ICE

ICE (Interactive Connectivity Establishment) is a framework used by WebRTC (among other technologies) for connecting two peers to each other, regardless of network topology (usually for audio and/or video chat). This protocol lets two peers find and establish a connection with one another even though they may both be using Network Address Translator (NAT) to share a global IP address with other devices on their respective local networks.

The framework algorithm looks for the lowest-latency path for connecting the two peers, trying these options in order:

1. Direct UDP connection (In this case—and only this case—a STUN server is used to find out the network-facing address of a peer
2. Direct TCP connection, via the HTTP port
3. Direct TCP connection, via the HTTPS port
4. Indirect connection via a relay/TURN server (if a direct connection fails, e.g. if one peer is behind a firewall that blocks NAT traversal)

Learn more

General knowledge

• WebRTC, the principal web-related protocol which uses ICE
• WebRTC protocols

Technical reference

• RFC 5245, the IETF specification for ICE
• RTCIceCandidate, the interface representing a ICE candidate