Deploying VoIP

Telephone bills, for any company, can run into a few lakh rupees to say the least. If this is the case with your company, it’s time you considered deploying VoIP. In this article, we’ll look at how to set up VoIP in a company.

The setup 

Implementing VoIP doesn’t mean throwing out the existing investments you’ve made in your telecom setup. The beauty of the system is its modularity; you can easily integrate it with your existing setup. To implement VoIP, you first need to analyze the existing network topology and geographical distribution of your offices. Other deciding factors include initial investment required, running costs, etc. 

If we consider a large or medium-sized organization, we can split the voice network into two segments: internal PBX and external connect. The internal PBX network is interfaced to the external lines, such that calls can be made from any extension to outside phone numbers. A similar topology is implemented when using VoIP devices on network. Before we discuss the actual topology and hardware, let us see how a voice call is made. Irrespective of the technology (PSTN or IP), a voice call will encompass the following event.

The call is ‘originated’. It has to be ‘carried’ from the origin and finally, ‘terminated’ at the destination. When the destination party acknowledges the call, a connection is established and the ‘billing’ starts. Let’s look at the equipment required for a VoIP setup now.

Front-end equipment

The front-end of a VoIP setup consists of IP terminals. This can be an IP phone, a ‘voice’ box or a standard desktop PC running a softphone terminal application. You can use headphones for PC based IP telephony, and would require a full-duplex sound card. IP phones are similar to analog phones as they have a similar keypad, but are more feature-rich. Of course, the difference between the two is in the technology used. While a regular phone uses electrical analog signals for carrying voice, IP phones digitize voice and carry it over IP like regular data packets. While there are IP phones that can double as analog phones (see Micronet IP Telephony products, page 70), you will need other supporting equipment to communicate with them over IP. 

A ‘voice’ box is similar to an IP telephone, except that it houses the circuitry to accept input from a standard analog phone. In this case, connect your existing analog telephone instruments to a voice box, which in turn connects to your existing data network to send voice over it. Voice boxes are readily available off-the-shelf from various vendors, and come with different numbers of input ports (two lines, four lines or eight lines). 

There are terminal applications on the desktop front you can use. These would have dial pads, and require a full-duplex sound card for operation. Simply connect a microphone and headphones to your PC, and use them to dial the telephone number of the IP address of any other IP telephony device. 

The back-end

The devices at the backend in a VoIP setup include an IP gateway, gatekeeper, voice router and software to manage and maintain the voice quality. You may need to deploy software to provide additional services like call waiting, call forwarding, answering machine, directory service, etc. The gateway interfaces your data network to the front-end devices and provides simple services like IP address to telephone number mapping. A gatekeeper stores information about the IP calling devices on network, their authentication and data on the route to be taken for a voice call. They do address translation (a phone number to an IP) and may have access control rules. Gatekeepers are linked to a directory service server to provide directory services if required. A gatekeeper can be roughly equated to a company’s PBX, but working on IP. There are some solutions (like Intel’s PBX-IP media gateway) that allow you to use your existing PBX and implement VoIP technology on them.

You would need a voice router to route voice traffic. It will take VoIP data as input, and route it over Internet through your existing gateway or over a private network. This can be hardware or software based wherein, hardware is used for small call volumes while software is used for larger ones. This is because software is scalable and capacity can be added to it easily. Schemes like QoS are implemented on a voice router to maintain quality of voice on calls. 

You may need to modify your existing gateway for interfacing it with the voice router. In case you are using a single router for data as well as voice, the splitting of voice and data will happen on the gateway. Priority rules are also defined here.

The carrier

Once a call is originated, you need a carrier for the voice traffic. It would comprise an Internet gateway, and interconnect between the origin and gateway. For simplicity, lets call it the ‘voice bandwidth’. While VSNL has been a traditional player, now, private operators are neing allowed to have their own gateways. This can even be the regular ISP you have been using for data traffic. However, ensure that appropriate service level agreements (SLA) are laid out to ensure optimum voice quality. If you’re planning to use the provider as a channel to the outside world, ensure complete end-to-end quality. Factors deter- mining voice quality are the amount of bandwidth allocated to voice (a typical toll-quality voice call needs around 16-20 kbps of bandwidth), good Mean Opinion Scores (MOS) and good round-trip times. Checks can be incorporated to ensure better ‘handshakes’. 

The carrier is responsible for ‘terminating’ your voice calls to PSTN phones abroad. For this, termination partners who take over traffic and route it to PSTN are required. They need gateways to translate network protocols to PSTN signals. However, if a voice call is to go onto public Internet in any manner (say to dial-up a PC user as the receiving party), the quality of service cannot be assured. The carrier could implement a billing system, as it can isolate voice and data traffic and hence, incorporate a billing server. With many players offering IP telephony services, at the end of the day, it is the quality of voice that matters. Hence, ask for demos and run pilots at your establishment before you decide on a solution. 

Ashish Sharma