitous & Mobile Computing Course Presentation
         – Issues of Wireless Communications

                    Delivered by
                    Ayaz Ahmed
Today’s Talk

 Routing
 Mobile Ad Hoc Routing - Review of Paper(s)
 Mobile Ad-hoc Communication Issues in
  Ubiquitous Computing
 View Ad Hoc Connection (not routing)
 Discussion
Typical IP Routing
 “Routing is the act of moving information across an
  internetwork from a source to a destination. Along the way,
  at least one intermediate node typically is encountered.”

 Routing involves two basic activities:

    determining optimal routing paths
         Can be very complex

    transporting packets (packet switching/forwarding)
         Relatively straight forward

                                              (http://cisco.com)
  Two basic Classes of Routing




Distance Vector ( RIP)



                                                 Link State (OSPF)
 Yes – these are Internal and External is BGP4
                                                  (http://cisco.com)
Routing in (Mobile) Ad-hoc Networks

 Proactive Routing:
    “keep routing information current at all times”
    good for static networks
    Eg.: distance vector (DV), link state (LS) algorithms

 Reactive Routing:
    “find a route to the destination only after a request comes in”
    good for more dynamic networks and low communication
    Eg: Ad hoc On-demand distance Vector (AODV), Dynamic
     Source Routing (DSR)

 Hybrid Schemes:
    “keep some information current”
    example: Zone Routing Protocol (ZRP)
Papers Read
 A Review of Current Routing Protocols for Ad Hoc Mobile Wireless
  Networks
       IEEE Personal Communications • April 1999; by Elizabeth M. Royer, University
        of California, Santa Barbara and Chai-Keong Toh, Georgia Institute of Technology


 Network Layer Mobility: An Architecture and Survey

       IEEE Personal Communications • June 1996; by Pravin Bhagwat, Charles
        Perkins, and Satish Tripathi


 Mobile Ad-hoc Communication Issues in Ubiquitous Computing The Smart-
  Its Experimentation Platforms
       Albrecht Schmidt#, Frank Siegemund*, Michael Beigl+ Stavros Antifakos‡, Florian
        Michahelles‡, Hans-W. Gellersen
Summary - A Review of Current Routing Protocols
for Ad Hoc Mobile Wireless Networks


 Briefly describes several routing protocols
  proposed for ad hoc mobile networks
 Classifies the protocols according to the
  routing strategy.
 Presents a comparison among the features,
  differences, and characteristics of the
  protocols.
   Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




The Classification of protocols
    Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Destination-Sequenced Distance-
vector Routing (DSDV)
 Each node maintains every possible destinations
    Common in table-driven
 Tables
    Routing Table + table to keep track of incremental
     updates
 Periodic updates
    Full Dump
    Incremental updates
 Disadvantage
    Periodic updates regardless of the # of changes in the
     topology
    Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Clusterhead Gateway Switch Routing (CGSR)

 Hierarchical address space
    Nodes are grouped into clusters.
    Special nodes
         Cluster head
                 Forwards packets to gateways on behalf of source nodes
                 Dynamically elected
         Gateway
                 nodes within the communication range of two or more cluster head
 Tables
    Cluster member table: (node -> cluster head)
    Routing table: (cluster head -> next hop)
 Using DSDV to broadcast the member table periodically
 Disadvantage
    Too frequent cluster head selection can be an overhead
    Cluster nodes and Gateway can be a bottleneck
    Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Wireless Routing Protocol (WRP)
 Tables
      Distance table
      Routing table
      Link-cost table
      Message retransmission list (MRL) table
 Periodic hello message
    To keep track of alive neighbors
 Loop Free
    By forcing each node to check consistency of predecessor
     information reported by all it’s neighbors
 Disadvantage
    4 tables requires a large amount of memory
    Periodic hello message consumes power and bandwidth
   Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Comparison among Table-driven
routing protocols
   Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Ad Hoc On-demand Distance Vector
Routing (AODV)
 On-demand version of DSDV
 Pure on-demand routing acquisition system
   Nodes out of the routing path doesn’t maintain
    any information about the path
 Assumes a symmetric link
   Route reply packets use the reverse path of
    route request packets
 Route Timer
   remove stale entries
 Supports multicast
    Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Dynamic Source Routing (DSR)
 Route Cache:
    maintains source routes
 Append visited node id into a packet
 Assumes an asymmetric path
    A destination node sends another Route request to the
     source node to find a reverse path
    Reply is piggybacked on the request packet.
 Advantage
    No periodic hello message
    Fast recovery: cache can store multiple paths to a
     destination
 Disadvantage
    Scalability : packet size grows with the network size
   Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Temporally Ordered Routing
Algorithm (TORA)
 Height
   Logical metric to build Directed Acyclic Graph (DAG)
    rooted at the destination.
 Timing
   Because it assumes the synchronized clock among nodes
   Therefore, it relies on external time source such as GPS
 Advantage
   Supports multiple paths to a destination (like DSR)
 Disadvantage
   Reliance on global time synchronization
     Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Associativity-Based Routing
(ABR)
 Connection-oriented approach
 Associativity table
    A node increases associativity of its neighbor when it receives
     periodic beacon message from the neighbor.
    Represents association stability (i.e. connection stability)
 Route Discovery
    Append associativity into the packet
    Destination node examines the best routes by associativity
     values in the packets
    Destination sends the reply along the selected path
 Prefers long-lived routes
    Selecting nodes with less mobility. (i.e. high degree of
     association)
 Advantage
    Free from duplicate packets.
 Disadvantage
    Short beaconing interval to reflect association degree precisely.
    Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Signal Stability Routing (SSR)
 Selects routes based on signal strength between nodes
 Prefers stronger connectivity
 Tables
    Signal Strength Table (SST)
    Routing Table (RT)
 Two protocols
    Dynamic Routing Protocol (DRP): manages SST & RT
    Static Routing Protocol (SRP): forwards packets based on RT
 Advantage
    To select strong connection leads to fewer route reconstruction
 Disadvantage
    Long delay since intermediate nodes can’t answer the path
     (unlike AODV, DSR)
  Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Comparison among On-demand
routing protocols
      Summary - A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks




Table-driven vs. On-demand

     Parameters                              On-demand                              Table-driven
Availability of routing                                                         Always available
                                    Available when needed
     information                                                               regardless of need
Periodic route updates                      Not required                               Required
                                       Use localized route                  Inform other nodes to
 Coping with mobility                       discovery                        achieve a consistent
                                          (ABR and SSR)                         routing table
                                    Grows with increasing
                                                                             Greater than that of
  Signaling traffic                   mobility of active
                                                                              on-demand routing
                                           routes
                     Network Layer Mobility: An Architecture and Survey


             Mobile IP Motivation

Traditional routing
    based on IP destination address
    network prefix determines physical subnet
    change of physical subnet implies change of
    IP address (conform to new subnet), or special routing table entries to forward
    packets to new subnet
Changing of IP address
    DNS updates take to long time
    TCP connections break
    security problems
Changing entries in routing tables
    does not scale with the number of mobile hosts and frequent changes in the
    location
    security problems
Solution requirements
    retain same IP address, use same layer 2 protocols
    •authentication of registration messages, …
           Network Layer Mobility: An Architecture and Survey




    Mobile IP Features


 You can take notebook to any location
 Finds nearby IP routers and connects
   automatically
 you do not even need to find a phone jack
 Only Mobility Aware Routers and mobile units
   need new software
 Other routers and hosts can use current IP
 No new IP address or address formats
 Allows authentication; providing security
              Network Layer Mobility: An Architecture and Survey



      Mobile IP Process


 Agent Discovery – to find agents
    HA and FA advertise periodically on network layer
    and optionally on Data Link layer
    They also respond to solicitation from MN
    MN selects an agent and gets/uses COA.

 Registration
    MN registers its COA/co-COA with HA; either
    direct or through FA
    HA send a reply to MN via FA on COA.
         Network Layer Mobility: An Architecture and Survey




Registration
                   Network Layer Mobility: An Architecture and Survey




   Tables maintained on routers

 Mobility Binding Table
    Maintained on HA of MN
    Maps MN’s home address
     with its current COA

 Visitor List
    Maintained on FA serving an
     MN
    Maps MN’s home address to
     its MAC address and HA
     address
      Network Layer Mobility: An Architecture and Survey




Mobile IP Works

                                     MN                    Router
  S
                                                             3


                                        Home
                                        agent

  Router                             Router
    1                                  2
         Network Layer Mobility: An Architecture and Survey




    Mobile IP Works

                       move

                                                              Router
S                                                                          MN
                                                                3

                                                     Foreign agent

                        Home agent

Router                       Router                            Packets are tunneled
                                                               using IP in IP
  1                            2
                   Network Layer Mobility: An Architecture and Survey



          Mobile IP Works
           HA
                    2
                                                                                       MN



home network                                                       3           receiver
                                     Internet

                                                                        FA   foreign
                                                                             network




               1
 CN

      sender
              Network Layer Mobility: An Architecture and Survey




Security in Mobile IP

 Authentication can be performed by all parties
    Only authentication between MN and HA is required
    Keyed MD5 is the default
 Replay protection
    Timestamps are mandatory
    Random numbers on request reply packets are optional
 HA and FA do not have to share any security
  information.
               Network Layer Mobility: An Architecture and Survey




 Problems with Mobile IP

 Suboptimal “triangle” routing
   What if MN is in same subnetwork as the node to
    which it is communicating and HA is on the other
    side of the world?
      It would be nice if we could directly route packets
   Solution: Let the CN know the COA of MN
      Then the CN can create its own tunnel to MN
      CN must be equipped with software to enable it to learn the
       COA
      Initiated by HA who notifies CN via “binding update”
      Binding table can become stale
             Network Layer Mobility: An Architecture and Survey




Other Mobile IP Problems

 Single HA model is fragile
   Possible solution – have multiple HA
 Frequent reports to HA if MN is moving
   Possible solution – support of FA clustering
 Security
   Connection hijacking, snooping…
 Many open research questions
             Network Layer Mobility: An Architecture and Survey



 Mobility in IPv6

 Route Optimization is a fundamental part of
  Mobile IPv6
   Mobile IPv4 it is an optional set of extensions that
    may not be supported by all nodes
 Foreign Agents are not needed in Mobile IPv6
   MNs can function in any location without the
    services of any special router in that location
 Security
   Nodes are expected to employ strong
    authentication and encryption
 Other details…
  Mobile Ad-hoc Communication Issues in Ubiquitous Computing The Smart-Its Experimentation Platforms




Wireless issues in Ubicomp
 “Mobile Ad-hoc Communication Issues in Ubiquitous
  Computing, The Smart-Its Experimentation
  Platforms” paper does not talk about routing issues
  in ubocomp, but the wireless issues of layer 1 and 2;
  like:
        Local Broadcast
        Radio-signal strength indication and control
        Stateless vs. stateful communication
        Power issues
        Instant communication
        Unidirectional communication
        Common Time base
Need to understand the degrees
of Mobility/Adaptability
 Static

 Limited mobility
     a few nodes may fail, recover, or be moved (sensor networks)
     tough example: “throw a million nodes out of an airplane”

   Highly adaptive/mobile
     tough example: “a hundred airplanes/vehicles moving at high
      speed”
     impossible (?): “a million mosquitoes with wireless links”

   “Nomadic/viral” model:
     disconnected network of highly mobile users
     example: “virus transmission in a population of bluetooth users”

                                                 Northeastern University tutorial
 Ad hoc routing and Mobile Ad hoc routing should
  be a feature of one protocol or what…
 It is observed that size of ad hoc network be in 1 -
  2 hundreds of nodes at the most
 IPv6 be explored for Ubicopm because… layer 2,
  low-level naming, fast connection and switching,
 There is less requirement of dynamic routing in
  Ubicomp; neither static routing seems ok; need an
  efficient hybrid approach; !!! …………
 Name Resolution in group of ad hoc nodes
     ‫شکریہ‬
Any More Questions

				
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