Chapter 1
Living in a Network-Centric World
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Networks Supporting The Way We Live
• Data networks that were once the transport of information for
businesses are now also used to improve our quality of life
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check bank balance and pay bills electronically
find the least-congested route to a destination
use instant messaging and chat for both personal and business use
post and share your photographs, home videos and experiences
shop and sell at online auctions
use Internet phone services
– obtain health information
and nutritional advice
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Today’s Popular Communication Tools
• Instant messaging (IM)
– real-time text communication between two or more users
– also supports voice, photo and video sharing, and file transfers
• Blogs or weblogs
– individuals publish their personal opinions and thoughts about any
conceivable topic
– allow unfiltered and unedited publication of ideas from anyone
• Podcasting
– website that contains audio files available for downloading
• Wikis
– publicly created web content that groups of people can edit and view
together
– organizations and individuals build their own wikis to capture collected
knowledge for use as collaboration tools
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Examples of Communication Tools
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Networks Supporting The Way We Learn
• Traditional learning methods make use of textbooks and instructorled classes
• Courses delivered using networks or Internet resources are often
called online learning experiences or e-learning
• Online courses can contain voice, data and video
– available to the students at any time from any place
• Blended courses can combine instructor-led classes with online
courseware to provide the best of both delivery methods
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Global Online Learning Experience
• The instructor provides a syllabus and establishes a preliminary
schedule for completing the course content
• The way we learn is supported by courseware delivered over the
data network
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Learning by Sharing and Exploring
• Students can communicate with the instructor and fellow students
using online tools
– bulletin/discussion boards, chat rooms and instant messaging
• Links provide access to learning resources outside the courseware
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Online Courseware Administration
• Improved management and administration of courses
– enrollment, assessment delivery and grade books
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Benefits of Online Courseware
• Current and accurate training materials
– collaboration among vendors, equipment manufacturers and training
providers ensures that the courseware is up to date with the latest
processes and procedures
• Availability of training to a wide audience
– online training is not dependent on travel schedules, instructor
availability, or physical class size
• Consistent quality of instruction
– quality of instruction does not vary as it would if different instructors
were delivering an in-person lesson
• Cost reduction
– facilities to support in-person training can be reduced or eliminated
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Networks Supporting The Way We Work
• Business applications can be accessed remotely as if employees
were on site
• Workers in any location can reach each other and access multiple
resources on the network
Accessing Multiple Resources
Remote Access
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Networks Supporting The Way We Play
• Explore places of interest interactively or preview actual destinations
before a trip
• Posting photographs about an event online for others to view
• Participate in online games
• Preview motion pictures
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Basic Characteristics of Communication
• Rules or agreements to govern the conversation are first established
– these rules, called protocols, must be followed in order for the message
to be successfully delivered and understood
• A message with important information may need a confirmation that
the message has been received and understood
• As a message moves through the network, many factors can
prevent the message from reaching the recipient or distort its
intended meaning
– internal or external factors
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External Factors
• The quality of the pathway between the sender and the recipient
• The number of times the message has to change form
• The number of times the message has to be redirected or
readdressed
• The number of other messages being transmitted simultaneously on
the communication network
• The amount of time allocated for successful communication
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Internal Factors
• The size of the message
– it is more difficult to deliver a large bulky message, quickly and without
damage, than it is to deliver a number of smaller, less complex
messages
• The complexity of the message
• The importance of the message
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Four Elements of a Network
• Rules or agreements to govern the messages are sent, directed,
received and interpreted
• The messages or units of information that travel from one device to
another
• A means of interconnecting these devices – a medium that can
transport the messages from one device to another
• Devices on the network that exchange messages with each other
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Rules
• Rules govern every step of the process, from the way cables are
designed to the way the digital signals are sent
• These rules are called protocols, e.g. TCP/IP protocol stack
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Messages
• Message is a generic term that encompasses text, voice or video
information
• The message must be converted to bits, binary coded digital signals,
before they are transmitted on the medium
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Medium
• Physically carries the message
• Connects the devices
• Can be wired or wireless
UTP cables
Wired connections
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wireless
router
Wireless connections
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Devices
• End-user devices
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• Networking devices
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desktop computer
server
notebook (or laptop)
IP phone
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LAN switch
firewall
router
wireless router
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Common Data Network Symbols
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Non-Converged Networks
• In the past, every one of the services required a different technology
to carry its particular communication signal
• Each service has its own set of rules and standards
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Converged Networks
• Convergence occurs when telephones, broadcasts (radio and TV),
and computer communications all use the same rules, devices and
media to transport messages
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Network Architecture
• Refers to the conceptual plans on which a physical
network is built
• Must support a wide range of applications and services
• Four basic characteristics of the network architecture
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fault tolerance
scalability
quality of service
security
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Fault Tolerance
• A fault tolerant network limits the impact of hardware or software
failure
– recover quickly when a failure occurs
– depend on redundant links, or paths, between the source and
destination of a message
– redundant connections allow for alternate paths
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Circuit Switched Connection-Oriented Networks
• A physical, dedicated path or circuit is temporary setup between the
source and destination
• The circuit is maintained for the duration of the call
• Early circuit-switched networks do not dynamically recover from
drop circuits
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Packet Switched Connectionless Networks
• The entire message is broken into packets which are addressed and
numbered
• Any packets can be sent through the network using any available
path
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Scalability
• A scalable network can expand quickly to support new users and
applications without impacting the performance of the service being
delivered to existing users
• Depends on a hierarchical layered design for the physical
infrastructure and logical architecture
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Internet Structure
• The Internet is a hierarchical structure of interconnected networks
• Many individual networks that provide Internet connectivity
cooperate to follow accepted standards and protocols
– new products can integrate with and enhance the existing infrastructure
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Quality of Service (QoS)
• QoS refers to the mechanism that manage congested network traffic
• Congestion is caused when the demand on the network exceeds the
available capacity
• Some constraints on network resources cannot be avoided
– technology limitations
– cost
– local availability of highbandwidth services
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QoS Classification
• Prioritize which types of data packets must be delivered at the
expense of other types of packets that can be delayed or dropped
– use queues to prioritize traffic
• Classify applications in categories based on specific quality of
service requirements
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Prioritizing Network Traffic
• Delay-sensitive (or time sensitive) communication
– increase priority for services like voice or video transmission
• Delay-insensitive (or non-time sensitive) communication
– decrease priority for web page retrieval or e-mail
• High importance to organization
– increase priority for business transaction data or production control
• Undesirable communication
– decrease priority or block unwanted activity such as gaming
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Security
• The Internet has become a widely accessible means of business
and personal communications
– the same environment that attracts legitimate business, however, also
attracts scam artists and vandals
• Compromising the integrity of company assets could lead to serious
business and financial repercussions
• Tools and procedures are
being implemented to
combat inherent security
flaws in the network
architecture
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Network Security Concerns
• Network infrastructure security
– physical securing of devices that provide network connectivity and
preventing unauthorized access to the management software that
resides on them
• Content security
– protecting the information contained within the packets being
transmitted over the network and the information stored on network
attached devices
– tools to provide security for the content of individual messages must be
implemented on top of the underlying protocols
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Consequences of Security Breach
• Network outage causing a loss of communications and
transactions occurring, with consequent loss of business
• Misdirection and loss of personal or business funds
• Theft of intellectual property such as project bids and strategic
plans and used by a competitor
• Exposure of confidential customer data, which may result in
loss of market confidence in the business
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Security Measures
• Prevent unauthorized disclosure or theft of information
– ensure confidentiality
• Prevent unauthorized modification of information
– maintain communication integrity
• Prevent denial of service (DoS)
– ensure availability
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Confidentiality, Integrity and Availability
• Ensuring confidentiality
– allowing only the intended and authorized users to read the data
– a strong system for user authentication
– encrypting the content
• Maintaining communication integrity
– data integrity is the assurance that the information has not been altered
in transmission, from source to destination
– source integrity is the assurance that the identity of the sender has been
validated
– using digital signatures and hashing algorithms
• Ensuring availability
– resources are available to authorized users
– virus software and firewalls are used to combat virus and DoS attacks
– building fully redundant network infrastructures
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Trends in Networking
• Increasing number of mobile users
– a demand for more mobile connectivity to data networks
• New and more capable devices
– functions performed by cell phones, personal digital assistants,
organizers and pagers are converging into single handheld devices with
continuous connectivity to providers of services and content
• Increased availability of services
– new services are introduced and
older services are enhanced to meet
user demands
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