Frame multiplexing device

Abstract

A frame multiplexer includes a plurality of counters each of which is provided for each of the lines. A flow monitoring unit monitors frame flow of each line by referring to the counter of the line, and adds length of a passed frame to a value of the counter. A bandwidth managing unit cyclically selects one of the lines through which a frame is input, and subtracts a predetermined token value from a value of the counter of the selected line. An output control unit stores a frame passed through the flow monitoring unit in a queue buffer, and outputs the frame at an output rate of the frame multiplexer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a frame multiplexer according to embodiments of the present invention;

FIG. 2 is a block diagram of a flow monitoring unit;

FIG. 3 is a block diagram of a bandwidth managing unit;

FIG. 4 is a schematic for illustrating an operation by a line searching unit;

FIG. 5 is a flowchart of processings of monitoring a frame flow and updating a value of each counter performed by the flow monitoring unit;

FIG. 6 is a flowchart of processings of searching a line and updating a value of each counter performed by the bandwidth managing unit;

FIG. 7 is a block diagram of another bandwidth managing unit; and

FIG. 8 is a block diagram of a conventional frame multiplexer.

Claims

1. A frame multiplexer that multiplexes a plurality of frames of variable length input from a plurality of lines, the frame multiplexer comprising: a plurality of counters each of which is provided for each of the lines;a flow monitoring unit that adds a value representing a length of a frame that passes through the frame multiplexer to a value of a counter provided for a line from which the frame is input;a bandwidth managing unit that cyclically selects one of active lines that are lines from which frames are input into the frame multiplexer among the lines, and that subtracts a token value from a value of a counter of the active line selected; andan output control unit that stores the frame that has passed through the flow monitoring unit in a queue buffer, and that controls to output the frame at an output rate.

2. The frame multiplexer according to claim 1, wherein the flow monitoring unit includes a discard determining unit that discards, when a counter of a line exceeds a threshold predetermined for the line, a frame input from the line.

3. The frame multiplexer according to claim 1, wherein the bandwidth managing unit includes a timing managing unit that generates a trigger for selecting the active line in cycles that are determined by dividing the token value by a predetermined acceptable rate.

4. The frame multiplexer according to claim 3, wherein the bandwidth managing unit includes a line searching unit that refers to the counter to select one of the active lines upon receiving the trigger.

5. The frame multiplexer according to claim 4, wherein the bandwidth managing unit includes a plurality of selection counters for counting number of times for which each of the lines is selected by the line searching unit.

6. The frame multiplexer according to claim 2, wherein a size of traffic burst acceptable for each of the lines is set as the threshold.

7. The frame multiplexer according to claim 3, wherein the token value is larger than a value representing a minimum frame length of the frames.

8. The frame multiplexer according to claim 3, wherein the token value is equal to a value representing a maximum frame length of the frames.

9. The frame multiplexer according to claim 3, wherein the predetermined acceptable rate is equal to the output rate.

10. The frame multiplexer according to claim 1, wherein each of the counters includes a counter part having a plurality of bits indicating a counted value, and a sign bit indicating whether the counted value indicated by the counter part is positive.

11. The frame multiplexer according to claim 10, wherein the active lines are lines of which the counted value is positive.

12. The frame multiplexer according to claim 11, wherein the bandwidth managing unit searches one of the active lines using a weighted round robin method.

13. The frame multiplexer according to claim 12, wherein the bandwidth managing unit selects one of the active lines to which an identical weight is assigned in the weighted round robin method.

14. The frame multiplexer according to claim 12, wherein the bandwidth managing unit selects one of the active lines to which different weights are assigned in the weighted round robin method.