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Ethernet Frame Header

 

Here's an example of a packet frame and its header for data transmission. A typical frame header contains several fields, depending on the protocol and network type (like Ethernet). Below is a simplified Ethernet frame structure.

Ethernet Frame Header Breakdown:

  1. Destination MAC Address (6 bytes):

    • The hardware address of the recipient (e.g., the next router or the destination device).

  2. Source MAC Address (6 bytes):

    • The hardware address of the sender (e.g., your computer or router).

  3. Type/Length (2 bytes):

    • Type: Indicates the type of the protocol being used (for example, IP, ARP).
    • Length: If using Ethernet II, this field indicates the length of the payload.

  4. Payload (Data) (46-1500 bytes):

    • The actual data being transmitted (e.g., your "Hello" message or IP packet). This is what gets encapsulated in the frame.
    • This can vary in size, depending on the network and protocol used.

  5. Frame Check Sequence (FCS) (4 bytes):

    • A checksum used for error checking (used for detecting errors in the frame).

Ethernet Frame Example:

Destination MAC (6 bytes) Source MAC (6 bytes) Type (2 bytes) Data (46–1500 bytes) FCS (4 bytes)
00:14:22:01:23:45 00:14:22:67:89:ab 0x0800 (IP) "Hello" message FCS value

Explanation:

  • Destination MAC: The MAC address of the receiver's network interface.
  • Source MAC: The MAC address of the sender's network interface.
  • Type: Specifies the protocol (e.g., IP).
  • Payload/Data: The actual data being sent (e.g., the "Hello" message).
  • FCS: Ensures that no errors occurred during transmission.

Simplified Frame Packet for WhatsApp Example:

  1. Your device (sender) creates a packet with:
    • Destination MAC: The MAC address of your router.
    • Source MAC: Your device's MAC address.
    • Type: IPv4 or ARP.
    • Data: The message ("Hello").
    • FCS: Checksum to check for errors.
  2. Router forwards the frame using its own MAC address and ensures the correct path is used.

This is a basic overview of how a Data Link Layer frame would look when transmitting data in a network.

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