  Network Service Chaining (NSC) is a service deployment concept that promises
increased flexibility and cost efficiency for future carrier networks. NSC has
received considerable attention in the standardization and research communities
lately. However, NSC is largely undefined in the peer-reviewed literature. In
fact, a literature review reveals that the role of NSC enabling technologies is
up for discussion, and so are the key research challenges lying ahead. This
paper addresses these topics by motivating our research interest towards
advanced dynamic NSC and detailing the main aspects to be considered in the
context of carrier-grade telecommunication networks. We present design
considerations and system requirements alongside use cases that illustrate the
advantages of adopting NSC. We detail prominent research challenges during the
typical lifecycle of a network service chain in an operational
telecommunications network, including service chain description, programming,
deployment, and debugging, and summarize our security considerations. We
conclude this paper with an outlook on future work in this area.
