Error Checking

Error Checking

1. A PROTOCOL is a set of rules that governs how information is communicated.

   • When data is transmitted over a network, it can be corrupted and some of the data can be lost

2. PARITY: using 7-bits of data in each byte. A 0 is added to the end if it is posative and a 1 is added to the end if it is negative

   • When you receive the byte, you have to check if there is an even number of ones or zero's
   • If not then there is a parity error and something has been corrupted.
   • The type of parity used is agreed in advance according to a protocol.

3. ECHOES: a way of checking small amount of data for errors.

   • Data is returned to the sender and the sender confirms it matches what it sent.
   • LIMITATION: slow and inefficient as data is being sent twice.

4. CHECKSUMS: data is sent in several blocks of bits and added together.

   • The total from the sums is attached to the file being transmitted across the network
   • When the data arrives, the receiver independently completes its won checksum
   • If the 2 checksums match up, the data is accepted.