Prioritization of flows in a home network based on traffic classification is still no guarantee that enough bandwidth will be available between a content server and a client. Besides, such QoS technologies need to be supported by every device in the end-to-end path to be effective, which is relatively expensive for the owners of home networks. In any small-scale IP network, best effort or QoS-enabled, at home or anywhere else, it is therefore preferable to diagnose the network in real time before admitting a new flow. In this article we analyze existing probing techniques, and demonstrate a new method to probe the available bandwidth between a server and a client in a heterogeneous IP-based home network. The tool works with existing end-user devices, is non-intrusive, has a short measurement time, does not require preknowledge of the link layer network topology, and is accurate enough to make decisions about the admission of high-throughput high-quality streams such as for IPTV services.