Download ISP

Chapter 5
Internet 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
router
server
workstation
mobile
local ISP
– fiber, copper, radio, satellite
– transmission rate = bandwidth
regional ISP
• routers: forward packets
(chunks of data)
company
network
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”
router
server
workstation
mobile
local ISP
– loosely hierarchical
– public Internet versus private
intranet
regional ISP
• Internet standards
– RFC: Request for comments
– IETF: Internet Engineering Task
Force
company
network
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-2 ISP pays
tier-1 ISP for
connectivity to
rest of Internet
 tier-2 ISP is
customer of
tier-1 provider
Tier-2 ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
NAP
Tier 1 ISP
Tier-2 ISP
Tier-2 ISPs
also peer
privately with
each other,
interconnect
at NAP
Tier-2 ISP
Internet structure: network of networks
• “Tier-3” ISPs and local ISPs
– last hop (“access”) network (closest to end systems)
local
ISP
Local and tier3 ISPs are
customers of
higher tier
ISPs
connecting
them to rest
of Internet
Tier 3
ISP
Tier-2 ISP
local
ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
local
local
ISP
ISP
NAP
Tier 1 ISP
Tier-2 ISP
local
ISP
Tier-2 ISP
local
ISP
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 fiberoptic 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 between
Twisted Pair (TP)
transmitter/rcvr pairs
• two insulated copper wires
• physical link: what lies
– Category 3: traditional
between transmitter & receiver
phone wires, 10 Mbps
Ethernet
• guided media:
– signals propagate in solid media:
copper, fiber, coax
• unguided media:
– signals propagate freely, e.g.,
radio
– 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
to/from
cable
headend
cable
modem
router/
firewall
Ethernet
wireless
laptops
wireless
access
point
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
Availability for
Businesses
Modem
Speed (Kbps) Send Speed = Cost
Receive
Speed
33–56
No
Very low
Cable modem
64–1500
No
Medium
Very limited
ISDN
56–128
Yes
High
Widely available
xDSL
384–55,000
No
Low
Limited
Universal
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 streamingmedia 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