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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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computer network
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

network devices
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

cabling
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

cabling1
Cabling
  • Top: Unshielded Twisted Pair and Shielded Twisted Pair Cable
  • Bottom: Coaxial and Optical Fiber Cable

CS105 Section 2 - Lecture 10

network types
Network Types
  • LAN (Local Area Network)
  • WAN (Wide …)
  • MAN (Metropolitan …)
  • PAN (…)
  • Internet

CS105 Section 2 - Lecture 10

slide7
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

lan topologies
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

ethernet
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

wlan wireless lan
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

wlan wireless lan1
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

wan man
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

gateway
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

internet connections
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

dial up services
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

dial up services1
Dial-up Services
  • ISDN
    • Integrated Services Digital Network
    • 2 data channel (56K each)
    • 1 voice channel

CS105 Section 2 - Lecture 10

broadband services
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

broadband services1
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

broadband services2
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

home network single machine
Home Network (single machine)

Wall Jack

DSL/Cable Modem

USB/Ethernet Cable

CS105 Section 2 - Lecture 10

home network multiple machines
Home Network (multiple machines)

Wall Jack

DSL/Cable Modem

Hub/Switch/Router

USB/Ethernet Cable

CS105 Section 2 - Lecture 10

home network multiple machines1
Home Network (multiple machines)

Wall Jack

Ethernet Cable

DSL/Cable Modem

Hub/Switch/Router

CS105 Section 2 - Lecture 10

home wireless network
Home Wireless Network

Wall Jack

Ethernet Cable

DSL/Cable Modem

Hub/Switch/Router

CS105 Section 2 - Lecture 10

network security
Network Security

Firewall A gateway machine and its software that protects a network by filtering the traffic it allows

CS105 Section 2 - Lecture 10

network addresses
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

network addresses1
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

domain name system
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

domain name system1
Domain Name System

matisse.csc.villanova.edu

Computer

name

Domain name

TLD

CS105 Section 2 - Lecture 10

domain name system2
Domain Name System

Figure 15.10 Top-level domains, including some relatively new ones

CS105 Section 2 - Lecture 10

domain name system3
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

domain name system4
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

references
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

references cont
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