Jul 162012
Stephen
My business is moving to new premises and I keep reading about VoIP for telephone calls.
I am not sure if this is something that I should be considering.
To be honest I am not sure what VoIP is… I know it involves using the internet for phone calls, but I always thought that was Skype.
Help!
Michael Craig
Michael
I am glad you asked that question as there is definitely a lot of confusion about VoIP.
VoIP stands for Voice over Internet Protocol and is simply the term used for transmitting voice telephony signals over IP networks such as the public internet.
Confusingly the term VoIP is also used to cover transmitting voice telephony signals over private local area networks which may or may not use Internet Protocols.
To avoid any confusion I am going to keep things simple by considering VoIP over the public internet as being something different from VoIP over private networks.
The reason for this is that VoIP over a private network is something that most private networks can handle without a problem in terms of network performance, but VoIP over public network is something that requires careful consideration to ensure acceptable voice quality.
Can you tell me a bit more about the numbers of lines and extensions that the proposed phone system will need to support.
Hi Stephen
I appreciate the reply.
I am confused already!
We will have about 12 workstation which could possibly grow to about 18 in current premises.
Not sure on the number of lines… we have 6 lines and 10 workstations at current premises.
I am still not clear where Skype comes into this.
Michael
Sorry about confusion.
Hopefully things will become clearer.
Let me deal with Skype….
The Skype phone service with which you are probably familiar is an example of a VoIP service that uses the public internet. However, it is a non standard service that uses Skype’s own software on a PC, laptop, tablet or smartphone.
There is a standard for VoIP over the public internet called SIP which is implemented in VoIP phone systems. VoIP phone systems support SIP trunks in the same way that they support analogue trunks and ISDN trunks.
SIP trunks are provided by service providers who enable phone calls to be made over the SIP trunks and provide connections to the public phone network.
Skype offer SIP trunking services that can be implemented in VoIP PBXs.
Skype is therefore just one of many VoIP service providers as far as office phone systems are concerned.
Regarding your requirement for a phone system at your new premises….
The first thing I should say is that if you are considering VoIP for external calls then you will need a high quality broadband connection which can give priority for voice phone calls.
VoIP does not need a fast broadband connection, but it does need a low latency connection.
With most broadband applications latency is not a problem since it does not matter if an email arrives immediately or 10 seconds later or even 10 minutes later. Similarly delays of a second or two in the downloading of a file or the display of a web page do not really matter.
However, if there is a delay of even 0.5 seconds in voice transmission then the conversation can become unintelligible.
The other issue is that most broadband connections are Asymmetric. In other words the download speed is greater than the upload speed. This is fine for email and web browsing, but not for VoIP which requires a symmetric connection.
This means that the quoted download speed is not relevant for VoIP. it is the upload speed which is the relevant parameter.
In summary the broadband connections used by most small businesses can’t offer the quality of service required for VoIP.
To get the required quality of service it is usually necessary to spend at least £100 per month on a symmetric broadband connection which can prioritise VoIP traffic and ensure that VoIP traffic does not get transmitted with general internet traffic on its route to the VoIP service provider.
The cost of a suitable broadband connection is in addition to the cost of the SIP trunks which can be £5-£10 per trunk.
A regular analogue or ISDN trunk costs about £15 per month.
In your case you will probably need fewer than 8 trunks to support your 12 extensions.
These would cost £120 per month.
This would need to be compared with the cost of improving your broadband connection and the cost of 8 x SIP trunks.
I can’t really do that calculation without knowing what type of broadband connection you have and how much you are paying for it.
The message is that the decision on whether to deploy SIP trunks can’t be taken in isolation from your other broadband internet requirements.
In general businesses with fewer than 6 x external lines would not find it cost effective to deploy SIP trunks and should therefore not consider VoIP for external calls.
VoIP for internal calls is another matter.
An internal private local area network is usually OK for handling VoIP calls. All that is required is a router that can give priority to VoIP calls to ensure the required quality of service.
The benefit of having VoIP extensions is that it cuts down on the cabling requirement since a single cable to a workstation can support both the computer connection and the phone connection.
Many VoIP phones have an ethernet outlet for connecting another device such as a PC or laptop.
VoIP extensions can work on proprietary signalling or they can support the SIP standard. Proprietary VoIP phones usually support more features.
Another issue to consider is that one of the benefits of a VoIP phone system is that it can support off-site extensions using a VPN connection to (say) a home-office or a branch office.
Because these connections would be made over the public internet the issue of the public internet quality of service would again need to be considered.
Stephen
Thanks Stephen
I think I understand.
If I get a BT Infinity connection wold that be good enough?
M
No it wouldn’t…
BT Infinity is a fibre based service which offers very high capacity with download speeds approaching 80Mbps and upload speeds approaching 20Mbps.
However, it is still a contended service which means that many people are sharing the same internet bandwidth and that means that congestion can be a problem which affects the quality of voice calls.
Most of the time quality might be OK, but there will be occasions when calls would be unintelligible. This is not ideal for business phone calls.
I hope things are becoming clearer.
I think you are saying that I should avoid VoIP for external calls and that I should consider VoIP only for internal calls?
That’s right…unless there is another business reason why you would need an uncontended symmetric broadband connection. In whihc case VoIP could easily “piggy-back” on to that.
The use of VoIP for external calls is I think something that should only be considered by businesses that need over 10 x lines.
However, we have installed VoIP external lines over regular broadband connections in some circumstances.
In such cases we always make it clear that the quality of calls will be variable and could be unintelligible at times of broadband congestion.
Examples of such cases would be:
* overflow lines where VoIP is a low cost way of providing additional capacity to be used only at busy periods
* short term offices where the cost of installing traditional analogue and digital lines is prohibitive because of connection charges and minimum 12 month contracts
* low-cost calls to certain international destinations where the phone system is programmed to route calls to expensive international destinations over VoIP lines to take advantage of significantly cheaper call rates
It is also possible for you or your staff to use Skype from your desktop PCs and bypass the phone system completely.
I hope I have made things clearer.
Stephen