What is the difference between PROFINET A and B?

1, Functional differences
PROFINET A (CC-A) is the most basic level in the PROFINET protocol, providing basic functionality for PROFINET IO and RT (real-time) communication. These features include cyclic exchange of I/O data with real-time properties (1 to 512 milliseconds), non cyclic data communication (for reading and writing demand oriented data such as parameters and diagnostic information), parallel TCP/IP communication, flexible alarm models (for signal equipment and network errors, with three alarm levels), etc. In addition, PROFINET A also supports addressing schemes based on modules, slots, and sub slots, as well as GSD files for integration into engineering systems.
In contrast, PROFINET B (CC-B) has been extended on the basis of A, adding additional network diagnosis and topology detection functions. This is mainly achieved through the Simple Network Management Protocol (SNMP), which integrates parts of the Management Information Base 2 (MIB2) and the Lower Link Discovery Protocol MIB (LLDP-NEXT MIB) into the device. In addition, PROFINET B also supports querying all diagnostic and topology information from physical device objects (PDEVs) through non periodic PROFINET services. These features make PROFINET B more advantageous in network diagnosis and troubleshooting.
2, Application scenarios
PROFINET A is suitable for all (sub) applications that do not rely on network topology and functionality, such as network diagnostics and topology detection. These applications include locally separated I/O stations and (sub) networks connected through wireless technology, as well as situations where various automation fields are connected using company networks. Due to its comprehensive basic functions and relatively low cost, PROFINET A has been widely used in many simple industrial automation systems.
PROFINET B is more suitable for complex industrial automation systems that require network diagnosis and topology detection functions. These systems typically include multiple devices, complex network topologies, and high reliability requirements. Through the additional features provided by PROFINET B, system administrators can more conveniently perform network monitoring, troubleshooting, and performance optimization.
3, Network topology
In terms of network topology, both PROFINET A and B support multiple topology structures, such as star, tree, and bus. However, due to the addition of network diagnosis and topology detection functions, PROFINET B has an advantage in handling complex network topology structures. This is mainly reflected in PROFINET B's ability to better identify devices, connection relationships, and communication paths in the network, thereby more accurately diagnosing and solving network problems.
4, System redundancy
System redundancy is one of the important functions in industrial automation systems, which can improve the reliability and stability of the system. In the PROFINET protocol, system redundancy functionality is included in an extended version of CC-B called CC-B (PA). This means that although PROFINET A itself does not support system redundancy functionality, it can be achieved by upgrading to PROFINET B (PA).
PROFINET B (PA) provides a cross vendor application solution with redundant controllers to achieve higher availability. This is particularly important for equipment in the process industry, as these devices typically require continuous operation and have a low tolerance for faults. By adopting PROFINET B (PA), enterprises can build more reliable and stable industrial automation systems.