Nortel Networks Corporation

Ciena Corporation

Notel Networks Corporation

James A Shields

David Michael Goodman

Christopher David Murton

John Paul Russell

Christopher Thomas William Ramsden

Richard Trudel

Evert E deBoer

David William Wiggins

Evert E De Boer

Kim Bryon Roberts

Peter J Ashwood-Smith

Ronald Joseph Gagnon

Malcolm Betts

Evert De Boer

Jayne Brady

Rick R Wedge

Mark Allaye-Chan

In a mesh network, a network element for providing protection switching in a 1:N shared mesh protection scheme having a first protection path associated with a pair of working paths selected from the N working paths is disclosed. The network element comprising: (a) a link for connecting the network element to a first working path of the pair of working paths in a path layer of the network, the path layer including a plurality of interconnected network elements; (b) a routing table accessible by the network element, the routing table for having local protection channel information associated with a local protection segment separate from the first protection path, the local protection segment connecting the network element and one of the interconnected network elements adjacent to the network element; and (c) an identification module for using the local protection channel information to identify an available protection channel on the local protection segment in the event of failure of a local working segment of the first working path, the local working segment connecting the network element and said one of the adjacent interconnected network elements; wherein the available local protection channel on the local protection segment is used to switch local network bandwidth from the failed local working segment to the local protection segment after the failure has been detected. Selection functions are also disclosed.

Shared mesh signaling method and apparatus

A transmission apparatus and a method for operating the apparatus comprises means for controlling flow of frame based data transmitted from a local frame based data channel interface over a synchronous digital network. The method of operation comprises the transmitter receiving frame based data at a first rate whereafter a buffer is configured to receive the frame based data. A data amount threshold level for the buffer is pre-determined whereafter, with respect to the threshold level, an amount of transmitted frame based data that has been received is monitored. In response to monitoring the amount of data received, a signal, in the form of a pause frame, is generated wherein the signal is configurable to adapt the rate of transmission from the frame based data channel interface. Working in conjunction with the transmission means there is also provided a receiver for controlling flow of frame based data, received from a synchronous digital network, to a frame based data channel interface. The receiver is configured to receive the frame based data at a first rate whereafter a buffer is configured to receive the frame based data. Upon pre-determining a data amount threshold level for the buffer an amount of frame based data received is monitored with respect to the threshold level. In response to monitoring the amount of data received, a signal is generated in the form of a pause frame, wherein the pause frame signal is configurable to adapt the first transmission rate of the frame based data over the synchronous digital network to a second rate. In this way, the rate of transmission from a local Ethernet switch may be controlled and the rate of receipt of Ethernet based frame data from a synchronous digital network may be controlled. In the latter case pause frames may be incorporated into one or more synchronous digital hierarchy virtual containers.

Flow control of frame based data over a synchronous digital network

In a mesh communications network, in which working and protection paths may be established, channels used to carry protection traffic between nodes are shared across multiple protection paths. Channels need only be shared if sharing does not adversely impact network usage. If working and protection paths become susceptible to single points of failure, channels need not be shared.

Methods, devices and software for combining protection paths across a communications network

A node within a mesh network includes an Optical Connection Controller (OCC) and a network element. When a connection path within the mesh network is required, an OCC determines if a particular connection path requires a network element to operate as a virtual gateway to separate the mesh network into separate protection domains for that particular connection path. A connection path might require separate protection domains in cases in which the number of network elements and/or repeater/amplifier components for a particular connection path is greater than a threshold, the total length of links for the connection path is above a threshold and/or another factor that could cause the recovery time for the connection path to increase beyond an acceptable threshold level. If the OCC determines that one or more virtual gateways are required for a particular connection path, the OCC selects an appropriate network element within the network to operate as a virtual gateway for that particular connection path. Finally, the OCC assigns network elements and links to establish working and protection paths between the source network element and the virtual gateway and between the virtual gateway and the destination network element. This set-up can ensure that each connection path will have a recovery time after a failure within an acceptable range.

Apparatus and method for establishment and protection of connections within mesh networks

Synchronization and desynchronization of a data signal transported in a synchronous frame across a synchronous communications network, such as SONET/SDH, reduces waiting-time jitter. A timing estimate (F) indicative of a relationship between a data rate (f) of the data signal and a reference frequency (f) of the synchronous communications network is calculated and communicated through the synchronous communications network, for example in the Synchronous Payload Envelope of a SONET frame. The data signal is recovered using a desynchronizer Phase-Locked Loop steered by the timing estimate (F). The timing estimate (F) can be any one or more of: a ratio between the data rate (f) and the reference frequency (f); a difference between the data rate (f) and the reference frequency (f); and a phase difference between a recovered data clock signal associated with the data rate (f) and a reference clock signal associated with the reference frequency (f).

Method and apparatus for digital data synchronization

A traffic recovery mechanism for communication networks uses a layer-adaptive rate protection scheme that compliments layer-restoration mechanisms. The protection scheme allocates less bandwidth to the traffic during a protection switch than during the normal operating conditions. This scheme allows the network to roll off more gracefully from the perspective of the applications routed through it. Rate adaptation is effected by a new interface between the data equipment and the transport network, which switches information transfer rate between two or more predetermined levels.

Adaptive rate traffic recovery mechanism for communication networks

A shared mesh protection scheme defines an associated protection path when a working connection is established. During the protection path definition, the corresponding protection path information is sent down to a switch card of network elements making up the protection path. Upon detection of the failure, the network elements using an overhead byte message will inform the routing source network element of the connection of the failure in the working path. The overhead bytes used are interrupt driven bytes located in the line and path overhead of network traffic. The routing source node of the connection will then send the corresponding overhead byte messages down the protection path to provide for protection path establishment according to the preloaded data located at the switch card. It should be noted that each connection can have a source and termination element which relates to the source from where the corresponding connection was set-up rather than the direction of the payload transmission. Therefore, once the failure has occurred the source elements will send messages using overhead bytes to the corresponding network elements along the protection path. Accordingly, routing tables located at the switch card of the network elements, set-up when the working path connections were initially established, determine this dynamically allocated protection path environment.

Shared mesh signaling algorithm and apparatus

The SONET/SDH multiplexing hierarchy is extended to very high rates by creating new virtual containers of a higher capacity, and their associate pointers. The multiplexing hierarchy nests the pointers into the payload, so that the number of pointers on the high capacity line is importantly reduced, as the high rate spans of the network do not see the STS-1/STM-1 pointer granularity. Fewer pointers result in reducing the current complexity of pointer processing. The complexity of the multiplexing hierarchy is also reduced by the use of larger containers. The hierarchy may be extended to higher rates, as needed, and may also be used for other technologies, besides SONET/SDH.

Multiplex hierarchy for high capacity transport systems

A frame based data communications network is interfaced to a synchronous digital hierarchy network via a plurality of frame based data port cards incorporated into a plurality of synchronous multiplexers. Each port card comprises a conventional frame based data port, a frame switch, a rate adapter means and a mapping means for mapping data frames into a plurality of SDH virtual containers. Frame based data is incorporated directly into a synchronous virtual container without encapsulation in an intermediate protocol. A number of topologies of a frame based data channel network are possible, overlaid on the underlying synchronous transport network, including an open loop topology, a ring mode topology, and a backhaul topology.

Frame based data transmission over synchronous digital hierarchy network

There is disclosed a method of converting synchronously between a plurality of VC-3 container streams and a plurality of STS-1 synchronous payload envelope streams within the synchronous digital hierarchy. A stream of VC-3 containers is converted to a stream of STS-1 SPEs by reading the VC-3s in a VC-4 container stream, adding redundant byte columns to each VC-3 stream and re-writing said VC-3 streams to an STS-3 synchronous payload envelope stream. Conversely, a plurality of STS-1 synchronous payload envelope streams are converted to a plurality of VC-3 virtual container streams by reading the STS-1 SPE streams from an STS-3C SPE stream; removing redundant stuff byte columns from each STS-1 SPE stream; writing the STS-1 SPE streams to a VC-4 virtual container stream; recalculating pointer positions, writing pointer bytes to the VC-4 stream, and adding a plurality of redundant stuff bytes to the VC-4 container stream.

Payload translation between frame options in synchronous digital hierarchy networks

In the situation that data switching is incorporated in a wide area telecommunications network it is advantageous to use a local area network protocol such as ethernet which allows network resources to be shared. However, this introduces a problem with respect to loops in the network and the possibility of infinite packet looping. If the known spanning tree algorithm is used to prevent infinite packet looping this is problematic because the known algorithm takes a relatively long time to take effect. An algorithm is described which is based on assumptions about the topology of the communications network and which is simpler and faster.

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Ottawa, Canada

James A Shields