Ethernet Essentials: A Deep Dive into Networking Fundamentals

 

• Ethernet is a widely used networking technology employed for sharing data and facilitating communication among devices within a Local Area Network (LAN). It adheres to the IEEE standard 802.3 and typically employs a Bus topology.
  
  
  
• Utilizing the CSMA/CD (Carrier Sense Multiple Access/Collision Detection) media access control method, Ethernet employs the Manchester Encoding technique.
• Various types of Ethernet networks exist for connecting devices and transferring data, including:

1. Fast Ethernet: Transfers data at a speed of approximately 100 Mbps.
2. Gigabit Ethernet: Transfers data at a speed of 1 Gbps.
3. 10 Gigabit Ethernet: Transfers data at a speed of 10 Gbps.

• To understand how Ethernet functions, let’s examine its frame format, which comprises the following seven parts:
• Below diagram shows Ethernet Frame format:

1. Preamble
2. SFD (Start Frame Delimiter)
3. DA (Destination Address)
4. SA (Source Address)
5. Length
6. Data
7. CRC (Cyclic Redundancy Check)

• Breaking down each part:

1. The frame format initiates with the Preamble and SFD, both operating at the physical layer.
2. Preamble: A 7-byte block featuring an alternating pattern of 0’s and 1’s (101010…10)which basically indicate the starting of the frame and is used for synchronization between sender and receiver.
3. SFD (Start Frame Delimiter): A 1-byte field always set to 10101011. The 1 at last is used to break the bit pattern and indicate the start of actual frame.
4. The DA, SA, and Length fall under the Data Link Layer.
5. DA (Destination Address): A 6-byte field containing the destination address.
6. SA (Source Address): A 6-byte field containing the source address, considering MAC addresses.
7. Length: A 2-byte (16-bit) field indicating the length of the entire Ethernet frame.
8. Data: The Data, also known as Payload, is where the actual data is inserted. The minimum data size is 46 bytes, resulting in a frame size from DA to CRC of 64 bytes. The maximum data that can be sent in one frame is 1500 bytes.
9. CRC (Cyclic Redundancy Check): A 4-byte field containing a 32-bit hash code of data created using the destination address, source address, length, and data fields. This checksum is used for detecting corrupted data in the entire frame. Data is considered damaged or corrupted if the calculated checksum at the destination differs from the supplied checksum value.

In this way, the Ethernet communication protocol works.

Do explore my other blogs covering the following communication protocols:

1. AMBA, APB, AHB and ASB
2. UART, I2C, and SPI

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