The present invention relates to a method and terminal for reporting media format adaptation resources to convert a media format of a media stream of a media session to be established between terminals through a packet switched communications network towards a requesting terminal. The invention further relates to a method and NSIS router for reporting media format adaptation resources for converting a media format of a media stream of a media session to be established between terminals. To allow terminals to establish a media session utilizing media adaptation, the invention provides a NSIS (Next Step In Signaling) based signaling framework facilitating the detection and reservation of media adaptation resources on (and off) a media data path on which media data are transported utilizing a media transport protocol among terminals participating in the session.