Mobile computing Unit III MANET Notes

RAMCO INSTITUTE OF TECHNOLOGY
Department of Computer Science and Engineering
Academic Year: 2019- 2020 (Even Semester)
Degree, Semester & Branch: VI Semester B.E. CSE.
Course Code & Title: CS8601 Mobile Computing.
Name of the Faculty member: Dr.M.Kaliappan, Associate Professor/CSE
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UNIT-I INTRODUCTION 9
Introduction to Mobile Computing – Applications of Mobile Computing- Generations of
Mobile Communication Technologies- Multiplexing – Spread spectrum -MAC Protocols –
SDMA- TDMA- FDMA- CDMA
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Credit: Jochen Schiller, “Mobile Communication”, PHI, Prasant Kumar Pattnaik, Rajib
Mall, “Fundamentals of Mobile Computing”, PHI
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Objective:
 To familiarize the students with the network layer protocols and Ad-Hoc networks.
Outcome:
 Determine the functionality of MAC, network layer and identify a routing protocol for
a given Ad hoc network
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UNIT III MOBILE NETWORK LAYER
Mobile IP – DHCP – AdHoc– Proactive protocol-DSDV, Reactive Routing Protocols – DSR,
AODV , Hybrid routing –ZRP, Multicast Routing- ODMRP, Vehicular Ad Hoc networks (
VANET) –MANET Vs VANET – Security
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3.1 Overview of Mobile IP or IP packet delivery (16 marks)
• IP
– IP is responsible for routing packets to any host uniquely identified by an
assigned IP address
– Issues:
• In traditional IP addressing scheme, it needs to change IP address when
user move from one network to another network or different location
• It does not support user mobility
• Mobile IP (2 marks)
– Mobile IP was developed by Internet Engineering Task force(IETF)
– It is standard protocol that extents IP.
– It allows mobile device to stay connected with internet regardless their
locations and without change their IP address

Figure 1: Mobile IP
3.1.1 Terminologies-Mobile IP
• Mobile Node(MN)
– It is a hand held device with roaming capabilities.
– It keeps its IP address and continuously communicate with any other system in
the internet
– It can be a cell phone, PDA, laptop or a router onboard aircraft
• Home Network
– It is the network within which the device receives its IP address(Home
Address).
– It is a subnet to which a mobile node belongs to as per its assigned IP address.
– Within the home network, there is no needs for mobile IP
• Home Address(HA)
– IP address assigned to a device within its home network. The IP address on the
current network is known as home address.
• Foreign network
– It is the network in which the mobile node is operating when away from its
home network.
– The foreign network is the current subnet to which the MN visits and which is
not the home network
• Foreign Agent(FA) (2 marks)
– FA is a router in foreign network that functions as point of attachment for a
mobile node when it roams to the foreign network
• Correspondent Node(CN)
– It is router on the home network serving as a point of communication with
mobile node.
– It tunnels packets from a device on the internetwork to roaming mobile node
• Care of Address(COA) (2 marks)
– It is the address that is used to identify the present location of foreign agent.
The packets send to MN are delivered to COA
– Two steps
• Foreign agent COA

• The COA is an IP address of foreign agent
• Co-located COA
• When mobile node acquires a temporary address, that address
act as the COA(service like DHCP)
• Home Agent(HA)
– It is router that located in home network
– It provides several services to MN like maintains location registry.
– Location registry keep track of locations using current care of address of the
MN
• Agent discovery
– During call establishment it is necessary for a mobile node to determine its
foreign agent. This task is called agent discovery.
– Two discovery methods
• Agent advertisement
• Foreign agents and home agents advertise their presence
periodically using special agent advertisement messages.
• These advertisement messages list one or more COA and a
flag indicating whether it is home agent or foreign agent
• Agent solicitation (2 marks)
– If no agent advertisements are present, the mobile node must send agent
solicitations.
– MN send three solicitation message one per second as soon as it enter new
network
– Purpose
• MN is to search for a foreign agent
• the inter-arrival time is too high
• IF MN does not received a COA , MN reduce the rate of sending the
solicitation message to avoid network flooding
• Tunneling and encapsulations (2 marks)
– The packet is forwarded by HA to FA. When the packets come to the FA, it
delivers to the mobile node. This process is called tunneling.
– Tunneling establish a virtual pipe for the packets available between entry and
end point. Two functions
– Encapsulation
• Arranging a packet header and data in the data part of new packet.
– Decapsulation
• Disassembling the data part of an encapsulated packet is called
decapsulation.

Figure 2: Encapsulation and Tunnelling
3.1.2 Features of Mobile IP (2 marks)
• Transparency
– A mobile end system continue to keep its IP address and managed
transparently
– There should not be any disruption of communication with mobility
• Compatibility
– Mobile IP compatibility with existing IP address
• Security
– Provide users with secure communication over the internet
• Scalability
– It should be scalable to support billions of moving MN worldwide.
3.1.3 Advantages of Mobile IP (2 marks)
• It allows fast, continuous low‐cost access to corporate networks in remote areas where
there is no public telephone system or cellular coverage.
• It supports a wide range of applications from Internet access and e‐mail to
e‐commerce
• It support Authentication mechanism to ensure security
• Mobile IP finds local IP routers and connects automatically
3.1.4 Disadvantages of Mobile IP (2 marks)
• There is a routing inefficiency problem caused by the “triangle routing” formed by
the home agent, correspondent host, and the foreign agent.
• Security risks are the most important problem facing Mobile IP. one has to worry
about faked care‐of addresses

3.2. Key mechanism on Mobile IP (8 marks)
• Discovering the care-of-address
• Registering the care-of-address
• Tunneling the care-of-address
Figure 3: Model of Mobile IP
• Discovering the care-of-address
• MN uses discovery protocol to identify respective HA and FA
• Steps
• Agents advertise their presence by periodically broadcast the agent
advertise message
• MN receiving the agent advertise message observes whether the message
from its own HA and determines whether it is on Home network or foreign
network.
• MN does not wait for the periodic advertisement, it can send agent
solicitation message that will be responded by MA
• Process of agent advertisement
• FA send message to advertise the available care of address
• HA send advertisements to make themselves
• MN issue solicitation message to seek information
• If MN has not hear from the FA to which its current COA belongs, it takes up the
another COA
Registering the COA
• If MN discovers the home network, it continue to operate service without require
mobility service
• If a MN is on a new network , it register with foreign agent by sending registration
request which includes permanent IP address of MN and IP address of HA
• The foreign agent sends a registration request permanent IP address of MN and IP
address of FA to home agent
• HA updates the mobility binding table by associating COA of MN with its home
address when it receives the registration request
• The HA then send an acknowledgement to FA

• The FA updates its visitor list by inserting the entry for the MN and send registration
reply to MN
Figure 4: Registering the COA
How Mobile IP does works?
• Each mobile node has two IP addresses
- Permanent home address
- Care-of Address
• Home Agent maintains a mobility binding table
• Maintained on HA of MN
Maps MN’s home address with its current COA
• Foreign Agent contains a visitor list
• Maintained on FA serving an MN
• Maps MN’s home address to its MAC address and HA address

Security in Mobile IP
• Authentication can be performed by all parties
• Only authentication between MN and HA is required
• Keyed MD5 is the default
• HA and FA do not have to share any security information.
Problem in Mobile IP
• 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(unauthorized access)
Agent Advertisement
Figure 5: Agent Advertisement
Registration request format
Figure 6: Registration request format
Registration Replay format

Figure 7: Registration Replay format
3.3 Route optimization in mobile IP (8 marks)
• In Mobile IP, all the packets are to the Mobile node go through home agent. It cause
heavy traffic between HA and CN, causing latency to increase.
• Route optimization
• Enable direct notification to the CN
• Direct tunneling from CN to MN
• Binding cache maintained in CN
• Mobile IP scheme supports four message
• Binding request
• If a CN wants the current location of MN, It send binding request to
HA
• Binding Acknowledgement
• On request, HA will return an acknowledgement message after getting
the binding update
• Binding update
• This message sent by HA to CN mentioning the correct location of
MN. This message contains the permanent IP address of MN and
COA.
• Binding warning
• If a CN decapsulate a packet for a MN, but it is not a current FA, then
this node send binding warning to the HA of the MN
3.4 Dynamic Host Configuration Protocol (DHCP) (8 marks)
• DHCP was developed based on bootstrap protocol (BOOTP). BOOTP is used for
starting computer from network in case of diskless computer. It does not handle the
Mobility issue
• IETF standardized an extension of BOOTP called as DHCP.
• DHCP client and DHCP server work together to handle the roaming status and
assign IP address on a new network.
• DHCP server allocates a temporary IP address from a set of IP address.
• DHCP supports three mechanisms
• Automatic Allocation

• DHCP assigns a permanent IP address to a host
• Dynamic allocation
• DHCP assigns a permanent IP address to a host for a specific period of
time
• Manual allocation
• A host’s IP address is assigned by the network administrator, where
DHCP is used to inform the address assigned to client
Figure 8: DHCP request
Figure 9: DHCP response
DHCP operation
DHCP discover
Figure 10: DHCP discover
DHCP offer

Figure 11: DHCP offer
DHCP release IP address
DCHP RELEASE
Figure 11: DHCP Release
DHCP Message Type
Value Message Type
1 DHCPDISCOVER
2 DHCPOFFER
3 DHCPREQUEST
4 DHCPDECLINE
5 DHCPACK
6 DHCPNAK
7 DHCPRELEASE
8 DHCPINFORM

Benefits of DHCP (2 marks)
• Reliable IP address configuration.
• DHCP minimizes configuration errors caused by manual IP address configuration,
such as typographical errors, or address conflicts caused by the assignment of an
IP address to more than one computer at the same time.
• Reduced network administration.
• The efficient handling of IP address changes for clients that must be updated
frequently
3.5 MANET (2 marks)
• MANET stands for Mobile adhoc Network also called as wireless adhoc network or
adhoc wireless network that usually has a routable networking environment on top of
a Link Layer ad hoc network.
• They consist of set of mobile nodes connected wirelessly in a self-configured, self-
healing network without having a fixed infrastructure.
• MANET nodes are free to move randomly as the network topology changes
frequently.
• Each node behave as a router as they forward traffic to other specified node in the
network
Figure 12: MANET
• Host movement frequent
• Topology change frequent
• No cellular infrastructure.
• Multihop wireless links.
• Data must be routed via intermediate nodes
Figure 13: Topology change

3.5.1 How is an Ad hoc network set up without the infrastructure support? (2 marks)
• Network can be established through cooperation among the devices themselves.
• A mobile node wanting to communicate, can forward its packet to its neighbor, and
the neighbor nodes in turn forward its packets to its neighbor, and so on until it
reaches destination. so no access point that provides access control is required
• In ad-hoc networks, the nodes in the network take care of routing.
• Routing is to find the best possible path between the source and destination nodes to
transfer data.
• All the individual nodes in an ad-hoc network maintain a routing table, which
contains the information about the other nodes.
Figure 14: MANET Protocol
• MANET comprising three nodes, named S,R and D.
• In this, node S want to communicate with node D, both are not within the
transmission range and cannot communicate with each other.
• However, S and R take the help of node R to relay packets from each other.
• Protocol stack highlight that R is an independent device and not a networking
infrastructure, R is acting as Router at the network layer to facilitate communication
3.5.2 When to use an ad-hoc network? (2 marks)
– If you want to quickly set up a peer-to-peer (P2P) network between two
devices(Shareit App)
– When creating a quick temporary network
– If there is no network infrastructure set up in the area
3.5.3 Why is routing in a MANET a complex task? (2 marks)
• In a MANET, simple and efficient routing protocol is difficult like wired networks
• It is very difficult to have global identifier assigned to each node for routing.
• Nodes keep on moving and identity would have to change, which would incur
overhead.
• Route between a pair of nodes is determined, route become quickly obsolete since
they dynamically get built, some nodes forming this route move away even as the
packets are getting transmitted, thus disrupting the communication.
• The topology of the network and route between different devices changes
dynamically as nodes move away or fail.
• As a result, packet routing is a critical and complex issue.

• Consequently, a satisfactory routing protocols should be able to cope with factors
such as link breakages, and ensure message get transmitted efficiently even when
nodes move or shut down due to hardware malfunctioning and depletion of battery
energy
3.5.4 Characteristics of MANET (4 marks)
• Lack of fixed infrastructure
– A pair of nodes can communicate directly when they are in the transmission
range without central network infrastructure or they communicate using a
multi-hop communication that set up through intermediate node locate
between them.
– Based on the character alone, cellular networks and Wireless LAN cannot be
considered to be MANET
• Dynamic Topologies: Network topology which is typically multi-hops, may change
randomly and rapidly with time, it can form unidirectional or bi-directional links.
• Autonomous Behavior: Each nodes can act as a host and router, which shows its
autonomous behavior
• Energy Constrained Operation:
– As some or all the nodes rely on batteries with limited amount of energy.
– Routing process for transmission and processing cause the batteries to get
drained out.
– Energy conservation is considered to be an objective of MANET routing
protocols.
• Limited Security:
– Wireless network are more prone to security threats. A centralized firewall is
absent due to its distributed nature of operation for security, routing and host
configuration.
– Threats arise due to wireless transmission and collaborative routing
techniques.
– Eavesdropping, spoofing, denial of service attacks is possible.
– It is difficult to identify the attacker since the device keep moving and do not
having global identifier.
– Nodes are vulnerable to capture and compromise
• Less Human Intervention:
– They require minimum human intervention to configure the network; therefore
they are dynamically autonomous in nature.
• Bandwidth constrained, variable capacity links:
– Wireless links usually have lower reliability, efficiency, stability and capacity
as compared to wired network.
– Factors such as fading , noise, and interference can change the available
bandwidth of wireless link with time.
– Consequently, the bandwidth of a link can change with time

3.5.5 Advantages of MANET (2 marks)
• Cost Efficient.
• Infrastructure less.
• Autonomous Network:
– Self-configuring and self-healing nodes, does not require human intervention
• No Need of separate Routers – Each node can work as router too.
• Network Topology – Not defined.
3.5.6 Disadvantages of MANET (2 marks)
• High power consumption.
• Low in range of connectivity.
• Less secure-More prone to attacks.
• Computational power Limited.
• Resources are limited due to various constraints like noise, interference conditions,
etc.
• Lack of authorization facilities.
3.5.7 Applications of MANET (8 marks)
• Communication among portable devices
– Portable devices such as cell phone, laptop, ear phone, wrist watch connected
that reduce flexibility to share the data.
– EX: In a meeting room, if mobile devices are present, network connection
among them can be established to form MANET over which the nodes can
communicate and carry out network operations.
• Environment monitoring
– Continuous data collections from remote locations(Ad hoc sensor networks) is
considered important for several application like environment management,
road traffic monitoring, and security monitoring.
– Sensors are gathering environmental information such as rainfall, humidity,
animal data
• Military environments
– Adhoc network of military equipment allow a military setup to share
informationamong soldiers, vehicles and higher officials.
• Emergency application
– MANET can deployed easily in emergency situation like search and rescue
operation after natural disaster(Earthquake, flood)
3.6 MANET Design issues (8 marks)
• Network size and node density
• Connectivity
• Network topology
• User traffic
• Operational environment
• Energy constraint

3.6.1 Network size and node density
• Network size and node density parameters need to be considered to design MANET
routing protocols.
• Network size refers to the geographical coverage area of the network
• Network density refers to the number of nodes in a geographical area.
• For large network, Clustering is essential to reduce communication overhead.
3.6.2 Connectivity
– It refers to the number of neighbor it has or link between two nodes.
– The link capacity is denotes the bandwidth of the link
– In MANET, both number of neighbors and the link capacity (bandwidth) to different
neighbor may vary significantly
3.6.3 Network topology
• Network topology denotes the connectivity among the nodes.
• Mobility affect the Network topology. Due to mobility, new link can form and some
link gets dissolved.
• Node can become inoperative due to drained batteries, or hardware failure that cause
change in Network topology.
• The rate at which the Network topology change need to be considered to design
effective network
3.6.4 User traffic
• The design of a MANET is carried out based on the anticipated node density, average
rate of mobility and the expected traffic.
• Various specific traffic are considered to improve the performance.
• Bursty traffic ( Continuous data transfer)
• Large packets sent periodically
• Combination of above two types of traffic
3.6.5 Operational Environment
• The Operational Environment of a MANET is either urban, rural and maritime which
support line of sight (LOS) communication.
• There can be a difference in node density and mobility in different operational
environments, requiring different design of MANET to suit an operational
environment

Figure 15: Line of sight
3.6.6 Energy constraint
• In a MANET, the nodes themselves store and forward packets.
• The additional role of nodes as router in which it perform router workload that leads
battery drainage.
3.7 Routing
– Routing is the process of find best path in a network along which to send network
traffic
3.7.1 Why traditional routing protocol is not suitable for ad hoc network? (2 marks)
• In traditional networks, routes to nodes uniquely identified based on subnet structure
encoded in IP.
• In a MANET, Each node needs to have routing capability and need to participate in
routing to keep the network operational. The route at various nodes quickly becomes
obsolete due to mobility and network topology change.
• Whenever there is an incoming packet in a MANET, Forward the packet to the next
node (hop).
3.7.2 Routing in MANET Vs Routing in Traditional network (2 marks)
• In MANET, each node act as a router, whereas ordinary node in traditional network
do not participate in the routing process.
• In a MANET, topology is dynamic, because of node mobility, but it is static in
traditional networks. The routing table in a MANET become obsolete, making routing
process complicated.
• In MANET, IP-based addressing scheme does not work because of node mobility,
simple IP-based addressing scheme deployed in wired network.
• Power efficiency is an issue in MANETs, while it is normally not an issue in
traditional networks
• There is limited physical security in a MANET compared to a traditional network
3.7.3 Types of Communications
• Unicast
– A message is sent to single destination node
– Browsing a website, Downloading a file from a FTP Server
• Multicast
– A message is sent to a selected subset of the nodes. Ex: IPTV, e-mail message
to a mailing list. Tele conferencing and video conferencing
• Broadcast
– A message is sent to all the nodes

– a radio station broadcasts a signal to many listeners, and
– digital TV subscribers receive a signal that is broadcast by their TV provider
Figure 16: Types of Communications
3.7.4 Popular MANET Routing Protocols (2 marks)
Figure 17: MANET Routing Protocols
3.7.4.1 Proactive (table driven) protocol (2 marks)
• In this type of routing protocol, each node maintains routing tables to every other
node.
• Routing tables are updated periodically when change in the network topology.
• This protocol generates a large number of control messages to keep the routing table
up to date that lead routing overhead and take large bandwidth.
• A networks with large number of nodes and high mobility node, the control messages
may consume almost entire bandwidth.
• It is not suitable for large network.
• Examples (2 marks)
– Distance vector (DV) protocol,
– Destination Sequenced Distance Vector (DSDV) protocol,
– Wireless Routing protocol,
– Fisheye State Routing (FSR) protocol

3.7.4.2 Reactive (on-demand) protocols (2 marks)
• Each node in a network discovers a route only when required
• It floods a control message to determine the route when the node does not have
knowledge about route to specific destination.
• It reduced the large overhead incurred by the proactive routing protocols
• The efficiency is achieved by maintaining a active routes only and avoid large number
of route update message
• EX: (2 marks)
– Dynamic source routing(DSR)
– Ad hoc On-demand distance vector routing(AODV)
3.7.4.3 Hybrid routing protocol (2 marks)
• It is a combination of best features of both proactive and reactive protocols.
• It proactively maintaining routes to nearby nodes and determining routes to far away
node when required using route discovery strategy.
• Example (2 marks)
– Zone based routing(ZRP) protocol
3.7.5 Destination-Sequenced Distance-Vector Routing Protocol (DSDV) (16 marks)
• It use Table driven (proactive) approach to packet routing
• It extends the distance vector protocol of wired networks which makes use of
distributedBellman-Ford routing algorithm
• Improvement – Avoidance of routing loops through the use of a sequence numbering
• Each node maintains routing information to all known destinations
• The routing information is updated periodically and whenever there is a change
3.7.5.1 Sequence numbering system
• Allows mobile nodes to distinguish stale routes from new ones.
• A node update its table only if the received routing table with highest sequence
number.
• It avoids routing loops
3.7.5.2 DSDV uses two types of route updates
• Full Dump
– Full dump Packet carries all available route information
– Requires multiple Network protocol data unit(NPDUs) to be transmitted
infrequently if the routing table is large.
• Incremental
– Small incremental packets are used to disseminate only the routing
information that has changes since the latest full dump sent out
– Hence, incremental packets only consume a fraction of the network resources
compared to a full dump
3.7.5.3 Steps in the operation of DSDV
• Each node collects route information from all its neighbours
• The node determines the shortest path to the destination based on the gathered
information
• A new routing table is generated

• The node broadcasts this routing table to its neighbours. On receipt of neighbours, the
neighbour nodes recomputed the respective routing table.
• This process continues till the routing information becomes stable.
3.7.5.4 Route advertisement
• Advertise to each neighbor own information.
• Route Table Entry contains
• next hop for a destination,
• number of hops to reach the destination(metric),
• a sequence number
• Install time
3.7.5.5 Rule to set sequence number
• On each advertisement increase own destination sequence number(even number)
• If a node is no more reachable, increase own sequence number by 1(odd number) and
set metric as ∞
3.7.5.6 Route selection
• Select a route with high sequencing number that ensure the latest routing information
from destination
• Select the route with better metric when sequence numbers are equal
Figure 18: DSDV route selection
3.7.5.7 Link failure
In case of link failures, neighbors increment the sequence number of destination with
the failed link by 1 – odd sequence numbers

Figure 18: Link failure
3.7.5.8 Advantages of DSDV(2 marks)
– The availability of paths to all destinations in network always shows that less
delay is required in the path set up process.
– All available wired network protocol can be useful to ad hoc wireless networks
with less modification
3.7.5.9 Shortcoming (Disadvantage) of DSDV protocol (2 marks)
• It denies a node from going into sleeping mode.
• There is traffic overhead, even if there is no change in network topology.
• Nodes maintain routes which they may never use.
• DSDV is not suitable for highly dynamic or large scale networks.
• DSDV requires a regular updates of its routing tables, which uses up battery power
and a small amount of bandwidth even when the network is idle
3.7.5.10 Exercise
Construct the routing table at node 4 using DSDV routing

Answer
3.7.6 On demand routing protocol (2 marks)
On-demand routing protocols execute the path-finding process and exchange routing
information only when a path is required
• Ex:
– Dynamic source routing(DSR)
– Ad Hoc On-Demand Distance-Vector Routing Protocol (AODV)
– Temporally Ordered Routing Algorithm (TORA)
– Location-Aided Routing (LAR)
– Associativity-Based Routing (ABR)
– Signal Stability-Based Adaptive Routing Protocol
– Flow-Oriented Routing Protocol
3.7.6.1 Dynamic source routing (DSR) (16 marks)
• DSR is an on-demand protocol designed to restrict the bandwidth consumed by
control packets in ad hoc wireless networks by eliminating the periodic table-update
messages.
• The major difference between this and the other on-demand routing protocols is that it
is beacon-less and hence does not require periodic hellopacket (beacon)
transmissions, which are used by a node to inform its neighbors of its presence.
• DSR protocol is suitable in MANET having small diameter of about 5 to 10
hops(small network) and low mobility
3.7.6.1.1 Source routing
• A technique in which the sender of a packet determines the complete sequence of
nodes (route) through which a packet has to travel.
• Sender explicitly records route in the packet’s header. This makes it easy for each
node in the path to identify the next node to which it should transmit.
• Each node maintains a sequence counter called request id to identify the last
request it has generated
3.7.6.1.2 Routing cache
• Each mobile node (using this protocol)
• Maintains a routing cache
• Contains a list of all routes that the node has learnt
• Whenever a node finds a new route, it adds the new route to its routing cache.

3.7.6.1.3 DSR works in two phases
• Route discovery
• Route maintenance
3.7.6.1.4 Route discovery
• Allows any node to dynamically discover the route to any destination in the ad hoc
network
• When a node has data packet to send,
• It first checks its own routing cache.
• If it finds a valid route in its own routing cache, It sends out packet using this
route
• Otherwise,
• It initiate a route discovery process by broadcasting a route request
packet(RREQ) to all its neighbors
Figure 19: Route discovery
• The route request packet contains the source address, the request id and a route
record.
• < source address, request id , route record>
• < N1, 005, N1-N3-N5>
3.7.6.1.5 Route Record
– The sequence of hops traversed by the request packet, before reaching the
destination.
– The sequence of hops prevent loop formations
– It avoid multiple transmissions of the same RouteRequestby an intermediate
node that receives it through multiple paths

3.7.6.1.6 What does a node do on receiving a route request packet? (2 marks)
• A node upon getting a route request packet does the following,
– If a packet does not have the required route in its cache, it forwards the packet
to all its neighbours.
– A node forwards a route request message only if it has not seen it earlier(using
request id), and if it is not the destination.
• The route request packet initiates a route reply when
– the destination node is reached
– Or when an intermediate node that knows the route to the destination is
reached.
• When the route request message reaches the destination,
– This information is piggybacked on to the route reply message that contains
the path information and sent to the source node
Figure 20: Route discovery-route reply
3.7.6.1.7 Route maintenance
• Whenever a node detects that one of its next hop neighbor link is broken
– It sends back a route error packet
– route error packet containing
• Its own address
• the address of the hop that is not working

Figure 21: Route maintenance
• The source node on receiving the RouteError message,
– If it has another route to the destination,
• it starts to retransmit the packet using the alternative route
– Else
• The cached entries at the intermediate nodes and the source node are
removed
• It initiates the route discovery process again.
3.7.6.1.8 Route Optimization in DSR (8 marks)
• Route Shortening
– Routes may be shortened if one of intermediate nodes become unnecessary
– The vertical arrow shows the one –hop destination e.g. B, C, D, with arrow on
B means B is the destination
– If C overhears that A is forwarding a packet to B that is destined to C, then
– C sends a “Gratuitous” message (Its RREP message) to original sender A.
– The RREP informs A to route packets as A-C-D instead of AB-C-D
Figure 22: Route shortening
• Route Request - Hop Limits
– Each RREQ message contains a field called hop limit
– Hop limit controls the propagation of RREQ i.e. how many intermediate nodes
are allowed to forward the RREQ
– Each receiving node decrements the hop-limit by 1 before forwarding.
– RREQ is not forwarded & is discarded by node when this limit becomes zero
even before reaching the destination.

– A RREQ with hop-limit zero will determine that the source is the one hop
neighbor
– If no RREP is received within a timeout period, a new RREQ is sent by the
sender with no hop-limit
– Variations of this theme are sending RREQ with hop-limits of 0, 2, 4 etc
3.7.6.1.9 Advantages of DSR (2 marks)
• The protocol performs well in static and low-mobility environments.
• The nodes don’t need to exchange the routing table information periodically – reduce
bandwidth overhead associated with the protocol.
• The intermediate nodes utilize the route cache information efficiently to reduce the
control overhead
3.7.6.1.10 Disadvantages of DSR (2 marks)
• The route maintenance mechanism does not locally repair a broken link.
• The connection setup delay is higher than in table-driven protocols.
• The performance degrades rapidly with high mobility of nodes.
• Also, considerable routing overhead is involved due to the source-routing mechanism
employed in DSR.
• This routing overhead is directly proportional to the path length
• Stale route cache information could result in inconsistencies during the route
reconstruction phase.
3.7.7 Ad hoc On-demand distance vector (AODV) (16 marks)
• AODV uses an on demand approach for finding routes only when it is required by a
source node for transmitting data packets.
• In AODV, the source node and intermediate nodes store the next-hop information
corresponding to each flow for data packet transmission
• It uses a destination sequence number ( DestSeqNum) to determine an up-to-date path
to the destination.
• A node updates its path information only if the DestSeqNum of the current packet
received is greater than the last DestSeqNum stored at the node
• Routing table
• AODV utilizes routing tables to store routing
destination
addr
next-hop
addr
destination sequence hop count life time
Routing procedure
• Route Discovery
• Route maintenance
3.7.7.1 Route Discovery
• If a node wants to send a packet to some destination. At first, it checks its routing
table to determine whether it has a current route to the destination or not.

– If yes, it forwards the packet to next hop node of the route.
– If no, it initiates a route discovery process
• It begins with the creation of a RouteRequest (RREQ) packet. Broadcasting is done via
flooding.
• Broadcast ID gets incremented each time a source node uses RREQ.
Broadcast ID and source IP address form a unique identifier for the RREQ
Figure 23: RREQ packet
• DestSeqNum indicates the freshness of the route that is accepted by the source.
• When an intermediate node receives a RouteRequest, it either forwards it or prepares a
RouteReplyif it has a valid route to the destination.
• The validity of a route at the intermediate node is determined by comparing the sequence
number at the intermediate node with the destination sequence number in the
RouteRequestpacket
• If a RouteRequest is received multiple times, which is indicated by the BcastID-SrcID
pair, the duplicate copies are discarded.
• All intermediate nodes having valid routes to the destination, or the destination node
itself, are allowed to send RouteReply packets to the source.
• A timer is used to delete this entry in case a RouteReplyis not received before the timer
expires
Figure 23: RREP packet format
• Node S needs a routing path to node D.
• Node S creates a RREQ packet
• RREQ [D’s IP addr, seq#, S’s IP addr, seq#, hopcount]
• Node S broadcasts RREQ to its neighbors

• Node A rebroadcasts RREQ to all its neighbors
• Since, node C known a route to D. Node C creates a RREP packet and unicasts RREP
to A.
• Set forward path in node C’s routing table
• Node A creates a RREP packet and unicasts RREP to S.
• Set forward path in node A’s routing table
• Set forward path in node S’s routing table

3.7.7.2 Route maintenance (Path broken due to host mobility)
• If intermediate nodes or the destination move.
– The next hop links break.
– Routing tables are updated for the link failures.
– All active neighbors are informed by RouteError (RRER) packet.
• When a source node receives an RRER, it can reinitiate the route discovery process.
• It can be also dealt with by a local fix scheme
• Assume link between C and D breaks.
– Node C invalidates route to D in route table.
– Node C creates RRER packet and sends to its upstream neighbors.
– Node A sends RRER to S.
– Node S rediscovers route if still needed
3.7.7.3 Significance (Advantages) of AODV (2 marks)
 The AODV uses a combination of a DSR and DSDV mechanism.
 Route is calculated on demand, just as it is in DSR via route discovery process.
 However, AODV maintains a routing table where it maintains one entry per
destination unlike the DSR that maintains multiple route cache entries for each
destination.
 AODV provides loop free routes while repairing link breakages but unlike DSDV, it
doesn’t require global periodic routing advertisements
3.7.7 .4 Disadvantages (2 marks)
 Intermediate nodes lead to inconsistent routes if the source sequence number is very
old.
 The periodic beacon packet leads to unnecessary bandwidth consumption.

 Also, multiple RouteReply packets in response to a single RouteRequest packet can
lead to heavy control overhead.
3.7.7.5 DSR VS AODV (2 marks)
DSR AODV
DSR has less routing
overhead
DSR has high routing overhead
DSR is based on a source
routing mechanism
AODV uses a combination of DSR and DSDV
mechanisms
It suitable for small network
with low mobility
It suitable for large network with high mobility
DSR has less frequent route
discovery processes
AODV has less frequent route discovery processes
3.7.8 Zone routing protocol (ZRP) (8 marks)
• ZRP is a hybrid protocol. It incorporates the merits of both on demand and proactive
routing protocols.
• Routing Zone is a cluster.
• The zone is defined as a collection of nodes whose minimum distance (in hops) from
the node that is called the “zone radius”
Two phase
• Intra-Zone Routing Protocol (IARP)
• Inter-Zone Routing Protocol (IZRP)
3.7.8 1 Intra-Zone Routing Protocol (IARP)
• Could be any link state or distance vector routing protocol.
• Maintained only within a zone
• Each node contains route to all nodes within the zone
3.7.8 2 Inter-Zone Routing Protocol (IZRP)
• On demand route discovery employs on IZRP
• The source node sends a RREQ packet to border nodes of its zone containing its own
address, destination address and sequence number
• Hello messages are required in order to ensure that neighbors are still present. This
helps detect link failures
• If the IARP cannot find the destination, i.e., the destination is beyond a node’s zone,
the IERP is invoked. • It is a reactive protocol that enables the discovery of the
destination
• The node would direct the query message out only to its peripheral nodes

Figure 23: ZRP
3.7.9 Multicast routing- ODMRP (8 Marks)
• The protocol, termed ODMRP (On-Demand Multicast Routing Protocol), is a mesh-
based, multicast scheme and uses a forwarding group forwards the multicast packets via
flooding.
• It applies on-demand procedures to dynamically build routes and maintain multicast
group membership.
• Types
• Tree based multicast routing
• Mesh based multicast routing
Figure 24: Tree based multicast routing Figure 25: Mesh based multicast routing
• In ODMRP, group membership and multicast routes are established and updated by the
source on demand.
• Two phases
– request phase

– reply phase
3.7.9.1 Request phase
Figure 26: Request phase-JREQ
3.7.9.2 Reply phase
Receiver nodes R1, R2, R3 sent the Joining Reply message to corresponding senders
such as S1 and S2. I2 receives three JOIN TABLES from the receivers R1,R2 and R3, it
broadcasts the JOIN TABLE only once because the second and third table arrivals carry no
new source information
Figure 27: Reply phase- JREP
• Multicast source periodically broadcasts a member advertising packet to the entire
network, called a JOIN REQUEST.
• This periodic transmission refreshes the membership information and updates the
route as follows.
– When a node receives a non-duplicate JOIN REQUEST, it stores the upstream
node ID and rebroadcasts the packet.
– When the JOIN REQUEST packet reaches a multicast receiver, the receiver
creates or updates the source entry in its Member Table

• While valid entries exist in the Member Table, Receiver JOIN TABLES are
broadcasted periodically to the neighbors.
• When a forwarding node receives a JOIN TABLE, it checks if the next node ID of
one of the entries matches its own ID. If it does, It sets the FG Flag and broadcasts its
own JOIN TABLE the node realizes that it is part of the forwarding group.
• It then broadcasts its own JOIN TABLE by each forwarding group member until it
reaches the multicast source via the shortest path.
• This process constructs the routes from sources to receivers and builds a mesh of
nodes, the forwarding group.
3.7.9.3 Soft State approach or Route maintenance
– In ODMRP, no explicit control packets need to be sent to join or leave the group.
– If a multicast source wants to leave the group, it simply stops sending JOIN
REQUEST packets since it does not have any multicast data to send to the group.
– If a receiver no longer wants to receive from a particular multicast group, it
removes the corresponding entries from its Member Table and does not transmit
the JOIN TABLE for that group.
– Links break
• Receiver: receives new J-Q and replies with J-R
Advantages (2 marks)
• No explicit control message is required to leave the group.
• The connectivity make ODMRP more scalable for large networks and more stable for
mobile wireless networks
Disadvantages (2 marks)
• Intermittent connectivity
• Frequent tree reconfiguration
• Traffic concentration
3.8 VANET (2 marks)
• A Vehicular Ad Hoc Network (VANET) is s special types of MANET in which
automobiles form a network.
• VANETs were initially introduced for vehicle of police, ambulance and fire brigades.
• Communication range between vehicles is about 100 to 300 metres.
• Multi hop communication is used in large networks.
• Nodes in the vehicular environment are much more dynamic because most cars
usually are at a very high speed and change their position constantly.
• The high mobility also leads to a dynamic network topology
3.8.1 VANET architecture (8 marks)
• VANET follows the IEEE 1471-2000 and ISO/IEC 42010 architecture standard
guidelines.
• CAR-2-CAR communication consortium (C2C-CC) is the major driving force for
vehicular communication system called CAR-2-X communication system
• VANET architecture divided into three domains:
– Mobile domain

– Infrastructure domain
– Generic domain
Figure 28: C2C-CC reference architecture
3.8.2 Mobile domain consists of two parts:
– vehicle domain
– Mobile device domain.
– The vehicle domain comprises all kinds of vehicles such as cars and buses.
– The mobile device domain comprises all kinds of portable devices like
personal navigation devices and smartphones
• The in-vehicle domain is composed of an on-board unit (OBU) and one or multiple
application units (AUs).
• The connections between them are usually wired and sometimes wireless.
• However, the ad hoc domain is composed of vehicles equipped with OBUs and
roadside units (RSUs).
• An OBU can be seen as a mobile node of an ad hoc network and RSU is a static node.
• An RSU can be connected to the Internet via the gateway; RSUs can communicate
with each other directly or via multi hop as well.
• There are two types of infrastructure domain access, RSUs and hot spots (HSs).
• OBUs may communicate with Internet via RSUs or HSs.
• In the absence of RSUs and HSs, OBUs can also communicate with each other by
using cellular radio networks (GSM, GPRS, UMTS, WiMAX, and 4G)

3.8.3 Vehicular communication architecture
• In-vehicle communication, it refers to the in-vehicle domain. In-vehicle
communication system can detect a vehicle's performance , driver's fatigue and
drowsiness, which is critical for driver and public safety.
• Vehicle-to-vehicle (V2V) communication can provide a data exchange platform for the
drivers to share information and warning messages, so as to expand driver assistance.
• Vehicle-to-road infrastructure (V2I) communication. V2I communication enables
real-time traffic/weather updates for drivers and provides environmental sensing and
monitoring.
• Vehicle-to-broadband cloud (V2B) communication means that vehicles may
communicate via wireless broadband mechanisms such as 3G/4G. As the broadband
cloud contain more traffic information and monitoring data, this type of
communication will be useful for vehicle tracking.
3.8.4 Application of VANETs (2 marks)
• VANET helps driver to get advance information and warning from a nearby
environment
– Ex: advance notification about accident, road condition
• VANET help disseminate geographical information to driver for continuous driving.
– Driver would notified about nearby food mall, petrol bulk , map display
• Driver may participate in an office video conference session.
• Traffic information systems, which use VANET communication to provide up-to-
the minute obstacle reports to a vehicle's satellite navigation system
3.8.5 MANET Vs VANET (2 marks)
MANET VANET
MANET is a collection of mobile node that
communicate with each other without
infrastructure
A Vehicular Ad Hoc Network (VANET) is s
special types of MANET in which automobiles
form a network.
Node mobility is dynamic ally change Node mobility in VANET is constrained to
road topology
Power is major constrain Battery power is available in VANET
3.9 Security issues in MANET (8 marks)
• Dynamic topology changes and inherent wireless communication make MANET
vulnerable to different types of attack
• At the physical layer, an intruder can cause jamming or overload the available
resources beyond their capabilities.
– Wireless link get jammed
– Batteries of node get depleted
• At the network layer, Attacker disturb the operation of routing protocol by modifying
the header of the packet.

• The intruder may insert spurious information while routing packets cause erroneous
routing table updates and leading to misrouting
• Destructive attacks can be orchestrated by Trojan horse and viruses
3.9.1 Characteristics of MANET that can be exploited to cause security vulnerability (5
marks)
• Lack of physical boundary
– Each mobile nodes functions as router and forward packets from other nodes. As a
result , network boundary is not defined, making it difficult to deploy firewall or
monitor the incoming traffic
• Low power RF transmission
– Malicious node can continuously transmit or monopolise the physical medium that
cause the neighbour node to wait long time.
– Signal jamming can lead to denial of service attack
• Limited computational capabilities
– Node usually have limited computational capabilities. It became difficult to
deploy computational security solutions such as public cryptographic system
• Limited power supply
– Since nodes rely on battery power. An attacker might attempt to exhaust batteries
by unnecessary transmission or excessive computations to be carried out.
3.9.2 Characteristics of secure ad hoc networks (2 marks)
– Availability
• It should be able to survive denial of service attack.
– Confidentiality
• It should protect information by preventing its access by unauthorized
users
– Integrity
• It should guarantee that no transferred information has been tampered with
– Authentication
• It should guarantee the true identity of a peer node
– Non-repudiation
• It should ensure that a node having sent a message, cannot deny it
3.9.3 Security attack in MANET (8 marks)
– Security attack
• Passive attack
• Active attack
– Passive attack
• The purpose is solely to gain information about the target and no data is
changed on the target without affect the function of the network.
• It becomes difficult to identify since it do not have any symptoms.
• It can be reduced by encryption technique.
– Active attack
• It destructive and disturb the functions of networks

Passive attack Active attack
Snooping, eavesdropping , traffic analysis,
monitoring
Wormhole, black hole, grey hole, resource
consumption, routing attack
Different attacks at different layer of MANET protocol stack
Layer Attacks
Application layer Malicious node, repudiation, data corruption,
Transport layer Session hijacking, SYN flooding
Network layer Worm hole , black hole, fabrication attack
Data link layer Resource consumption
Physical layer Traffic analysis, monitoring, disruption, jamming,
eavesdropping
Multilayer Denial of service, impersonation , replay
• Routing loop
– By sending an tampered routing packets, an attacker can create a routing loop
– It consume more bandwidth and power, packets send endlessly
• Malicious node attack
– It can be a virus, worm, spyware.
– An attacker propagate malicious code that slow down the system
• Repudiation system
– It refers a denial of participation in communication
– Attacker deny bank transaction
• SYN flooding
– An attacker creates a large number of opened TCP connections with victim
node by sending SYN packet.
– It cause over the TCP table
• Session hijacking
– All communications are authenticated only beginning of the communication
– The attacker spoof the IP address of a node that has just started the session and
hijack the session from the victim and perform DOS
• Fabrication attack
– AODV routing, a node detects a broken link, Route error message sent to
source.
– A malicious node sends a false route error packet
• Black hole attack
– A node setup a route to some destination via itself. This node form a black
hole, to which data packets entered but never leave

• Grey hole attack
– The attacker selectively drops some kind of packets.
– This attacker forward the routing packet but not the data packets
• Partitioning
– The attacker partition the network by causing some nodes to split up from
other nodes.
• Black list
– In ad hoc routing protocol, keep a list of malicious node that is called black
list.
– An attacker add the normal node into black list
• Worm hole attack
– In a worm hole attack, direct link is established between the two nodes
referred as worm hole.
– Through the worm hole, one node eavesdrop message at one end, and tunnel
them through worm hole link to other node. Attacker use for DoS attack
• Dropping routing traffic or selfish attack
– It is possible that a node act as selfish and process only the routing information
that is related to itself or conserve the energy
3.9.3 Security measure at different protocol layers (2 marks)
Layer security measures incorporated
Application layer Detection and prevention of virus , worms , malicious code by code
analysis
Transport layer Secure and authenticating end-to end communication by encryption
Network layer Use of authentication measures and keep track of trusted nodes
Data link layer Use of spread spectrum transmission and directional antenna
Physical layer Maintain the secrecy

Mobile computing Unit III MANET Notes

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Mobile computing Unit III MANET Notes