What is ip pbx. PBX for LAN telephony. Possibilities of virtual PBX for business

First of all, it is distinguished by its focus on a small number of serviced numbers (usually no more than one hundred or two hundred), the division of the telephone network into “internal” and “external”. Depending on the type, it can receive a digital stream, analog lines or via switched networks (IP telephony) from telephone operators. Subscriber devices are usually analogue phones, digital phones or IP phones. Using a PBX allows you to avoid connecting each subscriber device (telephone, modem, fax) of the organization to the public telephone network, which would lead to the allocation of a separate line to each subscriber device (usually paid monthly), and all “internal” calls would go through the PBX telecom operator.

PBX equipment is usually installed on the premises of an organization and switches calls between internal subscriber lines. Additionally, a limited number of trunks to the public telephone network are usually available for external incoming and outgoing calls. Organizations located in several buildings can use trunk lines (CO, from Central Office) to connect their own PBXs. Connecting lines are usually analog or can be digital (E1, BRI). The latter, unlike analog ones, are capable of processing more than one connection and receiving calls to several city numbers - DID.

Sometimes the English abbreviation is used to refer to PBX PBX(short for P rivate B ranch e X change - or P rivate B business e X change), as well as PABX(from P rivate A utomatic B ranch e X change).

The main difference between a production PBX and a city telephone exchange ( GTS) are:

the ability to provide fully accessible traffic switching schemes (communication without blocking);
intelligent call distribution systems for subscribers or operators;
the enormous volume of subscriber services provided (for example, Avaya PBXs provide over 800 telephone services);
support for built-in CRM subsystems and developed SDK systems for integrating telephone subscriber services into automated systems;
ensuring the provision of subscriber service packages regardless of the location of the subscriber and the method of his connection to the telephone network (mobility);
high reliability and flexible redundancy system ensuring 100% continuity of telephone communication.

PBX allows you to save money for an organization and reduce communication costs, since when using a PBX, internal calls within the organization are free, the connection establishment time is extremely short, since three-digit numbering is usually used, and each organization can program its PBX to suit its needs, distributing it among employees the right to access the city, the organization’s existing city lines, setting up voice menus, etc.

Large corporate telephone networks are built on the basis of PBX for government and financial institutions, transport management systems, medical institutions, etc. Programming an office PBX is carried out using a system telephone, or using a special program connected via the port (interface): RS-232 ; USB ; 10BASE-T. You can usually set a password to enter the programming mode so that unauthorized persons cannot change the specified operating algorithm of the mini-automatic telephone exchange (PBX). Such a system telephone should be installed at the secretary or at the secretary and director, however, if the mini-PBX has a sufficient number of expansion cards that support system telephones, such devices can be installed by everyone.

The capabilities of the PBX are determined by its configuration. For example, you can equip a station with as many analog subscriber cards as possible in order to achieve maximum capacity, or you can give priority to city line cards. In addition to these types of boards, there are many other boards, for example, an auto attendant board, a voice mail board, a modem board, a board for connecting a music source, and so on. Different PBX manufacturers may have very different station configurations.

Main functions

Subscriber switching within the office telephone network.
The ability for subscribers to make calls to the city (usually with the addition of “9” before the city number), that is, the organization of interfacing with the public telephone network (PSTN).
Receiving landline calls and directing them to specified internal numbers (see also DISA)

Types of office and institutional PBXs

Traditionally, telephone exchanges are divided by type of switching and by the number of connected telephone lines (capacity).

Based on the type of switching, analogue, hybrid and digital PBXs are distinguished. Currently, various manufacturers produce stations of all three types. Analog stations have the lowest port cost. Hybrid PBXs differ from digital ones in the way they switch the signal. In digital telephone exchanges, the voice signal of the tone frequency is converted into a coded digital electrical signal (having only two logical values: “0” and “1”). These signals are then switched. In hybrid PBXs, a “non-digitized”, that is, an analog electrical signal of a voice frequency without conversion is switched. At the same time, the control programs of hybrid PBXs are similar to those used in digital PBXs. The user interface may be the same, and in some cases the station subscriber will not even feel the difference between a hybrid and digital PBX. The term "hybrid lines" means that both system and analogue telephones can be connected to such lines.

With the spread of the IP telephony standard, IP PBXs became widespread.

By manufacturer

Additional features

Reserving telephone communications from several operators (if communication with one operator is lost, the lines of another are used).
Call forwarding based on busy signal, no answer or unconditional, depending on the time of day and other conditions, that is, drawing up call processing scripts or dialplans.
Transferring a received call to another subscriber.
Picking up the handset for another subscriber (call interception).
Priority calls.
Additional dialing of internal numbers for incoming connections (DISA).
Group call, call center organization
Serial search - selection of a free trunk for outgoing connections.
Automatic change of guidance table depending on time and day of the week.
Notifying the subscriber about a hung up call (loud signal into the handset some time after hanging up).
Speakerphone, reception and broadcast of civil defense and emergency signals.
Control

1. IP-PBX: what is it?

In recent years, almost all leading manufacturers of switching equipment have released office PBXs ( PBX, Private branch exchange or Private business exchange - office PBX or mini-PBX) with the ability to transmit voice over data channels, including via the Internet using the SIP protocol ( Session Initiation Protocol - session establishment protocol). They began to be called IP-PBX (IP-PBX).

SIP(English: Session Initiation Protocol - session establishment protocol) is a technology that allows you to carry out a telephone conversation over the Internet or a local enterprise network. When using this technology, a direct point-to-point connection is established between subscribers. Thanks to SIP technologies, you can make video calls.

Conventional office PBXs use circuit switching technology: when receiving a call over a copper line, the PBX switches it to internal numbers in the office. IP-PBX uses packet switching technology, i.e. a call to the PBX arrives via a data network channel and is then redirected to a special phone that supports a SIP connection. As a SIP phone, you can use not only a landline device, but also a softphone (SoftPhone) installed on a computer or mobile phone. The latest models of smartphones with the Android operating system already have built-in support for receiving and making calls using the SIP protocol.

2. Scope of IP-PBX

The emergence of IP-PBX is associated with the rapid development of computer technology and the emergence of corporate data networks and, as a consequence, the demand for equipment that allows the use of the same communication channels for the transmission of voice traffic, data, fax messages and video information. Modern IP PBXs convert speech into standard IP packets and send them over a communication channel, where they are transmitted along with data packets.

IP packets- these are blocks of information transmitted via the Internet or the enterprise’s local network.

Thanks to the use of Internet channels for transmitting voice traffic, connecting an office PBX has become only a matter of setting up authentication data on the side of the telecom operator and the subscriber who has an IP-PBX installed. Moving away from traditional wires also allowed subscribers to painlessly change rented premises because... When moving from office to office, the organization's existing numbers are retained, and to connect a PBX, all that is required is the presence of an Internet channel.

If you use an IP-PBX in a company to organize telephone communications between several offices, you can significantly reduce the costs of using channels from fixed-line operators. Connecting several PBXs via IP channels is usually cheaper than via other protocols (ISDN BRI, PRI, E&M and others). Also, thanks to the use of IP technologies, subscribers of a modern PBX can be located outside the office, connecting to the office PBX from anywhere from any device that supports voice transmission using the SIP protocol.

3. Advantages of IP-PBX (IP-PBX)

Virtually unlimited number of lines and subscribers- unlike conventional office PBXs and mini-PBXs, which have a maximum capacity of external lines or internal ports, IP-PBX can expand almost unlimitedly, and both external lines and internal subscribers can be connected in various ways;
IP PBX allows unite the company's divisions and branches into a single telephone network located in different places (different city or country), while all subscribers, regardless of their location, will be subscribers of one PBX, which will make all calls between branches free;
With IP PBX you can organize an interactive voice menu (IVR) or the so-called “intelligent secretary”, with the help of which you can process incoming calls automatically;
IP PBX provides all the functions of modern corporate PBXs- call forwarding (according to various customizable rules), call hold, call interception, group call, etc.
Various call forwarding options both between internal subscribers and to mobile phones of employees who are outside the office;
Centralized call recording on the IP-PBX server allows you to save information about all conversations carried out;
Conference calling- conferences with the connection of both internal and external subscribers;
Ability to install restrictions on making long-distance or international calls for various groups of subscribers;
The system is easy integrates with CRM systems, databases, etc.;
Based on IP-PBX you can organize call center(call center or contact center);
IP-PBX allows you to organize a system automatic fax reception and forwarding to e-mail Possibility to organize a voice mail system;
Manager IP-PBX interface is accessible via a web browser, which ensures ease of control and changing the necessary parameters;
Implementation possible on the basis of IP-PBX video telephony systems, which will allow employees to communicate not only by voice, but also provide visual contact.

In addition, based on IP-PBX you can organize unified communications system(unified communications), which will allow your company's employees to always stay in touch.

4. How to choose an IP PBX? Criterias of choice

An IP-PBX has a packet switching function, which means that such a PBX is a small computer with its own operating system, processor and memory. As a rule, an IP-PBX has a special version of the Linux operating system installed with a proprietary software package that provides call management and additional services. As a rule, Asterisk software PBX is used.

Asterisk is a full-fledged software PBX. It can run on operating systems such as Linux, BSD, Windows and OS X and provides you with all the features that a regular PBX has and even more. The functioning of Asterisk is based on protocols that provide voice transmission over networks based on the IP protocol (Internet Protocol) and, thanks to this, this PBX can work with almost any equipment for IP telephony that uses standard protocols for VOIP, while using a relatively inexpensive Hardware.

Thus, the main thing you need to pay attention to when choosing an IP PBX is its performance. The performance of stations operating on the basis of packet switching technology is determined by the number of simultaneous connections. This determines how many people can talk on the phone at the same time.

You also need to pay attention to the size of the memory installed in the IP-PBX. The number of saved minutes of voicemail and recorded conversations will depend on the memory capacity. If there is a shortage of it, old recordings of conversations and voicemails will be deleted.

What is Asterisk IP-PBX, how it works, use cases and prospects

O. Tereshchenko

Today, buying a regular or digital PBX for a small office or call center is not profitable. Traditional telephony has been replaced by IP telephony, which is characterized by low call cost, ease of deployment, ease of configuration, scalability and connection security.

IP PBX is a telephone exchange that provides voice transmission over the Internet (based on the Voice over IP protocol).

In this article we will talk about IP telephony organized on the basis software IPATS "Asterisk».

IP PBX Asterisk today is the best solution for organizing office telephony and an inexpensive call center. This is an Open Source class software product - free open source software. Due to its unique combination of many functions, Asterisk occupies a leading position among platforms for creating office telephony. Price also plays an important role. The cost of office IP telephony on the Asterisk platform is several times lower than the cost of solutions on traditional IP PBXs - Panasonic, Samsung, etc.

Hardware

Asterisk supports any equipment for Voice over IP (VoIP). Devices from various VoIP equipment manufacturers can be connected without any problems.

Functionality

Asterisk has all the capabilities of a classic PBX, supports many VoIP protocols and provides functions of voice mail, conferences, interactive voice menu (IVR), call center (queuing calls and distributing them to agents using various algorithms), CDR recording and other functions. Asterisk has no restrictions on the number of subscribers, channels and functionality.

To create your own functionality, you can use the Asterisk language to write a dialplan. Today, many graphical web shells for Asterisk have already been written for ease of use and ease of perception.

Implementation

1. Let's start with the fact that Asterisk is installed on Linux.

The first question is which implementation option to choose. Actually, the main choice is “flat” Asterisk, controlled through the command interface (using the command line),

or the Asterisk system with a Web interface (as already mentioned, a sufficient number of them have been written).

The first option offers more flexibility and greater capabilities, while the second offers easier setup and management.

For office tasks and small business tasks, the implementation of complex logic is not important. Therefore, here we focus on building a simpler system designed to service up to 100 internal telephones with multi-channel input lines from one or more telephone operators.

2. Second practical question, which needs to be solved - which platform to choose to use Asterisk. There are two options: local server or “cloud”?

A local server for an IP-PBX in modern conditions can cost almost free: let’s say you have old (or not very old) computers. All you need is: 2 GB of RAM and one processor (you can even use an old and not very powerful one).

But - attention: if the old computer is completely junk... Then such a server can let you down, failing at the most inopportune moment. And then the effect of saving the company money may be completely opposite.

Today, the cost of a computer system unit for deploying an IP PBX in an office does not exceed $200.

So, the issue with the server is either resolved, or we are heading “to the clouds”.

Virtual PBX

An obvious advantage of the cloud is that the cloud provider is responsible for the reliability of operation and there is no need to spend money on a server. The monthly fee for a virtual “server” with one core and 2 GB of RAM will not be high: about 1000 rubles (or even less). You can also use a cloud PBX (the operation of a virtual server and a cloud PBX has a slight difference).

A little about the pitfalls of a virtual PBX

Telephony operators offer different conditions for using their cloud PBXs. There are restrictions. These may be restrictions on the number of internal numbers, various functional features. For example, not all such systems provide the ability to record conversations, not all types of IP phones are supported, and sometimes the quality of communication suffers.

There is a set of restrictions that are common to virtual PBXs of all telephone operators. It is as follows: virtual PBXs do not allow simultaneous connection of other telephone operators or switching to another operator. Therefore, you will not be able to optimize costs by automatically selecting tariffs for specific connections, or use another operator with your current virtual PBX.

Those. a telephone operator, using his virtual PBX, can initial stage to provide solutions to telephony issues. But this will pose a serious barrier to the further development of your company’s communications.

It is also worth paying attention to the situation in which one internal subscriber needs to call another internal subscriber. In this case, the conversation between subscribers will take place in a “large circle”, that is, from the device of internal Subscriber 1, the signal will pass to the office router with access to the external network (on which the corresponding ports must be open, which in turn increases the “attack area”, since it is required to open SIP ports for each device), go to the virtual IP-PBX server (cloud PBX), located in a certain data center, after which it will return to the original router and from the external line will be sent to the internal one to the device of internal Subscriber 2. Long way isn't it? What if there are more than a dozen such connections?

Security may become an issue because one internal user will be exposed to the external network while talking to another internal user. Such a structure is often hacked and calls are “pumped” through it, say, from Nigeria to Palestine - to expensive paid numbers, and through all available channels. Your company can lose a huge amount overnight, and it’s good if the telephone provider has introduced restrictions for such cases, then the losses will not be so significant. In general, any SIP port visible on the Internet (the need to open which I spoke above) is subject to attacks within a few minutes of its appearance, so security issues must be worked out carefully and professionally, since the more ports are open, the larger the “attack area.”

In this case, the “traffic” passing between internal subscribers must be encrypted, since in this option all conversations between internal subscribers will not be difficult to listen to (intercept).

IP-PBXcusing the server

If you use “your own” server (located within the network), the picture will be different.

Own server:

Minimizes the “attack area” (since it reduces the number of open ports);

Allows you to eliminate the very possibility of listening to (intercepting) conversations of internal subscribers or connecting to a third party on behalf of the internal subscriber, even if there are remote offices (since internal subscribers talk to each other without going to the “external network”);

A Virtual PBX can be used to create and modernize a corporate communication network. With its help, it is easy to build and optimize all communication processes for business.

Based on a Virtual or mini-PBX, you can combine all communication channels into one: from regular calls and notifications about requests from clients and partners in instant messengers to creating automatic tasks in an integrated CRM or ERP system.

The advantages that IP telephony provides for the office:

line availability for receiving and making calls;

the ability to connect an unlimited number of internal numbers for employees free of charge;

the ability to use both a regular telephone network and an IP-based connection to connect subscribers;

high quality and stability of communication without connection breaks, noise, interference and other defects that may interfere with comfortable communication;

advanced functionality of a virtual IP PBX, especially when using the integration of virtual telephony with customer relationship management systems (CRM and ERP), not to mention traditional tasks (receiving and sending faxes, saving conversations and forwarding calls);

no connection to the location of the office;

the ability to connect dynamic call tracking to track advertising effectiveness.

* - uninterrupted communication operation is guaranteed when routing calls only through our company’s networks (without transitions to/from partner networks) and in case of force majeure.

Cloud PBX - reliability and innovation

Cloud telephony is a modern platform for companies with any staff, including remote employees (working outside the office). Enjoys great success among businesses in Moscow and other Russian cities.

A virtual PBX is a full-featured telephony service, the technical basis of which is based on the duplication of all infrastructure elements, which guarantees uninterrupted operation and preservation of data, including call records. Optimal cost, the ability to integrate with other business tools and expanded functionality make it possible to use an innovative product every day.

You can use a cloud PBX in the office without any phones at all - just a computer or laptop connected to the Internet: all resources are actually located with the provider. The number will also be virtual, that is, without connection to the office. You can connect and configure Virtual PBX completely remotely.

Connection in 3 hours

The selected number will become available for receiving calls immediately after the conclusion of the contract

No link to address

No wires, no hassles with moving or opening new points of presence

Favorable rates

Connecting a number from 0 RUR, fee for a number from 250 RUR/month, minute of conversation from 0.42 RUR.

High reliability

The UIS communication infrastructure guarantees stable operation - no more than 15 minutes of downtime per month*

Easy connectivity options

It’s easy to connect and disconnect functionality and pay only for the tools and features you use

Technical support 24/7

And a personal manager for convenient work with telephony, Virtual PBX and other tools

Possibilities of virtual PBX for business

Online stores

Automation of order processing

Call centers

Operator control and call distribution

Service companies

Tracking all stages of interaction with clients

Financial organizations

This is an excellent solution for companies that value mobility. IP telephony can work from anywhere in the world and does not require changing your phone number. Cloud telephony allows you to make any settings up to the scenario of selecting a specific operator when specified conditions are met in your Personal Account, which makes the Virtual PBX a very flexible tool that adapts to any needs and tasks.

Connecting smart telephony from UIS allows you to use various tools: a call from a website (sitephone), a lead generator and an online consultant. With their help, the company can provide customers with additional communication channels. Connecting a Virtual PBX is an important step for business growth.

Computerization has affected traditional telephone communications, and the pairing of traditional private branch exchanges (PBXs) with access to the city, long-distance and international telephone network with a personal computer significantly changes the face of modern telephony. However, most modern offices still use separate wiring for telephone and computer networks, which is not always convenient and, in addition, makes it difficult to access telephone communications when working with various applications. Therefore, various systems have emerged that allow the joint operation of telephone and computer networks on the same wiring - telephone or computer.

LAN telephony is understood as such an organization of telephone communication in which in a building that has a local area network, there remains (in addition to power) only one signal wiring - either computer network (for example, Ethernet) or telephone. In this case, both computers and telephones are connected to the same sockets.

To organize telephone communication in these conditions, alternative PBXs (also called pseudo-PBX or un-PBX) are used - these are PBXs based on personal computers (PCs). Those un-PBXs that use the same signal wiring to carry telephone signals and data can be classified as LAN telephony PBXs.

Systems of this class are usually divided into the following three main categories:

Distributed LAN-PBX. These systems consist of several elements: telephone servers, gateways and telephone switches.
Integrated communication systems (all-in-one-box) are specialized devices with built-in OS and application software.
PBX with IP gateway – traditional PBX in which IP gateway cards are installed to organize IP communication.

Companies took different routes to LAN telephony. Those involved in the supply of equipment for computer networks offered so-called distributed solutions that did not require the presence of a PBX in the office in the usual sense (Cisco, etc.). Companies specializing in the production of traditional PBXs have begun to equip them with IP gateways - boards inserted into those PBXs that are already produced and in operation (solutions from Avaya, Ericsson, Siemens, Alcatel, Samsung, etc.). These same companies began offering integrated communications systems.
All of these systems are based on common signal wiring and have centralized intelligence concentrated in the core of the system - the server or PBX processor.

Distributed systems

In LAN telephony systems with distributed switching, the switching process is carried out in the local network. All such systems contain switches, IP phones, gateways, and voice packets in them do not necessarily go through the central core; packets receive authorization and route from the intelligent core and are forwarded to the phone or gateway. In such systems, the principle of distributed switching is implemented - it is carried out not on the switching field, but in the network itself. In this case, telephone call servers are connected to the LAN and are used to establish and disconnect traditional telephone connections, as well as to perform additional functions, such as voice mail. As a rule, after a connection is established in such systems, the servers are switched off, and the subscribers' phones exchange voice packets directly.

In Russia there are currently similar systems with Ethernet-IP and ATM technologies.

The vast majority of local networks around the world implement one or another type of Ethernet technology (a typical network structure with a distributed LAN-PBX based on Ethernet technology is shown in Fig. 1). However, if you urgently need to deploy a telephone and computer network in a building where there is only telephone wiring, it is advisable to focus on distributed solutions for local ATM networks. In this case, high quality telephone communication is ensured, but network performance is significantly lower than when using Ethernet. In this case, telephone sets (analog or digital - depending on which telephone network is actually installed in the building) are connected to the network directly, and computer network equipment is connected through ATM modems. However, most often enterprise-class ATMs are implemented on twisted-pair wiring of a fairly high category, and the choice of this technology is dictated by the structure of data, voice and video traffic.

Network with integrated communication system

An integrated communications system (sometimes called an integrated LAN-PBX) combines the functions of the following devices: LAN switch, IP router, remote access server, VoIP gateway and PBX. In integrated communications systems (IP-PBX), switching is based mainly on PBX. In this case, the PBX is usually complemented by a LAN switch and an IP router, which is why it is called an integrated communication system. Connection switching is carried out by the telecommunications server in accordance with the list of services available to a particular user.

The main advantage of such systems compared to distributed ones is greater functionality, and with systems based on upgrading existing PBXs by installing additional VoIP gateways - also greater transparency.

Products in this category in Russia are presented by 3Com, Alcatel, Avaya, Samsung and Nortel Networks. Products from small companies such as Merlot Communications, Network Alchemy, Praxon and Vertical Networks are also sold abroad. The block diagram of a network with an integrated communication system is shown in Fig. 2.

When starting to select hardware and software solutions for organizing LAN telephony in your office, it makes sense to be guided by the following considerations.

If your office already has Ethernet and telephone networks deployed, then you probably have a PBX installed from a reputable manufacturer. In this case, it is advisable to settle on an intermediate solution - purchase an IP gateway and install it in the PBX.
If you're busy taking over a new building and installing new wiring, an advanced distributed solution or an integrated communications system may be right for you. However, in terms of one workplace, this will probably be more expensive than a PBX with an IP gateway.
An integrated communications system is preferable to a distributed network solution if users are accustomed to receiving a variety of telephone services provided by traditional PBXs (call transfer, follow me, parking, pick-up, announcement, etc. - about 200 functions in total). Distributed LAN-PBXs support only basic PBX functions (usually 10-20, in any case, no more than 25 basic functions), but in some cases this is not enough (for example, in distributed systems, as a rule, there is no barge in - operator intrusion into a conversation ). In addition, problems may arise when connecting to a city PBX using signaling methods specific to Russia.
If you have already settled on the most suitable solution, then when choosing a supplier you should consider factors such as ease of configuration, the ability to receive updated software, scalability, variety and completeness of functions. If the main thing is reliability and fault tolerance, then pay special attention to the possibility of equipment clustering provided by Cisco Systems. Some vendors also use core component redundancy (eg Alcatel OmniPCX 4400).
If your company has a corporate ATM network installed, then the options for choosing a PBX are sharply reduced. Before choosing a specific supplier, it is advisable to analyze the above factors.
Even when the decision is made to deploy equipment from a specific company, it will not be superfluous to be able to use LAN telephone devices from different manufacturers. The vast majority of such devices are considered compatible, but this only applies to IP devices. In fact, such compatibility must be tested in practice. 3Com equipment is practically incompatible with telephones from other manufacturers.
When choosing hardware and software, you should take into account factors such as cost per line or port, including the cost of the telephone set. The analysis showed that in terms of this indicator, the proposed solutions differ significantly - from $110 (Samsung) to $1000 (Nortel Networks and Cisco Systems). The specific value of the cost greatly depends on the configuration and delivery conditions, which are determined by the contract.
No one has any particular doubts about the feasibility of switching to the active use of IP telephony in corporate networks. However, when purchasing and deploying an enterprise IP telephony system, you should first think about what you need it for. The fact is that by leaving one wiring instead of two, you can get a system that is less reliable, although it has greater functionality. Therefore, weigh in advance all the possible consequences of such a responsible step.

Standards and algorithms

When creating LAN telephony systems, two basic standards are used - H.323 and SIP. To date, the H.323 ITU standard has become the most widely used, during the development of which the task was to “adapt” telephone equipment to work in computer networks. This standard is close to traditional signaling systems (Q.931-based circuit switched) and is therefore most widely used in systems developed by traditional telephone equipment suppliers. It became the first standard IP telephony protocol.

The SIP standard was developed by the IETF issue group and implements a simpler, Internet-based approach to HTTP-based signaling. Therefore, it was started to be used by precisely those companies that traditionally produced equipment for computer networks. However, everyone predicts a great future for this standard in LAN telephony, since it reflects the main trend - the “internetization” of telecommunications. Today, the SIP protocol is rapidly spreading, including thanks to the efforts of the SIPNET company. Some features, such as conferencing, are supported better by SIP than by H.323. Therefore, for now, you should choose a solution that supports both of these protocols, and in the future, it may be worth switching to using the SIP protocol. Some companies also use their own proprietary protocols (for example, Cisco Systems' Skinny Gateway Protocol, which it opened up for use by other companies).

Telephone sets

Currently, a company employee’s workplace can be equipped with voice communication in one of the following ways:

Telephone for direct connection to a LAN socket. In the case where Ethernet technology is implemented in the LAN, this is a digital Ethernet phone.
A multimedia personal computer (with microphone and headphones or speaker), equipped with telephone functions and connected to a LAN. The disadvantage of such a terminal device is typical for any personal computer - for example, it can “freeze” and the connection will be interrupted.
A regular analog telephone connected to a LAN.
LAN phones are often called IP phones. They should not be confused with system telephones - digital telephones manufactured by the same company as the rest of the telephone equipment, or terminal.