webrtc

Which latest (as of 2025 APR) RFC defines the WebRTC ICE Candidate Data format?

Inquiry

Which latest (as of 2025 APR) RFC defines the WebRTC ICE Candidate Data format?

Background

RFC 5245 had defined the ICE candidate data format:

candidate:842163049 1 udp 1677729535 192.168.1.2 61734 typ srflx raddr 10.0.0.2 rport 54321

The format can be clearly identified with RFC 5245 15.1. "candidate" Attribute:

15.1.  "candidate" Attribute

   The candidate attribute is a media-level attribute only.  It contains
   a transport address for a candidate that can be used for connectivity
   checks.

   The syntax of this attribute is defined using Augmented BNF as
   defined in RFC 5234 [RFC5234]:

   candidate-attribute   = "candidate" ":" foundation SP component-id SP
                           transport SP
                           priority SP
                           connection-address SP     ;from RFC 4566
                           port         ;port from RFC 4566
                           SP cand-type
                           [SP rel-addr]
                           [SP rel-port]
                           *(SP extension-att-name SP
                                extension-att-value)

   foundation            = 1*32ice-char
   component-id          = 1*5DIGIT
   transport             = "UDP" / transport-extension
   transport-extension   = token              ; from RFC 3261
   priority              = 1*10DIGIT
   cand-type             = "typ" SP candidate-types
   candidate-types       = "host" / "srflx" / "prflx" / "relay" / token
   rel-addr              = "raddr" SP connection-address
   rel-port              = "rport" SP port
   extension-att-name    = byte-string    ;from RFC 4566
   extension-att-value   = byte-string
   ice-char              = ALPHA / DIGIT / "+" / "/"

However, it has been deprecated and looking for which latest RFC defines it.

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RFC 8445 5.3. Exchanging Candidate Information has similar information but not definitive e.g. Type: The type of the candidate. does not give the clue of using typ in the ICE candidate data.

5.3.  Exchanging Candidate Information

   ICE agents (initiating and responding) need the following information
   about candidates to be exchanged.  Each ICE usage MUST define how the
   information is exchanged with the using protocol.  This section
   describes the information that needs to be exchanged.

   Candidates:   One or more candidates.  For each candidate:

      Address:  The IP address and transport protocol port of the
         candidate.

      Transport:  The transport protocol of the candidate.  This MAY be
         omitted if the using protocol only runs over a single transport
         protocol.

      Foundation:  A sequence of up to 32 characters.

      Component ID:  The component ID of the candidate.  This MAY be
         omitted if the using protocol does not use the concept of
         components.

      Priority:  The 32-bit priority of the candidate.

      Type:  The type of the candidate.

      Related Address and Port:  The related IP address and port of the
         candidate.  These MAY be omitted or set to invalid values if
         the agent does not want to reveal them, e.g., for privacy
         reasons.

      Extensibility Parameters:  The using protocol might define means
         for adding new per-candidate ICE parameters in the future.
Solution

  • The "SDP" definition moved from RFC 5245 to RFC 8839 titled "Session Description Protocol (SDP) Offer/Answer Procedures for Interactive Connectivity Establishment (ICE)".

    Note that browser implementations still mostly use RFC 5245.