How Data Stuffing Useful in Transmission + Byte Stuffing


Why soh is replaced with esc x
If the receiver can receive two times soh and get confused then it can receive two times esc x similarly.

To prevent data being interpreted as control information data stuffing is used.

It may easily happen that the control information (SOT, EOT) pattern occurs in the data. This is called interface with framing. A way to solve problem "Special escape byte insertion just before each 'accidental' control information (SOT, EOT) in data. While receiving the data , it removes escape byte before the data given to network layer and is called character stuffing or byte stuffing. Thus, framing delimiters can be distinguished from one in the data by the absence or presence of an escape byte before it.

Now what happens if an escape byte occurs in the middle of the data?Answer to it, too, is stuffed with an escape byte. Thus, any single escape byte is part of an escape sequence, whereas in the data a doubled one shows that single escape occurred naturally. All cases are same as original byte sequence. After De-stuffing byte sequence will deliver.

Byte Stuffing

Byte stuffing is a process that transforms a sequence of data bytes that may contain 'illegal' or 'reserved' values into a potentially longer sequence that contains no occurrences of those values. The extra length is referred to in this paper as the overhead of the algorithm.

To date, byte stuffing algorithms, such as those used by SLIP [RFC1055], PPP [RFC1662] and AX.25 [ARRL84], have been designed to incur low average overhead but have made little effort to minimize worst case overhead.

Some increasingly popular network devices, however, care more about the worst case. For example, the transmission time for ISM-band packet radio transmitters is strictly limited by FCC regulation. To adhere to this regulation, the practice is to set the maximum packet size artificially low so that no packet, even after worst case overhead, can exceed the transmission time limit.

This paper presents a new byte stuffing algorithm, called Consistent Overhead Byte Stuffing (COBS), that tightly bounds the worst case overhead. It guarantees in the worst case to add no more than one byte in 254 to any packet. Furthermore, the algorithm is computationally cheap, and its average overhead is very competitive with that of existing algorithms.

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