## 2 Related Work
### Network Slicing Background  
Network slicing provides logically isolated network transmission tunnels using shared physical network resources, with a guarantee of end-to-end QoS requirements, e.g., bandwidth, delay, etc. Network slicing presents the key enabler of cellular network improvements, especially for the 5G cellular network [14], in which three typical network slice types are defined as ultra-reliable low-latency communication (uRLLC), massive machine type communication (mMTC), and enhanced mobile broadband (eMBB). Powered by network \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline \hline
**Symbol** & **Description** \\ \hline eMBB & Enhanced Mobile Broadband \\ \hline GEO & Geosynchronous Equatorial Orbit \\ \hline IoT & Internet of Things \\ \hline LEO & Low-Earth Orbit \\ \hline MEO & Medium-Earth Orbit \\ \hline mMTC & Massive Machine Type Communication \\ \hline NFV & Network Function Virtualization \\ \hline NS & Network Slicing \\ \hline QoE & Quality-of-Experience \\ \hline SDN & Software Defined Networking \\ \hline SP & Service Provider \\ \hline UAV & Unmanned Aerial Vehicle \\ \hline uRLLC & Ultra-Reliable Low-Latency Communication \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The acronyms and their corresponding full forms used in this study. function virtualization (NFV) and software-defined networking (SDN), network slicing has been supported in satellite networks [15; 16; 17] and broader network scenarios, e.g., sensor networks [18], LoRa networks [19], vehicular networks [20], and IoT networks [21; 22]. More challenges arise when network slicing is extended from a single domain to multiple domains, both theoretically and practically. Since network service providers from different domains have heterogeneous costs and interests, it would be important to consider the incentive to encourage cooperation among multiple domains, along with the service quality requirements. While network service provision in a single domain has been widely discussed, there are much fewer relevant studies for the multi-domain case. It is confirmed that no disclosure of the intra-domain topology information is preferable by infrastructure operators [23]. Thus, it is more acceptable to allow operators from each domain to provide an end-to-end network service without revealing the private and internal topology information. Some existing tools may be used, e.g., the border gateway protocol is a conventional routing protocol widely used as an inter-domain solution in the Internet. Another potential solution is the federated learning approach, which is used to build a solution without revealing data privacy for the participants, and has already been proposed to provide multi-domain network slicing orchestration and federated resource control [24; 25]. SDN has also become one of the key enablers of a successful satellite-terrestrial integrated network [26]. With SDN techniques, satellite network service providers can efficiently create, deploy, and manage network services and achieve seamless handovers, both among different satellites/beams or between the terrestrial and satellite segments. In other words, the end users can be served without/barely knowing which kind of network is being used or wondering about the high dynamic feature of satellite networks. To manage the LEO satellite constellations, which is the trend of next-generation satellite networks, a centralized SDN controller can be deployed in a geosynchronous equatorial orbit (GEO) satellite [27] or a medium-Earth orbit (MEO) satellite [28] or in the ground station [29]. Software-defined satellite networks have drawn attention from both academia and the industry with impressive progress in recent years [30], e.g., Amazon, Microsoft, and Google all cooperated with satellite operators to build virtual ground stations with NFV and SDN techniques in recent years. SDN-empowered systems are further proposed for the implementation of network slices with the objectives of efficiency and security, both in the terrestrial and satellite networks [12].