1. Feature Guide
  2. DSR Features and Functions
  3. Routing and Transaction Related Parameters in the DSR
  4. Congestion Control
  5. MP Overload Control

2.6.15.2 MP Overload Control

DSR MP Overload Control utilizes proven platform infrastructure to monitor the CPU utilization of each DSR MP and implement incremental load-shedding algorithms as engineered CPU utilization thresholds are exceeded. MP overload control provides DSR stability in the presence of extremely deteriorated network conditions, message loads that exceed the engineered capacity of a DSR MP, or improper configurations. It is important to note that MP overload control algorithm only monitors and acts on the CPU utilization of the DSR MP software functions (that is message & event handling), allowing a sufficient CPU budget for other non-critical (that is best effort) DSR MP functions. In this way, the load-shedding algorithms are not invoked when non-critical DSR MP functions consume more than their budgeted CPU when it has no impact on critical DSR MP functions. Message priority and Message color are used as input to the DSR’s message throttling and shedding decisions. In addition, exponential smoothing is applied to the CPU utilization samples in order to prevent the load-shedding algorithms from introducing more instability to an already degraded system

A DA-MP Danger of Congestion (DOC) threshold is less than the threshold set for DA-MP congestion level “1”. There is a DOC onset threshold, a DOC abatement threshold, and a DOC warning event.

When it has been determined that a system is actually in congestion, the request messages discarded are based on the priority of the message, the color of the message, and the user-configurable DA-MP Danger of Congestion discard policy. There are three user-configurable options:

  • Discard by color within priority (Y-P0, G-P0, Y-P1, G-P1, Y-P2, G-P2,……, Y-P15, G-P15).
  • Discard by priority within color (Y-P0, Y-P1, Y-P2,…….,Y-P15, G-P0, G-P1, G-P2,…….,G-P15).
  • Discard by priority only (P0, P1, P2,…..., P15).

The following elements are configurable for the DA-MP Overload Control feature:

  • Congestion Level 1 Discard Percentage – The percent below the DA-MP engineered ingress MPS that DA-MP overload control polices the total DA-MP ingress MPS when the DA-MP is in congestion level 1.
  • Congestion Level 2 Discard Percentage – The percent below the DA-MP engineered ingress MPS that DA-MP overload control polices the total DA-MP ingress MPS to when the DA-MP is in congestion level 2.
  • Congestion Level 3 Discard Percentage – The percent below the DA-MP engineered ingress MPS that DA-MP overload control polices the total DA-MP ingress MPS to when the DA-MP is in congestion level 3.
  • Congestion Discard Policy – The order of message priority and color-based traffic segments to consider when determining discard candidates for the application of treatment during DA-MP congestion processing.
  • Danger of Congestion Discard Percentage – The percent of total DA-MP ingress MPS above the DA-MP Engineered Ingress MPS that DA-MP Overload Control discards when the DA-MP is in danger of congestion.
  • Danger of Congestion Discard Policy – The order of Message Priority and Color-based traffic segments to consider when determining discard candidates for the application of treatment during DA-MP Danger of Congestion (DOC) processing. The following order is considered: Color within Priority, Priority within Color, and Priority Only.

As the DSR MP CPU utilization exceeds the engineered thresholds, the MP congestion level is updated and message load-shedding is performed by the DSR.