  In this article, we propose a novel formulation for the resource allocation
problem of a sliced and disaggregated Radio Access Network (RAN) and its
transport network. Our proposal assures an end-to-end delay bound for the
Ultra-Reliable and Low-Latency Communication (URLLC) use case while jointly
considering the number of admitted users, the transmission rate allocation per
slice, the functional split of RAN nodes and the routing paths in the transport
network. We use deterministic network calculus theory to calculate delay along
the transport network connecting disaggregated RANs deploying network functions
at the Radio Unit (RU), Distributed Unit (DU), and Central Unit (CU) nodes. The
maximum end-to-end delay is a constraint in the optimization-based formulation
that aims to maximize Mobile Network Operator (MNO) profit, considering a cash
flow analysis to model revenue and operational costs using data from one of the
world's leading MNOs. The optimization model leverages a Flexible Functional
Split (FFS) approach to provide a new degree of freedom to the resource
allocation strategy. Simulation results reveal that, due to its non-linear
nature, there is no trivial solution to the proposed optimization problem
formulation. Our proposal guarantees a maximum delay for URLLC services while
satisfying minimal bandwidth requirements for enhanced Mobile BroadBand (eMBB)
services and maximizing the MNO's profit.
