This article original from Http://blog.csdn.net/voipmaker reprint annotated source.
WEBRTC clients establish a call through interactive candidate to achieve NAT traversal, if these interactions candidate in the Offer/anwser SDP will lead to through the establishment time is very slow,
Because the WEBRTC client needs to communicate with the Stun/turn server to get these candidate, the entire process is block, in order to increase the speed of call establishment, WEBRTC introduced trickle ice, in interactive offer, Answer in the process of parallel sending candidate to do connectivity detection, when signaling the adoption of the SIP protocol, a specification is required to define the entire process, there is a draft, in particular can see
Https://tools.ietf.org/html/draft-ietf-mmusic-trickle-ice-sip-01
This specification sends candidate through SIP info message, sends in dialog SIP info message to each other immediately after SIP dialog is established, achieves the purpose of concurrent execution with offer, answer, improves the speed of call establishment,
WebRTC SIP Trickle Ice