Copyright © 2006 Heathkit Company, Inc. All Rights Reserved Introduction to Networking Technologies Digital Subscriber Line (DSL)

2 Digital Subscriber Line (DSL) - A technique used for transmitting high-bandwidth data over twisted-pair telephone lines.

3 Central Office Central Office Local Loop Analog Local Loop Analog

4 Voice requires only about 4 kHz of bandwidth. 0 4kHz Frequency Voice

5 Central Office Central Office Local Loop Analog Local Loop Analog Digital

6 For short distances, twisted- pair can handle frequencies much higher than 4kHz.

7 Connecting to the Internet Modem (POTS) ISDN T1 line Digital Subscriber Line (DSL)

8 Cost Vs. Bandwidth Cost $ Bandwidth Modem (POTS) ISDN T1 DSL

9 Advantages of DSL Always-on connectivity High speed Flat-rate service Reliability

10 DSL takes advantage of the bandwidth not required by voice. 0 4kHz Frequency Voice DSL 1MHz

11 xDSL: Asymmetric Digital Subscriber Line (ADSL) Very High Data Rate Digital Subscriber Line (VDSL)

12 Asymmetric DSL – Allows more bandwidth downstream than upstream. 0 4kHz Frequency Voice Downstream 1MHz Upstream

13 Central Office Upstream Downstream To/From ISP To/From ISP

14 Typical ADSL Characteristics Data RateDistance Downstream 1.5 Mbps 15,000 ft Upstream 16 kbps 15,000 ft Downstream 6.1 Mbps9,000 ft Upstream 640 kbps9,000 ft

15 DSL is distance-sensitive You must be within about 12,000 to 18,000 feet of a central office. The distance is the path the wire takes, not the straight-line distance. Even so, the majority of the United States’ population lives and works within DSL range.

16 The DSL Provider The company that delivers DSL service to your home or business. Generally a phone company. Many DSL providers act as their own Internet Service Provider (ISP). Some areas have more than one DSL provider.

17 Customer Premises Equipment (CPE) Telco lingo for phone or DSL equipment in the home or office. Splitter/Filter DSL Modem or DSL Router

18 0 4kHz Frequency Voice Data 1MHz Splitter/Filter Voice/Data Low Pass High Pass Voice Data

19 The DSL Modem Low cost. Requires no customer configuration. Acts as a bridge to your DSL provider’s TCP/IP network.

20 CO Internet ISP PSTN Analog Modem Phone Computer

21 DSL Modem Phone Computer PSTN Internet PSTN Switch PSTN Switch DSLAM Central Office (CO) Splitter/ Filter

22 Problems with the DSL Modem Approach Single IP address The Internet Connection is not easily shared. Security concerns.

23 The DSL Router Turns your local network into a separate TCP/IP LAN. May provide several services such as: DHCP NAT Firewall VPN

24 HUB Analog Modem Small Office/Home Office (SOHO) Phone CO Internet ISP PSTN

25 HUB DSL Router Small Office/Home Office (SOHO) Splitter/ Filter Phone To/From DSL Provider

26 HUB DSL Router Home/Office PSTN Internet PSTN Switch PSTN Switch DSLAM Central Office (CO) Phone Filter

27 Digital Subscriber Line Access Multiplexer (DSLAM) Normally located at the Telco Central Office Concentrates data from numerous DSL connections into a high capacity backbone. Separates voice from data and sends each to its appropriate location.

28 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider

29 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider

30 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider DHCP

31 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider NAT Outgoing Datagram Source IP address

32 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider NAT Outgoing DatagramSource IP address

33 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider NAT Incoming Datagram Destination IP address

34 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider NAT Incoming Datagram Destination IP address

35 HUB DSL Router Small Office/Home Office (SOHO) To/From DSL Provider

36 Very High Data Rate Digital Subscriber Line (VDSL) An emerging technology Promises to deliver Downstream speeds of 15 to 52 Mbps. Upstream speeds of 1.5 to 2.3 Mbps. Over short distances (1000 to 4500 ft) of existing twisted pair phone lines.

37 Central Office Fiber Optic Cable Optical Network Unit (ONU) Optical Network Unit (ONU) Office Building

38 Now, it’s your turn.