Ryan Malloy
aa4bb512ea
Created comprehensive troubleshooting guide documenting the multi-layer debugging of Twilio calls dying at exactly 64 seconds. ### Root Cause: UDP conntrack timeout (30s) < SIP Timer H (32s) = ACK dropped at kernel Timeline: - t+30s: conntrack expires UDP NAT mapping - t+32s: Asterisk final 200 OK retransmit → Twilio ACK - Kernel drops ACK (no conntrack entry) - t+64s: Timer H fires → call dies (2× Timer H = 64s) ### The Fix (applied by flextel agent on docker-2): ```bash sudo sysctl -w net.netfilter.nf_conntrack_udp_timeout=120 echo "net.netfilter.nf_conntrack_udp_timeout = 120" | \ sudo tee /etc/sysctl.d/99-sip-conntrack.conf ``` 120s timeout provides 88s headroom beyond Timer H (32s). ### Documentation Added: - docs/troubleshooting/udp-conntrack-ack-loss.md - Full case study with: - Investigation timeline (3 layers: SIP timers, sip-guardian, conntrack) - Timing conflict tables showing conntrack vs SIP protocol interaction - Packet capture evidence - Architectural improvements (ACK fast-path) - Lessons learned from cross-layer debugging - README.md - Added troubleshooting entry with quick-fix and case study link ### Agent Thread: - 008-flextel-applied-conntrack-fix-noting-it-didnt-land-from-your-side.md Notes that the sysctl fix was applied by flextel agent after diagnosis. Confirms timing analysis was the smoking gun. ### Defense in Depth: 1. Kernel: conntrack timeout increased (production fix) 2. Userspace: ACK fast-path in sip-guardian (architectural fix) Both layers now protect against this failure mode. Credit: Multi-agent debugging via agent-thread protocol. flextel agent applied the production fix and confirmed the diagnosis. See: docs/agent-threads/ack-loss-from-twilio-trunk/ |
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| udp-conntrack-ack-loss.md | ||