Graph-Based Quantitative Description of Networks' Slices Isolation

5G networks are expected to be a set of slices which are virtual subnets designed for specific applications. A crucial requirement for providing proper functioning of the network and its security is proper isolation of slices. The aim of this paper is to propose a new method of determination of the isolation level of a slice. We propose a Graph-based model of the sliced network, which has a layered structure. In each layer, the appropriate network elements have their own isolation level. The lowest layer of the Graph-based model represents virtual network elements with isolation traits used for calculating their isolation level. Climbing to the top of the stack of layers one can calculate, successively, isolation level for a network's physical element, a link, subnetworks and, the End-to-End slice's isolation level. We present numerical examples, where suitable traits are specified and the isolation level in each layer is calculated.