What are the advantages of a CRC over the Internet checksum algorithm?What are the disadvantages? Solution Checksum: all 16-bit words are summed together using one\'s complement (with the checksum field set to zero). The sum is then one\'s complemented. This final value is then inserted as the checksum field. CRC: the remainder of a binary division with no bit carry (XOR used instead of subtraction), of the message bit stream, by a predefined (short) bit stream of length n + 1, which represents the coefficients of a polynomial with degree n. Before the division, n zeros are appended to the message stream. Finally: The TCP checksum is a quite weak check by modern standards. Data Link Layers with a high probability of bit error rates may require additional link error correction/detection capabilities. If TCP were to be redesigned today, it would most probably have a 32-bit cyclic redundancy check specified as an error check instead of the current checksum. The weak checksum is partially compensated for by the common use of a CRC or better integrity check at layer 2, below both TCP and IP, such as is used in PPP or the Ethernet frame. However, this does not mean that the 16-bit TCP checksum is redundant: remarkably, surveys of Internet traffic have shown that software and hardware errors that introduce errors in packets between CRC-protected hops are common, and that the end-to-end 16-bit TCP checksum catches most of these simple errors. This is the end-to-end principle at work. CRC is more thorough as opposed to Checksum in checking for errors and reporting. – Checksum is the older of the two programs. – CRC has a more complex computation as opposed to checksum. – Checksum mainly detects single-bit changes in data while CRC can check and detect double- digit errors. – CRC can detect more errors than checksum due to its more complex function. – A checksum is mainly employed in data validation when implementing software. – A CRC is mainly used for data evaluation in analogue data transmission. Disadvantages:.

1. What are the advantages of a CRC over the Internet checksum algorithm?What are the
disadvantages?
Solution
Checksum: all 16-bit words are summed together using one's complement (with the checksum
field set to zero). The sum is then one's complemented. This final value is then inserted as the
checksum field.
CRC: the remainder of a binary division with no bit carry (XOR used instead of subtraction), of
the message bit stream, by a predefined (short) bit stream of length n + 1, which represents the
coefficients of a polynomial with degree n. Before the division, n zeros are appended to the
message stream.
Finally:
The TCP checksum is a quite weak check by modern standards. Data Link Layers with a high
probability of bit error rates may require additional link error correction/detection capabilities. If
TCP were to be redesigned today, it would most probably have a 32-bit cyclic redundancy check
specified as an error check instead of the current checksum. The weak checksum is partially
compensated for by the common use of a CRC or better integrity check at layer 2, below both
TCP and IP, such as is used in PPP or the Ethernet frame. However, this does not mean that the
16-bit TCP checksum is redundant: remarkably, surveys of Internet traffic have shown that
software and hardware errors that introduce errors in packets between CRC-protected hops are
common, and that the end-to-end 16-bit TCP checksum catches most of these simple errors. This
is the end-to-end principle at work.
CRC is more thorough as opposed to Checksum in checking for errors and reporting.
– Checksum is the older of the two programs.
– CRC has a more complex computation as opposed to checksum.
– Checksum mainly detects single-bit changes in data while CRC can check and detect double-
digit errors.
– CRC can detect more errors than checksum due to its more complex function.
– A checksum is mainly employed in data validation when implementing software.
– A CRC is mainly used for data evaluation in analogue data transmission.
Disadvantages: