A service is defined as an entity that provides a useful function to its users. 서비스의 몇 가지 예로는 CRM 애플리케이션, 온라인 뱅킹, 이메일 서비스 등이 있습니다. Some simpler forms of services are business functions that are supported by protocols such as DNS, LDAP, POP, or SMTP.