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This Could Happen to You
Dee needs to decide where she will run the blogIt needs to be private to maintain a competitive advantage
Sales people need to have easy access
Passwords may be needed to restrict access
Emerson has a private networkProtected by firewall
Employees access through VPN (Virtual Private Network) Can be protected from unauthorized access
Sales people can access with same password they already use
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Study Questions
Q1. What is a computer network?
Q2. What are the components of a LAN?
Q3. What are the alternatives for a WAN?
Q4. How does encryption work?
Q5. What is the purpose of a firewall?
Q6. What is a VPN and why is it important?
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Q1. What Is a Computer Network?
NetworkCollection of computers
Communicate with one another over transmission line
Three basic typesLocal area network (LAN)
Wide area network (WAN)
Internet
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LAN
Connects computers residing in single location2 to several hundred computers
One geographic area
Communication lines can be placed where the organization wants
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WAN
Connect computers in different geographical areasTwo or more cities
Uses communication networks from vendorsLicensed by government
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Internet
Network of networks
Connect LANs, WANs, and other internets
Private networks of networks
Use a variety of communication methods and conventionsSeamless flow of data provided by layered protocol
Set of rules that communicating devices follow
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Local area networkComputers connected on single company siteUsually located within half mile areaProperty controlled by company operating network
Company can run cabling as necessary
ComponentsSwitch
Special purpose computer that receives and transmits messages
Network Interface Card (NIC) Hardware that connects each device’s circuitry to the cable Onboard NIC or card that fits into an expansion slot
Q2. What Are the Components of a LAN?
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NIC Devices
MAC addressUnique identifier
Media connectionsUnshielded twisted pair (UTP) cable
RJ-45 connector
Optical fiber cables Light rays reflected inside glass core surrounded by cladding
Uses ST and SC connectors
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IEEE 802.3 Protocol
Ethernet protocol standardSpecifies hardware characteristics
Describes how messages are packages
Determines how messages are processed
Operates at Layers 1 and 2 of TCP/IP-OSI architecture
Personal computers usually support 10/100/1000 Ethernet
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LANs with Wireless Connections
Wireless NIC (WNIC)
LAN operationNICs operate on 802.3 protocol
WNICs operate on 802.11 protocol
WNICS connect to Access Point (AP) AP processes both standards
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Q3. What Are the Alternatives for a WAN?
WANs connect computers at separate sitesNo cabling between sites
Cable connections made through licensed communications companies
Internet service provider (ISP)Provides legitimate Internet address
Serves as gateway to Internet
Pay for Internet
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Connecting to the ISP
Connections made through:Regular telephone lines
Use of DSL line
Cable TV lines
All require digital data to be converted to analogModem makes conversion
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MIS In Use: Larry Jones (Student) Network Services
Larry set up LAN networks
Realized that he had to offer supportCustomers had problems
Customers needed to add more devices
Coupled installation with support packageExtra charges for support beyond normal wear and tear
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Dial-Up Modems
Handles conversion between analog and digital
Connection made by dialing ISP
Maximum transmission speed of 56 kbps
Modulation governed by V.34, V.90. or V.92 standards
PPP (Point-to-Point Protocol) controls message packaging and handling
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DSL Modems
Operates over telephone lines
Do not interfere with voice telephone service
Faster data transmission than dial-up
Connection always maintained
Use their own Layer 1 and 2 protocols
Download and upload speeds varyAsymmetric digital subscriber lines (ADSL)
Symmetrical digital subscriber lines (SDSL)
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Cable Modems (1)
Provide high-speed data transmission
Use cable television linesHigh-capacity optical fiber cable run to neighborhood
distribution center
Television cables connect at distribution center and runs to subscribers
Does not interfere with television transmission
Up to 500 subscribers connected at each center Performance varies based on number connected
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Cable Modems (2)
Download speed up to 10Mbps, upload up to 256 kbps
Operate with Layer 1 and 2 protocols
SpeedsNarrowband
Transmission speeds less then 56 kbps
Broadband Transmission speeds in excess of 256 kbps
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Networks of Leased Lines
WAN connects computers located at geographically distributed sites
Access devices connect sites to transmissionSwitch
Router
Alternative is leasing linesT1, T3
Set up as a point-to-point line
Only predefined sites can use leased lines
Provide low cost per bit transmitted
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Nathan Myhrvoid claimed that:Humans cannot think exponentially
Think of fastest linear change and extrapolate from there
Was writing about growth of magnetic storage
Also applies to growth of computer network phenomena
Ubiquitous and cheap connectivity is growing exponentiallyWhat are the threats and opportunities?
Problem Solving Guide: Thinking Exponentially Is Not Possible, but…
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Exponential Phenomena Brings Changes
Technology doesn’t drive people to do new things
Social progress occurs in small, evolutionary, adaptive steps
Technology may enable a capability, but people may not want itPeople want to do what they are doing more easily
They want to solve existing problems
Respond by hedging your bets
The more time involved, the more potential for error
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Public Switched Data Network (PSDN)
Network of computers and leased linesDeveloped and maintained by vendor
Time leased on network
Utility that supplies network for other companies to leaseEach site leases line to connect to PSDN network at
access point Point of presence (POP)
Saves setup and maintenance activities
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PSDN Protocols
Frame relayProcess traffic at 56 kbps to 40 Mbps
Simplest and easiest to support
Asynchronous transfer mode (ATM)Process speeds from 1 to 156 Mbps
EthernetOperates at speeds of 10 to 40 Gpbs
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Criteria for Comparing WANs (1)
CostsSetup costs
Examples: costs of acquiring lines and equipment
Operational costs Examples: lease fees, ISP charges, training
Maintenance costs Examples: periodic maintenance, repair, upgrades
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Criteria for Comparing WANs (2)
PerformanceSpeed
Latency
Availability
Loss rate
Transparency
Performance guarantees
Growth potential
Length of contract commitment
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Q4. Security Guide: How Does Encryption Work? (1)
EncryptionProcess of transforming clear text into coded text
Used for secure storage or communication
Uses algorithms DES, 3DES, AES
KeyUsed to encrypt data
Algorithm applies key to produce coded message Symmetric encryption
Asymmetric encryption
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Security Guide: How Does Encryption Work? (2)
Public key / Private keyPublic key used to encrypt messagesPublic key sent to other party to encode messages to be sent backDecoded with private keyComplex and slow
HTTPSSecure communication over Internet
Encrypted using SSL (Secure Socket Layer) / TLS (Transport Layer Security) protocol
Encodes messages using Web site’s public key, decoded with private key
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Q5. What Is the Purpose of a Firewall?
Computer device that prevents unauthorized network access
May be special-purpose computer or program
Organizations may have multiple firewallsPerimeter firewalls sit outside organizational network
Internal firewalls are inside network
Packet-filtering firewalls examine source address, destination address, and other data before allowing message to pass
May filter both incoming and outgoing messages
Access control list (ACL) encodes rules stating what packets are allowed or prohibited
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Q6. What Is a VPN and Why Are VPNs Important?
Virtual private networkUses Internet or private network to create appearance
of point-to-point connections
Uses public Internet to create appearance of private network
Client and server have point-to-point connection called tunnel
Private pathway over shared network
Secure, encrypted communications
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Ethics Guide: Human Networks Matter More
Six degrees of separationOften unaware of those in the chain
Build personal human networks for successSomeone, somewhere that you need to know or will need to know
Meet people at professional and social situations Pass out and collect cards
Converse to expand network
Look for new channels
Social network theory Weak and strong ties
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How Does the Knowledge in This Chapter Help Dee? (1)
Dee and salespeople use thin client computersDee creates blog entries on Web pages using Moveable Type
Salespeople use pages served by Moveable Type
Client computers contain VPN client softwareInteracts with VPN server via Internet
Secure, private connections
Firewalls stop traffic not addressed to VPN server
Salespeople know how to use VPN
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How Does the Knowledge in This Chapter Help Dee? (2)
IT department cannot schedule resources to setup blog server in timely fashionWill not allow outside person to do setup
Would then have access to system
Consultant can create server on unprotected test serverCan be copied onto network server after acceptance
Requires some internal IT labor
Consultant could include Trojan horse virus or malware Install only software from known sources
Code should not reside on production server
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How Does the Knowledge in This Chapter Help Dee? (3)
Dee negotiates with IT departmentThreatens to set up own system of user Ids and
passwords
Says she will set up blog on public server
Would cause confusion that would add to IT department’s work
Her proposal is the lesser of two evils