How Data is Placed in Frames, continued

To overcome synchronization problems, special byte sequences are often used to prefix and suffix (envelope) the data.

As these special bytes may themselves be required data we must "escape" their special meaning (particularly true for "binary" data such as floating point numbers, executables, JPGs and MP3s).

This process is termed byte stuffing, using DLE=020₈, STX=002₈, ETX=003₈.
On a Linux or macOS machine, execute: man ascii.

Consider the following example, transmitting 3 bytes: [A, DLE, B]

A lower-level approach, bit-stuffing, overcomes the reliance on using the ASCII codes. Each frame is now enveloped in pairs of "flag" patterns 01111110.

If this flag pattern appears in the data, the stuffed sequence 011111010 is transmitted.