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7/27/2019 Lecture Intro to Networks
http://slidepdf.com/reader/full/lecture-intro-to-networks 1/35
P G D M T R I M E S T E R I
Computer Networks
7/27/2019 Lecture Intro to Networks
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Learning Objectives
ITBM, 2014
Define the basic terminology of computer networks
Recognize the individual components of the bigpicture of computer networks
Outline the basic network connections Define the term “convergence” and describe how it
applies to computer networks
Communication software and protocols
Network topology
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Introduction
ITBM, 2014
Who today has not used a computer network?
Mass transit, interstate highways, 24-hour bankers,grocery stores, cable television, cell phones,
businesses and schools, and retail outlets supportsome form of computer network
Computer network – an interconnection of computers andcomputing equipment using either wires or radio waves
over small or large geographic areas
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The Language of Computer Networks
ITBM, 2014
Types:
Personal area network – a network spanning an area of afew meters around an individual. Include devices such asPDAs, laptops, and wireless connections.
Local area network – networks that are small in geographicsize spanning a room, floor, building, or campus
Metropolitan area network – networks that serve an area ofupto 30 miles, approximately the size of a typical city
Wide area network – a large network that encompasses partsof states, multiple states, countries, and the world
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The Language of Computer Networks (cont.)
ITBM, 2014
Voice network – a network that transmits telephonesignals
Data network – a network that transmits computerdata
The merging of voice and data networks is termedconvergence.
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The Language of Computer Networks (cont.)
ITBM, 2014
Data communications – the transfer of digital oranalog data using digital or analog signals
Issues:
Data and Signal Multiplexing
Compression
Error detection and control
Network management – the design, installation, andsupport of a network, including its hardware andsoftware
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The Big Picture of Networks
ITBM, 2014
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The Big Picture of Networks
ITBM, 2014
Networks are composed of many devices, including:
Workstations (computers, telephones)
Servers (store network software and shared or private userfiles)
Network hubs and switches (bridges)
Routers (LAN to WAN and WAN to WAN)
Telephone switching gear
High speed transmission lines
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Communications Networks – Basic Connections
ITBM, 2014
Computer terminal / microcomputer-to-mainframe
Microcomputer-to-local area network
Microcomputer-to-Internet
Local area network-to-local area network Personal area network-to-workstation
Local area network-to-metropolitan area network
Local area network-to-wide area network Sensor-to-local area network
Satellite and microwave
Wireless telephone and wired telephone to network
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Terminal/Microcomputer-to-Mainframe ComputerConnections
ITBM, 2014
Predominant form inthe 1960s and 1970s
Still used in many
types of businessesfor data entry anddata retrieval
Usually involves a
low-speed connection
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Microcomputer-to-Local Area NetworkConnections
ITBM, 2014
Highly common throughout business and academicenvironments, and now homes
Objective: Resource sharing
Typically a medium- to high-speed connection Computer (device) requires a NIC (network interface
card)
NIC connects to a hub-like device
Other issues:
Client/server system
Wireless LAN
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Microcomputer-to-Local Area NetworkConnections
ITBM, 2014
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Microcomputer-to-Internet Connections
ITBM, 2014
Popular with home users and small businesses
Often a dial-up modem is used to connect user’s microcomputer to anInternet service provider (ISP)
Technologies such as DSL and cable modems are replacing modems forhigher speeds.
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LAN to LAN Connections
ITBM, 2014
Found in systems that have two or more LANs and aneed for them to intercommunicate
A bridge-like device (such as a switch) is typically
used to interconnect LANs Switch can filter out traffic.
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ITBM, 2014
LAN to LAN Connections
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PAN -to-Workstation Connections
ITBM, 2014
Interconnects wireless devices such as PDAs, laptopsand notebooks, and music playback devices
Used over short distances such as a few meters
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LAN-to-MAN Connections
ITBM, 2014
Used to interconnect companies (usually their local area networks) tonetworks that encompass a city
High-speed networks using fiber-optic links
They can transfer data at fast, LAN speeds but over larger geographicregions than typically associated with a LAN.
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LAN-to-WAN Connections
ITBM, 2014
One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network)
A router is the typical device that performs LAN to WAN connections
Routers are more complex devices than switches
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WAN-to-WAN Connections
ITBM, 2014
High-speed routers and switches are used to connectone wide area network to another
Internet: Collection of thousands of networks.
Issues: Addressing
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Sensor-to-Local Area Network Connections
ITBM, 2014
Often found in industrial and laboratory environments
Assembly lines and robotic controls depend heavily onsensor-based local area networks
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Satellite and Microwave Connections
ITBM, 2014
Typically long distance wireless connections
Many types of applications including long distancetelephone, television, radio, long-haul data transfers,
and wireless data services Typically expensive services but many companies
offer competitive services and rates
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ITBM, 2014
Satellite and Microwave Connections
(continued)
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Wireless Telephone Connections
ITBM, 2014
Constantly expanding market across the U.S. and world
Third generation services available in many areas
and under many types of plans
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ITBM, 2014
Wireless Telephone Connections (continued)
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CORPORATE NETWORK INFRASTRUCTURE
ITBM, 2014
Today’s corporatenetwork infrastructureis a collection of manydifferent networksfrom the public
switched telephonenetwork, to theInternet, to corporatelocal area networkslinking workgroups,
departments, or officefloors.
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Convergence
ITBM, 2014
As a process of coming together toward single point. Voice transmission systems converging with data
transmission systems. – telephone-to-network Telephone systems are now carry more data than voice
Common configuration – telephone connected to POTSNewer configuration (VoIP) – telephone-to-LAN via gateway or
telephone to gateway via DSL/cable
Cell phones can act as Web phones
Television sets connect to Internet Wireless technologies combined in same device
enhance functionality
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Packet switching
Method of slicing digital messages into parcels (packets), sendingpackets along different communication paths as they becomeavailable, and then reassembling packets at destination
Circuit-switched networks: requires complete point-to-point circuit as intelephone system.
Packet switched: More efficient use of network’s communicationscapacity
ITBM, 2014
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Communications Software and Protocols
Communications protocol: set of rules that governs theexchange of information over a communications channel
The principal functions of protocols in a network are
Line access concerns how the sending device gains access to the
network to send a message. Collision avoidance refers to managing message transmission so that
two messages do not collide with each other on the network.
Other functions of protocols are
to identify each device in the communication path,
to verify correct receipt of the transmitted message,
to verify that a message requires retransmission because it cannot becorrectly interpreted, and
to perform recovery when errors occur.
ITBM, 2014
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TCP/IP
The Transmission ControlProtocol/Internet Protocol(TCP/IP) is a protocol forsending information acrosssometimes-unreliable networks
with the assurance that it willarrive in uncorrupted form.
TCP/IP allows efficient andreasonably error freetransmission between differentsystems and is the standardprotocol of the Internet andintranets.
ITBM, 2014
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TCP/IP
ITBM, 2014
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Communications Software and Protocols
Common Telecommunications Protocols
ITBM, 2014
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Communications Software
Network operating system (NOS): systems software that
controls computer systems and devices on a network and allows themto communicate with each other
Network-management software : It performs functions
that decrease the human resources needed to manage the network. These functions reduce time spent on routine tasks, such as remote,
electronic installation of new software on many devices across anetwork.
They also provide faster response to network problems, greater
control over the network, and remote diagnosing of problems indevices connected to the network.
Scans for viruses and Ensures compliance with software licenses
ITBM, 2014
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Network Topology
The topology of a network is the physical layout andconnectivity of a network. Specific protocols, areoften used on specific topologies.
There are several basic network topologies: star,
bus,
ring,
mesh, and
hierarchical.
Networks that combine more than one type (such as a ringsegment connected to a star segment) are consideredhybrid topologies
ITBM, 2014
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Network Topology
ITBM, 2014