Summary of 3GPP Technical Document S4-260117
Document Information
- Specification: TS 26.113 v19.1.0
- CR Number: 0015
- Category: F (Correction)
- Release: Rel-19
- Work Item: iRTCW-TEI (Interactive Real-Time Communication Web - Technical Enhancement and Improvement)
- Source: Qualcomm Inc.
Purpose and Rationale
The CR addresses an ambiguity in the SWAP (Streaming and WebRTC API) specification regarding the handling of the accept message in response to a close operation. Currently, the specification is unclear about whether the answer field (containing SDP answer) should be included in the accept message when responding to a close message, leading to potential implementation confusion.
Technical Changes
Accept Message Handling (Clause 13.2.4.4.5)
Description Updates (13.2.4.4.5.1)
- Previous behavior: Accept message always contains answer SDP when replying to connect or update requests
- Clarification added:
- Accept message shall contain answer SDP when responding to connect or update messages
- Accept message shall NOT contain SDP when responding to close messages
- Explicitly separates the two use cases for the accept message
Parameter Definition (13.2.4.4.5.2)
- answer parameter: Changed from mandatory to optional
- Modified to "This parameter, when present, shall contain the answer SDP"
- Makes it clear that answer is conditionally included based on the triggering message type
Update Message Clarification (13.2.4.4.6.1)
- Reinforces that update message is for partial media teardown (half-close)
- Distinguishes from close message which performs full session termination
- Note added emphasizing the use of close message for full session termination
Close Message Clarification (13.2.4.4.8.1)
- Explicitly states that accept message response shall be "without an SDP payload"
- Clarifies session teardown procedure: accept message triggers resource release
- Note added distinguishing close (full termination) from update (partial teardown)
Impact
The changes ensure proper protocol behavior by:
1. Removing ambiguity in accept message structure based on context
2. Preventing unnecessary SDP exchange during session termination
3. Clearly delineating between partial media teardown (update) and full session termination (close)