  Network slicing allows Mobile Network Operators to split the physical
infrastructure into isolated virtual networks (slices), managed by Service
Providers to accommodate customized services. The Service Function Chains
(SFCs) belonging to a slice are usually deployed on a best-effort premise:
nothing guarantees that network infrastructure resources will be sufficient to
support a varying number of users, each with uncertain requirements. Taking the
perspective of a network Infrastructure Provider (InP), this paper proposes a
resource provisioning approach for slices, robust to a partly unknown number of
users with random usage of the slice resources. The provisioning scheme aims to
maximize the total earnings of the InP, while providing a probabilistic
guarantee that the amount of provisioned network resources will meet the slice
requirements. Moreover, the proposed provisioning approach is performed so as
to limit its impact on low-priority background services, which may co-exist
with slices in the infrastructure network. A Mixed Integer Linear Programming
formulation of the slice resource provisioning problem is proposed. Optimal
joint and suboptimal sequential solutions are proposed. These solutions are
compared to a provisioning scheme that does not account for best-effort
services sharing the common infrastructure network.
