Nowadays, many embedded systems use specific data buses to ensure the exchange of data. To reduce the financial cost, the mass and to increase performance in keeping at least the same reliability, a solution is to rely on a components off-the-shelf (COTS) technology. As switched Ethernet is a well-known solution and widely implemented, this technology is studied for the next generation of space launchers. In this paper, we focus on the observability issue defined as, not simply network management system techniques, but as the ability to monitor the satisfaction of the application quality of performance (especially in terms of time constraints and frames sequence). It consists to obtain a real picture of the communications at any given time and location. In a conventional communication technology (i.e., specific buses), it is easy to collect all exchanges on the physical wire with a dedicated device. But, it is not possible anymore on a switched network. Many monitors are therefore implemented and have to be synchronized. Hence, this paper aims at highlighting the implementation challenges that we have faced in our experimental test bench mainly in coping with online synchronization. Some recommendations on synchronisation and multi-monitoring issues are therefore submitted for the future developments.