A system, and computer program product for identifying reset source and reason in a TCP session are provided in the illustrative embodiments. A reset packet is prepared for the TCP session. An identifier associated with the target data processing system is added using a first header in the reset packet. The identifier associated with the target data processing system is unknown to a sender a data packet in the TCP session. The sender sends the data packet to another data processing system during the TCP session. A reason for resetting the TCP session is added using a second header in the reset packet. The TCP session is reset by sending the reset packet.