Peer-to-peer overlays can be used for service discovery over a global network fabric. We describe and evaluate a new service indexing mechanism for in-band streaming services such as application relays, mixers, and media transcoders. For this type of service, the location of the service in the network and service admission status are key attributes. We describe and analyze a service indexing mechanism which uses network position-based advertisement. We show that this mechanism gives good service selection, provides a close to uniform advertisement distribution in the overlay, reduces message overhead, and exhibits acceptable stability and setup delay. Keywords-service discovery; application relay; DHT; overlay.