| 摘要 |
When using PROFINET IRT in a system, the transmission of process data is determined ahead of time in an extremely precise manner for the entire network according to a precisely determined sequence using an engineering tool. The maximally allowed deviation from the beginning of a bus cycle is 1 µs, thereby resulting in no queues during communication. The preplanning in the IRT component and the monitoring process carried out by the IRT hardware excludes the possibility of the NRT protocol interfering with the IRT communication component. The PROFINET standard requires that all participants do not transmit more than 3 Kbyte/ms. Such a requirement does not exist in IEEE 802.3, however. More often, there are multiple extensions which oppose said requirement, thereby leading to RT frames now being discarded due to overflowing queues in the network elements because the network component is blocked by NRT communication jumbo frames that are being transmitted at the moment for example. Thus, the RT communication can no longer be maintained such that as a result, the subordinate automation task can no longer be carried out in an error-free manner. In order to diagnose the problem, the network is flooded with packets of the lowest priority so that the network is being utilized at virtually 100% capacity. Said packets "know" their path and allow a determination to be made as to which and how many data packets have been lost. By further analyzing the missing diagnosis data packets, a detection of the network components in which the packet loss has occurred can be carried out. |
