Linux in combination with PREEMPT_RT is a popular operating system for embedded devices in real time environments and Time Sensitive Networks (TSN). Linux Real time networking applications range from industrial fieldbuses like PROFINET and Ethercat, Audio and Video Bridging (AVB) up to Automotive. Over the last years several networking technologies such TSN Qdiscs, XDP, zero-copy and busy polling have been added into the Linux kernel or improved for real time use cases. In this contribution we will show concepts and tools like the RTC-Testbench, evaluate what precision and performance as well as limitations and pitfalls can be expected when deploying Linux as operating system for these devices.