## 7 Results
### Number of Bridges  
The size of the network is expected to impact the reliability of streams, as in a larger path there are more chances for a frame to be affected by a fault. Figure 15 shows the reliability achievable by TSN, approach A and approach B in networks of different sizes and a BER of \(1\times 10^{-10}\).  
As expected, we can see that the reliability decreases as the network size increases. If we look at Figure 15a we see that the impact is higher in TSN than in approaches A and B, as TSN does not count with time redundancy. In any case, we can see that the reliability drops around 15% for TSN when moving from 2 to 10 bridges. If we compare this results to the ones obtained previously, we can conclude that in TSN networks with low BERs the impact of the network size is lower than the impact of other parameters.  
If we now focus on Figure 15b we see that the reliability using approach B is lower than using approach A. We also see that the difference in terms of this negative impact between both approaches increases with the number of bridges. To understand this effect please recall that the bridges of approach B are PTRF-enabled devices and, thus, they have a higher failure rate than the bridges of approach A. Additionally, recall that this does result in approach A being more reliable than approach B when the BER is low. In this sense, what we observe in Figure 15b indicates that, when the BER is low, the negative impact of using PTRF-enabled bridges instead of TSN ones increases with the size of the path, as a  
Figure 14: Reliability achievable when varying the number of replicas in a network with a BER of \(1\times 10^{-6}\). Approach A is represented in orange and approach B in green. The \(x\) axis represents the number of replicas, while the \(y\) axis represents the reliability.  
larger path includes more bridges. In any case, we must note that the reliability achievable by PTRF is above the 99.99%, and higher than in TSN, when the BER is \(1\times 10^{-10}\).  
Finally, Figure 16 shows the reliability achievable by approach A and approach B in networks of different sizes with a BER of \(1\times 10^{-6}\). We must note that we do not plot the reliability of TSN in this scenario as it is too low to be depicted together with approach A and B (under \(5.8\times 10^{-12}\)). Again, we can see that the reliability is affected by the size of the network. Furthermore, we see that the higher the BER is, the higher the impact will be.  
However, conversely to what we observe in Figure 15b, we see that approach B is a more adequate solution than approach A in networks with higher BER values. In fact, the difference of reliability of approach B when compared to approach A increases with the size of the path. This does not only reinforce the result we showed before about the higher reliability of B when compared to A when the BER is high, but it also shows that, when the BER is high, the positive impact of the additional degree of time redundancy provided by PTRF-enabled bridges further counterbalances the negative impact of their higher failure rate as the path size increases. Specifically, we see that the reliability achievable by approach B drops 18% while the reliability achievable by approach A drops as much as 74%.  
Figure 16: Reliability achievable when varying the number of bridges in a network with a BER of \(1\times 10^{-6}\). Approach A is represented in orange and approach B in green. The \(x\) axis represents the number of bridges, while the \(y\) axis represents the reliability.  
Figure 15: Reliability achievable when varying the number of bridges in a network with a BER of \(1\times 10^{-10}\). TSN is represented in grey, approach A in orange and approach B in green. The \(x\) axis represents the number of bridges, while the \(y\) axis represents the reliability. (**a**) Reliability achievable by TSN, approach A and approach B when varying the number of bridges. (**b**) Zoom in the reliability achievable by approach A and approach B when varying the number of bridges.