Header Error Correction

From Wikipedia, the free encyclopedia

The Header Error Correction (HEC) is the last field in the Asynchronous Transfer Mode cell consisting of an 8-bit CRC of the cell's header only.

It consists of the remainder of the division of the 32 bits of the header by the polynomial x8 + x2 + x + 1. The pattern 01010101 is XORed with the 8-bit remainder before being inserted in the last octet of the header[1]. This added 01010101 value is called a coset.

This scheme is able to correct single-bit errors and detect many multiple-bit errors.

For a tutorial and an example of computing the CRC see the Mathematics of CRCs page.

[edit] References

  1. ^ ATM User-Network Interface Specification V3.0. Retrieved on 2007-09-17.