Data Link Layer
The standard Ethernet Data Link Layer is extended by an additional bus scheduling mechanism which secures that at a time only one node is accessing the network. The schedule is divided into an isochronous phase and an asynchronous phase. During the isochronous phase, time-critical data is transferred, while the asynchronous phase provides bandwidth for the transmission of non time-critical data. The Managing Node (MN) grants access to the physical medium via dedicated poll request messages. As a result, only one single node (CN) has access to the network at a time, which avoids collisions, present on older Ethernet hubs before switches. The CSMA/CD mechanism of non-switched Ethernet, which caused non-deterministic Ethernet behaviour, is avoided by the Ethernet Powerlink scheduling mechanism.
Read more about this topic: Ethernet Powerlink
Famous quotes containing the words data, link and/or layer:
“To write it, it took three months; to conceive it three minutes; to collect the data in it—all my life.”
—F. Scott Fitzgerald (1896–1940)
“If parents award freedom regardless of whether their children have demonstrated an ability to handle it, children never learn to see a clear link between responsible behavior and adult privileges.”
—Melinda M. Marshall (20th century)
“A revolution is not the overturning of a cart, a reshuffling in the cards of state. It is a process, a swelling, a new growth in the race. If it is real, not simply a trauma, it is another ring in the tree of history, layer upon layer of invisible tissue composing the evidence of a circle.”
—Kate Millett (b. 1934)