Terminology in Service Level Management

Service Level Requirement - A customer requirement that the service (or some aspect of the service) must satisfy to to deliver a business objective.  This could be a functional requirement or a non-functional requirement.

Service Level Agreement - A document which sets out the service stipulations, such as measures and targets, between an IT Service Provider and their customer.  It will explicitly set out the responsibilities of all parties and the roles they must play.  It will be agreed between the IT Service Provider and customer and may form part of a contract between them.

Operational Level Agreement - A document which underpins the Service Level Agreements, internal to the IT Service Provider.  It forms an agreement between the customer facing part of the business and an internal department or team to set out the targets and measures for the support that department or team will give to a service.

Underpinning Contract - A contract between the IT Service Provider which underpins the Service Level Agreement with the customer.  The contract ensures that any aspect of the service supported by the third party supplier will be supported within the timescales of the Service Level Agreement.  For example if a service relies on the availability of network connectivity to a server, and that connectivity is supplied by a third party, then if the service is supported 24x7 the network connectivity must also be supported 24x7.

Service Improvement Plan - A formally agreed plan to implement improvements in the service delivered to the customer by the IT service Provider.