Hello, Thanks for this feedback. Here the description of the issue I am trying to solve. I use already tcp_keepalive. Call flow is: UACs --> Nat device --> Kamailio Transport protocol is TLS. Kamailio sends TCPs keepalive (tcp_keepalive option) to the softphone located behind the nat devices in order to prevent disconnection due to network inactivity. In most cases I have the expected behavior, I do not have any problems. I think somes NAT devices don't properly handle TCPs keepalive because they close the connection after TCP keepalives. I have always this issue with NAT devices using VSS-Monitoring protocol. A network capture shows: - Kamailio sends a tcp keepalive - The NAT device sends a tck keepalive ACK to Kamailio with a new filed : vss-monitoring Frame 70: 62 bytes on wire (496 bits), 62 bytes captured (496 bits) Linux cooked capture Internet Protocol Version 4, Src: x.x.x.x, Dst: x.x.x.x Transmission Control Protocol, Src Port: 13178, Dst Port: 443, Seq: 2752, Ack: 6214, Len: 0 *VSS-Monitoring ethernet trailer, Source Port: 0* *Src Port: 0* - Kamailio received then a TCP from the NAT device that notifies the closure of the connection. Frame 73: 87 bytes on wire (696 bits), 87 bytes captured (696 bits) Linux cooked capture Internet Protocol Version 4, Src: x.x.x.x, Dst: x.x.x.x Transmission Control Protocol, Src Port: 13178, Dst Port: 443, Seq: 3436, Ack: 6214, Len: 31 Secure Sockets Layer TLSv1.2 Record Layer: Alert (Level: Warning, Description: Close Notify) Content Type: Alert (21) Version: TLS 1.2 (0x0303) Length: 26 Alert Message Level: Warning (1) Description: Close Notify (0) - After a FIN ACK sent to Kamailio by the NAT device, a new tcp three-way handshake is made again. Sometimes, I have this issue during the connection establishment that cause a problem of sending or receiving SIP messages (for examples 200 OK and ACK). The advantage of the SIP ping options is a bidirectional traffic through NAT. I think in this case, my issue will be solved. Regards Abdoul OSSENI 2017-04-05 12:48 GMT+02:00 Daniel-Constantin Mierla &lt;miconda(a)gmail.com <mailto:miconda@gmail.com>>: Hello, nathelper module does ping OPTIONS only for UDP. For tcp/tls, there is transport layer keepalive: - https://www.kamailio.org/wiki/cookbooks/5.0.x/core#tcp_keepalive <https://www.kamailio.org/wiki/cookbooks/5.0.x/core#tcp_keepalive> What is the problem you are trying to solve with this? Maybe there are some other options for it. Cheers, Daniel On 31.03.17 13:03, Abdoul Osséni wrote: -- Daniel-Constantin Mierla www.twitter.com/miconda <http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda <http://www.linkedin.com/in/miconda> Kamailio Advanced Training - May 22-24 (USA) - www.asipto.com <http://www.asipto.com> Kamailio World Conference - May 8-10, 2017 - www.kamailioworld.com <http://www.kamailioworld.com>

On 6/04/2017, at 12:25 AM, Abdoul Osséni &lt;abdoul.osseni(a)gmail.com&gt; wrote: I have always this issue with NAT devices using VSS-Monitoring protocol. A network capture shows: - Kamailio sends a tcp keepalive - The NAT device sends a tck keepalive ACK to Kamailio with a new filed : vss-monitoring Frame 70: 62 bytes on wire (496 bits), 62 bytes captured (496 bits) Linux cooked capture Internet Protocol Version 4, Src: x.x.x.x, Dst: x.x.x.x Transmission Control Protocol, Src Port: 13178, Dst Port: 443, Seq: 2752, Ack: 6214, Len: 0 *VSS-Monitoring ethernet trailer, Source Port: 0* * Src Port: 0* Hi, VSS-Monitoring is a function of your monitoring tap, is is not a function of your NAT box - http://www.vssmonitoring.com/resources/feature-brief/ Port-and-Time-Stamping.pdf It should not be included in the actual traffic packets going past the tap - only the packets that you see on your network analyser - if you find that it is included on actual packets, you need to talk to your networking people and get that fixed. It is very unlikely that a NAT device sends anything other than synthesised RST packets. It certainly won’t be generating close notify TLS alerts - I’m not actually sure that it can, they might need to be authenticated. If you are seeing a close notify, you should capture between the UAC and the NAT device - I believe you will see the close notify TLS alert coming from the UAC. If that is the case, you need to look at the UAC for why it’s doing that. Perhaps your UAC does not support TCP keepalives properly. -- Nathan Ward _______________________________________________ SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list sr-users(a)lists.sip-router.org http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users

The advantage of the SIP ping options is a bidirectional traffic through NAT. I think in this case, my issue will be solved.