METHOD OF OPERATING A NETWORK

Abstract

A method is proposed for operating a network with several subscribers in the network. For this purpose, the network has at least one switch (10, 11, 12), at least two terminals and at least one controller. According to the invention, the controller can now communicate with one of the terminals via an application protocol. For this purpose, data is sent and/or received as data packets. In order to be able to schedule the communication, time slots are provided for sending the data packets that are adapted to a maximum possible packet size. For this purpose, the time slots have a start time and an end time so that they can overlap in different branches of the network. To optimize communication time, the packet sizes (5) can be changed. To avoid wasting bandwidth in the network, the time slots are adapted to the packet size accordingly by changing the start times and the end times (6).

Claims

1. A method of operating a network with multiple subscribers in the network and comprising at least one switch, at least two terminals, and at least one controller, the method comprising the steps of: the controller communicating with one of the terminals via an application protocol by sending or receiving data as data packets, providing time slots having respective start and end times that are adapted to a maximum possible packet size for sending the data packets, and, when packet sizes are changed, adapting the time slots to the packet size by changing the start times and the end times.

2. The method according to claim 1, wherein the start times are adapted to a minimum possible packet size.

3. The method according to claim 1, wherein the network is an automation network.

4. The method according to claim 1, wherein sizes of the time slots are adjusted to the maximum possible packet size during an initialization of the communication via the controller.

5. The method according to claim 4, wherein the time slots overlap in time.

6. The method according to claim 1, wherein the change of packet sizes is performed during communication.

7. The method according to claim 1, wherein the change of the packet sizes and the change of the start times and the end times are independent of each other in terms of time.

8. The method according to claim 1, wherein the change in packet sizes and the change in start times and end times are controlled by a protocol that operates independently of the application protocol.

9. The method according to claim 1, wherein the subscribers are connected to the switches in ring or line topology.

10. The method according to claim 1, wherein a plurality of the terminals are connected in series.

11. The method according to claim 1, wherein communication takes place by data packets within the link layer of the network.

12. The method according to claim 1, wherein the switches are routers or servers.

13. The method according to claim 1, wherein several controllers are present as subscribers in the network.

14. The method according to claim 1, wherein a configuration of the controller or the switch is performed by a network management.

Description

[0038] Therein:

[0039] FIG. 1 is a block diagram of the previous problem of a packet size change;

[0040] FIG. 2 is a block diagram of the process according to the invention; and

[0041] FIG. 3 shows operation phases using the example of a SERCOS III network;

[0042] FIG. 1 is a schematic representation of part of a communication in a network. The data to be transmitted is divided into data packets and sent or received in the currently available bandwidth of the network.

[0043] The data packets are shown in the figure as diagonally shaded areas. As an example, the communication contains three data packets that are sent and received over different cycles of the network. The term cycle is understood according to IEEE 802.1Q (“Time-Aware Shaping”). The cycles are shown here as dotted areas and can be addressed via three switches 10, 11, 12.

[0044] Time slots are provided for the data packets that are represented by vertical hatching. At the start of communication, these time slots are set to the maximum packet size. This means that the start times of the time slots correspond to the start times of the data packets. The end times of the time slots may be later than the end times of the data packets due to the maximum-size assumption. The maximum packet size is thus determined by the amount of data and the available bandwidth. This is standardized in IEEE 802.1Qbv.

[0045] To optimize communication times, respective packet sizes of the data packets are changed to a time optimum. This shortens the data packets as shown under step 1.

[0046] The shortening of the data packets and the time slots that have remained the same length so far result in time gaps between the individual data packets. The individual time slots are designed to be contiguous, which means that the end of one time slot simultaneously represents the start of another time slot. Thus, this results in continuous communication. In the case of the reduced data packets, however, the available bandwidth is not effectively utilized.

[0047] To use the bandwidth effectively, the time slots can be shortened by matching the end times of the time slots to the end times of the data packets. This is illustrated in step 2. However, this causes gaps in the data stream during communication, which is known as the jitter effect and causes errors in the network. In the case of a SERCOS III network, this causes an error condition.

[0048] Therefore, the time slots must be offset or shifted so that a coherent data stream is created again. This is shown in step 3. To avoid the error condition, step 2 and 3 would have to be executed together (at the same time), which corresponds to step 4, but is practically not feasible, since the shifting of a time slot is also error-prone. A shift could cause a time slot to enter a time slot that has already been reserved.

[0049] FIG. 2 shows the solution to the above problem according to the invention. Here, time slots are also generated at the start of communication and are adapted to the maximum possible packet sizes. However, according to the invention, the time slots are designed in such a way that they overlap. A continuous data stream is ensured by the different start times of the data packets within the time slots. Thus, the start times of the time slots are no longer identical to the start times of the data packets.

[0050] If the data packets are now reduced in size, the overlap of the time slots can still ensure a continuous data stream without an error condition occurring. This is shown in step 5.

[0051] The communication would now still work without errors, but would not be effective due to the length of the time slots.

[0052] Accordingly, it is proposed to adapt the time slots to the reduced data packets, such that not only the end times of the time slots are adapted to the data packets, but also the start times. This is shown in step 6.

[0053] This procedure enables optimization of the size of the data packets without having to shift the time slots. Also, the adaptation of the time slots to the data packets is decoupled from the reduction of the data packets, so that a possible source of error is eliminated.

[0054] In FIG. 3, the procedure is explained on the basis of SERCOS III operation phases. First, communication is initialized by means of SERCOS III (NRT) and then, toward M, the topology of the network is defined according to the application protocol (CP0).

[0055] Then, in direction S, the configuration is loaded and executed (CP1). In the next step in direction S, the data packet size is defined and optimized during communication (CP2). The terminals that act as communication receivers, are jitter-sensitive from this point on.

[0056] CP3 comprises the actual communication with optimized packet sizes. CP4 terminates the communication and enables the next communication that works according to the same principle.

[0057] Accordingly, the process according to the invention is executed within the marked area. Accordingly, the initial packet size and time slot size are s determined from CP2 and optimized between CP2 and CP3 (see steps 5 and 6 from FIG. 2).

[0058] The present application is not limited to the previous features. Rather, further embodiments are conceivable. For example, instead of at least one switch, a router or a server could also be used. Also, further subscribers, such as PCs or hubs, could be used.