Computer Network

CN Unit 2 Part 8 MCQs

PREV
NEXT
Distribute Education
Menu

UNIT 2: Physical Layer

Physical Layer: Transmission media, Signal transmission and encoding, Network performance and transmission impairments, Switching techniques and multiplexing, Overview of PSTN, ISDN, and ATM

Q141 – In SONET, the duration of any frame is
  1. 110
  2. 120
  3. 125
  4. 135

Ans – (3)

Explanation –

SONET (Synchronous Optical Network) is a standardized digital communication protocol used to transmit large amounts of data over optical fiber. It ensures high-speed and high-capacity data transfer, making it ideal for telecommunications.

Frame Duration – Each frame in SONET has a fixed duration of 125 microseconds. This is equivalent to 8000 frames per second, aligning with the standard telecommunication systems’ pulse code modulation (PCM) rate of 8000 samples per second.

Q142 – At the optical source, the signal is changed from an electronic form into an
  1. Absolute form
  2. Optical Form
  3. Dynamic form
  4. Resolved form

Ans – (2)

Explanation –

In optical communication systems, the process involves converting electronic signals into optical signals using devices like laser diodes or LEDs (Light Emitting Diodes). This conversion is essential for transmitting data over optical fiber cables, which use light to carry information.

Q143 – The SONET Layer that is responsible for the movement of a signal across a physical line is called
  1. Line Layer
  2. Section Layer
  3. Path Layer
  4. Photonic Layer

Ans – (1)

Explanation –

The Line Layer in SONET is responsible for the movement of a signal across a physical line.

SONET Layers and Their Responsibilities

  1. Section Layer – Manages the movement of a signal across a physical section. Handles framing, scrambling, and error control for the transmission path.
  2. Line Layer – Ensures the proper movement of the signal across a physical line. Focuses on synchronization, multiplexing, and line maintenance. It is responsible for the transportation of the signal between network elements.
  3. Path Layer – Responsible for the end-to-end transmission of data. Manages the path overhead, which includes monitoring the status and quality of the signal from the source to the destination.
  4. Photonic Layer – Manages the transmission of the optical signal. Converts electronic signals into optical signals for transmission and vice versa at the receiver end. It deals with the physical medium and light modulation.
Q144 – SONET/SDH is a synchronous network using synchronous
  1. TDM multiplexing
  2. CDMA multiplexing
  3. TDM demultiplexing
  4. CDMA demultiplexing

Ans – (1)

Explanation –

SONET (Synchronous Optical Network) and SDH (Synchronous Digital Hierarchy) are synchronous networks that use synchronous Time Division Multiplexing (TDM) for multiplexing.

TDM Multiplexing – Synchronous TDM is used to combine multiple data streams into a single signal over a shared transmission medium. In SONET/SDH, this involves the synchronization of different data streams into fixed time slots, creating a structured and orderly multiplexed signal.

Q145 – In SONET, the basic building block of a frame is called a
  1. Byte
  2. Bit
  3. STS-1
  4. OC-1

Ans – (3)

Explanation –

In SONET (Synchronous Optical Network), the basic building block of a frame is called an STS-1 (Synchronous Transport Signal level 1).

STS-1 is the fundamental unit of SONET’s hierarchical structure. It represents the smallest unit of data that can be transported across the SONET network.

Q146 – Which layer of the SONET architecture is responsible for end-to-end communication across the SONET network?
  1. Line Layer
  2. Section Layer
  3. Path Layer
  4. Photonic Layer

Ans – (3)

Explanation –

In SONET (Synchronous Optical Networking), the Path Layer is responsible for end-to-end communication across the SONET network. This layer manages the payload (data) and ensures that it is correctly delivered from the source to the destination, handling tasks like framing and synchronization at the end-to-end level.

Q147 – In SDH, the basic transmission unit is called a
  1. STM-1
  2. STS-1
  3. OC-1
  4. DS-1

Ans – (1)

Explanation –

In SDH (Synchronous Digital Hierarchy), the basic transmission unit is called an STM-1 (Synchronous Transport Module level 1). It represents the fundamental unit of transmission in SDH, with a data rate of 155.52 Mbps.

Other options are –

  • STS-1 (Synchronous Transport Signal level 1) is used in SONET, which is equivalent to STM-1 in SDH.
  • OC-1 (Optical Carrier level 1) is also used in SONET and is the optical equivalent of STS-1.
  • DS-1 (Digital Signal level 1) is a different hierarchy used in T-carrier systems and is not directly related to SDH or SONET.
Q148 – The _______ Layer is responsible for the framing and synchronization of the SONET signal.
  1. Section
  2. Line
  3. Path
  4. Network

Ans – (1)

Explanation –

In SONET (Synchronous Optical Network), the Section Layer is responsible for the framing and synchronization of the SONET signal. This layer manages the transmission of signals over the physical link between network nodes.

Its duties include

Framing – Adding and managing overhead information necessary for synchronization and error correction.

Synchronization – Ensuring that data is properly synchronized and aligned between the sending and receiving ends of the link.

Q149 – The _______ Layer is responsible for multiplexing and demultiplexing of signals in SONET.
  1. Section
  2. Line
  3. Path
  4. Photonic

Ans – (2)

Explanation –

In SONET (Synchronous Optical Network), the Line Layer is responsible for multiplexing and demultiplexing signals.

Line Layer handles the multiplexing of data from lower-level signals into a higher-level signal and the demultiplexing of higher-level signals into lower-level signals. It is also responsible for managing the line overhead, including error monitoring and performance reporting.

Q150 – In SONET, the synchronous payload envelope (SPE) is transported within the
  1. STS frame
  2. STM frame
  3. OC frame
  4. DS frame

Ans – (1)

Explanation –

In SONET (Synchronous Optical Network), the Synchronous Payload Envelope (SPE) is transported within the STS (Synchronous Transport Signal) frame.

This is the fundamental frame structure used in SONET to carry data. The STS frame includes various overhead bytes and a payload area where the SPE is located.

Q151 – A major advantage of SONET/SDH is that it
  1. Supports asynchronous transmission
  2. Allows for easy multiplexing of different signals
  3. Is limited to low data rates
  4. Uses only electrical signals

Ans – (2)

Explanation –

One of the major advantages of SONET (Synchronous Optical Network) and SDH (Synchronous Digital Hierarchy) is their ability to allow for easy multiplexing of different signals.

Multiplexing – SONET/SDH standards provide a structured and synchronous framework that facilitates the combining of multiple data streams into a single high-speed signal. This is done using a standardized frame structure, which simplifies the integration of various data types and speeds into a unified transport system.

Q152 – In the context of SONET, a BLSR stands for
  1. Bidirectional Line-Switched Ring
  2. Basic Line-Switching Rate
  3. Binary Line-Switching Repeater
  4. Broadband Line-Switched Router

Ans – (1)

Explanation –

In SONET (Synchronous Optical Network), BLSR stands for Bidirectional Line-Switched Ring. This is a network topology used to ensure fault tolerance and high availability.

Q153 – In SONET, the function of the Automatic Protection Switching (APS) protocol is to
  1. Enhance synchronization
  2. Provide fault tolerance
  3. Improve signal quality
  4. Increase data rate

Ans – (2)

Explanation –

In SONET (Synchronous Optical Network), the Automatic Protection Switching (APS) protocol is designed to provide fault tolerance by ensuring that network services remain operational even if a failure occurs.

APS continuously monitors the network for faults. If a fault is detected on the primary path, APS automatically switches traffic to a backup or secondary path.

Q154 – A key difference between SONET and SDH is
  1. SONET is used globally, while SDH is used only in North America.
  2. SONET and SDH are identical standards with no differences.
  3. SONET uses the STS frame structure, while SDH uses the STM frame structure.
  4. SONET supports only electrical signals, while SDH supports optical signals.

Ans – (3)

Explanation –

SONET: Uses the STS (Synchronous Transport Signal) frame structure. It is primarily used in North America.

SDH: Uses the STM (Synchronous Transport Module) frame structure. It is used in other parts of the world, including Europe and Asia.

Q155 – Which SONET/SDH layer is responsible for converting electrical signals into optical signals and vice versa?
  1. Line Layer
  2. Section Layer
  3. Path Layer
  4. Photonic Layer

Ans – (4)

Explanation –

In SONET/SDH, the Photonic Layer (also known as the Optical Layer) is responsible for converting electrical signals into optical signals and vice versa. This layer deals with the physical transmission of data over optical fiber, including the modulation and demodulation of light signals.

Q156 – What is the purpose of the pointer in a SONET frame?
  1. To identify the beginning of the frame
  2. To adjust the phase of the payload
  3. To indicate the end of the frame
  4. To measure signal strength

Ans – (2)

Explanation –

In SONET (Synchronous Optical Network), the pointer is used to manage the alignment of the payload within the frame. Since SONET frames are designed to be synchronous, the pointer helps in adjusting the phase of the payload relative to the frame to accommodate variations in payload size or timing. This ensures that the payload is correctly aligned within the frame for accurate transmission and reception.

Q157 – The minimum overhead information required to manage a SONET/SDH network is found in the
  1. Path overhead
  2. Line overhead
  3. Section overhead
  4. Management overhead

Ans – (3)

Explanation –

In SONET/SDH, the section overhead is responsible for managing and monitoring the transmission of the signal across a physical section. It contains critical information required for the proper operation and maintenance of the network segment, including error checking, performance monitoring, and signal quality assessment.

Q158 – SONET/SDH networks provide a high degree of
  1. Asynchrony
  2. Synchrony
  3. Redundancy
  4. Latency

Ans – (2)

Explanation –

SONET/SDH networks provide a high degree of synchrony. This is one of the key features of SONET (Synchronous Optical Network) and SDH (Synchronous Digital Hierarchy).

Q159 – In Sonet Network, the data is sent over the working line until it fails, is
  1. One-Plus-One APS
  2. One-to-One APS
  3. One-to-Many APS
  4. Both 1 and 2

Ans – (2)

Explanation –

One-to-One APS – In this approach, there is a dedicated backup line (protection line) for each working line (active line). The data is transmitted over the working line, and if it fails, the system automatically switches to the backup line.

Q160 – SONET defines a hierarchy of electrical signaling levels called
  1. Synchronous Transport System
  2. Synchronous Transport Station
  3. Synchronous Transport Signals
  4. Synchronous Transport Solution

Ans – (3)

Explanation –

SONET defines a hierarchy of electrical signalling levels called Synchronous Transport Signals.

Synchronous Transport Signals (STS) – SONET (Synchronous Optical Network) uses the STS hierarchy to define various levels of data rates and signalling. Each level of STS corresponds to a specific data rate and is used for multiplexing lower-level signals into a higher-level signal.

PREV
NEXT

BOOKS

Computer-Network books

 

GATE Study Material
Previous Year Paper
Assignements