Systems and methods for dropping data using a drop profile

• US 8,335,158 B2
• Filed: 05/14/2010
• Issued: 12/18/2012
• Est. Priority Date: 01/25/2002
• Status: Active Grant

• Current Assignee: Juniper Networks Incorporated
• Original Assignee: Juniper Networks Incorporated
• Inventors: Sindhu, Pradeep, Basu, Debashis, Boddu, Jayabharat, Godbole, Avanindra
• Primary Examiner(s): Zhu, Bo Hui A
• Application Number:
  US12/780,607
• Publication Number:
  US 20100220590A1
• Time in Patent Office: 949 Days
• Field of Search: 370/230, 370/230.1, 370/231, 370/232, 370/233, 370/234, 370/235, 370/412, 370/413, 370/414, 370/415, 370/416, 370/417, 370/418
• US Class Current: 370/231
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/23 Bit dropping
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames
• CPC Class Codes: H04L 47/326 with random discard, e.g. random early discard [RED]
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/9078 using an external memory or storage device

Abstract

A system selectively drops data from queues. The system includes a drop table that stores drop probabilities. The system selects one of the queues to examine and generates an index into the drop table to identify one of the drop probabilities for the examined queue. The system then determines whether to drop data from the examined queue based on the identified drop probability.

Claims

1. A system for selectively dropping data from a queue, the system comprising:

a plurality of queues to temporarily store data; and

a drop engine to select one of the queues to examine, the drop engine comprising;

a drop table to store a plurality of drop probabilities,

indexing logic to;

generate an index into the drop table based on an amount of memory used by the examined queue, and

identify one of the drop probabilities in the drop table using the generated index, and

drop decision logic to;

determine whether to drop data, from a head of the examined queue, based on the identified drop probability, and

determine to drop the data when a ratio of the amount of memory being used by the examined queue to a maximum of a static amount of memory allocated to the examined queue and an amount of memory that should be made available to the examined queue is greater than one.

2. The system of claim 1, where the drop table includes:

a plurality of drop tables, each of which is configured to store a plurality of drop probabilities.

3. The system of claim 2, where the indexing logic is further configured to:

select one of the drop tables, and

identify one of the drop probabilities in the selected drop table using the generated index.

4. The system of claim 3, where, when selecting one of the drop tables, the indexing logic is configured to:

use one or more attributes of the data to select among the drop tables.

5. The system of claim 1, where the drop decision logic is configured to:

determine whether to drop data from the examined queue based on the identified drop probability and other information including information extracted from the data, where the information includes an attribute that indicates that the data should not be dropped.

6. The system of claim 1, where the drop probability is based on the ratio of the amount of memory being used by the examined queue to the maximum of a static amount of memory allocated to the examined queue and the amount of memory that should be made available to the examined queue.

7. The system of claim 1, where the drop decision logic is configured to:

determine not to drop the data when the index generated by the indexing logic is below an index threshold.

8. A method of selectively dropping data from each of a plurality of queues that temporarily store data, the method comprising:

selecting one of the queues to examine;

providing a drop table associated with the selected queue, the drop table storing a plurality of drop probabilities;

determining an amount of memory used by the selected queue;

generating an index into the drop table based on the amount of memory;

identifying one of the drop probabilities in the drop table using the generated index;

determining whether to drop data, from a head of the selected queue, based on the identified drop probability; and

determining to drop the data when a ratio of the amount of memory being used by the selected queue to a maximum of a static amount of memory allocated to the selected queue and an amount of memory that should be made available to the selected queue is greater than one.

9. The method of claim 8, where the drop table includes a plurality of drop tables, each of which is configured to store a plurality of drop probabilities;

and

where the method further comprises;

selecting one of the drop tables, and

identifying one of the drop probabilities in the selected drop table using the generated index.

10. The method of claim 9, where the selecting one of the drop tables includes:

using one or more attributes of the data to select among the drop tables.

11. The method of claim 8, where the determining whether to drop data from the selected queue includes:

generating a random number,

comparing the identified drop probability to the random number, and

generating a drop decision based on a result of the comparison.

12. The method of claim 8, where the determining whether to drop data includes:

determining whether to drop the data from the selected queue based on the identified drop probability and other information including information extracted from the data.

13. The method of claim 8, further comprising:

establishing an index threshold; and

where the determining whether to drop data includes;

determining not to drop the data when the index is below the index threshold.

14. The method of claim 8, where the drop probability is based on the ratio of the amount of memory being used by the selected queue to the maximum of the static amount of memory allocated to the selected queue and the amount of memory that should be made available to the selected queue.

15. A system comprising:

a plurality of queues to temporarily store data; and

a drop engine to select one of the queues to examine, the drop engine comprising;

a drop table to store a plurality of drop probabilities,

indexing logic to generate an index into the drop table, based on an amount of memory used by the selected queue, to identify one of the drop probabilities, and

drop decision logic to;

determine whether to drop data from a head of the selected queue based on the identified drop probability, and

determine to drop the data when a ratio of the amount of memory being used by the selected queue to a maximum of a static amount of memory allocated to the selected queue and an amount of memory that should be made available to the selected queue is greater than one.

16. The system of claim 15, where the drop table includes:

a plurality of drop tables, each of which is configured to store a plurality of drop probabilities.

17. The system of claim 16, where the drop decision logic includes:

a random number generator configured to generate a random number; and

a comparator configured to;

compare the identified drop probability to the random number, and

generate a drop decision based on a result of the comparison.

18. The system of claim 17, where the random number generator has a same number of bits as a number of bits in the identified drop probability.

19. The system of claim 17, where the random number generator has a greater number of bits than a number of bits in the identified drop probability.