Method for optimizing a digital transmission network operation through transient error monitoring and control and system for implementing said method

• US 6,222,822 B1
• Filed: 03/31/1997
• Issued: 04/24/2001
• Est. Priority Date: 04/23/1996
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Systems, Inc.
• Inventors: Spagnol, Victor, Massi, Patrick, Gerardin, Pierre
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US08/831,273
• Time in Patent Office: 1,485 Days
• Field of Search: 370/230, 370/229, 370/235, 370/252, 370/412, 370/413, 370/414, 370/415, 370/416, 370/417, 370/418, 370/419, 370/421, 370/428, 370/216, 370/217, 370/218, 370/242, 370/244, 370/250, 370/253, 370/463, 370/465, 395/265, 395/262, 395/200.55, 709/232, 709/235, 709/225
• US Class Current: 370/230
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• 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

Abstract

Method and system for tracking transient errors and controlling data traffic in a high speed packet switching network node. The traffic exits each node through a transmit queue per connection between end users.

The queue is monitored at both queue level through a threshold based mechanism (53) and a control of time activity mechanism (55). If trouble is detected by any one of these mechanisms, the queue packet admission is momentarily barred. To that end, a Line Resources Manager (LRM) provides queue threshold and time-out references and keeps monitoring the node global buffering memory available. If required, the LRM may also report to Network Management facilities for possible rerouting of the traffic.

Claims

1. For use in a high speed packet switching network node having a plurality of transmit adapters and a plurality of transmit queues created by assigning memory locations from a buffer pool, each transmit queue being assigned to one of the transmit adapters, a plurality of systems for controlling the admission of packets to the transmit queues, each system being associated with one of the transmit queues and comprising:

a queue threshold detector which generates a threshold-exceeded signal when the queue occupancy exceeds a predetermined threshold level;

a free buffer space detector for generating a low-buffer signal when the number of free memory locations in the buffer pool falls below a predetermined threshold;

a discard signal generator responsive to concurrent threshold-exceeded and low-buffer signals to generate a packet discard signal;

a port activity timer which generates a transmission time-out packet discard signal if the transmit queue requires more than a predetermined time to dequeue its contents following the start of a dequeuing operation; and

gate control logic responsive to packet discard signals from either said discard signal generator or said port activity time to block the enqueuing of a received packet into the transmit queue.

2. A system as described in claim 1 wherein the node further includes a line resources manager for controlling threshold levels and time-out values, said system further including event reporting logic for generating a report of threshold-exceeded signal events, low-buffer signal events and transmission time-outs for use by said line resources manager.

3. A system as described in claim 1 or 2 wherein said port activity timer further includes:

start logic for initiating timer operation at the start of a dequeuing operation;

reset logic responsive the occurrence of an end-of-buffer flag in a dequeued packet to reset the time;

a threshold detector for generating a time-threshold exceeded signal if the timer operation continues beyond a predetermined threshold interval; and

a signal generator for generating the transmission time-out packet discard signals in response to the time-threshold exceeded signal.

4. For use in a high speed packet switching network node having a plurality of transmit adapters and a plurality of transmit queues created by assigning memory locations from a buffer pool, each transmit queue being assigned to one of the transmit adapters, a method of controlling the admission of packets to a transmit queue comprising the steps of:

generating a first signal if the queue occupancy exceeds a predetermined threshold level;

generating a second signal if the number of free memory locations in the buffer pool falls below a predetermined threshold;

generating a third signal if the first signal and second signal occur concurrently;

generating a fourth signal if the transmit queue remains in a dequeuing state for greater than a predetermined period of time; and

denying admission of a new packet into the transmit queue in response to either the third signal or the fourth signal.

5. A method as set forth in claim 4 further including the step of reporting the occurrence of the first, second and fourth signals to a line resources manager to enable the manager to determine whether either of the threshold levels or the predetermined period of time should be altered.

6. A method as set forth in either claim 4 or 5 wherein the step of generating the fourth signal further comprises the steps of:

starting a count-up timer at the beginning of a packet dequeuing operation;

resetting the count-up timer in response to the detection of an end-of-buffer flag in the data being dequeued in the packet dequeuing operation; and

generating the fourth signal if the count exceeds a predetermined threshold count.