Method for translating an ATM switch cell header

Abstract

The invention relates to a process for translating an ATM cell header for the routing thereof on a transmission highway of a communication network via an ATM switch. The header of the cell includes a first field VPI and a second field VCI, the first field VPI identifying a virtual path number and the second field VCI selecting a specified virtual channel within the virtual path. The process includes in]storing indirect addressing context page numbers in a first major table ( 3 ), storing context page numbers for the circuits in VP switching mode in a second major table ( 4 ), storing context page numbers ( 7 ) for the circuits in VC switching mode in indirect addressing ( 5 ) context pages ( 2 ), addressing the context pages ( 7 ) of circuits in VC switching mode by way of an indirect addressing ( 5 ) context page on the basis of the first major table ( 3 ) and of the field VCI, and addressing the context pages ( 9 ) of the VP switching mode on the basis of context page numbers contained in the second major table ( 4 ).

1. Process for translating an ATM cell header for the routing thereof on a transmission highway of a communication network via an ATM switch, the header of the cell comprising a first field VPI and a second field VCI, the first field VPI and a second field VCI,  the first field VPI identifying a virtual path (VP) number and the second field VCI selecting a specified virtual channel (VC) within the virtual path, said process comprising:
 storing indirect addressing context page numbers for virtual circuits in VC switching mode in a first major table,  
 storing context page numbers for virtual circuits in VP switching mode in a second major table,  
 storing context page numbers for virtual circuits in VC switching mode in indirect addressing context pages,  
 addressing the context pages of virtual circuits in VC switching mode by way of an indirect addressing context page on the basis of the first major table and of the field VCI, and  
 addressing the context pages of the VP switching mode on the basis of context page numbers contained in the second major table, wherein all context pages have a substantially identical size.  
 
     
     
       2. Process according to  claim 1 , characterized in that for the addressing of a context page in VC switching mode, the first field VPI comprises a first area of bits VPI 1  and a second area of bits VPI 2 , which areas are reserved for the addressing of the first major table ( 3 ) for switching in VC mode, and a third area of bits VPI 3  which is reserved for the addressing of an indirect addressing context page ( 5 ) and in that the second field VPI  VCI comprises a first area of bits VCI 1  which is reserved together with the third area of bits VPI 3  for addressing inside the indirect addressing context pages as well as a second area of bits VCI 4 . 
     
     
       3. Process according to  claim 2 , characterized in that it consists in also using, for the addressing of a context page in VP switching mode, the first area of bits VPI 1  for the addressing of words inside the second major table ( 4 ) for switching in VP mode and a second area of bits VPI 4  which is reserved as indirect addressing word for the addressing of a context inside a context page. 
     
     
       4. The process of  claim 1 , wherein a size of the VP mode context page and the VC mode context page is constant and is determined by
   T VPC =T VCC =2 M    
 
       where T VPC  is the size of the VP mode context pages,
 where T VCC  is the size of the VC mode context pages, and  
 M is an integer that is independent of the size of the VP mode and VC mode context pages.  
 
     
     
       5. The process of  claim 2 , wherein a size of the VP mode context page and the VC mode context page is constant and is determined by
   T VPC =T VCC =2 M    
 
       where T VPC  is the size of the VP mode context pages,
 where T VCC  is the size of the VC mode context pages, and  
 M is an integer that is independent of the size of the VP mode and VC mode context pages.  
 
     
     
       6. The process of  claim 3 , wherein a size of the VP mode context page and the VC mode context page is constant and is determined by
   T VPC =T VCC =2 M    
 
       where T VPC  is the size of the VP mode context pages,
 where T VCC  is the size of the VC mode context pages, and  
 M is an integer that is independent of the size of the VP mode and VC mode context pages.  
 
     
     
       7. A digital data switch for translating and routing an asynchronous transfer mode (ATM) cell having a header that includes a VPI field identifying a virtual path number, and a VCI field identifying a virtual channel within the virtual path, said switch comprising:
 a first major table configured to store indexation fields relative to virtual channel (VC) mode circuits;  
 a second major table configured to store indexation fields relative to virtual path (VP) mode circuits; and  
 a general purpose page block configured to store an indirect addressing context page configured to catalog and address VC mode and VP mode context pages stored in the general purpose page block,  
 wherein, in a VC switching mode, the VC context pages are addressed by way of the indirect addressing context page on the basis of the first major table and the VCI field,  
 wherein, in a VP switching mode, the VP context pages are addressed on the basis of context page numbers contained in the second major table; and wherein all context pages have a substantially identical size.  
 
     
     
       8. The switch of  claim 7 , wherein a size of the VP mode context page and the VC mode context page is constant and is determined by
   T VPC =T VCC =2 M    
 
       where T VPC  is the size of the VP mode context pages,
 where T VCC  is the size of the VC mode context pages, and  
 M is an integer that is independent of the size of the VP mode and VC mode context pages.  
 
     
     
       9. A digital data switch for translating and routing an asynchronous transfer mode (ATM) cell having a header that includes a VPI field identifying a virtual path number, and a VCI field identifying a virtual channel number within the virtual path, said switch comprising:
 means for storing indexation fields relative to virtual channel (VC) mode circuits;  
 means for storing indexation fields relative to virtual path (VP) mode circuits; and  
 means for cataloging and addressing VC mode and VP mode context pages stored in a general purpose page block,  
 wherein, in a VC switching mode, the VC context pages are addressed by way of the means for cataloging and addressing on the basis of the means for storing indexation fields relative to virtual channel (VC) mode circuits and the VCI field,  
 wherein, in a VP switching mode, the VP context pages are addressed on the basis of context page numbers contained in the means for storing indexation fields relative to virtual path (VP) mode circuits; and wherein all context pages have a substantially identical size.  
 
     
     
       10. A computer-readable medium for use in translating and routing an asynchronous transfer mode (ATM) cell, the cell having a header that includes a virtual path identification field (VPI) field and a virtual channel identification (VCI) field, the computer-readable medium comprising:
   a first table configured to store data for identifying one or more indirect addressing context pages;        a virtual channel context page configured to store a context area M 3 ; and        an indirect addressing context page configured to store an address M 2  to identify the virtual channel context page,        wherein, in a virtual channel mode, the first table is used to locate a pointer M 1  by using portions of the VPI field; the indirect addressing context page is located by using the pointer M 1 ; the address M 2  is located by using the pointer M 1 , a portion of the VPI field, and a portion of the VCI field; and the context area M 3  is located by using the address M 2  and a portion of the VCI field.     
     
     
       11. The computer-readable medium of  claim 10 , wherein the pointer M 1  in the first table for switching in the virtual channel mode is located by using a first portion of the VPI field (VPI 1 ) and a second portion of the VPI field (VPI 2 ). 
     
     
       12. The computer-readable medium of  claim 11 , wherein the pointer M 1  is located at a cross section between a row and a column, the row identified by VPI 1  and the column identified by VPI 2 . 
     
     
       13. The computer- readable medium of    claim 11   , wherein the indirect addressing context page is found by the pointer M 1  acting as a pointer to a location in a block of context pages where the indirect addressing context page resides, the indirect addressing context page cataloging addresses of context pages in the block of context pages.   
     
     
       14. The computer- readable medium of    claim 13   , wherein the address M 2  of the virtual channel context page is located by using the pointer M 1 , a third portion of the VPI field  ( VPI 3   ) , and a first portion of the VCI field  ( VCI 1   ). 
     
     
       15. The computer- readable medium of    claim 14   , wherein the address M 2  is located at a cross section between a row and a column in the indirect addressing page found by the pointer M 1 , the row being determined by appending to the pointer M 1  the content of the third portion of the VPI field  ( VPI 3   ) , the column being determined by the first portion of the VCI field  ( VCI 1   ). 
     
     
       16. The computer- readable medium of    claim 14   , wherein the context area M 3  of the virtual channel context page is located by using the address M 2  and a second portion of the VCI field  ( VCI 4   ). 
     
     
       17. The computer- readable medium of    claim 16   , wherein the context area M 3  is located by appending the content of VCI 4  to the address M 2 .   
     
     
       18. The computer- readable medium of    claim 16    further comprising:      a second table configured to store data for identifying one or more virtual path context pages; and        a virtual path context page configured to store a context area M 5 ;        wherein, in a virtual path mode, the second table contains an address M 4  that is located by using a portion of the VPI field; the virtual path context page is located using the address M 4 ; and the context area M 5  is located by using the address M 4  and another portion of the VPI field.     
     
     
       19. The computer- readable medium of    claim 18   , wherein the address M 4  in the second table for switching in the virtual path mode is located by using the first portion of the VPI field  ( VPI 1   ). 
     
     
       20. The computer- readable medium of    claim 19   , wherein the context area M 5  is located by using the address M 4  and a fourth portion of the VPI field  ( VPI 4   ). 
     
     
       21. The computer- readable medium of    claim 20   , wherein the virtual path identification, in the virtual channel mode, is formed from portions VPI 0 , VPI 1 , VPI 2 , and VPI 3 , and wherein the virtual path identification, in the virtual path mode, is formed from portions VPI 0 , VPI 1 , and VPI 4 , the bit length of the portion VPI 4  being equivalent to the sum of the bit lengths of the portions VPI 2  and VPI 3 , wherein the virtual channel identifier is formed from portions VCI 0 , VCI 1 , and VCI 4 .   
     
     
       22. The computer- readable medium of    claim 18   , wherein a size of the virtual path context pages and the virtual channel context pages is constant.   
     
     
       23. The computer- readable medium of    claim 18   , wherein all the context pages have a substantially similar size.   
     
     
       24. The computer- readable medium of    claim 10   , wherein all the context pages have a substantially similar size.   
     
     
       25. The computer- readable medium of    claim 10   , wherein the size of one of the context pages is substantially similar to the size of another of the context pages.   
     
     
       26. The computer- readable medium of    claim 25   , wherein the pointer M 1  in the first table for switching in the virtual channel mode is located by using a first portion of the VPI field  ( VPI 1   )  and a second portion of the VPI field  ( VPI 2   ). 
     
     
       27. The computer- readable medium of    claim 26   , wherein the pointer M 1  is located at a cross section between a row and a column, the row identified by VPI 1  and the column identified by VPI 2 .   
     
     
       28. The computer- readable medium of    claim 26   , wherein the indirect addressing context page is found by the pointer M 1  acting as a pointer to a location in a block of context pages where the indirect addressing context page resides, the indirect addressing context page cataloging addresses of context pages in the block of context pages.   
     
     
       29. The computer- readable medium of    claim 28   , wherein the address M 2  of the virtual channel context page is located by using the pointer M 1 , a third portion of the VPI field  ( VPI 3   ) , and a first portion of the VCI field  ( VCI 1   ). 
     
     
       30. The computer- readable medium of    claim 29   , wherein the address M 2  is located at a cross section between a row and a column in the indirect addressing page found by the pointer M 1 , the row being determined by appending to the pointer M 1  the content of the third portion of the VPI field  ( VPI 3   ) , the column being determined by the first portion of the VCI field  ( VCI 1   ). 
     
     
       31. The computer- readable medium of    claim 29   , wherein the context area M 3  of the virtual channel context page is located by using the address M 2  and a second portion of the VCI field  ( VCI 4   ). 
     
     
       32. The computer- readable medium of    claim 31   , wherein the context area M 3  is located by appending the content of VCI 4  to the address M 2 .   
     
     
       33. The computer- readable medium of    claim 31    further comprising:      a second table configured to store data for identifying one or more virtual path context pages; and        a virtual path context page configured to store a context area M 5 ;        wherein, in a virtual path mode, the second table contains an address M 4  that is located by using a portion of the VPI field; the virtual path context page is located using the address M 4 ; and the context area M 5  is located by using the address M 4  and another portion of the VPI field.     
     
     
       34. The computer- readable medium of    claim 33   , wherein the address M 4  in the second table for switching in the virtual path mode is located by using the first portion of the VPI field  ( VPI 1   ). 
     
     
       35. The computer- readable medium of    claim 34   , wherein the context area M 5  is located by using the address M 4  and a fourth portion of the VPI field  ( VPI 4   ). 
     
     
       36. A computer- readable medium for use in translating and routing an asynchronous transfer mode  ( ATM )  cell, the cell having a header that includes a virtual path identification field  ( VPI )  field and a virtual channel identification  ( VCI )  field, the computer - readable medium comprising:      a virtual channel context page configured to store a first context area that is found in a VC switching mode by appending a first portion of the VCI field  ( VCI 4   )  to a first address that is found from an indirect addressing context page, wherein data of the first context area is used to translate the ATM cell in a VC switching mode; and        a virtual path context page configured to store a second context area that is found in a VP switching mode by appending a first portion of the VPI field  ( VPI 4   )  to a second address that is found by using a second portion of the VPI field  ( VPI 1   )  to index into a first table, wherein data of the second context area is used to translate the ATM cell in a VP switching mode.     
     
     
       37. The computer- readable medium of    claim 36   , wherein the size of the virtual channel context page and the size of the virtual path context page are constant.   
     
     
       38. The computer- readable medium of    claim 36   , wherein the size of the virtual channel context page is equivalent to the product of  2  raised to the power of M and  2  raised to the power of Np 4 , M being an integer which is independent of the size of the virtual channel context page and the size of the virtual path context page, Np 4  being the number of bits associated with a portion of the virtual path identification  ( VPI 4   ). 
     
     
       39. The computer- readable medium of    claim 38   , wherein the size of the virtual channel context page is equivalent to the product of  2  raised to the power of M and  2  raised to the power of Nc 4 , Nc 4  being the number of bits associated with a portion of the virtual channel identification  ( VCI 4   ). 
     
     
       40. The computer- readable medium of    claim 39   , wherein the size of an indirect addressing context page is equivalent to the product of  2  raised to the power of Np 3  and  2  raised to the power of Nc 1 , Np 3  being the number of bits associated with a portion of the virtual path identification  ( VPI 3   ) , Nc 1  being the number of bits associated with a portion of the virtual channel identification  ( VCI 1   ). 
     
     
       41. The computer- readable medium of    claim 40   , wherein the size of a table for facilitating the virtual channel mode is equivalent to the product of  2  raised to the power of Np 1  and  2  raised to the power of Np 2 , Np 1  being the number of bits associated with a portion of the virtual path identification  ( VPI 1   ) , Np 2  being the number of bits associated with a portion of the virtual path identification  ( VPI 2   ). 
     
     
       42. The computer- readable medium of    claim 40   , wherein the size of a table for facilitating the virtual path mode is equivalent to  2  raised to the power of Np 1 , Np 1  being the number of bits associated with a portion of the virtual path identification  ( VPI 1   ). 
     
     
       43. The computer- readable medium of    claim 36   , wherein, in the VC switching mode, the indirect addressing context page is located by using portions VPI 1  and VPI 2  of the VPI field to index into a second table.   
     
     
       44. The computer- readable medium of    claim 43   , wherein the size of the virtual channel context page and the size of the virtual path context page are constant.   
     
     
       45. The computer- readable medium of    claim 43   , wherein the size of one of the context pages is substantially similar to the size of another of the context pages.   
     
     
       46. A method for translating an ATM cell header for the routing thereof on a transmission highway of a communication network via an ATM switch, the header of the cell comprising a first field VPI and a second field VCI, the first field VPI identifying a virtual path ( VP )  number and the second field VCI selecting a specified virtual channel  ( VC )  within the virtual path, said process comprising:      storing indirect addressing context page numbers for virtual circuits in VC switching mode in a first major table,        storing context page numbers for virtual circuits in VP switching mode in a second major table,        storing context page numbers for virtual circuits in VC switching mode in indirect addressing context pages,        addressing the context pages of virtual circuits in VC switching mode by way of an indirect addressing context page on the basis of the first major table and of the field VCI, and        addressing the context pages of the VP switching mode on the basis of context page numbers contained in the second major table, wherein the size of one of the context pages is substantially similar to the size of another of the context pages.     
     
     
       47. The method of  claim 46 , characterized in that for the addressing of a context page in VC switching mode, the first field VPI comprises a first area of bits VPI 1  and a second area of bits VPI 2 , which areas are reserved for the addressing of the first major table (   3   )  for switching in VC mode, and a third area of bits VPI 3  which is reserved for the addressing of an indirect addressing context page  (   5   )  and in that the second field VPI comprises a first area of bits VCI 1  which is reserved together with the third area of bits VPI 3  for addressing inside the indirect addressing context pages as well as a second area of bits VCI 4 .   
     
     
       48. The method of  claim 47 , characterized in that it consists in also using, for the addressing of a context page in VP switching mode, the first area of bits VPI 1  for the addressing of words inside the second major table (   4   )  for switching in VP mode and a second area of bits VPI 4  which is reserved as indirect addressing word for the addressing of a context inside a context page.   
     
     
       49. A digital data switch for translating and routing an asynchronous transfer mode ( ATM )  cell having a header that includes a VPI field identifying a virtual path number and a VCI field identifying a virtual channel within the virtual path, said switch comprising:      a first major table configured to store indexation fields relative to virtual channel  ( VC )  mode circuits;        a second major table configured to store indexation fields relative to virtual path  ( VP )  mode circuits; and        a general purpose page block to store an indirect addressing context page configured to catalog and address VC mode context pages stored in the general purpose page block,        wherein, in a VC switching mode, the VC context pages are addressed by way of the indirect addressing context page on the basis of the first major table and the VCI field,        wherein, in a VP switching mode, VP context pages are addressed on the basis of context page numbers contained in the second major table, and        wherein the size of one of the context pages is substantially similar to the size of another of the context pages.     
     
     
       50. The switch of  claim 49 , wherein a VC switching mode, the first field VPI comprises a first area of bits VPI 1  and a second area of bits VPI 2 , which areas are reserved for the addressing of the first major table for switching in VC mode, and a third area of bits VPI 3  which is reserved for the addressing of an indirect addressing context page; and the second field VCI comprises a first area of bits VCI 1  which is reserved together with the third area of bits VPI 3  for addressing inside the indirect addressing context pages as well as a second area of bits VCI 4 . 
     
     
       51. The switch of  claim 50 , wherein in a VP switching mode, the first area of bits VPI 1  is reserved for the addressing of words inside the second major table for switching in VP mode and the second area of bits VPI 4  is reserved as an indirect addressing word for the addressing of a context inside a context page. 
     
     
       52. A digital data switch for translating and routing an asynchronous transfer mode ( ATM )  cell having a header that includes a VPI field identifying a virtual path number and a VCI field identifying a virtual channel within the virtual path, said switch comprising:      means for storing indexation fields relative to virtual channel  ( VC )  mode circuits;        means for storing indexation fields relative to virtual path  ( VP )  mode circuits; and        means for cataloging and addressing VC mode context pages stored in the general purpose page block,        wherein, in a VC switching mode, the VC context pages are addressed by way of the means for cataloging and addressing on the basis of the means for storing indexation fields relative to virtual channel  ( VC )  mode circuits and the VCI field,        wherein, in a VP switching mode, VP context pages are addressed on the basis of context page numbers contained in the means for storing indexation fields relative to virtual path  ( VP )  mode circuits, and        wherein the size of one of the context pages is substantially similar to the size of another of the context pages.     
     
     
       53. The switch of  claim 52 , wherein in a VC switching mode, the first field VPI comprises a first area of bits VPI 1  and a second area of bits VPI 2 , which areas are reserved for the addressing of the means for storing indexation fields relative to virtual channel ( VC )  mode circuits, and a third area of bits VPI 3  which is reserved for the addressing of the means for cataloging and addressing VC mode context pages stored in the general purpose page block; and the second field VCI comprises a first area of bits VCI 1  which is reserved together with the third area of bits VPI 3  for addressing inside the means for cataloging and addressing VC mode context pages stored in the general purpose page block as well as a second area of bits VCI 4 .   
     
     
       54. The switch of  claim 53 , wherein in a VP switching mode, the first area of bits VPI 1  is reserved for the addressing of words inside the means for storing indexation fields relative to virtual path ( VP )  mode circuits and the second area of bits VPI 4  is reserved as an indirect addressing word for the addressing of a context inside a context page.   
     
     
       55. A computer- readable medium for use in translating and routing an asynchronous transfer mode  ( ATM )  cell having a header that includes a VPI field identifying a virtual path number and a VCI field identifying a virtual channel number within the virtual path, said computer - readable medium comprising:      a first major table configured to store indexation fields relative to virtual channel  ( VC )  mode circuits;        a second major table configured to store indexation fields relative to virtual path  ( VP )  mode circuits; and        a general purpose page block to store an indirect addressing context page configured to catalog and address VC mode context pages stored in the general purpose page block,        wherein, in a VC switching mode, the VC context pages are addressed by way of the indirect addressing context page on the basis of the first major table and the VCI field,        wherein, in a VP switching mode, VP context pages are addressed on the basis of context page numbers contained in the second major table, and        wherein the size of one of the context pages is substantially similar to the size of another of the context pages.     
     
     
       56. The computer- readable medium of    claim 55   , wherein in a VC switching mode, the first field VPI comprises a first area of bits VPI 1  and a second area of bits VPI 2 , which areas are reserved for the addressing of the first major table for switching in VC mode, and a third area of bits VPI 3  which is reserved for the addressing of an indirect addressing context page; and the second field VCI comprises a first area of bits VCI 1  which is reserved together with the third area of bits VPI 3  for addressing inside the indirect addressing context pages as well as a second area of bits VCI 4 .   
     
     
       57. The computer- readable medium of    claim 56   , wherein in a VP switching mode, the first area of bits VPI 1  is reserved for the addressing of words inside the second major table for switching in VP mode and the second area of bits VPI 4  is reserved as an indirect addressing word for the addressing of a context inside a context page.