Abstract: A method of identifier correlation in a communications network, the network comprising: an identifier translator, for translating at least one identifier of a communications packet, wherein a packet which has passed through the identifier translator comprises translated and untranslated identifiers; the method comprising: selecting a first packet prior to transmission through the identifier translator; selecting a second packet after transmission through the identifier translator which has at least one identifier which is the same as a corresponding identifier of the first packet; and correlating at least one identifier from the first packet which is different to a corresponding identifier of the second packet.