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 <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

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:
Hi,

Is it possible to send ping OPTIONS over tcp or tls?

If yes, could you me how?

Regards

Abdoul.
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