Technology 7
Peer-to-Peer Networks
Client-Server Networks
Nodes
Transmission Media
 Existing Wiring
 Twisted Pair
 Coaxial Cable
 Fiber-Optic Cable
 Wireless Connections
Data Transfer Rate (Bandwidth) -- Maximum Speed of Data Transfer
Throughput – Actual Speed of Data Transfer
Data Transfer Rate – Megabits per Second – Mbps (one million bits per second)
Network Adapters – devices that enable nodes to communicate
 External Network Adapters
 Network Interface Cards (NIC)
Packets
Network Navigation Devices
 Router – transfer packets of information between networks
 Switches – sends packets to selected nodes on the same network
Peer-to-Peer Networks
 Wired Ethernet Networks
 Wireless Ethernet Networks
 Power-Line Networks
Wired Ethernet Networks – IEEE 802.3 Standard
 Efficient Transfer of Data
 Complex Data Transfer Algorithms
 Fast, Reliable
 NIC Cards -- 1,000 Mbps Equipment
 Unshielded Twisted Pair (UTP) Cables - page 319 for details wrt specific UTP features
 Network Navigation Devices
 Repeaters – devices that amplify data signals
o required for cable runs over 328 feet
o maximum run limited to 600 feet
 Ethernet Switches
o sends packets to selected nodes on the same network
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o sends a specific packet only to the node to which it should be sent
o keeps track of the data packets
o in conjunction with the NIC cards,
guides the data packets to their final destination
o keeps the network running efficiently
Hubs – retransmits data signals, ie., data packets to all nodes attached to it
Wireless Ethernet Networks – IEEE 802.11 (WiFi) Standard
See www.ieee.org for details wrt IEEE 802.11b, IEEE 802.11g standards
 Wireless Network Adapter Cards
o Transceiver
 converts electronic signals to &/or from radio signals
 transmit and receive radio signals
 Wireless Router
o Transceiver
 converts electronic signals to &/or from radio signals
 transmit and receive radio signals
 Range & Quality of Transmission
o Maximum Range 250 feet
o 802.11b & 802.11g devices transmit on a bandwidth of 2.4 GHz
o cell phones transmit on a bandwidth of 2.4 GHz
 Wireless Access Point Device – extends the range of a wireless network
o connect directly to the router
o connect to a node that is within range of the router
Power-Line Networks
HomePlug Power Line Alliance – www.homeplug.org
 Data Transfer Rate -- 200 Mbps
 Attach a Power-Line Network Adapter to each Node (computer)
 Plug the Power-Line Network Adapter into an electrical outlet
Historical Cost Analysis (page 327)
Cybercrime
 Hackers – anyone who unlawfully breaks into a computer system
 White-Hat Hackers (testing a systems vulnerabilities)
 Black-Hat Hackers (malicious intent)
o Financial Benefit
o Industrial Espionage
o International Governmental Espionage
 W32/Conficker.worm.gen.d
 Script Kiddies – use tools created by hackers to break into systems
 Packet Sniffer program that searches all packets traveling through a
specific node, looking for vital financial &/or other useful information, e.g.,
credit card numbers, bank account numbers & passwords, e-commerce
login names & passwords, social security numbers, birthdates, etc.
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Copier Machines – hard drives – tax returns
Identity Theft (see page 336)
Trojan Horses
o Appears to do something useful or desirable
o Does something malicious in the background
o Installation of Backdoor Programs
o Zombie Computers
Denial of Service Attacks (DoS)
Distributed Denial of Service Attacks (DDoS)
o Hackers use numerous zombie computers to repeatedly request bogus
service from a service provider; the requests overwhelm the service
providers computer systems to the point where they shut down
Unrelated Topic
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Logical Ports
 Virtual, i.e., software, communication paths that allow a computer to
organize requests for information from other networks or computers
 Each port is numbered and assigned to a specific service
o HTTP – port 80
o Simple Mail Transfer Protocol (SMTP) – port 25
Firewalls
 Software Firewalls
o Norton Personal Firewall
o McAfee Firewall
o ZoneAlarm
o BlackICE PC Protection
 Hardware Firewalls – Network Address Translation (page 338-339)
o Linksys Routers
Routers without NAT cannot provided
Firewall Protection
o D-Link Routers
o Netgear Routers
 Security Test – www.grc.com
 Wireless Networks
o Firewall
o Change the Service Set Identifier, i.e., router name
o Disable the SSID Broadcast feature – keeps the router from
broadcasting the SSID
o Change the router password
o Security Protocols – Encryption Key Required for access
 Wired Equivalent Privacy (WEP) -- weaker encryption code
 Wi-Fi Protected Access (WPA) -- stronger encryption code
o Implement the Media Access Control feature
 each Network Adapter has a unique number assigned to it by the
manufacturer, the Media Access Control Number (MAC Address)
 restrict network access to designated MAC Address devices
o Apply Firmware Upgrades – router has a read-only memory chip with
software, i.e., firmware, written on it; manufacturers issue updates, i.e.,
“patches”; periodically check the manufacturer’s website and apply the
necessary upgrades
Viruses -- program fragments that
 attach to other programs
 attempt to hide within the host program
 replicate itself
 attach it’s replicates to other programs
 side affects
o malicious intent
o innocuous intent
 types of viruses
o Boot-Sector Viruses
 Master Boot Record is a program that executes whenever the
computer is started; this ensures that the virus is loaded into
memory before the virus protection programs become active
 Potentially very destructive, e.g., format t hard drive
o Logic Bombs -- triggered when certain conditions are met
o Time Bombs – triggered by the passage of time or on a certain date
o Script Viruses – series of commands embedded in websites
 automatically run when you visit the website
 Amazon.com scripts allow you to purchase items from the site
 E-mail website links – potential source of script viruses
o Macro Viruses –
 Macros are series of commands which may be attached to any MS
Office Product, e.g., MS Word
 Opening the infected document triggers the virus which then infects
other documents of the same type
o Encryption Viruses
 Virus searches for common data files, e.g., MS Word documents
 Encrypts the files with a complex encryption method
 Requests, via e-mail, payment of a fee for the encryption code and key
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Worms – programs that travel between systems via network connections
o can run independently of a host program execution
o very active in spreading themselves
o exploits weaknesses in the Windows Operating System
o antivirus software is ineffective against worms
o firewalls with up to date patches applied are effective
Technology 8
EDGE – Enhanced Data Rate for Global Evolution & EVDO – Evolution Data Optimized
 data transfer rate ≥ 700 Kb/sec
hence improved multimedia access
 wide area coverage
 less interference – fewer dropped calls
Music File Formats
 MP3
 ACC
 WMA
Napster – P2P Sharing -- centralized index server
 Pre June 2002 – free downloads
 Post June 2002 – sells access to music files
Gnutella & Kazaa – P2P Sharing – facilitates connections between interested parties
Podcasting
PDA
 faster processors than cell phones
 more powerful than cell phones
 slightly larger than cell phones
 decreased battery life compared to cell phones
 synchronization of data files with computer system -- cradle
 synchronization of data files with other PDA’s
o IrDA wireless -- infrared waves
o Bluetooth wireless -- radio waves
 WAP – Wireless Application Protocol
Smartphones
 Palm Treo 700wz – PDA with the following capabilities added
o Cellphone
o EVDO
o Bluetooth
o PMP features – multimedia
 T-Mobile SDA – Cellphone with the following capabilities added
o Email access
o Internet access
New Gadgets
www.gizmodo.com
Tablet PC
 Portable computer
 Electronic clipboard – advanced handwriting recognition
 Digital Ink
o Pressure sensitive screen
o Hand drawn images
 stored as hand drawn picture images
 converted to & stored as rectified graphic images
 Software keyboard displayed on the screen
 Bluetooth or WiFi connectivity
 Docking Station
GPS – Global Positioning System -- 21 satellites
Notebooks
 Hot-swappable bays
 Battery Life Extension
o turn off computer when not in use
o install maximize amount of RAM
o turn off wireless capabilities when not in use
o charge batteries to maximum amount – don’t partially charge system
o minimize the use of DVD drives
 security lock
 portable surge protector
 collaboration software
o www.colligo.com
o Windows Meeting Space