https://www.stuvia.com/user/performance
BROADBAND SYSTEMS: DOCSIS, DSL TROUBLESHOOTING, AND FIBER
INSTALLATION Original Questions with Answers and Rationales
Section 1: DOCSIS Details (Questions)
1. What does the acronym DOCSIS stand for?
A. Digital Optical Cable System Interface Standard
B. Data Over Cable Service Interface Specification
C. Direct Online Cable Service Internet System
D. Digital Over Coaxial Service Integration Standard
Answer: B
Rationale: DOCSIS (Data Over Cable Service Interface
Specification) is the international standard developed by
CableLabs for transmitting data over cable TV systems.
2. Which layer of the OSI model does DOCSIS primarily
address?
A. Application layer
B. Physical layer and Data Link layer
C. Transport layer
D. Network layer
Answer: B
Rationale: DOCSIS defines the physical (PHY) and media
access control (MAC) layers for cable modem
communication, corresponding to OSI Layers 1 and 2.
,https://www.stuvia.com/user/performance
3. What is the maximum downstream channel bonding
supported by DOCSIS 3.0?
A. 4 channels
B. 8 channels
C. 16 channels
D. 32 channels
Answer: D
Rationale: DOCSIS 3.0 supports bonding up to 32
downstream channels (and 8 upstream), enabling
downstream speeds up to about 1 Gbps depending on
channel width.
4. DOCSIS 3.1 introduced which modulation scheme for
downstream transmission?
A. QPSK only
B. 64-QAM only
C. OFDM (Orthogonal Frequency Division Multiplexing)
D. FM modulation
Answer: C
Rationale: DOCSIS 3.1 uses OFDM for downstream and
OFDMA for upstream, allowing more efficient use of
spectrum and higher speeds up to 10 Gbps downstream.
5. What is the typical downstream frequency range used by
DOCSIS cable systems?
A. 5–42 MHz
, https://www.stuvia.com/user/performance
B. 50–100 MHz
C. 88–1002 MHz or higher
D. 1–5 GHz
Answer: C
Rationale: Downstream channels typically occupy
frequencies from about 88 MHz to 1 GHz or higher, while
upstream uses lower frequencies (5–42 MHz in North
America).
6. Which device at the cable provider's facility communicates
with cable modems and manages bandwidth allocation?
A. DSLAM
B. CMTS (Cable Modem Termination System)
C. ONT
D. Router
Answer: B
Rationale: The CMTS is located at the cable headend or
hub and manages all cable modems on a given node,
controlling upstream and downstream traffic.
7. A cable modem's upstream frequency range in North
America is typically:
A. 5–42 MHz
B. 88–860 MHz
C. 1–2 GHz
D. 50–100 MHz
BROADBAND SYSTEMS: DOCSIS, DSL TROUBLESHOOTING, AND FIBER
INSTALLATION Original Questions with Answers and Rationales
Section 1: DOCSIS Details (Questions)
1. What does the acronym DOCSIS stand for?
A. Digital Optical Cable System Interface Standard
B. Data Over Cable Service Interface Specification
C. Direct Online Cable Service Internet System
D. Digital Over Coaxial Service Integration Standard
Answer: B
Rationale: DOCSIS (Data Over Cable Service Interface
Specification) is the international standard developed by
CableLabs for transmitting data over cable TV systems.
2. Which layer of the OSI model does DOCSIS primarily
address?
A. Application layer
B. Physical layer and Data Link layer
C. Transport layer
D. Network layer
Answer: B
Rationale: DOCSIS defines the physical (PHY) and media
access control (MAC) layers for cable modem
communication, corresponding to OSI Layers 1 and 2.
,https://www.stuvia.com/user/performance
3. What is the maximum downstream channel bonding
supported by DOCSIS 3.0?
A. 4 channels
B. 8 channels
C. 16 channels
D. 32 channels
Answer: D
Rationale: DOCSIS 3.0 supports bonding up to 32
downstream channels (and 8 upstream), enabling
downstream speeds up to about 1 Gbps depending on
channel width.
4. DOCSIS 3.1 introduced which modulation scheme for
downstream transmission?
A. QPSK only
B. 64-QAM only
C. OFDM (Orthogonal Frequency Division Multiplexing)
D. FM modulation
Answer: C
Rationale: DOCSIS 3.1 uses OFDM for downstream and
OFDMA for upstream, allowing more efficient use of
spectrum and higher speeds up to 10 Gbps downstream.
5. What is the typical downstream frequency range used by
DOCSIS cable systems?
A. 5–42 MHz
, https://www.stuvia.com/user/performance
B. 50–100 MHz
C. 88–1002 MHz or higher
D. 1–5 GHz
Answer: C
Rationale: Downstream channels typically occupy
frequencies from about 88 MHz to 1 GHz or higher, while
upstream uses lower frequencies (5–42 MHz in North
America).
6. Which device at the cable provider's facility communicates
with cable modems and manages bandwidth allocation?
A. DSLAM
B. CMTS (Cable Modem Termination System)
C. ONT
D. Router
Answer: B
Rationale: The CMTS is located at the cable headend or
hub and manages all cable modems on a given node,
controlling upstream and downstream traffic.
7. A cable modem's upstream frequency range in North
America is typically:
A. 5–42 MHz
B. 88–860 MHz
C. 1–2 GHz
D. 50–100 MHz
