Cisco Cisco Microsoft AT&T Vinci Systems Juniper Networks This document presents techniques built upon BGP/IP MPLS VPN control plane mechanisms to construct virtual topologies for service chaining. These virtual service topologies interconnect network zones and constrain the flow of traffic between these zones via a sequence of service nodes so that service functions can be applied to the traffic. This document also describes approaches enabled by both the routing control plane and by network orchestration to realize these virtual service topologies.