**Hi Kamailio Community,** I am experiencing an issue with delayed SIP processing and dropped packets under high load, and I would appreciate some advice on tuning or architecture.
**Environment & Setup:** * **Kamailio:** v6.1.2 * **RTPEngine:** ngcp-rtpengine 13.5.1.3+0~mr13.5.1.3 (using kernel module `table=0`) * **OS:** Debian 13 * **Hardware:** 56 CPU Cores (Note: Kamailio and RTPEngine are running on the *same* physical server) * **Kamailio Config Snippet:** `children=40`, `tcp_children=40` **The Scenario & Symptoms:** The system handles traffic coming from FreeSWITCH. When the concurrent calls (CC) reach around 3000, we start observing two major issues: **1. RTPEngine UDP Queue Warnings:** We frequently see the following warning in the RTPEngine logs: `Too many packets in UDP receive queue (more than 50), aborting loop. Dropped packets possible` **2. Kamailio missing SIP packets (Silent Drops):** FreeSWITCH sends an `INVITE` to Kamailio. When I capture traffic with `tcpdump`, I can see the initial `INVITE` arriving at the server's network interface, followed by several retransmissions. However, Kamailio (verified via the `sipdump` module and xlogs) does not seem to receive the initial requests. It often only registers the `INVITE` on the 4th or 5th retransmission. **3. Latency checking:** To check if the Kamailio routing script is blocking, I enabled `latency_cfg_log=1`. The logs show acceptable execution times during this high-load period: `NOTICE: request-route executed in: 18510 usec` (~18.5ms) **My Questions:** 1. Since `tcpdump` sees the packets but Kamailio doesn't, is this a classic case of OS-level UDP receive buffer (`rmem`) overflow, possibly exacerbated by CPU context switching between Kamailio and RTPEngine? 2. With `children=40` for Kamailio and RTPEngine also running on the same 56-core machine, is this configuration leading to significant CPU contention or an imbalanced distribution of workload, especially at 3000 CC? Should Kamailio's `children` count be adjusted (e.g., increased closer to 56, or perhaps fewer to leave more for RTPEngine and OS network processing)? 3. Does this scenario typically imply that the host CPU is exhausted/interrupt-bound, or is there a specific Kamailio/OS tuning I am missing? Any insights or recommendations on how to further debug this would be greatly appreciated! Thanks, __________________________________________________________ Kamailio - Users Mailing List - Non Commercial Discussions -- [email protected] To unsubscribe send an email to [email protected] Important: keep the mailing list in the recipients, do not reply only to the sender!
