Stun, turn, and ice protocols in VoIP

One major drawback of using VOIP and video calls is that Nat and firewall restrict the stable completion of calls. Nat and firewall play an important role in security protection and hardening of internal network availability, but they also pose serious problems for establishing VoIP calls between end users.
IETF standard stun, turn, and ice are deployed to handle NAT traversal issues.

Stun helps VoIP endpoints:
After checking whether they are in the NAT/firewall
Determine the Internet address and firewall type. Stun then uses this information to help establish end-to-end VoIP or video calls.

Although stun is effective in handling Nat problems on most users' NAT devices (routers), it is not efficient in many enterprise networks.

Turn (the penetration implemented by relay Nat) can solve this problem. It provides a forward NAT traversal technology that uses media relay servers to facilitate transmission between endpoints.

Ice is a comprehensive structure that uses stun and turn. It provides reliable VoIP or video call configurations and media transmission, A sip supply/response model is used to exchange Multiple candidate IP addresses and ports (such as private addresses and turn server addresses) between the endpoints ).