A service-level agreement (SLA) is a part of a service contract where a service is formally defined. Particular aspects of the service - scope, quality, responsibilities - are agreed between the service provider and the service user. A common feature of an SLA is a contracted delivery time (of the service or performance). As an example, Internet service providers and telcos will commonly include service level agreements within the terms of their contracts with customers to define the level(s) of service being sold in plain language terms. In this case the SLA will typically have a technical definition in terms of mean time between failures (MTBF), mean time to repair or mean time to recovery (MTTR); identifying which party is responsible for reporting faults or paying fees; responsibility for various data rates; throughput; jitter; or similar measurable details.