Network node, entity and methods performed therein for handling a communication session in a communication network

A method performed by entities of two established communication sessions for handling a communication session in a communication network using a session description protocol, SDP, for communication sessions, where at least one network node is configured to connect the entities of the two established communication sessions with each other, the method comprising:

• sending, on the two established communication sessions, from one of the entities towards the other one of the entities, a request with a request indication, wherein the request indication indicates a request of one or more mappings of a payload type number to a codec associated to the established communication session;
• intercepting the request and checking whether or not the other one of the entities is a final destination of the request;
• in response to the other one of the entities being not the final destination of the intercepted request, forwarding the intercepted request to another one of the entities that is the final destination of the request;
• in response to the other one of the entities being the final destination of the intercepted request, adding a response indication to a response, wherein the response indicates one or more supported mappings of a payload type number to a coded of the communication established session;
• sending, on the two established communication sessions, from the other one of the entities towards the one of the entities, the response;
• suggesting a mapping of a payload type number to a codec associated to the communication session based on knowledge of used payload type numbers mapped to a different codecs according to the received response;
• sending, on one of the two established communication sessions, to the one of the entities, an invite with an invite indication, wherein the invite indication indicates the suggested mapping of a payload type number to a codec associated to the communication session;
• selected the suggested mapping of a payload type number to a codec associated to the communication session by taking the invite indication into account;
• generating an offer message with the selected mapping of a payload type number to a codec associated to the communication session by the one of the entities;
• sending, on the two established communication sessions, from the one of the entities towards the other one of the entities, the offer message;
• and
• performing an SDP exchange according to the received offer message.