# A New Bit Repair Fast Reroute Mechanism for Smart Sensors IoT Network Infrastructure
## 2 Related Works  
Several existing solutions dealing with rerouting have been proposed in the IoT and IP network area. Reference [23] presents a new approach of jamming attack tolerant routing using multiple routes constructed on specific zones. This method separates the network into a number of zones and routes the candidate forward nodes of neighbor zones. When a system detects an attack, detour nodes in the network determine zones for proper rerouting and reroute packets intended for victim nodes through forwarding nodes in the obtained specific zones. The authors of [24] present a comprehensive review of IoT sensing applications in WSNs, as well as the problems and tasks that need to be overcome. Some of the problem areas identified by authors are, for example, fault tolerance, the efficiency of the energy consumption, transmission interference, cost feasibility, and proper integration of these components. Based on the identified issues and on our analysis of the IP FRR mechanisms properties, we can currently divide them into two generic groups/types. The first category of IP FRR mechanisms includes all proactive FRR mechanisms. The second category contains a family of reactive FRR mechanisms. A characteristic of proactive FRR mechanisms is that these mechanisms calculate the alternative path in advance before a failure occurs. They act proactively when they already have alternative paths ready to respond to an error, depending on the location of the error. In the event of a failure, this backup path is then immediately installed into the routing table and used by a routing engine to redirect traffic around the failure. The interruption of operation caused by a network failure is therefore only for the time necessary to install a pre-prepared alternative route. This is considered as their undeniable advantage [25]. However, mechanisms in this category also have certain disadvantages identified. These include such properties as the pre-computation, the dependence on link-state routing protocols, complexity of internal algorithm [21; 26; 27; 28; 29]. One of the first mechanisms developed in the field of fast network recovery is the loop-free alternates (LFA for short) mechanism. LFA uses alternative next-hop neighbors that are able to deliver data without creating a routing loop. The selection of a suitable LFA candidate is ensured by several mathematical conditions. The basic version of the LFA mechanism [21; 26; 27] is suitable for certain topologies that are characterized by a high number of redundant links and suitable routing metrics. For topologies that do not meet these parameters, an extension of the classical LFA has been proposed, which is called the remote LFA (RLFA) [28; 29]. RLFA has been proposed for situations where, for some reason, it is not possible to find suitable next-hop candidates according to the LFA conditions. RLFA uses tunneling mechanism to get around the failure towards remote tunnel end. Compared to the original LFA, the R-LFA provides higher repair coverage. Other existing proactive FRR mechanisms are built on different approaches. The equal-cost multi-path (ECMP) [26; 28] uses multiple routing paths that have the same metric in parallel. Multiple routing configurations (MRC) [28; 30; 31] uses different routing tables, while not-via addresses mechanisms [32; 33] use specific addresses for explicit identification of failure. Furthermore, there are several FRR mechanisms exist based on alternative trees [19; 34; 35]. Amongst them, the maximally redundant trees (MRT) one is the most used [36; 37]. The behavior of the reactive mechanism is different in that the alternative path is not calculated in advance. The backup path is constructed as an immediate reaction to the failure of the link itself and the protected flow transmitting through this link. Reactive FRR solutions do not calculate an alternative path in advance. However, the backup path is created after failure detection. Reactive FRR mechanisms are not very numerous.