Local Area Network (LAN) services allow users to share and access information and resources on a network. There are many types of services available for networks. Each type of service is responsible for performing a specific task. The most common are those that help users exchange files and information or use a network printer.
Network services are usually organized, managed and run on servers. Servers are powerful computers that have a lot of memory and processing power. Most servers on a network operate continuously.
A common service would be E-mail. E-mail enables people in a company to exchange information quickly. Many message services offer several features. Many allow users to exchange many different types of information, such as word processing documents, spreadsheets, video and sound files.
Print services allow users on a network to share the same printer. On many networks, the print server is directly connected the the printer. Since many users can send documents to the same printer, the printer may become overloaded. The print server can temporarily store print jobs until the printer is available. This is called spooling. Using a print service to share a printer eliminates the need to buy a printer for each user on the network. A print service may also be used to allow users to access a fax machine on the network.
Database services help people on a network manage and work with large amounts of information. Database services are one of the most common types of services found on corporate networks. A client computer is used to request information from the database server. Most databases consist of information that may be restricted. Database security is one of the primary concerns of a database service. Database services use a language called Structured Query Language (SQL) to perform instructions which access and work with information in the database.
Assignment:
What is spooling?
What is SQL?
If you work from a LAN, what are the common services provided by the network to you?
A network operating system is the software used to control the overall activity of a network. Many networks use computers, called servers, to run the network operating system. A network may use many resources, such as fax modems, printers and software applications. Many network operating systems have sophisticated security features to control access to information and devices on the network.
An operating system driver is software that allows the computers on a network to communicate with the network operating system. A computer must have the appropriate drivers to access the network.
Windows for Workgroups is the networking version of the Windows 3.1 operating system. Windows for Workgroups is a Graphical User Interface that runs on computers using the DOS operating system. Since it requires DOS it is not considered a "true" operating system. Operating systems are often identified by the amount of information they can process at once. Windows for Workgroups can process 16 bits of data at one time. It cannot run programs designed for an operating system that can process more information at once.
Windows 95 is a graphical, easy-to-use operating system. Although Windows 95 is often found on personal computers, many companies use it as a network operating system. The Windows 95 operating system operates on a peer-to-peer network. Each computer that runs Windows 95 can exchange information and resources with other Win-95 computers on the network.
Windows NT is a powerful network operating system available in two main versions, the NT Server and the NT Workstation. The NT Server is found on coient/server networks and supports the heavy processing demands of a dedicated network server. It can use a variety of operating systems. NT Workstation is used frequently on peer-to-peer networks and can run most applications that were designed to work on earlier versions of the Windows operating system. Both versions are 32-bit operating systems.
UNIX is an older, powerful operating system that can be used to run an entire network or a single user's computer. There are several versions of the UNIX operating system available. Hewlett-Packard makes a UNIX operating system called HP-UX. IBM's UNIX system is called AIX. Linux is a free version of UNIX available on the WWW at http://www.linux.org.
Assignment:
What Operating System are you using on your computer?
If you are using a networked computer, what Operating System your Network running?
The Internet is essentially a network of networks and its success depends upon "cooperation." Since no one person, organization, or government is responsible for the Internet, cooperation among the networks and computers that compose the Internet is paramount. The way that the computers and networks cooperate is by using the same set of protocols to communicate with one another.
The International Standardization Organization (ISO) is an organization that develops product standards for the computer industry and coordinates the activities of other standards organizations. The ISO's main objective is to allow networks to work together efficiently. They developed the Open Systems Interconnection (OSI) model which is a set of guidelines that describes all the aspects of the communication process and how applications and devices should work in order to communicate with each other on a computer network.
There are seven layers, or sections, in the OSI model. Each layer is responsible for one particular aspect of communication. They are:
Application
Presentation
Session
Transport
Network
Data Link
Physical
Before two computers or network devices can exhange information, they must establish communication. A network protocol allows two devices to communicate using the same set of rules. Protocols are the actual hardware or software components that carry out the OSI model guidelines for transferring information on a network.
The protocol that determines how computers connect, send, and receive information on the Internet is called Transmission Control Protocol/Internet Protocol (TCP/IP). (The Cerf document in the Cyberspace/History section of the Internet Concepts and Applications course, briefly introduces the man who created TCP/IP, why it is called Cerfing the Internet, and gives an explanation of TCP/IP.) TCP/IP consists of about 100 different protocols and new ones are regularly developed and added. Think of these protocols as forming the "rules of the road" ranging from who has the right of way to how you register your vehicle and get a driver's license.
TCP/IP has been described as the "language of the Internet." In the same way that a common language allows people of diverse backgrounds to communicate, TCP/IP allows many different kinds of computers, from personal computers to mainframes, to exchange information.
Transferred information is "formatted" according to it's specific application protocol. For instance, Simple Mail Transfer Protocol (SMTP) is used for your e-mail message and Hypertext Transfer Protocol (HTTP) is used for your Web page request. Once your computer has TCP/IP software installed, the information to be sent is split into IP packets and transmitted over the Internet. There are three advantages of packets:
Error Recovery : if a packet gets corrupted, only that packet needs to be resent and not the entire message.
Load Distribution : if one area of the network is congested, packets can be rerouted to less busy areas.
Flexibility : if the network experiences a failure or disruption in one local, packets can be rerouted.
Assignment:
Explain how the Internet transfers information in your words.
What do you think is the most important advantage to IP packeting?
Someone connecting to the Internet from home generally uses a modem and a regular telephone line, copper wire, to connect to an Internet Service Provider (ISP). A second modem completes the connection at the ISP's end and the slower of the two modem speeds determines the maximum connection speed - 28.8 kilobits per second (Kbps) is still the typical speed. Some important parts of the network are still audio-based, for example the part of the phone system in your home or office. This means that modems are needed to convert from analog to digital and back again.
A business, organization, or school network typically uses network interface cards instead of modems to join the personal computers that are part of their LAN. Such a connection often has a higher speed connection, usually 56 Kbps or better, to connect to their ISP. A kilobit is 1,000 bits. These connections are leased from the telephone company.
Another option is Intergrated Services Digital Network (ISDN) which provides connections with speeds up to five times faster than a traditional modem. By using regular telephone lines and replacing modems with special adaptors, ISDN offers a slightly more expensive but much faster alternative to a modem.
On the horizon is both a cable television connection and Teledesic, that is going to put 841 low earth orbit satellites in the sky and offer data service everywhere.
So. if the ISP is our "driveway" rights to the highway, then the freeways of the Internet are what are called the "backbones". These backbones are run by Network Service Providers (NSPs). Local ISPs connect to NSP networks like AT&T, MCI, or Sprint. The connection between the ISP and the NSP is over leased-lines from local telephone companies. These phone lines typically transmit data at a rate of 1.54 megabits per second (Mbps). A megabit is 1,000,000 bits.
The NSPs lease or buy lines consisting of copper wire, fiber-optic cable, or satellite communications from companies such as AT&T, MCI, or WorldCom.
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