# Enhanced Bit Repair IP Fast Reroute Mechanism for Rapid Network Recovery
## 1 Introduction  
In 2020 and 2021, communication networks have faced and will face challenges due to the spread of the COVID-19 virus [1]. COVID-19 has moved most offline meetings and services into online spaces and led to a further radical increase in the traffic generated in existing IP networks [2]. Today, IP networks, as a true example of today's converged networks, face the challenge of meeting the diverse requirements of a wide portfolio of communication services, whether used by humans or machines. The network is therefore required to meet very specific and diverse qualitative and quantitative parameters for a diverse range of services operated, where others are for real-time communication services [3], wireless sensor services [4; 5; 6; 7; 8; 9], mission-critical services, Software-Defined Networking (SDN) [10] and other important systems such as intelligent transport systems [11]. These services, to provide the expected quality and functionality, have their critical network performance requirements, including delay, availability, jitter, and packet loss [12; 13; 14; 15]. Moreover, all these factors are thus negatively affected by unpredictable links or node failures in the network. In this situation, a network device is unable to route data correctly based on its current information, as some of its routing information is no longer valid. Therefore, the network device (a router) must start a network convergence process, in which it informsthe neighbors about the change and updates its routing knowledge based on the mutual exchange of current routing information. The length of the network convergence process is affected by the complexity of the network and the routing protocol used in the network. Until the process is complete, the routing of packets is performed based on outdated or missing entries, and many packets may be lost. Great efforts have been made to reduce the time required for a routing protocol to advertise information about network changes and recalculate the new set of shortest routes [14; 15; 16; 17; 18; 19; 20; 21; 22; 23]. However, simply shortening the routing protocol timers to achieve faster network convergence is not recommended as this can lead to network destabilization by making the routing protocol too responsive [24; 25; 26]. To meet these complex requirements, it is therefore necessary for Internet Service Provider (ISP) to deploy and correctly use multiple solutions to ensure a reliable connection for the customers and the services they offer. One of the types of mechanisms that focus on situations of unexpected network failures is the IP Fast Reroute (hereinafter referred to as IP FRR or FRR) mechanisms (Figure 1). Addressing these issues, the IP Fast Reroute mechanisms have been developed to decrease the network convergence time and minimize traffic losses [27; 28; 29; 30; 31; 32].  
To achieve rapid traffic recovery, the first of the IP Fast Reroute mechanisms calculates an alternative path in advance, before the link or node fails. When a failure is detected, for example, detecting the loss of carrier, the FRR-enabled router immediately uses this backup path in response to the failure and forwards packets to a new neighboring router on the alternative path, rather than just starting convergence and calculating a new path, as it is common in traditional routed networks. Using current IP FRR approaches, the average routing recovery time ranges from 20 to 50 ms [33].