A service layer is used in computer and telecommunication systems to help delegate tasks. The service layer must be under a higher layer, because it is only made to assist in efforts; it is not made to perform tasks without instruction. When this layer receives a task, it contacts the layers, programs or functions responsible for getting the task done and tells them to turn on or off. Aside from communicating, this layer usually does not have any functions of its own. Work can be tough for an upper layer, so making this layer do the communicating eases some of the computing stress.
When a service layer is used, it cannot be used as a top layer that receives instructions from users. This is because this layer would not understand how to interpret the instructions, nor would it know how to fulfill them. It must be under another layer to properly work. One way to think of this layer is as an assistant that is good at fulfilling tasks and organizing workers but not at making decisions without being directly told what to do by management.
After the upper layer receives an instruction, it delegates it to the service layer under it. For example, the upper layer may be told to start sending data packets to a location. That layer will tell the service layer, which will contact all the programs and functions responsible for performing this task and tell them to start working.
While a service layer can tell other functions to work, the layer itself rarely has any of its own functions. It can organize other areas of the computer to properly fulfill a task, but it cannot do the task itself. This means this layer only serves as liaison between the upper layer and the functions.
The main reason for using a service layer is to make it easier for the upper layer to process requests and to take computational stress off the upper layer. Without a service layer, the upper layer would have to take tasks from the user, find the proper functions to perform the task, contact those functions and continue interpreting the user’s commands at the same time. This often is difficult and can lead to slow processing between layers. By adding a middle layer, the upper layer can focus on getting and moving tasks to best facilitate the user’s needs.