Intro

Because babblevoice is targeted at the business world, it is very important to us that the quality of the calls are of a high standard. There is a fair bit of stuff we have to be mindful of but some of the decisions are in your control. For those decisions we can give you some help and pointers then it is important for you to make the right decisions. Purchasing an in-appropriate Internet connection or a Firewall which is not up to the job will give you headaches and lead you to believe that VOIP is poor quality.

This is a daunting subject but once the time is spent on it, it is very simple. You have some things to consider

• The amount of Internet we use for ‘other stuff’
• The amount of people we have in the office
• The amount of people will be concurrently on the phone

Other Stuff

If you don’t know the answer to this - then it probably isn’t that important to you. There are a few things you might want to consider

• Are you hosting services for your customers/users to connect into, if so we would suggest this is not the best thing to do and placing equipment with a hosting company is a much better way to get fast reliable bandwidth which will certainly give your users a much better experience.
• Internet backup, most Internet backup is very good at setting schedules (use all your Internet between midnight and 4 am for example) and/or drip feeding it to ensure it is kept to a minimum.
• Users activity - make sure your users are behaving themselves. If it is your business connection do you want your staff downloading films/music or whatever else? Ensure you have a company policy on such things.

Calculating how much VOIP needs

There are two bits to telephone calls on the Internet (VOIP). The first is call signalling - which everyone knows by the term SIP. SIP itself does not carry any voice. This uses a minuscule amount of bandwidth. It only needs to be fast enough to give the user the sense something is happening - i.e. the same way a users tries to connect to a web site they need to see progress, but if it takes half a second or quarter of a second it doesn’t really matter.

You will realize why I mention the signalling bit in a second.

Then each voice call takes approx 80Kb for uncompressed or HD and ~30Kb for compressed. That is an active call, where both ends are talking. If you put a call on hold, or they are waiting with your phone ringing, all that is happening is the signalling bit. No voice traffic is happening.

To compress calls, which is the default on a lot of entry level phones, we use iLBC. This is enabled by default on phones such as Polycom ³²¹⁄₃₃₁. The only reason you would not be using this is if your device did not support iLBC or supports HD.

Therefore it is unlikely that an office of 2 people would ever have more than 2 active channels of voice, regardless of how many callers are waiting (on hold or ringing or whatever).

As an aside, babblevoice system in the cloud has to care about this though! It is us that plays the music on hold to your caller when you put them on hold. So we consume bandwidth, but you do not.

Now, very few offices have a all their staff on the phones all of the time. Even in busy calls centres this may only be as high as 40-50% of staff on the phone. As a basic rule of thumb, in a non-intensive office we would suggest a usage pattern of 20% - but you really must assess this yourselves.

Putting it all together

Uncompressed: bandwidth required = 80Kb x ceiling(number of users x usage ratio) Compressed: bandwidth required = 30Kb x ceiling(number of users x usage ratio) Example, I have 12 members of staff. We are typically on the phone 20% of the time. We are using phones which are capable of using iLBC. 30Kb x ceiling(12*20%) = 72Kb This is the required bandwidth for both up and down.

Other Considerations

Historically we used this to calculate how many physical bits of copper were to be installed in your building. If you installed 2 phone lines, then when you get to call 3 the caller gets an engaged signal. VOIP degrades more gracefully. So in our example above, the business owner decides to install an ADSL2 - the most common Internet connection for a small business. The smaller services typically give around 500K upload. The download maybe massive - but VOIP is what is considered symmetrical - the speed in both directions is equally important. So we take the slower of the two speeds. Transposing our equation we get: floor(500k/30k) = number of calls possible = 16 This means you’ve got capacity for 6 active calls even though you only need 3. While there are 6 active calls the Internet will slow down, but that is the beauty, babblevoice is giving you flexibility for moving requirements. You may only require 1 day a year where you need to handle a larger amount of calls than normal, the usage of your Internet simply shifts to achieve it.

Compression

This technology squashes down the data for each call. So instead of using 80K per call you only need ~30Kb. This is now the default method of voice transmission on babblevoice.