http://ils.unc.edu/inls181/notes/...

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Monday April 24

  • Connecting to the Internet: Web hosting and ISPs
  • ISP=Internet Service Provider: They sell consumer-level or small business access to the Internet. Usually temporary/on-demand, but can be 24-hour.
  • Classes of ISP service:
    • Analog dial-in. Regular modem, up to 56Kbps (actually a little less). Uses a regular phone line, hopefully to a local (vs. long distance) untimed phone number.
      • Relatively slow. Modem can only transmit data in one direction at a time; end-users might find their data taking circuitous routes to go places (use traceroute to see where you data are going).
      • Relatively cheap. Monthly plans ranging from $5 to $25 depending on whether hours are limited and what other services are included (e.g., a mailbox or Web page).
      • Local numbers in rural areas may be absent or limited.
      • Dial-up ISP listings are at thelist.com among other places
    • Digital dial-in. ISDN (Integrated Services Digital Network) allows multiple "channels" on a single phone line. You can use a digital modem and a channel for Web traffic, and another channel for a regular phone or fax.
      • Faster than an analog modem (from 64-256Kbps, full duplex)
      • Usually billed as a business service, so every minute costs money.
      • Limited service areas, but usually larger than xDSL (below).
      • Currently not favored; xDSL is favored. Partially because ISDN requires upgrades to telephone company switches and other equipment, more so than xDSL.
    • xDSL is digital "full time." xDSL (ADSL and related technologies; ADSL=Asymmetric Digital Subscriber Line). ADSL offers up to 1Mbps outbound and 8Mbps inbound using a digital modem. Pricing is usually more than a regular dial-in service, but might not require an extra phone line. Service is from the phone company, rather than an ISP.
    • Cable modem is digital "full time," but bandwidth is shared with others on your local cable loop. Upload via modem cable is 1Mbps or more; download may be up to 30Mbps. Some areas offer a "hybrid" solution where the cable is used for download and a regular analog modem is used for upload.
    • DirecPC is a hybrid solution using geosynchronous satellites for download (the same satallites as the small DirecTV dish) and a modem for upload. Requires $400-800 in equipment, and costs somewhat more than a regular modem ISP.

    • All of the above are consumer-oriented: for people who will be USING the Internet, but not PUBLISHING from their Internet access point. For organizations that want to have Web servers and other online content, they need a full time dedicated connection to the Internet.
    • Dedicated data lines: The phone company provides a dedicated data line (usual coaxial or fiber optic) and bandwidth to their local office. This is called the "local loop," and costs from several hundred to many thousand dollars per month, depending on bandwidth and your distance from the phone company central office.

      Then, the phone company or another company provides your connection to the Internet, often with related services (such as DNS servers, news servers, help desk, etc.). These companies are generally not the same as the local ISPs and include: Sprint, Cable and Wireless (bought part of MCI), MCI/WorldCom,

      Speeds and technologies range from 56Kbps - 2Mbps (frame relay, up to a few thousand $'s per month) to 45-155Mbps (ATM, used by UNC, tens of hundreds of thousand $'s per year), to ISP or Internet backbone levels (OC12 [622Mbps] - OC192 [10Gbps]), accessible to phone companies or major resellers.

      For a graphic of MCI/UUNet's global network map, see their site

    • Web hosting. For many businesses (including some very large ones, such as Yahoo!), it makes more sense to locate their Web pages off-site. This effectively outsources Internet connectivity, systems administration and maintenance, while keeping internal control of content.

      Depending on the size of the company and purposes, needs might include secure credit card transactions, shopping carts, ability to re-sell virtual hosts, or other services.

      Costs range from free/no frills (e.g., geocities) to hundreds of $'s per month (for a dedicated server or colocation service).

      See Yahoo!'s category for Web hosting directories for listings and comparison charts for Web hosting services.

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UNC SILS
Prof. Greg Newby