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[F517]For Your Computer Network

by Bushra Bashir, Bus

Computer networking or data communication is a most important part of the information technology. Today every business in the world needs a computer network for smooth operations, flexibly, instant communication and data access. Just imagine if there is no network communication in the university campuses, hospitals, multinational organizations and educational institutes then how difficult are to communicate with each other. In this article you will learn the basic overview of a computer network. The targeted audience of this article is the people who want to know about the network communication system, network standards and types.

A computer network is comprised of connectivity devices and components. To share data and resources between two or more computers is known as networking. There are different types of a computer network such as LAN, MAN, WAN and wireless network. The key devices involved that make the infrastructure of a computer network are Hub, Switch, Router, Modem, Access point, LAN card and network cables.

LAN stands for local area network and a network in a room, in a building or a network over small distance is known as a LAN. MAN stands for Metropolitan area network and it covers the networking between two offices within the city. WAN stands for wide area network and it cover the networking between two or more computers between two cities, two countries or two continents.

There are different topologies of a computer network. A topology defines the physical layout or a design of a network. These topologies are star topology, bus topology, mesh topology, star bus topology etc. In a star topology each computer in a network is directly connected with a centralized device known as hub or switch. If any computer gets problematic in star topology then it does not affect the other computers in a network.

There are different standards and devices in computer network. The most commonly used standard for a local area network is Ethernet. Key devices in a computer network are hub, switch, router, modem and access point etc. A router is used to connect two logically and physical different networks. All the communication on the internet is based on the router. Hub/Switch is used to connect the computers in local area network.

Hopefully, in this article you may have learnt that what a computer network is, how important it is in our lives, what are different network devices, standards, topologies and communication types.

The GPS system is a worldwide navigational system operated by the US military. The system is maintained by USNO, the United States Naval Observatory. The Global Positioning System is implemented from space by 24 satellites in high orbit. Each satellite has precise timing equipment that can be used to triangulate position for navigational purposes. Low-cost GPS antennas and receivers are now widely available and provide precise time and frequency information worldwide.

This article presents an introduction to using the GPS system for computer timing applications. It describes the equipment that can be utilised to provide a precise time resource for computers and computer networks.

Each GPS satellite has a highly accurate atomic clock timing reference, which can be used by NTP servers to synchronise computer networks. Each satellite continually broadcasts accurate time and positioning information. This information can be received by a GPS receiver and externally mounted GPS antenna. The timing information received is referenced to UTC time. The system is a free to air service requiring no set-up or subscription fees.

Many Network Time Protocol (NTP) server systems utilise GPS time as an external timing reference to synchronise Windows, LINUX, UNIX and other operating systems and network infrastructures. GPS is an ideal time and frequency source because it can provide highly accurate time anywhere in the world using relatively cheap components.

Each GPS satellite transmits a very low-power radio signal at two frequencies; L1 and L2. L1 is the civilian frequency band transmitted at 1575 MHz, while L2 is used for military positioning purposes. The radio signal transmitted by each satellite can easily pass through material such as glass and plastics but are blocked more substantial materials used in buildings. The signals travel by line of sight. The ideal location for a GPS antenna is on a rooftop with a good view of the sky.

The radio signals can be received by a low-cost GPS antenna. The antenna is essentially a high gain amplifier, which is used to amplify and transmit the weak radio signals down a coax cable to a GPS receiver.

The cable length that can be utilised between a GPS antenna and receiver is critical. The maximum distance that can be utilised is dependant on the gain of the antenna and the quality of the coax cable used. High antenna gain and high quality coax allows for much longer cable runs.

GPS signal amplifiers can be fitted inline on the coax cable to boost the signal and increase cable length. GPS amplifiers are generally powered from the coax cable. The higher the gain provided by the amplifier, the longer the cable can be extended.

Roof-mounted antennas can be prone to lighting strikes or other voltage surges. A lightning strike up to a quarter of a mile away can damage electronic components. Therefore, it is recommended that a surge suppressor be fitted. Lightning or surge suppressors are installed inline on the GPS cable and redirect any surge to earth. Various types of surge suppressor are available, from gas discharge devices to solid-state multi-strike devices.

GPS receivers decode the signal received from the amplifier and generally make the received information available in a RS232 serial format. Most operating systems, including Microsoft Windows, LINUX and UNIX as well as time server systems can utilise the time output provided by the GPS receiver for accurate synchronisation. Many different GPS protocols are utilised, the most popular being NMEA. The NMEA protocol was developed by the National Marine Electronics Association. The protocol specifies a set of sentences that contain time and positioning information obtained by the GPS receiver. The sentences can be parsed by a PC or time server to obtain accurate time.

To summarise, the GPS system is an excellent source of precise time for NTP server systems or for synchronising stand-alone Windows, LINUX and UNIX PC's. By using relatively low-cost components, the Global Positioning System can provide time sensitive applications with precise timing information.

Article Source : Pg. 67

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Both Bushra Bashir & David Evans are contributors for EditorialToday. The above articles have been edited for relevancy and timeliness. All write-ups, reviews, tips and guides published by EditorialToday.com and its partners or affiliates are for informational purposes only. They should not be used for any legal or any other type of advice. We do not endorse any author, contributor, writer or article posted by our team.

Bushra Bashir has sinced written about articles on various topics from Information Technology, Personal Desktop and Computers and The Internet. B. Bashir manages and regularly writes articles on various topics such as Computer Networking,. Bushra Bashir's top article generates over 4400 views. to your Favourites.

David Evans has sinced written about articles on various topics from Computers and The Internet, Personal Desktop and Computers and The Internet. Dave Evans has provided a technical authoring service to the network timing and telecommunications industries for many years. Click here for more information on Windows, LINUX and UNIX timing and. David Evans's top article generates over 18100 views. to your Favourites.