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DSL Digital Subscriber Line

DSL Digital Subscriber Line. An Ngo. Agenda. The Need for Speed What is DSL? PROs & CONs DSL Compared Coverage & Providers. The Need for Speed. Explosive Growth of the Internet Increase Demand for High-Speed Access By Businesses & Individuals Increase Demand for New Applications

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DSL Digital Subscriber Line

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  1. DSLDigital Subscriber Line An Ngo

  2. Agenda • The Need for Speed • What is DSL? • PROs & CONs • DSL Compared • Coverage & Providers

  3. The Need for Speed • Explosive Growth of the Internet • Increase Demand for High-Speed Access • By Businesses & Individuals • Increase Demand for New Applications • Real-time interactive multimedia • Video conferencing • Distance learning

  4. What is DSL? • Digital Subscriber Line • A technology which uses the existing transmission medium (telephone wire) to provide high-speed transfer of information across the internet. • The Technology • DSL simply uses more of the bandwidth. • It utilizes the frequencies above the voice spectrum. • Greater than 4KHz • No interference to normal phone conversations (below 4KHz). • Thus, it can encode more data to achieve higher data rates than would otherwise be possible in the restricted frequency range of the old telephone network.

  5. Common Types of DSL • ADSL - Asymmetric transfer rates • ~6Mbps downstream / ~640Kbps upstream • SDSL - Symmetric • ~1Mbps up & down • HDSL - High Bit Rate Symmetric • ~2Mbps up & down • VDSL - Very High Bit Rate • Restricted to users less than a mile from Telco. (~50Mbps) • RADSL – Rate Adaptive • Automatically adjusts speed to the line condition. • Uplink rate depends on the downlink rate.

  6. How It Works • A.Over the Wire: You are connected to another ADSL modem which also has a POTS splitter, which separates voice calls from data. • B.Telephone Calls: Voice calls are routed to the phone company's public switched telephone network (PSTN) and proceed on their way as usual. • C.Internet Requests: DSL Access Multiplexer links many ADSL lines to a single high-speed asynchronous transfer mode (ATM) line, which in turn connects to the Internet. • D.Back at You: The requested data is retrieved from the Internet and routed back to you. http://www.zdnet.com/pccomp/features/excl0198/dsl/adsl2a.html

  7. PROs Speed Up to 8 Mbps Downstream Cost Affordable (~$50/mo.) Connectivity Instant “always-on” Investment Uses existing copper infrastructure Application Enhancements Enables high quality real-time, interactive multimedia CONs Distance Signal degradation with increasing distances Load coils Causes distortion at higher DSL frequencies Interference Cross-talk interference between adjacent pair of wires Network Compatibility DSL equipment must be compatible with Telco. PROs & CONs

  8. DSL Compared • ISDN • Pros: Widely available, permits fax, data, and voice on the same line. • Cons: Top speed of only 128Kbps, not available in all areas, often difficult to set up, expensive phone-company and ISP charges. • Satellite (DBS) • Pros: Available to anyone with an unobstructed view of the southern sky. • Cons: Top download speed of only 400Kbps is just a fraction of cable or DSL; requires an analog modem for uploads • Cable • Pros: Available wherever cable TV is; provides high-speed downloads and uploads; inexpensive. • Cons: Actual speeds reach only around 1.5Mbps downstream and 300Kbps upstream; you share bandwidth with others in your area; difficult to get in many older, urban buildings.

  9. Current Coverage Area • U.S. • Canada • Hong Kong • Singapore • Trial Basis: Most other industrialized countries. http://www.zdnet.com/pccomp/features/excl0198/dsl/adsl4.html

  10. Ameritech Bell Atlantic Dakota Services Limited Intelecom Data Systems InterAccess Lotus/Bell Atlantic MCI Northland Communication Pacific Bell Southwestern Bell DSL Providers

  11. Questions

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