#165 [Help] SIPp stops generating RTP after 1024 concurrent calls

[Sami LAOUINI]

Hello,

I am running SIPp on Debian 12 to perform VoIP stress tests (SIP + RTP).
Everything works fine up to 1024 concurrent calls, but starting with call number 1025, SIPp no longer generates any RTP packets. The SBC on the other side eventually sends a BYE after ~5 minutes (expected, due to RTP inactivity).

Environment

Debian 12 (Bookworm)

SIPp version: [please insert your version here]

Scenario: [UAC/UAS/custom XML]

Transport: UDP

Problem observed

Up to 1024 CC → SIP + RTP works normally.

From call 1025 onwards → SIP signaling still works, but RTP is not sent at all (0 packets).

SBC tears down the call due to missing media (BYE after timeout).

No specific errors are shown in sipp_error.log, except earlier I saw:
"Last Error: Could not open socket for RTP streaming: Too many open files..."

Already tested

Increased file descriptors:
ulimit -n 131072
Defined RTP port range:
-min_rtp_port 10000 -max_rtp_port 49999

Reserved RTP ports in the kernel:
sysctl -w net.ipv4.ip_local_reserved_ports=10000-49999

Increased UDP buffer sizes:
sysctl -w net.core.rmem_max=2621440
sysctl -w net.core.wmem_max=2621440

Despite these changes, RTP still stops after 1024 calls.
Question

Is there a known limit of 1024 RTP streams in SIPp?

Do I need to enable an additional option (e.g. -max_socket or similar) to allow more RTP sessions?

Any advice on how to correctly configure SIPp for >1024 concurrent RTP calls?

Thanks a lot for your help,

Regards,
Sami LAOUINI