Network Protocols: OSI Layers, Addressing, and Encapsulation Processes

What is a network protocol?

A set of rules for exchanging data in a structured format.

What are the two principal functions of a network protocol?

Addressing and encapsulation.

What does the addressing function in a network protocol do?

Describes where data messages should go, identifying nodes and rules for sending and receiving messages.

What is encapsulation in the context of network protocols?

Describes how data messages should be packaged for transmission, adding headers to the payload data.

What is a protocol data unit (PDU)?

A 'chunk' of data formed by adding headers to the data payload at each layer.

What is the process called when a message is sent from one node to another?

Encapsulation: The message travels down the stack of layers on the sending node, reaches the receiving node, and then passes up the stack.

What happens at each layer during the sending process? (except Physical)

Each layer adds a header to the data payload, forming a protocol data unit (PDU).

What is the role of the Physical layer in data transmission?

It transmits the stream of bits making up the frame as a modulated electrical signal.

What is decapsulation?

The reverse process of encapsulation where the receiving node extracts headers and data from the received stream.

How does the receiving node process the incoming data? (Decapsulation)

It decodes the Ethernet frame, extracts the IP packet, resolves the IP header, and continues to extract TCP and Application headers until it retrieves the application data.

What is meant by same layer interaction in network protocols?

Communication between nodes at the same layer, requiring both nodes to run the same protocol.

What is adjacent layer interaction?

When each layer provides services for the layer above and uses the services of the layer below.

What is an example of an application protocol mentioned in the notes?

HyperText Transfer Protocol (HTTP).

What protocol adds a header at the Transport layer?

Transmission Control Protocol (TCP).

What protocol wraps the TCP segment at the Network layer?

Internet Protocol (IP).

What is the Data Link layer responsible for?

Encapsulating the IP packet in an Ethernet frame.

What is the significance of using the same protocol at each layer for communication?

It ensures that two nodes can communicate effectively.

What happens to the headers added during encapsulation when data is received?

They are removed in the decapsulation process.

Why is encapsulation compared to an envelope?

Because each layer requires its own 'envelope' to package the data for transmission.

What is the first step in the sending process of a message?

Data is generated by an application, such as HTTP.

What is the last step in the receiving process of a message?

The extracted HTTP application data is processed by a software program, such as a web browser or web server.