1. DSLs Digital Subscriber Lines

2. Digital Subscriber Lines (DSLs) • Offered by Telephone Companies • Lines to customer premises are subscriber lines, which connect subscribers to the telephone system • These are digital • Hence “digital subscriber line” Telephone Network DSL DSL Modem ISP

3. Digital Subscriber Lines (DSLs) • Offered by Telephone Companies • Several types of digital lines for subscribers • Some are for homes, others for businesses • For residential customers, usually multiplexes regular phone, high-speed data • Can use existing phone line coming into house • Can use Internet without tying up phone Telephone Network DSL Modem ISP Existing Phone Line

4. Digital Subscriber Lines • Most common for home is Asymmetric DSL (ADSL) • Upstream and downstream speeds are different • Upstream at 64 kbps or more • Downstream at 256 kbps to a few Mbps • Asymmetric speed is good for WWW • About $50 per month incl. ISP; more for faster service Telephone Network ADSL DSL Modem ISP 64 or more kbps 256 kbps-a few Mbps

5. Digital Subscriber Lines • G.Lite (G.992.2) Standard • New ADSL standard from ITU-T • Up to 1.5 Mbps downstream speed • No carrier installation is necessary • Not being widely adopted by ADSL vendors yet Telephone Network ADSL DSL Modem ISP 64 or more kbps Up to 1.5 Mbps

6. Digital Subscriber Lines • Digital Subscriber Line Access Multiplexer • Telco must install a DSLAM at end switching office DSL Telephone Network ISP DSLAM DSL DSL

7. Digital Subscriber Lines New • Splitting Voice and Data • Voice and data are split at home by the DSL modem • Voice and data are also split at the telephone company’s first switching office Computer DSLAM DSL Modem DSL Splitter Phone DSL Voice Network

8. DSLs Versus Cable Modem Service • Both Expected to Sell Well • Forecast for Worldwide Installations in 2004 • Cable modem lines: 9 million • DSLs: 10 million • Source: Insight Research • Cable is Available Mostly in Residential Areas • Cable is only widespread in some countries, especially the United States