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bump webrtc fork: MTU-safe bundles, a reordering window, tail loss within the RTT

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rustdesk-org/webrtc cc6633bc, three commits on 825a0a48, all on the path
that sends without a congestion window:

Both bundlers counted a DATA chunk by its payload alone; with the header and
padding counted, bundles of small chunks stay within the MTU, and the fragment
payload rounds down to 1160 so a full chunk does too. A chunk is fast
retransmitted at most five times, KCP's IKCP_FASTACK_LIMIT.

A frame's chunks go out within microseconds of each other, so on a path that
jitters the send-order rule resent every chunk that landed behind three of
its siblings: 2.7x the payload on the wire at 10ms of jitter, and on a link
without the room for that, a queue that fed on itself. A reordering window,
RACK's, makes evidence count only from what was sent a quarter of an srtt
after the chunk once the path is seen to reorder, widening on the duplicate
TSNs the receiver reports. 5 Mbps, 1% loss, 20ms jitter: 600 of 600 frames
at a 98ms mean where 290 arrived at 6.2s.

A chunk lost at the tail of a burst has only T3-rtx, which ran from floors
sized for a 200ms delayed ack and restarted only on the tail's predecessor's
ack: 600ms and more. Every DATA chunk now carries the I bit, the floors are
KCP's shape, and a fast retransmission restarts the timer. One 200-byte
message per frame at 5% loss: 9 of 600 later than 200ms, from 42.

Random loss without jitter is unchanged at every rate and frame size.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019aokqJuhjvB3kijXtAg5Ns
This commit is contained in:
rustdesk
2026-09-05 22:55:44 +08:00
parent dd5f4cd866
commit 7bab2c3297
2 changed files with 7 additions and 4 deletions
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4
Cargo.lock generated
View File

@@ -9708,7 +9708,7 @@ dependencies = [
[[package]]
name = "webrtc-sctp"
version = "0.12.0"
source = "git+https://github.com/rustdesk-org/webrtc?rev=825a0a4862818f74406d8e1cc25be72259228235#825a0a4862818f74406d8e1cc25be72259228235"
source = "git+https://github.com/rustdesk-org/webrtc?rev=cc6633bc240936b4973a3a30b12dad02d9a57f3f#cc6633bc240936b4973a3a30b12dad02d9a57f3f"
dependencies = [
"arc-swap",
"async-trait",
@@ -9748,7 +9748,7 @@ dependencies = [
[[package]]
name = "webrtc-util"
version = "0.11.0"
source = "git+https://github.com/rustdesk-org/webrtc?rev=825a0a4862818f74406d8e1cc25be72259228235#825a0a4862818f74406d8e1cc25be72259228235"
source = "git+https://github.com/rustdesk-org/webrtc?rev=cc6633bc240936b4973a3a30b12dad02d9a57f3f#cc6633bc240936b4973a3a30b12dad02d9a57f3f"
dependencies = [
"async-trait",
"bitflags 1.3.2",

7
Cargo.toml
View File

@@ -222,9 +222,12 @@ libxdo-sys = { path = "libs/libxdo-sys-stub" }
# and fast retransmit cannot cover a request/response exchange; INITIAL_MTU 1228 also fragments on
# IPv6; and its AIMD pins a lossy long-haul link to MSS/(RTT*sqrt(p)), so a switch sends without
# a congestion window, as KCP does - on by default, `allow-webrtc-congestion-control` opts back in.
# Sending that way, a reordering window keeps a chunk that is merely late from being resent on a
# path that jitters, every DATA chunk asks for its SACK at once so a lost tail is back within an
# RTT at KCP's RTO floors, and bundles of small chunks stay within the MTU.
# Pinned by rev, not branch: a fork branch can be rewritten out from under the lockfile.
webrtc-util = { git = "https://github.com/rustdesk-org/webrtc", rev = "825a0a4862818f74406d8e1cc25be72259228235" }
webrtc-sctp = { git = "https://github.com/rustdesk-org/webrtc", rev = "825a0a4862818f74406d8e1cc25be72259228235" }
webrtc-util = { git = "https://github.com/rustdesk-org/webrtc", rev = "cc6633bc240936b4973a3a30b12dad02d9a57f3f" }
webrtc-sctp = { git = "https://github.com/rustdesk-org/webrtc", rev = "cc6633bc240936b4973a3a30b12dad02d9a57f3f" }
[package.metadata.winres]
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