Return to LanScape's home page Go back a page...       Active TopicsActive Topics   Display List of Forum MembersMember List   Knowledge Base SearchSearch   HelpHelp  RegisterRegister  LoginLogin

SIP Proxy and Media Proxy Products
 LanScape Support Forum -> SIP Proxy and Media Proxy Products
Subject Topic: Sipphone weird behaviour Post ReplyPost New Topic
Message << Prev Topic | Next Topic >>

Joined: February 04 2014
Location: Spain
Posts: 13
Posted: February 17 2015 at 10:39am | IP Logged Quote alberto007


I'm experiencing some weird in the SIP and RTP communications between my sip softphone and the SIP Proxy/Media Proxy.

In the attached Wireshark log, you can see that one softphone is trying to send some messages (ACK) directly to the other end of the call, using its private IP address which is not accessible.
And, it also send these ACK messages to the SIP server to its public IP.

Here is the list of IPs used:

- My local IP address where de Webphone is running (and where I'm sniffing the traffic)
- The SIP server public IP
- The private IP address of the call destination (which is in the same network as the SIP server)

Can you imagine why could this be happening? Why is the phone trying to reach the far end directly (as well as through the SIP server)?
How is it possible that one end gets the IP address of the other end? The sip and media proxies are supposed to hide this information to each other, is it?

I also attach the full wireshark log, if it helps.

Thank you very much for your help. Best regards,


Url to the attached files:

Back to Top View alberto007's Profile Search for other posts by alberto007

Joined: January 26 2005
Location: United States
Posts: 1666
Posted: February 17 2015 at 1:39pm | IP Logged Quote support

Hi Alberto,

For me to look into SIP logs in depth requires paid support. You do not have that with us.

You guys have been a good customer in the past so I want to post something for you...

I see that our SIP proxy does send back the proper 200 OK to the web phone. The web phone then sends the INVITE ACK but the proxy cannot associate the ACK with the call that was set up.

To and From header tags and Call Ids look OK in the INVITE and the final ACK. It may be possible that the ACK request header is not correct in frame 294.

This is not specifying port 5061:
ACK sip:phone-35-3@ SIP/2.0

The problem lies in the contents of the INVITE ACK. It appears the web phone is not specifying the port of the SIP proxy but the port that was specified using the Contact header of the 200 OK response. Why? I bet the SIP proxy is retransmitting the received ACK to and that is why it is not being recognized.

Why the web phone starts using a private IP address on 200 OK retries from the proxy I have no idea but this is a secondary issue. If you solve the problem of the ACK not being accepted by the proxy then nothing after frame 294 really matters.

One other item: Do you guys use a custom DLL with the proxy to manipulate any of the SIP traffic? If you do, you may want to see what the DLL code is doing in a debugger.

I can help fully but we will need paid support in place. Email to discuss an hourly rate.



Back to Top View support's Profile Search for other posts by support Visit support's Homepage

If you wish to post a reply to this topic you must first login
If you are not already registered you must first register

  Post ReplyPost New Topic
Printable version Printable version

Forum Jump
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Contact LanScape Hear what the Lawyers have to say How youm may use this site Read your privacy rights