COMPUTER NETWORK
.docxINTERNET AND LAN TECHNOLOGIES
Hello everyone, today I want to say some words about computer networking. Nowadays computer network is so important part of everybody. Do you agree with me? I think you agree with me because it is absolutely clear. With help of networking, we can get favorite item of our life such as Internet. We use the Internet with different purposes. The most popular purposes are communication with other people, playing games, watching some videos or just see news of our world. Now I would like to describe some aspects of computer networking. Today, networks are everywhere and everyone wants to be connected. Networks can be classified according to their size and geographic scope (PAN, LAN, MAN, WAN).
Geographical area
PAN (personal area networks) connect laptop and mobile.
LAN (local area networks). A typical example is a college or university computer network.
MAN (metropolitan area networks) cover campus or a city.
WAN (wide area networks).
You can think of a network as a spider web with many interconnecting points, referred to as node. A network node usually contains a computer, networked peripheral, or network device. To connect to a LAN, a computer requires network circuitry, sometimes referred to as a network interface card (NIC). Network circuitry is built into the main system board of most personal computers. If not, a NIC can be added to a slot in the system board or a USB port.
A networked peripheral is any device that contains network circuitry to directly connect to a network. Printers, scanners, and storage devices are examples of devices that can be equipped to directly connect to a network instead of connecting to a workstation.
A storage device that directly connects to a network is called network attached storage (NAS). A network device is any electronic device that broadcasts network data, boosts signals, or routes data to its destination. The most important network device is a router, which acts as a central distribution point for getting data to its destination. Network devices also include hubs, switches, gateways, bridges, wireless access points, and repeaters.
Data in a network with wired connections travels from one device to another over cables. Wired connections are fast, secure and simple to configure. This type of connection is more secure than wireless one because a computer can only join a network if it is physically connected by a cable. An example of wired network technology is Ethernet. Ethernet is a family of a computer networking technologies commonly used in LAN, MAN and WAN.
A network without wires transports data through the air, eliminating the need for cables. Networks of all sizes, from PANs to LANs and WANs, can use wireless technologies, such as radio signals, microwaves, and infrared light. Most wireless connections transport data as RF signals (radio frequency signals). They are sent and received by a transceiver (a combination of a transmitter and a receiver) that is equipped with an antenna. Workstations, peripheral devices and network devices can be equipped with transceivers.
The most popular wireless LAN technology is WI-FI. WI-FI refers to a set of wireless networking technologies defined by IEEE802.11 standards. A WI-FI device transmits data as radio waves and is compatible with Ethernet, so you can use the two technologies in a single network. Additional wireless technology is Bluetooth. Bluetooth is a short-range wireless network technology that is designed to make connections between two devices. A communications channel or link, is a physical path or a frequency for signal transmissions.
Cloud computing encompasses most Internet-enabled activities including Webmail, Google searching, social networking, blogging and photo sharing. The concept of cloud computing is that apps and data are available any time, from anywhere, and on any device. Cloud computing depends on a grid of servers, storage devices, and protocols that offer Internet-accessible computing ranging from consumer-level media sharing to office productivity applications and complex corporate data processing. These resources are maintained by Internet service companies, such as Google, Amazon, Apple, and Microsoft. For example, Apple maintains a 500.000-square-foot facility for its iCloud data center where subscribers can store music, photos, data files, backups, reminders and contracts. Microsoft offers a similar cloud service called SkyDrive.
Consumers have several options for connecting to the Internet. Fixed Internet access links your computer to an ISP from a stationary point, such as wall socket or roof-mounted antenna. Portable Internet access allows you to easily move your access device, as in the case of vehicle-mounted satellite dishes that can be deployed when the vehicle is parked. It is light and compact enough to easily carry. Like a fixed satellite dish, a portable dish transmits signals to and receives signals from a geostationary satellite. Mobile Internet access allows you to use Internet as you are on the go, such as using a cell phone to collect your e-mail while you are traveling by train. You are not necessarily limited to a single Internet access option. Many consumers find it convenient to maintain fixed Internet access for home use, but use portable or mobile method of Internet access while out.
A communication protocol refers to a set of rules for efficiently transmitting data from one network node to another. Protocols set standards for encoding and decoding data, guiding data to its destination. Specifically, protocols are responsible for the following aspects of network communications: dividing messages into packets, affording addresses to packets, initiating transmission, regulating the flow of data, checking for transmission errors, acknowledging receipts of transmitted data.
Symmetric key encryption uses the key to encrypt a message as well as decrypt it. Symmetric keys are not practical for e-mail and other situations in which the person receiving encrypted data does not have the key beforehand.
Public key encryption eliminates the key-distribution problem by using one key to encrypt a message, but another key to decrypt the message. Public key encryption is a crucial technology for e-commerce and e-mail. When you use a secure connection to transmit a credit card number, the server sends a public key to your browser.