Since late 1980s SLAs have been used by fixed line telecom operators. SLAs are so widely used these days that larger organizations have many different SLAs existing within the company itself. Two different units in an organization script an SLA with one unit being the customer and another being the service provider. This practice helps to maintain the same quality of service amongst different units in the organization and also across multiple locations of the organization. This internal scripting of SLA also helps to compare the quality of service between an in-house department and an external service provider.