voip and internet bandwidth usage

Our office uses cable internet - bandwidth is 200 mbps download and 20 mbps upload.  We are thinking of adding VOIP to our network - currently we use POTS lines.  We will have approximately 6-8 phone lines.  How much of an impact will that have on our users internet speed, which is a high priority since many of our users access all their files from a remote server (box.com). If it's going to slow down the internet noticeably, I don't want to do it. We will be using Cat 5e for network cable.
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I think you have your concerns placed/priorities on the wrong thing A user downloading, browsing, accessing will wait as needed.  a person placing a call should not hear any jitters, stuttering or dropped alls.

If you configure your router using a QoS to prioritize VOIP packet handling, you should not experience phone call performance issues.

each "phone" call usually consumes/need usually 62.54Kbs.
Once people start using VOIP type, going th face to face/video type calls become are made a viable option.  hey consume more bandwidth, but the current connection seems sufficient to handle at 40 of video type calls at the same time (your upload speed is the limiter)
 I think a video style call is 384kbs
martin-tadhgAuthor Commented:
But will we experience slower internet speed?

It's a high priority for the people at our company who are working on a new website - working with large amounts of programming data.  Of course I don't want jittery or dropped calls, but at the same time I don't want to compromise our internet speed for VOIP. So will VOIP have an impact on our internet speed?
Mohammed HamadaSenior IT ConsultantCommented:
It always depends on the codecs you're going to use for your VoIP solution but normally the G 711 is used when there's a PSTN gateway to your ITSP company with a gateway that has a PRI card that translates calls between data and the PSTN line.

you will have to calculate how many calls you presume there will be after you place the VoIP gateway on your premises..

You can use this website to calculate the total bandwidth that'll be consumed during the day when you have your VoIP network configured and in place.

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martin-tadhgAuthor Commented:
will we need a POE switch for VOIP?
Mohammed HamadaSenior IT ConsultantCommented:
Depends on the phones you're planning to purchase for your VoIP solution.... Some support PoE some don't.
martin-tadhgAuthor Commented:
Arnold, when you mention that the router will need to be configured for QoS - we are a one server network w/ a couple switches and a firewall. When you refer to the router, would that be the firewall or the switches?
It can be both the firewall to make sure traffic entering and leaving is prioritized for VOIP traffic, switches when can should also prioritize VOIP traffic.
Local workstation/server traffic is only seen in the switches without hitting the firewall unless you have VLANed or segmented switches..

Some phones can get power via POE (network feed) or have a separate external power source.

Mohammad pointed to the phone at hand if you have a choice, separating data from voice network is often optimal when the voice "server" is internal.

The options should be considered with all items in play

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