Dear Kamailio Developers,
I am using Kamailio as a SIP server to facilitate a phone call, but I am encountering an issue where the call cannot be established due to Kamailio sending a 408 Request Timeout to the caller. Issue Details:
- A (Caller) sends an initial INVITE to Kamailio, which then forwards it to B (Callee). The INVITE contains the following Supported header:
Supported: timer,100rel,replaces,precondition,from-change,histinfo,tdialog
I suspect the *precondition* option may be relevant to the issue.
- *B* responds with a *183 Session Progress* message, which includes:
Require: 100rel,precondition
Kamailio correctly forwards this response to *A.*
- *A* then sends a *PRACK* request to Kamailio. However, this request contains:
Require: sec-agree Supported: timer
Notably, *precondition* is absent from both the *Require* and *Supported* headers.
- Kamailio forwards this *PRACK* to *B*, and *B* responds with *200 OK*, including:
Supported: 100rel,from-change,tdialog
- However, Kamailio does not seem to acknowledge *B's 200 OK* and instead *keeps retransmitting the PRACK* to *B*. B responds with *200 OK* again, but the cycle repeats.
- After three retransmissions of *PRACK*, Kamailio eventually sends *408 Request Timeout* to *A*, leading *A* to send a *CANCEL* request.
Device Used:
- *Caller (A):* Asus ROG Phone 5 - *Callee (B):* Asus ROG Phone 6
Both are commercially available mobile phones.
Possible Cause:
According to *3GPP TS 24.229, Subclause 5.1.3.1*,
If the received response with an SDP body includes a Require header with
In this case:
- The *183 Session Progress* from *B* contains Require: *precondition*. - The subsequent *PRACK* from *A* does not include *precondition* in either *Require* or *Supported*.
Could this mismatch be the reason Kamailio keeps retransmitting *PRACK* and ignoring *B's 200 OK*? Or could there be another factor causing Kamailio to behave this way?
If additional details are needed, please let me know.
Best regards, Ping Kuan Kao
Hi The header fields should not be the reason that the reply is not processed. By default, kamailio should process the response even its content is something that the endpoints won't like.
If you can provide that SIP request and response (a packet capture may also be good), then it might be obvious to someone if something is wrong with it. Does your config file have anything in a reply route (sanity-checking, etc) that might be dropping the replies?
James
On Sun, 23 Feb 2025 at 07:15, 高秉寬 via sr-users sr-users@lists.kamailio.org wrote:
Dear James,
Thank you for your response.
I have attached two packet capture (.pcap) files for reference:
- *success.pcapng* – A case where the call succeeds. - *failure.pcapng* – A case where the call fails with a 408 timeout.
For context, the relevant IP addresses in the captures are:
- *172.16.6.204* – Kamailio - *10.70.0.16* and *10.70.0.17* – The UEs
Regarding your question about the configuration file: To my knowledge, there is nothing in the reply route (such as sanity-checking) that would be dropping the replies. However, if you suspect something specific, I’d be happy to double-check.
Please let me know if you need any additional details.
Best regards,
Ping Kuan Kao
James Browne james@frideo.com 於 2025年2月24日 週一 下午9:21寫道：
Hi
The SIP is in there, alright, but encapsulated in multiple layers. It's confusing to read that pcap, alright.
I used filter "gtp and ip.addr==10.70.0.16" in Wireshark. I see that the INVITE, the SIP-100 response, the SIP-183 response and the later CANCEL (and its response) all were encapsulated with IP, UDP, GTP, IP and ESP, but that the SIP-200 responses (frames 29, 31,35) to the PRACK were not (they have IP, UDP, GPT, IP, UDP and then SIP, but not the ESP). I don't see anything in the SIP that looks wrong to me, so it looks like a routing problem with whatever networking you have set up, and not actually any problem with SIP. That's my best guess.
Anyway, to troubleshoot further, you might add some logging to kamailio. Simply add an xlog to the very top of the onreply_route. If you see a log for the SIP-183 INVITE response but not for the SIP-200 PRACK response, then it shows that the SIP message does not even get to kamailio, which is my suspicion. If the message does actually get to kamailio (and my suspicion is wrong), then you might try setting the debug level high enough to see exactly what kamailio does with the response (and why it drops it).
James James
On Wed, 26 Feb 2025 at 06:49, Sergey Safarov s.safarov@gmail.com wrote:
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James Browne -
Sergey Safarov -
高秉寬