In ITIL service design, five aspects are considered to be defined during the design phase. These aspects are commonly called the "Five Aspects of Service Design”. They are as follows:
Service Solutions – Designing the services to deliver to customers. It involves defining the services' scope, requirements, functionality, and features.
Technology and Architecture –  Defining the technology,  infrastructure, and architecture that will support the delivery of IT services.
Management Information Systems and Tools – Choosing the systems and tools that will be used to manage and support the delivery of IT services.
Measurement and Metrics – Defining the metrics, measures, Key Performance Indicators (KPIs) , and Critical Success Factors (CSFs) that will be used to evaluate the performance and effectiveness of the services.
Processes – Designing the structured activities and workflows required to deliver and support IT services. Each process will have a defined trigger and pre-agreed inputs and outcomes.