Unit 2 Data Link Layer - Functions and its Prototocols
UNIT: Data Link Layer Fig – 7 layers of OSI Model 1. Introduction to Data Link Layer Definition: The Data Link Layer (DLL) is the second layer in the OSI model. It provides node-to-node delivery of frames and ensures reliable data transfer over the physical link. Functions: Framing - Divides the stream of bits received into data units called frames. Physical addressing (MAC) - If frames are to be distributed to different systems on the same network, data link layer adds a header to the frame to define the sender and receiver. Error detection & correction - Used for detecting and retransmitting damaged or lost frames and to prevent duplication of frames. This is achieved through a trailer added at the end of the frame. Flow control - If the rate at which the data are absorbed by the receiver is less than the rate produced in the sender ,the Data link layer imposes a flow ...