The Edge of IT

ITEC-200 Fall 2006 Topic 4: Telecommunications & Networks

Professor J. Alberto Espinosa

Agenda • Learn the basics about telecommunications • Introduction to networking concepts

Topic 4: Telecom p.2

Roadmap

Transaction Processing Decision Support Distributed Collaboration Enterprise Collaboration Financial Management etc.

Information Server Appl Client Appl DB DB Database IT & Business IT Infrastrucure: - HW & SW - Database - Telecom Business Applications IT & Business Topic 4: Telecom p.3

Telecom Basics

Telecom

1 0

“Any sufficiently advanced technology is indistinguishable from magic”

Arthur C. Clarke (a famous scientist)

2 worlds: Digital

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

Analog

signal (what humans sense) Topic 4: Telecom p.5

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 analog

or

digital signals

can both be transmitted using

either

Topic 4: Telecom p.6

Examples of Data and Signals

• • •

Internal computer bus Local area networks Computer data over digital phone lines (DSL)

•

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

• • • •

Video-conferencing Digital cable TV Music CD’s MP3/media players

• • • •

Regular telephone (voice transmission) Regular TV Analog cable TV Radio transmission Digital Signal Analog Signal Transmission Mode

Topic 4: Telecom p.7

Example: How Modems Work

Computers send digital signals, but regular telephone lines only transmit analog signals. A modem (

mod

ulator/

dem

odulator) converts the digital signals to analog (fast audible beeps) so that the message can be transmitted through telephone lines

Digital Signal Analog Signal Digital Signal Computer Modem (Modulation) Modem (Demodulation) Computer

Topic 4: Telecom p.8

Transmission Medium

= physical medium through which data signals travel

• All signals travel as kilohertz)

electromagnetic waves

– i.e., pulses (of voltage, light, etc.) at a given frequency (e.g., 1000 pulses per second or 1000 hertz, or 1

– Examples of transmission media:

– – – –

Twisted wire



Coaxial cable

 inexpensive, available in most buildings faster, thick, hard to wire

Fiber optic cable



Wireless

 expensive, faster, lighter, durable slower, flexible (microwave , radio, cellular, infrared) Topic 4: Telecom p.9

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

Topic 4: Telecom p.10

Characteristics of Channels

Transmission 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) Topic 4: Telecom p.11

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 traffic capacity more lanes  •

Bandwidth difference between the highest and lowest frequencies

(of a medium or channel) is defined as: the 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 Topic 4: Telecom p.12

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.) Topic 4: Telecom p.13

Bandwidth

Animation Topic 4: Telecom p.14

Medium and Channel Bandwidth Illustration

800 MHz

700 MHz 600 MHz 500 MHz 400 MHz

300 MHz

Channel Bandwidth = 400 MHz – 300 MHz = 100 MHz Medium Bandwidth = 800 MHz – 300 MHz = 500 MHz Number of Channels = 5 = 500 MHz / 100 MHz Topic 4: Telecom p.15

Electromagnetic Wave Frequencies

Example: WiFi -- 2.4 GHz = 2.4x10

9 (unregulated frequency) ( chart ) Kilohertz (KHz) = 10 3 ; Megahertz (MHz) = 10 6 ; Gigahertz (GHz) =10 9 Topic 4: Telecom p.16

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”

Topic 4: Telecom p.17

Circuit Switching

San Francisco Washington, DC Circuit Switches • 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) Topic 4: Telecom p.18

Packet Switching

e.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 Miami Packet Switches Atlanta Topic 4: Telecom p.19

Introduction to Networking

A Network

• Is a number (2 or more) of interconnected computer devices • The connecting devices are called

“nodes”

Topic 4: Telecom p.21

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 Topic 4: Telecom p.22

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 Topic 4: Telecom p.23

Physical Analogy: Postal Service

Actual Communication

Application: write a letter Application: read the letter Mail Person Local Post Office (for zip code) Mail Sorting Facility Trucks, Airplanes, Trains, etc.

Mail Person Local Post Office (for zip code) Mail Sorting Facility Trucks, Airplanes, Trains, etc.

Data Flow Physical Infrastructure: Highways, Sky, Railways, etc.

Topic 4: Telecom p.24

Another Analogy: A Telephone Network

Application: make a phone call Telephone

Actual Communication

Application: receive a phone call Telephone End Office or PBX Circuit Switch Telephone Network Physical Media End Office or PBX Circuit Switch Telephone Network Physical Media Cables, Airwaves, etc.

Data Flow Topic 4: Telecom p.25

A Generic 5-Layer Networking Model (each layer has its own set of protocols) Applications: E-Mail, Web, Chat, etc.

Data Communication

Application Layer Each layer is HW and/or SW performing a distinct function Transport Layer Applications: E-Mail, Web, Chat, etc.

Application Layer Transport Layer Network Layer Data Link Layer Physical Layer Data Flow The data flows from layer to layer and through the network 00100010010

Network

Network Layer Data Link Layer Physical Layer Topic 4: Telecom p.26

Network Layer Architecture: An Example

FYI Only – no need to study this •

Application Layer

(SW) Communicates with the

Transport Layer software applications

(e.g., e-mail, web pages) and break data into small packets and passes the packets to the (and reassembles incoming packets into original data) •

Transport Layer

(Usually SW) Communicates with the for error checking and flow control to each packet, and passes these larger data packets to the

Network Layer Application Layer

, adds some digits (and the other way around) •

Network Layer

(HW and/or SW) Communicates with the

Transport Layer

packet, adds network address information necessary to route the packets through the network, and passes these packets to the , gets each

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

converts incoming signals into data packets) , 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 Topic 4: Telecom p.27

Networking

Network =

• 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 •

INTER

connected

NET

works Topic 4: Telecom p.28

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 Topic 4: Telecom p.29

Key Implementation Decisions for LANs

•

Physical Layout

• Physical configuration of network

cables

in buildings

Structured Cabling

: – A standard for wiring commercial buildings – Horizontal wires connected vertically via – Via a

“backbone”

cable – Entry point into the building is through the (i.e., the medium)

“telecom closets”

– Telecom closets connected vertically to closets in other floors

“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 Bus (i.e. linear) topology

in the network – most predominant today Topic 4: Telecom p.30

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) Terminator Passive Hub Active Hub Wireless Transceiver Terminator Passive Hub

Topic 4: Telecom p.31

• • • • •

Wide Area Networks (WANs)

Cover

large geographical areas

states, countries) (e.g., across 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 Topic 4: Telecom p.32

Point to Point Connections in WANs

Needed 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 Topic 4: Telecom p.33

Connection Through Network Services in WANs

through

“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 Topic 4: Telecom p.34

Wide Area Networks

General Configuration

LAN 1 e.g. Dallas T1, T3, or ISDN

(point to point) Server

Frame Relay

Network Service WAN Service access points

ATM

Network Service Frame Relay Router Client

LAN 2 e.g.

New York

Server ATM Router T1, T3 or ISDN (point to point) Client Topic 4: Telecom p.35

Introduction to Inter-Networks: The Internet, Intranets and Extranets

3. Inter-Networking

An

“internet”

(in lower case)

=

• a network of networks (i.e.,

INTER

connected

NET

works) • 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”

Topic 4: Telecom p.37

The

TCP/IP

Reference Model (Internet = INTER connected NET works)

Ex:

EMail, Browsers, etc.

Application 1 Application Layer

TCP IP

Network Access Layer Physical Layer

Examples

•HTTP (Web)

Ex:

•SHTTP (secure Web) •SMTP, IMAP (e-mail) •FTP (file transfers) Mail Server, Web Server, etc.

Related Application Application Layer •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

TCP IP

Network Access Layer Physical Layer

The Internet

Topic 4: Telecom p.38

Routers: Application Layer

TCP “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

Router IP

Network Access Layer (protocol 1) Physical Layer 1

IP

Net 1 Access (protocol 1) Net 1 Access (protocol 2) Physical Layer Physical Layer Network 1 Network 2 Application Layer

TCP IP

Network Access Layer (protocol 2) Physical Layer 2

Network 1 Network 2

Topic 4: Telecom p.39

Intranets and Extranets

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 Topic 4: Telecom p.40

Firewalls and VPNs

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) Topic 4: Telecom p.41

Intranets, Extranets, Firewalls & VPNs

(cont’d.) Firewall

T1, T3, or ISDN

(point to point) Internet Service Access Points VPN IP Router IP Router VPN (Tunnelling)

Internet

VPN IP Router

T1, T3 or ISDN

(point to point) Firewall

Extranet Intranet

Firewall LAN Company A Topic 4: Telecom p.42

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

T1, T3, ISDN

(point to point) IP Router w/Firewall and VPN

Intranet

Most commercial routers have built in firewall and VPN functions Internet Service Access Points IP Router w/Firewall and VPN

Internet

IP Router w/Firewall and VPN

T1, T3 ISDN

(point to point)

Extranet

LAN Company A Topic 4: Telecom p.43

Network Configuration Example: (2) thru WAN + Internet

WAN T1, T3, or ISDN

ATM, Frame Relay or other Router WAN Service Access Points

WAN

Internet Service Access Points Router w/IP, ATM, Frame Relay, Firewall and VPN support

T1, T3 ISDN Internet

IP Router w/Firewall and VPN

Extranet

LAN 2 Company A Topic 4: Telecom p.44

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 Topic 4: Telecom p.45

Clients and Servers

Clients

– 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) Topic 4: Telecom p.46

Client-Server Computing

(cont’d.)

Client Client Server Network Response Service Request Server Client Server Client

Topic 4: Telecom p.47

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 Topic 4: Telecom p.48

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) Topic 4: Telecom p.49

Generic Client-Server Architecture

There are many variants of this architecture as presented in the next few slides

Client Server

To format and display information to end users Presentation Software

Request Client Application Software

Client Communication Software

Response Server Application Software

Server Communication Software Client Operating System Server Operating System Client Hardware Server Hardware

Network

Topic 4: Telecom p.50

Example: Client-Server Database Management Systems (DBMS)

Client Workstation

Presentation Software Database Application

Client Front-End DBMS

Client Communication Software Client Operating System Hardware Platform

Request Response Server Server Back-End DBMS

Server Communication Software Server Operating System Hardware Platform

Network Databases

Topic 4: Telecom p.51

Ex.: Web Client-Server

Client

Browser

Server

Web Server HTTP TCP/IP Client Communication Software Client Operating System Hardware Platform HTTP TCP/IP Server Communication Software Server Operating System Hardware Platform

Network

Web pages (HTML and other files) Topic 4: Telecom p.52

Ex.: Web Client-Server + Database Server

Client

HTML Form HTML Response

Server

Browser Web Server SQL Queries DBMS Server HTTP HTTP TCP/IP Client Communication Software Client Operating System TCP/IP Server Communication Software Server Operating System Hardware Platform Hardware Platform

Network

Web pages (HTML and other files)

Databases

Topic 4: Telecom p.53

Ex.:

“Thin Client”

or

“Fat Server”

model Most of the processing is done by the server

Thin Client

Presentation Software

Fat Server

Example: •Web Server-Browser Applications •The trend these days •Easy to support and upgrade applications for distributed use Application Software DBMS Client Communication Software Client Operating System Server Communication Software Server Operating System Hardware Platform Hardware Platform

Network

Topic 4: Telecom p.54

Ex.:

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

Fat Client

Example: •File Servers (Novell’s NetWare —your G drive, Windows NT) Presentation Software Application Software Client Communication Software Client Operating System Hardware Platform

Thin Server

Server Communication Software Server Operating System (incl. file management) Hardware Platform

Network

Topic 4: Telecom p.55

Examples of “Very Thin” Servers: Embeddable Web Servers

Topic 4: Telecom p.56

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) Topic 4: Telecom p.58

Wireless Technologies

Examples:

•Wireless Telephony •Wireless Ethernet and WiFi •Microwave Antennas •Bluetooth •Infrared •Radio Frequency Identifiers (RFID) Topic 4: Telecom p.59

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 Topic 4: Telecom p.60

Evolution of Wireless Telephony

• • • 1 st . Generation (

1G

) Wireless: analog service • 2 nd . 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) Topic 4: Telecom p.61

1 st 2 nd 3 rd

Wireless Telephony Networks (Cellular)

Generation: to analog To Landline Telephone Networks Generation: to digital Generation: to IP net Radio Frequency Channels Handover MS 4,8,12 1,5,9 3,7,11 Radio Frequency Channel Reuse 1,5,9 Land Links Radio Links 2,6,10 3,7,11 4,8,12 BS = Base Station MS = Mobile Station MSC = Main Switching Center Topic 4: Telecom p.62

Wireless Ethernet & WiFi

• Wireless

Ethernet

& Wireless Fidelity ( wireless local area networks

WiFi

) are standards for • 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 Topic 4: Telecom p.63

Wireless LANs

Wireless Transceiver Wired Office LAN Transceiver Wired connection to DSL, Cable Modem or other Internet Access Service Wireless Router Home Wireless LAN

Topic 4: Telecom p.64

Other Wireless Technologies

Microwave 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 Topic 4: Telecom p.65

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

Beam signal Bounce signal with RFID tag code

EZ Pass Database

in remote central location

RFID Tag

Topic 4: Telecom p.66