Transfer of messages in a multiplexed system

Abstract

A method and apparatus for transmitting variable length messages on a network in fixed length slots including the provision of a source identifier field in the header of each slot, the source identifier field including a code which is uniquely associated with the message to be transmitted. The fixed length slots are then transmitted on the network and reassembly of the slots by a reassembly machine is controlled in accordance with the identifier codes in the slot.

The claims defining the invention are as follows:  
     
       1. A method of transmitting variable length messages on a network from a source having a source address to a destination having a destination address, said method including the steps of: 
       segmenting each message into a plurality of fixed length slots including a first slot, continuing slots, and a last slot, each  of said slots including a header field which includes a source identifier field, which is substantially shorter than said destination address, and a message segment;  
       providing a source identifier code in the source identifier field, each source identifier code being uniquely associated with the message to be transmitted;  
       entering said destination address in the message segment of said first slot;  
       transmitting the slots on the network; and  
       controlling reassembly of slots at the destination in accordance with the source identifier code of slots received at the destination.  
     
     
       2. A method as claimed in  claim 1 , including the step of providing the a type field in the header field of each slot, and coding into the type field a first, second or third code representing a beginning of message, a continuation of message and an end of message respectively and controlling the reassembly of received slots at the destination in accordance with the first, second and third code. 
     
     
       3. A method as claimed in  claim 2 , wherein the method includes the step of storing message segments associated with a single message in a buffer at the destination. 
     
     
       4. A method as claimed in  claim 3 , wherein if said first code is detected at the destination, the source identifier code is inputted to a comparator and if said second code associated with a subsequently received slot is detected the source identifier thereof is also inputted to the comparator to check for a match, and if a match occurs the message segment of the subsequently received slot is stored in said buffer. 
     
     
       5. A method as claimed in  claim 4 , wherein if said third code is detected a reassembled message in the buffer is outputted from the buffer. 
     
     
       6. A method as claimed in  claim 2 , including the step of coding into the type field a fourth code representing a single segment message and if said fourth code is detected in a slot received at the destination, the message segment thereof is stored in a single segment buffer. 
     
     
       7. A method as claimed in  claim 5 , including the step of providing multiple comparators and buffers at the destination so as to enable simultaneous receipt of a plurality of messages each having its own source identifier code, the message segments of each message being stored in a single buffer. 
     
     
       8. A method as claimed in  claim 1 , including the step of concurrently transmitting two or more messages from the source to the destination on the network. 
     
     
       9. Apparatus for transmitting variable length messages on a network from a source having a source address to a destination having a destination address in fixed length slots, said apparatus including: 
       a segmentation machine for segmenting each message into a plurality of fixed length slots including a first slot, continuing slots, and a last slot, each of said slots including a header field which includes a source identifier field which is substantially shorter than said destination address, and a message segment,  
       coding means for providing a source identifier field including a source identifier code which is uniquely associated with the message to be transmitted,  
       means for entering said destination address in the message segment of said first slot, and  
       a reassembly machine located, in use, at the destination, said reassembly machine including control means for controlling reassembly of slots in accordance with the source identifier codes of the slots.  
     
     
       10. Apparatus as claimed in  claim 9 , wherein said coding means provides a type field in the header field of each slot and provides a first, second or third code representing a beginning of message, a continuation of message and an end of message, respectively, and wherein the control means is responsive to said first, second and third codes. 
     
     
       11. Apparatus as claimed in  claim 10 , wherein said reassembly machine includes detecting means for detecting in the header fields of the received slots the presence of the third code and for detecting a match between the destination address in the slot and the destination address of the destination, and wherein if there is an address match, the detecting means copies the source identifier code into a comparator means. 
     
     
       12. Apparatus as claimed in  claim 11 , wherein the reassembly machine includes a plurality of said comparator means to enable concurrent receipt of slots of different messages. 
     
     
       13. Apparatus as claimed in  claim 12 , including means inputting the source identifier codes of received slots to said plurality of comparator means to thereby enable matching of slots having the same source identifier codes. 
     
     
       14. Apparatus as claimed in  claim 13 , including a plurality of buffers for the message segments of the sots and a buffer selector circuit which selects a particular buffer for receipt of all message segments of slots having the same source identifier code whereby reassembled messages are stored in said buffers. 
     
     
       15. A method of transmitting variable length messages on a network from a source to a destination, said method including the steps of segmenting each message into a plurality of fixed length slots each of which slots includes a header field and a message segment, providing a source identifier field in the header field of each slot, said source identifier field including a source identifier code that is uniquely associated with the message to be transmitted, transmitting the slots on the network, controlling the reassembly of slots at the destination in accordance with the source identifier codes of the slots received at the destination, and providing a type field in the header field of each slot, and coding into the type field a code selected from a first code, a second code and a third code, respectively representing a beginning of message, a continuation of message or an end of message, and controlling the reassembly of received slots at the destination in accordance with said source identifier codes and the first code, the second code and the third code. 
     
     
       16. A method as claimed in  claim 15  wherein the message includes a destination address field that is checked for a match with an address associated with the destination, and wherein the address field is transmitted in the message segment of the first slot used to transmit the message. 
     
     
       17. A method as claimed in  claim 15  or  16  wherein the method includes the step of storing message segments associated with a single message in a buffer. 
     
     
       18. A method as claimed in  claim 17  wherein if said first code is detected at the destination, the source identifier code is inputted to a comparator and if the second code associated with a subsequently received slot is detected the source identifier thereof is also inputted to the comparator to check for a match, and if a match occurs the message segment of the subsequently received slot is stored in said buffer. 
     
     
       19. A method as claimed in  claim 18  wherein if said third code is detected the reassembled slots in the buffer are outputted from the buffer as a reassembled message. 
     
     
       20. A method as claimed in  claim 19  including the step of providing multiple comparators and buffers at the destination so as to enable simultaneous receipt of a plurality of messages each having its own source identifier code, the message segments of each message being stored in respective buffers. 
     
     
       21. A method as claimed in  claim 15  including the step of coding into the type field a fourth code representing a single segment message and if said fourth code is detected in a slot received at the destination, the message segment thereof is stored in a single segment buffer. 
     
     
       22. Apparatus for transmitting variable length messages on a network from a source to a destination in fixed length slots said apparatus including; 
       
         a segmentation machine for segmenting the messages into fixed length slots, each of said slots includes a header field and a message segment, said segmentation machine including coding means for providing a source identifier field in the header of each slot, the source identifier field being substantially shorter than any associated destination address, said source identifier field including a source identifier code that is uniquely associated with the message to be transmitted, and a reassembly machine located, in use, at the destination, said reassembly machine including control means for controlling reassembly of slot in accordance with the source identifier codes of the slots. 
       
     
     
       23. Apparatus as claimed in  claim 22  wherein said coding means provides a type field in the header field of each slot and provides a code selected from a first code, a second code and a third code, respectively representing a beginning of message, a continuation of message and an end of message, and wherein the control means is responsive to said source identifier codes and said first code, said second code and said third code. 
     
     
       24. Apparatus as claimed in  claim 22  or  23  wherein the message includes a destination address field and wherein the segmentation machine is arranged to transmit the destination address field in the message segment of the first slot of the message. 
     
     
       25. A method of transmitting variable length messages on a network from a source having a source address to a destination having a destination address, said method including the steps of: 
       
         segmenting each message into a plurality of fixed length slots including a first slot, continuing slots, and a last slot, each of said slots including a header field that includes a source identifier field, which is substantially shorter than said destination address, and a message segment;  
       
       
         providing a source identifier code in the source identifier field, said source identifier code being uniquely associated with the message to be transmitted;  
       
       
         transmitting the slots on the network; and  
       
       
         controlling reassembly of slots at the destination in accordance with the source identifier codes of the slots received at the destination. 
       
     
     
       26. Apparatus for transmitting variable length messages on a network from a source having a source address to a destination having a destination address in fixed length slots, said apparatus including: 
       
         a segmentation machine for segmenting each message into a plurality of fixed length slots including a first slot, continuing slots, and a last slot, each of said slots including a header field that includes a source identifier field that is substantially shorter than said destination address, and a message segment;  
       
       
         coding means for providing the source identifier field with a source identifier code that is uniquely associated with the message to be transmitted; and  
       
       
         a reassembly machine located, in use, at the destination, said reassembly machine including control means for controlling reassembly of slots in accordance with the source identifier codes of the slots. 
       
     
     
       27. A method for the connection oriented transfer of variable length messages (   20   )  on a network having a plurality of nodes  (   4   )  from a source node  (   42   )  having a source address  (   24   )  to a destination node  (   46   )  having a destination address  (   22   ) , said method including the steps of:    
         segmenting each message  (   20   )  into a plurality of fixed length slots  (   32   )  including a first slot, continuing slots and a last slot, each of said slots including a header field  (   34 ,  36 ,  38   )  and a message segment  (   40   );  
       
         transmitting the slots from the source node to the network; and  
       
       
         controlling reassembly of slots received at the destination node into the message on the basis of information in the header field;  
       
         a source identifier code  ( SI )  uniquely associated with the message to be transmitted from the source node being provided in a source identifier field in the header field of each of said slots; and    
       
         said reassembly of slots at the destination node being controlled in accordance with the source identifier code of slots received at the destination node. 
       
     
     
       28. A method as claimed in  claim 27  including the step of providing a type field (   36   )  in the header field of each slot, and coding into the type field a code representing an end of message  ( EOM )  and controlling the reassembly of received slots  (   32   )  at the destination node in accordance with said code.   
     
     
       29. A method as claimed in  claim 28  including the step of storing message segments (   40   )  associated with a single message in a buffer  (   77   )  at the destination node.   
     
     
       30. A method as claimed in  claim 29  wherein the source identifier code ( SI )  of the first slot received at the destination node is inputted to a comparator  (   82   )  and the source identifier code  ( SI )  of each subsequently received slot is also inputted to the comparator to check for a match, and if a match occurs, the message segment  (   40   )  of the subsequently received slot is stored in said buffer  (   77   ). 
     
     
       31. A method as claimed in  claim 30  wherein if one of said codes is detected, the reassembled message (   20   )  in the buffer  (   77   )  is outputted from the buffer  (   77   ). 
     
     
       32. A method as claimed in  claim 30  or  31  including the step of providing multiple comparators (   82   )  and buffers  (   77   )  at the destination node so as to enable simultaneous receipt of a plurality of messages  (   20   )  each having its own source identifier code  ( SI ) , the message segments  (   40   )  of each message  (   20   )  being stored in a single buffer  (   77   ). 
     
     
       33. Apparatus for the connection oriented transfer of variable length messages (   20   )  on a network having a plurality of nodes  (   4   )  from a source node  (   42   )  having a source address to a destination node  (   46   )  having a destination address in fixed length slots  (   32   ) , said apparatus including:    
         a segmentation machine  (   48   )  located, in use, at the source node, for segmenting each message  (   20   )  into a plurality of fixed length slots  (   32   )  including a first slot, continuing slots and a last slot, each of said slots including a header field  (   34 ,  36 ,  38   )  and a message segment; and    
         a reassembly machine  (   50   )  located, in use, at the destination node, said reassembly machine including control means for controlling reassembly of slots  (   32   )  in accordance with information in the header field;    
         coding means for providing a source identifier field  (   38   )  in the header field of each slot including a source identifier code  ( SI )  which is uniquely associated with the message  (   20   )  to be transmitted; and    
         the control means being adapted to control reassembly of the slots into the message in accordance with the source identifier codes  ( SI )  of the slots.   
     
     
       34. Apparatus as claimed in  claim 33 , wherein said coding means provides a type field (   36   )  in the header field of each slot and provides a further code representing an end of message  ( EOM )  and wherein the control means is operative to control reassembly of the slots to a reassembled message.   
     
     
       35. Apparatus as claimed in  claim 34  wherein the control means includes selector means (   70   )  for checking said further code in the header field of the slots and for inputting the source identifier codes  ( SI )  to comparator means  (   82   )  for checking for matches with subsequently received source identifier codes.   
     
     
       36. Apparatus as claimed in  claim 35 , wherein the reassembly machine (   50   )  includes a plurality of said comparator means  (   82   )  to enable concurrent receipt of slots of different messages.   
     
     
       37. Apparatus as claimed in  claim 36 , including means for inputting the source identifier codes ( SI )  of received slots to said plurality of comparator means  (   82   )  to thereby enable matching of slots having the same source identifier codes  ( SI ). 
     
     
       38. Apparatus as claimed in  claim 37 , including a plurality of buffers (   77   )  for the message segments of the slots and a buffer selector circuit which selects a particular buffer for receipt of all message segments of slots having the same source identifier code  ( SI )  whereby reassembled messages are stored in said buffers.   
     
     
       39. Apparatus as claimed in  claim 35  wherein, if the selector means (   70   )  detects a further code representing the end of a message  ( EOM ) , the control means operates to output a reassembled message from the buffer  (   77   )  which is associated with the source identifier code  ( SI )  of the slot containing said detected further code.