  Ultra-reliable and low-latency communication has received significant
research attention. A key part of this evolution are the Time-Sensitive
Networking (TSN) standards, which extend Ethernet with real-time mechanisms. To
guarantee high reliability, the standard IEEE 802.1CB-2017 Frame Replication
and Elimination for Reliability enables redundant communication over disjoint
paths. While this mechanism is essential for time-critical applications, the
standard contains some fundamental limitations that can compromise safety.
Although some of these limitations have been addressed, none of the previous
works provide solutions to these problems. This paper presents solutions to
four main limitations of the IEEE 802.1CB-2017 standard. These are 1) choosing
match versus vector recovery algorithm, 2) defining the length of the sequence
history, 3) setting a timer to reset the sequence history, and 4) dimensioning
the burst size in case of link failures. We show how these challenges can be
solved by using best- and worst-case path delays of the network. We have
performed simulations to illustrate the impact of the limitations and prove the
correctness of our solutions. Thereby, we demonstrate how our solutions can
improve reliability in TSN networks and propose these methods as guidance for
users of the IEEE 802.1CB standard.
