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Going Online

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

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  1. Going Online Chapter 3a

  2. 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

  3. 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

  4. Internet (contd) • 1990 government project ended • Today Internet is commercial • Governed by international group of volunteers • Sets standards • Coordinate global operation

  5. Ingredients to go online • Communications channel • Connection method • Communications protocol • Communications software

  6. 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

  7. 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

  8. Communication channels • Cable • Broadband • Available from cable TV companies • Limited to metropolitan areas • Requires cable modem • 10 Mbps

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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)

  17. Communications software • To be continued…

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