Black Channel
In communication technology, a black channel is a communication channel with unsecured properties or properties that do not match the application. It is the characteristic element of the black channel principle , a design pattern with the help of which the application's requirements for communication can be met without the communication channel ensuring this. It is z. B. used in safety-related systems in which communication components are used that do not meet the requirements of the application.
When designing safety-related systems , compliance with relevant standards such as IEC 61508 must be demonstrated. If communication methods - such as Ethernet - are used in such systems for which this proof is not possible, the “black channel” principle can be used as a substitute. For this purpose, a security protocol is usually integrated between the security application and the "non-secure" standard communication channel, which corresponds to the security level of the security-oriented system and recognizes and controls transmission errors in the communication layers below. This means that the "non-secure" transmission channel is continuously monitored for its integrity by a higher-level "secure" protocol.
Examples of transmission errors at the protocol packet level in the "unsafe" channel are:
- Repetition
- loss
- insertion
- Wrong order
- Adulteration
- delay
- Mixing of safe and non-safe telegrams
If the security protocol detects such an error, an error response is initiated. In the best case, the transmission error can still be controlled and thus tolerated, otherwise the system must be transferred to a safe state , which, however, often leads to a standstill and thus to a loss of productivity of the system.
Safety- related fieldbus protocols are specified in the standards IEC 61158 (basic communication), IEC 61784-2 (real-time communication) and IEC 61784-3-18 (safety profile).
References and comments
- ^ Black Channel Constraints. Retrieved January 3, 2018 .
- Jump up ↑ Verhappen, Ian .: The Hidden Network. In: ControlGlobal.com. February 14, 2011, accessed on January 3, 2018 (Verhappen notes the increasing use of the term in technical terms, problematizes the lack of a precise definition for it and goes into more detail on the concrete implementation of the black channel transmission of safety data.).