RTCIceCandidateStats: priority property

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The priority property of the RTCIceCandidateStats dictionary is a positive integer value indicating the priority (or desirability) of the described candidate.

Value

A positive integer indicating the priority of the RTCIceCandidate described by the RTCIceCandidateStats object. The value may be anywhere from 1 to 2,147,483,647.

Description

During ICE negotiation while setting up a WebRTC peer connection, the priority values reported to the remote peer by a user agent are used to determine which candidates are considered "more desirable". The higher the value, the more desirable the candidate is.

Determining priority

The ICE specification describes how user agents and other software using WebRTC should calculate the priority. The priority of a candidate is calculated using the following variables as inputs:

• The preferability of the candidate type (local, server reflexive, peer reflexive, or relayed)
• The preferability of the candidate's specific IP address (for multihomed agents)
• The candidate's component ID (1 for RTP, 2 for RTCP)

The candidate's priority is computed using the formula (p_type is the priority of the candidate's type and p_local is the priority of the IP address):

$$\mathit{priority} = 2^{24} \times p_{type} + 2^{8} \times p_{local} + \left(\right. 256 - \mathit{componentID} \left.\right)$$

This is equivalent to mapping the priorities of the candidate type, the local IP, and the component ID into various bit ranges within the 32-bit priority value.

Specifications

Browser compatibility

See also

• RFC 5245, section 4.1.2.1: Recommended Formula section in the ICE specification