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CS105 INTRODUCTION TO COMPUTER CONCEPTS COMPUTER NETWORKS 101 Instructor: Cuong (Charlie) Pham.

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Presentation on theme: "CS105 INTRODUCTION TO COMPUTER CONCEPTS COMPUTER NETWORKS 101 Instructor: Cuong (Charlie) Pham."— Presentation transcript:

1 CS105 INTRODUCTION TO COMPUTER CONCEPTS COMPUTER NETWORKS 101 Instructor: Cuong (Charlie) Pham

2 Computer Network CS105 Section 2 - Lecture 10 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 2

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 3

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. Thicknet is 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 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 4

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

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

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

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 8

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 9

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 10

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

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 12

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

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 14

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 15

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

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 17

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 18

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 19

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

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

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

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

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 24

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 25

26 Network Addresses 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 Figure 15.9 An IP address is stored in four bytes Where does the host number come from? CS105 Section 2 - Lecture 10 26

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 27

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

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

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 Figure Some of the top-level domain names based on country codes Do you someone in another country? CS105 Section 2 - Lecture 10 30

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 31

32 References Computer Science Illuminated Ch 15 Slides Modem DSL Cabling nToNetworking.ppt Basic Computer Network by Weesan Lee _network.ppt CS105 Section 2 - Lecture 10 32

33 References (cont) Domain Names faq.htm faq.htm CS105 Section 2 - Lecture 10 33


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