Multiplex communications – Fault recovery – Bypass an inoperative station
Reexamination Certificate
1998-09-02
2001-06-12
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Fault recovery
Bypass an inoperative station
C370S244000, C370S249000, C370S405000, C714S004110
Reexamination Certificate
active
06246667
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to bidirectional multiplex section-switched ring transmission systems and, more particularly, to a failure restoration method and apparatus for use in such systems.
BACKGROUND OF THE INVENTION
In prior known bidirectional multiplex section switched self-healing ring transmission systems (also referred to herein as bi-directional line-switched rings (BLSRs)), bridging and switching, in the presence of a fault, was restricted to switching at the BLSR nodes which border to the fault. A problem with such an arrangement, in long distance networks, is that the restoration path can be extremely long. In certain applications, for example, transoceanic BLSR transmission systems, the length of the restoration path would be looped and may cause signals to traverse the ocean three times for particular fault conditions making the path extremely long, causing long delays and degraded system performance. The long delays and degraded service is extremely undesirable.
The notion of eliminating BLSR restoration path delay is not a new one, prior U.S. Pat. No. 5,341,364 entitled “Distributed Switching in Bi-directional Multiplex Section-Switched Ring Transmission Systems” by Marra et al., issued on Aug. 23, 1994 provided one solution to the problem. However, the method described in this patent has the disadvantage that it may not be compatible with conventional BLSR nodes, since it explicitly relies on the absence of BLSR loopbacks at the nodes bordering the failure. BLSR compatibility is important for at least two reasons: the first is mixed-vendor operation, and the second is software upgrades. What is needed is a method and apparatus which eliminates BLSR node restoration path delay yet which is compatible with existing BLSR loopback operation.
SUMMARY OF THE INVENTION
The prior restoration problems resulting from a system transmission path degradation are overcome, in accordance with the principles of the invention, by the use of a jumper flag indicating an establishment of a jumpered connection path, for each active tributary affected by the path degradation. The jumpered connection path at an affected node eliminates any unnecessary loop formed in the re-established connection path caused by the loopback connection at that node.
In accordance with the invention, there is stored in memory at each node entries identifying (1) its provisioned (or normal) service connection path and (2) a jumper flag indicating if a jumpered connection path exists.
In response to a loopback setup complete message received at a node, from both the first and second directions, it is determined if a jumpered connection is needed at that node. If a jumpered connection is not needed, conventional BLSR processing is performed. If a jumpered connection is needed, the provisioned connection is taken down, the jumpered connection is put up, a jumper flag is set, and conventional BLSR processing is performed.
In response to a loopback takedown message received at a node, from both the first and second directions, conventional BLSR processing is performed.
In response to a signal fail/degrade or a signal fail/degrade clear message received at a node, from both the first and second directions, it is determined if a jumper flag is set at that node. If the jumper flag is set, the jumpered connection is taken down, the provisioned connection is restored, and the jumper flag is reset. If the jumper flag is not set, conventional BLSR processing is performed.
Advantageously, the operation of the present invention can be programmed into existing node controllers and is compatible with existing restoration procedures.
REFERENCES:
patent: 5341364 (1994-08-01), Marra et al.
patent: 5442623 (1995-08-01), Wu
patent: 5636205 (1997-06-01), Suzuki et al.
patent: 5712846 (1998-01-01), Yoshimura
patent: 5721727 (1998-02-01), Ashi et al.
patent: 5901137 (1999-05-01), Nakabayashi
Ballintine James E.
Kremer Wilhelm
Nelson Bruce L.
Raychaudhuri Kamal Kumar
Caccuro John A.
Hsu Alpus H.
Lucent Technologies - Inc.
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