Transcript Brian Kovar - Kansas State University

TELECOMMUNICATIONS
and
NETWORKS
All Organizations Need to Share and
Communicate Information...
• Externally with other organizations
• Internally among employees.
- the electronic movement of
information over public or private networks
- a communications, data exchange, and
resource-sharing system created by
, or protocols, so
that they can work together.
Benefits of a NETWORK
1. The ability
(
is the most
communications)
2. The ability to share
–I
– Software
– Peripheral devices
–P
with other people
of network
Ways different types of networks are
differentiated
• Size and Proximity of the network
– LAN versus WAN
• Architecture
– Peer-to-Peer versus Client/Server
• Protocols Used
– Ethernet for LAN
– Transmission Control Protocol/Internet Protocol (TCP/IP)
• Topology
– Bus, Star, Ring, Hybrid, Wireless
• Media
– Coaxial, Twisted-pair, Fiber-optic, Wireless media
Network Proximity
• L
Network--Connects computers in
relatively
• W
Networks-- Connects
computers that may be dispersed
among a number of buildings, or
even in different cities.
• Internet--International Network
of Networks.
WAN
Types of
LANs
P
Each user can share
their computer’s
resources with other
LAN users
C
Only resources on
specific computers
called “servers”
can be shared
Peer-to-Peer Networks
• Peer-to-peer (P2P)
network - any
network
and in which
computers in the
network
to the public
files located on all
other workstations
Peer-to-Peer LAN Advantages
• Control is distributed to the LAN users
– Users who own data have control over who accesses it
• Inexpensive and easy to install
– You just need
• A
• A network operating system on both
computers,
(any version of
since 95).
• Network
• Network resources are distributed
– A disaster on one user’s computer
doesn’t destroy all the data on the network
Peer-to-Peer LAN Disadvantages
• Control is distributed to the LAN users
– No one person or group can know what resources are
available.
– No one person or group is
• Performance is poor
– Since the computers share resources and some computers
can even access the hard drives of other computers, the
result is that
– The performance of a PC also slows down when someone
on the network accesses it.
– As a result, peer-to-peer networks are
Client/Server Networks
• Client - a computer that is designed to
from a server
• Server - a computer that is dedicated to providing
information in response to external requests
• Client/server network - model for applications in
which the
takes place on a
, while the
is handled by the
The Client/Server Model
Data Management
Business Logic
Presentation
Storage and management of the data
needed by the application
Actual business rules implemented
The
to the application
Client/Server Model: A Business
View
The different Client/server implementations differ
according to:
1. Where the processing for the
2. Where the processing of
3. Where the
(DBMS) and
occurs
are located
Flexible Applications
Server
Client
Data Management
Business
Presentation
Logic
Business Logic
Presentation
Any Combination is Possible
Client
Data Management
Business Logic
Design Server
Presentation
Data Management
Business Logic
Production Server
Client/Server Advantages
• Application can be structured to match organizational
requirements since it is both
– Can change the implementation of this model as the organization
changes in size since the Client/Server model provides the
to whatever
is
• Data access is
regardless of where the data is stored.
• Separate programs are more easily maintained and can be
reused.
• One
easier to
for all of the
and
Client/Server LAN Disadvantages
• All shared resources reside on computers
call “servers”
– If a disaster occurs on the server all the data is in
jeopardy
– If the server malfunctions,
• Expensive
– Usually require expensive hardware and extra staff to
manage
– Only
of client/server costs are tied up in
– The remaining
is in the form of
IT professionals and knowledge workers.
- both
Client/Server Networks
• Network operating system (NOS) - the operating system that runs a
network, steering information between computers and managing
security and users
– Major client/server NOSs are Windows NT, Windows 2000,
Novell NetWare, Linux, and Unix
• P
- occurs when the sending computer divides a
message into a number of efficiently sized units called packets, each
of which contains the address of the destination computer
• Router
– Used to
– Can also “sit”
(serving as a
).
– An intelligent connecting device that examines each packet of data it receives
and then decides which way to send it onward toward its destination
Network Data Transfer Process
• Network operating system on the source machine
to be sent into segments of predetermined length called
• Network operating system on the source uses a
communications protocol to
• Network Operating System on the source sends packets
over the network.
• Packets are routed as necessary through the network
depending on the transmission mediums, transmission
signal characteristics and access control methods.
• Network Operating system on the destination receives
packets over the network.
• Network Operating system on the destination
by looking
at the communication protocol information. Requests
retransmission of any missing data.
Connecting Networks
The connection between a LAN and a larger
network is usually accomplished using a
device called a
LAN
WAN or Backbone
Router
LAN
Routers are responsible
for
that
messages take from the sending
computer to the destination computer.
Router
Once a network is linked
to a
, it
becomes part of the
Internet community.
Backbone is
usually a type
of network that has
WANs
High Speed Backbone
Wide Area Network
Packet Switched Network
Data is packaged in
for transmission. R
R
R
Each packet follows
through
the network.
R
R
R
R
R
R
R
R
R
R
PROTOCOLS
• Protocol - a
as well as the
that specifies the
during transmission
• Following a certain
for interoperability
, allows
– Interoperability - the capability of two or more computer
systems to share data and resources, even though they are
made by different manufacturers
• Two primary communications protocols are TCP/IP
and Ethernet
– TCP/IP is used for
– Ethernet is used by computers in a
to communicate
Ethernet
• Ethernet - a physical and data layer
technology for LAN networking
Ethernet
• Defines the
LAN.
standards used in a
• Used to describe the
–
–
–
–
W
(Co-axial, twisted-pair, fiber-optic)
How bits are physically transmitted using those media
Access control rules
Data transmission speeds
• Details
the principle of
and works on
and
• Helps insure the compatibility of different devices so
that many people can attach to a common cable.
Transmission Control Protocol/
Internet Protocol
• Transmission Control Protocol/Internet
Protocol (TCP/IP) - provides the technical
as well as
for large numbers of private network
• The TCP/IP protocol suite is made up of over
protocols.
– The two
– TCP provides for
– IP provides the
mechanism
are TCP and IP
TRANSMISSION CONTROL
PROTOCOL / INTERNET PROTOCOL
(TCP / IP)
• Allows computers to
their
regardless of
or hardware.
• Transmission Control Protocol
– Breaks information into data packets
– Reassembles packets when received
– Checks for lost packets
• Internet Protocol
– Each computer given a unique IP address
– Used to
– 209.1.144.212
TCP/IP’s four-layer reference model
• The
– F
– Simple
layer allows users and applications to access
protocol (FTP)
protocol (SMTP)
– T
provides terminal emulation that allows a “
terminal with
” to be able to connect to a
host computer (which will control everything).
– H
protocol (HTTP)
– Simple network management Protocol (SNMP)
TCP/IP’s four-layer reference model
• The
• The
• The
layer handles
layer handles the packets (
, etc.)
layer details how
through the networking
is
How Does the Internet Work??
http://www.howstuffworks.com/web-server.htm
#1
#2 Browser communicates with
209.1.144.212
to get
#3 Browser
connects to
specific server,
uses GET request
to ask for file you
wish to see.
#4 Server sends
HTML text to
your browser.
HTML tags are
read and page
displayed.
Network Topology
The
computers in a network.
Bus
Ring
Star
Mesh
Hybrid
Wireless
of
Bus
Topology
• All
computers
are connected
/cable.
• One device transmits a communications signal,
which is broadcast
to the
entire network
• Most
LAN topology. Relatively
Ring Topology
• All devices
connected to one
channel in the form
of a closed loop (ring). Each device is connected
directly to two other devices.
• All messages
in one direction.
• Relatively
and
, but they
offer high bandwidth and can span large distances.
• Used primarily in
ring software.
that use token
Star Topology
• All devices are
, called a hub.
The hub
. All network traffic
the hub.
• Relatively easy to install and manage.
• B
can occur because
of the
must
through the
, and if the hub goes
down, the entire network is down.
Hybrid Topology
• Groups of star-configured workstations that are
connected to a liner bus cable, combining
characteristics of bus and star topologies.
– Often
Wireless Topology
• Computers are connected by
to a
wireless access point (which is directly connected
to a wired LAN)
– Must be within a certain number of feet from the access
point to
communicate
wirelessly
(
depending on
the technology
being used)
Network Transmission Media
• Refers to the various types of media used to
– Wire media (guided)
• Transmission material manufactured so that signals will be
and will behave .
• Three most commonly used types include:
– Twisted-pair wiring
– Coaxial cable
– Fiber optic (or optical fiber)
– Wireless media (unguided)
Network Communications Media
Network Communications Media
• C
cable - a betterconstructed version
of the phone twistedpair cable.
Twisted Pair Wire
Network Communications Media
Coaxial
Fiber-Optic
Cable
Cable
• Wireless communications
(radio waves, microwaves,
infrared) media radiate
information into the air, either
very narrowly beamed or in
many directions like ripples
from a pebble tossed into a
pond.
Business Networks
• You can build your own
wired network or you
can
from a
national provider.
• Virtual private network
(VPN) - a way to use the
telecommunication
infrastructure (e.g.,
) to provide secure
access to an organization’s network
–T
software is used to create a
connection between two different servers (
).
– Data packets are
Telecommunications Methods
• Data
are generally expressed in
thousands or millions of bits per second (kbps/mbps)
• Phone Lines: use a
:
but very
. Handles only analog signals. 28.8-56 kbps
• D
(
): regular
divided into voice (analog) and information (digital
channels). Always-on connection. Can make phone
calls while online.
• C
: Operates over
Provides a constant connection to the Internet,
although its speed depends on how many users (such
as your neighbors) are online.
Researchers explore scrapping and
rebuilding the Internet
• In order to address the problems that were not
envisioned when the Internet was initially created,
some are suggesting rebuilding the Internet using a
approach.
• S
– The Internet was designed to be open and flexible and all
users were assumed to be trustworthy. Internet protocols
were not designed to authenticate users and their data.
Firewalls and spam filters are now being used to control
security.
– Solution: data not passed along until
• Mobility
– Initially, computers were fixed in location so IP addresses were assigned to
devices in a fixed location. Wireless mobile computing is presenting challenges
related to data flow.
– Solution: R
so that addresses are based on the device,
rather than the location.
• Ubiquity (called
in our class notes)
– When the Internet was first designed, there were relatively few computers
connected to it. The addressing system has become strained due to the
proliferation of personal computers and mobile devices.
– Solution: assign
and have those same
devices connected to an addressed gateway, which is then connected to routers
and the rest of the Internet
• Result is fewer devices to keep track of and improved efficiency.
• These changes may happen over the next 10-15 years. They
(expected to cost
as computer hardware and software and Internet
infrastructure are replaced)
The End
The slides that follow this slide contain
additional details related to the material found
in some of your earlier slides. It is HIGHLY
RECOMMENDED THAT YOU STUDY
THESE ADDITIONAL SLIDES because they
reinforce other concepts that you have already
seen (and that you might see on an upcoming
exam)
Network Communications
• Network Card--Allows a PC
to communicate with the network.
• Digital Signal--Discrete signal, series of ons and
offs. Computer thinks in terms of zeros (off)and
ones (on). Very abrupt.
• Analog Signal--Continuous wave-like
communication. Readings can fall within a
range: temperature, humidity, air pressure, radio
signals, phone signals, TV signals, electricity.
Don’t we have a problem??
• Humans and their devices think in terms of
analog: continuous waves.
• Computers think in terms of digital signals:
abrupt stops and starts.
MODEM: Modulator/Demodulator
converts the digital signals of your computer
into an analog form that can be transmitted
over a telephone line and then converts the
analog signal back to digital signals at the
other end of the transmission.
Modems
Telecommunications Methods
Network Communications Media
•
•
•
•
•
•
Twisted Pair Wire
Coaxial Cable
Fiber Optical Cable (Optical Fiber)
Infrared
Microwave
Cellular
transmissions
Twisted Pair Wire
• Two or more strands of copper wire twisted
together, covered by insulation.
• Used for direct connections over short distances
in LANs
• Type of Signal Carries an electrical signal
• Other Characteristics Cheap, but slow. Not
used very frequently anymore. Does not protect
well against electrical interference
• Other Uses Telephone lines inside your home
Coaxial Cable
• Used for direct connections
over short distances in LANs but
over a slightly larger distance than twisted pair.
• Type of Signal Carries an electrical signal
• Other Characteristics Better signal quality and
more capabilities than twisted pair. More
reliable.
• Other Uses Cable TV
Optical Fiber / Fiber Optics
• Used for longer distance connections in WANs
that will carry large amounts of data.
• Type of Signal Glass fibers transmit information
as pulses of light.
• Other Characteristics Faster and more
expensive than TP or Coax.
• Other Uses High speed, cross country telephone
lines. Also being installed in cities as an
infrastructure for a wide variety of
communications uses.
Fiber-Optic
Cable
• Fiber-optic Cable
– Many extremely
thin strands of glass
or plastic bound
together in a
sheathing which
transmits signals
with light beams.
Can be used for
voice, data, and
video.
Infrared
• Used for Wireless, short range LAN
connections
• Type of Signal Infrared beam of light.
Requires line of sight communication. Uses a
red light that you can’t see to transmit info.
• Other Characteristics Advantage is lack of
wires connecting devices, portability.
• Other Uses many types of remote controls,
wireless keyboards and mice.
Microwave
• Used for long range WAN connections.
• Other Characteristics Require line-of-sight
connection. Signal can be boosted through the use
of repeater devices located between transmitter and
receiver.
• Other Uses:
Used by satellites,
cable companies,
cellular phones,
broadcast radio.
The Internet
• First developed by the US Department of Defense in 1969. Over
time, international connections were made, and the Internet really took
off during the early 1990s when the technology behind web pages was
developed and corporate users were given access to it, and the Internet
has evolved into its present form.
• The Internet and the World Wide Web are not the same thing. There
are many different resources and services on the Internet, and the
World Wide Web is just one of the resources found on the Internet.
• Initial Internet communications were text-only, but now Internet
communications can also be in the form of audio, video, and graphics
• Two types of computers on the Internet
– Clients
– Servers
• Web Servers
• Mail Servers
FTP Servers (used to upload and download files
Internet Relay Chat (IRC) Servers
Connecting to the Internet
• Dial up (dial in) using the telephone lines and a
modem.
• Constant Connections
– Wired (LAN): Local Area Network: network card required
– Cable modems and DSL (Digital Subscriber Line)
– Wireless Network (wireless LAN)
• PCs and laptop computers could access the Internet without
relying on physical wiring. Wireless Access Point/Base Station
Required
• Use wireless phones to retrieve email, access the Internet, or a
corporate database.
• Many of the buildings on campus are in wireless zones.
World Wide Web
• Hypertext Markup Language (HTML)
– Hypertext is used to connect or link documents together
: hyperlinks.
• Web browsers are the software capable of
understanding HTML files and HTML coding.
– Internet Explorer: approximately 89% market share
– Safari: found on Macs: faster than IE, can read web pages aloud
– The Netscape Family of Browsers
• Netscape: dominant in web’s early days, before IE
• Mozilla: 2% market share
• FireFox: 7% market share: more stable and secure than IE, can be
found on computers running Windows, Linux or the Macintosh operating
system.