Tunnel questions

[cfive]

Hi,

I have two remote offices, each with about 10 extensions. Each office has the 3cx SIP Proxy Manager running on one PC, and the extensions are configured to use the tunnel.

From this 3cx web page: http://www.3cx.com/blog/releases/sip-proxy-manager/ - Using the 3CX SIP Proxy Manager - have a couple of questions.

1. Is there a practical limit to the number of extensions at a remote location that would use a single SIP Proxy Manager, running on a single PC at that location?

2. What is the significance of this "Register Expiration" setting?:

>6.In the “Register Expiration” enter the re-registration interval – it the inter-site connection is subject to stability issues, it is recommended to reduce this value accordingly. A good reference starting point is 15 minutes.

The issue is that we are having random 1-way audio issues with calls in/out of the remote sites. Some days it's perfect, some days it's tolerable (say, 5%), other days it is not tolerable (50%).

If you have the answer to the two questions above, that helps me explore that corner.

Thanks, Les.

 

[leejor]

1. Is there a practical limit to the number of extensions at a remote location that would use a single SIP Proxy Manager, running on a single PC at that location?

It would probably only be limited by the bandwidth back to the 3CX PBX when using calls with voice routed through the host.

2. What is the significance of this "Register Expiration" setting?:

The 3CX default is 30 minutes, which usually (depending on model of phone) will override the setting you have put in the set unless it is less than the time set by 3CX. This just allows the sets to "check in" so that 3Cx knows that they haven't been disconnected if it wants to "send" them a call or there is a chance that their IP has expired. 3CX assumes that the set is still registered until it does not receive a re-registration after the time out period (30 minutes). So unless the IP at the set end is changing, there is really no need to lower that to 15 minutes. It won't hurt, but I don't see the benefit.

>6.In the “Register Expiration” enter the re-registration interval – it the inter-site connection is subject to stability issues, it is recommended to reduce this value accordingly. A good reference starting point is 15 minutes.

I suppose that it depends on the definition of "stability". If you find that lowering the number helps, then there is no harm.
It's just that until the registration time expires, 3CX assumes that the set is still there and can be reached at the last IP and port it registered with. That only changes when the time expires (and no registration is received) or a call is attempted to the set and it can't be reached.

The issue is that we are having random 1-way audio issues with calls in/out of the remote sites. Some days it's perfect, some days it's tolerable (say, 5%), other days it is not tolerable (50%).

You may have to resort to something like Wireshark and hope to capture the times it fails. You may want to swap out some of the components on your network(s) to see if you can pin-point what is causing the problem. Intermittent problems are very frustrating.

 

[cfive]

Yeah . . I'd like to swap out "the internet", as I suspect the cause is external to anything in my direct control ;-).

I am going to try another ISP at one site, and see if that makes any difference. The other site doesn't have another option at this point.

I do intend to do a capture on Monday, when I have a helper at one of the remote sites. Apparently, we need to start with clean verbose logfiles, and run concurrent captures at the proxy tunnel machine and the 3cx machine, and hope to catch it in the act.

Thanks for the explanations, leejor.

- Les

 

[eagle2]

I would recommend setting a VPN tunnel (pseudo-wire, GRE) between sites using routers.
There are inexpensive and powerful solutions.

This will allow you also to solve other issues like Qos, etc.

Regards

 

[cfive]

Hi Eagle2,

But, if the connection supporting the VPN is flaky, I'm not sure adding that layer will do any good?

I'll see if I can find the weak link first.

Thanks! - les.

 

[eagle2]

The system is good as your weakest point.

If your connection is poor, there is no way to improve it by using tunnel or vice-verse a proxy-server. Proxy server in fact uses a kind of GRE or EoIP (pseudo-wire) tunnel between the proxy server and the 3cx server.

Using a suitable router you may improve the situation by implement QoS, as I assume you are using the connection not only for VoIP. Also you may achieve a kind of load balancing using 2 or more providers (links) simultaneously (more advanced technology).

Consider also using narrow-band codecs, if network capacity is not enough.

Regards