A computer implemented method and telecommunications diagnostic apparatus that correlates packets on a core network with those on the access network. Generated is an identification attribute from Information Elements (IEs) in S1AP packets present in the core network and accessible to the access network. The generated identification attribute is integrated to an access and core session of the access and core network to correlate data packets between the access and core session by comparing if a core session contains the same identification attribute as that of an access session within the life span of the access session.