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CS105 Introduction to Computer Concepts Computer networks 101

CS105 Introduction to Computer Concepts Computer networks 101. Instructor: Cuong (Charlie) Pham. Computer Network. A collection of computing devices connected in order to communicate and share resources

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CS105 Introduction to Computer Concepts Computer networks 101

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  1. CS105 Introduction to Computer ConceptsComputer networks 101 Instructor: Cuong (Charlie) Pham

  2. Computer Network • A collection of computing devices connected in order to communicate and share resources • Connections between computing devices can be physical using wires or cables or wireless using radio waves or infrared signals CS105 Section 2 - Lecture 10

  3. Network Devices • To connect multiple segments of networks into a larger one • Hub: A multiport repeater to enhance signal within the same network • Switch: Like hub but with intelligent  Better performance • Router: Forward packets from one network to another CS105 Section 2 - Lecture 10

  4. Cabling • Coaxial Cable • Thinnet looks like regular TV cable. It is about 1/4 inch in diameter and is very flexible and easy to work with. • Thicknetis about 1/2 inch in diameter and not very flexible. Thicknet is older and not very common anymore except as a backbone within and between buildings. Coax transmits at 10 Mbps..  • Twisted Pair. Twisted pair looks like telephone wire and consists of insulated strands of copper wire twisted together. There are two versions of twisted pair cable: • Shielded Twisted Pair (STP). STP is commonly used in Token Ring networks • Unshielded Twisted Pair (UTP). UTP is used in Ethernet networks. Transmission rates vary between 10-100-1000-10000 Mbps. • Fiber-Optic Cable. Fiber-optic cable consists of a thin cylinder of glass surrounded by glass cladding, encased in protective outer sheath.   Fiber-optic cable is very fast (over 1Gbps).  It can transmit over long distances (2 km +) but is expensive. CS105 Section 2 - Lecture 10

  5. Cabling • Top: Unshielded Twisted Pair and Shielded Twisted Pair Cable • Bottom: Coaxial and Optical Fiber Cable CS105 Section 2 - Lecture 10

  6. Network Types • LAN (Local Area Network) • WAN (Wide …) • MAN (Metropolitan …) • PAN (…) • Internet CS105 Section 2 - Lecture 10

  7. LAN • A network that connects a relatively small number of machines in a relatively close geographical area • E.g., office buildings CS105 Section 2 - Lecture 10

  8. LAN Topologies • Ring topology connects all nodes in a closed loop on which messages travel in one direction • Star topology centers around one node to which all others are connected and through which all messages are sent • Bus topology nodes are connected to a single communication line that carries messages in both directions CS105 Section 2 - Lecture 10

  9. Ethernet • The industry standard bus (star) technology for LAN • 10BaseT • 10Mbps (Mega bits per second) • 100BaseT • 100Mbps • 1000BaseT • 1000Mbps or 1Gbps CS105 Section 2 - Lecture 10

  10. WLAN (Wireless LAN) • Wi-Fi (Wireless Fidelity) • A wireless technology that connects computers without cables • Access Point (AP) • A device (base station) that connects wireless devices together • Usually connected to a wired-network • SSID (Service Set ID) • A “name” for the AP, eg. mobilenet • Hotspot • The area covered by wireless access points CS105 Section 2 - Lecture 10

  11. WLAN (Wireless LAN) • Standard • 802.11b - 11Mbps • 802.11g - 54Mbps • 802.11a - 54Mbps • Security • WEP (Wired Equivalent Privacy) • WPA (Wi-Fi Protected Access) • To prevent wardriving 2.4G 5G CS105 Section 2 - Lecture 10

  12. WAN/MAN • Wide-area network(WAN) A network that connects local-area networks over a potentially large geographic distance • Metropolitan-area network(MAN)The communication infrastructures that have been developed in and around large cities • Internet A wide area network that spans the planet CS105 Section 2 - Lecture 10

  13. Gateway One particular set up to handle all communication going between that LAN and other networks Figure 15.1 Local-area networks connected across a distance to create a wide-area network CS105 Section 2 - Lecture 10

  14. Internet Connections • Internet backbone A set of high-speed networks that carry Internet traffic, provided by companies such as AT&T, Verizon, GTE, British Telecom, and IBM • Internet service provider(ISP)A company that provides other companies or individuals with access to the Internet CS105 Section 2 - Lecture 10

  15. Dial-up Services • Modem • Modulator/demodulator • A device that converts analog signal to digital (modulation) and vice versa (demodulation) • Speed • 1200/2400/9600 bps • 14.4/28.8/33.6 Kbps • 56 Kbps CS105 Section 2 - Lecture 10

  16. Dial-up Services • ISDN • Integrated Services Digital Network • 2 data channel (56K each) • 1 voice channel CS105 Section 2 - Lecture 10

  17. Broadband Services • xDSL (Digital Subscriber Line) • A technology that provides digital data transmission over unused frequencies on traditional telephone lines • For example, ADSL (Asymmetric DSL) • Speed • Downlink • 128Kbps - 4Mbps • Uplink • 64Kbps - 800Kbps • Need a DSL modem • Splitters are needed to separate the voice and data signal CS105 Section 2 - Lecture 10

  18. Broadband Services • Cable • A technology that provides digital data transmission over cable TV infrastructure • Speed • Downlink • 128Kbps - 3~5Mbps • Uplink • 64Kbps - 128Kbps~1Mbps • Need a cable modem CS105 Section 2 - Lecture 10

  19. Broadband Services • Satellite • A technology that provide digital data transmission over satellites • Speed • Downlink • 500Kbps - 1Mbps • Uplink • 50Kbps - 100Kbps • Need a satellite dish CS105 Section 2 - Lecture 10

  20. Home Network (single machine) Wall Jack DSL/Cable Modem USB/Ethernet Cable CS105 Section 2 - Lecture 10

  21. Home Network (multiple machines) Wall Jack DSL/Cable Modem Hub/Switch/Router USB/Ethernet Cable CS105 Section 2 - Lecture 10

  22. Home Network (multiple machines) Wall Jack Ethernet Cable DSL/Cable Modem Hub/Switch/Router CS105 Section 2 - Lecture 10

  23. Home Wireless Network Wall Jack Ethernet Cable DSL/Cable Modem Hub/Switch/Router CS105 Section 2 - Lecture 10

  24. Network Security Firewall A gateway machine and its software that protects a network by filtering the traffic it allows CS105 Section 2 - Lecture 10

  25. Network Addresses Hostname A name made up of words separated by dots that uniquely identifies a computer on the Internet IP address An address made up of four one-byte numeric values separated by dots that uniquely identifies a computer on the Internet CS105 Section 2 - Lecture 10

  26. Network Addresses Figure 15.9 An IP address is stored in four bytes Class A: first byte for network address and three remaining bytes for host number Class B:first two bytes for network address and the last two bytes for host number Class C: first three bytes for network address and the last byte for host number Where does the host number come from? CS105 Section 2 - Lecture 10

  27. Domain Name System Host number The part of the IP address that specifies a particular host (machine) on the network Yes, but what is it? Domain name The part of a hostname that specifies a specific organization or group Top-level domain (TLD) The last section of a domain name that specifies the type of organization or its country of origin CS105 Section 2 - Lecture 10

  28. Domain Name System matisse.csc.villanova.edu Computer name Domain name TLD CS105 Section 2 - Lecture 10

  29. Domain Name System Figure 15.10 Top-level domains, including some relatively new ones CS105 Section 2 - Lecture 10

  30. Domain Name System Organizations based in countries other than the United States use a top-level domain that corresponds to their two-letter country codes Do you email someone in another country? Figure 15.11Some of the top-level domain names based on country codes CS105 Section 2 - Lecture 10

  31. Domain Name System Domain name system (DNS) A distributed system for managing hostname resolution Domain name server A computer that attempts to translate a hostname into an IP address CS105 Section 2 - Lecture 10

  32. References • Computer Science Illuminated Ch15 Slides • Modem • http://en.wikipedia.org/wiki/Modem • DSL • http://en.wikipedia.org/wiki/Digital_subscriber_line • Cabling • http://ww2.it.nuigalway.ie/.../ct101/CT101_IntroductionToNetworking.ppt • Basic Computer Network by Weesan Lee • http://www.cs.ucr.edu/~weesan/cs6/03_basic_computer_network.ppt CS105 Section 2 - Lecture 10

  33. References (cont) • Domain Names • http://www.icann.org/topics/new-gtld-strategy-faq.htm • http://www.iana.org/root-whois/index.html CS105 Section 2 - Lecture 10

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