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Getting rid of / reducing Jitter

By Levi_L ·
I have a remote location that is on Time Warner Cable's Business Class Road Runner product. I have a VPN setup between their location and my location via our Adtran NetVanta routers.
We are running VOIP over the VPN to provide that location with voice services.
We seem to be experiencing a lot of Jitter over the VPN. I have setup QOS in the router to give voice traffic priority, but that didn't seem to help.

Anyone have any ideas on how to remedy or improve the situation?

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Connection

by Brenton Keegan In reply to Getting rid of / reducing ...

What's the situation on connection speeds and media types?

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We have enough

by Levi_L In reply to Connection

bandwidth to suffice the connection. At the main site we have a 3mbps up and down fiber connection, and at the remote site we have a 10x1mbps cable connection.
We have adtran routers in place at both locations and are using traffic shaping to limit the outgoing traffic to 1mbps at the remote location and 3mbps at the main location (so we don't overwhelm the pipes).

Not sure what you mean by media.

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Cut down on your caffeine intake

by robo_dev In reply to Getting rid of / reducing ...

but seriously....

http://www.voiptroubleshooter.com/indepth/jittersources.html

In terms of testing things, I would first measure how the ISP is doing from cable-modem to cable-modem end to end.

If it's the ISP who is at fault, then they're the only one who can fix that.

Not to answer a question with a question but, I would assume that those cable companies who offer VOIP must do QOS with their own voice traffic?

Several years ago I was running Vonage on a Cable Modem and I swear that the ISP was purposely borking the Vonage traffic while trying to sell you on their VOIP service.

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Couple of things

by Levi_L In reply to Cut down on your caffeine ...

First off, I have been doing some testing. I have been noticing some packet loss over the VPN.
I was looking into it all day yesterday to try and figure out what is causing it.
I finally spoke with our main site's ISP, and have discovered that we are maxing out our down pipe, so the VPN would not be able to be sustained. So i am currently working on limiting the bandwidth that each user at this site can use, to hopefully reduce our pipe-usage and fix that issue.

As for your question on QOS:
I am running a VPN, so my guess would be that the ISPs would not even see the VOIP traffic (although I could be wrong), but even if they did, it doesn't seem like they would offer me the service (at least Time Warner wouldn't).

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Technically you can do QOS on VPN

by robo_dev In reply to Couple of things

You can do QOS over VPN, but you are only managing your own traffic. Effectively it is QOS within the VPN...as the ISP cannot identify/tag different packets within the VPN, as that would defeat the security
of the VPN. But it would help to make sure your less important traffic over the VPN does not affect the VOIP.

http://www.ciscoblog.com/archives/2007/04/qos_over_vpn_tu.html

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I have that setup

by Levi_L In reply to Technically you can do QO ...

What I was trying to convey, was that the ISP wouldn't be able to setup COS, as the packets would be encased in the VPN. I have QOS setup on each of the routers, giving voice traffic priority.

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Forget VPN!

by petike222 In reply to I have that setup

VPN is very bad and ugly solution for voip unless used on a LAN.
If you need security, try to use some encryption solution which can encrypt the media packets (over UDP) one by one. For example SRTP or proprietary solutions. Search for "voip tunneling" to see some resolutions for this problem.

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