Saturday, 17 January 2015

NS2 BASIC PROGRAM FOR BEGINNERS-1

NS2 BASIC PROGRAM FOR BEGINNERS

FIRST EXAMPLE PROGRAM 

NETWORK SIMULATOR GUIDE 

SUNDARAPRAKASH CREATIONZ click here

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1. To Design C++ and OTcl classes (e.g., Class My TCP). Derive this class from the TCP Reno classes. Use the convention defined above to name the class names, variables/instvars, and functions/instprocs in both the domain.

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# myfirst_ns.tcl
# Create a Simulator
1 set ns [new Simulator]
# Create a trace file
2 set mytrace [open out.tr w]
3 $ns trace-all $mytrace
# Create a NAM trace file
4 set myNAM [open out.nam w]
5 $ns namtrace-all $myNAM
# Define a procedure finish
6 proc finish { } {
7 global ns mytrace myNAM
8 $ns flush-trace
9 close $mytrace
10 close $myNAM
11 exec nam out.nam &
12 exit 0
13 }
# Create Nodes
14 set n0 [$ns node]
15 set n1 [$ns node]
16 set n2 [$ns node]
17 set n3 [$ns node]
18 set n4 [$ns node]
# Connect Nodes with Links
19 $ns duplex-link $n0 $n2 100Mb 5ms DropTail
20 $ns duplex-link $n1 $n2 100Mb 5ms DropTail
21 $ns duplex-link $n2 $n4 54Mb 10ms DropTail
22 $ns duplex-link $n2 $n3 54Mb 10ms DropTail
23 $ns simplex-link $n3 $n4 10Mb 15ms DropTail
24 $ns queue-limit $n2 $n3 40
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Wednesday, 7 January 2015

Basics of Computer Network Simulation

Network Simulator Guide 

SUNDARAPRAKASH CREATIONZ click here

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Basics of  Computer Network Simulation

                        A simulation is, more or less, a combination of art and science. That is, while
the expertise in computer programming and the applied mathematical tools
account for the science part, the very skill in analysis and conceptual model
formulation usually represents the art portion.
                        A long list of steps in executing
a simulation process, as given in [2], seems to reflect this popular claim.
Basically, all these steps can be put into three main tasks each of which carries
different degrees of importance.
                        According to Shannon [2], it is recommended that 40 percent of time and
effort be spent on defining a problem, designing a corresponding model, and
devising a set of experiments to be performed on the simulation model. Further,
it was pointed out that a portion of 20 percent should be used to program
the conceptual elements obtained during the first step.
                        Finally, the remaining
40 percent should be utilized in verifying/validating the simulation model, experimenting
with designed inputs (and possibly fine-tuning the experiments
themeselves), and analyzing the results.  
                       We note that this formula is in no
way a strict one. Any actual simulation may require more or less time and
effort, depending on the context of interest and, definitely, on the modeler
himself/herself.
                     A simulation can be thought of as a flow process of network entities (e.g.,
nodes, packets). As these entities move through the system, they interact with
other entities, join certain activities, trigger events, cause some changes to the
state of the system, and leave the process.
                  From time to time, they contend
or wait for some type of resources. This implies that there must be a logical
execution sequence to cause all these actions to happen in a comprehensible
and manageable way. An execution sequence plays an important role in
supervising a simulation and is sometimes used to characterize the types of
simulation.
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How To Use Network Simulator2

                                Network simulator 2 (NS2)

Introduction to Network

Simulator NS2

ANOTHER GREAT RELEASE FROM   SUNDARAPRAKASH CREATIONZ click here

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        NS2 is an open-source event-driven simulator designed specifically for research
in computer communication networks. Since its inception in 1989, NS2 has
continuously gained tremendous interest from industry, academia, and government.
Having been under constant investigation and enhancement for years,
         NS2 now contains modules for numerous network components such as routing,
transport layer protocol, application, etc. 
          To investigate network performance,
researchers can simply use an easy-to-use scripting language to configure a network,
and observe results generated by NS2. Undoubtedly, NS2 has become
the most widely used open source network simulator, and one of the most
widely used network simulators.
           Unfortunately, most research needs simulation modules which are beyond
the scope of the built-in NS2 modules. Incorporating these modules into NS2
requires profound understanding of NS2 architecture. Currently, most NS2
beginners rely on online tutorials. 
           Most of the available information mainly
explains how to configure a network and collect results, but does not include
sufficient information for building additional modules in NS2. Despite its details
about NS2 modules, the formal documentation of NS2 is mainly written
as a reference book, and does not provide much information for beginners.
           The
lack of guidelines for extending NS2 is perhaps the greatest obstacle, which
discourages numerous researchers from using NS2. At this moment, there is
no guide book which can help the beginners understand the architecture of NS2 depth.
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Secure Data Retrieval for Decentralized Disruption-Tolerant Hi-privacy Networks

Secure Data Retrieval for Decentralized Disruption-Tolerant Hi-privacy Networks          ------------------------------------------------------------------------------------------------------------                                                                      
                 Mobile nodes in military environments such as a
battlefield or a hostile region are likely to suffer from intermittent
network connectivity and frequent part                                                                                                                                       Disruption-tolerant
network (DTN) technologies are becoming successful solutions
that allow wireless devices carried by soldiers to communicate
with each other and access the confidential information or command
reliably by exploiting external storage nodes. 
                                                 Some of the
most challenging issues in this scenario are the enforcement of
authorization policies and the policies update for secure data
retrieval. 
                  Ciphertext-policy attribute-based encryption (CP-ABE)
is a promising cryptographic solution to the access control issues.
However, the problem of applying CP-ABE in decentralized DTNs
introduces several security and privacy challenges with regard to
the attribute revocation, key escrow, and coordination of attributes
issued from different authorities. In this paper, we propose a secure
data retrieval scheme using CP-ABE for decentralized DTNs
where multiple key authorities manage their attributes independently.
We demonstrate how to apply the proposed mechanism to
securely and efficiently manage the confidential data distributed
in the disruption-tolerant Hi-Privacy network.
                                            

Friday, 25 July 2014

Open source technology(ABSTRACT)

 Open source technology
                                 -A.Sundaraprakash
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                                                          ABSTRACT
                                                   
                                    This paper makes an attempt to explain the latest open source technology.  In modern computer world huge companies like the New York Stock Exchange are starting to adopt free open source software. So it is necessary to discuss about the open source technologies.
            Open source's potential for delivering significant savings to the bottom line, resulting from the lack of software license fees. The concept of free sharing of technological information existed long before computers. For example, cooking recipes have been shared since the beginning of human culture.
            Many fields of study and social and political views have been affected by the growth of the concept of open source.
ü  Computer software
ü  Application software
ü  Operating systems
ü  Programming languages
ü  Server software

Open-source software is software whose source code is published and made available to the public, enabling anyone to copy, modify and redistribute the source code without paying royalties or fees. In this paper I discussed drawbacks in open source also. Some drawbacks like,
Reporting of bugs etc.
                       
Anyhow, OSS Economical, and licensed .When an open-source system is used, the operating environment and source code availability provides vast opportunities for teaching, learning, experimentation and Researches. So it is very useful for latest technology development and students….!
                                                            Thank you….!!



Thursday, 24 July 2014

LTE (telecommunication), Long Term Evolution, a telephone and mobile broadband communication standard(4G Technology)

Introduction

LTE, an acronym for Long-Term Evolution, commonly marketed as 4G LTE, is a standard for wireless communication of high-speed data for mobile phones and data terminals. It is based on the GSM/EDGE and UMTS/HSPA network technologies, increasing the capacity and speed using a different radio interface together with core network improvements. The standard is developed by the 3GPP (3rd Generation Partnership Project) and is specified in its Release 8 document series, with minor enhancements described in Release 9.
LTE is a standard for wireless data communications technology and an evolution of the GSM/UMTS standards. The goal of LTE was to increase the capacity and speed of wireless data networks using new DSP (digital signal processing) techniques and modulations that were developed around the turn of the millennium. A further goal was the redesign and simplification of the network architecture to an IP-based system with significantly reduced transfer latency compared to the 3G architecture. The LTE wireless interface is incompatible with 2G and 3G networks, so that it must be operated on a separate wireless spectrum.
LTE was first proposed by NTT DoCoMo of Japan in 2004, and studies on the new standard officially commenced in 2005 In May 2007, the LTE/SAE Trial Initiative (LSTI) alliance was founded as a global collaboration between vendors and operators with the goal of verifying and promoting the new standard in order to ensure the global introduction of the technology as quickly as possible. The LTE standard was finalized in December 2008, and the first publicly available LTE service was launched by TeliaSonera in Oslo and Stockholm on December 14, 2009 as a data connection with a USB modem. The LTE services were launched by major North American carriers as well, with the Samsung SCH-r900 being the world’s first LTE Mobile phone starting on September 21, 2010 and Samsung Galaxy Indulge being the world’s first LTE smartphone starting on February 10, 2011 both offered by MetroPCS and HTC ThunderBolt offered by Verizon starting on March 17 being the second LTE smartphone to be sold commercially. In Canada, Rogers Wireless was the first to launch LTE network on July 7, 2011 offering the Sierra Wireless AirCard® 313U USB mobile broadband modem, known as the "LTE Rocket™ stick" then followed closely by mobile devices from both HTC and Samsung. Initially, CDMA operators planned to upgrade to rival standards called UMB and WiMAX, but all the major CDMA operators (such as VerizonSprint and MetroPCS in the United States, Belland Telus in Canada, au by KDDI in Japan, SK Telecom in South Korea and China Telecom/China Unicom in China) have announced that they intend to migrate to LTE after all. The evolution of LTE is LTE Advanced, which was standardized in March 2011. Services are expected to commence in 2013
The LTE specification provides downlink peak rates of 300 Mbit/s, uplink peak rates of 75 Mbit/s and QoS provisions permitting a transferlatency of less than 5 ms in the radio access network. LTE has the ability to manage fast-moving mobiles and supports multi-cast and broadcast streams. LTE supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz and supports both frequency division duplexing(FDD) and time-division duplexing (TDD). The IP-based network architecture, called the Evolved Packet Core (EPC) and designed to replace the GPRS Core Network, supports seamless handovers for both voice and data to cell towers with older network technology such as GSM, UMTS and CDMA2000. The simpler architecture results in lower operating costs (for example, each E-UTRA cell will support up to four times the data and voice capacity supported by HSPA).

RankCountry/TerritoryPenetration
1 South Korea62.0%
2 Japan21.3%
3 Australia21.1%
4 United States19.0%
5 Sweden14.0%
6 Canada8.0%
7 United Kingdom5.0%
8 Germany3.0%
9 Russia2.0%
10 Philippines1.0%

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Tuesday, 22 July 2014

What is Burst in GSM? and Burst Types in GSM

A.Sundara Prakash's CREATIONZ
GSM Burst
The Below diagram illustrates a GSM burst. It consists of several different elements.
GSM Burst and TDMA Frame
These elements are as below:
Info
This is the area in which the speech, data or control information is held.
Guard Period
The BTS and MS can only receive the burst and decode it, if it is received within the time slot designated for it. The timing, therefore, must be extremely accurate, but the structure does allow for a small margin of error by incorporating a ‘guard period’ as shown in the diagram. To be precise, the time slot is 0.577 ms long, whereas the burst is only 0.546 ms long, therefore there is a time difference of 0.031 ms to enable the burst to hit the time slot.
Stealing Flags
These two bits are set when a traffic channel burst has been ‘‘stolen” by a FACCH (the Fast Associated Control Channel). One bit set indicates that half of the block has been stolen.
Training Sequence
This is used by the receiver’s equalizer as it estimates the transfer characteristic of the physical path between the BTS and the MS. The training sequence is 26 bits long.
Tail Bits
These are used to indicate the beginning and end of the burst.
Burst Types
The diagram below shows the five types of burst employed in the GSM air interface. All bursts, of whatever type, have to be timed so that they are received within the appropriate timeslot of the TDMA frame.
GSM Burst Types
The burst is the sequence of bits transmitted by the BTS or MS, the time slot is the discrete period of real time within which it must arrive in order to be correctly decoded by the receiver:
Normal Burst
The normal burst carries traffic channels and all types of control channels.
Frequency Correction Burst
This burst carries FCCH down link to correct the frequency of the MS’s local oscillator, effectively locking it to that of the BTS.
Synchronization Burst
So called because its function is to carry SCH down link, synchronizing the timing of the MS to that of the BTS.
Dummy Burst
Used when there is no information to be carried on the unused time slots of the BCCH Carrier (down link only).
Access Burst
This burst is of much shorter duration than the other types. The increased guard period is necessary because the timing of its transmission is unknown. When this burst is transmitted, the BTS does not know the location of the MS and therefore the timing of the message from the MS can not be accurately accounted for. (The Access Burst is up-link only.)