Question

Explain what a protocol stack is. Define and describe the OSI stack and what each layer is in charge of.

            

Answer 1

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A protocol stack refers to a group of protocols that are runnning concurrently that are employed for the implementation of network protocol suite. The protocols in a stack determine the interconnectivity rules for a layered network model such as in the OSI or TCP/IP models.

What OSI do– It defines the communication process using 7 layers from one endpoint to another endpoint devices. Each layer performs own functionality and forwards to the next layer. The Same process happens at another endpoint.

Advantage of OSI- It divide a big communication process into smaller components.

OSI is the combination of 7 layers, each layer has own functions on data.

OSI Layers-

Layer 7- Application Layer

This layer responsible to provide interface for the users to interface with networking services. Identify the service using Port Number.

Example- Web Browser, Outlook etc.

Layer 6- Presentation Layer

It responsible that how data would be represented. For example, Encoding-decoding, Encryption-decryption, compression-decompression etc.

Example- JPEG, ASCII, WAV, AVI

Layer 5- Session Layer

This layer is responsible for establishing, maintain or terminate the session. Session layer creates a Session between sender and receiver, once the data got transferred it terminate the session. Session ID used to identify the session. From client to server, a data communication process organized by 3 modes: Simplex, Half-Duplex, and Full-Duplex.

Layer 4- Transport Layer

Transport Layer- This layer is responsible for end to end the transportation of data between the application. This layer is Reliable, means It responsible for 3 things: Sequencing, Error Free, and Flow control. Sequencing- data should go in the same sequence and data would be error free and should go with the same flow.

Functions of Transport Layer-

Create a session using 3-way handshaking between sender and receiver before sending the data.
Multiplexing and De-multiplexing
Segmentation
Error Correction
Sequencing
Flow Control
Acknowledge

Layer 3- Network Layer
This layer is responsible to provide a path to data and responsible for logical addressing. This layer used to Route the packet among the network. In this layer, data converts into a packet.

Network layer has two responsibility, Logical Addressing and Path selection (Routing).

Layer 2- Data Link Layer
This layer is responsible data transport between LAN. Data link layer is responsible for error free data transmission, error detection and flow control over the physical layer. In this layer data packed into frames and this process called data framing.

This layer has 2 sub-layer:

LLC: Logical Link Control, provide flow control, error control data transmission (Check Error)

MAC: Media Access Control, provide physical addressing as well as logical topology.

Layer 1- Physical Layer

Physical layer is responsible for a physical medium for data transmission and transfers the data in Bit format ( 0 and 1 Binary) and This layer sends bits and receives bits.

Functions-
Data Rate

Synchronization

Signals

Devices- Network Interface Card (NIC), Hubs etc.