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Going Online. Chapter 3a. Connectivity. Computer strength Ability of computers to communicate with each other at computer speeds Ultimate example is Internet Inter connected Net works Collection of independent networks w/ Internet host connected 24/7. Internet.

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Going online

Going Online

Chapter 3a


Connectivity
Connectivity

  • Computer strength

  • Ability of computers to communicate with each other at computer speeds

  • Ultimate example is Internet

    • Interconnected Networks

    • Collection of independent networks w/ Internet host connected 24/7


Internet
Internet

  • Began in 1969 as APRANET project of Dept of Defense

    • Build a communications network for military, scientists, researchers across nation

    • Important stipulation – network should remain functional even if parts were down

    • Resulted in network with no central computer and multiple communication pathways between sites


Internet contd
Internet (contd)

  • 1990 government project ended

  • Today Internet is commercial

  • Governed by international group of volunteers

    • Sets standards

    • Coordinate global operation


Ingredients to go online
Ingredients to go online

  • Communications channel

  • Connection method

  • Communications protocol

  • Communications software


Communication channels
Communication channels

  • Rated by bandwidth

    • Number of bits transmitted per second (bps)

    • Low bandwidth = narrow bandwidth

    • High bandwidth = broadband

    • Broadband is now generic term for

      • High–speed Internet access

      • Always on


Communication channels1
Communication channels

  • Dialup access with POTS

    • Narrowband

    • Temporary connection

    • Required modem to convert

      • Computer digital signals

      • Phone line analog signals

    • ISP provides access to a host Internet server

    • 56 Kbps


Communication channels2
Communication channels

  • Cable

    • Broadband

    • Available from cable TV companies

    • Limited to metropolitan areas

    • Requires cable modem

    • 10 Mbps


Communication channels3
Communication channels

  • DSL or digital subscriber line

    • New broadband technology using POTS

    • Required DSL modem

    • Limited to metropolitan areas

    • Two speeds

      • Downstream rate (to client) 9 Mbps

      • Upstream rate (to server) 1.5 Mbps


Communications channels
Communications channels

  • Satellite

    • Broadband

    • Must have southern exposure

    • Problems

      • Latency = lag in response time of ¼ second

      • Weather dependence

    • Requires satellite dish and satellite modem

    • 1.5 Mbps


Communication channels4
Communication channels

  • Wireless

    • Requires access point or a link to a wired network

    • Uses short-range radio waves

    • Wi-Fi is the umbrella for several wireless standards (IEEE 802.11)

      • Wireless-B (IEEE 802.11b) 11 Mbps, up to 300 ft

      • Wireless-A (IEEE 802.11a) 54 Mbps, up to 50 ft

      • Wireless-G (IEEE 802.11g) 54 Mbps, up to 300 ft


Connection methods
Connection methods

  • ISP = Internet service provider

    • Commercial service via dialup, cable, DSL, satellite

    • Each channel requires a modem

  • Network = Local Area network (LAN)

    • Network has a host Internet server

    • Broadband access shared by all users in network

    • Requires network interface card (NIC) on each PC


Communication protocols
Communication protocols

  • Communication relies on protocols

    • Set of rules computers use to communicate with each other

    • Establish, maintain, terminate connection

    • Many different protocols

    • A single computer can support multiple protocols

    • To communicate both computers must use the same protocol


Communication protocols1
Communication protocols

  • Protocol of the Internet is TCP/IP

  • Uses an IP address to uniquely identify each user on the Internet

    • Four number (0-255), separated by periods

      • i.e. 206.28.104.10

    • IP address is assigned by ISP or network


Tcp ip
TCP/IP

  • Numbers are difficult to remember so TCP/IP includes DNS service

    • Translates domain names to IP address

    • Users use domain names to access Internet

      • i.e. www.victoriacollege.edu

    • Names must be registered

    • Charge is assessed to support Internet operations


Going online
DNS

  • Domain names are read from right to left

  • To determine IP address of www.victoriacollege.edu.

    • First, goes to root DNS server (.) for addresses of next level DNS server (edu)

    • Next, goes to edu server and retrieves address for next level DNS server (victoriacollege)

    • Finally, goes to victoriacollege DNS server to retrieves address for www (host PC)


Communications software
Communications software

  • To be continued…