A concrete example of an SLA is a service level agreement for data centers. This SLA includes: the SLA must contain not only a description of the services to be provided and their expected service levels, but also measures to measure the services, the obligations and responsibilities of each party, the corrective measures or sanctions in case of violation and a protocol for adding and removing metrics. However, for critical services, customers should invest in third-party tools to automatically collect SLA performance data that provides an objective measure of performance. Any important contract that is not subject to an associated SLA (reviewed by a lawyer) is open to intentional or accidental misinterpretations. The SLA protects both parties in the agreement.