Data-Link Framing

Point-to-point dedicated DS0 and higher PSTN-based communications links require a data-link protocol to format ULP data for transmission. The data-link protocol is responsible for the encapsulation of ULP data into transmission frames, as well as their transmission and delivery over the synchronous or asynchronous transport link.

For serial data transmissions using Universal Synchronous Asynchronous Receiver/Transmitter (USART) and Universal Asynchronous Receiver/Transmitter (UART) based transmission devices, there are two commonly used data-link framing protocols: the ISO's HDLC and the open standard, PPP. Both are derivatives of IBM's Synchronous Data-Link Control (SDLC), which was developed in the 1970s to provide serial ...

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