Abstract: A novel and useful mechanism for optical ring networks providing concentrator redundancy in the event of a failure of a concentrator. The nodes in a network are connected to dual concentrators to form bi-directional dual counter-rotating optical rings. The failure of one of the concentrators is detected and the internal connections of the surviving concentrator are reconfigured to form a single ring that provides an alternate communication path thus preventing the collapse of the ring. Reliability of optical rings is improved by enabling the ring to continue to function in the event of a concentrator failure.

Abstract: A novel and useful mechanism for detecting the nodes connected to a network device and for creating a ring network from the nodes detected thereby. The invention simplifies insertion, removal and modification of nodes in the ring by detecting and reconfiguring the ring without requiring intervention by a user. Identification information messages generated by network devices and sent out on all links and received over a plurality of ports are used in identifying and determining the connectivity and topology of the network devices. The resulting topology information is stored in a node database. The contents of the node database are then used to generate one or more ring networks, wherein each ring generated corresponds to a unique line speed. The connectivity of the one or more rings generated is stored in a ring database and the rings configured therefrom.

Abstract: A novel and useful mechanism of synchronizing and aligning a plurality of data streams. The invention comprises a plurality of sync machines and an alignment circuit which in combination function to synchronize and align multiple variable length cell streams. Each sync machine is operative to control the output clocking of a corresponding FIFO queue. The data stream output of each FIFO queue is monitored by a sync machine and all the sync machines are coupled to the alignment circuit. In operation, the sync machines synchronize to the cells by searching for the error checks sequence (ECS) at the end of each cell. Upon synchronization being achieved for all the data streams, the alignment circuit causes each sync machine to freeze its respective FIFO until the ECS arrives on the data stream most delayed in time. Once the ECS is received on the slowest data stream, the alignment circuit releases the hold and consequently the FIFOs are released by the sync machines.

Abstract: A novel and useful apparatus for and method of in-band clock compensation for use in synchronous communication systems. The clock compensation mechanism is implemented in each module and is operative to compensate for the differences between the clocks among the various modules in the system. The mechanism operates in band wherein special clock compensation symbols are periodically inserted into the data stream itself. Additional clock sync symbols are added to the data stream depending on the current level of the FIFO queue on the module or card. The insertion (or non-insertion) of additional symbols functions to compensate for the faster (or slower) clock of the module when compared to that of the reference.