Computer networking MCQ

1031. An..... signal is the optical modulation of an STS-n (or STM-n) signal.

Correct Answer: Correct answer is: (A) OC-n.

Exam Relevance: CCNA, CCNP, JNCIA, JNCIS

Difficulty: Moderate

Concept notes: An OC-n signal is the optical carrier level used in SONET/SDH networks to represent the optical modulation of an STS-n (Synchronous Transport Signal) or STM-n (Synchronous Transport Module) signal.

Common Mistakes: Students may confuse OC-n with other types of multiplexing techniques like TDM or FDM, which are not related to optical carrier levels.

Explanations: OC-n stands for Optical Carrier level n, which is a standard for the optical transmission of data in SONET/SDH networks. It is specifically designed to carry the STS-n or STM-n signals, which are the electrical signals used in these networks. The optical modulation of these electrical signals is what creates the OC-n signal, making it the correct answer.

Option Analysis:

Option A: Correct. OC-n is the optical carrier level used to modulate STS-n or STM-n signals.
Option B: Incorrect. TDM-n refers to Time Division Multiplexing, which is a method of transmitting multiple digital signals over a single channel by dividing the signal into distinct time slots, not an optical carrier level.
Option C: Incorrect. FDM-n refers to Frequency Division Multiplexing, which is a method of transmitting multiple signals over a single channel by dividing the signal into distinct frequency bands, not an optical carrier level.
Option D: Incorrect. None of the above is not applicable since OC-n is the correct answer.

1032. The DoD model (also called the TCP/IP stack) has four layers. Which layer of the DoD model is equivalent to the Network layer of the OSI model?

Correct Answer: Correct answer is: (C) Internet.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Easy

Concept notes: The Internet layer of the DoD model is equivalent to the Network layer of the OSI model.

Common Mistakes: Students may confuse the Internet layer with the Application layer or the Network Access layer.

Explanations: The Internet layer in the DoD model is responsible for addressing and routing packets across networks. This is analogous to the Network layer in the OSI model, which also handles addressing and routing. The Internet layer ensures that data packets are sent to the correct destination across different networks, which aligns with the functions of the Network layer in the OSI model.

Option Analysis:

Option A: The Application layer in the DoD model is not equivalent to the Network layer in the OSI model. It deals with user applications and protocols.
Option B: The Host-to-Host layer in the DoD model is equivalent to the Transport layer in the OSI model, not the Network layer.
Option C: The Internet layer in the DoD model is equivalent to the Network layer in the OSI model, as both handle addressing and routing.
Option D: The Network Access layer in the DoD model is equivalent to the Data Link and Physical layers in the OSI model, not the Network layer.

Mnemonic: Internet = Network

1033. In IEEE 802.11, a station with.....mobility is either stationary or moving only inside a BSS

Correct Answer: Correct answer is: (B) No-transition.

Exam Relevance: Computer Networks, Wireless Communications, IEEE 802.11 exams

Difficulty: Easy

Concept notes: In IEEE 802.11, a station with no-transition mobility is either stationary or moving only within a single Basic Service Set (BSS).

Common Mistakes: Students may confuse no-transition with BSS-transition, where a station moves between different BSSs.

Explanations: A station with no-transition mobility is confined to a single BSS. This means the station either remains stationary or moves within the boundaries of the same BSS without changing its association to a different BSS. This is in contrast to BSS-transition, where the station moves between different BSSs, requiring reassociation.

Option Analysis:

Option A: ESS-transition involves moving between different Extended Service Sets (ESS), which is not applicable here.
Option B: No-transition correctly describes a station that remains within a single BSS.
Option C: BSS-transition involves moving between different BSSs, which is not the case here.
Option D: None of the above is incorrect as no-transition is a valid mobility type.

1034. Which statements are true regarding ICMP packets? 1. They acknowledge receipt of a TCP segment. 2. They guarantee datagram delivery. 3. They can provide hosts with information about network problems. 4. They are encapsulated within IP datagrams.

Correct Answer: Correct answer is: (C) 3 and 4.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Moderate

Concept notes: ICMP (Internet Control Message Protocol) is used to send error messages and operational information indicating, for example, that a requested service is not available or that a host or router could not be reached. ICMP packets are encapsulated within IP datagrams and can provide hosts with information about network problems.

Common Mistakes: Students may mistakenly believe that ICMP packets acknowledge receipt of TCP segments or guarantee datagram delivery, which are not true.

Explanations: ICMP packets do not acknowledge receipt of TCP segments; this function is handled by TCP itself. ICMP also does not guarantee datagram delivery; it provides information about network issues and is encapsulated within IP datagrams. Therefore, statements 3 and 4 are true.

Option Analysis:

Option A: Incorrect because ICMP does not acknowledge receipt of TCP segments.
Option B: Incorrect because ICMP does not guarantee datagram delivery.
Option C: Correct because ICMP can provide hosts with information about network problems and is encapsulated within IP datagrams.
Option D: Incorrect because ICMP does not guarantee datagram delivery.

1035. In Frequency Division Multiple Access, data link layer in each station tells its physical layer to make

Correct Answer: Correct answer is: (B) Bandpass signal.

Exam Relevance: Computer Networks, Telecommunications, Digital Communications

Difficulty: Moderate

Concept notes: In Frequency Division Multiple Access (FDMA), the data link layer instructs the physical layer to convert the baseband signal into a bandpass signal for transmission over a shared medium.

Common Mistakes: Students may confuse the term "bandpass signal" with "baseband signal," leading to incorrect selection of option C.

Explanations: In FDMA, the data link layer in each station tells its physical layer to make a bandpass signal. This is because bandpass signals are suitable for transmission over a shared medium, as they occupy a specific frequency band. The bandpass signal is created by modulating the baseband signal onto a carrier frequency, which allows multiple users to share the same medium by using different frequency bands.

Option Analysis:

Option A: A signal is too general and does not specify the type of signal required for FDMA.
Option B: A bandpass signal is the correct choice as it is specifically used in FDMA to allocate different frequency bands for multiple users.
Option C: A baseband signal is not suitable for FDMA as it needs to be converted into a bandpass signal for transmission.
Option D: Both B and C is incorrect because only a bandpass signal is required, not a baseband signal.

1036. A..... error means that two or more bits in the data unit have changed.

Correct Answer: Correct answer is: (B) Burst.

Exam Relevance: Computer Networks, Digital Communications, Data Transmission

Difficulty: Moderate

Concept notes: Burst error refers to a situation where multiple bits in a data unit are altered, typically due to a single event or interference.

Common Mistakes: Students may confuse burst errors with single-bit errors, which only affect one bit, or double-bit errors, which affect exactly two bits.

Explanations: A burst error occurs when two or more bits in a data unit are changed due to a single event, such as a noise pulse or a transmission error. This is different from single-bit or double-bit errors, which affect only one or exactly two bits, respectively. Burst errors are more complex and can affect a range of bits, making them a significant concern in data transmission and storage systems.

Option Analysis:

Option A: Double-bit errors affect exactly two bits, not two or more.
Option B: Burst errors affect two or more bits, fitting the description.
Option C: Single-bit errors affect only one bit, not two or more.
Option D: This is not a valid option as the correct answer is provided.

Mnemonic: Burst = Bunch of bits

1037. Frame type that refers to High-level Data Link Control error detection field is

Correct Answer: Correct answer is: (A) Frame Check Sequence field.

Exam Relevance: Computer Networks, Data Communications, Network Security

Difficulty: Easy

Concept notes: The Frame Check Sequence (FCS) field is used for error detection in High-level Data Link Control (HDLC) frames.

Common Mistakes: Students may confuse the FCS field with the Control field, which is used for flow and error control, not error detection.

Explanations: The Frame Check Sequence (FCS) field in HDLC frames is specifically designed for error detection. It contains a cyclic redundancy check (CRC) value that is calculated over the entire frame, including the address, control, and information fields. This allows the receiver to verify the integrity of the received frame by recalculating the CRC and comparing it to the FCS value. If the values do not match, an error is detected.

Option Analysis:

Option A: Correct. The Frame Check Sequence field is used for error detection in HDLC frames.
Option B: Incorrect. The Control field is used for flow and error control, not error detection.
Option C: Incorrect. The Flag field is used to mark the beginning and end of a frame, not for error detection.
Option D: Incorrect. The Information field contains the actual data being transmitted, not error detection mechanisms.

Mnemonic: FCS - Find Corruption in Sequence

1038. Find parity bit for 1001011

Correct Answer: Correct answer is: (A) 0.

Exam Relevance: Computer Networks, Digital Logic, Data Communication

Difficulty: Easy

Concept notes: Parity bit is used to detect errors in data transmission. For even parity, the number of 1s in the data plus the parity bit should be even.

Common Mistakes: Students often forget to count the parity bit itself when determining the number of 1s.

Explanations: The given data is 1001011. Count the number of 1s in the data: 1 + 0 + 0 + 1 + 0 + 1 + 1 = 4. Since 4 is already even, the parity bit should be 0 to maintain even parity.

Option Analysis:

Option A: Correct, as the parity bit is 0 to maintain even parity.
Option B: Incorrect, as adding 1 would make the total number of 1s odd.
Option C: Incorrect, as the parity bit can only be 0 or 1.
Option D: Incorrect, as 0 is the correct parity bit.

Mnemonic: Even parity, even count, zero to stay.

1039. PPP consists of.....components

Correct Answer: Correct answer is: (B) Three (encapsulating, a link control protocol, NCP ).

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Easy

Concept notes: PPP (Point-to-Point Protocol) is a data link layer protocol used for transporting network layer protocols over point-to-point links. It consists of three main components: encapsulation, a link control protocol, and a network control protocol (NCP).

Common Mistakes: Students may confuse the components of PPP with other protocols or may not be aware of the specific roles of each component.

Explanations: PPP consists of three components: encapsulation, which is the process of formatting data for transmission; a link control protocol (LCP), which establishes, configures, and tests the data link connection; and a network control protocol (NCP), which negotiates and configures the network layer protocols. The Domain Name System (DNS) and Simple Network Control Protocol (SNCP) are not components of PPP.

Option Analysis:

Option A: Incorrect because PPP does not include the Domain Name System (DNS) as a component.
Option B: Correct as it accurately lists the three components of PPP.
Option C: Incorrect because Simple Network Control Protocol (SNCP) is not a component of PPP.
Option D: Incorrect because PPP does have defined components.

1040. Unlike User Datagram Protocol (UDP), Transmission Control Protocol (TCP) has Services which is

Correct Answer: Correct answer is: (A) Connection Oriented.

Exam Relevance: CCNA, CISSP, CompTIA Network+

Difficulty: Easy

Concept notes: TCP is a connection-oriented protocol, meaning it establishes a connection before data transmission begins.

Common Mistakes: Students often confuse TCP with UDP, which is connectionless.

Explanations: TCP is connection-oriented because it establishes a reliable connection between two endpoints before data transmission. This ensures that data packets are sent in order and that any lost packets are retransmitted. In contrast, UDP is connectionless and does not establish a connection before sending data, making it less reliable but faster.

Option Analysis:

Option A: Correct. TCP is connection-oriented, establishing a connection before data transmission.
Option B: Incorrect. UDP is connectionless, not TCP.
Option C: Incorrect. This is not a valid term in networking.
Option D: Incorrect. This is not a valid term in networking.

Mnemonic: TCP: Trusty Connection Provider

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Computer networking MCQ - Set 104

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