In one embodiment, a first device in a network sends a Session Traversal Utilities for Network Address Translation (STUN) binding request towards an endpoint device of a media session between the first and endpoint devices. The binding request includes one or more network attribute fields. The first device receives a binding response from an intermediate node between the first and endpoint devices in the network, in response to sending the binding request towards the endpoint device. The intermediate node inserted the one or more network attribute fields into the binding response. The received binding response includes one or more metrics for the media session in the one or more network attribute fields. The first device adjusts one or more bitrates of the media session based on the one or more metrics for the media session in the received binding response.