TELECOMMUNICATIONSTELECOMMUNICATIONSandand

NETWORKS 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 with other people ( is the most of network communications)

2. The ability to share– I– Software– Peripheral devices– P

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 NetworkL Network--Connects computers in

relatively

• W NetworksW Networks-- Connects computers that may be dispersedamong a number of buildings, or even in different cities.

• InternetInternet--International Network of Networks.

WAN

Types of LANs

PEach user can share

their computer’s resources with other LAN users

COnly 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

Storage and management of the data needed by the applicationData Management

Presentation The to the application

Business LogicActual business rules implemented

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 occurs

3. Where the (DBMS) and are located

Flexible Applications

Server Client

Data Management

Business Logic

PresentationBusiness LogicData Management

PresentationBusiness Logic

Any Combination is Possible

Design Server

Client

Production ServerBusiness Logic

Data Management

PresentationData Management

Business Logic

• 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 for all of the and easier to

Client/Server Advantages

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 - both IT professionals and knowledge workers.

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.

Routers are responsible for that messages take from the sendingcomputer to the destination computer.

Connecting Networks

Router

The connection between a LAN and a larger network is usually accomplished using a device called a

Router

WAN or Backbone

LAN

LAN

WANs

High Speed Backbone

Backbone is usually a type of network that has

Once a network is linked to a , it becomes part of the Internet community.

Wide Area Network

RR

R

R

R

R

R

RR

R

R

RR

Packet Switched NetworkData is packaged in for transmission.

Each packet follows through

the network.

PROTOCOLS• Protocol - a that specifies the

as well as the during transmission

• Following a certain , 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

• 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 standards used in a

LAN.

• 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 and works on the principle of 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 are TCP and IP– TCP provides for– IP provides the

mechanism

TRANSMISSION CONTROL PROTOCOL / INTERNET PROTOCOL

(TCP / IP)• Allows computers to regardless of

their 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 layer allows users and applications to access

– F protocol (FTP)– Simple 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 layer handles

• The layer handles the packets (, etc.)

• The layer details how is

through the networking

How Does the Internet Work??How Does the Internet Work??http://www.howstuffworks.com/web-server.htm

#1

#2 Browser communicates with 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.

209.1.144.212

Network Topology

The of computers in a network.

BusRing Star MeshHybrid Wireless

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 that use token ring software.

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

Twisted Pair Wire

• C cable - a better-constructed version of the phone twisted-pair cable.

Network Communications Media

Coaxial Cable

Fiber-Optic 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/Demodulatorconverts 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

• Cellulartransmissions

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– 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.

Fiber-Optic Cable

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 FTP Servers (used to upload and download files• Mail Servers 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.