1. Ad Hoc Networks
BY
DARPAN DEKIVADIYA
09BCE008
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING
AHMEDABAD-382481
April 2011

2. Ad Hoc Networks
Seminar
Submitted in partial fulfillment of the requirements
For the degree of
Bachelor of Technology In Computer Engineering
By
DARPAN DEKIVADIYA
09BCE008
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING
AHMEDABAD-382481
April 2011

3. Certificate
This is to certify that the Seminar entitled ”Ad Hoc Networks” submitted by DARPAN
DEKIVADIYA(09BCE008), towards the partial fulfillment of the requirements for the degree
of Bachelor of Technology in Computer Engineering of Nirma University of Science and
Technology, Ahmedabad is the record of work carried out by him under my supervision and
guidance. In my opinion, the submitted work has reached a level required for being accepted
for examination. The results embodied in this Seminar, to the best of my knowledge, haven’t
been submitted to any other university or institution for award of any degree or diploma.
Prof.Vijay Ukani Prof. D. J. Patel
Assistant Professor, Professor and Head,
Dept. of Computer Science & Engg., Dept. of Computer Science & Engg.,
Institute of Technology, Institute of Technology,
Nirma University, Ahmedabad Nirma University, Ahmedabad
Prof. Manish Chaturvedi
Guide and Assistant Professor,
Institute of Technology,
Nirma University, Ahmedabad
iii

4. Abstract iv
Now a days in the many areas of the network types of the network are used.Ad hoc
network are one of the network. It is the mobile no de network and which all are connected
with wireless link.There are many types of the ad hoc network.The most useful ad hoc
network is in the security purpose.Routing algorithm is same as the wired network but some
variation are made in it.There is two types table-driven and on-demand protocols for the
routing in ad hoc network.
iv

5. Acknowledgements v
I would like to express my heartfelt gratitude to Prof. Manish Chaturvedi,Professor in
Department of computer science and engineering for her valuable time and guidance that
made the seminar project work a success. Thanking all my friends and all those who had
helped me in carrying out this work. I am also indebted to the library resources centre and
interest services that enabled us to ponder over the vast subject of ”Ad Hoc Networks”.
- DARPAN DEKIVADIYA
09BCE008
v

6. Contents
Abstract iv
Acknowledgements v
1 Introduction 1
1.1 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Major Issues and Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Ad Hoc versus Infrastructure based Networks . . . . . . . . . . . . . . . . . 3
2 Architecture of Ad Hoc Network 4
2.1 IEE 802.11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Ad Hoc Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1 Medium Access Control Layer . . . . . . . . . . . . . . . . . . . . . . 5
2.2.2 Basic DFWMAC-DCF using CSMA/CA . . . . . . . . . . . . . . . . 6
2.2.3 DFWMAC-DCF with RTS/CTS . . . . . . . . . . . . . . . . . . . . 7
3 Routing In Ad-Hoc Networks 8
3.1 Requirement of the Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 General Issues for Ad Hoc Network Routing . . . . . . . . . . . . . . . . . . 9
4 Routing Protocols 10
4.1 Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1.1 Based on the routing information update mechanism . . . . . . . . . 10
4.1.2 Based on the use of Temporal information for Routing . . . . . . . . 10
4.1.3 Based on Routing Topology . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.4 Based on the Utilization of specific Resources . . . . . . . . . . . . . 11
4.2 Proactive or table-driven routing protocols . . . . . . . . . . . . . . . . . . . 11
4.2.1 Destination sequenced distance-vector protocol . . . . . . . . . . . . . 11
4.2.2 Wireless routing protocol . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.2.3 Cluster head Gateway Switch Routing protocol . . . . . . . . . . . . 14
4.3 On-Demand routing protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3.1 Dynamic Source Routing Protocol . . . . . . . . . . . . . . . . . . . . 15
4.3.2 Ad Hoc On-Demand Distance Vector Routing Protocol . . . . . . . . 17
4.4 Hybrid routing protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.4.1 Zone Routing Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 19
vi

7. Chapter 1
Introduction
In computer networking, an Ad Hoc Network refers to a network connection established
for a single session and does not require a router or a wireless base station.
Mobile nodes that are within each other’s radio range communicate directly via wireless
links that. Here mobile nodes are cause the different topology in the networks.
In the above diagram nodes A and D have direct connection between them. In the first
radio station shows that in same radio stations both A and D are directly connected. But
as the show in the second radio station, when nodes d are goes away from the these station
the connection link was broken between them. But still A and D are connected via nodes
A-B-C-D. So this type of networks connections is held in ad hoc networks. So it is widely
used in the military application and other temporary networks. For example, military units
(e.g., soldiers, tanks, or planes), equipped with wireless communication devices, could form
an ad hoc network when they roam in a battlefield. Ad hoc networks can also be used for
emergency, law enforcement, and rescue missions.
1

8. 1.1 Characteristics
ˆ Operating without a central coordinator
ˆ Multi-hop radio relaying
ˆ Frequent link breakage due to mobile nodes
ˆ Constraint resources (bandwidth, computing power, battery lifetime)
ˆ Instant deployment
1.2 Applications
ˆ Military applications
ˆ Collaborative computing
ˆ Emergency rescue
ˆ Mesh networks
ˆ Wireless sensor networks
ˆ Multi-hop cellular networks
ˆ Wireless Community Network
1.3 Major Issues and Challenges
ˆ Hidden terminal problem
ˆ Exposed terminal problem
ˆ Channel efficiency
ˆ Access delay and fairness
ˆ Differential service
ˆ Realistic mobility modeling
ˆ power-aware routing
ˆ Constructing virtual backbone
ˆ Distinguish contention, packet drop, and noise errors
ˆ Security
ˆ Efficient multicasting
2

9. 1.4 Ad Hoc versus Infrastructure based Networks
In infrastructure based Networks , communication typically takes place only between the
wireless nodes and the access point , but not directly between the wireless nodes.
Infrastructure Networks contain special nodes called access points(APs), which are con-
nected via existing networks. APs are special in the sense that they can interact with wireless
nodes as well as with the existing wired network. The other wireless nodes , also known as
mobile stations , communicate via APs. The APs also act as bridges with other networks.
Ad hoc LANs do not need any fixed infrastructure. These networks can be set up on the
fly at any place. Nodes communicate directly with each other or forward messages through
other nodes that are directly accessible. The design of infrastructure based networks is
simpler because most of the network functionality lies within the access point ,whereas the
client can remain quite simple.
In Ad hoc networks, the complexity of each node is higher because every node has to
implement medium access mechanisms to provide certain quality of service. Infrastructure
based networks lose some of the flexibility which wireless networks can offer. They cannot
be used for disaster relief in cases where no infrastructure is left, where ad hoc networks can
be used.
3

10. Chapter 2
Architecture of Ad Hoc Network
The architecture of ad hoc network can be explained by IEEE 802.11 standards.
2.1 IEE 802.11
IEEE 802.11 is a set of IEEE standards that govern wireless networking transmission
methods.
2.1.1 History
802.11 technology has its origins in a 1985 ruling by the U.S. Federal Communications
Commission that released the ISM band for unlicensed use. In 1991 NCR Corporation (now
Alcatel-Lucent and LSI Corporation) invented the precursor to 802.11 in Nieuwegein, The
Netherlands. The inventors initially intended to use the technology for cashier systems; the
first wireless products were brought on the market under the name WaveLAN with raw data
rates of 1 Mbit/s and 2 Mbit/s.
Vic Hayes, who held the chair of IEEE 802.11 for 10 years and has been called the
”father of Wi-Fi” was involved in designing the initial 802.11b and 802.11a standards within
the IEEE.
In 1992, the Commonwealth Scientific and Industrial Research Organisation (CSIRO)
obtained a patent in Australia for a method of wireless data transfer technology based on
the use of Fourier transforms to ”unsmear” the signal. In 1996, CSIRO obtained a patent
for the same technology in the US. In April 2009, 14 tech companies selling Wi-Fi devices,
including Dell, HP, Microsoft, Intel, Nintendo, and Toshiba, agreed to pay CSIRO 250 dollors
million for infringements on the CSIRO patents
Mobile terminals can operate in two modes under IEEE 802.11 :
ˆ Infrastructure Mode
ˆ Ad Hoc Mode
4

11. 2.2 Ad Hoc Mode
IEEE 802.11 only covers PHY layer and MAC layer
PHY layer is subdivided into
ˆ Physical Layer Convergence Protocol (PLCP)
ˆ Physical Medium Dependent sub layer (PMD)
PHY management include channel tuning and responsible for higher layer functions (e.g.
control of bridging). MAC management controls authentication mechanism and power man-
agement to save battery power.
2.2.1 Medium Access Control Layer
The basic servies provided by the MAC layer are the mandatory ”Asynchronous data
service” and an optional ”Time bounded service”. while 802.11 only offers the Asynchronous
data service in ad-hoc mode,both service types can be offered using an Infrastructure based
network.
The following three mechanisms for IEEE 802.11 : The mandatory basic method based
on a version of CSMA/CA, an optional method avoiding the hidden terminal problem,and
finally a contention free polling method for time bounded service. The first two methods are
also summarized as ”Ditributed Coordination Function(DCF)”, the third method is called
”Point Coordination Function(PCF)”. The MAC Mechanisms are also called ”Distributed
Foundation Wireless Medium Access Control(DFWMAC)”.
5

12. 2.2.2 Basic DFWMAC-DCF using CSMA/CA
The mandatory access mechanism of IEE 802.11 is based on Carrier Sense Multiple
Access with Collision Avoidance(CSMA/CA) ,which is random access scheme with carrier
sense and collision avoidance through random backoff. The basic CSMA/CA mechanism
shown in figure 2.1:
Figure 2.1: Cotention window and waiting time
If medium is idle for at least the duration of DIFS , a node can access the medium at
once.This allows for short access delay under light load.
If medium is busy , nodes have to wait for the duration of DIFS , entering a contention
phase afterwards.
Each node now choose a random back off time within a contention window and delays
medium access for this random amount of time.
The node cntinues to sense the medium. As soon as a node senses the channel is busy ,
it has lost this cycle and has to wait for the next chance. But if the randomized additional
waiting time for a node is over and the medium is still idle ,the node can access the medium
immediately.
The basic CSMA/CA mechanism is not fair.Independent of the overall time a node has
already waited for transmission;each node has the same chances for transmitting data in the
next cycle.To provide fairness , IEEE 802.11 adds back off timer. Each node selects random
amount of waiting time within the range of contention window.
If certain station does not get access to the medium in first cycle, it stops its back off
timer , waits for the channel to be idle again for DIFS and starts the counter again. As soon
as the counter expires, the node accesses medium. This means that deffered stations do not
choose a randomized backoff time again, but continue to countdown.
Stations that have waited longer have the advantage over stations that have just en-
tered,in that they only have to wait for the remainder of their backoff timer from the previous
cycle.
6

13. 2.2.3 DFWMAC-DCF with RTS/CTS
Hidden terminal problem may occur in 802.11, if one station can receive two others, but
those cannot receive each other.
To deal with this problem, mechanism using two control packets , RTS and CTS.
After waiting for DIFS , the sender can issue a request to send (RTS) control packet.
Every node receiving this RTS now has to set its net allocation vector (NAV) in accor-
dance with the duration field
The NAV than specifies earliest point at which the station can try to access the medium.
If the receiver receives the RTS , it answers with the clear to send (CTS) waiting for
SIFS.
This CTS packet contains duration field and receivers have to adjust their NAV.
Now all nodes within receiving distance around sender and receiver are informed that
they have to wait more time before accessing the medium.
This mechanism reserves the medium for one sender exclusively.
It is also called a Virtual Reservation Scheme.
7

14. Chapter 3
Routing In Ad-Hoc Networks
3.1 Requirement of the Routing
ˆ It should be fully distributed, as centralized routing involves high control overhead
and hence is not scalable. Distributed routing is more fault-tolerant than centralized
routing, which involves the risk of single point of failure.
ˆ It must be adaptive to frequent topology changes caused by the mobility of nodes.
ˆ It must be localized, as global state maintenance involves a huge state propagation
control overhead.
ˆ It must be loop-free and free from stale routes.
ˆ It must converge to optimal routes once the network topology becomes stable. The
convergence must be quick.
ˆ It must optimally use scare resources such as bandwidth, computing power, memory
and battery power.
ˆ It should be able to provide a certain level of quality of service (Qos) as demanded by
the applications,and should also offer support for time-sensitive traffic.
ˆ The flooding must be less.
8

15. 3.2 General Issues for Ad Hoc Network Routing
Secure delivery and the capability to handle constant connectivity are the most important
issues for routing protocols in wireless mobile ad hoc networks. Once the path will establish
between the source end destination, the source will send message to the destination without
worried.If the connectivity of any two nodes changes and routes are affected by this change,
the routing protocol should be able to recover if an alternate path exists.
There are some other issues related to routing in wireless ad hoc networks. For example:
ˆ overhead is particularly important in a wireless network with limited bandwidth.
ˆ Power consumption may also be a problem in an ad hoc network with battery-powered
nodes.
ˆ Quality of service may be required in an ad hoc network supporting delay sensitive
applications such as video conferencing .
ˆ A routing protocol may need to balance traffic based on the traffic load on links.
ˆ Scalability of routing protocols is an important issue for large networks .
The routing protocol may need to implement security to protect against attacks, such
as sniffer, man-in-the-middle. Routing protocols may rely on information based on other
layers. For example, the Global Positioning System (GPS) can be used in wireless ad hoc
networks deployed in battlefields or connecting vehicles. Mobility prediction can improve
routing in wireless networks with known movement patterns, such as the IRIDIUM system
satellite network . Information from the medium access control layer may be propagated to
the network layer so that neighbours can be detected via MAC layer protocols. The power
of received signals from a neighbouring node can be used to decide whether neighbour is
moving closer or further away .
9

16. Chapter 4
Routing Protocols
4.1 Classification
Routing protocols for ad hoc wireless networks can be classified into several types based
on different criteria. The routing protocols for ad hoc wireless networks can be broadly
classified into four categories base on :-
ˆ Routing Information update mechanism
ˆ Use of Temporal information for routing
ˆ Routing Topology
ˆ Utilization of specific resources
4.1.1 Based on the routing information update mechanism
ˆ Proactive or table-driven routing protocols
ˆ Reactive or on demand routing protocols
ˆ Hybrid routing protocols
4.1.2 Based on the use of Temporal information for Routing
Since ad hoc wireless networks are highly dynamic and path breaks are much more
frequent than in wired networks, the use of temporal information regarding the lifetime of
the wireless links and the lifetime of the path selected assumes significance.
ˆ Routing protocols using past temporal information
ˆ Routing protocols that use future temporal information
10

17. 4.1.3 Based on Routing Topology
Routing topology being used in the Internet is hierarchical in order to reduce the state
information maintain at the core routers.
ˆ Flat topology routing protocols
ˆ Hierarchical topology routing protocols
4.1.4 Based on the Utilization of specific Resources
ˆ Power aware routing
ˆ Geographical information assisted routing
4.2 Proactive or table-driven routing protocols
These protocols are extension of the wired network routing protocols. They maintain
the global topology information in the form of the tables at every node. These tables are
updated frequently in order to maintain consistent and accurate network state information.
The distance-vector routing protocol (DSDV),wireless routing protocol (WRP),source-tree
adaptive routing protocol (STAR),and cluster-head gateway switch routing protocol (CGSR)
are some example for the protocols that belong to this category.
4.2.1 Destination sequenced distance-vector protocol
This protocol also called as the DSDV routing protocol. It is the enhanced version of
the distributed Bellman-Ford algorithm where each node maintains a table that contains the
shortest distance and the first node on the shortest path to every other node in the network.
It incorporate table update with increasing sequence number tag to prevent loops, to counter
to the count-to-infinity problem, and for faster convergences. As describe this is the table
driven so that at finite interval the tables of the each node exchange to update and which
are reachable from all the nodes. If the topologies of the network are change then all tables
are forwarded to their neighbor. Here in the table updating, we have two types:- One is
the full dump in which done either when the local topology changed significantly or when a
more incremental change required in the table. Second is the incremental update in which
node does not observe change in the topology. Here one example is given for table updating
and node table creation.
11

18. Figure 4.1: DSDV Protocol
Desination Next Hop Distance
A A 0
B B 1
C C 1
D D 1
E D 2
F D 2
Table 4.1: Routing Table of DSDV Protocol
Here consider the example, here node A is the source node and F is the destination
node. Here in the table first Column is destination node which is all nodes in the network.
Second Column is the next node in the shortest path to the source path. Third column is
the distance between two nodes- source to destination. And fourth column is the sequence
number of each packet to be received by them.
Here routing table for node A is indicating that the shortest path to the destination node
F is available through node D and the distance to it is two. And the packets to be received
at that place which has number as shown in table. If any link between two node is broken
then the distance is assign infinite to that node and update the all node’s routing table.
12

19. Advantages
ˆ The availability of the routers to all destination at all times implies that much less
delay is involved in the route setup process.
ˆ The mechanism of incremental updates with sequence number tags makes the existing
wired network protocol adaptable to ad hoc networks. Hence wired network protocol
can be applied to the ad hoc network by less modification.
Disadvantages
ˆ A small network with high mobility or a large network with low mobility can completely
choke the available bandwidth. Hence this protocol suffers from excessive control
overhead that is proportional to the number of nodes in the network.
ˆ In order to obtain information about a particular destination node, a node has to wait
for a table update message initiated by the same destination node.
4.2.2 Wireless routing protocol
The WRP protocols is the basically same as the DSDV protocols, but it is differ from
it only in the their routing protocol. The routing table contain the up-to-date view of the
network for the network for all known destination. The routing table keeps the shortest
distance, the predecessor node and flag indicating the status of the path. The path status
may be a simple path(correct) ,or a loop(error) ,or the destination node not marked(null).
The LTC(Link cost table) contain the cost of relaying message through each link. The
MRL(Message transmission list) contains an entry for the every update message that is to
be retransmitted and maintain the counter for the each entry. When a node detects a link
break, it sends an update message to its all neighbors with the link cost is infinite (?). And
that all neighbors find the alternate path to reach the destination and resend the message.
Advantages
ˆ It is the faster convergence and involves fewer table updates.
Disadvantages
ˆ Complexity of maintenance of multiple tables demands a larger memory and greater
processing power from the nodes.
ˆ At the high mobility, the control overhead involved in updating table entries is almost
the same as DSDV. So it is not suitable for highly dynamic and also for very large ad
hoc networks.
13

20. 4.2.3 Cluster head Gateway Switch Routing protocol
The CGSR protocol uses a hierarchical network topology that employs at topologies.
CGSR organizes nodes into clusters, with coordination among the member of each cluster
instructed nodes named ”cluster head”. This cluster head selected dynamically by employing
a least cluster change (LCC) algorithm. According to this algorithm ,nodes creates to be
a cluster-head only if it comes under the range of another cluster-head, where tie is broken
either using the lower ID or highest connectivity algorithm. CGSR protocol creates afixed
region in the network. Each node in the cluster region is known as cluster member and
they all are connected with pivot node which is called cluster-head .Two cluster region are
connected via node which are place in intersection region of two cluster region and called
cluster-gateway.
Figure 4.2: CGSR protocol
Here in the figure three cluster area are shown ,the all are overlapped in each other .so
between their intersection one node is placed as the gateway which transfer the information
of one cluster area to the other.
14

21. Advantages
ˆ CGSR is a hierarchical routing scheme which enables partial coordination between
nodes by electing cluster-heads. Hence , better bandwidth utilization is possible.
ˆ It is easy to implement priority scheduling scheme with token scheduling and gateway
code scheduling.
Disadvantages
ˆ It increases in path length and instability in the system at high mobility when the rate
of change of cluster-heads is high.
ˆ To avoid gateway conflicts, more resources are required.
ˆ The power consumption at the cluster-head node is also a matter of concern because
the battery-draining rate at the cluster-head is higher than that at a normal node.
4.3 On-Demand routing protocols
This type of protocols execute the path finding process and exchange routing information
only when path is required by the node to communicate with a destination. There some of
the routing protocols like Dynamic Source Routing Protocol (DSR) , Ad Hoc On-Demand
Distance Vector Routing Protocol (AODV) .
4.3.1 Dynamic Source Routing Protocol
This type of routing protocol is design to restrict the bandwidth consumed by control
packets in ad wireless networks by eliminating the periodic table-update message required
in the table driven approach. In this routing protocol does not require periodic ’hello’
packet transmission, which are used by a node to inform its neighbors of its presence. The
basic approach of this protocol during the routing construction phase is to establish a route
by flooding Route-Request packets in the network. The destination node, On receiving a
Route-Request packet, respond by sending Route-Reply packets back to the resource.
15

22. Figure 4.3: DSR Protocol
Here shown in the figure, the node 1 is the source node and the node 5 is the destination
node. when 1 has data packet to sent to the node 5, it initiate a Route-Request as BLUE
arrow in figure ,and sent it to all its neighbors or flooded. Each node receiving this request
packet check if it is the destination then it generate Reply packet and send to sender. If
it is not proper destination then again that node send request packets to their neighbor
until destination node not found. Each packet has unique sequence number so that in the
network while flooding loop will not generate. If duplicate the packet at any node then it
will discarded by the particular node where redundancy will observe.
16

23. Advantages
ˆ Do not exchange routing update periodically, so overhead transmission is greatly re-
duced
ˆ Can refer to cache for the new route when link fails.
Disadvantages
ˆ Scalability problem: High route discovery latency for large network.
ˆ High mobility problem: although the packet dropped may not be substantional, the
overhead traffic will increase a lot.
4.3.2 Ad Hoc On-Demand Distance Vector Routing Protocol
The Ad hoc On-demand Distance Vector (AODV) routing protocol is a reactive protocol.
Similar to DSR,AODV broadcasts a route request to discover a route in a reactive mode. The
difference is that in AODV, a field of the number of hops is used in the route record, instead
of a list of intermediate router addresses. Each intermediate router sets up a temporary
reverse link in the process of a route discovery. This link points to the router that forwarded
the request. Hence, the reply message can find its way back to the initiator when a route is
discovered. When intermediate routers receive the reply, they can also set up corresponding
forward routing entries. To prevent old routing information being used as a reply to the
latest request, a destination sequence number is used in the route discovery packet and the
route reply packet. A higher sequence number implies a more recent route request.
We use the example topology shown in Figure to illustrate the discovery procedure of
AODV. Note that Routers A and C are disconnected from each other while both of them
connect to B. When Router A starts a route discovery to C, a route request is broadcast. The
request packet contains the requested destination sequence number, which is 1 greater than
the one currently kept at A. The intermediate routers reply to the source if they know the
route to that destination with the same or higher destination sequence number. We assume
that B does not have a record for a route to C. Therefore, B first sets up a temporary link
pointing back to A. In the second step, it increases the number of hops by 1 and rebroadcasts
the request. When C receives that request, it creates a new destination sequence number. A
route reply with that new sequence number is sent by C. The initiator and all intermediate
routers build routing entries associated with this new sequence number when they receive
the reply. The number of hop values can be used to find a shorter path if a router receives
two replies with the same destination sequence number.
17

24. Figure 4.4: AODV Protocol
Advantages
ˆ AODV is loop-free due to the destination sequence numbers associated with routes.
Therefore, it offers quick convergence when the ad hoc network topology changes which,
typically, occurs when a node moves in the network
Disadvantages
ˆ Poor scalability is a disadvantage of AODV.
18

25. 4.4 Hybrid routing protocols
4.4.1 Zone Routing Protocol
The Zone Routing Protocol (ZRP) is a prototype routing protocol. ZRP is formed by two
sub-protocols, the Intrazone Routing Protocol (IARP) and the Interzone Routing Protocol
(IERP).
IARP is ”a limited scope proactive routing protocol used to improve the performance of
existing globally reactive routing protocols”. It relies on the service of a certain neighbor
discovery protocol (NDP) to provide neighbor information. IARP may use a scheme based
on the time-to-live (TTL) field in IP packets to control the zone range.
IERP is the reactive routing component of ZRP. This scheme is responsible for finding a
global path. It avoids global queries for destinations that would be sent to surrounding hop
neighbors. When global queries are required, ”the routing zone based broadcast service can
be used to efficiently guide route queries outward, rather than blindly relaying queries from
neighbor to neighbor”.
ZRP tries to combine the advantages of reactive and proactive routing protocols. The
potential disad-vantage is the lack of route optimization. We use the example network in
Figure to briefly show the concept of ZRP. The range of the zone is set to one. So routers
in Subnets I and II use proactive IARP to find routes to other routers in the same subnet.
For routes to the other subnet, reactive IERP is used.
Figure 4.5: Zone Routing Protocol
19

26. Advantages
ˆ By combining the best features of proactive and reactive routing scheme, ZRP reduce
the control overhead compared to the Route-Request flooding mechanism employed
in on-demand approaches and the periodic flooding of routing information packets in
table-driven approaches.
Disadvantages
ˆ In absence of a query control ,ZRP tends to produce higher control overhead than
the aforementioned schemes. This can happen due to the large overlapping of nodes’
routing zones. The query control must ensure that redundant or duplicate Route-
Request are not forwarded.
ˆ The decision on the zone radius has a significant impact on the performance of the
protocol.
20

27. References
ˆ Ad hoc wireless networks Architectures and protocols By C.Siva Ram Murthy and B.S.
Manoj
ˆ A Secure Routing Protocol for Ad Hoc network By Kimaya Sanzgir
ˆ Mobile Communications By Jochen H. Schiller
21