## 1 Introduction  
The deployment of future 5G networks will represent an important and challenging source of investment for network operators. Some studies [1; 2] reveal the magnitude of the investments necessary for providing the features expected from future 5G services at a coverage similar to the one offered by previous mobile generations. A way of reducing such investments is the approach of sharing infrastructures among competing operators [3], as commonly happening nowadays, and/or the option of hosting mobile virtual network operators (MVNOs) [4] leveraging on the infrastructure already deployed by some mobile network operators (MNOs) in the field. In fact, it is expected that 5G could foster the appearance of local 5G micro operators [5] that can operate a closed network for its own customers, act as neutral host for mobile network operators' customers, or serve both, offering local context related services and content to complement existing services. Forthcoming 5G advanced services, demanding low latency and/or high bandwidth, will benefit from location proximity to the end user. The more straightforward manner of providing such proximity is by means of the deployment of computing capabilities towards the access, where content, applications and services can be deployed for facilitating the delivery of such innovative services. A number of technological options for distributing computing capabilities at the network edge are emerging, such as Multi-access Edge Computing, Fog Computing or Cloudlet paradigms [6; 7], each showing different degrees of capillarity and functionality. From all of them, Multi-access Edge Computing (MEC), whose technical specifications are being standardized by the European Telecommunications Standards Institute (ETSI) [8], has emerged as the industrial, standard-based reference platform enabling such delivery in proximity, with an important role expected for 5G [9]. MEC describes an edge system that enables edge applications from the provider or a third party to be executed in a network. These applications, for instance, are related to radio network information, location, etc. Some other advanced services could be enabled like streaming, augmented reality, gaming, etc., as described in [10; 11]. Interestingly, the ETSI MEC architectural framework presents the advantage with respect other edge alternatives of an industrial effort on making it coexist with other widely deployed frameworks such as the ETSI Network Function Virtualization [12] and the 3 GPP architecture [13], then presenting a roadmap of joint interworking, resulting on an industry backed-up choice for addressing the edge computing solution space. Thus, this paper concentrates on ETSI MEC as subject of analysis. In this new ecosystem demanding large investments and involving multiple actors, the integration of MEC environments from different stakeholders (in scenarios enabled by MVNOs, local 5G micro operators or infrastructure sharing) can largely benefit and assist on the generalization of the availability of such new 5G services. The integration of those environments requires the interaction of different administrative domains, imposing some challenges like security, discovery of resources and services, etc. Such a multi-domain scenario, however, has not been yet specified. Thus, the motivation of this paper is to analyze the different alternatives of multi-domain interworking feasible in MEC from an architectural point of view, in order to determine initial implications of such multi-provider scenarios. The contribution is threefold: (i) to describe distinct integration models as enabled by the ETSI MEC architecture definition; (ii) to elicit business and technical implications for each of that models; and (iii) to summarize the interactions among administrative domains in the deployment of MEC applications in a multi-domain scenario. The structure of the paper is as follows. Section 2 briefly discuss different technological approaches for edge computing.