Transcript Protocols

Chapter 6
Telecommunications
and Networks
© Paradigm Publishing Inc.
6-1
Presentation Overview
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The Evolution of Networking
Data Transmission Characteristics
Communications Media
Network Classifications
Network Topologies
Network Hardware
Network Software
Communications Software and Protocols
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The Evolution of Networking
Telecommunications,
combined use of
computer hardware
and communications
software for sending
and receiving
information over
communications
media, enables
computer users
throughout the
world to
communicate.
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Data Transmission
Characteristics
What are the characteristics of transmitted data?
– Bandwidth – number of bits that can be transferred
per second over a given medium
– Analog signals – continuous waves transmitted
over a medium at a certain frequency range
– Digital signals send data in the form of bits
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Data Transmission
Characteristics
Bandwidth
– number of bits that can be transmitted per second
– terms for measuring bandwidth
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Data Transmission
Characteristics
Analog and Digital Transmission
– Modulate – sending modem changes digital signal
into analog signal
– Demodulate – receiving modem changes analog
signal back into digital signal
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Data Transmission
Characteristics
Translating digital signals to analog signals
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Data Transmission Characteristics
Internal modem – electronic
board plugged into a slot on a
computer’s motherboard
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External modem – stand-alone
device connected by cable to a
computer
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Data Transmission
Characteristics
Parallel and Serial Transmission
– Serial transmission sends 1 byte plus the parity
bit one bit after another in a continuous line.
– Parallel transmission sends 8 bits plus a parity bit
at the same time over 9 separate paths.
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Communications Media
Coaxial cable
is an
insulated
center
wire
grounded
by a shield of
braided wire.
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Communications Media
Twisted-pair
cable is
two parallel
copper wires,
individually
wrapped in
plastic and
bound by
another
plastic casing.
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Communications Media
Fiber-optic
cable
transmits
beams of
light through
a glass or
plastic core.
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Communications Media
Wired Communications Media
– Integrated Services Digital Network (ISDN)
Lines are used to dial into the Internet and receive
information at high speeds.
– Digital Subscriber Lines (DSL) use existing
phone lines and new switched connections to get
faster speeds than traditional phone access.
– T Lines are digital, high-speed, long-distance lines
capable of carrying signals across the line.
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Communications Media
Microwave systems transmit data through the atmosphere
from one microwave station to another.
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Communications Media
Communications
satellite is a solarpowered, electronic
device with specialized
radios (transponders)
for receiving signals
from ground
transmission stations.
A satellite receives
transmitted signals,
amplifies them, and
retransmits them to
other ground locations.
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Communications Media
Infrared
technology
allows data as
infrared light
waves
to be
transmitted
from a special
port in a
computer to
an infrared
sensor in a
printer.
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Communications Media
Wireless Communications Media
– Bluetooth technology offers short-range
connectivity with other Bluetooth devices.
– Devices form a small, temporary network that
can transmit voice and data.
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Communications
Media
home
Wi-Fi-enabled devices use
a broadband Internet
connection through a
wireless access point.
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Communications Media
Signals sent by cell phones are transmitted and received from cell
to cell until they reach their destination.
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Network Classifications
Networking paths allow networked client computers to send
information to a server, which relays information back to the
computer or to another on the network. Fax machines and printers
are shared resources. The file server accesses a shared hard disk.
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Network Classifications
Local area
network
(LAN) is
a private
network
using a file
server
that houses
all network
resources.
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Network Classifications
Wide area
network
(WAN)
spans a large
geographical
area
connecting
two or more
LANs.
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Network Classifications
An intranet
is a network
within an
organization
to serve
internal
users.
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Network Hardware
Network Interface Card (NIC)
connects each client computer to a network
A network interface
card (NIC) is used for
wired connections in a
desktop PC.
A wireless NIC allows
notebook computers to
use Wi-Fi hotspots.
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Network Classifications
In peer-to-peer architecture, computers act as both client and server.
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Network Topologies
Bus Topology
– all computers linked to a single line of cable (bus)
– all communications travel length of bus
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Network Topologies
Ring Topology has no hub, and each computer is connected to two
other computers in a circular path.
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Network Topologies
Star Topology links multiple computers and devices to a
central hub in a configuration resembling a star.
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Network Hardware
Hubs, Switches, Routers
devices that links computers in a network
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Network Hardware
A gateway is a combination of hardware and software that allows
dissimilar networks to communicate.
A bridge is a combination of hardware and software that enables
devices on similar networks to communicate
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Network Software
Network Operating Systems (NOS)
– controls flow of messages from client computers and
provides services such as file access and printing
– systems such as Linux and Mac OS have networking
functions built in
– Windows systems include Novell’s Netware or
Windows Server software to enhance the basic
operating system
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Communications Software
Communication software programs can be used to
– access and use services of an Internet service provider
for e-mail and Web browsers
– send and receive information to and from computers
through LAN and WAN networks
– send and receive faxes
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Protocols
What are protocols?
– Protocols are rules and procedures for exchanging
information among computers on a network.
– Computers involved must have the same settings and
follow the same standards.
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Communications Software and
Protocols
With simplex data
transmission, data
flows only one way.
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With half-duplex
data transmission,
data flows in both
directions but only
in one direction at
a time.
With full-duplex
data transmission,
data flows in both
directions at the
same time.
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Communications Software and
Protocols
Synchronous Transmission Protocols
blocks of bytes are wrapped in a start and stop byte
called a synch byte.
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Communications Software and
Protocols
Asynchronous Transmission Protocols
each byte of data is surrounded by control bits:
• start bit signals the beginning of a character
• stop bit signals the end
• parity bit
checks for
errors
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Communications Software and
Protocols
Local Area Network (LAN) Protocols
– Ethernet protocol specifies how the network is
set up, how devices communicate, how problems
are identified and corrected, and how components
are connected.
– Token ring protocol sends an electronic signal
(token) around the ring quickly.
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Communications Software and
Protocols
TCP/IP
Transfer Control Protocol / Internet Protocol
physical media
receiving
layer
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user
sending
protocol
user
stack
physical media
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Communications Software and
Protocols
Circuit Switching / Packet Switching
Circuit switching
Packet switching
Networks create an end-  Outgoing messages are
to-end circuit between the
divided into fixed-size
sending and receiving
data units called packets.
computers.
 Packets are numbered
Electronic switches
and addressed to the
establish and maintain the
receiving computer.
connection.
 Routers examine the
packets and send them to
their destination.
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Packet Switching
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Communications Software and
Protocols
Internet and Web Protocols
– Hypertext Transfer Protocol (HTTP) is used on
the World Wide Web.
• sends small blocks (packets) of data along the
Internet to their destinations
– File Transfer Protocol (FTP) transmits and
receives large files over the Internet.
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Communications Software and
Protocols
Electronic Mail Protocols
– Post Office Protocol (POP) server allows the
recipient to retrieve the message.
– Simple Mail Transfer Protocol (SMTP)
determines how a message will be routed through
the Internet and then sends the message.
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Communications Software and
Protocols
Variations of the 802.11 protocol
802.11 n
2007
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600 Mbps
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On the Horizon
Based on the information presented in this
chapter and your own experience, what do
you think is on the horizon?
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