IPGWx Congestion Management Options

There are two options for congestion management: either discard new messages (which is how MTP3 congestion is handled) or fail a connection.

The IPGWx application is designed to match MTP3 congestion procedures. With this option, the connection congestion status is not shared, and altering routing strategy based on congestion events is stopped. Instead, new messages destined to the congested connection are discarded, a new measurement is pegged, and response-method Transfer Controlled (TFC) messages are generated. This routing strategy only changes due to adapter state events.

A configurable timer (False Connection Congestion Timer ) sets the maximum amount of time that a connection can remain congested before it is failed. This timer is similar to the MTP3 False Link Congestion timer (T31).

This Match MTP3 Congestion Procedures option has several advantages: it is simple to implement, prevents mis-sequencing during connection congestion, and notifies the originator of a discarded MSU due to the congestion. The primary disadvantage is that MSUs may be discarded that otherwise may have been transmitted (which is the same as for link congestion).

The configurable UA Parameter Set (UAPS) Timer ‘False Connection Congestion Timer’ allows the user to specify the maximum amount of time an association can remain congested before it is taken out of service. The default setting for the timer is 3,000 ms, the minimum is 0 ms, and the maximum setting (enforced by the IPGWx L2 software, not by the chg-uaps command) is 30,000 ms.