notes/School/Analyse/Layers/2. Datalink Layer.md

2. Data link Layer

The Data Link Layer is responsible for handling the data transfer between two devices on the same network. (so a bit like the Network Layer)

The Data Link Layer also splits up packets into smaller chunks called a frame. The reverse happens on the receiving device (reassembling frames into packets).

Like the Network Layer the Data Link Layer is also responsible for flow control and error checking.

Error detection

Transmissions are not always error free. In case of an error, it should be detected and the message should be re transmitted (whenever possible)

Detecting errors are handled by different algorithms:

• Parity bits
• CRC

Data Framing

Data is split up in smaller chunks called frames. For each frame we add some extra data:

• Who is sender?
• Who is receiver?
• Length of chunk
• Type of chunk (normal message, error me)
• Error checking values (ex. CRC code)
• Data and metadata are put in single message called frame