Download Data Communications for Business Students

Data
Communications
Networking and Telecommunications
topics for the Business Student
What is the difference between
telecommunications and a network?
• TELECOMMUNICATIONS - the electronic movement of
information over public or private networks
• NETWORK – two or more computers connected together using
standards/protocols so that they can work together.
What are the benefits of a network?
1. The ability to communicate with others
email is the most popular form of network communications
2. The ability to share
Data and Information
Peripheral devices and other resources
Software
Processing power
What is the most basic way to
differentiate networks? By Proximity
• Local Area Network (LAN) --Connects
computers in relatively close proximity
• Wide Area Networks (WAN)
-- Connects computers dispersed
among a number of buildings, or
even in different cities.
Biggest WAN = the Internet
• Personal Area Network (PAN)
--Wirelessly connecting small
personal devices, really short distance
Wireless Topology
• Computers are connected by radio waves 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
(35-300 feet
depending on
the technology
being used)
Comparing Wired to Wireless
Wired Network
Wireless Network
• Communications occur using • Communication occurs using radio
a wired media.
signals and line-of-sight base station.
Limited by obstructions.
• Faster
• Slower: rarely reaches max speeds that
• Tends to be more secure could be available
• Limited location and hard to
move around (bound to the
wire). Limited by walls,
furniture, infrastructure.
• Should be able to easily
handle multiple users
•
Inherently insecure: security features not
turned on: easier to have data packets
captured.
• Mobile. Relatively easy to connect to. Must
be within range of hotspot (base station)
•
• Fixed work location
• All of the work tools that you •
need probably are available
One person could monopolize the base
station with huge data transfers: slowness for
everyone.
Computer can be set up where needed, but
work tools needed may not be available when
needed.
Bluetooth vs Wi-Fi (802.11)
• Business networks use 802.11 (Wi-Fi/Wireless Fidelity) while
individuals might create their own short range network using
Bluetooth
Bluetooth
• Allows for wireless communications within a limited distance: 2
megabits per second, up to 30 feet.
• Less expensive than Wi-Fi chips, consume less power, easier to
build into small devices than run on batteries such as cell phones,
palm-top computers, and other PDAs.
• Called a “personal area network” (PAN) technology.
802.11
802.11b
Provides transmission speeds of up to 11 mbps, 300 feet inside, 800 feet outside.
802.11g
Provides transmission speeds of up to 54 mbps, at a 35 foot indoor range
802.11a
Uses a different radio frequency than standards b & g and other electronic devices
(kinda like taking a less crowded route: it will be faster since no one is using it)
802.11n
Still being developed: expected to provide transmission speeds over 100 mbps using
MIMO technology (multiple wireless signals and antennas):
Walt Mossberg Chief Technology columnist for the
WallStreet Journal
Q: I’m wondering about wireless specs for a
laptop. I suspect the “n” version of Wi-Fi is best
but “g” is adequate. Any advice would be
appreciated.
A. It depends on how and where you intend to use
your laptop’s wireless connectivity. The “n”
version of Wi-Fi can be much faster than “g” and
can have much greater range. However, the speed
difference won’t matter much if your sole use is
connecting to the Internet with a typical home or
public hotspot service, since the maximum speed
of these services is almost always well below “g”
and “n” capabilities. But if you are streaming
video at home or backing up large files wirelessly
among computers and networked hard disks on a
home network, you’d be much better off with “n,”
assuming all devices involved support it. The
same goes for range. In a small apartment, it likely
won’t matter. In a large home, it could.
802.11 wireless standards explained
http://compnetworking.about.com/cs/wireless80211/a/aa80211standard.htm
http://info.cba.ksu.edu/bkovar/wireless.htm
What are Protocols and what is the
difference between them?
• Protocol - a standard that specifies the format of data
as well as the rules to be followed during transmission
• Following a certain protocol/standard/set of rules,
allows for interoperability
– Interoperability - the capability of two or more computer
systems to share data and resources, even though they are
made by different manufacturers using perhaps different
technologies.
• Two primary communications protocols are TCP/IP
and Ethernet
– TCP/IP is used for Internet communications
– Ethernet is used by computers in a LAN to communicate
Ethernet
• Ethernet - a physical and data layer
technology for LAN networking
Ethernet
• Defines the wiring and signaling standards used in a
LAN.
• Used to describe the hardware layer of a LAN
–
–
–
–
Wiring Technology Used (Co-axial, twisted-pair, fiber-optic)
How bits are physically transmitted using those media
Access control rules
Data transmission speeds
• Details multiple user communications and works on
the principle of collision avoidance and collision
detection.
• 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
foundation for the public Internet as well as for
large numbers of private network
• The TCP/IP protocol suite is made up of over
100 different protocols.
– The two most important are TCP and IP
– TCP provides for data transport functions
– IP provides the addressing and routing
mechanism
TRANSMISSION CONTROL
PROTOCOL / INTERNET PROTOCOL
(TCP / IP)
• Allows computers to exchange messages regardless of
their operating system 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 identify a specific computer
– 209.1.144.212
TCP/IP’s four-layer reference model
• The application layer allows users and applications to access
network services
– File transfer protocol (FTP)
– Simple mail transfer protocol (SMTP)
– Telnet provides terminal emulation that allows a “dumb terminal with no
processing capability” to be able to connect to a host computer (which
will control everything).
– Hypertext transfer protocol (HTTP)
– Simple network management Protocol (SNMP)
TCP/IP’s four-layer reference model
• The Transport layer handles end-to-end packet
transportation.
• The Internet layer handles the packets (creation,
labeling and addressing, etc.)
• The Network Interface layer details how data is
physically sent through the networking hardware.
How Does the Internet Work??
http://www.howstuffworks.com/web-server.htm
#1 Browser breaks URL into 3 parts
209.1.144.212
#2 Browser communicates with name server to get IP address
#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.
What is a VPN?
• You can build your own
wired network or you
can lease lines from a
national provider.
• Virtual private network
(VPN) - a way to use the public telecommunication
infrastructure (e.g., Internet) to provide secure
access to an organization’s network
– Tunneling software is used to create a private connection
between two different servers or between a server and
individual computers (made when needed and terminated
when transmission is completed).
– Data packets are encrypted for security.
Network Data Transfer Process: How does it happen?
• Network operating system at the source divides the message to be sent
into segments of predetermined length called packets.
• Network operating system at the source uses a communications
protocol to label and address each packet.
• Network Operating System at 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 at the destination receives packets over the
network.
• Network Operating system at the destination identifies and
reassembles the packets of the message by looking at the
communication protocol information. Requests retransmission of any
missing data.
Connecting
Networks
LAN
The connection between a LAN and a larger
network is usually accomplished using a
device called a router. Routers are used to
connect computers in a network. They also “sit”
between your network and other networks
(serving as a gatekeeper both into and out of your
network). They are intelligent connecting
devices that examine each packet of data it
receives and then decides which way to send it
onward toward its destination
WAN or Backbone
Router
LAN
Routers are responsible
for determining the path that
messages take from the sending
computer to the destination computer.
Router
Wide Area Network
Packetswitching occurs
Packet Switched Network
Data is packaged in
packets for transmission. R
R
R
R
R
R
R
R
R
R
R
R
Each packet follows
it’s own path through
the network.
R
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.
Once a network is linked
to a backbone, it becomes
part of the Internet
community.
Backbone is
usually a type
of network that has
a larger size limit
and is relatively high
speed.
WANs
High Speed Backbone
Internet Backbone on the Ocean Floor
What are the
different types of
LANs?
Peer-to-Peer
Each user can share a
portion their
computer’s hard drive
with other LAN users
Client/Server
Only resources on
specific computers
called “servers”
can be shared
Client/Server Networks
• Client - a computer that is designed to request
information 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 bulk of the back-end processing takes
place on a server, while the front-end processing is
handled by the clients
The Client/Server Model
Data Management
Business Logic
Presentation
Storage and management of the data
needed by the application (the database)
Actual business rules implemented
as software (how you implement your
software to get the job done and what
are the processing steps)
The user’s interface to the application
(how the application appears to the
user, including the formatting)
Client/Server Model: A Business
View
The different Client/server implementations differ
according to:
1. Where the processing for the presentation of
information occurs
2. Where the processing of logic or business rules occurs
3. Where the data management component (DBMS) and
information (database) 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 flexible and scalable
– Can change the implementation of this model as the organization
changes in size since the Client/Server model provides the
flexibility to mold information systems to whatever business
model is most appropriate for an organization.
• Data access is transparent to the user regardless of where
the data is stored.
• Separate programs are more easily maintained and can be
reused.
• One central location to go to for all of the sharing and easier
to control the entire network.
Client/Server 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, no one can use the network
• Expensive
– Usually require expensive hardware and extra staff to
manage
– Only 30% of client/server costs are tied up in hardware
and software.
– The remaining 70% is in the form of labor - both IT
professionals and knowledge workers.
Current Events in
Information Technology
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
“clean slate” approach.
• Security
– 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 authenticated
• 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: Reconfigure the IP address system so that addresses are based on the
device, rather than the location.
• Ubiquity (also called Pervasive Computing)
– 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 addresses to fewer devices 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 will not
be cheap (expected to cost millions and billions of dollars as computer
hardware and software and Internet infrastructure are replaced)