Recently, I did some test over OSBC (*dual NICs*), and I found something confused me. Because my English is not very good, so it may sounds a little bit complex.

It is about the registration procedure, the way OSBC constucting Contact header of the REGISTER that will be sent to Registrar make me a little confused.

1. Conditions:
OSBC: interface1: 172.16.0.130, interface2: 123.127.237.90
while interface2 is the public access point for users and interface1 is in the same WLAN as Registrar.

Test user: Bob
It will register with Registrar through OSBC from 172.16.0.190 first, and then it will change its interface and register with Registrar from 172.19.1.136

2. Results:
First registration:
The Contact header that Registrar see: sip:x-reg-id-sip%3aBob%40123.127.237.55%3a1546@172.16.0.130:5062
The Registration record that can be view from OSBC admin GUI: sip:Bob@123.127.237.55:1546

Second registration:
The Contact header that Registrar see: sip:x-reg-id-sip%3aBob%40172.19.1.136%3a5060;send-addr=123.127.237.39%3a13982@172.16.0.130:5062
The Registration record that can be view from OSBC admin GUI: sip:Bob@172.19.1.136:5060

3. Analysis:
Maybe it is caused by the difference between the two gateways. However, it can be found in the OSBC log files that OSBC knows exactly where the REGISTER message come from (first from 123.127.237.55, second from 123.127.237.39), then why the format of the constructed Contact header is so different?

Why I bring up this issue (maybe not an issue at all) is because this registration procedure effects the call flow. Since 172.19.1.136 is not accessible for OSBC's public insterface, it should send the SIP messages to 123.127.237.39 with appropriate port at first.

I will check the source code today, and anyone has encounter this issue, please give me any tips, it is very appreciated!

Brs

austincao