;zhiguo.zeng;anne.barros}@centralesupelec.fr 5G and Beyond networks are expected to be reliable solutions to support new and complicated wireless communication scenarios. As high-speed railway systems are booming all around the world, they bring about novel challenges to the 5G and Beyond networks to support high mobility usage. Railway communication functionality has higher performance requirements than other use cases. These requirements will be satisfied by providing an ultra-reliable 5G and Beyond system and seamless handover procedures under high mobility. On the one hand, the system faces failures from its virtual and physical layers. On the other hand, high mobility creates radio issues on handover and interrupts network services. Network service reliability performance can be guaranteed by continuous end-to-end user plane connectivity. This connectivity is maintained by successful handover during radio zone changes. Handover is a signaling process in the control plane. Therefore, the railway network service reliability analysis requires a combined perspective of user and control planes. This paper investigates the possible challenges of high-speed railway network service reliability and examines the impacts of various factors. By using discrete event simulation, we calculate the onboard network communication service reliability during its mission. The impacts of different telecommunication network deployments on network and service reliability are compared. Simulation results provide insights into estimating service performance and propose feasible solutions to improve service continuity and reliability for railway operators and network providers.