Cisco 642-825 Free Demo – 3
Posted on | January 27, 2010 | No Comments
Q13
Which ADSL modulation type:
1. is prominent in residential applications has 120 subchannels 2.
doesn’t need a splitter 3.
has a 1.5 Mbps maximum downstream speed? 4.
A. CAP
B. DMT
C. G.Lite
D. PPPoA
E. PPPoE
Answer: C
Explanation:
ITU GLITE (ITU G.992.2) describes splitterless Asymmetric Digital Subscriber Line (ADSL) Transceivers on
a metallic twisted pair that allows high-speed data transmission between the Central Office (ATU-C) and
the customer end remote terminal (ATU-R).
G.LITE can provide ADSL transmission simultaneously on the same pair with voice (band) service, ADSL
transmission simultaneously on the same pair with ISDN services (G.961 Appendix I or II); or ADSL
transmission on the same pair with voice band transmission and with TCM-ISDN (G.961 Appendix III) in an
adjacent pair.G.992.2 supports a maximum 1.536 Mbps downstream and 512 kbps upstream net data rate.
Leading the way in IT testing and certification tools, www.exambible.com
G.LITE uses discrete Multitone (DMT) line code. DMT is based in the use of the IFFT to generate a set of
sub-channels, and transmit information in each sub-channel independently. Figure 1 shows the G.LITE
spectrum with indication of the POTS, upstream pilot tone, downstream pilot tone, subcarrier spacing, and
number of subcarriers for the upstream and downstream direction. Dividing the available bandwidth into a
set of independent, orthogonal subchannels are the key to DMT performance. By measuring the SNR of each
subchannel and then assigning a number of bits based on its quality, DMT transmits data on subcarriers
with good SNRs and avoids regions of the frequency spectrum that are too noisy or severely attenuated.
The underlying modulation technique is based on quadrature amplitude modulation (QAM). Each subchannel is
4.3125 kHz wide and is capable of carrying up to 15 bits. The downstream is up to 552 kHz, offering 122
subchannels, and the upstream from 26 to 138 kHz, offering 25 upstream subchannels.
Reference: http://www.vocal.com/data_sheets/full/glite.pdf
Q14
Certain physical factors are capable of severely limiting the maximum speed available on a DSL
connection. Which of the following describe the factors that are capable of it? (Choose all that apply)
A. Number of telephones attached to the local loop.
B. Gauge of wire used on the local loop.
C. Distance between the CPE and the DSLAM.
D. Bridge taps in the local loop.
E. Loading coils in the subscriber’s line.
Answer: B, C
Explanation:
DSL is a highly distance-sensitive technology. As the distance from the CO increases, the signal quality
and connection speeds decrease. ADSL service is limited to a maximum distance of 18,000 feet (5460 m)
between the DSL CPE and the DSLAM, although many ADSL providers place an even lower limit on the distance
to ensure quality. The 18,000-foot distance limitation for DSL is not a limitation for voice telephone
calls, but for data transmission. The telco uses small amplifiers, called loading coils, to boost voice
signals. Loading coils have a nasty tendency to disrupt DSL data signals. This means that if there are
loading coils in the loop between the CPE and CO, you probably are not within an area that can receive
DSL service.
Reference:
Leading the way in IT testing and certification tools, www.exambible.com
Cisco Press – BCRAN 821 – Exam Certification Guide 2004 (ISBN 1-587208) Page 247
Q15
A local Internet Service Provider is going to start offering ADSL with 640 kbps upload speed and 4Mbps
download speeds. They have retained you to help in their advertisement campaign to help them find their
target market. What groups of users should you target your marketing efforts to? (Choose two)
A. Central data processing facilities receiving simultaneous uploads of data from remote offices.
B. Support organizations providing ftp services for software distribution and documentation.
C. Small home offices requiring 24 hour connection to the Internet for email and web communication.
D. Web services companies providing dynamic web content serving, including video-on-demand.
Answer: A, C
Explanation:
Based on the expanding number of options currently and coming soon for the broadband market, competition
for home and remote user dollars has reached a frenzied state. The deployment of broadband and similar
technologies has involved quite a large amount of trial and error. The competition has seen the emergence
of two primary services for widespread deployment. These are Cable and DSL.
Loosely defined, DSL is a technology that exploits unused frequencies on copper telephone lines to
transmit traffic, typically at multimegabit speeds. DSL uses existing telephone wiring, without requiring
any additional cabling resources. It has the capability to allow voice and high-speed data to be sent
simultaneously over the same copper pair.
The service is always available, so the user does not have to dial in or wait for call setup.
DSL technologies can be broken down into two fundamental classifications: asymmetric (ADSL) and symmetric
(SDSL). As the name implies, ADSL uses higher downstream rates and lower upstream rates. In contrast,
SDSL uses the same downstream and upstream rates. ADSL is the most commonly deployed DSL technology, and
is the primary focus of the DSL portion of the CCNP Remote Access Exam.
Incorrect Answers:
B: In order to maximize the use of an FTP server, you would want a greater upload speed, since the
majority of users will be downloading files from the FTP server.
Leading the way in IT testing and certification tools, www.exambible.com
D: Again, we would want to ensure that the upload speed was as large as possible, due to the fact that
the majority of the bandwidth will be consumed as uploads to the end users.
Reference:
Cisco Press – BCRAN 821 – Exam Certification Guide 2004 (ISBN 1-587208) Page 245 to 247
Q16
What’s true about the G.Lite (G.922) ADSL ITU standard?
A. It offers equal bandwidth for upstream and downstream data traffic.
B. It has limited operating range of less than 4,500 feet.
C. It was developed specifically for the consumer market segment requiring higher
download speeds.
D. Signals cannot be carried on the same wire as POTS signals.
E. All of the above
Answer: C
Explanation:
G.Lite is the informal name for what is now a standard way to install Asymmetric Digital Subscriber Line
(ADSL) service. Also known as Universal ADSL, G.Lite makes it possible to have Internet connections to
home and business computers at up to 1.5 Mbps (millions of bits per second) over regular phone lines.
Even at the lowest downstream rate generally offered of 384 Kbps (thousands of bits per second), G.Lite
is about seven times faster than regular phone service with a V.90 modem and three times faster than an
Integrated Services Digital Network (ISDN) connection. Upstream speeds from the computer are at up to 128
Kbps. (Theoretical speeds for ADSL are much higher, but the data rates given here are what is
realistically expected.) With G.Lite, your computer’s analog-to-digital modem is replaced with an “ADSL
modem.” and the transmission from the phone company is digital rather than the analog tranmission of
“plain old telephone service.” G.Lite is also known as “splitterless DSL” because, unlike other DSL
technologies, it does not require that a technician come to install a splitter, a device that separates
voice from data signals, at the home or business (sometimes referred to as “the truck roll”).
The G.Lite standard is officially known as G.992.2.
DSL technologies can be broken down into two fundamental classifications: asymmetric (ADSL) and symmetric
(SDSL). As the name implies, ADSL uses higher downstream rates and lower upstream rates. In contrast,
SDSL uses the same downstream and upstream rates. ADSL is the most commonly deployed DSL technology, and
is the primary focus of the DSL portion of the CCNP Remote Access Exam.
Leading the way in IT testing and certification tools, www.exambible.com
DSL is a highly distance-sensitive technology. As the distance from the CO increases, the signal quality
and connection speeds decrease. ADSL service is limited to a maximum distance of 18,000 feet (5460 m)
between the DSL CPE and the DSLAM, although many ADSL providers place an even lower limit on the distance
to ensure quality.
References:
Cisco Press – BCRAN 821 – Exam Certification Guide 2004 (ISBN 1-587208) Page 245 to 247
http://whatis.techtarget.com/definition/0,,sid9_gci212198,00.html
Refecener: Exambible 642-825
More Cisco Exam Links: 642-901 642-825 640-816
Related Posts
- Cisco Certification Exam Exercises 40-50: TCP / IP
- Cisco Certified Learning Summary – CCNA Difficulty Analysis
- Exambible Cisco CCNA Certificate
- Cisco 642-825 Free Demo – 7
- Cisco 642-825 Free Demo – 1
- Cisco 642-825 Free Demo – 5
- Cisco 642-825 Free Demo – 0
- Cisco 642-825 Free Demo – 6
- Cisco 642-825 Free Demo – 2
- Cisco 642-825 Free Demo – 4