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Chapter 11 Voice and Data Delivery Networks Ken D. Vilar Csc 113
26

Voice and Data Delivery Networks

Dec 07, 2014

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Internet

Ken Vilar

Introduction to Computer Networks and Data Communications, Voice and Data Delivery Networks
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Page 1: Voice and Data Delivery Networks

Chapter 11Voice and Data Delivery

Networks

Ken D. Vilar

Csc 113

Page 2: Voice and Data Delivery Networks

Outline:

• The 56k Dial-Up Modem• Digital Subsciber Line• DSL basics• DSL formats• Cable Modems

Page 3: Voice and Data Delivery Networks

The 56k Dial-Up Modem

• 33,600-bps modem was made available in 1995 using standard telephone lines a modem would

ever achieve many experts believe this was the fastest modem and this was based on two facts.

1. Telephone connection into a home is an analog-modulated connection (using phase shift keying).

2. Telephone signal is transmitted with a certain signal power level and a given amount of background noise.

Page 4: Voice and Data Delivery Networks

The 56k Dial-Up Modem

Did something in the telephone system change to allow the faster transmission speed, or were the industry experts wrong?

Page 5: Voice and Data Delivery Networks

The 56k Dial-Up Modem

Did something in the telephone system change to allow the faster transmission speed, or were the industry experts wrong?

Digital Signaling was introduced.

Page 6: Voice and Data Delivery Networks

The 56k Dial-Up Modem

• 56,000-bps or 56k modem hybrid design, combining analog signaling and

digital signaling employs digital signaling instead of using analog

signaling Telephone system can send an 8-bit sample 8000

times per second, which corresponds to 64 kbps.

Page 7: Voice and Data Delivery Networks

The 56k Dial-Up Modem

If the telephone company can transmit 64-kbps, does this mean that we users can receive a 64-kbps downstream signal?

Page 8: Voice and Data Delivery Networks

The 56k Dial-Up Modem

If the telephone company can transmit 64-kbps, does this mean that we users can receive a 64-kbps downstream signal?

The answer is NO.

Page 9: Voice and Data Delivery Networks

The 56k Dial-Up Modem

Page 10: Voice and Data Delivery Networks

The 56k Dial-Up Modem

Page 11: Voice and Data Delivery Networks

The 56k Dial-Up Modem

• V.90 standard 1st standard to appear that supported 56,000 bps

dial-up modems

• V.92 modem standard Introduced by ITU after V.90 This standard is a slight improvement over the V.90

standard in two respects.1. the upstream link between the user and the

telephone company is capable of supporting connections up to 48 kbps (as opposed to the 33,600 bps of the V.90 modem)

2. V.92 modem can place a data connection on hold should someone call the user’s telephone number (call waiting)

Page 12: Voice and Data Delivery Networks

Digital Subscriber Line

• Alternative ways to send data through the basic telephone system

• Technology that allows existing twisted pair telephone lines to transmit multimedia materials and high-speed data.

• Transfer speeds can range from hundreds of thousands of bits per second up to several million bits per second.

Page 13: Voice and Data Delivery Networks

DSL basics

• Transmission speed is an important issue.• DSL is capable of a wide range of speeds.• The transfer speed of a particular line

depends on one or more of the following factors -

Carrier providing the service. Distance of your house from the central office of

the local telephone company. DSL service is either symmetric connection or an

asymmetric connection.• DSL is an always-on connection.• It uses a permanent circuit instead of a

switched circuit.

Page 14: Voice and Data Delivery Networks

DSL basics

Type of connection in DSL ServiceSymmetric connection

is one in which the transfer speeds in both directions are equal

Asymmetric connection has a faster downstream transmission speed

than its upstream speed

Page 15: Voice and Data Delivery Networks

DSL basics

• Users are required 4 component to establish a DSL connection DSLAM (Digital Subscriber Line Access

Multiplexer) DSL splitter DSL modem DSL router

Page 16: Voice and Data Delivery Networks

DSL basics

• DSLAM (Digital Subscriber Line Access Multiplexer)

The local telephone company (LEC) must install a special router called a DSLAM (digital subscriber line access multiplexer) within the telephone company’s central office.

• DSL splitter The local telephone company may also install a DSL

splitter on its premises, which combines or splits the DSL circuits (the upstream and downstream channels) with the standard telephone circuit of POTS.

When no splitter is used to separate the DSL signal from the POTS signal, then the service is called splitterless DSL.

Page 17: Voice and Data Delivery Networks

DSL basics

• DSL modem DSL modem is required to convert the DSL signals into

a form that the user workstation or network can understand.

• DSL router DSLAM router at the telephone company’s central office

must be connected to an Internet service provider via a high-speed line.

Page 18: Voice and Data Delivery Networks

DSL basics

Page 19: Voice and Data Delivery Networks

DSL formats

• DSL formats are in use today – referred to as xDSL

Asymmetric digital subscriber line (ADSL) DSL Lite Very high data rate DSL2 (VDSL2) Rate-adaptive DSL (RADSL)

Page 20: Voice and Data Delivery Networks

DSL formats

• Asymmetric digital subscriber line (ADSL) A popular format that transmits the downstream

data at a faster rate than the upstream rate.

• DSL Lite slower format compared to ADSL Also known as Universal DSL, G.Lite, and

splitterless DSL

• Very high data rate DSL2 (VDSL2) Very fast fast format (roughly 100 Mbps

downstream and upstream) over very short distances (less than 300 meters)

Page 21: Voice and Data Delivery Networks

DSL formats

• Rate-adaptive DSL (RADSL) RADSL is a format in which the transfer rate can

vary, depending on noise levels within the telephone line’s local loop

Page 22: Voice and Data Delivery Networks

Cable Modems

• is a high-speed communications services that allows high-speed access to wide area networks such as the Internet via a cable television connection.

• is a physical device that separates the computer data from the cable television video signal, but many people refer to the entire system as a cable modem service.

Page 23: Voice and Data Delivery Networks

Cable Modems

Page 24: Voice and Data Delivery Networks

Cable Modems

• Most cable modems are external devices that connect to the personal computer through a common Ethernet network interface card, which is either provided by the cable company or purchased at most stores that sell computer equipment

• The connection is typically asymmetric.

Page 25: Voice and Data Delivery Networks

Cable Modems

Page 26: Voice and Data Delivery Networks

Cable Modems

• Advantage Cable modems provide high-spee connections to

the Internet and the demand for them is growing rapidly.

• Disadvantage As traffic on Ethernet-based local area networks

increases, there is a decrease in overall throughput.