Download Lecture 5 - Chapter 4

Ralph M. Stair | George W. Reynolds
Chapter 4
Telecommunications and
Networks
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or duplicated, or posted to a publicly accessible website, in whole or in part.
Principles and Learning Objectives:
Telecommunications System
• A telecommunications system has many
fundamental components that must be
carefully selected and work together
effectively to enable people to meet
personal and organization objectives
– Identify and describe the fundamental
components of a telecommunications system
– Identify several network types and describe
the uses and limitations of each
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or duplicated, or posted to a publicly accessible website, in whole or in part.
2
Principles and Learning Objectives:
Processing Alternatives
• A telecommunications system has many
fundamental components that must be
carefully selected and work together
effectively to enable people to meet
personal and organization objectives
– Name three basic processing alternatives for
organizations that require two or more
computer systems and discuss their
fundamental features
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or duplicated, or posted to a publicly accessible website, in whole or in part.
3
Principles and Learning Objectives:
Critical Infrastructure
• The Internet provides a critical
infrastructure for delivering and accessing
information and services
– Briefly describe how the Internet works,
including methods for connecting to it and the
role of Internet service providers
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or duplicated, or posted to a publicly accessible website, in whole or in part.
4
Principles and Learning Objectives:
The World Wide Web
• Originally developed as a documentmanagement system, the World Wide Web
has grown to become a primary source of
news and information, an indispensable
conduit for commerce, and a popular hub
for social interaction, entertainment, and
communication
– Describe the World Wide Web and how it
works
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or duplicated, or posted to a publicly accessible website, in whole or in part.
5
Principles and Learning Objectives:
Web Content and Access
• Originally developed as a documentmanagement system, the World Wide Web
has grown to become a primary source of
news and information, an indispensable
conduit for commerce, and a popular hub
for social interaction, entertainment, and
communication
– Explain the use of markup languages, Web
browsers, and Web servers
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or duplicated, or posted to a publicly accessible website, in whole or in part.
6
Principles and Learning Objectives:
Web Applications
• Originally developed as a documentmanagement system, the World Wide Web
has grown to become a primary source of
news and information, an indispensable
conduit for commerce, and a popular hub
for social interaction, entertainment, and
communication
– Identify and briefly describe the process of
creating software applications for the Web
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7
Principles and Learning Objectives:
Web Resources
• The Internet and Web provide numerous
resources for finding information,
communicating and collaborating,
socializing, conducting business and
shopping, and being entertained
– List and describe several sources of
information on the Web
– Describe methods of finding information on
the Web
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8
Principles and Learning Objectives: Online
Communication and Collaboration
• The Internet and Web provide numerous
resources for finding information,
communicating and collaborating,
socializing, conducting business and
shopping, and being entertained
– List and describe several forms of online
communication, along with the benefits and
drawbacks of each, in terms of convenience
and effectiveness
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9
Principles and Learning Objectives:
Web 2.0
• The Internet and Web provide numerous
resources for finding information,
communicating and collaborating,
socializing, conducting business and
shopping, and being entertained
– Explain Web 2.0 and provide examples of
Web 2.0 sites
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10
Principles and Learning Objectives:
Web Resources
• The Internet and Web provide numerous
resources for finding information,
communicating and collaborating,
socializing, conducting business and
shopping, and being entertained
– List and describe sources of online media and
entertainment
– Explain how Web resources are used to
support shopping and travel
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11
Principles and Learning Objectives:
Internet Utilities
• The Internet and Web provide numerous
resources for finding information,
communicating and collaborating,
socializing, conducting business and
shopping, and being entertained
– Briefly name and describe two useful Internet
utilities
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12
Principles and Learning Objectives:
Intranets and Extranets
• Popular Internet and Web technologies
have been applied to business networks in
the form of intranets and extranets
– Explain how intranets and extranets use
Internet and Web technologies, and describe
how the two differ
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13
Why Learn About Telecommunications
and Networks?
• Nearly all career fields utilize the
communications capabilities provided by
telecommunications and networks
including the Internet, intranets, and
extranets
• To be a successful member of any
organization, you must be able to take
advantage of the capabilities that
communications technologies offer you
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An Overview of Telecommunications
• Telecommunications is the electronic
transmission of signals for
communications
• Telecommunications medium: any material
substance that carries an electronic signal
to support communications between a
sending and receiving device
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15
Elements of a Telecommunications
System
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16
Channel Bandwidth
• Channel bandwidth: the rate at which data
is exchanged, measured in bits/sec
• Broadband communications: a relative
term; a telecommunications system that
can transmit data very quickly
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17
Communications Media
• Two broad categories
– Wired (guided) transmission media: signals
are guided along a solid medium
– Wireless: the signal is broadcast over
airwaves as a form of electromagnetic
radiation
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18
Table 4.1 Guided Transmission Media
Types
Media Type
Description
Advantages
Disadvantages
Twisted-pair wire
Twisted pairs of copper
wire, shielded or
unshielded
Used for telephone
service; widely available
Transmission speed
and distance
limitations
Coaxial cable
Inner conductor wire
surrounded by
insulation
Cleaner and faster data
trans- mission than
twisted-pair wire
More expensive
than twisted-pair
wire
Fiber-optic cable
Many extremely thin
strands of glass bound
together in a sheathing;
uses light beams to
transmit signals
Diameter of cable is much
smaller than coaxial cable;
less distortion of signal;
capable of high
transmission rates
Expensive to
purchase and install
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19
Wireless Technologies
• Wireless transmission involves the
broadcast of communications in one of
three frequency ranges
– Radio, microwave, or infrared frequencies
• In some cases, use of wireless
communications is regulated
– The signal must be broadcast within a specific
frequency range to avoid interference with
other wireless transmissions
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20
Table 4.2 Frequency Ranges Used for
Wireless Communications
Technology
Description
Advantages
Disadvantages
Radio
frequency
range
Operates in the
3 kHz–300 MHz range
Supports mobile users;
costs are dropping
Signal highly
susceptible to
interception
Microwave—
terrestrial and
satellite
frequency
range
High-frequency radio
signal (300 MHz–300
GHz) sent through
atmosphere and space
(often involves
communications satellites)
Avoids cost and effort
to lay cable or wires;
capable of high-speed
transmission
Must have unobstructed
line of sight between
sender and receiver;
signal highly susceptible
to interception
Infrared
frequency range
Signals in the 300 GHz–
400 THz frequency range
sent through air as light
waves
Allows you to move,
remove, and install
devices without
expensive wiring
Must have
unobstructed line of
sight between sender
and receiver;
transmission effective
only for short distances
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21
Wireless Communications Options: Near
Field Communication and Bluetooth
• Near field communication (NFC): a very
short-range wireless connectivity
technology
– Designed for consumer electronics, cell
phones, and credit cards
• Bluetooth: a wireless communications
specification that describes how cell
phones, computers, personal digital
assistants, etc., can be interconnected
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Wireless Communications Options: Ultra
Wideband and Wi-Fi
• Ultra wideband (UWB): a short-range
communications that employs extremely
short electromagnetic pulses lasting 50 to
1,000 picoseconds
– Transmission range: 10 to 50 meters
• Wi-Fi: A medium-range wireless
telecommunications technology brand
owned by the Wi-Fi Alliance
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23
Wi-Fi Network
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24
Wireless Communications Options:
Microwave Transmission
• Microwave is a high-frequency (300 MHz–
300 GHz) signal sent through the air
• Common forms of satellite
communications:
– Geostationary satellite
– Low earth orbit (LEO) satellite
– Very small aperture terminal (VSAT)
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25
Satellite Transmission
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26
Wireless Communications Options:
4G and 5G Wireless Communications
• Historical perspective
– 1G (first generation) of wireless
communications standards: originated in the
1980s; based on analog communications
– 2G (second generation) employed fully digital
networks; superseded 1G networks in the
early1990s
– 3G supports wireless voice and broadband
speed data communications in a mobile
environment at speeds of 2 to 4 Mbps
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27
Wireless Communications Options:
4G Wireless Communications
• 4G wireless provides increased data
transmission rates
– Three to 20 times the speed of 3G networks
for mobile devices
• 4G networks are based on Long Term
Evolution (LTE)
• LTE is a standard for wireless
communications for mobile phones based
on packet switching
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28
Wireless Communications Options:
WiMAX
• Worldwide Interoperability for Microwave
Access (WiMAX)
– A 4G alternative
– Based on a set of IEEE 802.16 wireless
metropolitan area network standards
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29
Wireless Communications Options:
5G Wireless Communications
• The next major phase of mobile
telecommunications standards beyond 4G
• Anticipated in the early 2020s
• Expected characteristics
– Higher data transmission rates
– Lower power consumption
– Higher connect reliability and more coverage
– Lower infrastructure costs
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30
Growth in Wireless Data Traffic
• The volume of mobile data traffic reached
8:1 exabytes worldwide in 2012
• Some predict a compound average growth
rate of roughly 44 percent over the next
five years
• Cisco estimates that worldwide wireless
data traffic will grow at a higher average
rate of 66 percent per year from 2013 to
2017
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31
Networks and Distributed Processing
• Computer network: the communications
media, devices, and software needed to
connect two or more computer systems or
devices
• Network nodes: the computers and
devices on the networks
• Organizations can use networks to share
hardware, programs, and databases
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32
Network Topology
• A diagram that indicates how the
communications links and hardware
devices of the network are arranged
• Three most common network topologies
– Star network
– Bus network
– Mesh network
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33
Network Types
• A personal area network (PAN) supports
the interconnection of information
technology close to one person
• A local area network (LAN) connects
computer systems and devices within a
small area (e.g., an office or a home)
• A metropolitan area network (MAN)
connects users and their devices in an
area that spans a campus or city
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34
Typical LAN
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35
Network Types: WANs
• A wide area network (WAN) connects
large geographic regions
• WANs consist of:
– Computer equipment owned by the user
– Data communications equipment and
telecommunications links provided by various
carriers and service providers
• Communications may involve transborder
data flow
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36
Basic Processing Alternatives
• Centralized processing occurs in a single
location or facility
• Decentralized processing involves devices
placed at various remote locations; the
devices do not communicate with one
another
• Distributed processing uses devices
placed at remote locations; devices are
connected to each other via a network
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37
Client/Server Systems
• Client/server architecture features multiple
computer platforms dedicated to special
functions, e.g., database management,
printing, or communications
• A client is any computer that sends
messages requesting services from the
servers on the network
• A database server sends only the data that
meets a specific query—not the entire file
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38
Table 4.4 Common Telecommunications
Devices
Device
Modem
Fax modem
Multiplexer
PBX
Front-end
processor
Switch
Bridge
Router
Gateway
Function
Translates data from a digital form (as it is stored in the computer) into an analog signal that can be
transmitted over ordinary telephone lines.
Facsimile devices, commonly called fax devices, allow businesses to transmit text, graphs,
photographs, and other digital files via standard telephone lines. A fax modem is a very popular device
that combines a fax with a modem, giving users a powerful communications tool.
Allows several telecommunications signals to be transmitted over a single communications medium at
the same time, thus saving expensive long-distance communications costs.
A communications system that manages both voice and data transfer within a building and to
outside lines. In a PBX system, switching PBXs can be used to connect hundreds of internal phone
lines to a few phone company lines.
Special-purpose computer that manages communications to and from a computer system serving many
people.
Uses the physical device address in each incoming message on the network to determine which output
port it should forward the message to reach another device on the same network
Connects one LAN to another LAN that uses the same telecommunications protocol.
Forwards data packets across two or more distinct networks toward their destinations through a process
known as routing. Often an Internet service provider (ISP) installs a router in a subscriber’s home that
connects the ISP’s network to the network within the home.
A network device that serves as an entrance to another network.
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Telecommunications Software
• Network operating system (NOS): systems
software that controls the computer
systems and devices on a network
• Network management software:
– Protects software from being copied,
modified, or downloaded illegally
– Locates telecommunications errors and
potential network problems
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40
Software Defined Networking (SDN)
• An emerging approach to networking
• Allows network administrators to have
programmable central control of the
network via a controller without requiring
physical access to all the network devices
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41
Use and Functioning of the Internet
• The Internet is international scope with
users on every continent
• Internet sites have a profound impact on
world politics
• Internet censorship
– Some countries try to control Internet content
and services
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42
Internet Growth: Number of Internet Hosts
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43
Distribution of Internet Users
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44
Use and Functioning of the Internet
(cont’d.)
• ARPANET
– Ancestor of the Internet
– Project started by the U.S. Department of
Defense (DoD) in 1969
• Internet Protocol (IP) enables computers
to route communications traffic from one
network to another
• Internet2 is a faster alternative Internet
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45
How the Internet Works
• Backbone: one of the Internet’s highspeed, long-distance communications
links
• Transmission Control Protocol (TCP): the
widely used transport layer protocol that
most Internet applications use with IP
• IP address: a 64-bit number that identifies
a computer on the Internet
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46
Routing Messages Over the
Internet
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47
How the Internet Works (cont’d.)
• Uniform Resource Locator (URL): a Web
address that specifies the exact location of
a Web page using letters and words that
map to an IP address and a host location
• Internet Corporation for Assigned Names
and Numbers (ICANN) is responsible for
managing IP addresses and Internet
domain names
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48
Table 4.5 U.S. Top-Level Domain
Affiliations
Affiliation ID
Affiliation
Number of Hosts
com
Business sites
112,259,193
edu
Post-secondary educational sites
7,500
gov
Government sites
2,174
net
Networking sites
15,221,763
org
Nonprofit organization sites
10,395,604
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49
Several Ways to Access the Internet
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Cloud Computing
• A computing environment in which
software and storage are provided as an
Internet service and accessed with a Web
browser
• Advantages to businesses
– Businesses can save on system design,
installation, and maintenance
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51
Cloud Computing (cont’d.)
• Methods of deployment
– Public cloud: service providers offer their
cloud-based services to the general public
– Private cloud: cloud technology is used within
the confines of a private network
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52
The World Wide Web
• Developed by Tim Berners-Lee at CERN
• Originally conceived of as an internal
document-management system
• The Web has grown to become:
– A primary source of news and information
– An indispensable conduit for commerce
– A popular hub for social interaction,
entertainment, and communication
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53
How the Web Works
• The Internet
– The infrastructure on which the Web exists
– Made up of computers, network hardware
such as routers and fiber-optic cables,
software, and the TCP/IP protocols
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54
How the Web Works: Information and
Services
• Web components combining to deliver
information and services over the Internet
– Server and client software
– The Hypertext Transfer Protocol (http)
– Standards
– Mark-up languages
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55
How the Web Works:
A Hyperlink-Based System
• Hyperlink: highlighted text or graphics in a
Web document that, when clicked, opens
a new Web page
• Web browser: Web client software used to
view Web pages
– Examples: Internet Explorer, Firefox, Chrome,
and Safari
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56
How the Web Works:
Web Sites and Web Pages
• Web site: a collection of pages on one
particular topic, accessed under one Web
domain
• Hypertext Markup Language (HTML): the
standard page description language for
Web pages
• HTML tags tell the Web browser how to
format text and elements to be inserted
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57
How the Web Works: Web Sites and Web
Pages (cont’d.)
• Cascading Style Sheets (CSS): a markup
language that defines the visual
appearance of content in a Web page
• Extensible Markup Language (XML): a
markup language designed to transport
and store data on the Web
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58
Web Programming Languages
• Java
– An object-oriented programming language
from Sun Microsystems based on C++
– Allows small programs (applets) to be
embedded within an HTML document
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59
Web Services
• Standards and tools that streamline and
simplify communication among Web sites
• XML
– The key to Web services
– Used within a Web page to describe and
transfer data between Web service
applications
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60
Developing Web Content and Applications
• Popular tools for creating Web pages and
managing Web sites
• Adobe Dreamweaver CC, RapidWeaver 5,
Microsoft Expression Web, and Nvu
• Mashup: two or more Web applications
combined into a new service
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61
Internet and Web Applications
•
•
•
•
•
•
Web 2.0 and the social Web
Online information sources
Search engines and Web research
Web portals
Blogging and podcasting
Online media and entertainment
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62
Internet and Web Applications (cont’d.)
• Shopping online
• Travel, geolocation, and navigation
• Internet utilities
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63
Web 2.0 and the Social Web
• Web 2.0: the Web as a computing platform
that supports software applications and
the sharing of information among users
• Social networking Web sites enable users
to share information abut themselves and
to find, meet, and converse with others
• Rich Internet applications are available
that run in a Web browser and do not
require local installation
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64
Online Information Sources
• News
– The Web is a powerful tool for keeping
informed about local, state, national, and
global news
• Education and training
– Web is ideally suited as a tool for sharing
information and a primary repository of
information on all subjects
– Distance education offers classes via the Web
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65
Online Information Sources: Business and
Job Information
• Providing information about a businesses
and its products via Web site and social
media increases the company’s exposure
and reputation
• The Web is an excellent source of jobrelated information
– Examples: www.linkedin.com,
www.monster.com, www.hotjobs.com, and
www.careerbuilder.com
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66
Search Engines and Web Research
• Search engine
– Information on the Web is found by specifying
keywords
– The market is dominated by Google
– Spiders are automated programs that scour
the Web
• Wikipedia:
– Is an online encyclopedia
– Entries can be inaccurate and biased
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67
Table 4.6 Using Operators in Google Web
Searches
Keywords and
Operator Entered
vacation Hawaii
Search Engine Interpretation
The words “vacation” and “Hawaii”
Maui OR Hawaii
Either the word “Maui” or the word “Hawaii”
“To each his own”
The exact phrase “To each his own”
virus -computer
The word virus, but not the word computer
Star Wars Episode +I
The movie title “Star Wars Episode,” including the Roman
numeral I
Loan information for both the word “auto” and its
synonyms, such as “truck” and “car”
~auto loan
define:computer
Definitions of the word “computer” from around the Web
red * blue
The words “red” and “blue” separated by one or more words
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68
Web Portals
• Web portal: a Web page that combines
useful information and links and acts as an
entry point to the Web
• Vertical portals are pages that provide
information and links for special-interest
groups
• Corporate portals provide access to workrelated resources
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or duplicated, or posted to a publicly accessible website, in whole or in part.
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Web Portals: Communication and
Collaboration
• Email
• Instant messaging
• Microblogging, status updates, and news
feeds
– Twitter is a Web application that allows
members to report on what they are doing
throughout the day
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or duplicated, or posted to a publicly accessible website, in whole or in part.
70
Communication and Collaboration
(cont’d.)
• Conferencing
– The Internet has made it possible for those
involved in teleconferences to share computer
desktops
– GoToMeeting enables employees to attend
training without leaving their assigned stations
– Telepresence systems use high-resolution
video and audio with high-definition displays
• Apple iChat and Skype allow video chats
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or duplicated, or posted to a publicly accessible website, in whole or in part.
71
Blogging and Podcasting
• Web log (blog): a Web site that people can
create and use to write about their
observations, experiences, and opinions
on a wide range of topics
• Video log (vlog): blogging with video
content
• Podcast: an audio broadcast over the
Internet
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or duplicated, or posted to a publicly accessible website, in whole or in part.
72
Online Media and Entertainment
• Content streaming: a method of
transferring large media files over the
Internet
– The data stream of voice and pictures plays
continuously as the file is being downloaded
© 2016 Cengage Learning®. All Rights Reserved. May not be scanned, copied
or duplicated, or posted to a publicly accessible website, in whole or in part.
73
Online Media and Entertainment: Music
• The Internet and the Web have made
music more accessible than ever
– Artists distribute their songs through online
radio, subscription services, and download
services
• Downloaded music may employ Digital
Rights Management (DRM) technology to
limit the user’s ability to make copies
© 2016 Cengage Learning®. All Rights Reserved. May not be scanned, copied
or duplicated, or posted to a publicly accessible website, in whole or in part.
74
Online Media and Entertainment: Movies,
Video, and Television
• Hulu Web site and Internet-based
television platforms (e.g., Netflix and
Joost) provide television programming
• Vudu provides access to online movies
• YouTube supports the online sharing of
user-created videos
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or duplicated, or posted to a publicly accessible website, in whole or in part.
75
Online Media and Entertainment: E-Books
and Audio Books
• An e-book is a book stored digitally
• Apple’s iPad changed the eBook industry
by providing a form factor that is similar to
but larger than the Kindle
• There are dozens of eBook formats; some
are proprietary
• Audio books have become more popular
due to the popularity of iPods and iPhones
© 2016 Cengage Learning®. All Rights Reserved. May not be scanned, copied
or duplicated, or posted to a publicly accessible website, in whole or in part.
76
Online Games and Entertainment
• Video games are expected to generate
over $100 billion annually by 2017
• The market for Internet gaming is very
competitive and constantly changing
• Many video games are available online
• Game consoles such as the Wii, Xbox,
and PlayStation provide multiplayer
options for online gaming
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or duplicated, or posted to a publicly accessible website, in whole or in part.
77
Shopping Online
• Shopping on the Web can be convenient,
easy, and cost effective
• E-tail stores:
– Are online versions of retail stores
– Provide access to many products that may be
unavailable in local stores
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or duplicated, or posted to a publicly accessible website, in whole or in part.
78
Shopping Online (cont’d.)
• Online clearinghouses, Web auctions, and
marketplaces provide a platform for
businesses and individuals to sell their
products and belongings
• www.eBay.com is the most popular online
auction or marketplace
• Businesses benefit from shopping online
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or duplicated, or posted to a publicly accessible website, in whole or in part.
79
Travel, Geolocation, and Navigation
• The Web has had a profound effect on the
travel industry and the way people plan
and prepare for trips
• Mapping and geolocation tools
– MapQuest
– Google Maps
– Bing Maps
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or duplicated, or posted to a publicly accessible website, in whole or in part.
80
Travel, Geolocation, and Navigation
(cont’d.)
• Geographic information systems (GIS)
provide geographic information layered
over a map
• Geo-tagging is possible on Twitter and
Facebook
• Geolocation information poses a risk to
privacy and security
© 2016 Cengage Learning®. All Rights Reserved. May not be scanned, copied
or duplicated, or posted to a publicly accessible website, in whole or in part.
81
Internet Utilities
• Telnet: a network protocol that enables
users to log on to networks remotely over
the Internet
• Secure shell (SSH) provides Telnet
functionality through a more secure
connection
• File Transfer Protocol (FTP) supports file
transfers between a host and a remote
computer
© 2016 Cengage Learning®. All Rights Reserved. May not be scanned, copied
or duplicated, or posted to a publicly accessible website, in whole or in part.
82
Intranets and Extranets
• Intranet: an internal corporate network
built using Internet and World Wide Web
standards and technologies
• Extranet: a network based on Web
technologies that links selected resources
of a company’s intranet with its customers,
suppliers, or other business partners
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or duplicated, or posted to a publicly accessible website, in whole or in part.
83
Table 4.7 Summary of Internet, Intranet,
and Extranet Users
Type
Users
Need User ID and Password?
Internet
Anyone
No
Intranet
Employees and managers
Yes
Extranet
Business partners
Yes
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or duplicated, or posted to a publicly accessible website, in whole or in part.
84
Intranets and Extranets (cont’d.)
• Virtual private network (VPN): a secure
connection between two points on the
Internet
• Tunneling: the process by which VPNs
transfer information by encapsulating
traffic in IP packets over the Internet
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or duplicated, or posted to a publicly accessible website, in whole or in part.
85
Summary – Principle 1
• Telecommunications refers to the
electronic transmission of signals for
communications, including telephone,
radio, and television
• The elements of a telecommunications
system include the sending and receiving
devices, modems, the transmission media,
and the message
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or duplicated, or posted to a publicly accessible website, in whole or in part.
86
Summary – Principle 1 (cont’d.)
• Telecommunications media can be divided
into two broad categories: guided
transmission media and wireless media
• Network topology indicates how the
communications links and hardware
devices of the network are arranged
• Types of networks based on physical
distance between nodes are PAN, LAN,
MAN, or WAN
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or duplicated, or posted to a publicly accessible website, in whole or in part.
87
Summary – Principle 2
• The Internet has users on every continent
• People can connect to the Internet
backbone in several ways
• Cloud computing refers to a computing
environment where software and storage
are provided as an Internet service and
accessed with a Web browser
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or duplicated, or posted to a publicly accessible website, in whole or in part.
88
Summary – Principle 3
• The Web is a collection of tens of millions
of servers that work together as one in an
Internet service providing information via
hyperlink technology to billions of users
worldwide
• Web pages are accessed and viewed
using a Web browser, e.g., Firefox
• The Web is becoming a computing
platform in and of itself
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or duplicated, or posted to a publicly accessible website, in whole or in part.
89
Summary – Principle 4
• The Web has become the most popular
medium for distributing and accessing
information
• A search engine is a valuable tool that
enables you to find information on the
Web by specifying keywords
• A Web portal is a Web page that combines
useful information and links and acts as an
entry point to the Web
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or duplicated, or posted to a publicly accessible website, in whole or in part.
90
Summary – Principle 5
• An intranet is an internal corporate
network built using Internet and World
Wide Web standards and products
• An extranet is a network that links selected
resources of the intranet of a company
with its customers, suppliers, or other
business partners
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or duplicated, or posted to a publicly accessible website, in whole or in part.
91