Method and apparatus in a router (200) of an IP network, for providing a relevant and expected service level for a first subscriber (A) in a peer-to-peer session with a second subscriber (B). When a session setup message (PATH) sent from the first subscriber is received (2:2) at the router, a required service level is detected from a service level indicator in the received message, and a service level definition of an operator of the first subscriber is obtained (2:3) for interpreting the service level indicator. Communication resources required for data transmission during the session are determined (2:4) according to the detected service level as interpreted by the service level definition. The determined communication resources are then booked (2:4) in the router, and the session setup message is forwarded (2:7) to a next hop node in the transmission path towards the second subscriber.