Ethernet protocol basics in Computer Networks - Step-by-Step Execution

Concept Flow - Ethernet protocol basics

Start: Data to send

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Frame creation

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Add header and trailer

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Send frame on cable

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Other devices listen

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Collision detected?

Yes→Wait random time

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Retry send

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Frame received

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Check frame integrity

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Pass data to higher layer

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End

This flow shows how Ethernet frames are created, sent, checked for collisions, and received.

Execution Sample

Computer Networks

1. Create Ethernet frame with data
2. Add header (MAC addresses) and trailer (CRC)
3. Send frame on cable
4. Detect collision? If yes, wait and retry
5. Receive frame and check integrity
6. Pass data to next layer

This sequence shows the basic steps of sending and receiving data using Ethernet protocol.

Analysis Table

Step	Action	Details	Result
1	Create frame	Data + MAC addresses + CRC	Frame ready to send
2	Send frame	Transmit bits on cable	Frame on network
3	Collision check	Is another device sending?	No collision detected
4	Receive frame	Device listens and gets frame	Frame received intact
5	Check integrity	Verify CRC matches	Frame valid
6	Pass data	Send payload to higher layer	Data delivered
7	End	Process complete	Ready for next frame

💡 Process ends after frame is successfully received and data passed on.

State Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	Final
Frame	None	Created with data and addresses	Sent on cable	On cable, no collision	Received by device	Integrity checked	Passed to higher layer
Collision	Unknown	N/A	Checked	No collision	N/A	N/A	N/A

Key Insights - 3 Insights

Why do we add a header and trailer to the data before sending?

The header contains source and destination addresses so devices know where to send and receive data. The trailer has a CRC to check if data got corrupted during transmission. See execution_table step 1.

What happens if two devices send data at the same time?

A collision occurs, detected by devices. They stop sending, wait a random time, then retry. This is shown in the flow after 'Collision detected?'.

How does the receiving device know if the frame is correct?

It uses the CRC in the trailer to check integrity. If the CRC matches, the frame is valid and passed on. See execution_table step 5.

Visual Quiz - 3 Questions

Look at the execution_table, what is the frame status after Step 2?

A Frame is created but not sent

B Frame is sent on the cable

C Frame is received by device

D Frame integrity is checked

💡 Hint

Check the 'Result' column for Step 2 in execution_table.

At which step does the device check for collisions?

A Step 3

B Step 1

C Step 5

D Step 6

💡 Hint

Look at the 'Action' column in execution_table for collision detection.

If a collision is detected, what should happen next according to the concept_flow?

A Frame is passed to higher layer

B Frame is discarded and process ends

C Device waits a random time and retries sending

D Device immediately sends frame again

💡 Hint

See the branch after 'Collision detected?--Yes-->' in concept_flow.

Concept Snapshot

Ethernet sends data in frames with headers (MAC addresses) and trailers (CRC).
Frames are sent on a shared cable.
Devices check for collisions; if detected, they wait and retry.
Receiving devices verify frame integrity before passing data on.
This ensures reliable local network communication.

Full Transcript

Ethernet protocol basics involve creating a data frame that includes the actual data, source and destination addresses, and a checksum called CRC. The frame is sent over a shared cable where multiple devices listen. If two devices send at the same time, a collision occurs, detected by the devices. They then wait a random time before retrying to avoid repeated collisions. When a device receives a frame, it checks the CRC to ensure the data is not corrupted. If valid, the data is passed to the next layer for processing. This process repeats for each frame sent on the network.