CS Free MCQ Bank

[ Option C ]

The default gateway is used to forward network packets from one network to another, which is a function of routing. Routing and logical addressing using IP addresses are handled at the Network Layer (Layer 3) of the OSI model.

[ Option C ]

ALOHA is a Random-Access Protocol used in computer networks for sharing a common communication channel.
It allows multiple users or stations to send data whenever they want, but collisions can occur if two or more stations send data at the same time.
Throughput means the rate of successful data transmission over a communication channel.

• G = The total transmission attempts per slot.
• e^−G = The probability that no other station transmits in the same slot, i.e., no collision.

OTHER RANDOM-ACCESS PROTOCOLS:

[ Option B ]

The OSI (Open Systems Interconnection) model has seven layers, with the Physical Layer at the bottom (Layer 1).
The physical layer main job is to send raw bits (0s and 1s) from one device to another through a physical medium like cables, radio waves, or fiber optics. It does not understand data, packets, or addresses, it only deals with electrical signals, light signals, or radio signals.

[ Option A ]

In computer networks, the Data Link Layer is the second layer of the OSI (Open Systems Interconnection) model. Its main role is to ensure reliable data transfer between two directly connected nodes.
To perform its functions efficiently, the Data Link Layer is divided into two sublayers:
Logical Link Control (LLC):

• Handles flow control and error control.
• Ensures that frames are delivered accurately and in sequence.
• Acts as an interface between the Network Layer and Data Link Layer.
• It focuses on logical communication, not the physical medium.

Media / Medium Access Control (MAC):

• Controls how devices access the transmission medium.
• Decides which device gets permission to send data.
• Uses MAC addresses.
• It focuses on sharing the physical medium efficiently.

[ Option D ]

In computer networks, different types of addresses are used at different levels to identify devices and processes. A Port Address is used to identify a specific process (Program or Service) running on a host system.

• Port Addresses or Port Numbers act like apartment numbers within a building.

For example, when you open a website, your browser (process) uses a port number, like 80 for HTTP, so that data reaches the correct application.

• Logical Address (IP Address): Used to identify a device or host on a network, not a specific process.
• Physical Address (MAC Address): Used to identify a hardware device within a local network.
   

[ Option A ]

The OSI (Open System Interconnection) model is a standard networking model that divides network communication into seven layers. Each layer performs specific functions during data communication.

• Physical Layer.
• Data Link Layer.
• Network Layer.
• Transport Layer.
• Session Layer.
• Presentation Layer.
• Application Layer.

Statement I:
“The session layer provides means of establishing, maintaining and terminating a session between two end users.”
This statement is correct. The Session Layer is responsible for:

• Establishing communication sessions.
• Maintaining the session.
• Terminating the session after communication is completed.

E.g.:

• VIDEO Conferencing.
• Remote Login Sessions.

Statement II:
“Data Link layer sets up a logical path between the source and destination computer of the network.”
This statement is incorrect. Establishing the logical path between source and destination is the function of the Network Layer, not the Data Link Layer.
The Data Link Layer mainly:

• Handles Framing.
• Error Detection.
• Node-to-Node Delivery.

[ Option A ]

The Data Link Layer is responsible for Node-To-Node Delivery and ensures reliable communication over a physical link. It performs key functions such as Framing, Error Control, and MAC Addressing, all of which are essential for organizing data into frames, detecting, or correcting errors, and identifying devices on the network.

However, Congestion Control is typically not a function of the data link layer; it is primarily handled by higher layers such as the network or transport layer to manage traffic load and avoid network congestion.

[ Option A ]

[ Option A ]

Protocols such as SMTP (Simple Mail Transfer Protocol), HTTP (Hypertext Transfer Protocol), and FTP (File Transfer Protocol) operate at the Application Layer of the OSI and TCP/IP models. The application layer provides network services directly to end-user applications and manages communication between users and networks.
SMTP is responsible for email transmission, HTTP is used for accessing and transferring web pages, and FTP allows file transfers between systems.

[ Option C ]

The OSI model consists of different layers, each having specific responsibilities in network communication. 

• The Network Layer handles routing and path selection.
• The Transport Layer ensures end-to-end communication between processes. 
• The Application Layer provides services directly to users and presents meaningful data.

However, the Session Layer is responsible for establishing, maintaining, and terminating communication sessions between applications. It does not handle congestion control. Congestion control is mainly managed by the Transport Layer.

[ Option D ]

The Media Access Control (MAC) layer is a sublayer of the Data Link Layer, responsible for controlling how multiple devices share a common transmission medium. Its main function is to decide who can transmit data and when, especially in a shared network.
To manage this, the MAC layer uses different access protocols, which help avoid or handle collisions when multiple devices try to send data simultaneously.
Protocols Used by MAC Layer:

[ Option D ]

Reliable data transfer means ensuring that data reaches the receiver without errors, without loss, and in the correct order.
Reliable data transfer is implemented by the Transport Layer in the OSI model. The transport layer is responsible for providing end-to-end communication services for applications. 
It ensures reliable delivery of data through mechanisms such as error detection and correction, flow control, segmentation, acknowledgment of received data, and retransmission of lost or corrupted segments. 
Protocols like TCP (Transmission Control Protocol) at this layer offer connection-oriented and reliable communication by managing data packets and maintaining the order and integrity of the data transmitted between sender and receiver.