1. A system comprising: a first telecommunications network node, wherein the first node is operable to execute a first system software instance and a policy enforcement point (PEP); a second telecommunications network node operable to execute a policy decision point (PDP) wherein the policy decision point (PDP) is configured to make a decision as to whether a second system software instance should be allowed to execute concurrently with the first system software instance on the first node; and wherein the policy enforcement point (PEP) is configured to prevent the execution of the second system software instance on the basis of a decision provided by the policy decision point (PDP).