# Prioritization of Communication Operations¶

oneCCL supports prioritization of communication operations that controls the order in which individual communication operations are executed. This allows to postpone execution of non-urgent operations to complete urgent operations earlier, which may be beneficial for many use cases.

The communication prioritization is controlled by priority value. Note that the priority must be a non-negative number with a higher number standing for a higher priority.

There are the following prioritization modes:

• None - default mode when all communication operations have the same priority.

• Direct - you explicitly specify priority using priority field in operation attribute.

• LIFO (Last In, First Out) - priority is implicitly increased on each operation call. In this case, you do not have to specify priority.

The prioritization mode is controlled by CCL_PRIORITY.