Method of controlling access to a buffer and a device for temporary storage of data packets and an exchange with such a device

• US 5,546,389 A
• Filed: 07/12/1994
• Issued: 08/13/1996
• Est. Priority Date: 07/13/1993
• Status: Expired due to Term

• Current Assignee: Alcatel NV (Nokia Corporation), The Thing Tank
• Original Assignee: Alcatel NV (Nokia Corporation)
• Inventors: Schrodi, Karl, Willmann, Gert, Wippenbeck, Matthias
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US08/273,716
• Time in Patent Office: 763 Days
• Field of Search: 370/60, 370/94.1, 370/85.13, 370/85.14, 370/118, 370/17, 370/110.1, 370/85.6
• US Class Current: 370/412
• CPC Class Codes: G06F 13/18 based on priority control G06F13/1605 takes precedence
• CPC Class Codes: G06F 13/4226 with asynchronous protocol
• CPC Class Codes: G06F 5/10 having a sequence of storage locations each being individually accessible for both enqueue and dequeue operations, e.g. using random access memory G06F5/065 takes precedence
• CPC Class Codes: H04L 2012/5651 Priority, marking, classes
• CPC Class Codes: H04L 2012/5682 Threshold; Watermark
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

Data packets (D1, D2) each assigned to one of at least two priority classes (P1, P2) are stored in a buffer (MEM2) designed to hold data on a threshold value for each priority class wherein, instead of having the threshold fixed for each priority class whereby the data packets of the corresponding priority class will no longer be written into the buffer (MEM2) when the threshold is exceeded ("partial buffer sharing"), one or more thresholds are dynamically controlled. The current loss probability of the highest priority class (P1) is determined, and the threshold (MEM1) of the lowest priority class (P2) is then raised or lowered (REG1). This results in improved buffer utilization in applications which require a given loss probability for high priority classes, and calculation of a threshold value is no longer necessary.

Claims

1. An improved method of controlling access to a buffer in which data packets each assigned to one of at least two priority classes are stored together, comprising the steps of assigning each priority class a threshold value, the threshold value of a higher priority class being greater than or equal to that of a lower one, determining the priority class of a data packet arriving at the buffer and an occupancy level of the buffer at the time of arrival of the data packet, comparing the occupancy level with the threshold value assigned to the priority class of the data packet, and wherein based on this comparison, deciding as to whether the data packet is written into the buffer or discarded, wherein the improved method further comprises the step of determining traffic data and dynamically regulating a threshold value of at least one priority class based on a determination of traffic data.

2. The improved method as claimed in claim 1, further comprising the steps of determining and evaluating a loss probability of data packets of one or more priority classes, and to this end, determining and counting two events, namely that a data packet is written into the buffer and that a data packet is discarded.

3. The improved method as claimed in claim 1, further comprising the steps of quantitatively determining incoming traffic caused by data packets of one or more priority classes, and to this end, determining and counting the event that a data packet arrives at the buffer.

4. The improved method as claimed in claim 1, wherein said step of determining the occupancy level of the buffer is carried out at different times.

5. Improved apparatus for temporarily storing data packets each assigned to one of at least two priority classes, comprising a first memory device for storing data relating to a threshold value, a second memory device for said temporarily storing data packets, an access control device for receiving data packets and for providing said data packets to the second memory device and which apparatus, based on the data relating to a threshold value from the first memory device and based on data on an occupancy level of the second memory device, for deciding whether to write incoming data packets into the second memory device or to discard said data packets, and one or more readout devices for reading out data packets from the second memory device, wherein the improved apparatus further comprises a controller for determining traffic data and for dynamically changing the data relating to a threshold value in the first memory device based on determined traffic data.

6. The improved apparatus as claimed in claim 5, wherein the controller has an input for at least one timing signal.

7. The improved apparatus as claimed in claim 5, wherein the access control device provides at least one event signal which is determined from events including a time of arrival or a discarding of data packets, and wherein the controller has an input for at least one such event signal.

8. An exchange for a communications network for transporting data packets each assigned to one of at least two priority classes, comprising at least one apparatus for temporarily storing data packets which includes a first memory device for providing a threshold data signal having a magnitude indicative of a threshold value for each of said at least two priority classes, a second memory device which serves as a buffer, an access control device for receiving said data packets and for entering said data packets into the second memory device, said control device responsive to the threshold data signal from the first memory device and an occupancy data signal indicative of an occupancy level of the second memory device, for deciding whether to write incoming data packets into the second memory device or to discard said data packets, and one or more readout devices for retrieving data packets from the second memory device, wherein the magnitude of the threshold signal provided by the first memory device is changeable, and that the apparatus further comprises a controller which dynamically changes the magnitude of the threshold data signal provided by the first memory device according to a determination of traffic data.