Types of networks

Personal Area Network

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 are used in a PAN are printers, fax machines, telephones, PDAs or scanners. The reach of a PAN is typically within about 20-30 feet (approximately 6-9 metres). Personal area networks may be wired with computer buses such as USB[3] and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA and Bluetooth.

Local Area Network (LAN)

Local Area Network A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library will have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet. All of the PCs in the library are connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnection devices and eventually connect to the internet. The cables to the servers are on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbit/s. The staff computers (bright green in the figure) can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup. Typical library network, in a branching tree topology and controlled access to resources All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers. The defining characteristics of LANs, in contrast to WANs (wide area networks), include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 100 Gbit/s, and possibly 40 Gbit/s.

3G

3G technologies enable network operators to offer users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency. Services include wide-area wireless voice telephony and broadband wireless data, all in a mobile environment. Typically, they provide service at 5-10 Mb per second. Unlike IEEE 802.11 networks, 3G networks are wide area cellular telephone networks which evolved to incorporate high-speed internet access and video telephony. IEEE 802.11 (common names Wi-Fi or WLAN) networks are short range, high-bandwidth networks primarily developed for data. In December 2007, 190 3G networks were operating in 40 countries and 154 HSDPA networks were operating in 71 countries, according to the Global mobile Suppliers Association. In Asia, Europe, Canada and the USA, telecommunication companies use W-CDMA technology with the support of around 100 terminal designs to operate 3G mobile networks. In Europe, 3G services were introduced starting in March 2003 in the UK and Italy. The European Union Council suggested that the 3G operators should cover 80% of the European national populations by the end of 2005. Roll-out of 3G networks was delayed in some countries by the enormous costs of additional spectrum licensing fees. See Telecoms crash. In many countries, 3G networks do not use the same radio frequencies as 2G, so mobile operators must build entirely new networks and license entirely new frequencies; an exception is the United States where carriers operate 3G service in the same frequencies as other services. The license fees in some European countries were particularly high, bolstered by government auctions of a limited number of licenses and sealed bid auctions, and initial excitement over 3G's potential. Other delays were due to the expenses of upgrading equipment for the new systems. By June 2007 the 200 millionth 3G subscriber had been connected. Out of 3 billion mobile phone subscriptions worldwide this is only 6.7%. In the countries where 3G was launched first - Japan and South Korea over half of all subscribers use 3G. In Europe the leading country is Italy with a third of its subscribers migrated to 3G. Other leading countries by 3G migration include UK, Austria and Singapore at the 20% migration level. A confusing statistic is counting CDMA 2000 1x RTT customers as if they were 3G customers. If using this oft-disputed definition, then the total 3G subscriber base would be 475 million at June 2007 and 15.8% of all subscribers worldwide.

Mesothelioma is rare form of cancer caused by asbestos exposure. The disease might have been preventable had the asbestos industry acted responsibly decades ago to protect the public from the dangers of asbestos. Unfortunately for the estimated 3,000 Americans diagnosed with mesothelioma each year, the asbestos industry hid the dangers of asbestos from the public for decades after it knew of the risks.
In these pages you will learn about the asbestos tragedy in the United States and how it has affected the lives and health of countless American workers and their families. You will also read about how people are exposed to asbestos, including the types of work sites where asbestos was once common and the trades that worked with and around asbestos-containing products. And you will learn how Baron & Budd was one of the first law firms in the country to fight for the rights of asbestos victims and is still widely recognized as a national leader in asbestos litigation to this day.
For nearly three decades, in courtrooms across the country, Baron & Budd has championed the rights of mesothelioma victims. Here are just a few examples of some of the results we have achieved for our mesothelioma clients:
The cases described here reflect the net amounts of the judgments or settlements our clients received after the deduction of attorneys fees and expenses-in other words, what our clients actually received. The actual settlement or verdict would be higher. These cases were all handled by Baron & Budd attorneys serving as lead counsel.

What is Mesothelioma?

Mesothelioma is a rare form of cancer that invades mesothelial cells. These are specialized cells that make up the membranes lining the chest, the stomach or abdomen, and the heart. Mesothelial cells form a tissue called mesothelium, producing a lubricating fluid that allows the organs to move without irritating nerves.
Asbestos exposure can cause mesothelioma. If you have mesothelioma, you may have come into contact with asbestos on the job or through a secondhand exposure such as asbestos brought into the home on your spouse’s shoes or clothing. See Asbestos Exposure and Mesothelioma for more details. Some researchers believe that the virus SV40 may also be a factor in the development of mesothelioma.

Cigarette–smoking increases your chances of contracting lung cancer or an asbestos–related disease such as asbestosis, although it does not cause mesothelioma. If you have been exposed to asbestos and smoke cigarettes, you should consider quitting. Your local American Cancer Society and the Centers for Disease Control can provide resources, tips, and support for giving up the habit.

Search engine optimization

Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via "natural" ("organic" or "algorithmic") search results for targeted keywords. Usually, the earlier a site is presented in the search results, or the higher it "ranks", the more searchers will visit that site. SEO can also target different kinds of search, including image search, local search, and industry-specific vertical search engines.
As a marketing strategy for increasing a site's relevance, SEO considers how search algorithms work and what people search for. SEO efforts may involve a site's coding, presentation, and structure, as well as fixing problems that could prevent search engine indexing programs from fully spidering a site. Other, more noticeable efforts may include adding unique content to a site, ensuring that content is easily indexed by search engine robots, and making the site more appealing to users. Another class of techniques, known as black hat SEO or spamdexing, use methods such as link farms and keyword stuffing that tend to harm search engine user experience. Search engines look for sites that employ these techniques and may remove them from their indexes.

There is clear and widespread agreement among the public and educators that all students need to be proficient computer users or "computer literate." However, while districts are spending a great deal of money on technology, there seems to be only a vague notion of what computer literacy really means. Can the student who operates a computer well enough to play a game, send e-mail or surf the Web be considered computer literate? Will a student who uses computers in school only for running tutorials or an integrated learning system have the skills necessary to survive in our society?
Will the ability to do basic word processing be sufficient for students entering the workplace or post-secondary education?
Clearly not. In too many schools, teachers and students still use computers only as the equivalent of expensive flash cards, electronic worksheets, or as little more than a typewriter. The productivity side of computer use in the general content area curriculum is neglected or grossly underdeveloped.