VOIP call bandwidth requirements

[gmcholland]

I need to understand how much dedicated bandwidth each VOIP call requires. I have 2mbps of bandwidth (On an 8mb service!!) and I am worried that the quality of service will be poor as I am also using b/width for normal internet services. I can dedicate bandwidth to provide a basic QOS on my router, but as it's for business I don't want to shell out on an IP phone without ensuring the calls will be professional.

[TheOtherOne]

Hi gmcholland

This article might be useful:

Important Information About Hosted VOIP

In particular this bit:

The call quality on BT Hosted VoIP lines may not match that of normal landlines. Call quality is dependant upon the available bandwidth provided by the BT Business Broadband connection and therefore can be affected by a combination of factors including (but not limited to):-

• internet traffic
• the uploading or downloading of data (particularly large files) over the same Broadband connection; and
• making or receiving of simultaneous VoIP calls

BT therefore strongly recommends that if you use a dedicated BT Business Broadband connection solely for internet voice traffic to ensure maximum voice quality.

Having said that, I have a VOIP line (I get about 2 Mb service) and it works fine, but then again I do not use it very often. Call quality should be similar to a normal landline and it's very unlikely that you or your callers will notice any difference, unless you have an unstable broadband connection.

Hope this helps,

TheOtherOne

[gmcholland]

Thanks 'The Other One',

In theory I know that VOIP only requires a small amount of bandwidth to actually function and 2mb should be ample. The problems occur if you can not dedicate the bandwidth to VOIP and it gets squeezed out by other internet traffic. If only someone at BT knew of the exact bandwidth requirement for voice packets, I could then set up QOS on my router for the MAC address of the voice device.

[Saracen]

Hi gmcholland  

On the Standard Broadband Voice service each G711 call is 80 Kb/s at the IP level but when you add ADSL and ATM overhead it brings it to approx 100 Kb/s.

On the BT Hosted Voip service each G729 call is  29.6 Kb/s at the IP level and the ADSL and ATM overhead brings this down to approx 40 Kb/s.  You say you have 2Mbps down…but  the upstream  is also important. 

It might be worth testing your upstream, to see what speeds you are currently experiencing …….........................   

http://www.thinkbroadband.com/speedtest.html  

We already  have QoS UPSTREAM  built into our Business Hub ….and using only one or 2 phones on BBV shouldn't be a problem, provided your  data apps are all TCP based.  Again, downstream will only be an issue if the data apps are heavy data streaming. If its only browsing on a couple of PCs then this  should not be an issue.

I would suggest you  try  testing the service using the  analogue ports on the Business Hub   first before committing to purchase an IP phone.

[gmcholland]

Thanks Saracen. I thought at £60 odd quid a throw I'd give it a go anyway.

I connected up the BT Falcon to my Linksys WAG54GX2 and lo and behold it initialised and provisioned my line straight away.

My first test was to make a national call, whilst a tick-over office internet useage was being utilised, and the call was crystal clear both ends.

I intend to step up the tests over the next few days (running default settings on the gateway router) and try to make a few calls whilst performing some heavy downloading file transfers. I will then mess around by setting a QOS on the router based on your voice packet requirements.

I will report back with the findings.

So far, so good.

GMP