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)
“Anthropologists are a connecting link between poets and scientists; though their field-work among primitive peoples has often made them forget the language of science.”
—Robert Graves (1895–1985)
“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)
“Labor is prior to, and independent of, capital. Capital is only the fruit of labor, and could never have existed if labor had not first existed. Labor is the superior of capital, and deserves much the higher consideration.”
—Abraham Lincoln (1809–1865)