Transcript 2 Basic Concepts: data and computer networking

2 Basic Concepts: data and
computer networking
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Line Configuration
Topology
Transmission Mode
Categories of Networks
Internetworks
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2.1 LINE CONFIGURATION
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Defines the attachment of
communication devices to a link
Two categories:
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Point-to-Point
Multipoint
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Point-to-Point Line
Configuration
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Dedicated link with entire capacity of
the channel reserved for communication
Examples:
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PC to PC (workstation)
Mainframe to PC (Workstation)
Satellite links
PC
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Workstation
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Multipoint Line Configuration
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Multidrop
Sharing a single link:
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Spatially
Time sharing
PC
Laser printer
Ethernet
Laptop computer
Notebook computer
PC
Laptop computer
Notebook computer
Laser printer
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2.2 TOPOLOGY
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Logical or physical layout of a network
Two or more links form a topology
Five Basic Topologies:
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Mesh, Star, Tree, Bus, Ring
Ethernet
T oken-ring
Hub
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2.2 TOPOLOGY (continue)
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Relationships among devices:
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Peer-to-Peer
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Share communication link equally
Primary-Secondary
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Master traffic controller
Ethernet Hub
Terminal server
Mainframe
Hub
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Mesh Topology
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Every device has a dedicated point-topoint link to other device
A fully connected mesh network:
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n(n-1)/2 physical channels to link to n
devices
n-1 I/O ports
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Mesh Topology (continue)
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Example 1: three nodes or computers
Number of links: n(n-1)/2 = 3
Number of ports: n-1 = 2
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Mesh Topology (continue)
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Example 2: Four nodes or computers
Number of links: n(n-1)/2 = 6
Number of ports: n-1 = 3
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Mesh Topology (continue)
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Implementation: usually implemented
in a limited fashion -- a backbone
connecting the main computers of a
hybrid network
Example: ARPARNET
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Mesh Technology
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Advantages:
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Dedicated point-to-point links (eliminating
traffic problems)
Robust (high reliability, traffic can be
routed)
Privacy or security (communications only
between sender and receiver)
Easy fault identification and fault isolation
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Mesh Technology
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Disadvantages:
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High cost (amount of cabling and number
I/O ports)
Difficult to install and reconfigure
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Example 3:
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8 devices
Mesh topology
I/O port and links calculation
Answer:
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Number of links = n(n-1)/2 = 8(8-1)/2 =
28
Number of ports per device = n-1 = 8-1 =
7
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Star Topology
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Hub (central controller) acts as a
exchange controller which relays the
data to other connected devices
Each device has a dedicated point-topoint link only to a central controller
Hub
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Star Topology
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Advantages:
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Less expensive than a mesh topology
Robust (high reliability): if one link fails, all
other links remain active
Easy fault identification and fault isolation
through central hub
Disadvantages
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Require more cabling than in tree, ring or bus
topology (far less cable than a mesh)
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Tree Topology
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A variation of star
Nodes in a tree are linked to a central
hub that controls the traffic to the
network
TO
Backbone
Hub: ET Building
Hub: ET217
HUB: ET 215 Lab
Hub: LIN Office
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Tree Topology
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Secondary hubs:
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For connecting devices
Active or passive
Central hub:
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An active hub
Repeater (enhance signals for transmitting
over a longer distance)
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Tree Topology (continue)
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Advantages (same as star topology):
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Same advantages as star topology
Allow more devices to be attached to a single
central hub
Allow the network to isolate and prioritize
communications from different computers
Disadvantages (same as star topology)
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Require more cabling than bus or ring topology
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Bus Topology
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Multipoint configuration: one long cable
acts as a backbone to link all the
devices in the network
Computers are connected to the bus
cable by drop lines and taps
Tap
Tap
Tap
Ethernet Bus
Tap
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Tap
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Bus Topology (continue)
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Advantages
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Ease of installation
Less cabling than mesh, star, or tree
topologies
Disadvantages
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Difficult reconfiguration and fault isolation
Less Robust (a fault or break in the bus
cable stops all transmission)
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Ring Topology
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Dedicated point-to-point line
configuration only with the two devices
on either side of it
Repeaters
A signal is passed along the ring in one
direction from device to device, until it
reaches its destination
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Ring Topology (continue)
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Advantages
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Relatively easy to install and reconfigure
(maximum ring length and number of devices)
Easy fault isolation
Disadvantages
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Unidirectional traffic
A break in the ring can disable the entire network
(use dual ring or a switch)
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Hybrid Topologies
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A Combination of various topologies:
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Star (hub)
Ring
Bus
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2.3 Transmission Mode
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Three modes:
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Simplex: one direction, either as
transmitter or receiver
Half-duplex: both direction; can transmit or
receive, but one at a time
Full-duplex: can transmit and receive
simultaneously
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Transmission Media
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Coaxial cable: CATV, cable modem
Shield twisted pair
Un-shield twisted pair (UTP): category 5
-- up to 100 MHz
Optical fiber
Wireless: microwave, satellite, radio,
infrared
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2.4 Categories of networks
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Local Area Network (LAN)
Metropolitan Area Network (MAN):
Wide Area Network (WAN):
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Long distance transmission of data, voice,
image, and video information
Enterprise network (owned by a single
company)
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Local Area Network (LAN)
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Privately owned links and computers in
a single office, building, or campus
Bus, Ring, and Star topologies
Topologies: bus, ring, star, wireless,
infrared
Data rates: 2 Mbps, …, 10 Mbps, 100
Mbps, Gigabits
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Metropolitan Area Network
(MAN)
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City wide coverage
LAN-to-LAN
LAN-to-other larger network
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Wide Area Network (WAN)
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Long distance transmission of data, voice,
image, and video information
Enterprise network (owned by a single
company)
Technologies:
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ATM (Asynchronous Transfer Mode)
Frame Relaying
X.25 (Packet switching network)
Circuit switching
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2.5 Internetworks
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IBM Dictionary of Computing defines
internetworking as “communications
between two or more networks”
Two or more connected dissimilar
networks:
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Ethernet, Token Ring
Dial-up lines to ISDN (Integrated Services Digital
Network)
ATM
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2.5 Internetworks (continue)
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Internet (World Wide Web
Router
Gateways
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