VoIP for business: how it works and how to get started

What VoIP is, in plain terms

VoIP stands for Voice over IP: your voice is turned into data and sent over the same internet connection you use for email and your business software. Nothing changes for the people who call you: they dial an ordinary number and hear your voice. What changes is everything on your side: you no longer need a physical line for every number and every desk.

For a business this brings three practical advantages. First, cost: you pay for the conversation, usually per second, instead of a monthly fee for every line. Second, freedom of location: an extension works in the office, at home or on the road, as long as there is a connection. Third, speed of change: adding a desk or changing where a number rings is done from a portal in a few minutes, with no engineers and no cabling.

If you are still deciding whether to give up your traditional line, also read the comparison VoIP or traditional phone line: it explains what you gain and what you need to plan for, such as keeping the router powered during a power cut.

How a VoIP call works

A VoIP call uses two separate channels: one to set the call up and one for the voice. Understanding this distinction lets you solve most problems yourself, because almost every fault comes down to one of the two channels not getting through.

SIP: the signalling

The SIP protocol (Session Initiation Protocol) is the language your device and the provider use to talk to each other. It does not carry the voice: it decides who is calling whom, which audio codec to use and on which ports the sound will arrive. With Vohippo the SIP server is sip.vohippo.com on port 5060 UDP.

An outbound call always follows the same sequence of messages:

1. Your phone sends an INVITE with the number to call and the codecs it supports.
2. The provider replies 100 Trying (working on it) and then 180 Ringing when the phone at the other end rings.
3. When the other person answers, a 200 OK arrives and your phone confirms with an ACK.
4. From this point the audio flows, on the other channel.
5. Whoever hangs up first sends a BYE, and the call ends.

RTP: the voice

The voice travels over RTP (Real-time Transport Protocol), in small packets that each carry about 20 milliseconds of audio. On our platform the audio uses UDP ports 10000 to 20000. If SIP works but a firewall blocks RTP, the symptom is typical: the phone rings, you answer, but you hear nothing or the audio only goes one way. The guide on NAT, firewalls and ports explains how to fix it.

Registration

A phone or PBX registers with the provider: it says «I am this account and you can reach me at this address». The registration expires and is renewed: we recommend an expiry between 300 and 600 seconds. Without a valid registration the provider does not know where to deliver inbound calls.

The building blocks: SIP accounts, SIP trunks and numbers

Whenever VoIP comes up, you meet the same three things. It is worth being clear about what each one does, because they are bought and configured separately.

A SIP account is like a line: it has a username, a password and its own rules (how many simultaneous calls, how much it can spend, which countries it can call). If you already have a PBX, you connect it with a SIP trunk, which is simply an account designed to carry many calls at once. Virtual numbers are the inbound side: a number with a city's area code that rings wherever you decide.

For outbound calls there is also the caller ID, the number shown to the person you call. It can be a number bought on the platform or a number of yours from another provider, once verified: all the details are in the guide on caller ID.

What you really need to get started

Far less than you might think. You do not need proprietary equipment or a dedicated line contract and, in most cases, you do not need an engineer.

A stable connection

Stability matters more than bandwidth. A call using G.711, the most common codec, uses about 100 kbit/s in each direction, so even a modest fibre connection can carry many conversations at once. What ruins the audio is lost packets and variable delay, typical of a crowded Wi-Fi network or a connection saturated by a backup running during the day.

Vohippo accounts support G.711 a-law, G.711 µ-law and G.722, the latter with wideband audio that sounds more natural. The guide on VoIP codecs explains when to choose each one.

A device that speaks SIP

You have four options, and you can mix them in the same office:

• Desk IP phones: Yealink, Fanvil, Grandstream, Snom, Cisco. Instructions are in the guide on VoIP phones.
• A softphone on your computer, such as Zoiper or Bria: see set up a softphone.
• The web phone in your browser and the Vohippo app for iPhone and Android, which use the same SIP account.
• An IP PBX such as Asterisk, FreePBX or 3CX, connected with a trunk.

The right router

Many routers have a feature called SIP ALG, which tries to «help» SIP by rewriting its messages and often breaks them. Our advice is to turn it off: our platform already handles NAT issues on the server side, that is, the translation of addresses between your internal network and the internet.

What VoIP costs

The cost of VoIP telephony has three parts: outbound traffic, the fee for your numbers and any extra services. Inbound calls to your numbers are usually included in the number's fee.

Per-second or per-minute billing

The biggest difference between one offer and another is how call duration is rounded. With per-second billing you pay for the seconds you talk; with per-minute billing every call is rounded up to the next minute. Here is how it works with a hypothetical rate of €0.03 per minute (not a price from our rate list):

On a handful of calls the difference is negligible; on thousands of short calls (think of a call centre or a debt collection team) it becomes a line in the budget. Also watch out for a connection fee, a fixed amount some providers add to every call.

With Vohippo calls are billed per second, with no connection fee on listed destinations, with rates to 233 countries; you will find everything in the rate list. Prices exclude VAT and you pay with prepaid credit, topped up by card, PayPal or bank transfer.

Be wary of bundles with a monthly fee

«Inclusive minutes» bundles look convenient, but they are simply the per-minute price multiplied by the minutes included: if you use fewer, you have paid for the leftover minutes anyway. Before signing, work out how many minutes you really use, month by month, and compare with pay-as-you-go rates.

Extra services

A good provider states the price of every service. On our portal, for example, call recording costs €0.02 per answered call, each simultaneous outbound channel beyond the first costs €0.50 a month, and an Italian geographic number costs €23.48 a month or €109.83 a year, inbound calls included.

The most common mistakes (and how to avoid them)

The same mistakes come up in almost every business that moves to VoIP. None of them is hard to avoid, but some are very expensive.

1. Weak passwords on accounts. This is the entry point for nearly all toll fraud: someone guesses the password, registers a device and calls expensive destinations. Use long, randomly generated passwords, a different one for each account.
2. No spending limit. One night of fraudulent traffic can cost months of normal bills. Set a daily spending limit and a maximum per-minute rate on every account.
3. All destinations open. If you only call Italy and a few European countries, enable only those. The rest of the VoIP security guide builds on this.
4. Phones on a crowded Wi-Fi network. Use a cable for desk phones; if Wi-Fi is the only option, put them on a network separate from the guest one.
5. SIP ALG left on in the router. It causes calls that drop after 30 seconds or one-way audio. Turn it off and try again.
6. An unverified caller ID. Without a valid, authorised number the outbound call is rejected: there are no anonymous calls. Verify the number before you start.

Choosing where inbound calls ring

VoIP makes something simple that used to require a PBX with traditional lines: deciding where each call goes. For each number you build a step-by-step route: first the office accounts ring, if nobody answers the call goes to a mobile, and finally to voicemail with the message sent by email.

There are nine modules to build the steps, from the AI secretary that answers and takes notes, to voicemail and forwarding to another number. The guide on call routing modules describes them one by one, while the one on how to set up an inbound number walks you through the first configuration.

Getting started: the steps in order

This is the sequence we recommend for a professional firm or small business, for example an office with four people and a reception desk.

1. Sign up on the portal at cloud.vohippo.com/register and verify your mobile number.
2. Top up your credit: a few euros are enough for testing, as traffic is billed per second.
3. Create a SIP account for each desk, with a strong password, and straight away set a daily spending limit and the allowed countries.
4. Configure your devices: IP phone, softphone or app, with server sip.vohippo.com and the account's username and password.
5. Choose a number from those available in the virtual number search and upload the documents required.
6. Build the number's routing: for example, ring all accounts together for 30 seconds, then voicemail.
7. Make a test call outbound and one inbound from a mobile, and check the audio in both directions.

If you already have a PBX, at step 3 create an account to use as a trunk and follow the guide for your system, for example SIP trunk on 3CX or SIP trunk on Asterisk. If you have questions about a particular setup, you can contact us.

Frequently asked questions