CHARACTER ORIENTED PROTOCOL:
The character-oriented protocol is of an 8-bit size frame, the header which covers the source and destination address and some other control information, whereas the trailer carries error detection or error correction redundancy bits. In order to separate one frame from the next frame, the designer added a flag bit at the beginning and end of the frame. The most popular protocol which used to exchange only text by the data link layer.
If the receiver encounters other information rather than text in the middle of the data the user thinks of the end of the problem. To overcome this problem a byte-stuffing strategy was added to character-oriented framing. If the same pattern of the data found in the frame a special byte is added to the data section is called character stuffing (byte stuffing). This is called an escape character (ESC), which has a predetermined bit pattern. If we add ESC character in the middle of the data section means it treated has the next character as data, not a delimiting flag.
But it again creates a problem if the data contain an Escape character followed by a flag, by this the receiver will remove the ESC character from the data section but keeps the flag, which is incorrectly interpreted because of the end of the frame. To over the encountered problem, if the escape character is part of the text, an extra ESC character added to show that the second one is the part of the text.
BIT ORIENTED PROTOCOL:
Bit stuffing is the process of adding one extra 0 whenever five consecutive is follow a 0 in the data so that the receiver does not mistake the pattern 0111110 for a flag. In this, the data section of a frame is a sequence of bits to be interpreted by the upper layer as text, audio, video, and audio, etc. Where in addition to the header, the designer will require a delimiter to separate one frame from other frames. Well, most protocols use a special 8-bit pattern flag as the delimiter to determine the starting and end of the frame.
