Different Routing protocols

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A Detail Qualitative Performance Evaluation
of Integrated EIGRP/IS-IS and RIP/IS-IS
Routing Protocols in Hybrid Networks
A Dissertation Report Submitted in the Partial Fulfilment of
The Award of the Degree of
MASTER OF TECHNOLOGY
IN
COMPUTER SCIENCE AND ENGINEERING
Under Guidance of: Submitted By:
Name of Internal Guide Name of Students
(Designation) Roll No
LOGO
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

LIST OF ABBREVIATIONS
ABR Area Border Router
ASBR Autonomous System Boundary Router
AS Autonomous System
BR Backbone Router
BDR Backup Designated Router
CSNP Complete Sequence Number Packet
DR Designated Router
DBD Data Base Description
DUAL Diffusion Update Algorithm
DVR Distance Vector Routing
EIGRP Enhanced Interior Gateway Routing Protocol
FC Feasible Condition
FD Feasible Distance
FS Feasible Successor
IIH Intermediate System-Intermediate System HELLO
IR Internal Router
IS-IS Intermediate system to intermediate system
LSA Link-State Advertisement
LSAck Link-State Acknowledgement
LSDB Link-State Database

LSP Link State Packet
LSR Link-State Request
LSU Link-State Update
L1/L2 Level 1/Level 2
NET Network Entity Title
NSAP Network Service Access Point
NSSA Not-So-Stubby-Area
OSPF Open Shortest Path First
PDM Protocol Dependent Module
PSNP Partial Sequence Number Packet
RD Reported Distance
RTP Reliable Transport Protocol
SPF Shortest Path First
VLSM Variable Length Subnet Mask

ABSTRACT
In modern internet era, communication networks are growing very rapidly. To provide
efficient routing in the network, routers play an important role. They take part in the
network and forward the packets from source to destination and also keep an eye on the
data so that it remains in control manner. Routing is the process of transferring data from
source node to destination node. Routing selects appropriate path in the network and
forward a packet through the network to a device on a different networks and it is based
on routing protocols. Routing Information Protocol (RIP), Enhanced Interior Gateway
Routing Protocol (EIGRP) and Intermediate System to Intermediate System (IS-IS) are
the dominant interior routing protocols for such networks. This thesis presents a
simulation based analysis of these protocols. We used the combination of EIGRP&IS-IS,
RIP&IS-IS routing protocols on the Hybrid network in order to reveal the advantage of
one over the other as well as the robustness of each protocol combination and how this is
measured. To carry out the network simulations, we used Optimized Network
Engineering Tool (OPNET) v16.0. The comparison analysis is based on several
parameters that determine the robustness of these protocols. The routing protocol
convergence time is one important parameter which determines the time needed by the
routers to learn the new topology of the network whenever a change occurs in the
network. The routing protocol which converges faster is considered a better routing
protocol. We used throughput, HTTP object response time, database response time and e-
mail download response time parameters to measure the routing performance of the
network.
Keywords: EIGRP, IS-IS, IGR, RIP, HTTP, OPNET.

Chapter 1
INTRODUCTION
INTRODUCTION
Routing protocols provide essential role in the Enhanced Interior Gateway Routing
Protocol (EIGRP) is modern communication networks. A routing protocol based on
Distance Vector Routing algorithm where determines how routers communicate with
each other and Intermediate Systems-Intermediate Systems (IS-IS) and forward the
packets through the optimal path to travel Open Shortest Path First (OSPF) are based on
Link State from a source to a destination node. All of the above Protocols are from has
different configuration in comparison with others, the interior gateway protocol (IGP)
and are used for so in a network with a special structure, different Autonomous Systems
(AS) [2] protocols depending on their parameters demonstrates IS-IS can be extended
easily and utilizes Dijkstra better performance. As we know, Routing protocol algorithm
for finding the best route Meanwhile, EIGRP operates based on routing algorithms.
Dynamic and static and OSPF utilize Diffusing Update Algorithm (DUA), routing
algorithms are important algorithms for modern which consist of Distance Vector and
Link State routing communication networks. Modern communication algorithms EIGRP
has been CISCO dedicated protocol networks such as internet network use dynamic in
opposite to other general protocols. The cost of routing algorithms instead of static
algorithms, because static in EIGRP protocol is based on bandwidth and delay [5]
algorithms don’t utilize network's current load in finding and also the cost of routing
OSPF is based on just the best paths [1]. Dynamic routing algorithms have bandwidth
utilization different kinds, but there are two essential and important Performance analyses
of different routing protocols algorithms Distance Vector Routing and Link State has
been done based on various performance metrics like Routing algorithms which are
employed in recent network convergence, router convergence, queuing communication
networks, Adaptively and scalability delay, throughput network bandwidth utilization, in
comparison with Vector Routing algorithm.

1.1 Problem Description:
Interior networks mainly use the following four routing protocols: EIGRP, RIP, OSPF
and IS-IS. Due to its scalability, OSPF is used more often than EIGRP [1]. OSPF and IS-
IS are link state protocols. These protocols consume high bandwidth during network
convergence. Both protocols are relatively complicated to setup on the network but they
are the preferred protocols for larger networks. On the other hand, EIGRP has a faster
convergence time than OSPF and IS-IS, it can be used in different network layer
protocols and it is relatively easy to setup on the network. However, EIGRP is a CISCO
proprietary protocol, which means that it can only be used on CISCO products.
In this thesis, we will look at the advantages of using RIP and IS-IS on hybrid network
and EIGRP and IS-IS on another network. The comparison analysis of the routing
protocols will be performed on OPNET.
1.2 Motivation
The major causes for the degradation of the service performance in Internet are network
congestion, link failures, and routing instabilities. In [2] it has been found that most of the
disruptions occur during routing changes. A few hundred milliseconds of disruption are
enough to cause a disturbance in voice and video [2]. A disruption lasting a few seconds
is long enough for interrupting web transactions. Hence, during routing protocol
convergence data packets are dropped, delayed, and received out-of-order at the
destination resulting thus in a serious degradation in the network performance.
To support a wide variety of network services such as web browsing, telephony, database
access and video streaming, it becomes important to analyze different routing protocols
so that network resources are utilized more efficiently. Routing protocols are the main
factors contributing to speed-up data transfers within the network. The performance of
the routing protocols can be tested by their convergence time, link throughput and
application layer service performance, e.g., HTTP and FTP. Convergence time is the time
period required for the routing protocol to converge and reach a steady state. In routing

protocols, the convergence time is an important aspect in indicating routing protocol
performance.
1.3 Aims and objectives:
 Develop and design a simulation model and scenarios for integrated EIGRP/IS-IS
and RIP/IS-IS routing protocols in hybrid networks.
 Perform a simulation on different scenarios and evaluate via different metrics.
 Analysis of the results in Hybrid environment.
 Comparative study has been done on the basis of simulation results.
 Deriving a conclusion on basis of performance evaluation.
1.4 Introduction to Routing Protocols:
Forwarding of The Internet Protocol (IP) packets is the primary purpose of Internet
routers. A routing protocol is a set of process, algorithm, and messages that are used to
learn about remote networks and to quickly adapt whenever there is a change in the
network topology. Routing protocols can be classified into different groups according to
their characteristics: Interior Gateway Protocol (IGP) or Exterior Gateway Protocol
(EGP); Distance Vector or Link State; Class-full or Classless. Some of the most
commonly used routing protocols are as the follows:
 RIP: A class-full distance vector IGP
 RIPv2: RIP version 2. A classless distance vector IGP
 EIGRP: The advanced distance vector IGP developed by Cisco
 OSPF: A link state IGP
1.4.1 Routing Protocol Classification:
A. Routing Information Protocol (RIP):
The Routing Information Protocol (RIP), which is a distance-vector based algorithm, is
one of the first routing protocols implemented on TCP/IP. Information is sent through the
network using UDP. Each router that uses this protocol has limited knowledge of the
network around it. This simple protocol uses a hop count mechanism to find an optimal

path for packet routing. A maximum number of 16 hops are employed to avoid routing
loops. However, this parameter limits the size of the networks that this protocol can
support. The popularity of this protocol is largely due to its simplicity and its easy
configurability. However, its disadvantages include slow convergence times, and its
scalability limitations. Therefore, this protocol works best for small scaled networks.
Fig: 1 Routing Protocol Classification
B. Open Shortest Path First (OSPF):

Open Shortest Path First (OSPF) is a very widely used link-state interior gateway
protocols (IGP). This protocol routes Internet Protocol (IP) packets by gathering link-
state information from neighbouring routers and constructing a map of the network.
OSPF routers send many message types including hello messages, link state requests and
updates and database descriptions. Djisktra’s algorithm is then used to find the shortest
path to the destination. Shortest Path First (SPF) calculations are computed either
periodically or upon a received Link State Advertisement (LSA), depending on the
protocol implementation. Topology changes are detected very quickly using this protocol.
Another advantage of OSPF is that its many configurable parameters make it a very
flexible and robust protocol. Contrary to RIP, however, OSPF has the disadvantage of
being too complicated.
C. Enhanced Interior Gateway Routing Protocol (EIGRP):
EIGRP is a Cisco-developed advanced distance-vector routing protocol. Routers using
this protocol automatically distribute route information to all neighbours. The Diffusing
Update Algorithm (DUA) is used for routing optimization, fast convergence, as well as to
avoid routing loops. Full routing information is only exchanged once upon neighbour
establishment, after which only partial updates are sent. When a router is unable to find a
path through the network, it sends out a query to its neighbours, which propagates until a
suitable route is found. This need-based update is an advantage over other protocols as it
reduces traffic between routers and therefore saves bandwidth. The metric that is used to
find an optimal path is calculated with variables bandwidth, load, delay and reliability.
By incorporating many such variables, the protocol ensures that the best path is found.
Also, compared to other distance-vector algorithms, EIGRP has a larger maximum hop
limitation, which makes it compatible with large networks. The disadvantage of EIGRP is
that it is a Cisco proprietary protocol, meaning it is only compatible with Cisco
technology.

Chapter 2
LITERATURE REVIEW
2. Literature Review:
The Literature Review part of the presented thesis intends to accomplish two tasks.
Firstly, a detailed overview of the theoretical background related to the discussed
technologies is performed. It is believed that the in-depth explanation of the functions of
the involved routing protocols and IP protocols offers a knowledge foundation that is
absolutely necessary for the reader to comprehend with the presented research. Secondly,
the conducted by the scientific community related work, related to the Thesis topic is
presented. Finally, the author of this thesis introduces his personal view and critic on the
related research and he’s subjective opinion and conclusions on the subject. Both
Theoretical Background and Related Work sections’ authorship was assisted by
reviewing existing bibliography that is being cited accordingly. For the Theoretical
Background part, published scientific and computer networking books were advised in
order to give an as deep as possible understanding of the discussed technologies.
Ittiphon krinpayorm et al. [2] applied the EIGRP algorithm to an application based on
Maude. Maude is a programming language for formal specifications using algebraic
terms. It is an interpreted language that allows the verification of properties and
transformations on models that can run the model like a prototype. The authors show how
to build an infrastructure of processes implemented by Maude, giving the chance to send
a message directly to a neighbor or broadcast to all neighbors. EIGRP protocol
implements the top of this basic infrastructure. Finally, the global system is tested and
analyzed. The analysis is based on the search command that proves if a "bad" success
could happen. This allows verifying the model, which examines whether a formula is true
for all conditions. We have also found some works and a master thesis that compare and
make some kind of testing with multiple protocols.

Y. Navaneeth Krishnan et al; [3] In this thesis explored two eminent protocols namely
Open Shortest Path First (OSPF) and Enhanced Interior Gateway Routing Protocol
(EIGRP). Performed based on the Quantitative metrics such as Convergence Time, End-
to-End delays, Throughput and Packet Loss through the simulated network models. The
evaluation results indicate that EIGRP routing protocol provides a better performance
than OSPF routing protocol for real time. Conclude that EIGRP uses less system
resources when compared to OSPF. A use of less system resources of EIGRP Routing
protocol that produces lesser heat and therefore the cooling Cost is also saved.
Mr. Rajneesh Narula, Mr. Kaushal [7] This research focuses on the design and
performance of Hybrid Network incorporating different intra-domain routing algorithms
and performed the transmission of video-and voice-data streams over Hybrid network.
Discussed classification of Routing Protocols such as Distance vector routing protocol
and Link state routing then compared IS-IS & RIP and IS-IS & OSPF on various
performance parameters for video & voice data transmission.
Jagdeep Singh, Dr. Rajiv Mahajan [8] Here in this thesis OPNET simulation tool is used
to analyzed the performance of different routing protocols RIP, EIGRP and OSPF
.Simulated Email Download Response Time, Email Upload Response Time, Using
Throughput parameter determined that EIGRP has higher throughput and less packet loss
than other protocols. Also Found that EIGRP performs poor for Email download and
upload response time and DB query response time. While RIP performs well.
Kisten, S et al [9] This work presents the implementation decisions to be made when the
choice is between protocols that involve distance vector or link state or the combination
of both. Here a comparison is made between different parameters and a detailed
simulation study is performed on the network with Different routing protocols and it has
been shown that EIGRP provides a better network convergence time, less bandwidth
requirements and better CPU and memory utilization compared to OSPF also
RIP.EIGRP, OSPF also RIP are the active routing protocol being used in the practical
networks to propagate network topology information to the neighbouring routers. There

have been a large number of static and dynamic routing protocols available but choice of
the right protocol for routing is dependent on many parameters critical being network
convergence time, scalability, memory and CPU requirements, Security and bandwidth
requirement etc.
Thorenoor, S.G et al; [10] This work provides a lot of information about this routing
protocol. RIP is the oldest protocol. It uses a distance vector algorithm to form the
routing tables and calculates the distance to a destination host in terms of how many hops
a packet must traverse. It also shows technical aspects of the packet format and the
metric. Due to its small number of hops, RIP is not created for large systems. Several
methods have been added to the RIP protocol in order to solve some problems such as the
generation of loops.
Nohl, A.R, Molnar et al; [12] OSPF and EIGRP will distribute routing information
between routers in the same autonomous system. In This research found that how routing
protocol works and compare those dynamic routing protocols in IPv4 and IPv6
environments. Simulated Network based on GNS3 and Packet Tracer software. The
conclusions according to simulation and analysis performed that Packet sents in an IPv4
networks is smaller than the packet sents in an IPv6 networks. packet loss is smaller
when using EIGRP as compared with OSPF. Whether it is using an IPv4 addressing or
IPv6 addressing. EIGRP packets sent has a smaller size compared to the packets sent by
OSPF.
Talal Mohamed Jaffar et al; [13] This thesis compared the performance of intra-domain
routing protocols such as Enhanced Interior Gateway Protocols of IEEE 802.3 LAN by
evaluating various parameters including Network convergence time, Delay Variation,
End to End Delay, Utilization, Throughput, Queuing Delay and IP Processing Delay and
Also compared the performance of video- and voice-data on the entire networks results
found that IGRP routing protocol enabled networks performs better than that of EIGRP.
OSPF (Open Shortest Path First) and EIGRP (Enhanced Interior Gateway Protocol) are
routing protocol which is a member of IGP (Interior Gateway Protocol). OSPF and

EIGRP will distribute routing information between routers in the same autonomous
system. This research wills find how routing protocols works and compare those dynamic
routing protocols in IPv4 and IPv6 network. This research will simulate some network
topology and shows that EIGRP are much better than OSPF in many different topologies.
[13] This thesis looks at an approach for tuning dynamic routing systems using link
metrics and focusing on the EIGRP dynamic routing protocol in order to get consistent
and expected failover of dynamically routed links in complex networks. It examines:
architectural issues for designing enterprise network backbones with redundant links;
operational routing issues associated with configuring "hot spare" routers and
contingency backbone sites; and finally a metrics system for tuning the routing system
where multiply redundant links (redundant groups of redundant links) are used.
B. Albrightson et al. let us know in [14] that EIGRP is based on IGRP protocol, but
improving their benefits. They explain that EIGRP is a protocol based on a hybrid routing
algorithm, sharing some properties of distance vector and link state algorithms. This
protocol is the first Internet protocol that addressed the loop problem. Other aspects
which shows are the type of metrics, the transport mechanisms and the methods used to
discover the networks, among other features.
M. Nazrul and Md. A. Ullah in [16] their goal was to evaluate which protocol, EIGRP or
OSPF, is most suitable to route in real-time traffic. The simulations are based on the
convergence Time, Jitter, End-to-End delay, Throughput and Packet Loss. They
demonstrated that EIGRP has faster convergence time than OSPF, because EIGRP can
learn the topology information and updates faster than the others. Another important
issue is that the packet delay variation for EIGRP is better than for OSPF, and
consequently data packets in EIGRP reach faster to the destination compared to OSPF.
Also, EIGRP, present less number of lost packets and a higher throughput than OSPF,
when there is high link congestion.

Xu, Dahai et al [26]. show the design and development of a method for detecting RIP
routing updates. Specifically, RIP-TP protocol is presented. It uses hop count as routing
metric. The authors emphasize its efficiency, simplicity, low operating cost and
compatibility with the standard RIP. In order to assess the design efficiency, they show a
series of experimental simulations to demonstrate that it is possible the improvement of
fault detection in routing protocols. They particularize these evidences with RIP. There is
published a work about OSPF routing protocol in [12].
Ahmed Mahmoud et al. [38] In this thesis, its authors provided a study of the OSPF
behaviour in a large operational network, based on a hierarchical structure formed by 15
areas and 500 routers. One of its main features of this network is that it provides highly
available and reliable connectivity from customer’s facilities to applications and
databases residing in a data canter. They introduced a methodology for OSPF traffic
analysis, analyzing the link-state advertisement (LSA) traffic which is generated when
the network experiments a topology change. Also the authors provide a general method to
predict the rate of refresh LSAs from router configuration information and a set of
measurements confirm that the method is accurate. Moreover, the authors observed that
the type of topology could provoke certain asymmetries in duplicate-LSA traffic. Finally
they showed a method for reducing duplicate-LSA traffic by altering the routers’ logical
OSPF configurations, without changing the physical topology of the network. Another
study of OSPF is shown in [13].
A. Basu et al., studies the stability of the OSPF protocol under steady state and with
interferences. In this study we will see what effects are given by the TE (Traffic
Engineering) extensions on the stability of a network when OSPF is running. OSPF TE
extensions provide mechanisms for ensuring that all network nodes have a consistent
view of the traffic parameters associated with the network. The authors also analyze
whether it is possible to accelerate the convergence time of the network, analyzing the
Hello packets and the number of route flaps caused by a failure in the network, because
the number of route flaps characterizes the intensity disruption of the network. The
authors conclude the thesis letting us know that the OSPF-TE protocol seems fairly

stable, and adding that extensions TE does not significantly change the times of
convergence, even in presence of multiple failures. But, a high number of failures in the
network could lead to overload of the processor because it will have to attend a large
number of alerts in the short term. Because EIGRP is a Cisco proprietary protocol,
sometimes, it is quite difficult to find information about it.
Another work of the same authors where there is a comparative analysis of the routing
protocols EIGRP and OSPF is shown in [17]. In order to evaluate OSPF and EIGRP’s
performance, their authors designed three network models configured with OSPF, EIGRP
and a combination of EIGRP and OSPF and the three topologies where simulated using
the Optimized Network Engineering Tool (OPNET) [18]. In this case, the protocols and
the combined use of them are also analyzed in terms of convergence time, jitter, end-to-
end delay, throughput and packet loss. The evaluation results show that, in general, the
combined implementation of EIGRP and OSPF routing protocols in the network
performs better than each one of them alone.
E. S. Lemma at al. in [19] They use OPNET to carry out the network simulations, using
a combination of EIGRP&IS-IS, OSPF&IS-IS. The main aim of that thesis was to
configure multiple routing protocols on a selected network topology and analyze the
performance improvement of the network. They based their comparison analysis on
several parameters that determined the robustness of these protocols. In order to do it,
their authors simulated five different scenarios on the same network in order to reveal the
advantage of one over the others as well as the robustness of each protocol combination
and how this can be measured. The selected protocols for each scenario were OSPF,
EIGRP, IS-IS, OSPF/IS-IS and EIGRP/IS-IS. The results show that the use of combined
protocols in a network, improve significantly the network performance.
The increased use of new technologies incremented the possibility of malicious attacks to
our network, which could cause data loss, loss of privacy and even, eventually can lead to
large monetary losses. Therefore, in [20], the authors examine the advantages and
disadvantages of MD5 (Message-Digest Algorithm 5) authentication system compared to
non-secure system when EIGRP, RIPv2, OSPF routing protocols are used. MD5 is a 128

bits cryptographic reduction algorithm that is widely used. The authors measure values of
delay, jitter and network overhead, in both cases for all protocols, and conclude that the
EIGRP protocol shows the lower overhead, even when the system is heavily overloaded.
C-C Chiang et al. [21] As we know, the security mechanisms play an important role in
networks and in the Internet world. There are many ways to find vulnerabilities in a
network and launch attacks against the network. In this thesis, the authors examine the
performance and security problems of several existing routing protocols including RIP,
OSPF and EIGRP. Several routing performance parameters are evaluated and analyzed
through using SNMP (Simple Network Management Protocol) sessions. They briefly
describe the three IGP protocols, their network Infrastructure and the experimental
evaluation methods. In opposite of denegation of service (DOS) attacks and contaminated
tables, which are among the most serious attacks to network topologies, the authors
propose an automatic mechanism to analyze the states of routing and intrusion detection
in real-time response. The study concludes that the distance vector routing protocols are
more robust than link-state routing protocols for the unstable network topology because
global link-state's flooding of updates increase when link state changes. But, the distance
vector algorithms can only used for small networks.
Don Xu et al; [47] In this thesis we evaluate the Enhanced Interior Gateway Routing
Protocol (EIGRP) via packets simulation. EIGRP, an intra-domain routing protocols
developed by Cisco, is mainly based on the Diffusing Update Algorithm (DUAL) which
computes shortest paths distributed without creating routing-table loops or incurring
counting-to-infinity problem. Previous studies showed EIGRP’s ability to adapt quickly
to routing changes in medium-scale networks. In our research, we developed a detailed
simulation model of EIGRP (publicly available), and we used it to evaluate EIGRP
performance under a very dynamic network. Our results showed that EIGRP converges
faster than a single TCP timeout in most cases. The simulated network was a composite
of wired and wireless hosts, and the results hold for both types of media. In addition, the
study showed a feasible approach for seamless mobility and continuous connectivity for
users of mobile wireless devices as they move within an Autonomous System (AS).

Neha Singh et al; [56] In this thesis, we model power of core routers which are using
OSPF and EIGRP protocols. The model can accurately predict the power consumption of
the routers with an important speedup. Also we establish the total quantity of routers
required to support thousands of servers in the mentioned network. Simulations done
with NS2 in a wide range of network configurations to support the proposed model.
Results obtained from the simulations are in agreement with those obtained by the model.
This work settles an open question with a positive answer: Optimal traffic engineering (or
optimal multi commodity flow) can be realized using just link-state routing protocols
with hop-by-hop forwarding. Today’s typical versions of these protocols, Open Shortest
Path First (OSPF) and Intermediate System-Intermediate System (ISIS), split traffic
evenly over shortest paths based on link weights. However, optimizing the link weights
for OSPF/ISIS to the offered traffic is a well-known-hard problem and even the best
setting of the weights can deviate significantly from an optimal distribution of the traffic.
In this thesis, we propose a new link-state routing protocol, PEFT that split traffics over
multiple paths with an exponential penalty on longer path. Unlike its predecessor, DEFT,
our new protocol provably achieves optimal traffic engineering while retaining the
simplicity of hop-by-hop forwarding. The new protocol also leads to a significant
reduction in the time needed to compute the best Link weights. Both the protocol and the
computational methods are developed in a conceptual framework, called Network
Entropy Maximization that is used to identify the traffic distributions that are not just
most select, but also achievable by link-state routing.
2.4 Routing Protocol Overview
In IP networks, the main task of a routing protocol is to carry packets forwarded from one
node to another. In a network, routing can be defined as transmitting information from a
source to a destination by hopping one-hop or multi hop. Routing protocols should
provide at least two facilities: selecting routes for different pairs of source/destination
nodes and, successfully transmitting data to a given destination. Routing protocols are
used to describe how routers communicate to each other, learn available routes, build
routing tables, make routing decisions and share information among neighbours. Routers

are used to connect multiple networks and to provide packet forwarding for different
types of networks. The main objective of routing protocols is to determine the best path
from a source to a destination. A routing algorithm uses different metrics based on a
single or on several properties of the path in order to determine the best way to reach a
given network. Conventional routing protocols used in interior gateway networks are
classified as Link State Routing Protocols and Distance Vector Routing Protocols. There
are also other classifications of routing protocols, i.e., dynamic or static, reactive or
proactive, etc. The conventional routing protocols can be used as a basis for building up
other protocols for other types of communication networks such as Wireless Ad-Hoc
Networks, Wireless Mesh Networks, etc. This chapter introduces different types of routing
protocols, routing methods, network roles and characteristics.
2.2 Desirable Properties
To provide efficient and reliable routing, several desirable properties are required from
the routing protocols:
 Distributed Operation: The protocol should not depend on any centralized node
for routing, i.e., distributed operation. The main advantage of this approach is that
in such a network a link may fail anytime.
 Loop Free: The routes provided by the routing protocol should guarantee a loop
free route. The advantage of loop free routes is that in these cases the available
bandwidth can be used efficiently.
 Convergence: The protocol should converge very fast, i.e., the time taken for all
the routers in the network to know about routing specific information should be
small.
 Demand Based Operation: The protocol should be reactive, i.e., the protocol
should provide routing only when the node demands saving thus valuable network
resources.
 Security: The protocol should ensure that data will be transmitted securely to a
given destination.
 Multiple Routes: The routing protocol should maintain multiple routes. If a link
fails or congestion occurs then the routing can be done through the multiple routes

available in the routing table saving thus valuable time for discovering a new
route
 Quality of Service (QoS): The protocol design should provide some class of
QoS depending upon its intended network use. Not all routing protocols used in
current networks meet the above requirements. Each protocol differs in some
way.
2.3 Metrics and Routing:
2.3.1 Metrics
The path cost can be measured based on metric parameters of the path. To determine the
best path among all the available routes, routing protocols will select the route with the
smallest metric value (or cost). Every routing protocol has its own metric calculation.
2.3.2 Purpose of a metric
There are scenarios where routing protocols learn about more than one route to the same
destination. To select the best among the available paths, routing protocols should be able
to evaluate and distinguish among these paths. Hence, for this purpose, different metrics
are used. A metric is a value utilized by the routing protocols to assign a cost to reach the
destination or remote network. When there are multiple paths to the same destination,
metrics are used to determine which path is the best. Calculation of metrics for each
routing protocol is done in different ways. For example EIGRP uses a combination of
bandwidth, load, reliability and delay. OSPF uses bandwidth while Routing Information
Protocol (RIP) uses hop count.
2.3.3 Metric Parameters
Different metrics are used by different routing protocols and on the basis of the metric
used, routing protocols cannot be easily compared. Due to different metrics used, two
different protocols may choose different paths to same destination [1]. In IP routing
protocols, the following metrics are often used:
 Hop count: Counts the number of routers a packet should traverse to reach the
destination.
 Bandwidth: When used as a metric, the path with highest bandwidth is preferred.

 Load: It describes the traffic utilization of a certain link. When load is used as a
metric the link with lowest load is the best path.
 Delay: It is a measure of the time a packet takes to pass through a path. The best
path is selected with the least delay.
 Reliability: Calculates the probability of a link failure. Probabilities can be
calculated from previous failures or interface error count. Path with highest
reliability is chosen as the best path.
 Cost: Cost is a value which is decided by the network administrator or Internet
Operating System (IOS) to indicate a preferred route. Cost can be represented as a
metric, combinations of metrics or a policy.
2.4 Hop Count versus Bandwidth
Hop count is defined as the number of routers a packet needs to travel through that path
before it arrives at the destination. Each router represents one hope count. Distance vector
routing protocols such as RIP use the path with smallest number of hops from multiple
paths that exists to reach a destination. Bandwidth is used as metric in many kinds of
routing protocols, e.g., OSPF. The path with highest bandwidth value is selected as best
path for routing [1]. If we use hop count as the metric, the routers will choose suboptimal
routes.
Figure: 2.1 Hop Count versus Bandwidth

For example, consider Figure 2.1. When the routing protocol uses hop count as a metric,
the router R1 will select suboptimal route directly through R2 to arrive at PC2. However,
in routing protocol such as OSPF, R1 will choose the shortest path depending on the
bandwidth. R1 chooses the link through R3.
2.5 Administrative Distance:
Administrative Distance (AD) describes the rate of trustiness of packet received at the
receiver. It is expressed by integers (0 to 255), where 0 means very trusted and, 255
means no traffic flow on the path. AD is used for the purpose of determining which
routing source to be used. The routers must determine which routes to be included in the
routing table before using that route during forwarding packet.
At the time when the router learns a route about the same network from more than one
routing source, the determination of the route used in the routing table is based on the AD
of the source routes. The AD with the lowest value will have precedence as the route
source. The most preferred AD is zero and only the directly connected network has zero
AD, and it cannot be altered.
2.6 Classification
Routing protocols can be classified as:
 Static and dynamic routing protocols
 Classful and Classless routing protocols
 Distance Vector and Link State routing protocols
2.7 Static versus Dynamic Routing
In static routing, the routing table is constructed manually and routes are fixed at router
boot time. The network administrator updates the routing table whenever a new network
is added or deleted within the AS. Static routing is used only for small networks. It has
bad performance when the network topology changes. The main advantages of static
routing are its simplicity and the fact that it provides more control for the system
administrator to control the whole network. The main disadvantages of static routing are

as follows: it is impossible to accommodate rapid network topology changes and it is
hard to setup all the routes manually. In dynamic routing protocols, the routing tables are
created automatically in such a way that adjacent routers exchange messages with each
other and the best routes are computed using own rules and metrics. The selection of best
routes is based on specific metrics such as link cost, bandwidth, number of hops and
delay and these values are updated by using protocols which propagate route information.
The main advantage of this type of routing protocols is that it helps the network
administrator to overcome the time consumed in configuring and maintaining routes. The
drawback of dynamic routing is that it may create diverse problem such as route
instabilities and routing loops.
2.8 Classful and Classless Routing
Routing protocols can also be divided into classful and classless routing based upon the
subnet mask. In classful routing, subnet masks are the same throughout the network
topology and such a protocol does not send information of the subnet mask in its routing
updates. When a router receives a route, it will do the following [8]:
 Routers which are directly connected to the interface of the major network uses
the same subnet mask.
 Applies classful subnet mask to the route when the router is not directly
connected to interface of the same major network.
Classful routing protocols are not used widely because:
 It does not support Variable Length Subnet Masks VLSM (VLSM) for
hierarchical addressing.
 It is not able to include routing updates.
 It cannot be used in sub-netted network.
 It is not able to support discontiguous networks.
Classful routing protocols can still be employed in today’s networks but may not be used
in all scenarios since they do not include the subnet mask. Figure 2.2 shows a network
using classful routing protocol in which the subnet mask is same throughout the network.

RIPv1 and IGRP are examples of routing protocols that belong to the classful routing
family of protocols.
Figure 2.2: Classful Routing with Same Subnet Mask
Figure 2.3: Classless Routing with Different Subnet Masks
In classless routing, the subnet mask can vary in network topology and in the routing
updates and the subnet mask together with the network address are included. Most
networks today are not allocated based on classes and the value of the first octet is not
used to determine the subnet mask. Classless routing protocols support discontinuous
networks. Figure 2.3 shows a network using classless routing in which different subnet

mask are used within the same topology. RIPv2, EIGRP, OSPF, IS-IS and BGP are
examples that belong to the classless routing family of protocols.
2.9 Distance Vector Routing:
As the name indicates, distance vector routing protocol advertise routes as a vector of
distance and direction. Here, the distance is represented in terms of hop count metrics and
direction is represented by the next hop router or exit interface. DVR is based upon the
Bellman Ford algorithm. In DVR, the paths are calculated using the Bellman Ford
algorithm where a graph is built in which nodes takes position of the vertices and the
links between the nodes takes position of the edges of the graph. In DVR, each node
maintains a distance vector for each destination. The distance vector consists of
destination ID, next hop and shortest distance. In this protocol, each node sends a
distance vector to its neighbours periodically informing about the shortest paths. Hence,
each node discovers routes from its neighbouring nodes and then advertises the routes
from its own side. For information about the routes each node depends upon its
neighbour which in turn depends on their neighbouring nodes and so on. Distance vectors
are periodically exchanged by the nodes and the time may vary from10 to 90 seconds.
For every network path, when a node receives the advertisement from its neighbours
indicating the lowest-cost, the receiving node adds this entry to its routing table and re-
advertises it on its behalf to its neighbours.
2.10 Methods of Routing
Distance vector routing protocol is one kind of protocol that uses the Bellman Ford
algorithm to identify the best path. Different Distance Vector (DV) routing protocols use
different methods to calculate the best network path. However, the main feature of such
algorithms is the same for all DV routing protocols. To identify the best path to any link
in a network, the direction and distance are calculated using various route metrics.
EIGRP uses the diffusion update algorithm for selecting the cost for reaching a
destination. Routing Information Protocol (RIP) uses hope count for selecting the best
path and IGRP uses information about delay and availability of bandwidth as information
to determine the best path [6]. The main idea behind the DV routing protocol is that the

router keeps a list of known routes in a table. During booting, the router initializes the
routing table and every entry identifies the destination in a table and assigns the distance
to that network. This is measured in hops. In DV, routers do not have information of the
entire path to the destination router. Instead, the router has knowledge of only the
direction and the interface from where the packets could be forwarded [5].
2.11 Properties of Distance Vector Routing
The properties of DV routing protocol include [1]
 DV routing protocol advertise its routing table to all neighbours that are directly
connected to it at a regular periodic interval.
 Each routing tables needs to be updated with new information whenever the
routes fail or become unavailable.
 DV routing protocols are simple and efficient in smaller networks and require
little management.
 DV routing is base on hop counts vector.
 The algorithm of DV is iterative.
 It uses a fixed subnet masks length.
2.12 Advantages and Disadvantages of DV Routing
DV routing protocol suffers from the problem of count to infinity and Bellman Ford
algorithm has a problem of preventing routing loops [4]. The advantages of DV routing
protocols are:
 Simple and efficient in smaller networks.
 Easy to configure
 Requires little management.
The main disadvantages of DV routing protocols:
 Results in creating loops.
 Have slow convergence.
 Problems with scalability.
 Lack of metrics variety.

 Being impossible for hierarchical routing.
 Bad performance for large networks.
Few techniques exist to minimize the limitations of DV routing protocols. They are [7]:
Split horizon rule It is a one of the methods to eliminate routing loops and increase the
convergence speed. Triggered update It uses specific timers and increases the response
of the protocol.
2.13 Link State Routing:
Link State Routing (LSR) protocols are also known as Shortest Path First (SPF) protocol
where each router determines the shortest path to each network. In LSR, each router
maintains a database which is known as link state database. This database describes the
topology of the AS. Exchange of routing information among the nodes is done through
the Link State Advertisements (LSA). Each LSA of a node contains information of its
neighbours and any change (failure or addition of link) in the link of the neighbours of a
node is communicated in the AS through LSAs by flooding. When LSAs are received,
nodes note the change and the routes are recomputed accordingly and resend through
LSAs to its neighbours. Therefore, all nodes have an identical database describing the
topology of the networks. These databases contain information regarding the cost of each
link in the network from which a routing table is derived. This routing table describes the
destinations a node can forward packets to indicating the cost and the set of paths. Hence,
the paths described in the routing table are used to forward all the traffic to the
destination. Dijkstra’s algorithm is used to calculate the cost and path for each link. The
cost of each link can also be represented as the weight or length of that link and is set by
the network operator. By suitably assigning link costs, it is possible to achieve load
balancing. If this is accomplished, congested links and inefficient usage of the network
resources can be avoided. Hence, for a network operator to change the routing the only
way is to change the link cost. Generally the weights are left to the default values and it is
recommended to assign the weight of a link as the inverse of the link’s capacity. Since
there is no simple way to modify the link weights so as to optimize the routing in the
network, finding the link weights is known to be NP-hard. LSR protocols offer greater

flexibility but are complex compared to DV protocols. A better decision about routing is
made by link state protocols and it also reduces overall broadcast traffic. The most
common types of LSR protocols are OSPF and IS-IS. OSPF uses the link weight to
determine the shortest path between nodes.
2.13.2 Properties of LSR
 Each router maintains identical database.
 Converges as fast as the database is updated.
 Possibility of splitting large networks into sub areas.
 Supports multiple paths to destination.
 Each router maintains the full graph by updating itself from other routers.
 Fast non loop convergence.
 Support a precise metrics.
2.13.3 Advantages and Disadvantages of LSR
In LSR protocols [4], routers compute routes independently and are not dependent on the
computation of intermediate routers. The main advantages of link state routing protocols
are:
 React very fast to changes in connectivity.
 The packet size sent in the network is very small.
The main problems of link state routing are:
 Large amounts of memory requirements.
 Much more complex.
 Inefficient under mobility due to link changes.
2.14 EIGRP
The Enhanced Interior Gateway Routing Protocol (Enhanced IGRP) is a routing protocol
developed by Cisco Systems and introduced with Software Release 9.21 and Cisco
Internetworking Operating System (Cisco IOS) Software Release 10.0. Enhanced IGRP
combines the advantages of distance vector protocols, such as IGRP, with the advantages

of link-state protocols, such as Open Shortest Path First (OSPF). Enhanced IGRP uses the
Diffusing Update Algorithm (DUAL) to achieve convergence quickly. Enhanced IGRP
includes support for IP, Novell NetWare, and AppleTalk. The discussion on Enhanced
IGRP covers the following topics:
 Enhanced IGRP Network Topology
 Enhanced IGRP Addressing
 Enhanced IGRP Route Summarization
 Enhanced IGRP Route Selection
 Enhanced IGRP Convergence
 Enhanced IGRP Network Scalability
 Enhanced IGRP Security
Enhanced IGRP Network Topology: Enhanced IGRP uses a non hierarchical (or flat)
topology by default. Enhanced IGRP automatically summarizes subnet routes of directly
connected networks at a network number boundary. This automatic summarization is
sufficient for most IP networks. See the section "Enhanced IGRP Route Summarization"
later in this chapter for more detail.
Enhanced IGRP Addressing: The first step in designing an Enhanced IGRP network is
to decide on how to address the network. In many cases, a company is assigned a single
NIC address (such as a Class B network address) to be allocated in a corporate
internetwork. Bit-wise sub-netting and variable-length sub-network masks (VLSM’s) can
be used in combination to save address space. Enhanced IGRP for IP supports the use of
VLSM’s.
Enhanced IGRP Route Summarization: With Enhanced IGRP, subnet routes of
directly connected networks are automatically summarized at network number
boundaries. In addition, a network administrator can configure route summarization at
any interface with any bit boundary, allowing ranges of networks to be summarized
arbitrarily.

Enhanced IGRP Route Selection: Routing protocols compare route metrics to select the
best route from a group of possible routes. The following factors are important to
understand when designing an Enhanced IGRP internetwork. Enhanced IGRP uses the
same vector of metrics as IGRP. Separate metric values are assigned for bandwidth,
delay, reliability and load. By default, Enhanced IGRP computes the metric for a route by
using the minimum bandwidth of each hop in the path and adding a media-specific delay
for each hop. The metrics used by Enhanced IGRP are as follows:
 Bandwidth-Bandwidth is deduced from the interface type. Bandwidth can be
modified with the bandwidth command.
 Delay-Each media type has a propagation delay associated with it. Modifying delay is
very useful to optimize routing in network with satellite links. Delay can be modified
with the delay command.
 Reliability-Reliability is dynamically computed as a rolling weighted average over
five seconds.
 Load-Load is dynamically computed as a rolling weighted average over five seconds.
When Enhanced IGRP summarizes a group of routes, it uses the metric of the best route
in the summary as the metric for the summary.
2.14.1Enhanced IGRP Convergence:
Enhanced IGRP implements a new convergence algorithm known as DUAL (Diffusing
Update Algorithm). DUAL uses two techniques that allow Enhanced IGRP to converge
very quickly. First, each Enhanced IGRP router stores its neighbours routing tables. This
allows the router to use a new route to a destination instantly if another feasible route is
known. If no feasible route is known based upon the routing information previously
learned from its neighbours, a router running Enhanced IGRP becomes active for that
destination and sends a query to each of its neighbours asking for an alternate route to the
destination. These queries propagate until an alternate route is found. Routers that are not
affected by a topology change remain passive and do not need to be involved in the query
and response.

A router using Enhanced IGRP receives full routing tables from its neighbours when it
first communicates with the neighbours. Thereafter, only changes to the routing tables are
sent and only to routers that are affected by the change. A successor is a neighbouring
router that is currently being used for packet forwarding, provides the least cost route to
the destination, and is not part of a routing loop. Information in the routing table is based
on feasible successors. Feasible successor routes can be used in case the existing route
fails. Feasible successors provide the next least-cost path without introducing routing
loops.
The routing table keeps a list of the computed costs of reaching networks. The topology
table keeps a list of all routes advertised by neighbours. For each network, the router
keeps the real cost of getting to that network and also keeps the advertised cost from its
neighbour. In the event of a failure, convergence is instant if a feasible successor can be
found. A neighbour is a feasible successor if it meets the feasibility condition set by
DUAL. DUAL finds feasible successors by the performing the following computations:
2.14.2 Enhanced IGRP Network Scalability:
Network scalability is limited by two factors: operational issues and technical issues.
Operationally, Enhanced IGRP provides easy configuration and growth. Technically,
Enhanced IGRP uses resources at less than a linear rate with the growth of a network.
Memory: A router running Enhanced IGRP stores all routes advertised by neighbors so
that it can adapt quickly to alternate routes. The more neighbours a router has, the more
memory a router uses. Enhanced IGRP automatic route aggregation bounds the routing
table growth naturally. Additional bounding is possible with manual route aggregation.
CPU: Enhanced IGRP uses the DUAL algorithm to provide fast convergence. DUAL re-
computes only routes, which are affected by a topology change. DUAL is not
computationally complex, so it does not require a lot of CPU.
Bandwidth: Enhanced IGRP uses partial updates. Partial updates are generated only
when a change occurs; only the changed information is sent, and this changed
information is sent only to the routers affected. Because of this, Enhanced IGRP is very

efficient in its usage of bandwidth. Some additional bandwidth is used by Enhanced
IGRP's HELLO protocol to maintain adjacencies between neighbouring routers.
Enhanced IGRP Security: Enhanced IGRP is available only on Cisco routers. This
prevents accidental or malicious routing disruption caused by hosts in a network. In
addition, route filters can be set up on any interface to prevent learning or propagating
routing information inappropriately.
Analysis: Now that the <Client> requirements as well as the technical merits and
downfalls of the routing protocols have been defined an analysis needs to be conducted of
this information. The Open Shortest Path First Protocol is an ―open standard.‖ This
means that it can be implemented on any platform, from any vendor or manufacturer.
This is an advantage over Enhanced Interior Gateway Protocol, which is a proprietary
standard from Cisco. However, this is the only clear advantage of OSPF over EIGRP.
As previously stated, OSPF is designed primarily for hierarchical networks with a clearly
defined backbone area. This is clearly not the case in the <Client> network. In addition,
when compared to EIGRP, OSPF uses more bandwidth to propagate its topology requires
more router CPU time and memory. OSPF is also more difficult, and therefore more
costly, to implement that EIGRP.
Enhanced Interior Gateway Protocol is a proprietary routing protocol developed by Cisco
and used exclusively in their routing products. Although it is often lumped in with OSPF
as a link state protocol, it is actually a hybrid; containing the best elements of both link
state and distance vector protocols.
EIGRP, as stated previously, has several advantages over OSPF when used in the
<Client> network. A brief summarization of these advantages includes:
 Improved router memory and CPU utilization when compared to OSPF
 Intelligent bandwidth control – EIGRP takes into consideration the available
bandwidth when determining the rate at which it will transmit updates. Interfaces can
also be configured to use a certain (maximum) percentage of the bandwidth, so that

even during routing topology computations, a defined portion of the link capacity
remains available for data traffic.
 EIGRP does not require a hierarchical network design to operate efficiently. It will
automatically summarize routes where applicable.
Given all of this data and analysis a table is used to consolidate the issues and synthesize
Table 2.1 EIGRP Vs OSPF
Issue EIGRP OSPF
Ease of Implementation Easy, but remember ―no
auto-summary‖
Complicated
Support of IPX and
AppleTalk
Yes No
Standards-based Cisco Proprietary IETF Open Standard
Hierarchical Design No – summary statements
on interfaces
Yes – hierarchy is part of
the design
VLSM Support Yes Yes
Protocol Type Enhanced Distance Vector Link State
Routing Metrics Combination of bandwidth,
delay, reliability and load
Link 10^8/Interface
Bandwidth
CPU Requirements Lower CPU and memory
requirements
Higher CPU and memory
requirements
Maturity Since 1986 Since 1986
Stability Excellent Excellent

 Unlike OSPF, which only takes bandwidth into consideration when calculating the
cost of a route, EIGRP can be configured to use bandwidth, delay, reliability, and
load when calculating optimum routes. This has proven to be a valuable
consideration in a wireless environment.
 EIGRP has greater control on timing issues, such as hold times and hello intervals,
than does OSPF. This allows greater flexibility with wireless connections, where
these intervals must be fine-tuned to a particular device or bandwidth.
 EIGRP is less complex and has less cost (manpower and time) involved in
configuration and administration.
 Although EIGRP is proprietary, it can communicate and redistribute routing
information with other routing protocols, such as OSPF. This is accomplished
through router redistribution or using an exterior routing protocol such as BGP.
2.15 OSPF – IS-IS Comparison:
It is believed that for modern networks and applications that tend to be more and more
demanding in terms of resource consumption and need of low latency, performance
should be a vital factor when selecting a routing protocol. This gets even more important
for dual-stack networks which will be the majority of the enterprise network world, and
which by nature introduce additional performance overhead. This chapter intends to
review the research that has been carried on the comparison of the two protocols when
running over the existing IPv4 networks and on how they cope with IPv6 traffic. It is
expected that this research part will produce some assumptions about the proficiency of
OSPF and IS-IS when configured on dual-stack networks, that can be compared with the
project’s experiment results, in order to lead to safer conclusions.
The comparison of the two protocols has been a matter of debate through the years, but
nowadays the subject still preoccupies the networking community. IS-IS, although used
primarily in ISPs’ networks, is being reviewed by researchers about the possibility of a
broader deployment. A recent publication has attempted to emphasize IS-IS advantages
and why it should be considered as an alternative to OSPF. It is suggested that IS-IS is an
extensible routing protocol that offer huge support to the global IPv6 deployment.

Furthermore, as discussed in the Theoretical Background chapter its hierarchical structure
helps to reduce the exchanged routing information. In terms of security, IS-IS is also
strong, as it supports clear-text authentication by using specialized TLVs, and is
extensible to new authentication forms that are being researched by IETF. Except that, in
comparison to OSPF, IS-IS routing information is not carried over IP but is encapsulated
in layer 2, making a possible attacker task difficult, as they should directly connect to an
IS-IS router to start any malicious activities. Apart from the obvious advantages,
researchers believe that IS-IS also has disadvantages that may have played a role in its
reduced popularity. Notably, IS-IS level 1 adjacencies do not carry external route
information and this can only be done by injecting these routes to the level 2 topology, in
comparison to OSPF that can achieve this goal by using not-so-stubby-areas.
Furthermore, it is noted that IS-IS does not support virtual links like OSPF. However, this
is believed to be of less importance as IS-IS doesn’t require to achieve connectivity with
a backbone area. Back to IS-IS advantages, the LSP lifetime can grow up to 18.2 hours
unlike OSPF that is limited to 1 hour, making this way IS-IS more scalable for bigger
areas. Moreover, IS-IS can make use of the Overload bit to signal memory exhaustion of
a router and also includes a feature that enables routers in full-mesh topologies to receive
only one LSP copy, where OSPF has no such capabilities. Eventually, this research points
out that IS-IS may be a more efficient solution as it can be extended for future needs by
adding new TLVs in comparison to OSPF that needs the creation of new LSAs, by the
most obvious example being that of the IPv4 and IPv6 coexistence capability. It is
suggested that the above discussed characteristics should make the scientific and industry
community reconsider IS-IS place in the networking world, especially for larger
networks.
Even though several research thesis signalize IS-IS superiority, the OSPF - IS-IS
comparison topic is controversial and research thesis that support the opposite also exist.
Based on an example research thesis, OSPF is compared with other IGPs, namely IGRP,
EIGRP and OSPF and is suggested to be better than all of them. This research
emphasizes on the advantages of OSPF due to its hierarchical structure that facilitates
reducing the routing data traffic, as well as on the fast convergence times that it offers.
Thereinafter, it attempts to build a comparative table with the characteristics of each

mentioned IGP in order to conduct a comparison, and conclude to the most efficient of
them. The thesis suggests that OSPF’s greater advantage is that it is open, making
possible this way its deployment to networks that include routers and other network
devices by various vendors. These characteristics are used by the research as arguments
that lead to the conclusion that OSPF is superior to IGRP and EIGRP. However, the
presented comparative table regarding the comparison with IS-IS only presents
differences in the type of the hierarchy format, the Dead Timer times and the metric used,
and no other supremacy points are discussed. Thus, it is believed by the author of the
current project, that this information is inadequate to lead to a conclusion about which
protocol among OSPF and IS-IS is prime.
More than that, another general research review thesis about IGP and BGP protocols
dedicates a part in the popular OSPF - IS-IS comparison. Except the disclosure of the
main characteristics and differences of the two protocols, this research thesis presents a
brief comparison by showing some of their advantages and disadvantages. More
specifically, the research suggests that in OSPF, routers may belong to multiple areas in
comparison with IS-IS Intermediate Systems that belong to only one area, and this fact
results in higher power consumption. Furthermore, it is noted that OSPF area boundaries
fall on the routers where IS-IS area boundaries fall on the links, which could lead in
higher delay times in the sending and receipt of the packets for the latter. Additionally,
IS-IS is considered by the thesis as more flexible because holding timers don’t need to be
identical on all routers. Finally, an argument is made which supports that OSPF is
superior than IS-IS in security terms due to the fact that OSPF runs over IP. However,
this statement is believed by the author of this project to be untrue, as IP is more
vulnerable to various types of attacks and also is more popular and more hackers have
better knowledge of it.
Relatively recent research has been focused on the comparison of the OSPF and IS-IS
protocols in terms of performance in ISPs’ IPv4 networks. This research notes the
importance of selecting the right routing protocol to assure the temporal efficiency of a
network in the distribution of data, as well as the superiority of dynamic routing protocols
over static routing due to the fact that they are able to easily adapt network changes. The

performance comparison of the two protocols has been conducted with the help of the
OPNET modeler network simulator. More specifically, the same topology of 21 routers
spread across different states of the USA, has been configured with each protocol one
after the other in order to produce comparative metrics. The research aimed to produce
results regarding the router and network and router convergence activities and duration
times, as well as queuing delay times on point-to-point links. The results of the
experiment showed that OSPF demands more network activity regarding the messages
sent between the routers until the network has reached convergence, and also the network
and router convergence duration times are 6 and 5 times higher than the ones of IS-IS
respectively. In addition, in the specific experiment IS-IS presented much higher
throughput than OSPF, with the second resulting in lower queuing delays than the first.
The different metric results regarding convergence are possibly related to the hierarchical
format that each protocol is using. More precisely, in OSPF internal routers in an area
have to learn about routes to every possible destination, where internal IS-IS routers only
need to know about the closest level 1/2 IS, speeding this way the network convergence
procedure. Except that, IS-IS only requires the exchange of one LSP during the
convergence procedure where OSPF demands many different LSA types to be exchanged
between the routers.
Although most of the research implies that IS-IS presents better characteristics and
performance than OSPFv2, the performance of OSPFv3 should also be taken into account
when comparing the two protocols, especially nowadays that IPv6 becomes a constant
part of modern networks. One more motive for this research review, is that there is no
published research about the IS-IS – OSPFv3 performance in IPv6 networks. Based on
this fact, researchers have conducted experiments to discover any performance
improvements of OSPFv3 in comparison to OSPFv2. The experiments were implemented
by using OPNET Modeler and by creating a simple OSPF topology including five areas,
specifically two non-backbone areas and a backbone area, and five routers in total. Then,
the same topology was configured separately with OSPFv2 on one occasion and OSPFv3
on the other, and performance metrics were calculated in order to compare the two
protocols’ performance, by running 10 minutes simulations. In terms of convergence

duration and amount of traffic sent, the two versions of OSPF presented similar results.
As far as it concerns the LSDB size, measurements were taken according to the research
on an internal router, and the results showed that OSPFv3 LSDB is 27% smaller than the
OSPFv2 LSDB. Such behaviour can be explained due to the fact that OSPFv3 does not
store any network addresses carried in Router LSAs in the LSDB. Moreover, even if IPv6
addresses are bigger than IPv4 ones, similar measurements were taken for memory
consumption for both protocols, fact that may be explained by the facilitating role of the
OSPFv3 Link LSA. However, OSPFv3 presents greater routing table sizes due to the
inclusion of both global unicast and link-local unicast addresses, and it was also proved
that it produces more updates than OSPFv2 in case of a router failure. (Chen Haihong,
2013) Eventually, this research suggests that OSPFv2 and OSPFv3 present similar
performance and predicts that OSPFv3 will be one of the most popular routing protocols
in the near future due to its effectiveness. Nevertheless, important metrics such as
throughput and round-trip delay have not been measured in order to produce more clear
results.
2.16 IS-IS (Intermediate System to Intermediate System Routing
Protocol)
The IS-IS is also a link-state routing protocol with several similarities with OSPF
protocol, such as the use of the same SPF algorithm. It was defined by ISO (International
Organization for Standardization) and tagged as ISO 10589, in an attempt to implement
DECnet Phase V of Digital Equipment Corporation for large networks. Although it was
initially designed to work with CLNP (Connectionless Network Layer Protocol), it was
later in 1990 modified to also route IP as defined in RFC 1195 by the name Integrated IS-
IS. Opposite to all other IGPs that were created based on the TCP/IP protocol stack, IS-IS
is based on the primer OSI (Open System Interconnection) reference model. As a result
IS-IS was not initially build to support the IP protocol but the OSI layer 3 CLNP
protocol, which offers network services to the upper layers. More specifically, CLNP, IS-
IS and ES-IS (End System to Intermediate System) routing protocol all lay on OSI’s
network layer and are being encapsulated in different frames at the data-link layers.
Except this difference, IS-IS also uses a different terminology. Routers are defined as

intermediate systems, hosts as end systems, routing as routeing and packets as PDUs.
Nowadays, it is a less common protocol than OSPF but still is the favourite choice for
many Internet Service Providers’ backbone networks. More than that, IS-IS doesn’t need
to be upgraded to a new version in opposition to OSPF, because it can easily adapt the
carriage of IPv6 addresses as it will be discussed later on the thesis. Generally, as a link-
state protocol, IS-IS is considered to be an IGP with fast convergence time and stability,
as well as low resources consumption.
2.16.1 Addressing
Either being used to route CLNP or IP, IS-IS remains an OSI protocol and demands the
assignment of an OSI address on every Intermediate System, and not on interfaces. These
addresses are called NSAPs (Network Service Access Points), their length varies from 8
to 20 bytes and are usually written in hexadecimal. They consist of three main fields: the
Area ID which defines the IS-IS area where the IS resides, the System ID which is unique
for every device and commonly is assigned the MAC address of the device, and the N-
Selector (SEL). The latest field defines the user of the network service. At the most usual
situation where an NSAP address is assigned to an IS, the N-Selector takes always the
hex-value 0x00. Every such IS address is also called NET (Network Entity Title). ISs
assigned with addresses including the same Area ID field value belong to the same area
and moreover, a single IS can be assigned more than one NET addresses as long as the
Area ID changes and the System ID stays identical. NET addresses always start and end
with a single byte. It has to be noted that except this format, another two formats are
present, the OSI and the GOSIP format. The first one adds to the address a Routing
Domain Part, where the second adds six fields, namely AFI, ICD, DFI, AAI, Reserved
and RDI.
2.16.2 Hierarchy
Like OSPF and as a link-state protocol, IS-IS also uses the concept of splitting the entire
IS to smaller areas. The motivation behind this technique is again to limit the
consumption of CPU and memory resources at the ISs by minimizing their databases and
give them a relief when executing the SPF algorithm. Additionally, dividing into areas

facilitates route summarization at the areas’ edges in order to also minimize routing
tables. On the other hand, unlike OSPF, IS-IS only defines one type of area. The basic
differentiate characteristic is the lack of a backbone area. More specifically, areas do not
need to be connected physically or logically to a specific area. This specificity of IS-IS
makes it more scalable to larger networks and easier to adapt to any subnet additions.
However, as routing roles are not dependent on the area type, IS-IS includes another
feature to define routing hierarchy and manage the way routing is performed. This is
accomplished with the introduction of levels.
2.16.3 Levels
IS-IS includes two levels of hierarchy, level 1 and level 2. The first is used to characterize
intra-area routing where the second is used for inter-area routing. Level 1/2 is used for
both types of routing. Every IS is defined by one of these levels, depending on its role in
the topology, and so are its links. The level of every IS also defines the type of
relationship that will be formed with the IS-IS configured ISs.
Level 1: More specifically a level 1 IS contains only a level 1 Link-State Database
including the topological information of its own area. Level 1 ISs must have the same
Area ID to create an adjacency between them. The level 1 IS topology is very similar to
an OSPF stub-area, as no inter-area routes are injected to level 1 ISs’ routing tables.
Instead, a default route is injected in order for them to be able to reach destination outside
their area. However, even that is the default behaviour, IS-IS can be configured to leak
inter-area routes inside a level 1 topology.
Level 2: On the other hand, level 2 ISs contain a level 2 Link-State Database only. This
means that level 2 IS’s have knowledge of the topological information of other IS-IS
areas but not from theirs. More than that, Area IDs of level 2 routers do not have to match
in order to form an adjacency. However there is no way that a level 2 router is isolated
from the other level 2 routers. An area containing only level 2 routers can be considered
as similar to the OSPF backbone area, as far as it concerns its functionality that includes
spreading routing information from one area to another. However, this theoretical

backbone can be extended with the addition of another level 2 or level 1/2 IS, and any
connection to it is not mandatory. It has to be noted here, that an area containing only
level 2 routers can exist only in IP routing environments and not in solely OSI routing
networks.
Level 1/2: In IS-IS, an IS can belong to only one area so there is no ABR router concept
in terms that it has interfaces to more than one area. However an IS can be configured as
level 1/2. This means that such an IS stores both a level 1 and level 2 Link-State
Databases and is able to form adjacencies with all level 1, level 2 and level 1/2 ISs.
Figure. 2.2 IS protocol’s PDUs
Therefore, a level 1/2 IS contains topological information of the area it resides in and
also of other areas. Communication with a level 1 IS leads to the update of the level 1
database, communication with a level 2 IS leads to the update of the level 2 database and
accordingly communication with another level 1/2 will update both Link-State Databases.
This feature makes a level 1/2 IS simulate the behaviour of an ABR in OSPF. The level
1/2 IS is usually placed at the edge of the area, and is responsible for forwarding packets
from the area’s level 1 ISs to inter-area destinations.
PDU Types: The IS-IS protocol makes use of three main categories of PDUs (Protocol
Data Units) in order to establish neighbour relationships and manage the distribution of
routing information between ISs. These three categories include Hello packets, Link-
State Packets (LSPs) and Sequence Number Packets (SNPs). Each of these PDU

categories has a slightly different header format but the first eight fields with eight byte
length in total are identical for every one of them. Thus, every PDU consists of its header
and various TLVs (Type, Length, Value). TLVs have variable length and depending on
their numeric value, they describe the information that the PDU-packet carries. More
specifically, the Type part consists of a numeric code to define the type of the TLV, the
Length shows the actual length of the TLV and the Value part defines the content. The
following figure shows the common header part for every PDU sub-category. The fields
Intra-domain Routing Protocol Discriminator, Version/Protocol ID Extension, Version
and Reserved are fixed and have the decimal values 131, 1, 1 and 0 accordingly. Length
Indicator and ID Length fields define the header length and System ID length, where the
PDU Type field shows the category that the PDU belongs to. Finally, the Maximum Area
Addresses field defines the size of the IS-IS area.
Hello Packets: Hello packets are exchanged between ISs during neighbour discovery in
order to start forming adjacencies, and vary depending on the type of the link as well as
the type of the routing relationship. For broadcast links there are two subcategories. First,
level 1 LAN IIHs (Intermediate System to Intermediate System Hello packets) are used
in broadcast links which connect ISs in order to form a level 1 adjacency. On the other
hand, level 2 LAN IIHs are exchanged on the same type of links but for level 2 adjacency
establishment. On point-to-point links, point-to-point IIHs are used to form both level
1and level 2 adjacencies. Not to be confused by these categories, are the ESH (End
System Hello) and ISH (Intermediate System Hello) packets, which are being sent and
received between hosts and routers in order to discover each other. IS circuits can be
configured to allow or ban a specific type of Hello packets in order to optimize
performance.
Link-State Packets: LSPs, referred also as Link-State PDUs, have exactly the same
functionality that LSA packets have in OSPF. In IS-IS LSPs come in two versions,
depending on the routing information that they carry, having however the same packet
format. Specifically, level 1 LSPs are flooded by each IS within their area in order to
inform the rest ISs about their adjacent routers, their attached IP subnets (when talking
about Integrated IS-IS) and carry area, metric and authentication information. Level 1

Link-State Databases are built by them in the area and are identical at the time of
convergence. The second category consists of level 2 LSPs which are exchanged between
level 2 ISs by neighbour flooding, and carry information about the level 2 topology.
Thus, the level 2 Link-State Database is updated by their facilitation on the
communicating ISs. It has to be noted that level 1/2 ISs produce both types of LSPs.
Sequence Number Packets: SNPs are used to facilitate the Link-State Database
synchronization between ISs. They come in two forms, CNSPs (Complete Sequence
Number Packets) and PNSPs (Partial Sequence Number Packets), and each one of them
is divided in level 1 and level 2 sub-categories depending on which Link-State Database
they are describing accordingly, just like LSPs. CNSPs contain a summary of every LSP
in the Link-State Database that includes an LSP Identifier, a Sequence Number, a
Checksum and a Remaining Lifetime field. CNSPs are exchanged once during the
establishment of an adjacency and before any other LSPs have been exchanged. This way
ISs are informed about the topological information that each one of them contains. For
broadcast networks, CNSPs are only sent by the Designated IS of the network. On the
other hand, PSNPs contain only summaries about a specific LSPs and facilitate the Link-
State Database synchronization procedure, either as requests for missing LSPs or to
acknowledge receive LSPs.
Network Types: In opposition to OSPF, IS-IS supports only two types of networks,
point-to-point and broadcast. Adjacencies on NBMA networks can also be accomplished
without problems, if configured as a series of point-to-point links.
Point-to-Point Networks: Same as in OSPF, point-to-point links are used in IS-IS to
connect a single pair of ISs. CNSPs are exchanged between the two ISs in order to
synchronize their Link-State Databases that is maintained alive by the periodical
exchange of Hello packets.
Broadcast Networks: Broadcast networks are multi-access networks that support both
broadcasts and multicasts. In every broadcast network, a Designated IS (DIS) is elected,

that plays a similar role to a DR in OSPF. The election process is based on link
configured priorities that have a default value of 64, and in the case of a tie, the IS with
the higher MAC address wins the election. In contradiction to OSPF, there is no Backup
Designated IS, and a new election must be performed if the DIS goes down. In IS-IS, a
Broadcast Network is considered a pseudo node in the Link-State Database and every IS
in it has to advertise a link to it. The DIS has the role of flooding the LSPs and Hello
Packets for the pseudo node except its own packets, and establishing and maintaining
adjacencies. Of course, different DISs are elected for level 1 and level 2 topologies and
the two may be the same or vary.
Operation
As IS-IS is based on OSI model, its functions are divided to two categories that resemble
the two sub-layers of the OSI network Layer, the sub-network dependent layer and the
sub-network independent layer. The most vital functions of each sub-layer are presented
below.
Sub-network Dependent Layer
Discovery: The first step in IS-IS operation is the discovery of the ISs by the hosts and
vice versa, which is achieved as mentioned by the exchange of ESH and ISH packets.
The next step is the establishment of adjacencies.
Neighbouring Process: ISs send, every 10 seconds by default, Hello packets on their
attached interfaces, declaring this way their identity and capabilities as well as the
parameters of the link. If the two ISs agree on the parameters, they become adjacent.
Unlike OSPF, it is not demanded for all capabilities to match in order to form an
adjacency. For example Hello interval times may vary on the two ISs but the adjacency
will be established. As described above, adjacencies are level 1 and level 2. For level 1,
Area IDs must match where for level 2 that is not necessary. After the adjacency is
established, Hello packets are still used to maintain it as keep-alive messages. Moreover,
a Hold Time value is included in the Hello packets in order to inform neighbour about the
time they need to wait until they should declare the sending IS as dead. Finally, two ISs

are fully adjacent only when the Link-State Database synchronization is accomplished.
Hello packets are multicoated to all neighbours even by ISs that belong to the same
broadcast network, with the elected DIS sending the appropriate SNPs to ensure the
reliable transfer of LSPs.
Sub-network Independent Layer
Link-State Database Update: After the Hello packets have been exchanged and the
agreement between the ISs is set, level 1 LSPs are flooded within the area and level 2
LSPs are sent to all level 2 adjacent ISs, so that the level 1 and level 2 IS Link-State
Databases are updated. On point-to-point networks LSPs are sent directly to the
corresponding ISs, where in broadcast networks, LSPs are multicasted to the multicast
MAC addresses 0180.c200.0014 and 0180.c200.0015 for level 1 and level 2 respectively.
LSPs contain a Sequence Number that starts from the value of 1 and is incremented by
one in every new instance of the LSP until it reaches the maximum value, where IS-IS
stops for a period in order for the LSPs to age in Link-State Databases. They also contain
a Checksum value, and a Remaining Lifetime field that starts from 0 and rises to a
MaxAge value (1200 sec. by default), and defines when the LSP is going to be deleted
from the Link-State Database if not refreshed. As mentioned in a prior section, CSNP
summaries are sent periodically in order to synchronize the Databases with newer LSPs
and PSNPs are sent for acknowledgement and request of needed LSPs. In a broadcast
network the CSNPs are sent by the DIS.
Shortest Path First Algorithm: IS-IS uses the same SPF algorithm as OSPF in order to
build an SPF tree and calculate the shortest routes to the known destinations. After the
Link-State Database update procedure has finished, the ISs run a separate instance of the
SPF algorithm for the level 1 and level 2 databases, depending of course on which of
them do they support. The difference with OSPF resides on the metric used to perform
the calculations. More specifically, IS-IS uses a metric called default, which takes the
default value of 10 for every link. It also supports three optional metrics, namely delay,
expense and error that characterize the delay, the actual cost and the error rate of the link
respectively. However, using all metrics is not recommended as the SPF algorithm has to

be run separately for each one of them increasing this way the CPU and memory
overload. By running the SPF algorithm, ISs calculate the level 1 and level 2 routes and
inject them into their routing tables.
2.17 Integrated IS-IS:
IPv4 Capability: As TCP/IP model dominated in the networking world over OSI model,
and therefore IP is established as the most popular layer 3 routed protocol. As discussed
in the beginning of the IS-IS sector in the thesis, even if IS-IS was initially build to route
CLNP, it was modified to also support IP in order to be useful in modern networks and
was renamed to Integrated IS-IS, mostly referred simply IS-IS. More precisely, IS-IS
protocol is capable to provide routing functions to OSI environments, IP environments
and Dual environments. However, the routers have still to be configured with OSI
addresses in every case. Integrated IS-IS routing operation has no difference from the
initial IS-IS operation. However, IP routing information is also carried within the Hello
Packets and the LSPs in order to distribute IP destinations so that they can be reached.
This feature is achieved with the addition of new IP-specific TLVs to the routing packets.
In more detail, Hello packets include a Protocol Supported field, in order to declare that
the sending ISs support IP. More than that IS-IS Hello packets include the IP address of
the interface of neighbour ISs because ICMP Redirect messages to end systems must
include the next-hop address. Thus, every Hello packet includes the IP address of the
interface where it is send on. Additionally, in order for the ISs to have knowledge of the
attached IP networks for the rest ISs in their areas, LSPs are modified to contain a group
or all of the IP interface addresses on the IS. As there are Level 1 and Level 2 LSPs, both
of these types include the same IP addresses. The TLV including this information is
called IP Interface Address TLV. Additionally, level 1 ISs learn routes for the attached IP
subnets of other ISs in the area, and level 2 ISs know which IP addresses are reachable
inside the level 1 topology. Except the IP address, IP reachability information also
includes the Subnet Mask and a metric. Eventually, depending on the level of the LSP,
this information is carried either inside an IP Internal Reachability Information TLV for
level 1 and inside an IP External Reachability Information TLV for level 2.

IPv6 Capability: The adaptability of the Hello packets and LSPs to be modified to
include extra TLV fields, has given a huge advantage to IS-IS to the point that it can
carry newer addressing schemes network addresses without changing at all the operation
of the protocol. Therefore, the upcoming arrival of IPv6 found IS-IS almost ready, in
contradiction to OSPF that needed to be extended to a completely new version.
Specifically, another TLV was added to the IS-IS routing packets, equivalent to the ones
for IPv4. This TLV is named IPv6 Reach ability TLV and includes the global IPv6
addresses prefix, a metric and two bits to signify if the routing information comes from a
higher Level or from another routing protocol. Finally, the IPv6 equivalent TLV for the
IP Interface Address TLV is called IPv6 Interface Address TLV and it has identical
format, except the fact that it is modified to contain 16-byte long IPv6 addresses.
2.18. Simulation and Simulation Tools:
Simulation is three phase process which includes the designing of a model for theoretical
or actual system followed by the process of executing this model on a digital computer
and finally the analysis of the output from the execution. Simulation is learning by doing
which means that to understand/ learn about any system, first we have to design a model
for it and execute it. To understand a simulation model first we need to know about
system and model. System is an entity which exists and operates in time while model is
the representation of that system at particular point in time and space. This simplified
representation of system used for it better understating. In wireless sensor network there
are many simulation tools are used for simulation purpose describe as below:
A. NCTUns: NCTUns (National Chiao Tung University Network Simulation) is a
simulator that combines both traffic and network simulator in to a single module
that built using C++ programming language and support high level of GUI
support. It is a highly extensible and robust network simulator in no need to be
concerned about the code complexity.
Features:

 It can simulate many standards such as IEEE 802.11a, IEEE 802.11b,
IEEE 802.11e,IEEE 802.16d, IEEE802.11g and IEEE 802.11.
 It supports large number of nodes.
 It includes directional, bidirectional and omni directional communation.
Figure 2.3: Graphical user interface of NCTUns.

Figure 2.4 : NCTU ns simulator. The architecture of NCTU ns 6.0 network protocol
simulation.
B. NS-2(Network Simulator): Network Simulator (Version 2), called as the NS-2,
is simply an event driven, open source ,portable simulation tool that used in
studying the dynamic nature of communication networks.
Basic Architecture of NS-2: In the Figure2.17 represent the basic architecture of
NS-2. It provides ns executable command to its users to take input argument
.Users is feeding the name of a TCL simulation script as an input argument of NS-
2 executable command ns.
Fig. 2.5 Architecture of NS

NS-2 consists of two key languages one is the C++ and second is the Object-oriented
Tool Command Language (OTCL). In NS-2 C++ defines the internal mechanism
(backend) of the simulation objects, and OTCL defines external simulation environment
(i.e., a frontend)for assembling and configuring the objects. After simulation, NS-2 gives
simulation outputs either in form of text-based or animation-based.
C. OPNET (Optimized network engineering tool): OPNET is a commercial
network simulator environment used for simulations of both wired and wireless
networks. It allows the user to design and study the network communication
devices, protocols and also simulate the performance of routing protocol. This
simulator follows the object oriented modelling approach. It supports many
wireless technologies and standards such as, IEEE 802.11, IEEE 802.15.1, IEEE
802.16, IEEE 802.20 and satellite networks.
OPNET Architecture: OPNET provides a comprehensive environment to model
and do performance evaluation of networks and distributed systems. The OPNET
package includes numbers of tools. Those tools fall into three categories
corresponding to the three phases of modelling and simulation projects:
Specification, Simulation and Data Collection, and Analysis. These phases should
necessarily be in sequence and form a simulation cycle as in Figure 2.6. OPNET
uses the concept of modeling domains to represent its modeling environments,
and graphical editors for editing the Network, Node and Process models.
Specifically, there are several editors in OPNET: project editor, node editor,
process editor, external system editor, link model editor, packet format editor,
Interface Control Information editor, and probability density function editor.
Network Domain is used to define the network topology of a communication
network. The communicating entities are called nodes. Network domain is created
by using the Project editor tool of the OPNET modeller.
Node Domain describes nodes’ internal architecture in terms of functional
elements in the node and data flow between them.

Re-Specification
Data Collection
And
Simulation
Analysis
Initial Specification
Figure 2.6 : Simulation Cycle in OPNET
Process defines the behaviour of processes, including protocols, algorithms and
application, specified using infinite state machines and an extended high-level language.
External System specifies the interfaces to the models provided by other simulators
running concurrently with an OPNET simulation (a co-simulation).
OPNET Modeler Wireless Support
The Wireless module in OPNET provides a flexible and scalable wireless network
modeling environment, including a broad range of powerful technologies. The Wireless
module integrates OPNET’s full protocol stack modeling capability, including MAC,
routing, higher layer protocols, and applications, with the ability to model all aspects of
wireless transmissions, including:
- Radio Frequency propagation (path loss with terrain diffraction, fading, and
atmospheric and foliage attenuation)
- Interference
- Transmitter/receiver characteristics

- Node mobility, including handover
- Interconnection with wire-line transport networks
The wireless module has rich protocol model suites to optimize the R&D processes, and
more effectively design technologies such as MANET, 802.11, 3G/4G, Ultra Wide Band,
802.16, Bluetooth, and Transformational Communications systems. Wireless network
planners, architects, and operations professionals can analyze end-to-end behaviour, tune
network performance, and evaluate growth scenarios for revenue-generating network
services.
Why use OPNET
A good modeling tool should closely reflect the true behavior of a network or computer
system. It should support a wide range of network protocols and applications. It must be
easy to use and master, especially for beginners. On the other hand, a good modeling tool
should provide comprehensive technical support and maintenance assistance. In
summary, we believe that a good modeling tool should have the following properties:
Versatile: able to simulate various network protocols/applications under a wide range of
operating conditions [26].
Robust: provide users with powerful modeling, simulation and data analysis facilities.
User Friendly: easy to use and master [26].
Traceable: easy to identify modeling problems and simulation faults [26]. OPNET is
hailed by network professionals because it has all these properties. OPNET is a software
package that has been designed with an extensive set of features. It can be tailored to suit
almost every need of network protocol designers, network service providers, as well as
network equipment manufacturers. OPNET supports most network protocols in
existence, both wire line and wireless. It can be used to model and analyse a complex
system by performing discrete event simulations [26].
OPNET Capabilities
OPNET has a lot of capabilities. Some of these capabilities are the following:
Hierarchical Network Models: Manage complex network topologies with unlimited sub-
network nesting [27].

Object Oriented Modeling: Nodes and protocols are model as classes with inheritance
and specialization [27].
Clear and Simple Modeling Paradigm: Model the behavior of individual objects at the
process level and interconnect them to from devices at the ―Node Level‖ ; interconnect
devices using links to form networks at the ―Network Level‖ [27].
Finite State Machine Modeling: Finite state Machine modeling of protocols and other
processes. Simulate arbitrary behavior with C/C++ logic in FSM’s states and transitions.
You control the level of detail [27].
Comprehensive Support for Protocol Programming: 400 library functions support and
simplifying writing protocol models [27].
Wireless, Point-to-Point and Multipoint Links: Link behavior is open and
programmable [27].
Geographical and Dynamic Mobility Modelling: It is for mobile and satellite systems
[27].
Total Openness: API’s from program-driven construction or inspection of all models and
result files. Easily integrate existing code libraries into your simulations [27].
Integrated Analysis Tools: Display simulation results. Easily plot and analyze, time
series, histograms, probability functions, parametric curves, and confidence intervals.
Export to spreadsheets [27].
Animation: Animation of model behavior, either during or after simulation [27].
Integrated Debugger: Integrated debugger to quickly validate simulation behavior or
track down problems [27].
Import Data from Some Popular Tools: Such as HP Open View and Network
Associated Sniffer [27].
Comprehensive Library of Detailed Protocol Models: Including ATM, Frame Relay,
TCP/IP, RIP, OSPF, BGP4, IGRP, Ethernet, FDDI, Token Ring, and many more.
Provided as FSM’s with source code [27]
Run Time Environment (Modeler XE): Deliver proprietary protocol and device models
to end-users, working and running simulations at the network level only [27].
Solaris, Windows NT, and HP-UX: Supported (Transparent cross platform usage)
Flexible Licenses: Floating license (concurrent use based), and loan able license

Figure. 2.7 OPNET-A Powerful Network Simulation Tool
c) GloMoSim (Global Mobile Information System Simulator); GloMoSim (Global
Mobile Information System Simulator) is a scalable simulation environment especially
designed of MANET and its applications. It is open source, portable and includes a large
set of routing protocols and several physical layer implementations. It was retired in 2000
but it is still possible to download for educational purposes only. On the other side,
Scalable Network Technologies introduced the commercial version of GloMoSim
(Global Mobile Information System Simulator) named as QualNet (Quality Networking)
simulator. The main merits of QualNet simulator (Quality Networking), is that it is open
source portable, highly scalable and extremely powerful simulator. One of the main
merits of QualNet, is that it is run on both Windows and Unix/Linux platforms.
d.) QualNet (Quality Networking): QualNet is a highly scalable, fastest simulator for
large heterogeneous network It supports the wired and wireless network protocol.
QualNet execute any type of scenario 5 to 10 times faster than other simulators. It is
highly scalable and simulate up to 50,000 mobile nodes. And this simulator is designed as
a powerful Graphical User Interface (GUI) for custom code development. one of the main
advantage of QualNet is that it supports Windows and Linux.

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