Identifiability of an imbedding unknown subnetwork

Consider an unknown network
N_{\chi}
imbedded in a network
N_{T}
. Let the accessible nodes be connected to the known part of the network
N_{T}
, namely,
N = N_{T} - N_{\chi}
. The problem of the identifiability of
N_{\chi}
from the set of accessible nodes is investigated. It is shown that if a topological condition on
N
is satisfied then for almost all parameters of
N
, any
N_{\chi}
is identifiable. Furthermore, this topological condition is also necessary.