Chapter 5Internet Hardware, Software and

Communications

Introduction

• Connection media• Cost of connecting• Streaming media (audio and video)• Internet telephony • Technologies used to enhance online business

communications

What’s the Internet: “nuts and bolts” view

• millions of connected computing devices: hosts = end systems

• running network apps

• communication links– fiber, copper, radio, satellite

– transmission rate = bandwidth

• routers: forward packets (chunks of data)

local ISP

companynetwork

regional ISP

router workstation

servermobile

What’s the Internet: “nuts and bolts” view

• protocols control sending, receiving of msgs– e.g., TCP, IP, HTTP, FTP, PPP

• Internet: “network of networks”– loosely hierarchical

– public Internet versus private intranet

• Internet standards– RFC: Request for comments

– IETF: Internet Engineering Task Force

local ISP

companynetwork

regional ISP

router workstation

servermobile

Internet structure: network of networks

• “Tier-2” ISPs: smaller (often regional) ISPs– Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet tier-2 ISP is customer oftier-1 provider

Tier-2 ISPs also peer privately with each other, interconnect at NAP

Internet structure: network of networks

• “Tier-3” ISPs and local ISPs – last hop (“access”) network (closest to end systems)

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP

Local and tier- 3 ISPs are customers ofhigher tier ISPsconnecting them to rest of Internet

Tier-1 ISP: e.g., Sprint

Sprint US backbone network

What’s a protocol?

human protocols:

• “what’s the time?”

• “I have a question”

• introductions

… specific msgs sent

… specific actions taken when msgs received, or other events

network protocols:

• machines rather than humans

• all communication activity in Internet governed by protocols

protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission,

receipt

Structure of the Internet

• IP address (Internet Protocol)– Computers use IP addresses to locate other computers on the

Internet

• Packet– Source address, a destination address, sequencing

information, error-control information and the data to be delivered to the destination address

• Router– Used to move packets across the Internet efficiently

Hardware

• The Internet employs many advanced hardware technologies – Various communications media used to connect hosts

– The roles hosts play on the Internet

• Servers• Communications Media• Storage Area Networks (SAN)

Servers

• Server– A host on the Internet that manages network resources and

fulfills requests from clients

– Web servers, e-mail servers, database servers and file servers

– A single server may provide multiple services

• A Web server stores Web pages and delivers the pages to clients upon request

• Protocols for delivering information over the Web– Hypertext transfer protocol (HTTP)

– File transfer protocol (FTP)

– Post office protocol (POP)

– Simple mail transfer protocol (SMTP)

Residential access: point to point access

• Dialup via modem

– up to 56Kbps direct access to router (often less)

– Can’t surf and phone at same time: can’t be “always on”

• ADSL: asymmetric digital subscriber line

– up to 1 Mbps upstream (today typically < 256 kbps)

– up to 8 Mbps downstream (today typically < 1 Mbps)

– FDM: 50 kHz - 1 MHz for downstream 4 kHz - 50 kHz for upstream

0 kHz - 4 kHz for ordinary telephone

Residential access: cable modems

• HFC: hybrid fiber coax

– asymmetric: up to 30Mbps downstream, 2 Mbps upstream

• network of cable and fiber attaches homes to ISP router

– homes share access to router

• deployment: available via cable TV companies

Communications Media

• Communications medium – The hardware that connects computers and other digital

equipment

• Bandwidth– Indicates how much data can be transferred through the

medium in a fixed amount of time

– Usually measured in bits per second (bps)

• Copper wire– The primary communications medium

Communications Media

• Fiber-optic cable– Composed of flexible glass fiber, is thinner and lighter than

traditional copper wire, yet has much wider bandwidth – Uses short bursts of light to represent bits

• Optical modem– Modem stands for modulator and demodulator– Translates digital signals from computers into light through a

process called modulation

• Opto chip– Converts the most basic particle of light, the photon, into an

electric current – Allows tremendous amounts of data to be sent over fiber-

optic networks through particles 100 times smaller than the diameter of a human hair

Communications Media

• The strength of a signal transmitted over a communications medium is reduced as the signal travels farther and farther

• Repeater– Can be used to alleviate this problem by amplifying and

retransmitting the signal across segments of copper wire or fiber-optic cable

• Transmission costs– Fiber-optic cable is more expensive than copper wire

– Installation of fiber-optic cable is more complicated than installation of copper wire

– Fiber-optic cable requires fewer repeaters

Physical Media

• Bit: propagates betweentransmitter/rcvr pairs

• physical link: what lies between transmitter & receiver

• guided media: – signals propagate in solid media:

copper, fiber, coax

• unguided media: – signals propagate freely, e.g.,

radio

Twisted Pair (TP)

• two insulated copper wires– Category 3: traditional

phone wires, 10 Mbps Ethernet

– Category 5: 100Mbps Ethernet

Physical Media: coax, fiber

Coaxial cable:• two concentric copper

conductors

• bidirectional

• baseband:– single channel on cable

– legacy Ethernet

• broadband:– multiple channel on cable

– HFC

Fiber optic cable:• glass fiber carrying light

pulses, each pulse a bit

• high-speed operation:– high-speed point-to-point

transmission (e.g., 5 Gps)

• low error rate: repeaters spaced far apart ; immune to electromagnetic noise

Physical media: radio

• signal carried in electromagnetic spectrum

• no physical “wire”

• bidirectional

• propagation environment effects:– reflection

– obstruction by objects

– interference

Radio link types:• terrestrial microwave

– e.g. up to 45 Mbps channels

• LAN (e.g., Wifi)– 2Mbps, 11Mbps

• wide-area (e.g., cellular)– e.g. 3G: hundreds of kbps

• satellite– up to 50Mbps channel (or multiple smaller

channels)

– 270 msec end-end delay

– geosynchronous versus low altitude

Storage Area Networks

• Companies produce large volumes of data to support sales analysis tools, enterprise resource planning (ERP) systems, multimedia Web sites and e-commerce systems

• Storage Area Network (SAN)– a network (referred to as a fabric) designed to attach

computer storage devices such as disk array controllers, tape libraries and CD arrays to servers.

– Provides high-capacity, reliable data storage and delivery on a network

– Allows network administrators to collect data in logical groups on data servers distributed throughout the network

– SAN devices store large volumes of data and may also provide backup and recovery services

Storage Area Networks

• Mirroring technology – A SAN device stores redundant copies of data, so that if one

copy is lost or damaged, a mirrored copy can be used

• Fiber-channel technology – A high-speed communications medium based on fiber-optic

technology that provides transfer rates of 100 Mbps

• Network storage devices providers – EMC

– Compaq

– StorageNetworks

Connecting to the Internet

• Most home users subscribe to an Internet Service Provider (ISP) to connect to the Internet – Some charge fixed monthly fees for Internet access– Some offer free Internet access in return for personal

demographic data

• Analog modem– User connects to an ISP using the modem, which then

connects the user to the Internet– Takes digital signals from the computer and turns them into

analog signals• Analog signals can be transmitted over a telephone line just

like a human voice

– A modem at the ISP then converts the sound back into a digital signal that can be transmitted over the Internet

Home networks

Typical home network components:

• ADSL or cable modem

• router/firewall/NAT

• Ethernet

• wireless access

point

wirelessaccess point

wirelesslaptops

router/firewall

cablemodem

to/fromcable

headend

Ethernet

Connecting to the Internet

• Free Internet access providers– NetZero– IsFree.com– ACI– Address.com

• Web TV– A low-cost technology for connecting to the Internet through

the user’s television, instead of a PC

– WebTV users can dial into an ISP through a modem to surf the Web, send and receive e-mail and chat with other people

– The basic WebTV system includes a wireless keyboard, an 8.6-GB, a hard drive and a 56-Kbps modem

Digital Subscriber Lines

• Digital Subscriber Lines (DSL)– Offers high-bandwidth Internet access over existing copper

telephone lines

– Splits your phone line into three information-carrying channels

– DSL connections require special hardware at the local telephone company’s central office and at the user’s location

Digital Subscriber Lines

• IAD (integrated access device)– Provides network connections for high-speed Internet

access, as well as connections for multiple voice telephone lines

• ADSL (asymmetric DSL) – the connection speed for sending data to the Internet

(upstream) is slower than the connection speed for receiving data from the Internet (downstream)

• VoDSL (voice over DSL)– Provides voice telephone services and high-speed data

access over a single standard telephone line

• SDSL (symmetric DSL)– Transfers data at the same speed both upstream and

downstream

Digital Subscriber Lines

Method Speed (Kbps) Send Speed = Receive Speed

Cost Availability for Businesses

Modem 33–56 No Very low Universal

Cable modem 64–1500 No Medium Very limited

ISDN 56–128 Yes High Widely available

xDSL 384–55,000 No Low Limited

Frame relay/T1 64–1544 Yes Very high Widely available Fig. 5.1 Internet connection comparison chart. (Courtesy of GLINK, LLC.)

Broadband

• Broadband– A category of high-bandwidth Internet service provided

mainly by cable television and telephone companies to home users

– Can handle voice, data and video information

– Enables videoconferencing, real-time voice and streaming-media applications

– Always connected, eliminating the need to dial into an ISP

• Cable modem– Translates digital signals for transmission over the same

cables that bring cable television to homes and businesses

– Connections is shared among many users

Integrated Services Digital Network (ISDN)

• ISDN (Integrated Services Digital Network)– Provides high-speed connections to the Internet over both

digital and standard telephone lines

– Limited service

– Costly connection

– Divided into three channels that each perform different tasks• Two bearer channels each support data transfers, while the

data channel is used to transmit routing information

– ISDNZone

T-1 and T-3 Lines

• T-1 line– A dedicated connection that supports data rates of 1.544 Mb

per second

– Made up of 24 channels

• T-3 line– Supports data rates of 43Mbps and is made up of 672

channels that each support 64Kbps

• T-1 and T-3 lines can be used for both voice and data communication

Internet2

• Consortium developing next generation of the Internet – Abeline

• A high-speed network currently used by Internet2 consortium members, will soon be able to transfer 2.4 gigabits of data per second

– Teleimmersion• Allows users in different locations to share information in real

time—even 3D images

– Virtual laboratory• Enable researchers worldwide to collaborate on projects

– Digital libraries • Storage of audio and video files, enabling a search for a

movie by a line from its soundtrack.

Software

• Application Service Providers• Databases

Application Service Provider

• Provide customized business software applications over the Internet

• Maintains and updates the application as necessary• Companies can eliminate the costs associated with

developing and maintaining business applications• Virtual private networks (VPNs)

– Allow customers to connect to their applications securely over the Internet

– VPNs use the point-to-point tunneling protocol (PPTP) to create a secure channel of communication between the customer and the ASP

Databases

• Database– An integrated collection of data

• Database management system (DBMS) – Provides mechanisms for storing and organizing data in a

manner that facilitates satisfying sophisticated queries and data manipulations

• Structured Query Language (SQL)– Almost universally used with relational database systems to

make queries (i.e., to request information that satisfies given criteria) and manipulate data

Databases

• Relational database model – A logical representation of the data that allows the

relationships between the data to be considered independently of the physical implementation of the data structures

• Popular enterprise-level relational database systems:– Microsoft Sequel Server

– Oracle

– Sybase

– DB2

– Informix

Operating Systems

• Operating system (OS) – Software that manages the resources on a computer – Multiuser OS

• Allows more than one user to run programs simultaneously

– Multiprocessor OS • Controls a computer that has many hardware CPUs

– Multitasking OS • Allows multiple applications to run simultaneously

– Multithreading OS • Allows an individual program to specify that several activities

should be performed in parallel

• Major operating systems used in desktop computers are UNIX , Linux , Macintosh and Windows

Unix

• Multics– “All things to all people”

– Bell Laboratories, General Electric and Project MAC

• Unix– Developed by Bell Laboratories after leaving the Multics

project

– First version written in assembly language

– Unique design and coherence

– Met the needs of programmers who were building software and of administrators who control software development efforts

Unix

• University of California at Berkley– From time sharing to systems appropriate for studying

distributed computing environments

• Sun Microsystems– Sun OS

– Include facilities for supporting a graphics, window-based, mouse-oriented interface

– Provided facilities for diskless workstations to use the network for file storing, sharing and paging

• The Open Group– Controls the specification for UNIX and holds the trademark

– www.unix-systems.org

Microsoft Windows

• The most popular operating system in the world

• Introduced in 1984 with graphical user interface (GUI) added to the DOS system

• Windows 2.0– Failed to make a large impact in the market

– Took too long to open applications, change screens, etc.

• Windows 3.0 – Achieved widespread success

• Windows 95– Introduced a new graphical user interface and increased

performance

• Windows 98, Windows NT and Windows 2000

• Windows XP and Windows Vista

Linux

• Linux– A UNIX-like operating system that has been developed by

volunteers worldwide

– Initially developed by Linus Torvalds

– Greatest success on the server-side

• Version 1.0– Released in 1994, gained market share to become one of the

world’s most widely used operating systems

• The Gnome Foundation– Founded to develop a free Linux-based desktop environment

and a free application framework to compete with Microsoft Office for the desktop-computer environment

Linux

• Open source software– Freely available source code, so that anyone can use, customize

and make updates to the software

• Kernel– The core of the operating system

• Most of the applications that run on Linux are freely available over the Internet and on many CD-ROM distributions

• GNU General Public License (GPL) – One of the most widely used open-source licenses

– Requires that the source code for GPL-licensed software, as well as the source code for any modifications or improvements to that software, is made freely available to the public

Microsoft.NET

• Microsoft.NET– Weaves together the operating system, the Internet and each

device to create applications and services to be accessed anytime, anywhere, from any device

– Could potentially support UNIX and Linux

• Building and maintaining .NET components– Windows.NET

– Visual Studio.NET

– Integrated development environment (IDE)

– .NET Enterprise Servers and the .NET framework

• .NET applications will be built with XML

Mac OSX

• Achieved great success in the 1980s, dominating the market for GUI-based personal computers

• One of the first widely available systems to use a window-based (i.e., a GUI) interface, a mouse and icons

• Release of Windows challenged MacIntosh sales• Mac OS X operating system

– Core was built using industry open standards based on Unix

• Aqua– New Mac OS X interface

Internet Appliances

• Internet appliances – Desktop devices designed specifically for connecting to the

Internet

– iPAQ Home Internet Appliance

– Netpliance i-opener

• Devices allow you to browser the Web, send and receive e-mail and access streaming media online

• Limited functionality

Enhancing Business Communication

• Intranets• Extranets• Streaming audio and video • Internet telephony

– Makes PC-to-PC and PC-to-phone calls possible, dramatically reducing the cost of communication

• Web casting• Virtual conferencing• Wireless technology

Intranets and Extranets

• Intranet– An organization’s internal network that uses the TCP/IP

protocols of the Internet

– Only authorized parties, such as the organization's employees, have access to an organization’s intranet

– Used to store internal information

• Extranet – An intranet that is also accessible by authorized external

parties who are not members or employees of the organization

– Members or employees might have unrestricted access to information on the extranet, whereas customers or vendors might have access to a limited subset of that information

Streaming Audio and Video

• Streaming technologies– Allow users to send and process audio and video data

continuously

– Allows users to start playing the audio or video file while it is still downloading

– Users can play music over the Internet

– Users can watch a small video on a Web site

Streaming Audio and Video

RealPlayer dialog. (Copyright© 1995-2000 Realnetworks, Inc. All Rights Reserved. RealNetworks, Real.com, RealPlayer are trademarks registered trademarks of of RealNetworks, Inc.)

Internet Telephony

• Internet telephony– Enables communication over the Internet, allowing you to

use your PC as a telephone

– Cost efficient

• Net2Phone– Service allows you to make free PC-to-telephone calls

within the United States, and international calls at discounted rates

– Net2Phone and other Internet telephony services are not always compatible with systems running firewalls

– ClickTogether service allows companies to add personalized voice capabilities to a Web site

Webcasting and Web Conferencing

• Webcasting – Broadcasting over the Web

– Businesses can stream seminars, conferences, shows, sales presentations and more though their Web sites

– Live or prerecorded

• Web conferencing– Allows businesses to meet and collaborate online, in real

time from anywhere in the world

• Evoke– Webcasting and Web conferencing