A form of notification information that consists of the documentation of the actual sequence of intermediate networks traversed by a signalling message. The documentation of the sequence of networks traversed may also include the origination and destination networks. The documentation that the message traversed a given network is performed by that network itself. Intermediate networks that are not ISNI-capable are not identified. ISNI identification information can be used to force a return error message, destined for the originating SEP, to transit the same intermediate network (s) as the original message.