What does it cost to make calls with a VoIP phone?

How can you make calls for free with VoIP?

The cost of a telephone call

Just in case you are wondering, you can’t buy a VoIP phone, plug it in, set it up and start calling any number you like for free. It is not that simple – in fact, when you start looking into it, the cost of VoIP calls is anything but simple (more on that later).

All telephone calls incur costs to someone – the equipment and networks that carry the calls cost a lot of money to install and the ongoing maintenance of those networks also costs a massive amount. In the UK, calls to landlines, mobiles and any other non-VoIP services nearly always involve a direct cost to the caller. The chief exception to this is an 0800 free-phone number (or similar) which is effectively paid for by the organisation receiving the call. So somebody is still paying for the call.

When you use a VoIP phone or make a call via a VoIP enabled PBX or ATA, the connection to the public telephone network will very likely be handled by a VoIP Service Provider. So generally, the VoIP phone that you have will not be able to do very much until you sign up with a VoIP Service Provider – and they will want to collect some money off you for the service. However, it is not a total myth that some VoIP calls are free.

The quality and cost of Internet access

Your VoIP phone will be good for nothing at all unless it is plugged into an IP network – preferably with access to the Internet. What is more, you will need reasonably good Internet access if you want to make VoIP calls outside the building.

A good residential broadband connection can support one or even a few simultaneous VoIP calls, but beware the variability of ADSL which may only provide quite a low speed connection if you are located some distance from the nearest exchange. Furthermore, the speeds quoted by broadband suppliers are always the best that you could hope for and they don’t make it clear that upload and download speeds are completely different – 4Mbps download may only provide 250k upload speed. VoIP requires a good connection in both directions. Then there is contention – your broadband connection may be fine in the middle of the day, but in the evening when all your neighbours and their kids are surfing the Internet, it may drastically reduce the speed of your connection.

So the first assumption you must make before you can make a “free” VoIP call is that your Internet access is only free in as much as you have already got it and you were paying for it anyway. If you have to upgrade it to get reasonable quality on your VoIP phone then you’ve already failed in your quest to make free calls!

What type of call can be made for free?

Given that you have a reasonable quality connection to the Internet and the person you want to call has a VoIP enabled phone and a reasonable broadband Internet connection, then it should be possible to make free calls. In other words, VoIP-to-VoIP calls can be free as long as you are able to tell your phone how to reach their phone over the Internet. The key to free phone calls is the address resolution – how does your phone know the IP address of the phone you are calling and how does it connect through all the firewalls and routers in between?

There are certain scenarios where the address resolution and networking problems are easily resolved. These are the cases where VoIP can really come into its own and, for business users especially, where serious money can be saved:

Businesses with branch offices or offices abroad
At the very least, the IP address for the branch or overseas office will be known. At best, there may already be a corporate data network linking the offices together. Some equipment may be required (a VoIP gateway or IP enabled small business PBX) at each office to allow correct routing of calls, but this will not always be necessary. Home based workers and very small branch offices with just a few telephones may be able to link themselves into the corporate telephone network via the Internet – possibly using VPN where this is convenient.

VoIP offers tremendous opportunities for businesses with multiple branch offices and/or home based workers. Not only can the business save money on conventional calls to customers and suppliers etc, but also the internal telephone network can be integrated across all offices allowing free calls between offices and to/from home based workers.

There is one possible “fly in the ointment” that needs to be considered – bandwidth management and QoS for voice when it is sharing the corporate data network or corporate Internet access. If all the routing equipment is within the control of the corporation and all the routers support QoS, then it will be beneficial to arrange for proper segregation and prioritisation of voice packets as they traverse the network.

Users registered with the same VoIP Service Provider
If you sign up with Sipgate as your VoIP Service Provider, you will be able to make free calls to any other person who is also signed up with Sipgate. This rule applies to (as far as I know) all VoIP Service Providers. The problems come when you are signed up with Sipgate and your friend or relation is signed up with Skype. Both are Voice over IP Service Providers, but they might as well be on different planets when it comes to inter-working.

SIP Compatible Service Providers and the rest

Unfortunately, some of the biggest players in the VoIP market chose not to go down the path of open access. To name names, Skype and Vonage have probably the largest share of the VoIP market and yet they offer the lowest level of inter-operability with other providers – this may have been by design or maybe they were early into the arena and so inter-operability was not an issue at that time. Inertia and fear of losing market share through direct competition have probably contributed to the continuation of this situation.

On the positive side, there are now a huge number of commercial organisations that offer SIP compatible services. Some of them still make it difficult (or impossible) to make free calls to users on rival services, but at least the equipment is standardised and the service has the potential to easily interact with other similar services.

Address resolution – how does your IP phone locate the phone you are calling?

As mentioned above, address resolution plays a major part in allowing users to make “free” VoIP calls. If you know the IP address of the phone you want to call, then it should be possible to add an entry into your phone’s “Address Book” (or maybe program a speed-dial button) with a SIP URI containing the IP address of the phone you want to call. That would only be practical if the other phones you wanted to call were on fixed IP addresses. It also takes for granted that your phone can reach the called phone over the network or the Internet without too many restrictions like firewalls or NAT. Of course, in practice, this will seldom be the case.

To make it easier for your IP phone to be found, it can be registered with a VoIP Service Provider. People wanting to call your IP phone then send the SIP request to your provider who, in turn, forwards it to your phone. This reduces an otherwise impossible problem to a manageable scale. Your service provider may allow you to register with them on a free account – most providers offer some kind of free account, if only as a way of tempting you to “try before you buy”. Users who are registered with the same provider will now be able to call your IP phone for free, just as you can call them for free. However, if you want to use the IP phone to make calls outside the scope of your provider’s user base, then you will probably have to open your wallet, get the credit card out and buy some call credit.

Calls between different SIP Service Providers

Let’s face it, it really is not in the interests of a Service Provider to encourage users to make lots of free calls. Their infrastructure costs a small fortune to install and maintain. They need to be connected to the Internet backbone with a high speed, high bandwidth, resilient connection with complex applications running on rack-fulls of servers with failover, clustering, billing systems, an accounts department, support department, marketing department, web sites to maintain, etc, etc – these don’t come cheap. So while the allure of “free calls” is useful in attracting new customers to VoIP, it is hardly top of the agenda with the marketing or support departments after the user has signed up for the account. As a consequence, some providers simply do not allow direct SIP-to-SIP calling to users registered with other providers. Others support it, but only through the SIP Broker interface. A small and declining number of providers allow direct calling to other SIP domains based purely on the SIP URI of the call. In the UK, the only provider I am aware of who allows this is Freespeech. In the U.S., try Callcentric because they are one of the good guys.

Open Networks, Community Spirit and SIP Broker

I only recently discovered SIP Broker. It was mentioned to me by the support department at Voiptalk whan I was trying to make calls from a Voiptalk registered phone in the UK to a phone registered with Callcentric in the U.S. The provision of this information was one of the few redeeming factors in my exchanges with Voiptalk, or more specifically their reseller Draytel, but that’s another story. In fairness to Voiptalk, they seem to be big supporters of SIP Broker and they provide PSTN access to it in the UK.

SIP Broker is owned and operated by Voxalot, but it appears to be run like an industry-wide trade organisation – various VoIP service providers from around the world either sponsor or assist with the operation. No doubt it is there to promote the use of SIP worldwide, but it does this by making SIP phone systems more accessible. It provides the links between different SIP service providers and also provides inbound connections from the PSTN to any of the subscribing VoIP providers.

Participating providers must sign up to the service – in return they are allocated a unique numeric prefix code. When you want to call someone registered with that provider, you must dial * followed by the numeric prefix code for the provider, followed by the number of the IP phone you are calling. For example, Callcentric has the code *462 and Voiptalk is *258. SIP Broker, through its network of participating service providers, is able to offer a PSTN dial-in service – you call it from any conventional PSTN landline or mobile phone, enter the prefix and number and you are connected to the IP phone registered with the selected provider. Great – and some of the numbers you use to to access the SIP Broker service are ordinary geographic numbers so they don’t cost a fortune to call and you can even use your inclusive minutes allowance on your mobile phone.

The other use for SIP Broker is that it provides the glue to join different VoIP Service Providers together. They may not support direct calls using the appropriate SIP URI, but they do allow calls to bridge across to another provider via SIP Broker. The number that you must dial from your IP phone will end up being long so it will be best to program it into a speed dial or address book entry. There will be a prefix to tell your provider that you want to use SIP Broker, then the SIP Broker prefix that identifies the third party SIP provider, then the number of the user you are calling. It’s a bit cumbersome, but it works.

If you are looking for ways to make free calls using SIP, then I strongly recommend that you take a look at what SIP Broker offers. It is even possible to use sipbroker.com as a SIP Proxy server in which case it should be possible to make calls to other IP phones direct from your IP phone without needing to be registered with a provider yourself. I tried this once from an Asterisk PBX and it worked brilliantly – the speech was clear and there was very little delay on a call between the UK and the USA.