CS105 Introduction to - PowerPoint Presentation

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

Computer Network4/24/2012 CS105 Section 1 - 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

Network DevicesTo connect multiple segments of networks into a larger oneHub: 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 4/24/2012 CS105 Section 1 - Lecture 10 3

CablingCoaxial 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 networksUnshielded 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. 4/24/2012CS105 Section 1 - Lecture 104

Cabling Top: Unshielded Twisted Pair and Shielded Twisted Pair Cable Bottom: Coaxial and Optical Fiber Cable 4/24/2012 CS105 Section 1 - Lecture 10 5

Network Types4/24/2012 CS105 Section 1 - Lecture 10 LAN (Local Area Network) WAN (Wide …) MAN (Metropolitan …) PAN (…)Internet 6

LAN4/24/2012 CS105 Section 1 - Lecture 10 A network that connects a relatively small number of machines in a relatively close geographical area E.g., office buildings 7

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 4/24/2012 CS105 Section 1 - Lecture 10 8

Ethernet The industry standard bus (star) technology for LAN 10BaseT 10Mbps (Mega bits per second) 100BaseT 100Mbps1000BaseT 1000Mbps or 1Gbps 4/24/2012 CS105 Section 1 - Lecture 10 9

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 . mobilenetHotspot The area covered by wireless access points 4/24/2012 CS105 Section 1 - Lecture 10 10

WLAN (Wireless LAN)Standard802.11b - 11Mbps802.11g - 54Mbps802.11a - 54MbpsSecurity WEP (Wired Equivalent Privacy) WPA (Wi-Fi Protected Access) To prevent wardriving 2.4G 5G 4/24/2012 CS105 Section 1 - Lecture 10 11

WAN/MANWide-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 citiesInternet A wide area network that spans the planet 4/24/2012CS105 Section 1 - Lecture 10 12

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 4/24/2012 CS105 Section 1 - Lecture 10 13

Internet ConnectionsInternet 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 4/24/2012 CS105 Section 1 - Lecture 10 14

Dial-up ServicesModemModulator/demodulatorA 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 4/24/2012 CS105 Section 1 - Lecture 10 15

Dial-up ServicesISDNIntegrated Services Digital Network2 data channel (56K each)1 voice channel 4/24/2012 CS105 Section 1 - Lecture 10 16

Broadband ServicesxDSL (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 modemSplitters are needed to separate the voice and data signal 4/24/2012CS105 Section 1 - Lecture 1017

Broadband ServicesCableA technology that provides digital data transmission over cable TV infrastructureSpeedDownlink 128Kbps - 3~5Mbps Uplink 64Kbps - 128Kbps~1Mbps Need a cable modem 4/24/2012 CS105 Section 1 - Lecture 10 18

Broadband ServicesSatelliteA technology that provide digital data transmission over satellitesSpeedDownlink 500Kbps - 1Mbps Uplink 50Kbps - 100Kbps Need a satellite dish 4/24/2012 CS105 Section 1 - Lecture 10 19

Home Network (single machine) USB/Ethernet Cable DSL/Cable Modem Wall Jack 4/24/2012 CS105 Section 1 - Lecture 10 20

Home Network (multiple machines) USB/Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch/Router 4/24/2012 CS105 Section 1 - Lecture 10 21

Home Network (multiple machines) Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch/Router 4/24/2012 CS105 Section 1 - Lecture 10 22

Home Wireless Network Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch/Router 4/24/2012 CS105 Section 1 - Lecture 10 23

Network Security Firewall A gateway machine and its software that protects a network by filtering the traffic it allows 4/24/2012 CS105 Section 1 - Lecture 10 24

Network AddressesHostname 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 4/24/2012 CS105 Section 1 - Lecture 10 25

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? 4/24/2012 CS105 Section 1 - Lecture 10 26

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 4/24/2012 CS105 Section 1 - Lecture 10 27

Domain Name Systemmatisse.csc.villanova.edu Computer name Domain name TLD 4/24/2012 CS105 Section 1 - Lecture 10 28

Domain Name System Figure 15.10 Top-level domains, including some relatively new ones 4/24/2012 CS105 Section 1 - Lecture 10 29

Domain Name SystemOrganizations based in countries other than the United States use a top-level domain that corresponds to their two-letter country codes Figure 15.11 Some of the top-level domain names based on country codes Do you email someone in another country? 4/24/2012 CS105 Section 1 - Lecture 10 30

Domain Name SystemDomain 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 4/24/2012 CS105 Section 1 - Lecture 10 31

ReferencesComputer Science Illuminated Ch 15 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.pptBasic Computer Network by Weesan Leehttp://www.cs.ucr.edu/~weesan/cs6/03_basic_computer_network.ppt 4/24/2012CS105 Section 1 - Lecture 1032

References (cont)Domain Nameshttp://www.icann.org/topics/new-gtld-strategy-faq.htmhttp://www.iana.org/root-whois/index.html 4/24/2012 CS105 Section 1 - Lecture 10 33