The present studies of NAT traversal are focused on the commonest cone type of NAT type which has the biggest market share. There are two basic techniques of NAT traversal which are STUN (Simple Traversal of UDP through NAT) and TURN (Traversal Using Relay NAT). STUN cannot traversal symmetric NAT and TURN would cause high loading on relay server. Except for cone type NAT has been solved, symmetric NAT which assigned outgoing port number increase by sequence has been traversal successfully by predicting next possible outgoing port number. It still exists one type of symmetric NAT which assign...