  Service Function Chaining (SFC) is a trending paradigm, which has helped to
introduce unseen flexibility in telecom networks. Network service providers, as
well as big network infrastructure providers, are competing to offer
personalized services for their customers. Hence, added value services require
the invocation of various elementary functions called Service Functions (SFs).
The SFC concept composes and imposes the order in which SFs are invoked for a
particular service. Emerging technologies such as Software Defined Networking
and Network Function Virtualization support the dynamic creation and management
of SFC. Even though SFC is an active technical area where several aspects were
already standardized and many SFC architecture flavors are currently deployed,
yet some challenges and open issues are still to be solved. In this paper, we
present different research problems related to SFC and investigate several key
challenges that should be addressed to realize more reliable SFC operations.
