Transition refers to a computer science paradigm in the context of communication systems which describes the change of communication mechanisms, i.e., functions of a communication system, in particular, service and protocol components. In a transition, communication mechanisms within a system are replaced by functionally comparable mechanisms with the aim to ensure the highest possible quality, e.g., as captured by the quality of service.
Transitions enable communication systems to adapt to changing conditions during runtime. This change in conditions can, for example, be a rapid increase in the load on a certain service that may be caused, e.g., by large gatherings of people with mobile devices. A transition often impacts multiple mechanisms at different communication layers of a layered architecture.