One of the use cases for PubSub is the cyclic exchange of real-time data. In such a use case, the layout of the data that needs to be transferred is the same in every PublishingInterval. When the message layout is the same in every PublishingInterval, and the Subscriber knows this in advance, several optimizations are possible:

• Both Publisher and the Subscriber can be optimized for sending and receiving messages with a fixed layout, therefore offsets of send/receive fields can be pre-calculated based on the configuration.
• Certain encodings may result in varying size of DataSetMessages, which requires extra fields in the messages to allow the Subscriber to parse these messages. These extra fields can be omitted when the size of the DataSetMessages is constant.

The header layout described in this section is optimized for this use case.