Service Level Agreements when Providing Synchronization Signals

One of the ways to organize the system of network synchronization in a digital telecommunication network is the use of synchronization signals received from a synchronization network of another operator. The operator providing synchronization signals service must guarantee the quality of these signals corresponding to the agreed class of connection and the dependability of their receipt. An effective and proven tool for providing such guarantees in the field of information and communication technologies is the Service Level Agreement (SLA) concluded between the provider and the customer of the service. It sets out the requirements for service quality indicators, the obligations of the parties, and, as a rule, financial responsibility of the service provider to meet the requirements. Such agreements are used in the provision of various services; they are considered in a number of international and Russian normative documents (ITU-T Recommendations, ETSI and TM Forum guidelines, GOST R). This paper describes the key aspects of SLA application and gives recommendations for their use when providing synchronization signals. In this case, the quality of the provided synchronization signals must meet the requirements for the agreed class of connection. It is recommended to use the availability as a dependability indicator, which determines the allowable total downtime for a given evaluation period (usually a month). A formula is proposed that expresses the dependence of the relative amount of financial compensation in case of a violation of the availability requirement on the severity of the violation and the required level of availability, which can be used as a technically justified guide in elaboration and evaluation of SLA conditions.