# On Blockchain-Based Cross-Service Communication and Resource Orchestration on Edge Clouds
## 3 Network Service Marketplace Architecture  
### NFV-Related Definitions  
Towards the establishment of CSC and NSM, it is important to describe the basic NFV assets that are taken into account in the proposed solution. Aligned with the ETSI-NFV architecture [11], a service chain corresponds to the network slice, which describes the main interactions as well as the network communications between the services. Based on OSM information model [9], a service chain is described in the Network Slice Template (NST). An example of such NST is shown in Listing 1. The main fields of the NST are the _netslice-subnet_ and the _netslice-vld_. The _netslice-subnet_ objects are the declared services of the slice. For each service, the slice owner determines the corresponding network service descriptor--which in OSM model is defined as _nsd_--in the _nsd-ref_ key, the name of the service and a Boolean key about enabling sharing for a specific service with other slices, in the _is-shared-nss_ field. Therefore, a slice owner can share any of the services that is included in an NST. The _netslice-vld_ objects correspond to the networking management of the service chain. A _netslice-vld_ object consists of various parameters. These parameters refer to both Management and Orchestration (MANO) level information (e.g., the identifier, name of the virtual network--vld) and to the Virtual Infrastructure Manager (VIM) level, such as configuration about VIM networking. Also, the connection points for each service, which is attached to that vld, are included. A network service consists of one or more VNFs, in which the necessary functionality of the service is implemented. Each VNF constitutes of a specific instance at the VIM level. The interested reader can refer to [8] for more details about network service and VNF descriptors.  
Considering the above features of the OSM Model and based on the ETSI-NFV architecture, we can design appropriate architectures and implement efficient mechanisms, in order to facilitate the cross-service interaction between services of different slice owners, leading to the network service marketplaces establishment.  
SST descriptor example of a Service Provider. The slice consist of 2 Services. The second of them is shared
among other slice tenants.  Inst:  - 1d: provider_slice_mstd  name: provider_slice_mstd  SNSSAI-identifier:  slice-service-type: eMBB  quality-of-service:  id: 1  netslice-subnet:  -  id: provider-service-1  is-shared-nss: 'false'  description: NetSlice Subnet (service) composed by 1 vnf with 2 cp  nsd-ref: provider-service-1_nsd  -  id: provider-service-2  is-shared-nss: 'true'  description: NetSlice Subnet (service) composed by 1 vnf with 3 cp  nsd-ref: provider-service-2_nsd  
netslice-vld:  -  id: slice_vld_mgmt  name: slice_vld_mgmt  type: ELAN  mgmt-network: 'true'  nss-connection-point-ref: -  nss-ref: provider-service-1  nsd-connection-point-ref: nsd_cp_mgmt  -  nss-ref: provider-service-2  nsd-connection-point-ref: nsd_cp_mgmt  -  id: slice_vld_data  name: slice_vld_data  type: ELAN  mgmt-network: 'false'  nss-connection-point-ref: -  nss-ref: provider-service-1  nsd-connection-point-ref: nsd_cp_data  -  nss-ref: provider-service-2  nsd-connection-point-ref: nsd_cp_data  
**Listing 1**. Provider's NSTD.