📖 IT Bible

Ethernet and MAC Addresses

Ethernet - protocol most widely used to send data across individual links

  • Ethernet and data ink layer provide a means for software at higher levels of the stack to send and receive data
  • Ethernet as a protocol solved collision domains by using a technique known as carrier sense multiple access with collision detection (CSMA/CD)

CSMA/CD - used to determine when the communications channels are clear, and when a device is free to transmit data

  • if there’s no data being transmitted on the network segment, a node will feel free to send data
  • if 2 or more computers end up trying to send data at the same time, the computers detect this collision and stop sending data
  • Each device involved with the collision then waits a random interval of time before trying to send data again, and that random interval prevents devices from colliding again

MAC Address (Media Access Control address) - globally unique identifier attached to an individual network interface; a 48-bit number normally represented by 6 groupings of 2 hexadecimal numbers

  • Hexadecimal - a way to represent numbers using 16 digits Pasted image 20260521175349
  • Octet - in computer networking, any number that can be represented by 8 bits

MAC Address is spit into 2 sections:

  1. Organizationally Unique Identifier (OUI) - the first 3 octets of a MAC address
  2. Last 3 octets can be assigned in any way that the manufacturer would like

*Ethernet uses MAC address to ensure that the data it sends has both an address for the machine that sent the transmission, as well as the one the transmission was intended for