Networks

=__Networks__= http://computer.howstuffworks. com/internet/basics/internet- infrastructure.htm

**Read and Review the Components of Networks at the links below:** [|Network tutorial] [|Review the Parts of a Network for the Case Study and General Computer IT Knowledge]

Main function of network:
It allows you for :
 * 1) Internet Access
 * 2) Shared Data Access
 * 3) Communication

Types:
__**WAN**__-Wide Area Network is a computer network that covers a broad area. __**LAN**__-Local Area Network is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. __**VPN**__-Virtual Private Network is a computer network that appears to be a dedicated network to a particular set of users, whilst in fact using the infrastructure of public switched networks. Uses encryption to protect data. __**P2P**__-Peer-to-Peer is any distributed network architecture composed of participants that make a portion of their resources (such as processing power, disk storage or network bandwidth) directly available to other network participants. __**MAN**__-Metropolitan Area Network is a large computer network that usually spans a city or a large campus. __**PAN**__-Personal Area Network is a computer network used for communication among computer devices, including telephones and personal digital assistants, in proximity to an individual's body. __**SAN**__-Storage Area Network is an architecture to attach remote computer storage devices (such as disk arrays, tape libraries, and optical jukeboxes) to servers in such a way that the devices appear as locally attached to the operating system.

Components:
**__ Parts of a network- __** -**computer** - a machine for performing calculations automatically -**printers** - an output device that prints the results of data processing -**ethernet cable/wifi(and router)** - A method used to connect computers, hubs, switches, routers, etc. to a network. They resemble a large phone cable, or they transmit the signal from one device to the other wirelessly. -**modem** - a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. -**isp** - Companies which provide telecommunications services over fixed or mobile networks, or services with a telecommunication service component, to the public at large but do not own or operate telecommunications networks. -**bandwidth** - a data transmission rate; the maximum amount of information (bits/second) that can be transmitted along a channel -**network backbone** - A backbone network or network backbone is a part of computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks. **-database** - a comprehensive collection of related data organized for convenient access **-hub -** a center of activity or interest or commerce or transportation; a focal point around which events revolve/ A hardware device providing the interconnection between networked devices. It is called a hub because the network wiring can be sketched like a spoked wheel with the hub at the center. A Network Hub is used with 10-Base T and 100-Base T EtherNet wiring. **-dedicated server -** a type of Internet hosting in which the client leases an entire server not shared with anyone.
 * dedicated server types** = mail, web, applications, ftp, file transfer, proxy.
 * -switch -** a computer networking device that connects network segments

What is used to connect the server(s) to the computers on the network?
 The general idea behind both T1 and T5 lines is to provide high-speed and reliable Internet access T1 lines use a special type of telephone to transfer data with the service provider. The telephones lines are made out of twisted copper or with bundled glass fibers, which are more commonly known as fiber optics. T5 lines use coaxial cables to transfer data, a type of electrical cable first developed to be a part of AT&T's L-carrier system. The technology was later upgraded to be used with T5 lines.
 * Determine whether you will connect to the server via a directly linked cable or through a wireless network router. If connecting through a wireless system, you will need to configure the workstation to communicate with the wireless router.
 * Turn the workstation off.
 * Connect the network cable to the port on the at one end and the desired server at the other end. If working in an office, a jack should be located in the wall to connect the cable with the server.
 * Select the file folders, programs and peripherals connected to the server you wish to share. If the computer joins an existing network, skip this step and go to the next step.
 * Add a new user to the server. Go to the program responsible for keeping track of all users on the network and follow the process for adding a new user. You will need to add a username, password and perhaps a computer name, depending on the network. Write down the username, password and computer name.
 * Power up the computer.
 * Allow the operating system to recognize the new connection.
 * Use the help of a network setup wizard in Windows to connect the computer to the server. On a Mac, use the Network Setup Assistant to take you through the process. Provide the username, password and computer name for the computer and domain name (name of the network) when prompted.
 * Restart the workstation when prompted to do so to allow the computer to solidify the new connection to the server.
 * Check the status of the network connection to make sure the computer has successfully connected to the server.
 * DIFFERENCE BETWEEN __TRANSMISSION LINE 1 and 5__**

T1 lines were first made by AT&T Bell Labs for Japan and the United States. As of 2010, thousands of companies lease T1 lines across the United States. Even though the technology behind T5 lines existed even in the 1980s, most of its features are still in various stages of development. Therefore, it is rare to find a telecommunications company providing T5 lines.

T1 lines are a fast and reliable way to transfer data, because they are not affected by factors such as distance from the service provider, weather conditions and fluctuations in network traffic. However, the reliability of T5 lines is largely unknown because the technology is not widely used. T5 lines when fully developed will most likely be available to large companies, mainly due to the high costs that are sure to be associated when purchasing them. T5 - More robust than a T1-T3 - faster, more data transmitted.

.ip is a pseudo-top-level domain which is used to indicate that the rest of the hostname is either an IP address or a masked IP address. The IRC server UnrealIRCD is one of the users of this pseudo-top-level domain. A T1 line can carry about 192,000 bytes per second -- roughly 60 times more data than a normal residential modem. It is also extremely reliable -- much more reliable than an analog modem. Depending on what they are doing, a T1 line can generally handle quite a few people. For general browsing, hundreds of users are easily able to share a T1 line comfortably. If they are all downloading MP3 files or video files simultaneously it would be a problem, but that still isn't extremely common. A T1 line might cost between $1,000 and $1,500 per month depending on who provides it and where it goes. The other end of the T1 line needs to be connected to a web server, and the total cost is a combination of the fee the phone company charges and the fee the ISP charges.
 * IP**

VOIP
 * Voice over Internet Protocol** (**Voice over IP**, **VoIP**) is one of a family of internet technologies, communication protocols, and transmission technologies for delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms frequently encountered and often used synonymously with VoIP are //IP telephony//, //Internet telephony//, //voice over broadband// (VoBB), //broadband telephony//, and //broadband phone//.

Data Sharing - Reliability & Consistency
A [|transaction] is a logical unit of work that may include any number of file or database updates. During normal processing, transaction consistency is present only Following a failure of some kind, the data will not be transaction consistent if transactions were in-flight at the time of the failure. In most cases what occurs is that once the application or database is restarted, the incomplete transactions are identified and the updates relating to these transactions are either “backed-out” or processing resumes with the next dependant write.
 * 1) A record is locked for viewing ONLY when someone is modifying it so that two people cannot modify it at the same time.
 * 2) Regular backups and transaction
 * Transaction Consistency**
 * before any transactions have run,
 * following the completion of a successful transaction and before the next transaction begins, and
 * when the application ends normally or the database is closed.

System Failures Types:
Hardware: Server failures, power outages, human error, - prevention: parallel systems are needed, support, hiring practices, Causes: Electrical outages.

Software: Software Bug - Viruses - Anti-virus software, - prevention with permissions Causes:

Security: Systems admin. permissions