or service provider (e.g. CDN data centers of OTT service providers are also connected to the Internet via network providers). 9.4 SLA and QoS Regulation According to ITU-T E.860 [4], an SLA is a formal agreement between two or more entities that is reached after negotiating activity, with the scope of assessing service characteristics, responsibilities, and priorities of each part. The SLA may include state- ments about performance, tariffing and billing, service delivery, and compensations. On a national level, such commercial agreements are typically approved (initially) and mon- itored by NRAs. When one considers a multi-provider environment, there are also relationships between interrelated and interconnected providers. For example, one service provider that delivers a service to its own customers must use services provided by other providers (e.g. transit providers). With many service providers in the end-to-end chain, it may become much more complex to guarantee the QoS level as stated in the SLA. Therefore, in IP environments, due to the autonomous nature of different service providers, the SLA typically includes QoS in the access part and in the core network of the telecom operator which provides the access. Most SLAs are established between telecom operators which have local infrastructure and customers who use that infrastructure to access both Internet-based OTT services (i.e. data services) and spe- cialized services (provided via managed IP networks and offered with QoS guarantees). Typically, OTT service providers do not guarantee specific technical QoS to end-users because they offer their services on the principles of network neutrality over the open Internet network and thus they cannot have differentiated QoS provisioning regardless of service types (voice, video, messaging, Web, etc.). Because end-to-end communication typically may involve different networks (which are operated by different network providers), the standardized approach regarding QoS is one-stop responsibility [4], which is agr