Voice over our DSL--am I really SOL?

Discussion in '3CX Phone System - General' started by zooeyhall, Jul 18, 2008.

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  1. zooeyhall

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    I have setup two 3cx Small Business systems at two of our company's locations. Everything is working fine. I want to setup 3cx systems at our company's other 5 locations and setup 3cx to 3cx bridges between for inter-company calls. We are using SNOM IP phones.

    Each location has a DSL connection to the Internet through a local ISP. We have VPN tunnels setup between the remote locations and the home office. The primary traffic is data, and not very intensive (mostly Windows Remote Desktop connections).

    Each location has PSTN lines that they use for outgoing and incoming calls.

    We are using Sonicwall TZ170 firewall appliances at each location.

    I have setup a 3cx bridge between these locations for testing how VoIP would work for calls inside the company. If I could give it a score, I would give it about a 70 out of 100. Although it works "fairly" well, there are still considerable instances of jitter and garbled audio--especially in the mornings and later in the afternoon. This seems to point to internet traffic. I had suspected it would be as much when I first planned the system.

    I talked to our local mom-and-pop ISP, which provides internet for our main office. And basically I was told that I was SOL. That they could not guarantee priority for our Voice traffic, that's the way the internet is, "the phone companies don't want the internet to be able to handle voice calls", ...blah blah.

    We have quite a mix-and-match of ISPs for our locations. Some are using Qwest, some Time-Warner, and some mom-and-pop ISPs.

    So my question is: is what my local ISP told me true? Are there any options for a small business like ours for QOS for voice traffic? Is there anything I can do in the 3cx setups that might help? I truly appreciate any advice from anyone out there who has been in a similar situation.

    P.S> I have been told on a Sonicwall forum that you can set the Sonicwall to prioritize out-going Voice traffic. But then I have also read that the ISP disregards this prioritization, so you don't gain anything.
     
  2. SIPfun

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    If it's their connection out to the net, then you are out of luck... If it's *your* connection, I saw a device the other day at MicroCenter, that you put between your router and your "internet" modem, and supposedly it can federate your traffic...

    I'll look for the item - and post a link if I find it.
     
  3. SIPfun

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    It may have been this... if not - it was certainly like this;

    http://hardware.teamxbox.com/articles/xbox/1302/Hawking-Broadband-Booster-Review/p1/

    or on eBay;

    http://cgi.ebay.com/HAWKING-TECHNOLOGY-BROADBAND-BOOSTER-HBB1-QoS_W0QQitemZ110270057624QQihZ001QQcategoryZ61816QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    This lets you prioritize your traffic from you to your ISP... So if you only have X-Mbps, I suspect it means you can give priority to SIP or video, while having web & email take the back seat.
     
  4. BJReplay

    BJReplay New Member

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    A lot of routers will to QoS to manage your bandwidth to the ISP - I don't know the sonicwalls that you're using but as other have said, they probably will as well.

    This level of QoS is pretty basic, but usually all you need if you have a decent ISP: You specify your bandwidth (upstream is usually the key with ADSL, but if you have SDSL or limited downstream bandwidth, it can also be an issue) - for example, if your connection is 1500/256 (down / up), you specify this, and specify the traffic that is high priority based on various criteria - it can be ports / MAC addresses, physical ports on the router / IP Addresses, etc.

    The router then - in theory - ensures that the specified traffic (you VoIP traffic) gets priority at the expense of (say) your torrent downloads. So if you have two phone conversations going in G711 at approx 80kbps each, the router allows them to use 160kbps of your available bandwidth, and throttles other use to use the remaining 1340 down / 96 up.

    You're then relying on your ISP to deliver that traffic for you. If you can't get consistent speed (say to a speed test site) then you may need to look to an ISP that can deliver it.

    Proper QoS can do end to end management of priority and bandwidth, but that costs lots of bucks, and you probably don't need it if you have a decent ISP.

    http://www.testyourvoip.com/ is a good resource for identifying how well your connection will cope.
     
  5. craigbrass

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    I use SmoothWall and it does a really good job of prioritising VoIP traffic.
     
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