通信网络英语ppt

Important Dates in the History of Data Communications (1)

1837 – Invention of the telegraph 1876 – Invention of the telephone 1947 – Invention of the transistor (replaced vacuum tubes) 1948 – First commercial computer installed, the UNIVAC I 1958 – First U.S. Communications satellite sent into orbit 1959 – FCC approves private microwave communications networks 1964 – Packet switching network concept proposed by the Rand Corporation 1966 – IBM's binary synchronous (BISYNC or BSC) protocol announced 1969 – ARPANET, first packet switching network (later to become the Internet), begins operation
Hardware: Computer Network card Routers Modem … Media: Cable Wire Microwave …
Components of a Computer Network
Software: Network OS Utilities … Network Design: Logical layout Physical layout …
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What is a Computer Network?
Two or more computers or communications devices connected by transmission media and channels and guided by a set of rules for communication purposes that allow users to communicate with each other and share applications and data.
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Important Dates in the History of Data Communications (2)
1972 – Ethernet local area network specifications formulated 1972 – IBM's Synchronous Data Link Control (SDLC) protocol
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Computer Systems Redefined
Computer systems used to be defined as:
hardware + software
Computer systems are now redefined as:
hardware + software + networks
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Essentials of Data Communication

Message Sender Receiver Medium Understandability Error detection Security
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Types of Messages
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Protocols
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Applications of a Computer Network
Mass transit Interstate highways 24-hour bankers, grocery stores Cable television Pagers Mobile telephones Most businesses and schools Retail outlets …
• Star Topology
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Network Technologies
Ethernet
Based on bus topology; but can be used in star topology; Higher speed: first Fast Ethernet, then Gigabit Ethernet; Most popular: inexpensive, easy to install and maintain. Based on a ring topology; but can use a star topology; Token-passing scheme to prevent collision of data; The second most widely-used protocol after Ethernet. Based on client/server model of network computing; Uses packet switching technique for data transmission; Commonly used for Internet applications. Uses client/server model of network computing; Allows wireless devices to access the Internet and WWW; Meets increasing demands for wireless Internet access.
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Data Communication Applications (2)
Interactive - Short inputs and outputs.
Real-time response with direct user interaction Sensor-Based - Input derived from sensors instead of human operators Combined - More than one of the above applications running at the same time
Enables communication – how we

communicate (convention used for establishing transmission rules)
When Where How What with How much


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Protocols
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What is Information Technology (IT)?
Information Technology (IT)
Computer Technology To collect, store, process, search, retrieve, and present electronic information to meet the needs of various kinds of users, e.g., computer hardware & software, PDAs, printers, groupware, smart cards…. Communication Technology To deliver, disseminate, exchange, transmit, and receive electronic information in local, regional or global contexts, e.g., networks, fax machines, cell phones, email, satellites, GPS, Internet, telephony, ….
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Information & Communication
Generation and transfer of information
is critical to today’s businesses Flow of information both mirror and shape organizational structures Networks are the enabling technology for this process
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What is Data Communication?
Communication of data between sources Data formats – analog or digital or both Data travels by a medium

Wires Space
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Network Essentials
Models
• Client/Server
Technologies
• Ethernet • Token Ring • Transmission Control Protocol/Internet Protocol (TCP/IP) • Wireless Application Protocol (WAP)
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Data Communication Applications (1)
Batch - bi-directional transfers of large
amounts of data in concentrated groups Data Entry - Lengthy inputs with short responses Distributed - data and/or processing is handled by more than one processing unit Inquiry/Response - Small inputs of data that may result in large responses
announced 1974 – IBM announces its Systems Network Architecture (SNA) 1975 – Personal computers introduced, the Altaire 8800 replaced terminals in many cases 1981 – IBM PC introduced 1985 – Cellular radio telephones are introduced 1990 – World Wide Web is introduced 1993 – Web search engines introduced 1995 – The Internet grows to over four million host computers 1999 – The Internet grows to over ten million host computers
IST 220-002: Networking and Telecommunications Chapter 1: Introduction to Computer Networks & Data Communication
Dr. Lee Giles 001 Thomas Building, School of IST Phone 865 7884 Email: giles@
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The “Manager’s Dilemma”
Technology is necessary for
competitiveness Cost of technology has decreased Reliance on technology has increased sed Choices are both more difficult and more important
• Peer-to-Peer
Types
• Local Area Network (LAN) • Metropolitan Area Network (MAN) • Wide Area Network (WAN)
Network OS Topologies
• Bus Topology
• Ring Topology