Confirmed connections (class 2 and class 3) are maintained across switchovers. The following table describes what happens to a connection during connection-oriented switchover:
|
Connection type |
Description |
Connection status |
|
Transient connection |
Connection is being established or cleared |
Dropped on a switchover |
|
Connections that look active to the far end but idle to the local side |
A connection confirmation is returned but the checkpoint did not make it to backup, or a release was initiated but the far end did not receive it |
Cleared through the SCCP protocol-level inactivity timers |
The backup SCCP layer maintains the frozen status of each source local reference (SLR) assigned by the primary SCCP layer, so that the SLR is not re-used for the appropriate period of time after a switchover.
The following table describes what happens to messages during connection-oriented switchover:
|
Message is... |
Description |
The message... |
|
In transit at the time of a switchover |
Can be traveling in either direction |
May be lost |
|
Segmented and being reassembled at the time of a switchover |
Is incoming |
Will be dropped |
|
Segmented for class 2 connections |
The SCCP layer cannot detect that subsequent segments belong to a previous message. |
Is delivered to the application as a new message. Detection of the incomplete message and any recovery is the responsibility of the application. |
|
Segmented for class 3 connections |
The SCCP layer can detect and discard any subsequent segments received. |
|
Application inactivity control and connection auditing help synchronize connection information between primary and backup SCCP layers and applications.
|
Connection information mechanism |
Description |
|
Application inactivity control |
Complements the SCCP protocol level inactivity control by allowing the SCCP layer to detect that an active connection at the stack is no longer active at the application level. Application inactivity control must be enabled by a configuration option. |
|
Connection auditing |
Allows the application to retrieve a list of all active connections maintained by the SCCP layer. This is not recommended to replace application-level checkpointing of connection information, but can be useful when a backup application has failed and been restarted or as a general-purpose robustness mechanism. |
Refer to the Dialogic® NaturalAccess™ SCCP Layer Developer's Reference Manual for more information.