Multiplex communications – Fault recovery – Bypass an inoperative switch or inoperative element of a...
Reexamination Certificate
1998-03-18
2001-08-21
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Fault recovery
Bypass an inoperative switch or inoperative element of a...
C370S218000
Reexamination Certificate
active
06278687
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
Synchronous Digital Hierarchy (SDH) equipment is the latest generation of equipment that is used to provide high bandwidth communications capabilities for use between telephone exchanges and in other areas where high quality telecomms is required (broadcast video distribution, etc). Embedded within the ‘traffic’ carrying capability of the equipment are data communications channels (DCCs). These channels constitute a datacomms network that uses Open Systems Interconnections (OSI) protocols.
Each piece of equipment constitutes a routeing node in the datacomms network formed by the data channels, and can operate any one of a number of different methods. The present invention is concerned with the interworking of two of the possible routeing methods.
The two routeing methods that will commonly occur in SDH networks are IS—IS (ISO 10589) and quasi-static routeing (where alternate routes may be chosen on link failure). Where this occurs, routeing loops, causing loss of comms, can be caused. The present invention detects the formation of a routeing loop and changes the behaviour of the IS—IS node accordingly.
SUMMARY OF THE INVENTION
According to the present invention there is provided a Synchronous Digital Hierarchy (SDH) based communications network comprising a plurality of Intermediate Systems (IS), the IS being divided between at least one IS—IS Area and at least one non-IS—IS Area, an IS—IS Area being an area within which a routeing protocol forming part of the Network Layer (Layer 3) of the Open Systems Interconnection including routeing (OIS), is provided for routeing messages between areas, a method is provided wherein static routes (Manual Adjacencies (MA) are created at IS within the IS—IS Area to point to routes to a group of one or more Network Equipments (NEs) within the non-IS—IS Area and where a failure occurs in a link to or within a group and messages from the IS—IS Area to the non-IS—IS Area are looped to the originating IS—IS Area, identification of the NEs from which messages have been looped are removed from the respective MAS allowing routeing of messages via alternative MAS.
REFERENCES:
patent: 5251205 (1993-10-01), Callon et al.
patent: 5430727 (1995-07-01), Callon
patent: 5590118 (1996-12-01), Nederlof
patent: 5678178 (1997-10-01), Tahkokorpi
patent: 6055226 (2000-04-01), Verpooten
Cangialosi Salvatore
Kirschstein et al.
Marconi Communications Limited
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