From 3388bd9e9b82df6d7fe79fa4eee7c22a3277624e Mon Sep 17 00:00:00 2001 From: Dimitri Staessens Date: Tue, 21 Jul 2026 06:54:55 +0200 Subject: ipcpd: Add flow overshoot protection to mb-ecn The ECN marks were the only source of congestion information, and going into congestion collapse (dropping a lot of ECN packets and causing loss of signal) was unrecoverable. The sender's slow-start ramp clock now tracks a measured RTT to avoid overshooting into congestion collapse on the previously fixed (14ms) doubling on long-delay (e.g. 100ms) links. The flow allocator now carries a periodic heartbeat/ack to keep RTT estimates up-to-date. The heartbeat also serves as a congestion collapse detector: consecutive heartbeat losses will go into loss recovery, halving the window and pausing Additive Increase until the path is clear. The DT component now has a max_rtt config parameter that serves as a hint for the layer RTT to optimize slow-start for low-latency networks. These two mechanisms follow TCP, however only during slow start up to the first ECN signal and to recover from a total collapse until the ECN signal returns. MB-ECN is still fully RTT-independent in the AI/PD region. A shorter RTT path will just reach its equal fair share faster than a longer RTT path. Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders --- src/lib/protobuf.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'src/lib/protobuf.c') diff --git a/src/lib/protobuf.c b/src/lib/protobuf.c index a824d357..6beae000 100644 --- a/src/lib/protobuf.c +++ b/src/lib/protobuf.c @@ -362,6 +362,8 @@ dt_config_msg_t * dt_config_s_to_msg(const struct dt_config * s) msg->addr_size = s->addr_size; msg->eid_size = s->eid_size; msg->max_ttl = s->max_ttl; + msg->has_max_rtt = true; + msg->max_rtt = s->max_rtt; msg->routing = routing_config_s_to_msg(&s->routing); if (msg->routing == NULL) goto fail_routing; @@ -381,6 +383,7 @@ struct dt_config dt_config_msg_to_s(const dt_config_msg_t * msg) s.addr_size = msg->addr_size; s.eid_size = msg->eid_size; s.max_ttl = msg->max_ttl; + s.max_rtt = msg->has_max_rtt ? msg->max_rtt : 200; /* ms */ s.routing = routing_config_msg_to_s(msg->routing); return s; -- cgit v1.2.3