In the current competitive world, Quality of Service (QoS) is becoming, jointly with cost, a key parameter in selling and buying telecommunications services. At the same time, technology and liberalization trends are raising new types of concerns unknown with the Plain Old Telephony Services (POTS) using switched connections provided by a single monopoly supplier. As explained in other parts of ETSI EG 202 009 [i.1] and [i.2], the monitoring of a QoS commitment should refer to contractual values set either by governmental rules or in a mutual agreement between the provider and its customer. This is why achieving a SLA is more often perceived as the best means to meet specific QoS requirements while ensuring the optimal cost/quality ratio to the customer and the provider in a win-win perspective.

Nowadays, there are several standards describing QoS measurements but the questions of which indicators are to be monitored and which values they should meet are still open. ETSI EG 202 009-3 defines a framework for a Service Level Agreement between a customer and a supplier of ICT (Information and Communication Technology) Services. Such framework uses the service specific QoS metrics proposed in ETSI EG 202 009-2 [i.2] to evaluate the Quality of Service, while ETSI EG 202 009-1 [i.1] gives a methodology to identify the indicators relevant to the users.

The present document was written to make available to the providers and users of any kind of ICT services a common basis for mutual understanding about SLA. It aims to establish adequacy between the user's requirements in terms of Service Level Objectives (SLO) and the providers' offer with the associated QoS.