Logical link control

However, most protocol stacks running atop 802.2 do not use LLC sublayer flow control and error management.

These higher layer protocols work in an end-to-end fashion, i.e. re-transmission is done from the original source to the final destination, rather than on individual physical segments.

An LLC sublayer was a key component in early packet switching networks such as X.25 networks with the LAPB data link layer protocol, where flow control and error management were carried out in a node-to-node fashion, meaning that if an error was detected in a frame, the frame was retransmitted from one switch to next instead.

Since bit errors are very rare in wired networks, Ethernet does not provide flow control or automatic repeat request (ARQ), meaning that incorrect packets are detected but only cancelled, not retransmitted (except in case of collisions detected by the CSMA/CD MAC layer protocol).

Another example of a data link layer which is split between LLC (for flow and error control) and MAC (for multiple access) is the ITU-T G.hn standard, which provides high-speed local area networking over existing home wiring (power lines, phone lines and coaxial cables).