ACM 511ACM 511

Introduction to Computer Introduction to Computer NetworksNetworks

Computer NetworksComputer Networks

Intranet / ExtranetIntranet / Extranet

IntranetsIntranets, private networks in use by just one , private networks in use by just one company, enable businesses to communicate company, enable businesses to communicate and perform transactions among global and perform transactions among global employee and branch locations. employee and branch locations.

Companies develop Companies develop extranetsextranets, or extended , or extended internetworks, to provide suppliers, vendors, and internetworks, to provide suppliers, vendors, and customers limited access to corporate data to customers limited access to corporate data to check order status, inventory, and parts lists.check order status, inventory, and parts lists.

CommunicationCommunication

Before beginning to communicate with each other, Before beginning to communicate with each other, we establish rules or agreements to govern the we establish rules or agreements to govern the conversation. These rules, or conversation. These rules, or protocolsprotocols, must be , must be followed in order for the message to be followed in order for the message to be successfully delivered and understood. Among successfully delivered and understood. Among the protocols that govern successful human the protocols that govern successful human communication are:communication are:

An identified sender and receiverAn identified sender and receiver Agreed upon method of communicating (face-to-face, Agreed upon method of communicating (face-to-face,

telephone, letter, photograph)telephone, letter, photograph) Common language and grammarCommon language and grammar Speed and timing of deliverySpeed and timing of delivery Confirmation or acknowledgement requirements Confirmation or acknowledgement requirements

CommunicationCommunication

External FactorsExternal Factors

The external factors affecting communication are related The external factors affecting communication are related to the complexity of the network and the number of to the complexity of the network and the number of devices a message must pass through on its route to its devices a message must pass through on its route to its final destination. External factors affecting the success of final destination. External factors affecting the success of communication include:communication include:

The quality of the pathway between the sender and the The quality of the pathway between the sender and the recipientrecipientThe number of times the message has to change form The number of times the message has to change form The number of times the message has to be redirected The number of times the message has to be redirected or readdressedor readdressedThe number of other messages being transmitted The number of other messages being transmitted simultaneously on the communication networksimultaneously on the communication networkThe amount of time allotted for successful The amount of time allotted for successful communicationcommunication

Common Data Network SymbolsCommon Data Network Symbols

Internal FactorsInternal Factors

Internal factors affecting the successful Internal factors affecting the successful communication across the network include:communication across the network include:

The size of the messageThe size of the messageThe complexity of the messageThe complexity of the messageThe importance of the messageThe importance of the message

Three important terms: Three important terms: Bandwidth Bandwidth Congestion Congestion DelayDelay

Network ConnectionsNetwork Connections

Service/ProtocolService/Protocol

Transferring DataTransferring Data

Multiple NetworksMultiple Networks

Converged NetworksConverged Networks

Fault ToleranceFault Tolerance

ScalabilityScalability

Quality of ServiceQuality of Service

SecuritySecurity

Circuit SwitchingCircuit Switching

Packet SwitchingPacket Switching

Internet StructureInternet Structure

ConvergenceConvergence

QueuesQueues

Quality of ServiceQuality of Service

Quality of ServiceQuality of Service

Time-sensitive communication - increase priority Time-sensitive communication - increase priority for services like telephony or video distribution.for services like telephony or video distribution.Non time-sensitive communication - decrease Non time-sensitive communication - decrease priority for web page retrieval or e-mail.priority for web page retrieval or e-mail.High importance to organization - increase High importance to organization - increase priority for production control or business priority for production control or business transaction data.transaction data.Undesirable communication - decrease priority Undesirable communication - decrease priority or block unwanted activity, like peer-to-peer file or block unwanted activity, like peer-to-peer file sharing or live entertainment.sharing or live entertainment.

ConfidentialityConfidentiality

Ensuring ConfidentialityEnsuring Confidentiality

Data privacy is maintained by allowing only the intended Data privacy is maintained by allowing only the intended and authorized recipients - individuals, processes, or and authorized recipients - individuals, processes, or devices - to read the data. devices - to read the data.

Having a strong system for user authentication, Having a strong system for user authentication, enforcing passwords that are difficult to guess, and enforcing passwords that are difficult to guess, and requiring users to change them frequently helps restrict requiring users to change them frequently helps restrict access to communications and to data stored on network access to communications and to data stored on network attached devices. Where appropriate, attached devices. Where appropriate, encryptingencrypting content content ensures confidentiality and minimizes unauthorized ensures confidentiality and minimizes unauthorized disclosure or theft of information.disclosure or theft of information.

Communication IntegrityCommunication Integrity Maintaining Communication IntegrityMaintaining Communication Integrity

Data integrity means having the assurance that the Data integrity means having the assurance that the information has not been altered in transmission, from information has not been altered in transmission, from origin to destination. Data integrity can be compromised origin to destination. Data integrity can be compromised when information has been corrupted - wilfully or when information has been corrupted - wilfully or accidentally - before the intended recipient receives it.accidentally - before the intended recipient receives it.

Source integrity is the assurance that the identity of the Source integrity is the assurance that the identity of the sender has been validated. Source integrity is sender has been validated. Source integrity is compromised when a user or device fakes its identity compromised when a user or device fakes its identity and supplies incorrect information.and supplies incorrect information.

The use of The use of digital signaturesdigital signatures, , hashing algorithmshashing algorithms and and checksum mechanismschecksum mechanisms are ways to provide source and are ways to provide source and data integrity across a network to prevent unauthorized data integrity across a network to prevent unauthorized modification of information.modification of information.

AvailabilityAvailability

Ensuring AvailabilityEnsuring Availability

Ensuring confidentiality and integrity are irrelevant if Ensuring confidentiality and integrity are irrelevant if network resources become over burdened, or not network resources become over burdened, or not available at all. Availability means having the assurance available at all. Availability means having the assurance of timely and reliable access to data services for of timely and reliable access to data services for authorized users. Resources can be unavailable during a authorized users. Resources can be unavailable during a Denial of Service (DoS) attack or due to the spread of a Denial of Service (DoS) attack or due to the spread of a computer virus. Network firewall devices, along with computer virus. Network firewall devices, along with desktop and server anti-virus software can ensure desktop and server anti-virus software can ensure system reliability and the robustness to detect, repel, and system reliability and the robustness to detect, repel, and cope with such attacks. Building fully redundant network cope with such attacks. Building fully redundant network infrastructures, with few single points of failure, can infrastructures, with few single points of failure, can reduce the impact of these threats.reduce the impact of these threats.

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