Methods and Apparatus for Selecting the Better Cell From Redundant Streams Within A Cell-Oriented Environment.

Abstract

The specification discloses methods and apparatus for selecting the better of two or more copies of a cell in a cell-oriented redundant switching system connected to an external communications network. In the preferred embodiment, the best cell copy selection aligns redundantly transmitted cell streams before selecting cells for insertion in the data stream. Because the streams are aligned before the selection is made, the best cell copy selector compares each cell at the same instant in time, rather than basing its selection on past events.

What is claimed is: 
     
         1 . A method for selecting data at a network node coupled to a communications network, the method comprising:
 selecting a better copy of data at the network node from at least two copies of the data in redundantly transmitted streams, received via one or more communications paths, based on an error status identified for each of the at least two copies of the data in the redundantly transmitted streams.   
     
     
         2 . The method of  claim 1  wherein selecting the better copy of the data from the at least two copies of the data in the redundantly transmitted streams is further based on an arrival status identified for each of the at least two copies of the data in the redundantly transmitted streams. 
     
     
         3 . The method of  claim 1  further comprising:
 identifying a preferred switch network copy from the at least two copies of the data in the redundantly transmitted streams, the preferred switch network copy being data from one of the redundantly transmitted streams from which a last better copy of data was selected; and 
 selecting the preferred switch network copy as the better copy of the data based on each of the at least two copies of the data in the redundantly transmitted streams having an error status indicating bit errors. 
 
     
     
         4 . The method of  claim 1  wherein the redundantly transmitted streams each includes an asynchronous transfer mode cell. 
     
     
         5 . The method of  claim 1  wherein the redundantly transmitted streams each includes a synchronous transfer mode cell. 
     
     
         6 . The method of  claim 1  wherein the redundantly transmitted streams each includes an Internet protocol packet. 
     
     
         7 . The method of  claim 1  wherein the method is performed by an Application Specific Integrated Circuit (ASIC) at the network node. 
     
     
         8 . The method of  claim 1  further comprising:
 inserting the better copy of the data selected into a data stream being sent by the network node or generating a cell or packet at the network node and incorporating the better copy into the cell or packet prior to sending the cell or the packet from the network node. 
 
     
     
         9 . The method of  claim 1  further comprising:
 extracting overhead status information from each of the redundantly transmitted cell streams and maintaining the overhead status information in one or more memory locations of at least one memory in the network node. 
 
     
     
         10 . The method of  claim 1  further comprising:
 absorbing delay variation resulting from data received from one of the redundantly transmitted streams at non-regular intervals. 
 
     
     
         11 . A network node for selecting data, the network node comprising:
 a network interface configured to receive redundantly transmitted streams; and   a selection module configured to select a better copy of data from at least two copies of the data in the redundantly transmitted streams, received via one or more communications paths, based on an error status identified for each of the at least two copies of the data in the redundantly transmitted streams.   
     
     
         12 . The network node of  claim 11  wherein the selection module is further configured to select the better copy of the data from the at least two copies of the data in the redundantly transmitted streams based on an arrival status identified for each of the at least two copies of the data in the redundantly transmitted streams. 
     
     
         13 . The network node of  claim 11  wherein the selection module further includes:
 an identification module configured to identify a preferred switch network copy from the at least two copies of the data in the redundantly transmitted streams, the preferred switch network copy being data from one of the redundantly transmitted streams from which a last better copy of data was selected; and 
 wherein the selection module is further configured to select the preferred switch network copy as the better copy of the data based on each of the at least two copies of the data in the redundantly transmitted streams having an error status indicating bit errors. 
 
     
     
         14 . The network node of  claim 11  wherein the redundantly transmitted streams each includes an asynchronous transfer mode cell. 
     
     
         15 . The network node of  claim 11  wherein the redundantly transmitted streams each includes a synchronous transfer mode cell. 
     
     
         16 . The network node of  claim 11  wherein the redundantly transmitted streams each includes an Internet protocol packet. 
     
     
         17 . The network node of  claim 11  wherein the selection module is an Application Specific Integrated Circuit (ASIC). 
     
     
         18 . The network node of  claim 11  further comprising:
 a transmission module configured to insert the better copy of the data selected into a data stream being sent by the network node or to generate a cell or packet incorporating the better copy into the cell or the packet prior to sending the cell or packet from the network node. 
 
     
     
         19 . The network node of  claim 11  further comprising:
 at least one memory; and 
 an extractor module configured to extract overhead status information from each of the redundantly transmitted cell streams and to maintain the overhead status information in one or more memory locations of the at least one memory in the network node. 
 
     
     
         20 . A non-transient computer-readable medium having stored thereon a sequence of instructions which, when loaded and executed by a processor, causes the processor to:
 select a better copy of data from at least two copies of data in redundantly transmitted streams, received via one or more communications paths, based on an error status identified for each of the at least two copies of the data in the redundantly transmitted streams.