Nortel Networks Corporation

Northern Telecom Limited

Notel Networks Corporation

David Michael Goodman

Christopher David Murton

John Paul Russell

Christopher Thomas William Ramsden

James A Shields

Mark Brian Carson

James Alexander Shields

John Courtney

David William Wiggins

Chris Murton

Christopher Ramsden

Kim Bryon Roberts

Adonios Bitzanis

Dino Cosimo DiPerna

Jayne Brady

Gareth Dalzell

Carlo Capaldo

Clifford Townsend

James Shields

A method of transmitting OSI layerdatacoms data by direct incorporation into a plurality of synchronous digital hierarchy virtual containers is disclosed, in which a higher bit rate OSI layerdata frame is multiplexed into a plurality of lower bit rate SDH (or SONET) virtual containers, which are transmitted simultaneously and in parallel over a synchronous communications network. The plurality of virtual containers are virtually concatenated by association of the payloads of the plurality of virtual containers. Re-assembly of the OSI layerdata frames from a plurality of virtually concatenated VCs is achieved by storing each received VC payload corresponding to an OSI layerdata frame in a corresponding respective memory location, and alternately reading interleaved bytes from the plurality of payloads under control of a plurality of read pointers.

Concatenation of containers in synchronous digital hierarchy network

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

The invention provides a method and apparatus for providing hitless protection switching in a transmission systems which support a standardized implementation of virtual concatenation. A switching apparatus is arranged to receive data signals on at least two transmission paths and to output data from a selected one of said transmission paths. The apparatus is arranged to align the respective received data signals so that a selector mechanism can select between corresponding elements of the received data signals. This arrangement allows hitless switching to be performed since there is no loss or repetition of signal elements when switching occurs. In a preferred embodiment, data in respect of each frame of each data signal is stored and the selector mechanism selects between paths on a frame-by-frame basis by comparing quality information carried by the data signals. This arrangement offers a very low end to end Bit Error Rate (BER) performance. The invention is suitable for both synchronous and non-synchronous networks (for example, OTN) which implement standardized virtual concatenation.

Hitless protection switching

The invention provides a method and apparatus for providing hitless protection switching in a synchronous transmission system. A switching apparatus is arranged to receive data signals on at least two transmission paths and to output data from a selected one of said transmission paths. The apparatus is arranged to align the respective received data signals so that a selector mechanism can select between corresponding elements of the received data signals. This arrangement allows hitless switching to be performed since there is no loss or repetition of signal elements when switching occurs. In a preferred embodiment, data in respect of each frame of each data signal is stored and the selector mechanism selects between paths on a frame-by-frame basis by comparing quality information carried by the data signals. This arrangement offers a very low end to end Bit Error Rate (BER) performance.

The invention concerns a switching apparatus comprising a low order switch subtended from a high order switch. In order to compensate for delays incurred by passing a data frame through the high order switch to the low order switch and delays incurred by the operation of the low order switch, the apparatus is arranged to advance the payload of a received data frame with respect to the fixed overhead of the data frame by an amount corresponding to the incurred delays. The low order switch uses the advanced payload to create an output frame, for sending to the high order switch, which is advanced with respect to the data frame that it receives. The apparatus, which is particularly suitable for use in SDH and/or SONET systems, obviates the need to provide an alignment apparatus, such as a VT/TU aligner between the high order switch and the subtended low order switch.

Switch subtending in a synchronous transmission system

In order to allow geographically separate SONET/SDH networks to be interconnected transparently without changes in clock content, payload and overhead, it has conventionally necessary to use dark fiber. For relatively low bandwidth operators this is prohibitively expensive. The present invention proposes a scheme using a mapping and virtual concatenation scheme to allow SONET/SDH to be carried in a bandwidth efficient manner over a SONET/SDH link whilst maintaining clock integrity.

Methods and apparatus for transmitting synchronous data

A high capacity switch for switching communications traffic. The high capacity switch has a plurality of differing granularity switching levels, each switching level having at least one switch node capable of performing a switching operation at the granularity of the switching level and at least two primary connections, each connecting one of the switching levels to another one of the switching levels. At one of the switching levels, at least one switch node is capable of switching communications traffic along at least one switch connection path established along one of the primary connections, and is also capable of switching communications traffic along at least one secondary connection to another switch node within the same switching level, such that each of the at least one switch connection paths established is filled to a predetermined level.

Non-blocking high capacity fine grain switch

The invention relates to message signalling in a synchronous transmission apparatus using redundant pointer bits as a signalling channel within the apparatus. The preferred embodiment uses one or more of the new data flag (NDF) pointer bits as a signalling channel. The invention has particular, but not exclusive, application in the field of performance monitoring in a path protected telecommunications network, where the pointer bit signalling channel is used to communicate between data ports which transmission path is selected.

Message signalling in a synchronous transmission apparatus

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 carrying frame based data, eg Ethernet data, over a synchronous digital hierarchy network in order to provide local area network type functionality over a wide area network coverage. Specific embodiments disclose methods of mapping Ethernet data frames into SDH virtual containers, and distinguishing start and end boundaries of the Ethernet data frames within the virtual container payloads, by a selection of encoding methods including a segmentation, pointer methods, bit stuffing methods and byte stuffing methods. Data frames are encoded with a code which designates a boundary of each frame, and the encoded frames are input into a synchronous data channel.

Payload mapping in synchronous networks

An interface for converting a variety of incoming digital signals into SDH/SONET format for transmission on a synchronous digital network, by identifying the line code of the incoming digital signal, without identifying the information for OSI layer 2 or 3 processing, i.e. format of each packet. Headers are used to encapsulate incoming packets, and enable packets to be discriminated at the receiver. Advantages of performance monitoring capability and transparency are combined. Identifying line codes enables a greater degree of error detection, than a bit based interface. Also synchronisation can be simpler since line codes for padding can be added or deleted more easily than adding or subtracting bits. The interface is semi-transparent in the sense that identification of line codes limits the interface to those formats that use identifiable line codes, but without limiting to a particular OSI layer 2 or 3 frame format.

Semi transparent tributary for synchronous transmission

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

A synchronous digital communications network incorporating a number of nodes arranged in path protected rings and has two or more timing reference sources. The reference sources each allocated an artificial ranking of unique quality level values and these quality level values are transmitted as a section overhead message to provide a unique identifier for each source. Identification of the source to a node enables that node to be aware of a synchronization signal that has in fact originated from that node so as to prevent the setting up of synchronization loops. In a further embodiment the technique is extended to protection path identification for signals coupled between adjacent rings in a network having ring topology.

Growing community of inventors

St. Albans, United Kingdom

David Michael Goodman