When there is no outstanding data, then next TSN to allocate should always be one more than what the client has last ACKed. Bug: None Change-Id: Ieb8b5b23912d77d96fe3749fb53fd53652d97066 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/232002 Commit-Queue: Victor Boivie <boivie@webrtc.org> Reviewed-by: Florent Castelli <orphis@webrtc.org> Cr-Commit-Position: refs/heads/main@{#35016}