TSN (Time Sensitive Network) Software Stack - the last mile

The last 20% in solving a technical challenge is always the most difficult.

TSN is well known as the future technical base for real-time, deterministic, resilient and congestion-free Ethernet. The basic network technology is well defined and fulfills all those requirements. Nevertheless, within the “last mile” of the communication path (the piece of software between the Ethernet controller hardware and the application software) things can breakdown and achieving the promise of TSN can be lost. Even the Ethernet drivers and network stacks of most real-time operating systems are NOT deterministic.This is a deal-breaker for what is expected when utilizing TSN. To enjoy the features of TSN in applications, specialized software solutions are required:

The acontis TSN Software Stack

For real-time capable devices to be connected to a TSN network, the entire real-time path must be entirely deterministic for both sending and receiving data. This real-time path starts in the application running on the device’s real-time operating system (RTOS), extends down through the TSN stack, and finally to the Ethernet device driver and the Ethernet hardware. Additionally, regular (or non-TSN) as well as other non-deterministic TCP/IP Ethernet communications must exist on the same Ethernet controller and through the TCP/IP stack of the RTOS in such a way as to not disturb the real-time TSN traffic.

High precision clock synchronization according to 802.1AS-REV is another key part of the TSN stack. The Ethernet drivers included in the acontis TSN software stack are specifically optimized to guarantee the processing of high priority, time scheduled data as well as low priority best effort data (e.g. regular TCP/IP traffic). The acontis TSN software stack’s high performance and deterministic Ethernet drivers are based on the long-established and field proven combination of RTOS, processor, and Ethernet MAC controllers used in the industry leading acontis EtherCAT master stack.

The acontis TSN software stack provides a convenient user-friendly API for transmitting data from other protocols like OPC UA, PROFINET, and EtherCAT via the TSN network. Furthermore, the acontis TSN software stack includes a special RTOS-specific network driver to facilitate the use of the same Ethernet interface for regular TCP/IP traffic in a way as to not disturb the parallel transmission of real-time protocols to be carried over TSN. A typical RTOS networking stack provides a standard socket interface, and the acontis TSN software stack enhances this with a real-time capable UDP channel. As a result, existing UDP based protocols can be easily enhanced to utilize the deterministic data transfer over a TSN network.