Abstract: Operating state control in redundancy protection systems is disclosed. One protecting apparatus of a redundant pair is selected to be in a first operating state in the redundant pair. Protected communication equipment for which the redundant pair provides redundancy protection transmits, to only the selected apparatus, communication traffic that includes content for further transmission from both protecting apparatus in the redundant pair. This causes the selected protecting apparatus to transition to or remain in the first operating state and the other protecting apparatus to transition to or remain in a second operating state. A protecting apparatus determines that it is to be in the first operating state if communication traffic received from the protected equipment includes content for further transmission from the protecting apparatus, and determines that it is to be in the second operating state if the received communication traffic includes no such content.

Abstract: A method and mapper apparatus for reallocating bandwidth used by a data tributary comprising data units, during transport of the data tributary over a communications link by a time division multiplexing (TDM) frame (e.g., a SONET frame comprising N×STS-1s) from a source device to a sink device. Each the data unit occupies one time slot of the frame and the data units are encoded to differentiate between payload data and control codes. At the source device, a designated code (IGNORE CODE) is inserted in each unallocated time slot to identify that the time slot contains no payload data (the designated code being ignored by the sink device). New set(s) of time slots to be allocated (i.e., to increase bandwidth) or de-allocated (i.e., to decrease bandwidth) to the tributary are determined. The new set(s) of time slots are communicated to the sink device. Confirmation of the communication is received from the sink device.

Abstract: This invention relates to a method and apparatus for controlling the flow of fiber channel (FC) data frames from a fiber channel link to a metropolitan area link of lesser bandwidth (a synchronous optical network (SONET)). The release of each data unit by a data source for transport onto the first channel is governed by a credit-based protocol whereby one data unit is released upon the provision of one credit unit. A first marker identifies a high limit H of the buffer at which a first condition occurs, H being less than N and the first condition applying when the number of data units in the buffer is greater than H. A second marker identifies a low limit L of the buffer at which a second condition occurs, L being less than H and the second condition applying when the number of data units in the buffer is less than L. A credit unit owed counter O counts the number of credit units which become owed to the data source when the second condition applies.

Abstract: A method and mapper apparatus for reallocating bandwidth used by a data tributary comprising data units, during transport of the data tributary over a communications link by a time division multiplexing (TDM) frame (e.g., a SONET frame comprising N×STS-1s) from a source device to a sink device. Each the data unit occupies one time slot of the frame and the data units are encoded to differentiate between payload data and control codes. At the source device, a designated code (IGNORE CODE) is inserted in each unallocated time slot to identify that the time slot contains no payload data (the designated code being ignored by the sink device). New set(s) of time slots to be allocated (i.e., to increase bandwidth) or de-allocated (i.e., to decrease bandwidth) to the tributary are determined. The new set(s) of time slots are communicated to the sink device. Confirmation of the communication is received from the sink device.