Ethernet Format

Ethernet Format

What is Ethernet Format??

In Computer Network, an Ethernet frame is an information connect layer convention information unit and utilisations the fundamental Ethernet physical layer transport components.Every Ethernet outline begins with an Ethernet header, which contains goal and source MAC addresses as its initial two fields.

Ethernet format

  • 1s and 0s pattern shows start of the frame
  • Ethernet uses mac addresses to identify

MAC address?? what is mac address now! let me explain that.

MAC address (Media access control)

  • one MAC address per Network interface.
    • In router has more than one Network interfaces, there are more than one MAC addresses
  • Each mac address 48 bits long and written in hexadecimal.
    • AA : BB : CC : 00 : 11 : 22
  • AA: BB: CC part is OUT(Organisationally unique identifier)
  • 00: 11: 22 part is Vendor assigned
  • ffff: ffff: ffff use for broadcast address (no one owns it) ex- DHCP
  • There are multicast addresses also. ex-0100.0ccc.cccc

Explains about Ethernet format

  • Preamble
    • Fixed pattern of 1s and 0s
    • 7bytes
  • SFD
    • 8th byte – (Start frame delimiter)
    • One byte long
    • Next to destination address
  • Destination
    • Destination address known as MAC address
  • Source
    • Source address – Sender embeds its own source address
  • Type
    • Including which Protocol is in data Section
    • which Protocol is encapsulated inside this Ethernet frame (IPv4/IPv6)
  • Data (payload)
    • Datas
  • FCS – (Frame Check Sequence)
    • This is trailer
    • This determine if any part of the frame has become corrupted, during transit.

How is FCS works???

  • When frame is 1st assembled, then Sender will run mathematical formula over the frame contents.
  • Then results will push into trailer (FCS) and save it
  • After send, when frame arrives the receiver runs the same formula over frame (without trailer)
  • If results match with contain of trailer there is no data corruption
  • If data is corrupted and it will be discarded.
  • Ethernet not Recover this data but High-level protocol like TCP will recover data.

Hope this would be helpful, If you interested in Networking should know about Ethernet format.

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