It is very normal to start planning a call center around the concept of DNIS, Groups, Agents and Skills.  Experience has taught us, however, that call center design needs to start with a more important concept.  Call Centers are performance oriented.  We measure the number of calls presented, the number calls answered, the number of calls abandoned, average talk time, the average time a caller is waiting in queue for service and any number of other key parameters.  We want to know call disposition, agent availability and how much time was used for lunch and breaks.   Is the staff sized appropriately for the volume of calls that are arriving?  Do we over flow excess call volume from one group to another group? How often do we do this and how long did callers waiting in the original queue before this happened?  Do we Interflow from one call center to another?  These parameters are all key characteristics of a call center and the very parameters we want to measure.   For this reason, call center design should begin with the actual report that we want call center to produce in order to verify our performance!  Lets construct the report we want to use to manage our business and from this document, we can best work backwards to creating the groups, agents, skills  and Queue messages.