Alcatel

Alcatel Lucent

Martin Huck

Stefan Ansorge

Dieter Beller

Hans-Jörg Jäkel

Uwe Knebel

Jörg Jäkel

Walter Kailbach

Kerstin Skerra

To restore a failed working path (WP) in a transport network, a restoration request is relayed between adjacent network elements (NENE) and the path set up hop by hop over spare resources by establishing local crossconnections (CCCC) conforming to the request according to routing information locally stored within the network elements. During failure free operation, a low priority path (LPP A) for extra traffic with different signal structure is allowed on the spare resources and pre-empted in the case of a failure. The restoration request is forwarded using the old signal structure of the extra traffic path. Only after reception of a confirmation sent back by the peering node (NE) using the new signal structure, the I/O port () is also reconfigured to the new signal structure.

Transport network restoration method supporting extra traffic

Transmission signals in a transport network are multiplexed from traffic streams respectively representing paths. Each path is identified with a path tag and forwarding information is provided in each network element. Failed paths in the network are restored in that the source network element crossconnects the affected traffic stream to an alternate output port and subsequent network elements receiving this unexpected traffic stream at an input port check the received path tag, determine an appropriate output port based on the tag and the forwarding information, and establish an internal cross-connection between the input port and corresponding output port.

Transport network restoration method

A method for the automatic activation and deactivation of a tandem connection (-) is provided responsive to receiving an activation or deactivation request. Prior to activation, received transmission signals are monitored (M) for an existing tandem connection to avoid creation of overlapping tandem connections. Further, responsive to receiving a deactivation request, the tandem connection sink function (SK) is deactivated and the existing tandem connection is monitored (M) to detect when no tandem connection information is received anymore to automatically deactivate the tandem connection source function (SO) as well. Direct signaling of a sink inactive identifier (RDI) takes also place between the tandem connection terminating network elements () to inform the far end tandem connection terminating network element () of an automatic deactivation of the tandem connection sink function (SK). Upon reception of the sink inactive identifier (RDI), the far end network element () deactivates its tandem connection source function (SO).

Tandem connection activation/deactivation

Paths in a transport network are identified by labels (n-n, b-b) and more than one restoration resources that can be used for setting up a particular backup path form a restoration group. Backup tables (R, R) are provided, which define restoration groups per path labels (b-b), only, rather than individual restoration resources. Upon initial receipt of a path label (b-b), a network element (-) selects according to pre-determined rules a particular restoration resource from the restoration group defined in the backup table (R-R) for this backup path label.

Method of setting up a backup path in a transport network

A method for re-configuring a network element of a transmission network to restore traffic after occurrence of a failure is proposed. Each configuration request is divided into two phases: At first a 'fetch-ahead' phase and then a 'consolidation'. During fetch-ahead, only configuration steps essential for fast implementation of a new cross-connection are performed and security related configuration steps skipped thereby providing reduced security against process restarts. During consolidation, those previously skipped security related configuration steps are then executed and the changes made persistent.

Fast reconfiguration of network elements

An 1:n or m:n path protection mechanism is provided. Rather than defining an automatic protection protocol, use is made of the existing tandem connection monitoring function, tandem connection reverse defect indication, and tandem connection trail trace identifier. Upon detection of a failure on the working path segment, the occurrence of this failure is communicated to the far end node by inserting forced RDI into the tandem connection as long as the failure persists. In the case of more than one protected paths, the failed path is identified by means of the unique trail trace identifier received on the protection path. In the case of several protection paths, one network node is defined as slave node which has to follow the switch-over initiated by the master node and choose the same protection path as the master node. Preferably, a combination of two timers enables return from failure condition to normal operation.

M:N path protection

Failures are localized through the use of a Tandem Connection along a segment of a transmission path (P) to be monitored, non-intrusive intermediate Tandem Connection monitors (M), and temporary Tandem Connection sources created along the path segment in the case of a failure (F) in order to forward information about the fault location at least in downstream direction but preferably also in upstream direction. In particular, a failure adjacent network element (N) detects the failure and activates a temporary tandem connection source function (TS, TS). This function creates a valid tandem connection signal and insert therein a failed link identifier (TTI). The network element (N) terminating the tandem connection generates an alarm report including the failed link as indicated by the failed link identifier.

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Möglingen, Germany

Martin Huck