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Voice over Cable Networks:
Accessing Internet using Cable modem is one of the recent
technological advancements in the field of networking. Cable
network has widely deployed infrastructure and is most
commonly used to distribute television programs. Utilizing the
existing cable network (coaxial cable entering subscribers’
premises) to provide Internet access has opened up a
completely new paradigm. Cable modems used in the Cable
networks provide line speeds of 300kb/s and above for Internet
access in addition to distributing television programs
(video). Introducing IP telephony over Cable network
introduces many new challenges like quality of service and
security. In this research, we evaluate the performance of IP
telephony over a Cable network using OPNET network simulator.
Validation of MPLS Module Implemented in
OPNET:
MPLS is an emerging technology that combines layer 2 switching
performance with layer 3 scalability. MPLS assigns
labels to packets for transportation across a packet-switched
or a circuit-switched network. The forwarding mechanism in a
MPLS network is based upon label swapping in which every
packet (or cell) carries a short label that indicates the
manner in which the packet (or cell) needs to be processed.
The benefits of MPLS include, among others, scalable support
for Virtual Private Networks (VPN) and Constraint Based
Routing (CBR) for effective deployment of Traffic Engineering
(TE). The current work explores the various capabilities of
MPLS module implemented by OPNET.
Study of the Circuit
Switched Module in OPNET 8.0:
VoIP is an emerging technology aimed at leveraging the
benefits offered by an IP network for both voice and data
transmission. The integration of voice and data traffic
onto a single network is led by a demand for multi-service
applications over the global Internet. Even though the
possibility of toll-bypass could result in considerable
savings in long-distance calls, networks deploying VoIP face
challenges in terms of packet loss, delay, scalability,
reliability, inter-operability and lack of uniform standards.
The Circuit Switch model within OPNET was used in the current
work to quantify the performance of a VoIP network used in
conjunction with a PSTN network. This study is tuned towards
providing an easier migration path from a pre-dominantly
circuit-switched telephony network to a converged network
infrastructure. The focus of the current work is on the
evaluation of the circuit switched model within OPNET 8.0 with
respect to call priorities and call re-routing during the
migration process.
Impact
of RM Cell Frequency on ABR Feedback Schemes:
Master's Thesis by Shajith Moosa. Spring 2000.
Asynchronous
Transfer Mode (ATM) is potentially capable of supporting all
classes of traffic (e.g., voice, video etc) in one
transmission and switching technology. ATM networks have
mutliple service classes that allow audio, video and data to
share the same network. Of these, the Available Bit Rate (ABR)
service class is designed to efficiently support data
traffic. Lately, investigations have been going on to make
use of the ABR service to transport real-time multimedia
applications. The success of this approach depends on
minimizing the rate variations of ABR in order to provide
low variations in Quality of Service (QoS). ABR sources send
a Resource Management (RM) cell after it has sent [Nrm -1]
number of data cells (where Nrm is the number of data cells
sent between 2 RM cells). One way to minimize the rate
variations is to send the feedback RM cells less frequently,
i.e., Nrm should be large. The Nrm value needs to be chosen
carefully in order to obtain minimum oscillations in the
Allowed Cell Rate (ACR) and yield smaller maximum queue
lengths. The choice of an optimum Nrm value becomes an
interesting problem when we consider a heterogeneous network
with the Explicit Forward Congestion Avoidance Indication (EFCI)
and the Explicit Rate Indication for Congestion Avoidance
(ERICA) schemes. This thesis presents the results of an
investigation to find an optimum Nrm value for ERICA and
EFCI schemes. Results show that the ACR settles to an
optimum value for Nrm values as low as 8. But Nrm values
lower than this give very high control overhead and are
hence not advisable. The lower Nrm values also cause high
frequency of rate variations in the EFCI schemes.
Selection of Appropriate Data Network for Transferring Voice
Traffic: Master's Thesis
by Manish Sehgal. Spring 2000
Data traffic is
increasing at a much higher rate than voice traffic. This is
driving the enterprises to consolidate their voice and data
networks. There are different technologies for transferring
voice over data networks. In this research, we have
attempted to develop guidelines for selecting the
appropriate data network protocols for transferring
consolidated voice and data traffic. Performance of IP and
ATM networks was compared for different kinds of traffic. In
order to check the performance of IP and ATM networks,
several tests were conducted using the OPNET simulator. The
effects of various voice parameters on network performance
were evaluated. Degradation in voice quality was inspected
under different network conditions. The results show that
the selection of the appropriate data network protocols for
transferring consolidated voice and data traffic is
dependent on the amount of voice traffic and the Quality of
Service (QoS) required. It was concluded that the voice
parameters, coding techniques and link speeds affect the
network performance differently for IP and ATM networks.
Analysis of
Mobile network performance analysis:
Recent
advancements in the Wireless networking hardware have
resulted in the increased popularity of wireless networks.
Although wireless network hardware vendors claim high degree
of quality, it is not equivalent to the wired network.
Unlike wired links, wireless mobile network performance is
affected by many factors other than congestion. In a
wireless LAN, factors like multi path fading, link errors
and distance between the access point and the mobile client
affect the quality. In a highly error prone wireless link,
the fragmentation further deteriorates the performance.
This
project aims at quantifying the effect of fragmentation and
the buffer size (of the mobile client) on the mobile client
traffic. In the process, the researchers also analyze the
effect of the distance between the access point and the
mobile client and the mobility on the quality of client
traffic. OPNET Modeler 8.0 and OPNET Modeler 9.0 were used
to simulate Wireless networks.
Performance
Comparison of TCP over wired and wireless using OPNET:
In this project an attempt has
been made to
compare the performance of TCP over wired and
wireless networks using the network simulator package OPNET
8.0. Standard and custom applications like ftp, HTTP and Data
have been used for this purpose. In order to determine the
performance of TCP under differing conditions, simulations
were run with varied values of parameters like: receive buffer
size, data rate and packet discard ratio. Similar simulations
were run for both wired and wireless scenarios. The
corresponding values of TCP-delay, throughput time and
response time were recorded and the results were analyzed.
DSL VS CABLE: A Comprehensive
comparison:
DSL and Cable are the two
emerging technologies providing high bandwidth Internet
connectivity for both home and home-office users. Both DSL and
cable provide enough bandwidth (much higher compared to a 56K
dial up connection), fulfilling the needs of many domestic
users for video conferencing and voice applications. Although
DSL and cable services are affordable, several factors like
distance from the service provider, number of active users,
security, and manageability in terms of maintaining
connections and equipment to provide reliable connectivity
affect the quality of service. In this paper, the authors
compare these technologies from both – the service provider
and the customer’s perspective.
Validation of
Multicast Networks implementation in OPNET:
Multicasting is an emerging WAN technology intended for
group-oriented transmissions. Multicasting is developed based
on a group concept where an arbitrary group of users forms a
set, irrespective of their physical and geographical location.
Multicasting uses Internet group management protocol (IGMP) to
relay information between users. One of the main advantages of
multicasting is bandwidth conservation. It can support a
variety of applications involving real-time requirements such
as video conferencing, distance learning, stock quotes, and
storage area networks (SANs). In this paper, the authors
compare the performance of multicasting over unicasting and
validate the results by duplicating the scenarios using real
world equipment.
Coordinated
multihop scheduling - An OPNET implementation:
Quality of service is one of the major issues on which the
networking world is concentrating today. While there are many
different techniques that have been proposed to improve the
quality of service (QoS), most of them act on a single node,
independent of rest of the network. Although this would ensure
QoS to certain extent, issues like jitter and maintaining the
delay bound are not properly addressed. In this paper, the
authors make an effort to address these two issues by
establishing coordination between various nodes in the
network. Through such coordination, the next hop router can
schedule a datagram such that the additional delay caused in
the previous node may be compensated to certain extent.
State based
service differentiation for improving TCP performance over
wireless networks:
In traditional computer networks, service differentiation is
done based on application flows. This results in high packet
loss for low priority traffic flows. If the low priority flows
are TCP based applications then the packet loss results in
increased congestion due to the additional overhead of
connection reestablishment, retransmit and recovery mechanism.
The effect of the traditional service differentiation will be
more severe in the case of wireless networks since in wireless
networks the datagram drops may even be caused due to link
errors. In this paper, the authors discuss an alternative
approach that will improve the performance of TCP flows (both
high priority and low priority) without affecting the QoS for
high priority traffic.
Issues in
Deploying Wireless Networks:
Wireless Networking is becoming more important in the present
day market as compared to any other technique. New protocols
are being designed and tested for the proper functioning of
wireless communications. Demand for accessing the information
from anywhere, anytime has increased, and mobile devices are
becoming more common. Although there are many advantages with
wireless networking, limited available resources are a major
constraint. Multimedia applications requiring guaranteed
service are being restricted, and the speed of wireless
communication has reduced with the increase in the number of
users. In addition, the performance of a wireless network
decreases when different nodes operate at different data
rates. In this paper, the authors investigate the effect of
buffer size, fragmentation, and interleaving along with the
effect of having hosts operating at different data rates,
using OPNET network simulator.
Ad-Hoc Routing Protocol
Performance Evaluation:
An ad hoc network can be considered as a collection of mobile
nodes that dynamically form a temporary network in the absence
of an infrastructure of any kind or centralized administration.
Various routing protocols were proposed for networks of this
nature. DSR and TORA are two prominent Ad-Hoc routing protocols
that are being widely accepted. Both the routing protocols have
their own advantages and disadvantages. It is important to
determine the suitable routing protocol for the given scenario.
Hence the performance of the two routing protocols under various
network conditions was measured and compared. The parameters
considered were the packet loss, throughput and average delay.
It is observed that the routing protocols performed as expected
and the authors were able to segregate the routing protocols
based on their usage and characteristics. No single protocol
had a complete advantage over the other, the performances varied
as per the network. The protocols that discover routes on the
fly are found to perform the best in scenarios involving high
mobility. The protocols that tend to have message complexity
had a deteriorated performance.
PCF vs DCF: A Performance
Comparison:
Wireless LANs are gaining importance at a very rapid pace. The
idea of being mobile and being connected to the infrastructured
network is driving new innovations in this area. With the recent
innovations in the field of Multimedia over Internet, the
requirements of QoS support over Wireless LAN are becoming more
stringent. Quality of Service in a wireless LAN is affected by a
number of parameters like channel access method,
physical/environmental conditions, number of nodes, distance
etc. A proper selection of protocols/topology could help in
maintaining/improving the QoS support of a wireless network. In
this research work, the researchers analyze the effect of
channel access method on the multimedia (voice) traffic. Two
channel access methods, namely Point Coordinate Function (PCF)
and Distributed Coordinated Function are for their QoS support.
In the process of comparison, the authors have also studied the
impact of codec selection on the network performance. The
simulations were carried out using OPNET network simulator.
Parameters like number of simultaneously supported voice calls,
voice end-to-end delay, packet drop percentage were considered
for comparison. In addition, the effects of multimedia traffic
on the data traffic were also analyzed both analytically as well
as through simulations. The simulation results indicate that
using PCF for multimedia traffic would result in better
performance.
Study of Mobile IP Module in OPNET
Network Simulator: Mobility
support for communication nodes is one of the most explored
fields in today’s networking research world. While the initial
attempts were aimed at supporting mobility of a single host,
today most of the implementations also support mobile
networks. Mobile IP is the most widely used protocol that
supports mobility of both hosts as well as networks. Mobile IP
defines the presence of mobility agents, i.e. home agent and
foreign agent to support host mobility. In order to support
mobility of a network, the mobile IP protocol suit was
extended and an additional mobility agent i.e. mobile router
was introduced. The performance (quality of service as seen by
the mobile devices) depends upon parameters like handoff
delay, mobility agent efficiency, protocol implementation and
the network conditions. In this project, the authors explore
the features of mobile IP model within OPNET network
simulator. The behavior of the simulated network was compared
with an actual network built in the ANRC Lab at Wichita State
University.
Effect of Storage Mechanism on Storage
Over IP: In today’s global
marketplace, performance, availability, scalability and
reliability of the storage are very critical aspects to
provide uninterrupted and efficient service to the vendors
using the storage. Storage devices can be connected in
different ways and based on the connection, storage is termed
as Direct Attached Storage (DAS), Network Attached Storage
(NAS) and Storage Area Network (SAN). If a storage array or a
SAN consists of several different managed array controllers,
which support hundreds of groups of users with file storage
and volumes of data, it can lead to considerable overhead and
slower speeds of operation. In such a situation, the placement
of the array and the way they are connected plays an important
role in achieving the above goals. In this paper authors
discuss the impact of physical media (FC/IP) connecting the
storage devices over the effective throughput of data and
latency in multiple stages of DAS, NAS, and SAN. The
simulations were run using OPNET network simulator. Initial
simulation results indicate that SAN based storage mechanism
performs better compare to other techniques.
Model and
Analysis of Route Request Process in Ad-hoc Networks for VOIP:
In this
project, we developed a mathematical model for the route
discovery process in ad hoc networks. This model is based on
Markov chains and it takes into account the probability
associated with the route availability as a function of time.
This model is simulated and the performance of various on-demand
routing protocols in terms of route discovery process is
evaluated. This model provides a criteria for selecting an
on-demand routing protocol for voice communication in ad hoc
networks.
Analysis of Denial of Service attack on
VoIP networks:
Voice over
Internet Protocol (VoIP) is an Internet technology which is
revolutionizing the way we communicate these days. The ease of
implementation and significant reduction in costs for long
distance communication makes VoIP the ideal form of
communication for the coming years. Though there have been
significant advances in this field, Security of VoIP network
is still a major concern. This paper gives a brief
introduction to VoIP, and describes the common security
threats and counter measures. Our major emphasis will be on
the impact of DoS attack over VoIP and its effect on voice
quality
Performance Analysis of Voice Traffic
over Ad-hoc Networks:
This paper deals with issues limiting the performance of Voice
traffic in Ad-hoc networks. We observed End-To-End Delay and
Packet Loss while changing number of nodes, running various
traffic types, inducing mobility and varying distances among
the nodes. We extended the idea with adjacent channel
interference. OPNET (v10.0) was used as simulator.
Impact of
Denial of Service Attacks on Voice over Internet
Protocol-bearing Ad Hoc Wireless Networks:
The ad-hoc wireless network’s simple and distributed nature
presents certain vulnerabilities to attack. A significant
class of attacks are the Denial of Service attacks (DoS),
which include radio jamming and sleep deprivation attacks. Our
study focuses on the performance of an ad-hoc wireless network
bearing VoIP traffic under DoS attack.
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