Part 2: How NATs Work, Part II: NAT types and STUN - https://educatedguesswork.org/posts/nat-part-2/

Part 3: How NATs Work, Part III: ICE - https://educatedguesswork.org/posts/nat-part-3/

Part 4: How NATs Work, Part IV: TURN Relaying - https://educatedguesswork.org/posts/nat-part-4/