CODEWITHSUNDEEP
webrtc
Adrian Ber
Adrian Ber

Reputation: 21360

Trickle ICE - choose candidate

In WebRTC, how are the ICE candidates selected and used? If a new candidate is added, it will be used and if yes, when?

Upvotes: 2

Views: 1522

Answers (1)

Palash Borhan Uddin
Palash Borhan Uddin

Reputation: 394

Newly gathered candidates needs to be advertised to other end using signalling then it will be paired with the remote candidates for both ends and restart the ICE processing for the new pairs. If any of the pairs gets succeeded and the priority value set by ICE is higher than the existing selected candidates then offerer end will select this new pair as favoured and selected candidate and start using this new pair of selected candidates. Some time it may require to send updated offer using the selected candidates through signalling.

Sending updated offer/answer depends on the design or implementation of the client or ICE implementation. Basically for anything changes related with the ICE attributes from initial offer/answer requires updated offer. As per RFC when ICE candidates are selected then offerer end shall include "a=remote-candidates" with the selected candidates and exchange the updated offer/answer. If client doesn't requires explicitly the updated offer as the indication of remote-candidates then its fine not to send any updated offer, you can try by not sending this and see what happens. It's should be harmless if you send updated offer all the time as well as long as the other client can parse this and recognises the attributes.

In FF or Chrome browser default implementation of WebRTC (Trickle ICE) you don't need to get worried about updated candidates, as client end will receive events when an ICE candidate is available to retrieve so you will just retrieve that and send to other end. For re-Invite case, call createOffer once the ICE state goes to "completed" state on the Controlling (Offerer) side.

Upvotes: 4

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