සීමාවන් නොමැති අදහස් වලට පණ දෙන්න.....

Friday, September 11, 2009

Internet connectivity mechanisms

Internet connectivity mechanisms

Now anybody can access the Internet and get it's benefit. There are several ways to connect to the Internet.




Cable connections

Wireless connections

T-1, T-2 and T-3 lines



  • Dialup is simply the application of the Public Switched Telephone Network (PSTN) to carry data on behalf of the end user. It involves a customer premises equipment (CPE) device sending the telephone switch a phone number to direct a connection to.

  • Speed ranges from 2400 bps to 56 Kbps

  • Twisted pair (regular phone lines) is the physical medium.

  • Cheap but slow compared with other technologies.

  • Speed may degrade due to the amount of line noise


  • Integrated Services Digital Network is a telephone system network. ISDN is integrates speech and data on the same lines, adding features that were not available in the classic telephone system. access interfaces

    • Basic Rate Interface (BRI)

    • Primary Rate Interface (PRI)

    • Broadband-ISDN (B-ISDN)

  • Dedicated telephone line and router required.

  • Speed ranges from 64 Kbps to 128 Kbps.

  • Physical medium is Twisted pair.

  • Not available everywhere but becoming more widespread.

  • An ISDN line costs slightly more than a regular telephone line, but you get 2 phone lines from it.

  • 56K ISDN is much faster than a 56K dialup line

Digital subscriber line ( DSL )

  • Digital subscriber line ( DSL ) is more expensive than dialup, but provides a faster connection. DSL also uses telephone lines, but unlike dialup access, DSL provides a continuous connection to the Internet.

  • This connection option uses a special high-speed modem that separates the DSL signal from the telephone signal and provides an Ethernet connection to a host computer or LAN.

  • Doesn’t interfere with normal telephone use.

  • Bandwidth is dedicated, not shared as with cable.

  • Bandwidth is affected by the distance from the network hubs. Must be within 5 km (3.1 miles) of telephone company switch.

  • Limited availability.

  • Not networkable

Cable Internet

  • A cable Internet is a connection option offered by cable television service providers. The Internet signal is carried on the same coaxial cable that delivers cable television to homes and businesses.

  • A special cable modem separates the Internet signal from the other signals carried on the cable and provides an Ethernet connection to a host computer or LAN.

  • CMTS is the equipments provides the Cable Internet service to the users. It provides the same service which DSLAM offers.

  • 512 Kbps to 20 Mbps

  • Coaxial cable and in some cases telephone lines used for upstream requests as physical medium


  • Access is gained by connection to a high speed cellular like local multi-point communications system (LMCS) network via wireless transmitter/receiver.

  • Speed is 30 Mbps or more

  • Physical medium is Airwaves (antenna)

  • Can be used for high speed data, broadcast TV and wireless telephone service.


  • Satellite connection is an option offered by satellite service providers.

  • The user's computer connects through Ethernet to a satellite modem that transmits radio signals to the nearest Point of Presence, or POP, within the satellite network.

  • Newer versions have two-way satellite access, removing need for phone line.

  • In older versions, the computer sends request for information to an ISP via normal phone dial-up communications and data is returned via high speed satellite to rooftop dish, which relays it to the computer via a decoder box.

  • Speed is 30 Mbps or more

  • Physical medium is Airwaves (antenna)

  • Bandwidth is not shared.

  • Satellite companies are set to join the fray soon which could lead to integrated TV and Internet service using the same equipment and WebTV like integrated services

  • Latency is typically high

  • Some connections require an existing Internet service account.

Frame Relay

  • Provides a type of "party line" connection to the Internet.

  • Requires a FRAD (Frame Relay Access Device) similar to a modem, or a DSU/CSU.

  • speed ranges from 56 Kbps to 1.544 Mbps (or more, depending on connection type)

  • Various physical mediums used

  • May cost less than ISDN in some locations.

  • Limited availability.

  • Uses one of the connection types below, fractional up to OC3

Fractional T1 (Flexible DS1)

  • Only a portion of the 23 channels available in a T1 line is actually used.

  • Speed ranges from 64 Kbps to 1.544 Mbps

  • Physical medium is Twisted-pair or coaxial cable

  • Cheaper than a full T1 line with growth options of 56 Kbps or 64 Kbps increments as required.


  • Special lines and equipment (DSU/CSU and router) required.

  • Speed 1.544 Mbps

  • Physical medium is Twisted-pair, coaxial cable, or optical fiber

  • Typically used for high bandwidth demands such as videoconferencing and heavy graphic file transfers.

  • Minimum for large businesses and ISPs.

  • Expensive


  • Typically used for ISP to Internet infrastructure.

  • Speed 44.736 Mbps

  • Physical medium is Optical fiber


  • Typically used for ISP to Internet infrastructure within Internet infrastructure.

  • Speed 51.84 Mbps

  • Physical medium is Optical fiber


  • Typically used for large company backbone or Internet backbone.

  • Speed 155.52 Mbps

  • Physical medium is Optical fiber

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හිත නිතරම වෙනස් වෙනවා. හිතට නිතරම සිතුවිලි එනවා.
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ඇනෝලා සමා වෙත්වා. මගේ බ්ලොග් එකට ස්පෑම්බොට් එකකින් ස්පෑම් කමෙන්ට් එනනිසා ඇනෝලාගේ කමෙන්ට් කිරීමේ අයිතිය නැති කරන්න සිදු වුනා.

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