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VOIP / VPN -- call quality ?

Posted on 2012-03-20
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Last Modified: 2012-06-27
Do you know if anyone else has done VOIP via VPN successfully since our main concern is call quality ?

We are thinking about doing the below VOIP via VPN.

1.      Purchase VOIP PBX for each of our four locations

2.      Have user in one location (10mb/sec fiber connection) call user in another location (10mb/sec fiber connection) non-MPLS network

Below are some articles I read:

http://itknowledgeexchange.techtarget.com/channel-marker/how-to-run-voip-across-vpn-with-some-qos-assurance/

http://forums.untangle.com/openvpn/18212-voip-through-vpn-qos-issues.html

http://www.cisco.com/en/US/products/ps6120/products_configuration_example09186a008080dfa7.shtml
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Question by:finance_teacher
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3 Comments
 
LVL 71

Assisted Solution

by:Qlemo
Qlemo earned 668 total points
ID: 37744015
There are a lot of issues with VoIP over VPN (or any other tunnel technique). Some of them are:
QoS/DSCP flags are not honoured at all with the VPN packets, because ISPs are interested in managing that themselves for different services
The VPN gateway device is not able to move or apply the QoS setting of VoIP traffic to the encapsulating VPN packets
Depending on the power of the VPN device, and the used encryption and hashing algorithms, the device introduces significant lag and overhead to the VoIP packets
Only with carefully chosen devices, and ensuring to have a priorised VPN route between locations, you will have good results. It is much to prefer to have a direct VoIP connection, without applying NAT and IPSec (or SSL) encryption.
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LVL 20

Assisted Solution

by:José Méndez
José Méndez earned 664 total points
ID: 37744760
Let me share my little experience with this topic:

I was able to connect a very good quality voip call from my girlfriend's house to mine with the following components:

- Asterisk 1.8
- OpenVPN 2.2.2
- Granstream GVX3140
- 512kbps connection on phone's location
- 4Mbps connection on Asterisk's side
- Regular domestic modem/routers at each side

The call used G.711 and it was crystal clear as not even myself would believe it. Now, as Qlemo stated, it can get dirty when there are no QOS settings in place. Just image one of the locations streaming Youtube videos.... your voice clarity is most likely gone... But it is possible however, that's what I wanted to share.

HTH
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LVL 5

Accepted Solution

by:
Frank Mayer earned 668 total points
ID: 37746565
Well,
your internet access looks good. Why not first checking wether there are VoIP Providers which provide security and a virtual PBX to configure via Web eg. ? What is your interest in setting up all yourself (besides learning alot :)) ?
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