Payload mapping in synchronous networks

Abstract

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 stufifng 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 asynchronous data channel.

1 . A method for transporting frame based packet data into a synchronous transmission communications network, said method comprising the steps of: 
 encoding at least one packet data frame with a code which designates a boundary of said frame;    inputting said encoded packet data frame into a synchronous data channel.    
     
     
         2 . The method as claimed in  claim 1 , wherein said code is recognizable by a synchronous communications protocol as designating a boundary of a said data frame.  
     
     
         3 . The method as claimed in  claim 1 , wherein said step of encoding at least one packet data frame comprises: 
 appending a fixed pointer describing a position of a said boundary within a data stream containing said packet data frame, said fixed pointer appended into said synchronous digital channel.    
     
     
         4 . The method as claimed in  claim 2 , wherein a said fixed pointer comprises a pointer designating an end of said packet data frame.  
     
     
         5 . The method as claimed in  claim 2 , wherein said fixed pointer comprises a pointer designating a start of said packet data frame.  
     
     
         6 . The method as claimed in  claim 2 , wherein said pointer designates a position of a said boundary within a synchronous virtual container.  
     
     
         7 . The method as claimed in  claim 1 , wherein said step of encoding at least one packet data frame comprises: 
 partitioning said packet data frame into a plurality of bytes;    for each byte appending an extra bit indicating that said corresponding respective byte comprises part of said packet data frame; and    for a last byte of said packet data frame, appending an extra bit indicating that said byte constitutes a last byte of said data frame.    
     
     
         8 . The method as claimed in step  1 , wherein said step of encoding at least one packet data frame comprises applying a consistent overhead byte stuffing algorithm to said data frame.  
     
     
         9 . The method as claimed in  claim 1 , wherein said step of encoding at least one packet data frame comprises: 
 applying a coding algorithm to said packet data frame which identifies a boundary of said data frame by appending a fixed number of bits to said data frame, irrespective of a size of said data frame.    
     
     
         10 . The method as claimed in  claim 1 , wherein said step of encoding at least one packet data frame comprises: 
 applying a coding algorithm to said data frame which identifies a boundary of said data frame by appending a fixed number of bits to said data frame, irrespective of a data content of said data frame.