The document discusses different types of home internet connections, including dial-up modems, DSL, and cable modems. It describes how 56k dial-up modems worked using both analog and digital signaling to achieve higher speeds. Digital Subscriber Line (DSL) connections transmit data over existing telephone lines at speeds from hundreds of kbps to several mbps using technology like ADSL, VDSL2, and RADSL. Cable modems provide high-speed internet access through a cable television connection and separate computer data from video signals.

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

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

3. 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.

4. The 56k Dial-Up Modem
Did something in the telephone system change to
allow the faster transmission speed, or were the
industry experts wrong?

5. 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.

6. 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.

7. 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?

8. 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.

9. The 56k Dial-Up Modem

10. The 56k Dial-Up Modem

11. 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

12. 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.

13. 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.

14. DSL basics
Type of connection in DSL Service
Symmetric 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

15. DSL basics
• Users are required 4 component to establish a
DSL connection
 DSLAM (Digital Subscriber Line Access Multiplexer)
 DSL splitter
 DSL modem
 DSL router

16. 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.

17. 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.

18. DSL basics

19. 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)

20. 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)

21. 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

22. 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.

23. Cable Modems

24. 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.

25. Cable Modems

26. 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.