The szPacketType field which is part of NetSim packet structure,  can be updated to provide a custom description to the packet.

Eg:

strcpy(pstruPacket->szPacketType, "MY_PACKET");


This description will be visible in the Packet Trace under the field CONTROL_PACKET_TYPE/APP_NAME.



The packet description can also be visualized in NetSim's Packet Animator.