  A Service Level Agreement (SLA) is a formal contract between a service
provider and a consumer, representing a crucial instrument to define, manage,
and maintain relationships between these two parties. The SLA's ability to
define the Quality of Service (QoS) expectations, standards, and accountability
helps to deliver high-quality services and increase client confidence in
disparate application domains, such as Cloud computing and the Internet of
Things. An open research direction in this context is related to the possible
integration of new metrics to address the security and privacy aspects of
services, thus providing protection of sensitive information, mitigating risks,
and building trust. This survey paper identifies state of the art covering
concepts, approaches, and open problems of SLA management with a distinctive
and original focus on the recent development of Security SLA (SecSLA). It
contributes by carrying out a comprehensive review and covering the gap between
the analyses proposed in existing surveys and the most recent literature on
this topic, spanning from 2017 to 2023. Moreover, it proposes a novel
classification criterium to organize the analysis based on SLA life cycle
phases. This original point of view can help both academics and industrial
practitioners to understand and properly locate existing contributions in the
advancement of the different aspects of SLA technology. The present work
highlights the importance of the covered topics and the need for new research
improvements to tackle present and demanding challenges.
