Search results
Results from the WOW.Com Content Network
To understand the advantages, start with the slice-by-2 case. We wish to compute a CRC two bytes (16 bits) at a time, but the standard table-based approach would require an inconveniently large 65536-entry table. As mentioned in § Generating the lookup table, CRC tables have the property that table[i xor j] = table[i] xor table[j].
The CRC and associated polynomial typically have a name of the form CRC-n-XXX as in the table below. The simplest error-detection system, the parity bit , is in fact a 1-bit CRC: it uses the generator polynomial x + 1 (two terms), [ 5 ] and has the name CRC-1.
These inversions are extremely common but not universally performed, even in the case of the CRC-32 or CRC-16-CCITT polynomials. They are almost always included when sending variable-length messages, but often omitted when communicating fixed-length messages, as the problem of added zero bits is less likely to arise.
CRC: Cyclic redundancy check Link and other layers 24 References here. CRC-16-CCITT: Cyclic redundancy check (X.25, HDLC) Link layers Reference on CRC page. CRT: Cathode Ray Tube Television set, Computer Monitor Cathode ray tube: CSMA/CA: Carrier sense multiple access / collision avoidance Wireless IEEE Std 802.11 Downloads: CSMA/CD
CRC Handbook of Chemistry and Physics, a science reference handbook published by CRC Press CRC Standard Mathematical Tables , a mathematics reference handbook published by CRC Press Cyclic redundancy check , a type of hash function used to produce a checksum in order to detect errors in data storage or transmission
There are two fundamental limitations on when it is possible to construct a lookup table for a required operation. One is the amount of memory that is available: one cannot construct a lookup table larger than the space available for the table, although it is possible to construct disk-based lookup tables at the expense of lookup time.
The frame check sequence (FCS) is a 16-bit CRC-CCITT or a 32-bit CRC-32 computed over the Address, Control, and Information fields. It provides a means by which the receiver can detect errors that may have been induced during the transmission of the frame, such as lost bits, flipped bits, and extraneous bits.
Fletcher addresses both of these weaknesses by computing a second value along with the simple checksum. This is the modular sum of the values taken by the simple checksum as each block of the data word is added to it.