Basics of network

network

In general, the term network can refer to any interconnected group or system. More specifically, a network is any method of sharing information between two systems (human, electrical or mechanical).


classification of network

1. According to the size of the Network:
LAN 
MAN 
WAN 
PAN 
CAN
2. According to type of connection used:
Wired Network
Wireless Network
lan(local area network)


Characteristics:
1) A Local Area Network is a group of computers and network 
2) Communication devices within a limited geographic area, such as an office building. For example, a library will have a wired or wireless LAN for users to interconnect local devices(e.g., printers, and servers).
3) Local area networking uses switches, bridges and/or repeaters, and hubs to interconnect LANs and increase overall size. Routers are used to connect a LAN to a WAN or MAN.
4) LAN are characterized by the following:
5) High data transfer speeds.
6) Generally less expensive technologies 
7) Limited geographic area
8) Security 
9) Scalability 
10) Reliability
man(metropolitan area network)

A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area. A MAN can range anywhere from 5 to 50km in diameter.
wan(wide area network)

A WAN is a data communications network that covers a relatively broad geographic area (i.e. one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. They are generally connected with each other using routers.
WAN are characterized by the following:
1) Multiple interconnected LANs. 
2) Generally more expensive technology.
3) More sophisticated to implement than LANs.
4) Exist in an unlimited geographic area.

pan(personal area network)

A personal area network (PAN) is a computer network used for Communication among computer devices close to one person. 
Some examples of devices that may be used in a PAN are printers, fax machines, telephones, scanners. The reach of a PAN is typically within about 20-30 feet (approximately 6-9 Meters).
san(storage area network)

We have a lot of data in the form of audio and video. We need to store data for quick access and transfer on special storage devices.
SAN may be referred to as a sub network or special purpose network. Its special purpose is to allow users on a larger network to connect various data storage devices with clusters of data servers.
vpn(virtual private network)

VPN is a private network that lets you access public networks remotely. 
VPN uses encryption and security protocols to retain privacy while it accesses outside resources by creating a virtual network.
according to the type of connection used

1) Wired Network: A network that connects devices using cables (wires) like Coaxial Cable, Twisted pair Cable, Optical Fiber Cable etc.
2) Wireless Network: A network that connects devices using wireless technologies like Bluetooth, infrared, radio frequency etc.
according to the type of functional group


peer to peer network(workgroup)


A workgroup is a collection of computers on a LAN that share common resources and responsibilities. 
Workgroups provide easy sharing of files, printers and other network resources.
client-server network(domain)


1) A Domain is a "Network Architecture" in which each computer or process on the network is either a client or a server.
2) servers are powerful computers or processes dedicated to managing disk drives (file servers), printers (print servers) etc. 
3) Clients are PCs or workstations on which users run applications.
4) Clients rely on servers for resources, such as files, devices, and even processing power.

Network attacks

NETWORK ATTACKS

attacks on network

Men in middle attack
Attackers position themselves between two systems and actively participate
in the connection to gather data. The attacker may also run program which
spoofs dns reply, configured to send false DNS information so that a DNS query
for a given website will resolve to the attacker's IP address. Then the attacker will
activate a program such that it will transparently proxy all HTTP and HTTPS traffic it receives. The DNS spoof program detects DNS request for www.abc.com and redirects the client to
attacker's machine. The ARP table convinces the victim's machine that it is indeed talking
to the intended web server. The victim's browser starts to establish a secure connection.

All messages for establishing SSL connection are sent to MITM running on the attacker's machine.
Hacker's system acts as a SSL proxy, establishing two SSL connections-one from victim to the attacker's
machine and the other from attacker's machine to the actual web server. When establishing the SSL session
between the victim machine and the attacker machine, MITM program will send the attacker's own certificate. The victim's browser will notice that the certificate is not signed by a trusted Certificate Authority and show
a message to the user asking the user whether to accept this un-trusted certificate or not. The normal tendency is to accept
it, thinking it is some error message.
denial of service(DOS)
A denial of service attack (DOS) is an attack through which a person can render
a system unusable or significantly slow down the system for legitimate users by overloading
the resources, so that no one can access it. If an attacker is unable to gain access to a machine, the attacker most probably will
just crash the machine to accomplish a denial of service attack.

Network Attacks

NETWORK ATTACKS
Attacks on network

Attacking a network means either defacing it to ground or accessing a data which
you should not. In a network there are mainly two types of attacks are possible.
1). Denial of Service (DOS) attack.
2). Data Stealing.
network-infrastructure attacks
Hacker attacks against network infrastructures can be easy, because many
networks can be reached from anywhere in the world via the Internet. Here are some examples of network-infrastructure attacks: Connecting into a network through a rogue modem attached to a computer behind
a firewall Exploiting weaknesses in network transport mechanisms, such as TCP/IP and NetBIOS Flooding a network with too many requests, creating a denial of service (DoS)
for legitimate requests installing a network analyzer on a network and capturing every packet that travels across it, revealing confidential information in clear text.
common network attacks

1) Sniffing Attack.
2) Man in middle attack.
3) DOS attacks.
sniffing attacks

Sniffers monitor network data. A sniffer can be a self-contained software program or a hardware device with
the appropriate software or firmware programming.
Sniffers usually act as network probes or "snoops" examining network traffic but
not intercepting or altering it. Some sniffers work only with TCP/IP packets, but the more sophisticated tools can work with many other protocols and at lower levels such as the Ethernet frame.
concept

A sniffer is a piece of software that captures the traffic on a network. They are available for
several platforms in both commercial and open-source variations. Some of simplest packages use a command line interface and dump captured data to the screen, while sophisticated ones use GUI, graph traffic statistics, track multiple sessions and offer several configuration options.
Sniffers are also the engines for other programs. Network Intrusion Detection Systems (NIDS)
use sniffers to match packets against a rule-set designed to flag anything malicious or strange. Network utilization and monitoring programs often use sniffers to gather data necessary for metrics and analysis. It is to be noted that sniffers do not intercept or alter the data it captures.
The most common way of networking computers is through Ethernet. The Ethernet protocol works by broadcasting packets to all
hosts on the network, with the packet header containing the MAC address of the machine that is meant to receive the packet. All others are supposed to ignore it. A NIC (Network Interface Card, also known as Ethernet card) that is accepting all packets, regardless of the intended machine is said to be in promiscuous mode. A sniffer is a program that sets the desired NIC into promiscuous mode.
note
A packet sniffer is known for its ability to "sniff" plain text passwords. On a normal LAN there are thousands
of packets being conversed by numerous machines every minute. Therefore, anything transmitted in plaintext, such as passwords, web pages, database queries and messaging over the network will be vulnerable to sniffing. man in the middle

Database concepts

DATABASE CONCEPTS

DBMS(DATABASE MANAGEMENT SYSTEM)

DBMS contains information about a particular enterprise
Collection of interrelated data
Set of programs to access the data
An environment that is both convenient and efficient to use
Database Applications:
Banking: all transactions
Airlines: reservations, schedules
Universities: registration, grades
Sales: customers, products, purchases
Online retailers: order tracking, customized recommendations
Manufacturing: production, inventory, orders, supply chain
Human resources: employee records, salaries, tax deductions
Databases touch all aspects of our lives

Purpose of Database Systems
In the early days, database applications were built directly on top of file systems
Drawbacks of using file systems to store data:
Data redundancy and inconsistency
Multiple file formats, duplication of information in different files
Difficulty in accessing data
Need to write a new program to carry out each new task
Data isolation multiple files and formats
Integrity problems
Integrity constraints (e.g. account balance > 0) become buried in program code rather than being stated explicitly
Hard to add new constraints or change existing ones

Drawbacks of using file system
Atomicity of updates
Failures may leave database in an inconsistent state with partial updates carried out
Example: Transfer of funds from one account to another should either complete or not happen at all
Concurrent access by multiple users Concurrent accessed needed for performance
Uncontrolled concurrent accesses can lead to inconsistencies
Example: Two people reading a balance and updating it at the same time
Security problems
Hard to provide user access to some, but not all, data
Database systems offer solutions to all the above problems

Levels of Abstraction

Physical level: describes how a record (e.g., customer) is stored.

Logical level: describes data stored in database, and the relationships among the data.
type customer = record
customer_id : string; customer_name : string; customer_street : string; customer_city : string;
end; View level: application programs hide details of data types.
Views can also hide information (such as an employees salary) for security purposes.
DBMS(DATABASE MANAGEMENT SYSTEM)

An architecture for a database system

configuring apache server

Configuring of Apache server

Listed below is information on how to configure the Apache web server to run PHP programs on Windows machines.
For information on installing and configuring Apache for Windows, please see the following:
Installing and Configuring Apache for Windows

1. Install PHP
PHP needs to be downloaded and installed before continuing. You can download PHP
from the PHP download page at http://www.php.net/downloads.php. Download the zip package from the "Windows Binaries" section. This guide will assume the PHP version is version 5.x.
Create a folder on your machine for PHP. For example, c:\php. Extract all
of the files from the zip file to the c:\php directory.
Copy the file called c:\php\php.ini-recommended to c:\php\php.ini
If you want to be able to see error messages from your PHP pages,
open EditRocket and open the php.ini file. Search for the line display_errors,
and make sure the value is set to On.

2. Configure Apache to run PHP as a Module
This guide assumes you are using apache 2.2. To configure Apache to run PHP
, the httpd.conf file needs to be modified. This file is located in the apache installation directory under the conf folder. Open the httpd.conf file in EditRocket and do the following:
A. Add the following line after all of the LoadModule statements:
LoadModule php5_module "c:/php/php5apache2_2.dll"
B. Search for AddType, and add the following after the last AddType line:
AddType application/x-httpd-php .php
C. Add the PHP location to the end of the httpd.conf file.
For example, at the end of the file, add the following: PHPIniDir "c:/php"

3. Restart Apache Now, the apache web server needs to be restarted.
You can do this either via the Apache service located in the services control
panel or via the Start -> All Programs -> Apache . . . -> Control Apache Server menu option. 4. Run a test PHP page You can use the EditRocket hello world PHP template
for a test PHP page. This is located in File -> New From Template ->php ->Hello_World_Program.
Save this file as test.php to your htdocs folder under your apache installation directory. Open your web browser and type in your apache host (and :port if the port is something other than 80) followed by test.php, for example http://localhost/test.php
If u are using xampp server than put all your php files in htdocs folde

microsoft launcing sql2012

Microsoft SQL Server 2012 Promises Big Data, Business Intelligence Solutions

  

Microsoft has officially launched the release to manufacturing (RTM) version of SQL Server 2012 with a virtual conference and free downloads. SQL Server 2012 is heavily focused around three key themes and the company is positioning it as one of the most significant updates to the platform to date.

Launching SQL Server 2012 Toward Big Data and the Cloud

Yesterday, Microsoft held a virtual conference to announce the RTM release of SQL Server 2012. I have to admit the event was impressive. The 27 launch event sessions are categorized in three tracks that aligned with the official product strategy (I'm providing a marketing translation in parenthesis): mission critical confidence (high availability and reliability topics), breakthrough insights (self-service analytics) and cloud on your terms (Azure and hybrid cloud improvements).

The videos are high quality and more importantly, short, at around 20 minutes per topic. There is also an expo hall, which includes your typical vendor dog and pony shows, and a networking lounge organized in topic areas that enables social networking with other attendees and Microsoft folks.

All that’s missing is free t-shirts and stickers; wait, that’s available too — kind of. The event has a gamefication style point system that awards points, badges and levels for completing activities like viewing sessions, tweeting and interacting in the forums. There are sweepstakes drawings every four hours for prizes like gift cards, headphones and an Xbox 360. 

Beyond the flashy launch event, there is the actual software, which Microsoft Corporate Vice President, Business Platform Division, Ted Kummert says is one of the biggest releases for SQL Server to date. Microsoft’s vision for SQL Server 2012 centers around three areas:

Interestingly, Kummert did not include the new high-availability and reliability features like AlwaysOn, which the company is clearly making a big investment in and may make the product more attractive to larger enterprises with more stringent performance and availability requirements.

The big data features in SQL Server 2012 may be the area that’s generating the most conversation: they’ve even published an infographic. The company is offering new storage options and providing tools that help with big data analysis.

The 2012 version will include an in-memory column oriented database to improve analytics performance, and as we previously reported, Microsoft is also developing a Windows-based version of Hadoop with Yahoo spinoff Hortonworks.  Last October, the company introduced a preview Hadoop service on Azure. The preview is being expanded to 2,000 users, from 400, for the 2012 release. A full release of the service is planned for the end of June.

Microsoft is also continuing its self-service business intelligence (BI) trend in 2012 that makes analytics more accessible to end users and integrates the capability into office products. I admit, self-service BI always sends a cold chill through my spine. Perhaps it’s arrogant of me, but I just don’t think most users should be allowed to run wild through fields of complex data and be left to draw their own conclusions. Although it seems convenient, I’ve seen it yield amazingly inconsistent results and create spreadsheet marts that companies have to spend countless hours and dollars correcting.

iphoto on ipad

When Apple announced iPhoto for iOS at the press event for the new iPad, the company chose not to make the app compatible for the first generation device, leaving many customers out in the cold.

It is of course true that many original iPad owners may be looking to upgrade this year, but for those are still happy with their two-year-old devices, there is light at the end of the tunnel, with a relatively simple little hack allowing iPhoto to be installed on their devices. As is always the case though, there is a downside to proceedings.

For those that just want to forge ahead regardless, here’s what you’ll need to do…

1. First off, download iPhoto for iOS through iTunes on your computer. You’ll need the file there later, and you obviously cannot download it directly to the iPad.
2. You’ll also need to download Apple’s iPhone Configuration Utility too, which is free. Install it, you’ll be using it shortly.
3. Next, plug your iPad into the computer and sync it with iTunes. Once everything is finished, keep the iPad connected and fire up the iPhone Configuration Utility.
4. Select the “Applications” section in the left hand pane and then click “Add” in the top bar. This will allow us to add the iPhoto app that you downloaded earlier. Find the app, and add it. If you’re a Mac user, then it will be in “Music/iTunes/Mobile Applications.”
5. Now, choose your iPad – again, in the left hand pane – then select the “Applications” tab.
6. Finally, scroll through your apps until you find iPhoto, and then click “Install.” Once done, you’ll find iPhoto on your first generation iPad.

Now to the downside. From here on in, syncing your iPad using the traditional iTunes method will remove iPhoto because it is technically unsupported. Whether that is an issue for you depends on how you use your devices, and whether iPhoto is a must-have app for you or not.

Android

In 2002, shortly after the first iPod was released, Jobs started thinking about developing a phone. He saw millions of Americans lugging separate phones, BlackBerrys, and — now — MP3 players; naturally, consumers would prefer just one device. He also saw a future in which cell phones and mobile email devices would amass ever more features, eventually challenging the iPod's dominance as a music player. To protect his new product line, Jobs knew he would eventually need to venture into the wireless world.

If the idea was obvious, so were the obstacles. Data networks were sluggish and not ready for a full-blown handheld Internet device. An iPhone would require Apple to create a completely new operating system; the iPod's OS wasn't sophisticated enough to manage complicated networking or graphics, and even a scaled-down version of OS X would be too much for a cell phone chip to handle. Apple would be facing strong competition, too: In 2003, consumers had flocked to the Palm Treo 600, which merged a phone, PDA, and BlackBerry into one slick package. That proved there was demand for a so-called convergence device, but it also raised the bar for Apple's engineers.

Then there were the wireless carriers. Jobs knew they dictated what to build and how to build it, and that they treated the hardware as little more than a vehicle to get users onto their networks. Jobs, a notorious control freak himself, wasn't about to let a group of suits — whom he would later call "orifices" — tell him how to design his phone.

By 2004 Apple's iPod business had become more important, and more vulnerable, than ever. The iPod accounted for 16 percent of company revenue, but with 3G phones gaining popularity, Wi-Fi phones coming soon, the price of storage plummeting, and rival music stores proliferating, its long-term position as the dominant music device seemed at risk.

So that summer, while he publicly denied he would build an Apple phone, Jobs was working on his entry into the mobile phone industry. In an effort to bypass the carriers, he approached Motorola. It seemed like an easy fix: The handset maker had released the wildly popular RAZR, and Jobs knew Ed Zander, Motorola's CEO at the time, from Zander's days as an executive at Sun Microsystems. A deal would allow Apple to concentrate on developing the music software, while Motorola and the carrier, Cingular, could hash out the complicated hardware details.

Of course, Jobs' plan assumed that Motorola would produce a successor worthy of the RAZR, but it soon became clear that wasn't going to happen. The three companies dickered over pretty much everything — how songs would get into the phone, how much music could be stored there, even how each company's name would be displayed. And when the first prototypes showed up at the end of 2004, there was another problem: The gadget itself was ugly.

Googles product

The crowning achievement of Google’s budding social network by far is the ability to communicate with up to nine other people across the world instantly, and for free. Since the arrival of Hangouts,Google+ users have done everything from communicate casually to conduct trans-continental business meetings. There’s no limit to what those nine people can do, or how long they can do it. To make things even better, users can even enter a Hangout from an Android or iOS device, be that a tablet or a phone.

If you are an active Google+ user, you may consider how well your next device performs in a Hangout as a tie breaker when choosing your next gadget. Over the last week, we’ve gathered the top devices across manufacturers, operating systems, and mobile networks and put them all to the test. So, what is the best phone or tablet for a Google+ Hangout?

NEON VS Non-NEON

On paper, most of the hardware required for a Hangout is the same across most of the smartphones capable of joining the Hangout. For the most part, you’d think that the better camera, or the higher quality microphone setup would be the qualities you would look for in terms of what would be best for a Hangout. At the core, what you are really looking for is a chipset that supports hardware acceleration, specifically for video. This architecture type is called NEON. A device with NEON architecture enhances video encoding or decoding, graphics in things like games, and image/speech processing. NEON devices will handle Hangouts much better than non-NEON devices.

If you have an iPhone 4 or iPhone 4S, your device supports the NEON architecture. For Android devices, you’ll need to do some checking to see if it is supported. Using either a file manager on your device, locate a file called /proc/cpuinfo and open it. If you are unable to access this file from your phone, you can download the Android SDK and access the file using the Android Debug Bridge. If you see the word neon on the Features line, then your device supports NEON extensions.

Phones

To measure which device performed the best overall in a Hangout, each device was put through a series of tests. Each device was tested indoors and outdoors in a variety of situations including wind, conversations happening in the background, multiple people addressing the Hangout, and alone in a quiet room. Conversations in the Hangout were also measured for quality consistency. Each of the devices were tested individually, and each of them were tested in as similar a fashion as possible.

This test yielded several interesting results. HTC and Samsung devices of the same generation performed almost identically, with a single exception. The results from the Samsung Galaxy Nexusin a Hangout were wildly varied. In some tests, the results would be great, while in practically identical situations the Galaxy Nexus was nearly unusable. Motorola’s two most recent devices, the Droid 4 and the Droid Razr, also showed a significant variety in results. Despite being the newest in their lineup, the Droid 4 was by far one of the worst performing devices in every situation.

When comparing the iPhone to the Android batch, the iPhone 4S performed well above most of the Android devices, but struggled with noise cancellation in most situations. If there was wind or other people talking, the phone was often unable to handle the distortion and the audio would suffer. The phone that performed best out of the devices tested was the Samsung Galaxy Note. The high resolution of the screen allowed for a very clear and very large image of the other users in the Hangout, while the microphone placements on the device allowed for sound cancellation and external noise suppression.

smartphone

Smartphone manufacturers seem to be obsessed with making their handsets ever thinner and bragging about it in the form of marketing, only to be beaten the following week/month by a competitor. Now it looks as though the thin-frenzy is migrating over to the tablet market, too.

Toshiba has used the Mobile World Congress this week to unveil the 10.1-inch Excite X10 LE tablet. It stands out from the crowd because Toshiba claims it is the world’s thinnest and lightest tablet.

It’s a fair claim as the X10 LE measures just 7.7mm thick and weighs 535 grams. Compare that to the iPad 2, which is 8.8mm thick and 601 grams. That’s a whole 1.1mm thinner than Apple could achieve, and only 0.6mm thicker than the Droid Razr. Impressive.

Just because it’s super-thin doesn’t mean the X10 skimps on features. Although the use of Android 3.2 is a bit disappointing, Toshiba promise it will get Ice Cream Sandwich before spring is over. Inside you’ll find an OMAP 4430 dual-core Cortex-A9 chip running at 1.2GHz, 1GB RAM, 5MP rear camera, 1.3MP front camera, and the tablet comes in 16GB and 32GB configurations. As for the display, it’s a 10.1-inch panel with a 1280 x 800 resolution.

The Excite X10 LE will officially go on sale March 6. The 16GB unit will set you back $529.99, while the 32GB unit takes that up to $599. It’s therefore $30 more expensive than the iPad 2 16GB, but manages to match the 32GB on price.

March 6 isn’t the best date to launch seeing as we have the small issue of an Apple event the following day. Toshiba may hold the world’s thinnest crown for exactly 24 hours depending on what Apple have achieved with the iPad 3.