Transcript star topology

Dammam Community
College
Chap 5 Part 2
Network Overview
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Advantages of networks
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Enable sharing of files
Enables sharing of resources
It saves time
Internet access
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What is a Network ?
• Two or more computers connected
together by a cable.
• LAN - Local Area Network
• MAN - Metropolitan Area Network
• WAN - Wide Area Network
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Basic Network Components
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Network Interface Cards - NIC
Network cabling & connections
Servers & Workstations
Network Operating System – NOS
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Extending a LAN
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Repeaters
Bridges
Routers
Gateways
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Network Interface Card
Assignment for the students about following:
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Interrupt (IRQ) request line
Base I/O port address
Base memory address
Direct memory access (DMA) request line
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Basic Types of LAN’s
• Peer-to-Peer: Two computers participating
equally in the network.
• Server Based: Security and other network
functions are provided by a dedicated
server.
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Network Elements
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Sending Computer
Receiving Computer
Protocol
Media - Wire or Wireless
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Network Protocols
• A protocol is a set of rules that govern network
communication.
• A protocol suite is a group of protocols that can be
used together.
• The standard protocols are
– Internetwork Packet Exchange/Sequenced Packet
Exchange (IPX/SPX)
– Networked Basic Input/Output System/NetBIOS Enhanced
User Interface (NetBEUI)
– Transmission Control Protocol/Internet Protocol (TCP/IP)
– AppleTalk
– Data Link Control (DLC)
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Protocols Summary
Protocols - A set of rules for a network
Examples:
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TCP/IP
TELNET
IPX/SPX
NET BEUI
To cater for the following types of networking
technology:
Ethernet
Fast Ethernet
Token Ring
FDDI
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Main Types of Cable
• Coaxial Cable
• Twisted Pair
• Fiber Optic
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Network Cabling
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Cabling types and advantages
Three different types of network cabling and
their advantages are:
1. Twisted pair cable is readily available, easy to
install and inexpensive
2. Coaxial cable is standard technology that
resists rough treatment and EMI, can transmit
over longer distance than twisted pair
3.Fibre Optic cable is immune to EMI and
detection outside and provides reliable and
secure media with high bandwidth
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Types of Cable Connectors
• BNC Connector
• RJ-45 Connector
• Duplex SC
Connector
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Ethernet Cable Summary
Specification
Cable Type
Maximum length
10BaseT
Unshielded Twisted Pair
100 meters
10Base2
Thin Coaxial
185 meters
10Base5
Thick Coaxial
500 meters
10BaseF
Fiber Optic
2000 meters
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LAN Communication
• Ethernet uses Carrier Sense
Multiple Access with Collision
Detection (CSMA/CD) as well
as bus topology.
• Token ring allows only the
station holding the token to
transmit data.
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LAN Topology
Topology is the way the network is
connected physically. Following are
topologies:
• Bus Topology
• Ring Topology
• Star Topology
• Mesh Topology
• Hybrid Topology
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BUS TOPOLOGY
PRINTER
WORKSTATION 1
T-CONNECTOR
WORKSTATION 2
WORKSTATION 3
SERVER
TERMINATOR
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Workstation 5
Workstation 4
server
RING
TOPOLOGY
Workstation 3
printer
Workstation 2
Workstation 1
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STAR TOPOLOGY
WORKSTATION 5
WORKSTATION 4
WORKSTATION 3
HUB
WORKSTATION 6
SERVER
PRINTER
WORKSTATION 2
WORKSTATION 1
PRINTER
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Workstation 5
Workstation 4
server
MESH
TOPOLOGY
Workstation 3
printer
Workstation 2
Workstation 1
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HYBRID TOPOLOGY
STAR TOPOLOGY
Workstation 5
WORKSTATION 5
WORKSTATION 4WORKSTATION
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Workstation 4
server
HUB
RING
TOPOLOGY
Workstation 3
WORKSTATION 6
WORKSTATION 2
printer
SERVER
Workstation 2
Workstation 1
WORKSTATION 1
PRINTER
PRINTER
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Networking Essentials
• Local Area Network (LAN)
–Usually limited to short distances
–Owned by the organization that
uses it
–Usually employs solid cable
–Transmission rates tend to be high
in the range of 1Mbps to 100Mbps
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Networking Essentials
Local Area Network
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Networking Essentials
• Wide Area Network (WAN)
– Usually owned by major telephone companies
– Cover extremely large areas
– Most common WAN protocol is TCP/IP
(common for internet)
– Transmission rates are usually slower than
LAN or MAN rates (2400bps to 128Kbps)
– Technology such as ATM is improving data
transmission rates
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Networking Essentials
Wide Area Network
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Networking Essentials
• Network Components
–Network Interface Card (NIC)
• Usually found in the form of an
expansion card
• Can have multiple connector types
• Can be integrated into the motherboard
• Can be 8-bit, 16-bit ISA, VLBus or PCI
• Is used to connect the computer or PC
to the network
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Networking Essentials
• Network Components (cont.)
–Network cable
• Coaxial cable
• Thinnet (10Base-2) and Thicknet
(10Base-5)
• RG-59 used in broadband networks to
support video and data
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• Twisted pair
–Is used by dial-up modems for dial up
connection to the internet
–Unshielded and Shielded twisted pair
(UTP and STP)
–Category 1 to 6
• Fiber optic
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Networking Essentials
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Network Protocols
TCP/IP
– Transmission Control Protocol/Internet
Protocol
– The most widely used protocol suite in the
world
– Most major NOSs support the use of TCP/IP
– Originally designed for WAN use
– Routable protocol that offers true
internetworking and interoperability between
disparate NOSs
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Common Topologies
• Bus Topology
– Computers in the network are connected to a
single cable
– Main cable is called the backbone
– Signals from computers travel in both
directions
– Cable must be properly terminated at both
ends
– Only a single computer can transmit a signal
at any given time
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Common Topologies
Bus Topology
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Common Topologies
• Bus Topology
–Advantages
• Easy to apply and maintain
• Requires minimal amount of cabling
• Easy to extend by adding cable or
adding repeaters
• Can be extended with the addition of
hubs connected to the bus
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Common Topologies
• Bus Topology
– Disadvantages
• The speed of the network is directly related to
the number of computers connected to the
bus
• Damage to the cable at any location may bring
down the entire network
• The network usually has to be taken down to
add additional computers
• It may be difficult to locate a break or short in
the cable without specialized equipment
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Common Topologies
• Star Topology
– All computers are connected to a central
device called a hub
– Each signal is initially sent to the central
hub and then either out to all computers
(broadcast star network) or to the
recipient computer (switched star
network)
– Several star networks can be linked
together
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Common
Topologies
Star Topology
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Common Topologies
• Star Topology
– Advantages
• Easy to expand
• If one computer fails or one cable
connecting a computer fails, the rest of the
network stays up
• Hubs can support different types of cable
• UTP is the least expensive type of cable
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Common Topologies
• Star Topology
– Disadvantages
• Failure of the central hub results in failure of the
entire network
• Separate cables are required to connect each
workstation to a hub
• The initial cost of the equipment is more than with
a straight bus topology due to the added expense
of the hubs and running separate cables to each
computer
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Common Topologies
• Ring Topology
– All computers in the network are joined in a logical
ring
– The actual appearance may look like the star
topology
– The central network device, called an MAU, has a
loop inside of it, which creates the ring
– utilises token-ring to transmit data around the
network. If a token is free of data a transmitting
computer grabs it to send data by it and on the
receiving end the data is removed and free token
passed on to the network
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Common Topologies
• Ring Topology
– Advantages
• Ring networks handle collisions more efficiently
than bus networks
• No single computer can end up using the network
all the time. This is theoretically possible in the bus
topology.
• It is faster than the star topology
• Can be very long because each computer
reinforces the message
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Common Topologies
• Ring Topology
– Disadvantages
• On a physical ring network, you must down the
entire network to add or remove computers
• On a physical ring network, if a computer goes
down the entire network may go down
• It may not be easy to locate a faulty computer or
device on the physical ring network
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Common Topologies
Ring Topology
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Connectivity Within Networks
• Hubs
– Hubs can be used to connect networks but
are more commonly used to extend a network
– Most hubs will simply rebroadcast signals to
all ports
– Intelligent hubs rebroadcast signals only to
the actual destination port
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Connectivity Within Networks
• Repeaters
–Amplify signals on networks
–Most commonly used to increase
the length of the network backbone
–Normally signals should not pass
through more than two repeaters
before reaching their destination
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Connectivity Within Networks
• Bridges
– Selectively sends signals from one
segment to the other
– Can filter signals based on the protocol
type
– Transparent bridges contain the addresses
of each computer and calculate the
shortest route to the destination computer
– Source-routing bridges—sender
determines the proper route
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Connectivity Between Networks
• Routers
–Connect independent networks
–Dynamic and static routers
–Distance-vector routing
• Each router sends its table to all other
routers at regular intervals
–Link-state routing
• Instead of sending the entire table,
only the changes are sent
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Connectivity Between Networks
•Gateways
• Provides all the connectivity, and even
greater functionality of routers and bridges
• usually resides on a dedicated computer
and acts as a translator between two
completely dissimilar systems or
applications
• Are slower than bridges or routers
• Also provide access to special services
such as e-mail or fax functions
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Maintaining and
Troubleshooting Networks
• Reduced
bandwidth
• Loss of data
• Slow loading of
programs and
files
• Unauthorized
software
• Traffic overloads
• Common mode
failures
• Network security
violations
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Summary
•A network provides connections, communications,
and services.
•Networks are either peer-to-peer or server-based.
•Network topology types are star, bus, and ring.
•A NIC connects the computer to the network.
•Network cable types are twisted-pair, coaxial, and
fiberoptic.
•A network protocol provides the rules for network
communications.
•Networks can be extended with repeaters,
bridges, routers, and gateways.
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