VoIP How Internet Telephony Works

What is VoIP?

Conventional landline telephony is retiring. Even back in 2015, across Germany more telephony connections utilized the Internet as a transport medium compared to ISDN or analog lines and since then the trend has been growing, expedited by impending ISDN shutdowns across many European countries.

So what is VoIP? Simply put Internet Telephony or Telephony over an IP network such as the Internet.

Telephony as an Internet Service

Making conventional calls directly over the Internet is not possible in that the network does not support analogue data transmissions, but rather data packed into IP packets, in other words digital data. Analysing the abbreviation VoIP reveals which trick VoIP uses in order to enable telephony over the Internet.

What Does VoIP Mean Exactly?

VoIP is a technology-centric abbreviation typical of Internet jargon. The small “o” in the middle stands for “over”. Next to it on the left, an abbreviation for the type of data stream to be transmitted (V for Voice) and on the right a foreign transport medium over which the transmission should take place. In the case of VoIP, this relates to analogue voice data which is then digitalised, fragmented and then sent packaged in packets whose form is defined by the Internet Protocol (IP), hence Voice over IP and VoIP. As such, it is now possible to transport an analogue data stream over a medium that can only transmit digital data packets. As such, VoIP ensures telephony has become one of the many services now available via the Internet such as HTTP for webpages, SMTP for e-mails or FTP for file transfers. The advantages are clear to see in that only one, single data connection to a provider is now required.

How VoIP and Internet Telephony Works

Voice over IP transmits Voice in digital form and signalling for the construction and deconstruction plus any modifications of the connections. To do so, the service uses two different channels similar in to the ISDN with the B and D channel. VoIP does not require any special solution for the data connection as existing protocols such as RTP / RTCP can be used. For signalling purposes, several solutions have been developed with the Session Initiation Protocol or SIP having prevailed as the preferred method, the current status of which is specified under the Internet RFC 3261.

What is SIP?

The **Session Initiation Protocol (SIP) is used exclusively for signalling purposes, i.e. the transmission of control information which are required when establishing new connections (sessions), modifying and deconstructing said connections. SIP is not a dedicated VoIP protocol, but rather is designed to manage multi-user, multimedia applications sessions such as audio conferences. Without session management, Internet telephony would not be possible which is why the abbreviation SIP appears frequently in connection with IP telephony, for example SIP trunking, SIP softphone (software telephone), SIP client or SIP gateways, all of which will be examined in more detail in the Voice over IP phone system section.

How Does VoIP Affect my Telephone Number?

SIP data telegrams contain information pertaining to the participants of a connection (session). These may be encoded in a form that is specific to IP telephony, which is similar to an e-mail address. To ensure compatibility with the conventional telephony network (PSTN or Public Switched Telephone Network), a supplement tot the Internet Domain Name Service (DNS) has been developed ensuring conventional telephone numbers according the ITU-T recommended E.164 format can be assigned domain names. Such assignments do not happen automatically, but must be entered by a registrar in to the DNS. However, this is only interesting if a connection should be established directly between a conventional telephone and VoIP endpoint or if the same telephone number should be assigned to different Internet services. When a VoIP endpoint or IP phone system is connected via a SIP provider, then the provider generally handles the implementation between the PSTN and VoIP technologies.

What do I Need to Know About Faxing and VoIP?

While Internet services such as HTTP (websites) or SMTP for e-mails are based on the TCP connections protocol which guarantees an orderly and complete data packet transmission, those protocols used by VoIP can also be use the connectionless UDP. This has the benefit of delivering a lower latency, but can suffer from data loss. When transmitting Voice or a video conference for example, such small data losses are hardly noticeable, whereas a low latency is a distinct advantage However, should you wish to send a Fax via IP (FoIP), the data loss often leads to disconnections. Internet compatible fax devices allow fax transmission via a real-time connection according to ITU T.38. However, this standard must be supported by both devices, sender and receiver.

VoIP and Conventional Telephony (PSTN): Further Differences

An already described benefit of VoIP is the ability to use an Internet connection instead of a dedicated telephone line. However, this does not only have benefits. Internet telephony is easier to intercept (tap) compared to a separate fixed line. Furthermore, analogue and ISDN devices can be supplied with limited power by the telephony network, meaning it is possible to make calls even in a emergency without electricity. A software telephony solution and phone system server are effectively paralyzed by power failures if no backup emergency power supply has been installed.

What happens to the Phone System when Switching to Voice over IP?

Should you wish to replace your business’ existing ISDN connection with a VoIP connection, you have three options for adapting your existing internal telephony network to the Internet age. When conducting a complete overhaul, the options look similar, but the weighting of various aspects will differ. The three keywords to know are:

Option 1: Use your ISDN PBX with VoIP

The first option entails the least amount of disruption when it comes to retrofitting, in that you continue to use your existing ISDN phone system. As long as your PBX is VoIP enabled, it is possible to connect it directly to your provider via the Internet. If not, you will require a media Gateway between your Internet connection and your PBX, which converts incoming VoIP traffic into ISDN and vice versa. As you are not replacing the phone system, you can also continuing using your existing endpoints. If IP endpoints are supported by the phone system as well, it will be possible to perform a gradual or soft migration to the newer technology, replacing older endpoints over time with IP endpoints and soft clients on desktop PCs etc.

At first glance, this may appear very attractive as this option can save significant costs. However, long-term this option is somewhat counter-productive. Legacy and ISDN PBX systems are going the way of the dinosaurs, making maintaining, replacing components and upgrading them increasingly difficult. Then there’s the fact that they are hardware, which is inherently difficult to scale. Eventually, the limit will be reached where the system cannot cope anymore and you will have to change anyway – all at once. Stay competitive and go digital as soon as possible, particularly as soft migrations are notoriously complicated and long-winded.

Option 1b: Deploy On-premise VoIP Phone System

A favourite of the small to medium sized segment IT admin who is more inclined to hardware solutions. In certain scenarios, deploying an on-premise IP PBX solution (VoIP phone system) is the ideal option. The benefit here is that you have full control over your server hardware. Moreover, this option has a number of drawbacks, namely the relatively high investment and operational costs for the server hardware.

A point worth noting here is that a VoIP phone system, just like a VoIP telephone, can also be deployed as a software i.e. virtual solution and that the same level of control can be achieved with a virtual phone system server. Therefore, it is possible to significantly reduce the cost of your new phone system if you already operate a virtual infrastructure.

Option 2: Virtual Phone System

The virtual option enables you to save the hassle relating to the installation, maintenance and operation of dedicated telephone system server hardware. With a virtual phone system, the telephony server is running in your virtual infrastructure often hosted in a Data Centre. The result is that you only need to take care of the software and configuration of the phone system. To this end, pascom offer a number of pre-packed phone system images that can be installed in a VM.

Virtual phone system solutions offer significant benefits such greater redundancy and scalability, particularly as a virtual phone system does not suffer from the limitations of hardware and can therefore be grown in-line with business growth. On the downside, you require virtualisation knowledge and specific hardware interfaces are lost. For example, ATA adapters are required for connecting analogue endpoints.

Option 3: Migrate your Phone System to the Cloud

Cloud Voice over IP phone systems elevate administration workloads by taking away the need to dedicate human resources to the updating and installing security and feature updates on your cloud phone system server. You can start making calls over the Internet almost immediately, i.e. as soon your SIP provider access is granted and the registration is successful. This option is particularly attractive for small medium businesses and startups as well as larger enterprises looking to consolidate solutions into one centralised communications platform.

Cloud phone systems are also characterised by maximum flexibility and scalability, especially when the deployment is combined with software-based endpoints such as Softphones. Simply connect a headset to your PC or laptop and utilise a desktop application such as pascom’s UC client for Window, Mac and Linux and you will save yourself significant hardware telephone outlay in terms of expenditure and administration. Simultaneously, in doing so your set up will be greatly simplified and you are good to go in a matter of minutes plus your IP telephony will be seamlessly and fully integrated into your everyday workflow.