The second layer in OSI model is the Data Link, a very important layer in ensuring Network connectivity and data delivery. Main functions of Data Link Layer are:
- Define Network Protocol (Ex. Ethernet, Token Ring etc)
- Ensure Data is delivered to the correct device across Network
Data Link Layer has two sub layers in them
Logical Link Control:
- Provides interface for MAC sublayer by utilizing Source Service Access Points and Destination Service Access Points
- Manages the Control, Sequence and Acknowledgement of frames
- Manages Flow Control
Media Access Control:
- Frames the data packets
- Manages Error Control
- Identifies the MAC access (Media Access Control Address), a unique 48 bit address that identifies the Network device (mostly embedded into the Network Interface Card).
- Handles accessing the Media (Token Ring, CSMA/CD used in Ethernet, Polling used in Mainframe, etc)
The MAC address of your windows PC, for example, can be obtained by using ipconfig /all command. See an example output below:
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