Download 11. Building Information Systems

Chapter
8
TELECOMMUNICATIONS
AND
NETWORKS
** Modified **
8.1
© 2004 by Prentice Hall
General Block Diagram
of a Communication System
8.2
© 2004 by Prentice Hall
SEE Handout OF
FILE TRANSFER
• SOURCE and TRANSMISTTER are
the same
• TRANSMISSION SYSTEM is the
telephone lines
• DESTINATION and RECEIVER are the
same
8.3
© 2004 by Prentice Hall
Key Communications FUNCTIONS
• Transmission System Utilization
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•
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•
8.4
Interfacing
Signal Generation
Synchronization
Exchange Management
Flow Control
© 2004 by Prentice Hall
Key Communications FUNCTIONS
Example……
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Multiplexer: Enables single communication channel to
carry data transmissions
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8.5
Computer 1:..
Computer 2:..
Computer 3:…
Computer 4:…
Computer 5:..
Computer 6:…
123456 123456 123456
© 2004 by Prentice Hall
Key Communications FUNCTIONS
• Error detection and correction
• Addressing and routing
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•
•
•
8.6
Recovery
Message formatting
Security
Network Management
© 2004 by Prentice Hall
Transmission System Utilization
• Refers to the need to be efficient with the
network
• Especially the bandwidth because:
– The Transmission line is (usually) shared
among many users
– Capacity is allocated to many users
• “Congestion” means the network is too
busy
8.7
© 2004 by Prentice Hall
Error detection and correction
• Some applications require NO
ERRORS
– File transfers, Transactions (TPS)
• Other application can tolerate some
ERRORS
– Video, voice, streaming music
8.8
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Addressing and routing
• Messages must get to their
Destination
• And only their destination (unless
the message is broadcasted)
• Devices on a network must have a
UNIQUE Address
8.9
© 2004 by Prentice Hall
Networking
• Point to point communication not
usually practical
– Devices are too far apart
– Large set of devices would need
impractical number of connections
– N devices => n(n-1)/2 wires
• Solution is a communications
network
8.10
© 2004 by Prentice Hall
Simplified Network Model
8.11
© 2004 by Prentice Hall
Wide Area Networks
• Large geographical area
• Crossing public rights of way
• Rely in part on common carrier
circuits
• Alternative technologies
– Circuit switching
– Packet switching
– Frame relay (SKIP)
– Asynchronous Transfer Mode (ATM)
8.12
© 2004 by Prentice Hall
Circuit Switching
• Dedicated communications path
established for the duration of the
transmission
• e.g. telephone network
• Also called “connection oriented”
• Used for reliable transfer (no errors)
8.13
© 2004 by Prentice Hall
Packet Switching
• Data sent out of sequence
• Small chunks (packets) of data at a
time
• Packets passed from node to node
between source and destination
• Also called “connectionless”
• The Internet uses Packet Switching
8.14
© 2004 by Prentice Hall
Packet Switching
Packed-Switched Networks and Packet
Communications
Figure 8-9
8.15
© 2004 by Prentice Hall
Network services that we SKIP
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8.16
X.25
Frame Relay
ISDN
T1
Cable Modem
(no ‘lecture questions about these’
© 2004 by Prentice Hall
Asynchronous Transfer Mode
• Little overhead for error control
– Errors are checked in the end-systems
– Smaller overhead means faster trans
• Fixed packet (called cells) length
– Fixed length is faster to process
• Anything from 10Mbps to 10 Gbps
– 10 Gbps is great!
• Uses packet switching technique
8.17
© 2004 by Prentice Hall
Digital Subscriber Lines
DSL, ADSL
• Operate over existing copper lines
• Can transmit Voice, Data and Video
• Asymmetric DSL = ADSL
– Download speed 9Mbps <> upload
speed 640Kpbs
– (higher download speeds are better)
8.18
© 2004 by Prentice Hall
Local Area Networks
• Smaller scope
– Building or small campus
• Data rates much higher
• Usually broadcast systems
• Now some switched systems and
ATM are being introduced
8.19
© 2004 by Prentice Hall
Local Area Networks
• Gateway is a device that connects
two dissimilar LANs
• Router is a device that connects two
or more LANs or to a WAN
8.20
© 2004 by Prentice Hall
Local Area Networks
Network Topologies
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Star Network: All computers and other
devices are connected to a central host
computer
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Bus Network: Links a number of
computers by a single circuit
•
Ring Network: All computers are linked
by a closed loop
8.21
© 2004 by Prentice Hall
Local Area Networks
A Star Network Topology
Figure 8-5
8.22
© 2004 by Prentice Hall
Local Area Networks
A Bus Network Topology
Figure 8-6
8.23
© 2004 by Prentice Hall
Local Area Networks
A Ring Network Topology
8.24
Figure 8-7
© 2004 by Prentice Hall
COMMUNICATIONS NETWORKS
Private Branch Exchanges, Local Area Networks (LANs),
and Wide Area Networks (WANs)
Wireless LANs
8.25
•
Wi-Fi (802.11b) standard: Up to 11 Mbps,
low cost, high-speed mobile Internet
access, links work groups
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Bluetooth standard: Up to 720 Kbps,
small personal area networks
© 2004 by Prentice Hall
Local Area Networks NOS
A Local Area Network (LAN)
N O S Ar e u s u a l l y
contained within the
Operating System.
Ex: Windows 2000
Server has the NOS.
8.26
Figure 8-8
© 2004 by Prentice Hall
Protocols
• Used for communications between devices or
software programs in a communication network
• EX: Computers, routers, networks, application
programs, file formats, file transfers email, etc
• Allows two different computer entities to
communicate
– Must “speak the same language”
8.27
© 2004 by Prentice Hall
Key Elements of a Protocol
• Syntax
– Data formats (bit ordering)
– Signal levels (“high” means 1)
• Semantics
– Control information (How large)
– Error handling (checksum)
• Timing
– Speed matching (how fast)
– Sequencing (what order)
8.28
© 2004 by Prentice Hall
Protocol Architecture
• Task of communication broken up
into modules
• Each module interfaces with the
Layer above it and below
8.29
© 2004 by Prentice Hall
OSI v TCP/IP
8.30
© 2004 by Prentice Hall
SEE Handout OF
FILE TRANSFER
• Trace the transfer of a file though the
communications network with the
LAYERS in mind!
8.31
© 2004 by Prentice Hall
SEE Handout OF
FILE TRANSFER
• Trace the transfer of a file though the
communications network with the
LAYERS in mind!
8.32
© 2004 by Prentice Hall
Frequency Ranges for Communications Media and Devices
Figure 8-3
8.33
© 2004 by Prentice Hall
Other topics
THE NEXT SLIDES ARE ABOUT
OTHER IMPORTANT POINTS
Responsible for definitions only
8.34
© 2004 by Prentice Hall
Types of Signals: Analog and Digital
Analog signal
8.35
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Continuous waveform
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Passes through communications medium
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Used for voice communications
© 2004 by Prentice Hall
Types of Signals: Analog and Digital
Digital signal
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Discrete waveform
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Transmits data coded into two
discrete states as 1-bits and 0-bits
Used for data communications
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Modem
•
8.36
Translates computer’s digital
signals into analog and vice versa
© 2004 by Prentice Hall
Functions of the Modem
Figure 8-2
8.37
© 2004 by Prentice Hall
Communications Channels—Types of media
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Twisted wire: Telephone systems
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Coaxial cable: Cable television
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Fiber optics and optical networks
8.38
© 2004 by Prentice Hall
Communications Channels—Types of media
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Wireless transmission: Microwave,
Satellites, Paging systems, Cellular
telephones, Personal communication
Services, Personal digital assistants,
Mobile data networks
8.39
© 2004 by Prentice Hall
Electronic Data Interchange (EDI)
•
8.40
Direct computer-to-computer exchange
between two organizations of standard
business transaction documents
© 2004 by Prentice Hall
Electronic Data Interchange (EDI)
Figure 8-10
8.41
© 2004 by Prentice Hall
Value-Added Networks (VANs)
•
8.42
Private, multipath, data-only, third-party-managed
network
© 2004 by Prentice Hall