  Network Functions Virtualization (NFV) allows flexibility, scalability,
agility, and easy manageability of networks by leveraging the features of
virtualization and cloud computing technologies. However, softwarization of
network functions imposes many challenges. Reliability and latency are major
challenges in NFV-enabled 5G networks that can lead to customer dissatisfaction
and revenue loss. In general, redundancy is used to improve the reliability of
communication services. However, redundancy requires the same amount of
additional resources and thus increases cost. In this work, we address the
reliability-aware, delay guaranteed, and resource efficient Service Function
Chain (SFC) placement problem in softwarized 5G networks. First, we propose a
novel SFC subchaining method to enhance the reliability of an SFC without
backups. If reliability requirement is not met after subchaining method, we add
backups to VNFs to meet the reliability requirement. Then, we formulate the
reliable SFC placement problem as an Integer Linear Programming (ILP) problem
in order to solve it optimally. Owing to high computational complexity of the
ILP problem for solving large input instances, we propose a modified stable
matching algorithm to provide near-optimal solution in polynomial time. By
extensive simulations we show that our proposed solutions consume lesser
physical resources compared to state-of-the-art solutions for provisioning
reliable communication services.
