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:
“This city is neither a jungle nor the moon.... In long shot: a cosmic smudge, a conglomerate of bleeding energies. Close up, it is a fairly legible printed circuit, a transistorized labyrinth of beastly tracks, a data bank for asthmatic voice-prints.”
—Susan Sontag (b. 1933)
“John Brown and Giuseppe Garibaldi were contemporaries not solely in the matter of time; their endeavors as liberators link their names where other likeness is absent; and the peaks of their careers were reached almost simultaneously: the Harper’s Ferry Raid occurred in 1859, the raid on Sicily in the following year. Both events, however differing in character, were equally quixotic.”
—John Cournos (1881–1956)
“The writer in me can look as far as an African-American woman and stop. Often that writer looks through the African-American woman. Race is a layer of being, but not a culmination.”
—Thylias Moss, African American poet. As quoted in the Wall Street Journal (May 12, 1994)