Can an operator change settings/execute code in the phone without the user being noti

[bravotango]

There are many threads in this forum on how to change settings not meant to be changed by the user. I suddenly find that the phone is using such information which I have not entered. It seems that those settings have been entered/fetched from an operator without my knowledge. Should this be possible for an operator the implications are most interesting and I would appreciate comments:

I was loosing registration when using the operator Sipgate with my E61. The problem was caused by a function called ALG in my router. Turning of the ALGs solved the problem and it works excellent now. When debugging I sniffed the traffic from the Internet to the router. A registration process started with a request to REGISTER from the E61, after a successful registration nothing happened until the lease time had expired and the E61 should register again. After solving the problem with the router it continued like this.

It still works excellent but yesterday I noticed from the light emitting diodes on the router that there was a frequent traffic from the router to the E61 which had not been there before. Roughly every 15 seconds there was traffic. I sniffed the traffic between the router and the E61 and found:

- Before the actual request for REGISTRATION the E61 contacts stun1.sipgate.net and gets a prompt reply. No data in the packets which I can parse. After that registration proceeds immediately as usual.

- After that a repeated cycle starts where the E61 sends a packet to sipgate.co.uk (registrar and proxy server) and imidiately another to stun1.sipgate.net. After roughly 7 seconds the E61 gets a packet from sipgate.co.uk, after another 14 seconds another packet from sipgate.co.uk. After another 10 seconds the cycle starts again by the E61 sending packets to sipgate.co.uk and to stun1.sipgate.net again. A cycle with a period time of roughly 30 seconds. This continues until it is time for REGISTRATION again. Small UDP packets with nothing I can parse.

MY QUESTIONS

- From where does the E61 get the address to the stun server? I haven't entered it. As a user I can not enter it.

- What is initiating the contact with the stun server before the registration and the communication between renewals of the registration? Have I got “stun” without requesting it.

[cdavies]

It's nothing to do with your operator. The client just sends a DNS SRV request to your SIP provider to look for STUN servers, and if there's an entry then it'll use it. Because almost all mobile phones are behind NAT, there's no way your VOIP is going to work without STUN.

[bravotango]

You explain how the E61 can know the stun server but it does not explain the rest of the behavior. To pass the NAT some measure need to be taken. The SIP ALG is meant to handle that but caused other problems. When i turned of the ALG I had to do some port forwarding, I opened UDP 5060 - 65 535. It worked well like this without any contacts with the stun server for several days. Suddenly the use of the stun server started.

I did some experiments not opening all the above ports all the time. Can the the E61 change procedures depending on the state of the communications and start using stun?

[bravotango]

I have checked what is happening; it is making a DNS SRV request, finds a stun server and start using it. The reason I didn't have it until recently is most likely caused by Sipgate not having a DNS SRV record until it started.