  The paradigm of network function virtualization (NFV) with the support of
software defined networking (SDN) emerges as a promising approach for
customizing network services in fifth generation (5G) networks. In this paper,
a multicast service orchestration framework is presented, where joint traffic
routing and virtual network function (NF) placement are studied for
accommodating multicast services over an NFV-enabled physical substrate
network. First, we investigate a joint routing and NF placement problem for a
single multicast request accommodated over a physical substrate network, with
both single-path and multipath traffic routing. The joint problem is formulated
as a mixed integer linear programming (MILP) problem to minimize the function
and link provisioning costs, under the physical network resource constraints,
flow conservation constraints, and NF placement rules; Second, we develop an
MILP formulation that jointly handles the static embedding of multiple service
requests over the physical substrate network, where we determine the optimal
combination of multiple services for embedding and their joint routing and
placement configurations, such that the aggregate throughput of the physical
substrate is maximized, while the function and link provisioning costs are
minimized. Since the presented problem formulations are NP-hard, low complexity
heuristic algorithms are proposed to find an efficient solution for both
single-path and multipath routing scenarios. Simulation results are presented
to demonstrate the effectiveness and accuracy of the proposed heuristic
algorithms.
