Section: G.2.2 Communication across service mesh boundaries
Content: It is a deployment where a single service mesh covers all functionality within a given deployment or not. In cases of communication across the boundaries of a service mesh, the service mesh routing the outbound message knows neither whether the selected producer is in a service mesh nor the internal topology of the potential service mesh where the producer resides. In such a deployment, as shown in Figure G.2.2.-1, after producer selection is performed, routing policies on the outgoing service mesh are only aware of the next hop. Given a request sent by A, A's Service Agent will perform producer selection based on the received request. If the selected producer endpoint (e.g. D) is determined to be outside of Service Mesh 1, A's Service Agent routes the request to the Egress Proxy. For a successful routing, the Egress Proxy needs to be able to determine the next hop of the request. In this case, this is the Ingress Proxy of Service Mesh 2. The Ingress Proxy of Service Mesh 2 is, based on the information in the received request and its routing policies, able to determine the route for the request. Subsequently, D receives the request. No topology information needs to be exchanged between Service Mesh 1 and Service Mesh 2 besides a general routing rule towards Service Mesh 2 (e.g. a FQDN prefix) and an Ingress Proxy destination for requests targeting endpoints in Service Mesh 2. Figure G.2.2-1: Message routing across service mesh boundaries