G7Eleven

Over an over again we are meeting clients that have had various VoIP phone solutions installed that are not giving them good voice quality.

This is a shame, as it only means that the client has already lost faith in VoIP phone calls before a company like G7Eleven can come along to try to convince them that, in fact, VoIP is the way forward for everyone.  Recently, to bring people back to VoIP solutions, we install a demo of the phone system so they can see the full advantage of the technology, when it is correctly configured!

Without giving away all our secrets, the soution is a simple one.    It is vital, that above all other traffic across the customers internet connection, that the voice traffic is the most prioritised above everything else!    To do this, we must “tag” each of the IP packets leaving the network to the internet as voice, and then at our router, give it the priority it requires.

However, what about when you are using a software based phone system like 3CX?    Well, then the problem is a little more interesting as you need to not only set an advanced option on the 3CX phone system, but you also need to tell windows to allow the header tagging by a registry edit as it disables it by default.

First, set 3CX to tag the packets leaving it with a number you decide.   In our case we always use 47.   Once you have done this, you need to add a registry setting on the 3CX server….

• Open the registry editor: regedit.exe
• Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
• Create a new DWORD value called “DisableUserTOSSetting” and give it a value of 0 (zero)
• Reboot your server.

Example of Queue Control on MikrotikOf course, the configuration of such a thing is completely dependant on the phone system and phones you are using. For instance, if we have a client that has only one or two Linksys SPA phones connecting directly to our VoIP hosted SIP trunks, then the good news is that the Linksys phone has already tagged the DSCP field (in the IP header) with the number 46. Because of this, on the Mikrotik routers we install we can prioritise the traffic from all phones plugged into the customers LAN going out via our gateway router.

Now you can configure your router to prioritise the packets with the TOS/DSCP number you set in 3CX.

Of course, there is much more we could go into here, but we would end up with a seriously long blogpost!

Simply put, G7Eleven can provide you with the skills necessary to get this working in your company!

EDIT 20-01-2010:

Please note that this method only works on Windows XP based 3CX installs.   Vista, Windows 7 and Windows 2008 server use a completely different method and therefore will not work.   G7eleven have an open case with 3CX to support the newer methods, and will update with a new blogpost if and when we hear anything.