Network_OSI Layer 2

Layer 2

- It is responsible for managing data flow and error control

  between communication devices within the same LAN network.

 

- When communicating with networks in different LAN segments,

  Layer 3 is required.

 

MAC address(6bytes) used in Layer 2

- It is a physical address with a unique value (in hexadecimal).

 

- The first 6 digits represent the OUI (Organizationally Unique Identifier),

   which is the unique ID of the company

   that assigned the MAC address to the network device.

 

- The last 6 digits are a unique number assigned to the device

   by the manufacturer.

 

- The MAC address cannot be changed unless special equipment is used.

 

 

Layer 2 Ethernet Protocol

- Destination Address (6 bytes): Refers to the destination MAC address (6 bytes).

 

- Source Address (6 bytes): Refers to the source MAC address (6 bytes).

 

- Data (2 bytes): Refers to the payload.

 

- Ethernet Type (2 bytes): Identifies the type of Layer 3 protocol

  at the beginning of the payload.  

  There are two Layer 3 protocols that appear before the DATA

  [0800: IPv4 and 0806: ARP]

 

- This Ethernet Type field allows for the quick identification of the

  upper-layer protocol contained in the DATA,

  improving the efficiency of data transmission.