Intra-Domain Routing Protection Scheme Based on the Minimum Cross-Degree Between the Shortest Path and Backup Path  
[PERSON]  
1 School of Automation and Software Engineering, Shanxi University, Taiyuan 030031, China;  
[EMAIL_ADDRESS] (H.G. ); [EMAIL_ADDRESS] (C.L. ); [EMAIL_ADDRESS] (L.X.) [PERSON]  
1 School of Automation and Software Engineering, Shanxi University, Taiyuan 030031, China;  
[EMAIL_ADDRESS] (H.G. ); [EMAIL_ADDRESS] (C.L. ); [EMAIL_ADDRESS] (L.X.) [PERSON]  
2 China Astronautics Standards Institute, Beijing 100071, China; [EMAIL_ADDRESS] 2  
[PERSON]  
suggest that the vulnerability of critical infrastructure surpasses previous assumptions, as follows: a mere 4% failure of core nodes can trigger a cascade leading to the complete collapse of the Internet's performance. In real-world scenarios, a singular point of failure, such as the 2025 Egypt telecommunications hub fire, can precipitate a sharp 44% decline in national network connectivity. This, in turn, leads to financial transaction disruptions, loss of emergency communications, and subsequent chain reactions. In [2], this paper highlights that an analysis of the CENIC backbone's 5-year fault log reveals that 5% of high-risk links were responsible for over 50% of outage events. Furthermore, the median annual downtime in the access layer (CPE network) reached 72 min. In [3], simulation experiments demonstrate that a single router failure would result in 54% of core routing buffer overflows, impacting 31% of end-users with unacceptable transmission rates of less than 70 Kbps. If key routing pairs fail concurrently, 82% of client services would be entirely disrupted. These findings underscore the persistent threat that network failures pose to the resilience of the digital society through service degradation. Similarly, studies [4; 5] also assert that network failure is largely unavoidable and presents significant challenges. Consequently, bolstering network resilience against failures and ensuring uninterrupted service have emerged as pressing concerns in network research [6; 7]. While existing network failure protection methods such as Loop-Free Alternates (LFA) [8; 9; 10] and Equal-Cost Multi-Path (ECMP) [11] routing have somewhat enhanced network reliability, they possess significant limitations. LFA fails to provide effective backup paths in certain network topologies, and ECMP only offers shortest paths of equivalent costs, demonstrating a lack of flexibility in responding to diverse failure scenarios. These methods exhibit protracted recovery times in complex network environments and necessitate specific network topologies, making it challenging to fulfill the high-availability requirements of contemporary networks. Traditional routing algorithms, including Open Shortest Path First (OSPF) [12] and Intermediate System to Intermediate System (IS-IS) [13], primarily concern themselves with identifying the shortest path to each destination, and thus, they cannot ensure robust connectivity during frequent network failures. Upon detecting a failure, these algorithms initiate global link-state advertisements and subsequently recalculate routes, invariably leading to network interruption [14; 15]. This paper addresses the shortcomings of current methodologies by making the following contributions:  
* This paper introduces an intra-domain routing protection strategy that hinges on the Minimum Crossover Degree Backup Path (MCD-BP). The proposed approach entails identifying a backup path characterized by the lowest degree of crossover to the optimal path. It effectively circumvents potential fault zones, thereby mitigating the impact of network faults on other segments. * We have developed a link deletion rule (where the \"deletion\" of an edge is more of a logical operation than an actual deletion) and iterative optimization process to compute the backup path. This is designed to minimize crossover with the optimal path, while guaranteeing the connectivity of the network topology throughout the computation of the backup path.