Traffic priority control system for a concentration-type ATM switch

• US 6,496,513 B1
• Filed: 11/02/1998
• Issued: 12/17/2002
• Est. Priority Date: 11/06/1997
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Takamichi, Toru
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): SPAFFORD, TIMOTHY J
• Application Number:
  US09/184,568
• Time in Patent Office: 1,506 Days
• Field of Search: 370/232, 370/389, 370/395.1, 370/398, 370/399, 370/419, 370/420, 370/473, 370/434
• US Class Current: 370/434
• CPC Class Codes: H04L 2012/5651 Priority, marking, classes
• CPC Class Codes: H04L 49/103 using a shared central buffer; using a shared memory
• CPC Class Codes: H04L 49/105 ATM switching elements
• CPC Class Codes: H04L 49/205 Quality of Service based
• CPC Class Codes: H04L 49/30 Peripheral units, e.g. input or output ports

Abstract

An ATM concentrator connects (m×n) input highways to n output highways and performs a full priority control. The ATM concentrator has output cell buffers for respective quality classes. Cells are read from the output buffers of the quality classes and the number of valid cells thereof is checked. A quality class c is determined with respect to which an accumulated value of the numbers of valid cells calculated successively from quality classes of higher priority is maximum within the total number of the output highways. The ATM concentrator outputs only cells of the highest priority class if the quality class c is the highest priority class. When the quality class c is not the highest priority class, the ATM concentrator writes valid cells of next priority class through the quality class c over cells that are not valid cells in the highest priority class.

Claims

1. An ATM concentrator having (m×

n) input highways and n output highways and established CL quality classes ranging from a quality class 1 of highest priority to a quality class CL of lowest priority, for performing a priority control for outputting cells of a quality class of relatively high priority in preference to cells of a quality class of relatively low priority, where each of m, n, CL is an integer of 2 or greater, comprising;

output cell buffers for the respective quality classes, associated respectively with said output highways;

a readout controller for checking a number of valid cells of cells read from said n output highways for each of said quality classes, determining a quality class c with respect to which an accumulated value of the numbers of valid cells calculated successively from quality classes of higher priority is maximum within a total number n of said output highways, generating a multiplexing control signal to instruct the output cell buffers of the quality class 1 to output n cells if the determined quality class c is the quality class 1, and checking highways corresponding to valid cells of cells read from the output cell buffers of the quality classes 2 through c and generating a multiplexing control signal to instruct writing of valid cells of the quality classes 2 through c over highways corresponding to cells which are not valid cells, of cells read from the output cell buffers of the quality class 1, if the determined quality class c is a quality class other than the quality class 1; and

a quality class multiplexer for outputting n cells read from the output cell buffers of the quality class 1 according to said multiplexing control signal or outputting a total of n cells produced by multiplexing the valid cells read from the output cell buffers of the quality classes 2 through c with n cells read from the output cell buffers of the quality class 1 based on said multiplexing control signal, to said n output highways;

whereby priority control of the quality class of relatively high priority and the quality class of relatively low priority can be carried out based on the multiplexing control signal generated by said readout controller.

2. An ATM concentrator according to claim 1, further comprising:

valid cell number tables associated with the respective quality classes, for holding numbers of counted valid cells at cell output positions of the output cell buffers;

said readout controller comprising means for determining a maximum number of quality classes to be multiplexed based on information of the numbers of counted valid cells read from said valid cell number tables.

3. An ATM concentrator according to claim 1, further comprising:

valid cell positional information tables associated with the respective quality classes, for holding valid cell positional information indicative of which highways valid cells are stored in at cell output positions of the output cell buffers of the quality classes;

said readout controller comprising means for determining which highways valid cells of the quality classes 2 through c are to be overwritten in, based on the valid cell positional information read from said valid cell positional information tables.

4. An ATM concentrator according to claim 1, further comprising:

sorting units, provided for respective quality classes, for connecting said (m×

n) input highways to said n output highways, selecting only valid cells of the quality classes and supplying the selected valid cells to said output cell buffer for the respective quality classes.

5. An ATM concentrator having (m×

n) input highways and n output highways and established CL quality classes ranging from a quality class 1 of highest priority to a quality class CL of lowest priority, for performing a priority control for outputting cells of a quality class of relatively high priority in preference to cells of a quality class of relatively low priority, where each of m, n, CL is an integer of 2 or greater, comprising;

output cell buffers for the respective quality classes, associated respectively with said output highways, said n output highways including a plurality of adjacent highways put together into g highway groups each composed of an equal number of highways, where g is a positive integer of n or less;

a readout controller for checking a number of groups containing valid cells read from said n output highways for each of said quality classes, determining a quality class c with respect to which an accumulated value of the numbers of groups containing valid cells calculated successively from quality classes of higher priority is maximum within a total number g of said groups, generating a multiplexing control signal to instruct the output cell buffers of the quality class 1 to output g groups read therefrom if the determined quality class c is the quality class 1, and checking groups containing valid cells, of groups from the output cell buffers of the quality classes greater than 1 and generating a multiplexing control signal to instruct writing of valid cells from the output cell buffers of the quality classes greater than 1 over groups which do not contain valid cells, of groups from the output cell buffers of the quality class 1, if the determined quality class c is a quality class other than the quality class 1; and

a quality class multiplexer for outputting valid cells of the g groups from the output cell buffers of the quality class 1 according to said multiplexing control signal or outputting valid cells of a total of g groups produced by multiplexing groups containing the valid cells read from the output cell buffers of the quality classes greater than 1 with g groups from the output cell buffers of the quality class 1 based on said multiplexing control signal, to said n output highways;

whereby priority control of the quality class of relatively high priority and the quality class of relatively low priority can be carried out based on the multiplexing control signal generated by said readout controller.

6. An ATM concentrator according to claim 5, further comprising:

valid group number tables associated with the respective quality classes, for holding total numbers of counted groups containing valid cells at cell output positions of the output cell buffers;

said readout controller comprising means for determining a maximum number of quality classes to be multiplexed based on information of the total numbers of counted groups read from said valid group number tables.

7. An ATM concentrator according to claim 5, further comprising:

valid group positional information tables associated with the respective quality classes, for holding valid group positional information indicative of which groups valid cells are stored in at cell output positions of the output cell buffers of the quality classes;

said readout controller comprising means for determining which output groups valid cells of the quality classes 2 through c are to be overwritten in, based on the valid group positional information read from said valid group positional information tables.

8. An ATM concentrator according to claim 5, further comprising:

sorting units, provided for respective quality classes, for connecting said (m×

n) input highways to said n output highways, selecting only valid cells of the quality classes and supplying the selected valid cells to said output cell buffers for the respective quality classes.