Data Link Layer and Higher
Asynchronous communication at the data link layer or higher protocol layers is known as statistical multiplexing or packet mode communication, for example asynchronous transfer mode (ATM). In this case the asynchronously transferred blocks are called data packets, for example ATM cells. The opposite is circuit switched communication, which provides constant bit rate, for example ISDN and SONET/SDH.
The packets may be encapsulated in a data frame, with a frame synchronization bit sequence indicating the start of the frame, and sometimes also a bit synchronization bit sequence, typically 01010101, for identification of the bit transition times. Note that at the physical layer, this is considered as synchronous serial communication. Examples of packet mode data link protocols that can be/are transferred using synchronous serial communication are the HDLC, Ethernet, PPP and USB protocols.
Read more about this topic: Asynchronous Communication
Famous quotes containing the words data, link, layer and/or higher:
“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)
“This world is run by people who know how to do things. They know how things work. They are equipped. Up there, there’s a layer of people who run everything. But we—we’re just peasants. We don’t understand what’s going on, and we can’t do anything.”
—Doris Lessing (b. 1919)
“There is one thing higher than Royalty: and that is religion, which causes us to leave the world, and seek God.”
—Elizabeth I (1533–1603)