This sounds like a case for sharing same database, and adding Path before saving incoming register. That way, no need to replicate register message to other servers and all subscribers use the same domain.

append_hf("Path: <sip:$Ri:$Rp;
received=sip:$si:$sp;lr>\r\n");
msg_apply_changes();

Whichever server receives the incoming invite, will perform lookup and automatically route to the server which received the register. On the proxying server set $du according to received param of route header, add record-route, and then t_relay(). As Daniel said, no need to re-authenticate or perform lookup again.

On Mon, Sep 16, 2013 at 7:34 AM, Daniel-Constantin Mierla <miconda@gmail.com> wrote:

Hello,

On 9/12/13 10:08 PM, Brian Wallen wrote:

I currently have two independent kamailio servers. I'd like to set them up in a way that user1 on server1 can make a call to user2 on server2. After searching I've come up with two ways that this might be able to be done. Can someone please sanity check these or point me in the right direction?

1. Have one registrar server and convert the other server to a proxy
2. Keep them both as registrars and somehow make them each aware of the users on the other server

I like 2 better because if one server went down users on the other server would still be up. The only thing is I don't know how to set the servers up to communicate with each other.

the nat can create problems when a server is down - if the nat is symmetric, only the server that received the registrar can send back calls to the phone.

Communication between users on two servers is as simple as using t_relay_to("proto:serverip:port") after you do lookup("location") and no record is found.

Suppose I have three or more kamailio servers. If a call comes in and lookup() returns that no record was found, how do I know which server to forward to? Is that a case in which I should replicate the database?

You have to add an extra check for the case the call was coming from the other server, not to forward back to it in case of no found again.

Thanks for the tip, I hadn't thought of that.

Also, you should skip user authentication for calls from the other server (not do authenticate twice). Another aspect to take care is chaining rtpproxy, you have to use the flat for trusting the other server (r, iirc).

You can also replicate the registration, but again, it can add troubles to the nat. Look at t_replicate() (in tm module).

Cheers,
Daniel

--
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Kamailio Advanced Trainings - Berlin, Oct 21-24; Miami, Nov 11-13, 2013
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