| TECHNICAL ENGLISH II No.5 | May 8,2002 |
Generality:
In 1977, Apple Computer popularized the phenomenon of personal computing. Initially, it was a hobbyist's dream. Computers became economical enough for people to buy them for their own personal use. In 1981 IBM, the world's largest computer vendor, introduced the IBM Personal Computer. Almost overnight, personal computing became legitimate in business, industry and government organizations.
*phenomenon : something that happens or exists in society, science, or nature, often something that people discuss or study because it is difficult to understand
*legitimate : correct, allowable, or operating according to the law
But these computers were "standalone" units-people did their work on their own machines and transported disk back and forth to share information. Although early personal computers were not powerful enough to timeshare several users, these machines could be linked together in computer networks, sometimes over telephone lines and sometimes in local area networks (LANs) within an organization. This led to the phenomenon of distributed computing, in which an organization's computing, instead of being performed strictly at some central computer installation, is distributed over networks to the sited at which the real work of the organization is performed. Personal computers were powerful enough to both to handle the computing requirements of individual users and to handle the basic communications tasks of passing information back and forth electronically.
*distribute : to give something such as food, medicine, or information to each person in a group
Today's most powerful personal computers are as powerful as the million-dollar machines of just a decade ago. The most powerful desktop machines-called workstations provide individual users with enormous capabilities. Information is shared easily across computer networks where some computers called file severs offer a common store of programs and data that may be used by client computers distributed throughout the network (hence the term client/server computing). C and C++ have become and remain the languages of choice for writing operating systems. They also remain popular for writing computer networking, distributed clients/server and Internet and Web applications, although Java is now the discovered that programming in Java helps them be more productive than programming in C or C++. Today's popular operating systems, such as UNIX, Linux, MacOS, Windows NT and Windows 2000, provide the kinds of capabilities to control the network.
Details:
Popular network operating systems include Windows, Mac, Linux, Netware, and OS/2. This document describes the computer networking from the operating system point of view.
NOS - A Definition
The term "NOS" stands for network operating system. A NOS contains protocols stacks as well as device drivers for network hardware, ...
Basic Network Design - The OSI Model
The Open Systems Interconnection (OSI) reference model has served as one of the most basic, yet essential, elements of computer networking since its inception in 1984. OSI is an abstract model, meaning that actual network implementations need not adhere to it strictly. OSI is also standards effort, a product of the International Standards Organization (ISO). (And OSI is ISO spelled backwards, just to add to the fun). But despite being an abstract standard, the OSI divides the big task of host-to-host networking - traditionally called internetworking - into a vertical stack. The OSI stack contains these seven layers (in order from top to bottom):
The Layered Approach
The layered approach to OSI offers several advantages to system implements. By separating the job of networking into logical smaller pieces, vendors can more easily solve network "problems" through divide-and-conquer. A product from one vendor that implements Layer 2, for example, will be much more likely to interoperate with another vendor's Layer 3 product when both vendors follow this standard model. Finally, the OSI layers afford extensibility. New protocols and other network services will generally be easier to add to a layered architecture than to a monolithic one.
Application and Network
OSI designated the application, presentation, and session layers as "upper layers." Generally speaking, software in these layers performs application-specific functions like data formatting, encryption, and connection management. The remaining "lower layers" provide more primitive network-specific functions like routing, addressing, and flow control.
TCP/IP definition
Technically, Transmission Control Protocols (TCP) and Internet Protocols (IP) are two distinct network protocols. TCP and IP are so commonly used together, though, that "TCP/IP" has become standard terminology to refer to either or both of the protocols.
IP roughly corresponds to the Network layer (layer 3) in the OSI model, whereas TCP corresponds to the Transport layer (layer 4) in OSI. In other words, the term TCP/IP refers to network communications where the TCP transport is used to deliver data across IP networks. The average person on the Internet works in a predominately TCP/IP environment. Web browsers, for example, use TCP/IP to communicate with Web servers.
Local Area Networks(LANs) cover a limited physical distance whereas Wide Area Networks (WANs) cover much lager areas. The jargon of "area networks" includes many other possibilities.
LAN - A Definition
A local Area Network (LAN) supplies connectivity to a group of computers in close proximity to each other such as office building, a school or a home.
WAN - A definition
A wide area network (WAN) spans a large geographic area, such as a state, province or country.
Virtual LANs (VLANs)
Virtual LANs (VLANs) support logical grouping of network nodes to reduce broadcast traffic and allow more control in implementing security policies.
SONET - A definition
SONET is a physical layer netowork technology designed to carry large volumes of traffic over long distance on fiber optic cabling.
Local Area Network Fundamentals
Explain the characteristics of a LAN, relationship to the OSI reference model, twisted pair and coax cable, transmission modes, and connection-oriented / connectionless service.
LANs, WANs, and Other Area Networks
Besides LANs and WANs, other types of area networks like MAN and SAN also exist. Find out more about the difference between LANs, WANs, and all the rest.
REVIEW QUESTIONS:
1.According to the text, explain the term "distributed computing."
2.What is an OSI model and describe its architecture. Give an example of products, specifications or protocols for each OSI layer.
3.Which language is used to develop the network application in the past and now?
4.What is VLAN?
COMPUTING NEWS QUESTIONS:
5. If you want to build a wires computing system inside the campus, which of the following protocols can you use?
a. WAN
b. Wireless LAN
c. Wireless Modem
d. SONET
e. Bluetooth
f. SWAP
6. What is IEEE 802.11? Give its definition. (Find this information in the WWW)
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