Let’s start with the definition. Often, the term “IP-telephony” is understood as the service of cheap long-distance calls via the Internet. Indeed, the rapid development of this service has played a positive role in creating the popularity of packet telephony technology. But at the same time, it played a negative role, as it gave rise to the not very high quality of this type of telephone communication. In fact, the quality of a telephone conversation over the Internet is significantly different from the quality of a telephone conversation in the company’s IP network or the telecom operator. VoIP technology converts the audio stream (voice) into IP packets, transfers them over the IP network and performs the reverse conversion – from IP packets to sound (voice). VoIP technology assumes that an IP network “knows” that voice IP packets are very sensitive to delays, and therefore transmits them faster (in the first place) than other IP packets. The “awareness” of the IP-network about the sensitivity of audio IP-packets is realized by the technology of Quality of Service (QoS). QoS is configured by the system administrator of the IP network. Depending on whether the QoS IP network is configured, the quality of the transmission of IP audio packets will be high (similar to the quality of traditional digital telephony or even higher) or less high.
But total QoS tuning can only be implemented on an IP network with centralized management. Such networks are computer networks of the companies and telecom operators. Due to its democratic nature the Internet its QoS can not be centrally tuned: there is no single system administrator. Hence, there are cases when a call through the Internet using VoIP without the QoS is of unacceptable quality (depends on the current congestion and bandwidth of communication channels).
If voice IP packets are transmitted over an IP network with a centralized QoS, the voice quality will always be of high quality. Thus, speaking about the quality of voice transmission in IP-telephony, you should always emphasize on what network the voice IP-packets are transmitted (in terms of the availability of QoS).
There is also a nuance associated with the quality of voice. In ordinary telephony, a channel with a capacity of 64 kbit / s is allocated for one voice connection. In IP telephony, the voice stream is compressed using codecs before transmission. When G.729 or G.723 compression codecs are used, 64 Kbps can accommodate more simultaneous voice connections. Of course, this affects the sound quality, but it is not critical (for example, the quality of the audio compressed by the G.729 codec corresponds to the quality of the cellular connection). Nevertheless, in an IP-channel with a capacity of 64 kbit / s, we can simultaneously establish several voice connections, rather than one, like in traditional telephony. If to speak about higher quality of voice transmission, then IP-telephony has overtaken the traditional one. For example, the G.722 codec is oriented to a 128 kbit channel. And if you include this codec for calls on the local office network, then subscribers notice a significant improvement in the sound quality compared to even digital telephony.
So, when we talk about the use of IP telephony in the company’s office, we mean corporate IP telephony. When we talk about the service of telecom operators, we mean Internet telephony. When we think about the sound quality in IP networks, we understand that it depends on QoS and codec.
Below we are presenting some differences in the terms of usage.
Scope of VoIP technology
Internet – public
intranet network – the corporate network of the company
Purpose of VoIP technology usage
The service of international telephone communication
The way of organization of electronic communications in the company
- Participating parties
Communication operator – service provider
Subscriber – user of the service
The company is the only beneficiary of the advantages of VoIP technology
- Sound and security management
There is no one responsible for QoS and Security on the Internet
Centralized management of the company’s corporate network guarantees always high quality and network security
The options to implement the connection with the telecom operator
Let’s consider the ways to connect to a telephone operator – the types of communication channels. For small businesses, there are three types of communication channels are available: analog, digital and VoIP.
An analog connection is an old technology, but the most common in some countries. It implies the submission of one number and the ability to conduct one conversation. The digital method of connection (ISDN, E1) allows you to get several numbers in one pair of wires and conduct several conversations at the same time. VoIP is the connection to an operator of communication over an IP channel (usually Ethernet or DSL). Just like in the digital version, it allows you to get several numbers and simultaneous conversations.
According to the forecasts of the development of the telecommunications market, telecom operators follow the trend of global trends along the way of providing a telephone connection via IP-channels. In large cities, you can get a VoIP connection through the direct IP-link or through a DSL-connection. One of the main reasons for the desire of telecom operators to connect IP clients is that by using a single multiservice IP infrastructure, they can provide customers with more services in one communication channel at a lower cost. So, the request for the connection at those operators to telephony via the VoIP channel is usually lower than in the traditional telephone channel. And in terms of expanding the number of telephone lines and the cost of calls, VoIP channels allow saving on long-distance and inter-office calls, as well as saving the number when moving to another office.
Networking in the office of a small business company
Now let’s look at how the connection schemes and office equipment set for traditional and IP-telephony look like. In both cases, we need to solve the following telecommunication tasks: connection to city telephony, the creation of internal corporate telephony, secure connection to the Internet, the creation of an internal computer network.
In an office with traditional telephony, we need to have three separate devices (a telephone exchange, a LAN switch and a router), two connections to operators (telephone and Internet) and two sockets at each workplace: computer and telephone. In an office with corporate IP telephony, you need to have two separate devices (LAN switch and router – the IP telephone station is inside the router), one connection to the telecommunications operator and one socket at each workstation. At the same time, VoIP-connection to city telephony is initially multi-channel, and traditional telephone exchange often supports only analog telephone lines.
If a small company is not located in one office but in two (or even more), then, in addition to communication tasks for one office, there is also the task of combining the computer and preferably the telephone networks of two offices.
The implementation of corporate IP telephony to combine two offices allows the use of a single numbering plan and a centralized connection to the telecommunications operator. Employees of the central and additional offices can call each other by short numbers.
IP telephone station location
While connecting to a VoIP operator, a small entrepreneur can choose one of three options for placing an IP-telephony exchange (IP PBX).
The first option is based on its own system. The company uses its own IP PBX and independently manages it. You completely control the access to corporate IP telephony, but this requires you to have a trained specialist.
The second option: own system plus outsourced management. You use your own IP PBX, but you control it with the help of an external organization (for example, a telecom operator) in the format of outsourcing. In this case, there is no need to hire a trained technical specialist or send your own employee to the training.
The third option is equipment rental. You lease (get leased) a system of corporate IP-telephony from a telecommunications operator or company, which in the future will provide technical support in the format of outsourcing. In this case, physically IP PBX or its elements can be located on the technological platform of the third party company. System support is done by an accompanying company. The choice of the manufacturer of IP PBX is based on the recommendation of the company providing technical support. The technical specialist of your company, as a rule, partially manages the corporate IP-telephony system: he organizes the access to reporting forms, personal settings of subscribers, etc.
The fourth option is IP Centrex. You receive a corporate IP-telephony system in the form of a service from your telecom operator, which independently determines the scope and functionality of the proposed solution.