Topics Lesson 7
Basic Telecommunication Concepts
Telecommunication Models
Networking
Client/server Computing
Telecommunication Standards
Wireless Communications
Internet
Modems
Baud - transfer rate (bits per second)
Analog signals: continuous
Digital signals: discrete
Modulation: translating digital data to analog
Demodulation: translating analog data to digital
Modems modulate & demodulate data
Fax/Modem
telephone as well as facsimile
Modems
A typical telephone line can only accommodate
an analog signal (a continuous, curving signal)
A computer generates a digital signal
representing bits
Modem: a device that translates data from
digital to analog and analog to digital
Figure 6.8: How a Modem Works
Figure 6.3: Elements of a
Telecommunications System
Electronic Communication
Terminology
Simplex
one way (i.e. transmit, or receive)
Half Duplex
both directions (one-at-a-time)
Full Duplex
both directions at the same time
Baud vs. bit/s (bps)
Electronic Communication Modes
Communications Protocols
Handshaking
Redundancy
CRC – Cyclic Redundancy Checking
Multiplexers
Multiplexers (a.k.a. “mux”): device that allows
several telecommunications signals to be
transmitted over a single communications
medium at the same time
Demultiplexer (“demux”)
http://en.wikipedia.org/wiki/Multiplexer
Front-End Processors
Front-end processors: special-purpose computers
that manage communications to and from a
computer system (to networks, peripheral
devices)
Connect a midrange or mainframe computer to
hundreds or thousands of communications lines
Figure 6.9: Use of a Multiplexer to
Consolidate Data Communications onto a
Single Communications Link
Figure 6.10: Front-End Processor
Telecommunications Media
Connections
Micro to micro (modem)
(Dumb) Terminal to host
(mainframe/minicomputer) (direct wiring)
Micro to micro (direct)
LAN, WAN, PAN – Computer Networks
Uploading vs. downloading
Fig 6.19
Types of Media
Twisted Pair
Coaxial Cable
Fiber-Optic Cable
Wireless
Microwave Transmission, RF (WiFi, Bluetooth,
cellular), Inferred
Twisted Pair
Fig 6.4
Coaxial Cable
Fig 6.5
Fiber Optic Cable
Fig 6.6
Microwave Transmission
Fig 6.7
Satellite
Fig 6.8
Cellular
Fig 6.9
Infrared Transmission
Line of sight
Short distances
Local Area Networks
Server Based (Novell/Microsoft Active
Directory)
Peer-to-Peer (LANtastic, Windows)
Physically most common: Ethernet over
unshielded twisted pair.
Figure 6.15: The Basic Network
Topologies
Other
Gateway – for attaching different networks –
converts one protocol to another.
WAN
Wireless (Wi-Fi (802.11), Bluetooth)
PAN
What Is Client/Server?
Client/server is a term used to describe a computing
model for the development of computerized systems.
This model is based on the distribution of functions
between two types of independent and autonomous
processes; servers and clients.
A client is any process that requests specific services
from server processes.
A server is a process that provides requested services
for clients.
The key to client/server power is where the requested
processing takes place.
What Is Client/Server?
Basic Client/Server Computing
Client/Server Systems Benefits
Client/Server Benefits
Platform-independent system development
Optimized distribution of processing activities among
different platforms
Use of user friendly, cost effective, and compatible
techniques, methodologies, and specialized tools
Managerial Expectations of
Client/Server Systems Benefits
Organizational Expectations of Client/Server
Benefits
Flexibilityand adaptability
Improved employee productivity
Improved company work flow and a way to re-
engineer business operations
New opportunities to provide competitive
advantages
Increased customer service satisfaction
Client/Server Architecture
Components of Client/Server Architecture
Client. The client is any computer process that requests
services from the server. It is also known as the front-end
application.
Server. The server is any computer process providing
services to the clients. The server is also known as the
back-end application.
Client/Server Architecture
Client Components
Powerful hardware
An operating system capable of multitasking
A graphical user interface (GUI)
Communications capability
Client/Server Architecture
Types of Services
Fileservices
Print services
Fax services
Communications services
Database services
Transaction services
Application services
Web Services
The Internet, Intranets, and Extranets
Types of Internet Connections
Dialup (Modem)
ISDN (It Still Does Nothing, Innovations
Subscribers Don't Need)
Broadband (“high speed”)
DSL (ADSL) – (Asynchronous Digital Subscriber
Line)
Cable
T1, T2, T3, T4
Use and Functioning
of the Internet
The Internet
See Introduction to the Internet and the WWW
What is the Internet
a global set of interconnected data networks
running the TCP/IP protocols
Traditional services include email, file transfer
(FTP); current focus is on the World Wide Web
Largely self-financing; no single point of control
or administration (ANARCHY)
How the Internet Works
Hosts
Routers forward packets to other networks
Internet Protocol Stack (TCP/IP)
Protocol (IP)
Internet
Transport Control Protocol (TCP)
Backbones
How the Internet Works
Uniform Resource Locator(URL)
http://www.whitehouse.gov
World Wide Web Domain category
Hypertext
Host Network Name
transfer protocol
Table 7.1
Figure 7.3: Several Ways to
Access the Internet
Structure of the Internet
National/global backbone networks
Network Access Points (NAPS) connecting the
major commercial backbones
Internet Service Providers (ISPS)
“wholesale”:selling access to Users and other ISPS
“retail”:resell access to someone else's backbone
The World Wide Web
The World Wide Web
World Wide Web: AKA the Web, WWW, or W3
A menu-based system that uses the client/server
model
Organizes Internet resources throughout the
world into a series of menu pages, or screens,
that appear on your computer
Hypermedia: tools that connect the data on Web
pages, allowing users to access topics in
whatever order they wish
The World Wide Web (continued)
Hypertext Markup Language (HTML): the
standard page description language for Web
pages
HTML tags: inform browsers how to format text
on a Web page, and whether images, sound, and
other elements should be inserted
Extensible Markup Language (XML): markup
language for Web documents containing
structured information, including words,
pictures, and other elements
Html and XML Demo
Figure 7.4: Sample Hypertext
Markup Language
Web Software
Web browsers
Search engines
Keyword indexes: fast & broad
Subject indexes: focused searches
Table 7.7
Webcasting
aka Push Technology
Consolidates information according to a user’s
profile & displays in the browser
Internet Services
Web Services
Web services: standards and tools that
streamline and simplify communication among
Web sites for business and personal purposes
XML is used within a Web page to describe and
transfer data between Web service applications
Web Services (continued)
Besides XML, other components are used in
Web service applications:
SOAP (Simple Object Access Protocol)
WSDL (Web Services Description Language)
UDDI (Universal Discovery Description and
Integration)
Internet and Web Applications
E-mail and instant messaging
Instant messaging: a method that allows two or
more individuals to communicate online using
the Internet
Internet cell phones and handheld computers
Career information and job searching
Internet and Web Applications
(continued)
Telnet and FTP
Telnet: a terminal emulation protocol that enables
users to log on to other computers on the Internet to
gain access to public files
FileTransfer Protocol (FTP): a protocol that
describes a file transfer process between a host and a
remote computer and allows users to copy files from
one computer to another
Internet and Web Applications
(continued)
Web log (blog): a Web site that people can
create and use to write about their observations,
experiences, and feelings on a wide range of
topics
Usenet and newsgroups
Usenet: a system closely allied with the Internet that
uses e-mail to provide a centralized news service; a
protocol that describes how groups of messages can
be stored on and sent between computers
Newsgroups: online discussion groups that focus on
specific topics
Internet and Web Applications
(continued)
Chat room: a facility that enables two or more
people to engage in interactive “conversations”
over the Internet
Internet phone and videoconferencing services
Content streaming: a method for transferring
multimedia files over the Internet so that the
data stream of voice and pictures plays more or
less continuously without a break, or very few of
them; enables users to browse large files in real
time
Shopping on the Web
Fig 6.24
Figure 7.7: How Voice Over IP Works
Internet and Web Applications
(continued)
Web auctions
Music, radio, and video on the Internet
Office on the Web
Internet sites in three dimensions
Free software and services
Table 7.6: Summary of Internet and
Web Applications
Table 7.6: Summary of Internet and
Web Applications (continued)
Intranets and Extranets
Intranets and Extranets
Intranet
Internalcorporate network built using Internet and
World Wide Web standards and products
Slashes the need for paper
Provides employees with an easy and intuitive
approach to access information that was previously
difficult to obtain
Intranets and Extranets (continued)
Extranet: a network based on Web technologies
that links selected resources of a company’s
intranet with its customers, suppliers, or other
business partners
Virtual private network (VPN): a secure
connection between two points across the
Internet
Tunneling: the process by which VPNs transfer
information by encapsulating traffic in IP
packets over the Internet
Table 7.11: Summary of Internet,
Intranet, and Extranet Users
Figure 7.8: Virtual Private Network
Net Issues
Net Issues
Management issues: preventing attacks
Service and speed issues
Web server computers can be overwhelmed by
the amount of “hits” (requests for pages)
Routers can become bottlenecks
Figure 7.9: Typical Sources of
Internet Attacks
Net Issues (continued)
Privacy
Spyware: hidden files and information trackers that
install themselves secretly when you visit some
Internet sites
Cookie: a text file that an Internet company can
place on the hard disk of a computer system
Fraud
Phishing
Net Issues (continued)
Security with encryption and firewalls
Cryptography: converting a message into a secret
code and changing the encoded message back to
regular text
Digital signature: encryption technique used to
verify the identity of a message sender for
processing online financial transactions
Firewall: a device that sits between an internal
network and the Internet, limiting access into and
out of a network based on access policies
Unauthorized sites
Figure 7.10: Cryptography process
New Organizations
are Emerging
“Virtual Corporations”
Increasing usage of consultants; temporary
employees
Telecommuting
Questions (?)