topic 4: telecommunications & networks professor j. alberto espinosa the edge of it itec-200...

Topic 4: Telecommunications & Networks

Professor J. Alberto Espinosa

B u s in e s s W o r ldT r a n s a c t io n s

T r a n s a c t io n P r o c e s s in g

C l ie n tA p p l

D B

S e r v e rA p p l

D BD a ta b a s e

In fo r m a t io nD e c is io n S u p p o r tD is t r ib u te d C o l la b o r a t io nE n te r p r is e C o l la b o r a t io nF in a n c ia l M a n a g e m e n t

e t c .

E R P , S u p p ly C h a in M g t , e t c .

( I n te r / I n t r a ) N e t w o r k

The Edge of IT ITEC-200 Fall 2006

Topic 4: Telecom p.2

Agenda

• Learn the basics about telecommunications

• Introduction to networking concepts


Roadmap

IT &Business

ITIn

fra

stru

ctu

re

Database

DB DB

IT Infrastrucure: - HW & SW - Database - Telecom

Transaction ProcessingB

usi

nes

sA

ppl

ica

tion

s InformationDecision SupportDistributed CollaborationEnterprise CollaborationFinancial Management

etc.Client Appl

ServerAppl

Business Applications

IT & Business

Telecom Basics


Telecom

“Any sufficiently advanced technology isindistinguishable from magic”

Arthur C. Clarke (a famous scientist)

2 worlds:

Digital signal (what computers understand: e.g., 00111001)

Analog signal (what humans sense)

1

0


Data and Transmission Signals

• Data is what you want to transmit

• Data is transmitted with signals through a communication medium

• Data can be analog (sine waves)

– i.e., what humans understand (e.g., voice, video)

• Or it can be digital (square signals representing 0’s and 1’s)

– i.e. what computers understand (e.g., bit and bytes)

• Analog and digital data can both be transmitted using either

analog or digital signals


Examples of Data and Signals

• Internal computer bus

• Local area networks

• Computer data over digital phone lines (DSL)

• Regular telephone (voice transmission)

• Regular TV

• Analog cable TV

• Radio transmission

• Video-conferencing

• Digital cable TV

• Music CD’s

• MP3/media players

• Computer data over regular phone line dial-up connection (via modem)

Digital Signal Analog Signal

Transmission Mode

Dig

ital

Dat

aA

nal

og

Dat

a

Ori

gin

al D

ata

Fo

rm


Digital Signal

Computer

Example: How Modems Work

Analog Signal

Modem (Demodulation)

Computer Modem (Modulation)

Digital Signal

Computers send digital signals, but regular telephone lines only transmit analog signals. A modem (modulator/demodulator) converts the digital signals to analog (fast audible beeps) so that the message can be transmitted through telephone lines


Transmission Medium

= physical medium through which data signals travel

• All signals travel as electromagnetic waves – i.e., pulses (of voltage, light, etc.) at a given frequency (e.g., 1000 pulses per second or 1000 hertz, or 1 kilohertz)

– Examples of transmission media:

– Twisted wire inexpensive, available in most buildings– Coaxial cable faster, thick, hard to wire– Fiber optic cable expensive, faster, lighter, durable– Wireless slower, flexible (microwave, radio, cellular, infrared)


Transmission Channels

• A channel is the link between a sending and receiving point

• A medium is usually broken into several channels, depending on the medium’s capacity, so that data can be transmitted simultaneously through various channels:e.g., cable TV signal, cell phone signals


Characteristics of ChannelsTransmission speed or capacity• How much data you can send per second• Kilo/Mega/Gigabits per second (Kbps/Mps/Gps)• Affected by medium bandwidth, network traffic,

noise, transmission errors

Transmission Frequency• Cycles per second of the electromagnetic signal• Not necessarily related to transmission speed• It is just the nature of how the signal travels through a

medium• Measured in hertz (cycles per second), kilohertz, etc.

Bandwidth (see next slide)


Bandwidth

• Every data transmission medium (e.g., cables, airwaves, etc.) and each of its channels, have a bandwidth that affect the data transmission capacity of that medium or channel:

More bandwidth more channels more capacity to transmit data

Metaphor: wider highway more lanes more traffic capacity

• Bandwidth (of a medium or channel) is defined as: the difference between the highest and lowest frequencies that can be transmitted (through that medium or channel)

• e.g., if a channel or medium can transmit from 300Mz to 800Mz, the bandwidth is 800 - 300 = 500Mz


Splitting the Medium into Channels

• A useful physics principle about electromagnetic waves: waves of different frequencies don’t mix!! (sound check)

• Therefore, we can send more than one signal through a medium, provided that each signal uses a different frequency

– Ex. You 100+ TV channels through one channel– Ex. Your cell phone signals don’t mix with those of your neighbor– Ex. Signal from radio station doesn’t mix with another station

• But if the frequencies of two channels are too close to one another, there may be some interference (noise, etc.)

http://www.looknohands.com/chordhouse/guitar/index_db.html


BandwidthAnimation

http://media.pearsoncmg.com/ph/bp/bp_beekman_compconf_7/chapter_content/animations/PH_04_08.swf


Medium and Channel Bandwidth Illustration

800 MHz

700 MHz

600 MHz

500 MHz

400 MHz

300 MHz

Medium Bandwidth = 800 MHz – 300 MHz = 500 MHz

Number of Channels = 5 = 500 MHz / 100 MHz

Channel Bandwidth = 400 MHz – 300 MHz = 100 MHz


Electromagnetic Wave Frequencies

Example: WiFi -- 2.4 GHz = 2.4x109 (unregulated frequency) (chart)

Kilohertz (KHz) = 103; Megahertz (MHz) = 106; Gigahertz (GHz) =109


Switching

• How does data travel over distance from point A to point B?

• It travels from the source (the sending point), to the destination (the receiving point)

• Going through switching points widely distributed throughout the country (and the world)

• Every switching point has equipment (i.e., hardware and software) called “switches” that take care of making the necessary connections and finding the best routes

• There are two general types of switching methods:

“Circuit Switching” and “Packet Switching”


Circuit Switching

• Dedicated path (“circuit”) between communication points

• Connected through switching nodes• Good for continuous transmissions• e.g., voice and video (e.g., telephone networks)• Inefficient otherwise (idle circuit connection ties

up the circuit)

San Francisco Washington, DC

Circuit Switches


Packet Switchinge.g. ATM, Frame Relay

• Data is broken into packets• Each packet contains destination and

re-assembly info (packet #, msg #)• Each packet is sent separately • And reassembled at the receiving end• Good for data transmissions

Packet Switches

AtlantaMiami

Introduction to Networking


A Network

• Is a number (2 or more) of interconnected computer devices

• The connecting devices are called “nodes”


Protocols

A Protocol = “A set of rules and procedures that govern data transmissions between components in a network”

For two entities (e.g., computers, persons, radios) to communicate, there needs to be a protocol

• Implemented in software and/or hardware• Examples of protocols: TCP, IP, FTP, HTTP


The Network Layer Architecture• Networks are very complex• Because there are too many HW and SW components

communicating with each other• So, ensuring reliable/fast data communications requires

numerous networking steps and functions• No single networking component can do this alone• Thus, different networking functions are carried out by

different specialized components• These components are arranged in layers.• Each layer function is performed by specific HW and/or SW• Each layer needs to follow the standard communication

protocols agreed upon for that layer


Physical Analogy: Postal Service

Mail Sorting Facility

Mail Person

Local Post Office(for zip code)

Application: write a letter

Trucks, Airplanes,Trains, etc.

Actual Communication

Mail Sorting Facility

Mail Person

Local Post Office(for zip code)

Application: read the letter

Physical Infrastructure: Highways, Sky, Railways, etc.

Trucks, Airplanes,Trains, etc.

Data Flow


Another Analogy: A Telephone Network

Physical Media

Circuit Switch

Telephone

End Office or PBX

Physical Media

Telephone Network

Telephone

Application:make a phone call

Telephone Network

Circuit Switch

ActualCommunication

End Office or PBX

Cables, Airwaves, etc.

Application:receive a phone call

Data Flow


A Generic 5-Layer Networking Model(each layer has its own set of protocols)

Network

Physical Layer

Data Link Layer

Network Layer

Application Layer

Transport Layer

Physical Layer

Data Link Layer

Network Layer

Application Layer

Transport Layer

The data flows from layer to layer and

through the network

00100010010

Each layer is HW and/or SW performing

a distinct function

Data CommunicationApplications:

E-Mail, Web, Chat, etc.

Data Flow

Applications:E-Mail, Web, Chat, etc.


Network Layer Architecture: An ExampleFYI Only – no need to study this

Application Layer• (SW) Communicates with the software applications (e.g., e-mail, web

pages) and break data into small packets and passes the packets to the Transport Layer (and reassembles incoming packets into original data)

Transport Layer• (Usually SW) Communicates with the Application Layer, adds some digits

for error checking and flow control to each packet, and passes these larger data packets to the Network Layer (and the other way around)

Network Layer• (HW and/or SW) Communicates with the Transport Layer, gets each

packet, adds network address information necessary to route the packets through the network, and passes these packets to the Data Link Layer (and picks up packets routed from other layers).

Data Link Layer • (Usually HW) Communicates with the Network Layer and manage the

traffic flow of data packets from the computer to Physical Layer (and acknowledges receipt of incoming packets from other networks).

Physical Layer• (HW) Communicates with the Data Link Layer, gets the packets and

converts them into (analog or digital) signals that can be transmitted over that particular network physical medium (cable, fiber optics, airwaves) (and converts incoming signals into data packets)


NetworkingNetwork =

• A facility that interconnects a number of devices• To transmit data from one attached device to another

Networks are classified by their GEOGRAPHIC SCOPE:

1. Local Area Networks (LANs)• typically within a single building (e.g. Kogod) or small area

(AU)• Metropolitan Area Networks (MANs) are like LANs but

for multiple buildings throughout a city.

2. Wide Area Networks (WANs)• over larger geographical areas (e.g., across states,

countries)

3. Inter-Networks = “internets” = networks of networks• INTERconnected NETworks


1. Local Area Networks (LANs)

• Small scope network• Typically within a single building (e.g. Kogod)• Or within a small group of nearby buildings

(e.g., AU Campus)• If the network spans several buildings

throughout a city it is often called a Metropolitan Area Network (MAN)

• High data rates


Key Implementation Decisions for LANs

Physical Layout• Physical configuration of network cables (i.e., the medium)

in buildings• Structured Cabling:

– A standard for wiring commercial buildings– Horizontal wires connected vertically via “telecom closets”– Telecom closets connected vertically to closets in other floors– Via a “backbone” cable– Entry point into the building is through the “equipment room”

Transmission Medium (physical layer)• Medium used to connect hardware nodes• Twisted pair, co-axial, fiber optics, wireless, etc.

Network Topology• Configuration of hardware nodes in the network• Bus (i.e. linear) topology – most predominant today


Bus (linear) Topology w/Hubs• Very popular network is easily scalable via hubs:

– Passive Hubs to connect nodes to the network– Active Hubs to connect other hubs (to amplify signal)

• Physically, it looks like star topology, but it is “bus topology”• Every hub “extends” the bus• Predominant with “Ethernet” networks (AU’s Novell LAN)

Passive Hub

PassiveHub

Active Hub Transceiver

Wireless

TerminatorTerminator


Wide Area Networks (WANs)• Cover large geographical areas (e.g., across

states, countries)

• Wired, wireless or both

• A company’s WAN is generally implemented by interconnecting all the LANs in the company’s multiple office locations

• Each location’s LAN has a ROUTER that connects the LAN to a WAN service provider’s access point

• The connection from the router to the WAN service access is called point-to-point connection


Point to Point Connections in WANsNeeded to connect your home or office to a

network service provider

• DSL: digital subscriber line, fast dedicated(ADSL is asymmetric DSL same as DSL but receive speed is higher than send speed)

• ISDN: dial up digital telephone lines, fast

• T1, T3, etc.: fastest (1.5 Mbps +), dedicated digital lines, which is always connected (no need to dialup)

• Note: two or more LAN’s in a city can also be interconnected with point-to-point connections (forming a MAN). For example, you can connect two office LANs using a T1 line – the cost depends on the distance between the two offices


Connection Through Network Services in WANsthrough “Packet Switching” Nodes

• There are many types of wide area network services, which vary according to the type of packet switching technology they use. The main kinds of switching technologies are:

• Frame Relay:– Variable transfer speed– You pay more for faster speeds– Speeds: 64 Kilobytes per second (Kbps) to 45 Mbps

• Asynchronous Transfer Mode (ATM)– NOT THE SAME AS A BANK’S ATM– Really fast networks– Very fast data packet switching at fixed speeds– Speed: up to 1 Gbps


Wide Area NetworksGeneral Configuration

Client

Server

LAN 1e.g. Dallas

Frame RelayRouter

T1, T3, or ISDN(point to

point)

ATMNetworkService

Server

LAN 2e.g.

New York

ATM Router

Client

T1, T3or ISDN(point

to point)

Frame Relay Network Service

WAN Service access points

Introduction to Inter-Networks:

The Internet, Intranets and Extranets


3. Inter-Networking

An “internet” (in lower case) =• a network of networks

(i.e., INTERconnected NETworks)• Connected through routers and packet

switching nodes (Frame Relay, ATM, etc.)

“The Internet” (capitalized)• the most popular public “internet”• All nodes connected to “The Internet”

communicated using the same widely adopted & supported protocol = “TCP/IP”


The TCP/IP Reference Model (Internet = INTERconnected NETworks)

The Internet

Physical Layer

Network Access Layer

IP

Application Layer

TCP

Physical Layer

Network Access Layer

IP

Application Layer

TCP

Application 1 Related Application

Ex: EMail, Browsers, etc. Examples

•HTTP (Web)

•SHTTP (secure Web)

•SMTP, IMAP (e-mail)

•FTP (file transfers)

•SNMP (network mgt)

“Transmission Control Protocol”Provides a reliable connection between the 2 applications

“Internet Protocol” Routing functions across multiple networks using an IP address

Ex: Mail Server, Web Server, etc.


Routers:

Network 1

Physical Layer 1

Network Access Layer (protocol 1)

IP

Application Layer

TCP

Physical Layer 2

IP

Application Layer

TCP

Network 2

Net 1 Access (protocol 1)

IP

Physical Layer Network 1

Physical LayerNetwork 2

Net 1 Access (protocol 2)

Router

Network Access Layer (protocol 2)

“The Internet” is a network of networks. A router connects two networks (similar or dissimilar) – e.g., your company’s LAN and its Internet service provider’s network. It routes IP packets from one network to another through it’s IP layer


An “Intranet”• A company’s internal network• Spanning multiple geographic locations• Interconnected via the Internet instead of a WAN• Usually protected by “Firewalls”• Usually secured with “Virtual Private Networks

(VPNs)”

An “Extranet” • Similar to an intranet, but external with other

companies

Intranets and Extranets


Firewalls

• Hardware and/or software that restrict access into and out of a the company‘s internal networks or intranets

– They protect your internal network from outsiders

– They don’t protect your communications outside

“Virtual private networks (VPNs)”• Provide secure internal networks or intranets• Protect your internal communications on the outside• Uses “Tunneling” (encrypt transmissions betw points)

Firewalls and VPNs


VPN

IPRouter

VPN (Tunnelling)

LA

N C

om

pan

y A

Firewall

Internet ServiceAccess Points

Internet

LA

N C

om

pan

y B

Firewall

LAN Company A

Intranet Extranet

VPN

Intranets, Extranets,Firewalls & VPNs (cont’d.)

T1, T3, or ISDN(point to

point)

T1, T3or ISDN(point

to point)

IPRouter

IPRouter

Firewall


LA

N C

om

pan

y A

IP Router w/Firewall and VPN


Internet

LA

N C

om

pan

y B

LAN Company A

Intranet Extranet

Network Configuration Example: (1) thru the Internet (no WAN)

T1, T3, ISDN

(point to point)

T1, T3ISDN(point

to point)IP Router w/Firewall and VPN


Most commercial routers have

built in firewall and VPN functions


WAN

Internet

LA

N 1

Co

mp

any

A

ATM, Frame Relay or

other Router

WAN ServiceAccess Points

LA

N C

om

pan

y B

LAN 2 Company A

WANExtranet

Network Configuration Example: (2) thru WAN + Internet

T1, T3, or ISDN

T1, T3ISDN

Router w/IP, ATM, Frame

Relay, Firewall and VPN support




Client-Server Architecture

• A key technological development in the 90’s

• A form of “distributed computing”

• Most predominant computing architecture today

• Software application (i.e., processing) is split into tasks

• These tasks are distributed among computers

• Depending where it is more efficient to do the processing


Clients and ServersClients

– Request specialized services from servers, and – Perform other tasks for users (e.g., screen displays)

Servers– Acknowledge service requests from clients, and – Provide requested services (i.e., tasks, processes)– Via responses to clients

• Servers and clients connect via networks• Client and servers don’t work in isolation, but they are

designed to work together (i.e. there is no client without a server, there is no server without a client)


Client-Server Computing (cont’d.)

Network

Client

Service Request

Response

Client Server

Server Client Server Client


Examples of Servers

• A server can be hardware, software or both• File Server central file storage, process file requests

(ex. Novell’s NetWare, Windows NT)• Database Server back-end DBMS functions

(ex. MS SQL Server, Oracle Server, Lotus Notes Server)• Web Server store and fetch web files on request

(ex. Apache, Microsoft IIS)• Print Server print job queuing for central printers• Mail Server routes mail to users and other mail servers


Examples of Clients

• A client can be hardware, software or both

• Networked PCs request files and other services from file servers (Windows 2000, XP)

• Database Clients request records from database server, process data locally, screen formatting, etc. (Lotus Notes client, MS Access)

• Web Browsers request web files from web servers, translate HTML code into formatted screen displays(Internet Explorer, Netscape)

• Mail Client Send/retrieve mail to/from mail servers, organize and display user mail(Outlook Express; Lotus Notes mail client)


Generic Client-Server ArchitectureThere are many variants of this architecture

as presented in the next few slides

Client Server

Request

Network

Client Hardware

Client Operating System

Client ApplicationSoftware

Client Communication Software

Presentation Software

Server Hardware

Server Operating System

Server ApplicationSoftware

Server Communication Software

Response

To format and display information to end users


Example: Client-Server Database Management Systems (DBMS)

Client Workstation

ServerRequest

Network

Hardware Platform


Client Front-End DBMS



Hardware Platform


Server Back-End DBMS


Response

Database Application

Databases


Ex.: Web Client-Server

Client Server

Network

Hardware Platform



Hardware Platform


HTTP


Browser Web Server

HTTP

TCP/IP TCP/IP

Web pages (HTML and other files)


SQL Queries

Ex.: Web Client-Server + Database Server

ClientServer

Network

Hardware Platform



Hardware Platform


HTTP


Browser

Web Server

HTTP

TCP/IP TCP/IP

Web pages (HTML and other files)

DBMS Server

Databases

HTML Form

HTML Response


Ex.: “Thin Client” or “Fat Server” model Most of the processing is done by the server

Thin Client Fat Server

Network

Hardware Platform



Hardware Platform


Application Software



DBMS

Example:

•Web Server-Browser Applications

•The trend these days

•Easy to support and upgrade applications for distributed use


Fat Client Thin Server

Network

Hardware Platform



Hardware Platform

Server Operating System(incl. file management)



Application Software

Example:

•File Servers (Novell’s NetWare—your G drive, Windows NT)

Ex.: “Fat Client” or “Thin Server” model Most of the processing is done by the client


Examples of “Very Thin” Servers: Embeddable Web Servers

Introduction to Wireless Communications

and Networks


Wireless Communications•One of the fastest growing areas of IT•There are many types of wireless technologies available these days. The only similarity is that they don’t use wires. Otherwise they are all very different.

•Some key concepts to help you distinguish these technologies:–Line-of-sight: when physical objects in between devices

block communications (e.g. your TV remote control)–Frequencies:

•Lower frequencies = longer distance, less line-of-sight required (e.g., radio waves, cell phone signals)

•Higher frequencies = shorter distances, line-of-sight required (e.g., visible light, infrared)


Wireless Technologies

Examples:

•Wireless Telephony•Wireless Ethernet and WiFi•Microwave Antennas•Bluetooth•Infrared•Radio Frequency Identifiers (RFID)


Wireless Telephony•Mobile units communicate with ground antennas

•Ground antennas are connected with each other with ground wires

•And with the PSTN (public service telephone network), also known as POTS (plain old telephone systems)

•Your telephone signal travels from your mobile cell phone, to a ground antenna, to the regular telephone system


Evolution of Wireless Telephony• 1st. Generation (1G) Wireless: analog service• 2nd. Generation (2G) Wireless: digital service (PCS in the

US, GSM in Europe) compression (more channels), encryption and data transmission are enabled with digital communication

• 2.5 G: provide packet switching services for more efficient transmission of data (e-mail, minimal web access, PDA’s, etc.)

• 3G: high speed multi-media transmission and better Internet access

• (see http://www.devx.com/wireless/Door/11259 for terminology)

http://www.devx.com/wireless/Door/11259


Wireless Telephony Networks (Cellular)To Landline Telephone Networks

BS = Base StationMS = Mobile StationMSC = Main Switching Center

MS

Land Links

Radio Links

1,5,9

1,5,9

2,6,10

3,7,11 3,7,11

4,8,12

4,8,12

Radio FrequencyChannelReuse

1st Generation: to analog2nd Generation: to digital3rd Generation: to IP net

Handover

Radio FrequencyChannels


Wireless Ethernet & WiFi•Wireless Ethernet & Wireless Fidelity (WiFi) are standards for wireless local area networks

•Standards: 802.11a, b, g, etc. – different speeds, frequencies, capacities and ranges (see http://www.devx.com/wireless/Door/11259 for terminology)

•Short range (up to 250 ft) communication between devices (note: this is changing with new technologies like WiMax)

•Large office LANs have wireless transceivers (i.e., transmitters/receivers) attached to the wired network, so that wireless devices (e.g., network cards on your laptops) can connect to the wired network over the airwaves

•Small LANs and home networks have a wireless router attached to the wired Internet service access (e.g., DSL, cable modem) with which all wireless devices communicate

•Wireless access points are called “hot spots”•Great for mobility and when wiring buildings is difficult

http://www.devx.com/wireless/Door/11259


Wired Office LAN

Wireless LANs

Transceiver

Wireless

Wireless Router

Wired connection to DSL, Cable Modem or other Internet Access Service

Transceiver

Home Wireless LAN


Other Wireless TechnologiesMicrowave Antennas

–Low frequency antennas to interconnect, for example, two nearby buildings (with roof microwave antennas) without wires

Bluetooth (named for a Danish King)–Wireless technology developed by a group of

companies (IBM, Nokia, Intel, Lucent, etc.) to connect small devices wirelessly from short distances (30-50 ft)

–Ideal for wireless speakers, keyboards, printers–Less line-of-sight required than infrared

Infrared–High frequency signals to send signals from one

device to another at very short distances and line-of-sight

–Ex. TV remote controls, printer infrared ports


Other Wireless Technologies (cont’d)

Radio Frequency Identifiers (RFID’s)–Devices (small chips, tags, etc.) that contain small amounts of

data that can be transmitted to an RFID sensor wirelessly–The tags can be passive (RFID tag has no power, the reader

reads the RFID) or active (the RFID tag has a power source and can beam its own signals to the sensor)

–The RFID readers are connected to networks that transmit the data (e.g., EZ Pass)

RFID Sensor

RFID Tag

EZ PassDatabasein remote

centrallocationBeam signal

Bounce signal with RFID tag code

Submit RFID tag code, toll

location and time stamp to

EZ Pass central system

topic 4: telecommunications & networks professor j. alberto espinosa the edge of it itec-200...

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