Computer Networks and distributed Systems

as part of the BMBF-Compound Project SIMBA — „Key Concepts of Informatics in multi medial Elements under special Consideration of Women's specific Learning Interests”

Advice for Teachers - Error Detection

On transmitting frames within networks errors may occur. Therefore, in order to be able to work smoothly, methods for error detection and -correction are necessary.

In the interactive applications below three methods for error detection are introduced.
CRC (Cyclic Redundancy Check) is a technique used frequently for the detection of transmission errors.
One-dimensional parity and two-dimensional parity are simpler, yet, equally wide spread methods. Within the scope of the latter data is transmitted as a block of n lines and q columns, in which every line and every column is added a parity bit. (see Illustration 3)

Illustration 1: CRC

Illustration 2: One-dimensional parity

Illustration 3: Two-dimensional parity

Average learners have a hard time understanding the mode of operation, which, especially in the case of CRC, is rather complex. This application makes it possible to calculate solutions independently for automatically generated exercises, afterwards having them corrected automatically. Calculating and using the algorithms independently is a pivotal step towards comprehension. Here, especially proof-calculating the given algorithms by hand is an error-prone as well as time-consuming activity. It takes away from other activities, that are important for the learning process.
Therefore, this object is well-suited to prepare for exams, as in such phases time as well as working energy may be concentrated on the basics.

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