Working with the Junos Kernel

Kernel Communication and Generic Configuration (KCOM/GENCFG) is a Junos feature that allows applications to store their data as high-availability-enabled opaque blobs within the kernel space, and subsequently retrieve or change the data.

KCOM, or Kernel Communication, is the mechanism by which the Junos SDK functions perform these operations. The following figure shows how this works:

Kernel Communication and Generic Configuration

You can use GENCFG to store persistent application state in the kernel, to support interapplication communication, restart, and Routing Engine failover (GRES). Upon being re-spawned (for example, after a board switch-over) an application can request its data from the kernel space and reinitialize its internal states. The kernel does not know the contents of this data, but it can replicate the information onto the redundant or standby board if needed.

The GENCFG functionality is tied to a notification mechanism that applications can use. For a code example that illustrates how to use this feature, see Using the GENCFG Subsystem.

GENCFG is also used to implement reliable configuration download to the Multiservices PIC. A set of functions on the PIC allow the application data component to retrieve the data from the kernel. For details about this functionality, see Reliable Configuration Download.

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