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The mysterious world of wireless technology

Wireless cellular technology has made the cellular phone a must have accessory that enables us to instantly communicate with friends, relatives, and business associates. Similarly, computers can also be free of wired connections when they are part of a wireless local area network (WLAN). Wireless networks are very popular in home and business computer environments and are great in places that are not conductive to running cable, such as outdoor centers, convention centers, bookstores, coffee shops, universities and hotels. Laptops are frequently used to connect to a wireless network. In wireless network technology the data is transmitted over air using either infrared or radio frequencies. The transmitted waves can be described in terms of a sine wave. A number of wireless technologies are in use globally, most of which are not compatible with the others. Wireless networks have evolved from analog-based equipment to sophisticated digital devices. As wireless technologies improved, they were categorized into generations, using a number and the letter G. For example, first generation technology is labeled 1G, second generation 2G, and so on.

IEEE Wireless LAN Specification

The IEEE (Institute for Electrical and Electronics Engineers) committee created a wireless network standard called 802.11 wireless standards. There are five 802.11 standards: 802.11, 802.11a, 802.11b, 802.11g, and 802.11e, 802.11n. 802.11e differs from the others in that it focuses on providing for quality of service (QoS) in wireless LAN. The 802.11 specification identifies an over-the-air interface between a wireless client and a base station or between two mobile device wireless clients. This kind of wireless network also known as Wi-Fi. Wireless networks operate at layer 1 and 2 of the OSI model. The IEEE 802.11 standard specifies parameters of both the physical (PHY) and data link layer (MAC) layers of the networks.

PHYSICAL Layer : This layer is responsible for the transmission of information among nodes. The wireless standards supports data rates ranging from 2 Mbps to 54 Mbps, with the early draft of a proposed new standard, 802.11n, target 100 Mbps.

DATA LINK (MAC) Layer: This layer is a set of protocols responsible for maintaining order in the use of a shared medium. The 802.11 standard specifies a carrier sense multiple access with collision avoidance (CSMA/CA) protocol for the wireless LANs. This layer provides services like Data transfer, association, re-association, authentication and privacy.

CSMA/CA (Carrie Sense Multiple Access with Collision Avoidance) : This technology is used with wireless networks (WLANs) and Apple networks; with CSMA/CA a workstation that wants to transmit data sends a jam signal onto medium. The workstation then waits a small amount of time for all other workstations to hear the jam signal and then the workstation begins transmission. If a collision occurs the workstation stops transmission, waits a designated amount of time and then retransmits.

Types of Wireless Networks

802.11 standards offer two operational modes: ad hoc and infrastructure. Ad hoc mode : An ad hoc mode wireless network refers to peer-to-peer or IBSS (Independent Basic Service Set). It does not have backbone infrastructure and involve at least two wireless workstations these both should have wireless cards. Two devices transmit and receive data. There are three major types of wireless NICs; PC Card, USB, and PCI. Ad mod wireless network is used when two or more computers need to transfer data, or one computer connects to internet and other computer(s) not wired into same network.

Infrastructure mode: This wireless network mode connects multiple wireless network devices through an access point. An access point is a device that receives and transmits data from multiple computers that have wireless cards. The easiest way to describe an access point is to think of it as a network hub, it connects the wireless network. The access point can also be wired to another wireless network or a wired network. When multiple devices connect to an access point, the configuration is known as BSS (Basic Service Set). When multiple access points connect to same main network (known to some as distribution system), the network design is known as ESS (Extended Service Set). Each access point is assigned an SSID (Service Set Identifier). An SSID is a set of 32 alphanumeric characters used to differentiate between different wireless networks. If two access points connect to same wireless network, the same SSID is used. An access point can be configured with a password and channel ID. The channel ID defines at what frequency the access point operates. With the 802.11b standard, up to 14 channels are available. The three commonly used non-overlapping channel IDs are 1, 6, and 11. By using these three channel IDs, the three access points would not interfere with one another. This is because each center frequency overlaps with the adjacent frequency channels.

ANTENNA: Wireless cards and access points can have either antennas or antennas built into them. An antenna is used to radiate or receive radio waves. Some laptops have the wireless antenna built into the laptop screen. The quality of these integrated antennas is diverse. There are two major types of antennas: Omni-directional and directional. An Omni-directional antenna radiates in all directions. A directional antenna radiates energy in specific direction.

What is WIMAX?

Wimax means World wide Interoperability for Microwave Access. It is telecommunication technology aimed at wireless connectivity over long distances. It is almost similar to wireless standard known as Wi-Fi, but on a larger scale and at high speed. Wimax networks are based on IEEE 802.16 standers. Wimax performance is similar to wired networks like cable, DSL with high data rate of 70MBPS or more. A single Wimax antenna has range up to 40miles there fore Wimax network is also known as Wireless MAN (Metropolitan Area Network).

Author : Rizwan Siddiqi

Importance of Network Security

It seems that every other day there is story in news about a computer network compromised by hackers. More recently, Yahoo, Amazon, eBay and some other popular World Wide Web (WWW) sites were targeted by hackers with much known “Denial of Service” attack. During three days sites were overwhelmed by massive bombardment of false traffic from multiple sites. As a result sites were shutdown for hours at a time. Few days ago a theft of billion of dollars by hackers from Citibank also reported. Similarly some of the attackers are found compromising legitimate websites and using them to host malicious code such as Trojans and password stealers. Unfortunately users visiting these websites will find themselves victims of “drive-by downloads” whereby computers are silently infected with malware. These types of attacks illustrate how alarming the threat from outside hackers has become.

The need of network security is relatively new requirement. Prior to 1980 most computers were not networked. It was not due to lack of desire to network them; it was more due to result of lack of technology. In 1980s the combination of the development of personal computer (PC), the development of network protocol standards, and the development of new applications made networking much more accepted practice. As a result LANs, WANs, distributed computing experienced tremendous growth during that period.   

Development of packet switched protocols such as X.25 and TCP/IP allowed many systems to share circuits. Many people or organizations could be interconnected over the shared network. Vulnerabilities were introduced with the deployment of this distributed environment utilizing shared, packet switched networks employing protocols such as TCP/IP and the concept of trusted systems.

 Importance of Computer and Network Security

Network and computer security is critical to financial health of every company. Almost every day a new network security incident reported. One recent report stated that hacking and viruses will cost companies approximately $1.6 trillion world wide.

At the same time, every organization that uses computers faces the threat of hacking from individuals within the organization. Employees or former employees with malicious intent or who want to obtain information such as employee salaries or view other employee’s files are also a threat to an organization’s computers and networks. Every organization should monitor its systems for possible unauthorized intrusion and other attacks. Network security should be part of daily routine of a company IT department.

There is a question to ask “why is Computer and Network Security important?” Computer and network security is important for the following reasons.

To protect company assets: The most important and vital asset for an organization is its “Information”. 

To gain a competitive advantage: It provides competitive advantage to a company over its competition, particularly in banking and e-commerce sector where financial transaction should be made within a secure channel.

To comply with regularity requirements and fiduciary responsibilities: Continuity of operations is necessary in an organization it will be possible only when computers and data are safe enough to not compromised by some hacking attacks and remain in working condition. Other wise the trust of the organization will be damage.

There are three key principles of information security in an organization known as (C-I-A).

Confidentiality is concerned with preventing the unauthorized disclosure of sensitive information.

Prevention of the modification of information by unauthorized users and prevention of the unauthorized or unintentional modification of information by authorized users.

Availability assures that a system’s authorized users have timely and uninterrupted access to the information in the system and to the network.

 Author:   Rizwan Siddiq

Tags: Hacking awareness, Network Security

PTA blocks Facebook, Youtube, WikiPedia

The govt. of Pakistan blocked facebook on Wednesday after a group of lawyers in Lahore won a court order requiring officials to block the popular social network website facebook until 31 May. The reason of this act is a group on facebook that annouced to celebrate "EVERYBODY DRAW MOHAMMAD DAY " on 20th May, it encourages users to post images of prophet Mohammad(PBUH).

Facebook reported wednesday that they are investigating this issue, and the contents does not voilate our terms and condition, we do not understand it could not be legal in some countries. In that case the approach can be followed to restrict certain contents from being shown in specific countries.

Online reaction of people on facebook ban was very supportive on wednesday, but after the time passing and on thursday after the restriction of youtube, wikipedia, and flicker many internet users showed their anger on this wide range restrictions.

Now the question is ban on youtube, wikipedia and flicker is temporary till 31 May or permanant. Because PTA did not give any deadline about the restrictions of these sites. In history of Pakistan you tube was blocked in 2008 for two days in all over Paksitan. Lets see how much time this ban will take. The PTA did not point to specific material on you tube that prompted it to block the site, only citing "growing sacriligious contents"

It remains to seen that how much govt. of Pakistan will be succeeded at keeping Pakistan's nearly 20 million internet users from accessing the blocked sites. Indonesia, Turkry, Thailand, Morroco also blocked you tube in past for various reasons. China permanantly blocked the facebook and youtube. But people can still have access to these blocked websites through various proxy servers. Therefore its not a permanant solution.  

On Twitter which is still unblocked peopel showed their reactions on restrictions of these websites. A person tweets "You can tell that Facebook's blocked, when a guy standing outside a restaurant hands you an event invitation on a piece of paper!! "

A person from a foreign country tweets " Pakistan just blocked youtube and facebook across the country. Pray for them, and thank God we live in a free country."

"Sad and embarrassing day in the history of Pakistan. Tough times to be a Pakistani. Questionable decisions in a so called 'democracy,"' one user tweeted

Tags: websites blocked, General

IT as a Profession

Tags: Motivation, General

Event calender based on Jquery and XML

here is simple event based calender which drag events from xml file  here is source file

DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">