Abstract: A method and apparatus are provided for displaying network information to a user connected to a network or sub-network manager of a hierarchical telecommunications network by providing a map on a visual display unit showing network elements and connections between network elements. A plurality of views may be selected which include not only a conventional physical view, in which all network elements and the optical fibre links between them are shown, but also one or more views showing connections at respective virtual container levels (e.g. VC-4, VC-12). In these views only the multiplexers are shown and virtual containers at the respective level are shown as lines joining the multiplexers which are their termination points.

Abstract: A sub-network manager in a telecommunications network such as a synchronous digital hierarchy (SDH) or a synchronous optical network (SONET) filters out secondary (AIS) alarms generated in response to signals received by network elements on incoming links by determining whether the upstream termination point of the incoming link on which the signal was received is within the managed domain of the sub-network manager. If it is within the managed domain, the alarm is blocked. If the upstream termination point is outside the managed domain the alarm is processed further. In the latter case the secondary alarm may be the only indication of the fault causing the alarm that the sub-network manager receives, whereas in the former case it will have received notification from some other alarm, either a primary alarm, such as a loss of signal alarm (LOS) or an AIS alarm generated in response to a signal entering the managed domain from outside.