# Design of a Technique for Accelerating the WSN Convergence Process
## 3 Theoretical Principles Used in Research  
### Fast Reroute (FRR)  
FRR mechanisms serve to ensure fast and reliable transmission in a network, minimize the impact of an outage on operation, and thus improve the availability of services. The principle of operation of the FRR mechanism is presented in [49]. There are two different approaches to Fast Reroute in IP networks. The speed at which these accesses can be performed depends on the network conditions, namely the network topology, available resources, and the type of error or event. A local repair is usually faster than a global repair, because it is limited to the area around the fault location. In the event of a local repair, backup routes or route redirection within the local circuit will be used to work around the error. This approach is faster because it does not require changing the overall network topology. On the other hand, a global fix would involve changing the entire network topology, which can be time-consuming and complex. This approach is suitable if the fault is very serious and affects a large part of the network. The exact speed ratio between local and global patching depends on the specific circumstances and technologies used in the network. In some cases, an in-place repair can be hundreds of times faster, while in other cases, it can only be a few times faster. It is a matter of network design and specific implementation details. An example of comparing these two types of repairs from the point of view of speed is shown in the following Figure 1.  
Global repair (Global Fast Reroute) in computer networks is performed through various techniques and protocols that ensure fast bypassing of errors or failures in the network at the overall topological level. These techniques and protocols may include the following [50; 51]:  
Multiprotocol Label Switching (MPLS): MPLS is a technology that enables efficient routing of data flow in the network based on labels instead of traditional routing based on IP addresses. In the event of a failure, an alternative MPLS path (fast error bypass) can be created via another route [52; 53]. Figure 1: Comparison of local and global correction. Interior Gateway Protocol (IGP) Fast Reroute: Many interior gateways in a network, such as Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (IS-IS), can support fast error workarounds through various mechanisms such as congestion connections or microcircuits that allow immediate redirection of the data flow [54]. Border Gateway Protocol (BGP) Multipath: In the case of multipath BGP configurations, routers in the network can have multiple alternative paths. In the event of an error, these alternate paths can be used to quickly redirect the data flow [55]. Segment Routing: This is an innovative routing technique that allows network paths to be defined using segments or stages, without the need for complex routing tables. Segment Routing can be used to implement fast workaround for network errors [52]. The exact techniques and protocols used for global patching may vary depending on the specific network implementation and availability and speed requirements. The goal is to ensure that in the event of network errors or failures, data are quickly and efficiently rerouted along alternative routes to minimize service disruption and data loss. The main advantage of local repair is its speed and efficiency. By using the shortest possible alternative path, traffic can be quickly rerouted without significant network disruption. This is particularly important when high levels of availability are required, such as for networks where critical application or service data pass. The time required for local repair is an important factor by which FRR mechanisms are compared [10; 11; 12].