Our office is migrating to IP telephony. We have less than 10 employees that will be using the phones. We currently have cable internet, and they just bumped the speeds:

speed test

There is a data center that was just recently built in our building, and we were considering co-lo'ing there in the near future. As a result, they offered us access to their triple-redundant internet, but it's quite expensive. They are offering 3mbps committed with up to 10mbps burst for $250/month (discounted). We pay ~$120 for our cable (which the plan was to keep--at least for TV).

I want the phone system and LAN to be as separate as possible. Was thinking about keeping the cable for LAN, and using the other connection for the phones (until I saw the price). Now I'm thinking it might make sense to add on to our existing cable setup, and change our phone to only have DSL as a backup for the cable.

Is there any real benefit to the fiber? Especially for the price? Any other suggestions or ideas?



Yes there is benefit for fiber...low latency.

VoIP is prone to problems with Jitter (latency). You'll have low volume issues, dropped calls and noise on the line.

Although to support 10 users I'm not sure if you really need the fiber. Especially if you add QoS on your network...and that is a must if you do VoIP.

Lets say I would consider it a very nice to have.

  • QoS is definitely going to be part of the solution regardless of which option we go with. Is latency a result of clogged pipes, or just the way of life when dealing with cable? Thanks! – stormdrain Feb 22 '11 at 16:36
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    Latency is mostly the technology but can also be clogged pipe. In the later case, QoS should help a lot. For example, DSL access would be the worst for VoIP because phone lines are know for latency, cable is quite better and Fiber as nearly no latency (nearly speed of light). – Alex Feb 22 '11 at 16:43
  • jitter != latency. We do voip on satellite links (500ms+ but no jitter) without any problems. – petrus Mar 6 '11 at 22:56

Based on my experience, the 25/2 Mb/s will be more than enough for VoIP, including all other traffic such as browsers, mailing, skype, etc. We had no problems with VoIP with some more users and all the internet traffic.

  • Have you had issues with latency? Thanks for the reply. – stormdrain Feb 22 '11 at 16:37
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    No, my users reported that it was equivalent to a phone call, no issues there. The only problems we had were software problems ... we stopped using it because of bad software from the vendor. – rems Feb 22 '11 at 16:46
  • May I ask who the vendor was? Hopefully we haven't made the same mistake :/ – stormdrain Feb 22 '11 at 16:50
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    The name starts with Sie and ends with mens. I'm not really sure if it was a vendor problem or more the commercial and technical guy. They sold us something promising all type of features, and then they have all kind of troubles making it work and everything takes very long time to come forward, if at all. – rems Feb 22 '11 at 17:06
  • OK, good--that's not who we're going with... Thanks very much for your help. – stormdrain Feb 22 '11 at 17:08

QoS will handle most issues for preventing data from overrunning voice, to a point at least. If you can separate your data and voice, you are best off doing so, if not, you can also implement VLANs to separate data and voice traffic and limit the data more than simple QoS that an ISP implements usually allows.

Generally, when dealing with voice, you should expect that each phone will require about 100kbps both up and down while it is on a call. You will need a connection that will support at least that times the number of phones, plus a little more for overhead and even more if you intend to share with data. Therefore, with 10 phones, you should have at the minimum a synchronous connection of 1.5mbps, which would make a T1 optimal, especially as it would have lower latency compared to DSL or cable. Fiber is a good alternative as it will have lower latency as well, so compare prices and SLAs before making a decision (T1s will generally have the best SLA and uptime compared to other technologies).

If you can afford to, always keep a backup circuit of a different technology type. You can typically choose from T1/DSL, Cable, Fiber. The reason I say this is that if an outage affects one technology type, it will rarely affect the other, so you will always have something that works. T1 and DSL are essentially the same backend so do not use one as a backup for the other.

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