Topology

Single environment

Hub and spoke

flowchart TB
    Contoso --> Fabricam
    Contoso --> Northwind
    Contoso --> ProseWare

Mesh

flowchart LR
    Contoso <--> Fabricam
    Contoso --> Northwind 
    Fabricam --> ProseWare   
    Northwind <--> ProseWare
    Northwind --> Fabricam
    Contoso --> ProseWare

flowchart TB
    Contoso --Chart of Accounts--> Fabricam
    ProseWare --Items--> Northwind 
    Contoso --Chart of Accounts--> Northwind     
    Fabricam --Items--> ProseWare       
    Northwind --Resources--> ProseWare    
    Northwind --Resources--> Fabricam    
    Contoso --Chart of Accounts--> ProseWare    
    ProseWare --Items--> Contoso 

Multiple Environments

flowchart TB
    subgraph BC_Env_US
        direction LR
        Contoso 
        Fabricam
    end
    subgraph BC_Env_GB
        direction LR
        Northwind 
        ProseWare
    end
    ASB[(Azure Service Bus)]    
    Contoso<-->ASB
    Fabricam<-->ASB
    Northwind<-->ASB
    ProseWare<-->ASB