The promise of telecommunication networks to deliver more demanding and complex applications requires them to become more flexible and efficient. To achieve better performance, telecommunication networks adopt technologies such as NFV (Network Function Virtualization). However, this evolution also brings more potential risks to the telecommunication network. Reliability and resilience are becoming critical for service delivery in the networks. To answer to service requirements of high level availability and reliability, a model with a global view of infrastructure, virtual network elements, and network layer structure is required. Toward this end, this paper presents a Petri Net method to model 5G and beyond telecommunication networks. We introduce an extended Petri Net to model physical infrastructure, virtual infrastructure, network services, their behaviors, and dependencies. We present a simulation result on network availability estimation. This result shows the potential of the Petri Net-based model to be applied to a complex telecommunication system resilience assessment.