SIP telephony - what it is and how it works. We explain in detail.

Most users of the global network know and even actively use the method of transmitting multimedia data over the Internet - the Internet Protocol (IP). Simply put, exchanging information, including audio messages, requires an IP connection between devices.

But what is SIP telephony? This is one of the voice information transmission protocols, which is based on the principles of IP telephony. SIP stands for Session Initiation Protocol. Used for many purposes - audio and video conferencing, telephony, online games and more. The SIP protocol operates in a client-server-client fashion, alternating requests and responses.

Next, we will dwell in detail on the operating algorithm, differences from IP and VoIP, and the advantages of SIP telephony.

What is SIP telephony

Technically speaking, SIP (Session Initiation Protocol) is a session initiation protocol, that is, a way to send voice calls over a SIP channel. While older phone systems sent calls over a copper wire to the PSTN, which is the telephone switched telephone network, SIP calls use Internet Protocol. In this case, a call can be received and made to any number.

Thus, SIP telephony is a system for sending and receiving calls over the Internet, which does not use physical communication lines.

What is a SIP trunk? This is directly a method of organizing communication, that is, a communication channel between your business equipment and a communication service provider (like Nextel). In IP telephony, this communication channel is virtual, that is, it does not require wires between the equipment, and the equipment itself can be located in different cities or in different countries. That is, a SIP trunk is a highway through which data is transferred from the sender to the recipient.

If we talk about the distinctive features of SIP calls, we can highlight 3 features:

1. High quality voice communication . Unlike an analog phone system, which only supports standard definition audio, a SIP route provides high-definition signal for clearer, interference-free audio (assuming you have a good internet connection).
2. Call forwarding . This is a SIP feature to redirect calls according to predefined settings. For example, you can set up custom scripts for routing calls between departments with different technical support specialists, forwarding by time of day, based on a unique subscriber ID, and so on.
3. Convenient interface for management . Nextel IP telephony allows you to connect any number of SIP numbers for personal use, a sales department or an entire call center. At the same time, you or your operators will be able to view, manage and analyze calls through a user interface that is convenient, simple, intuitive and accessible without any IT training.

What is a “protocol” in Internet communications?

If you are reading this text, you are probably already familiar with many Internet protocols and related technologies. Click on the address bar of this page - it displays:

https://nextel.cloud...

https:// is a protocol for transmitting data, in this case, data about the content of this page.

Remember your last email registration. In the process, you probably came across settings with the labels IMAP, POP3 or SMTP - these are also protocols, specifically email protocols. This is a kind of highway for sending and receiving letters.

So SIP is the same thing in the world of voice communication. It is a real-time communication channel for video and voice calls, as well as text messages.

Mango Office

Another leader in the Russian IP telephony market is Mango Office. This service has been operating for 18 years. A distinctive feature of the company is that it offers its clients more than 200 communication services. That is, users can connect to almost any SIP telephony service they need. Of course, you will have to fork out for such convenience, since many of these services are paid.

The basic build of virtual PBX from Mango Office has about 50 free functions. The cost of services per month for three users is approximately 700 rubles.

In addition to the niche services described above, SIP telephony services are also provided today by representatives of cellular communications. For example, MTS, Beeline and Megafon have diversified their services and are now actively connecting SIP telephony to their business clients. Only paid tariffs have the ability to connect to numbers of third-party companies.

The Mango Office service features good 24/7 support service and a service for connecting virtual numbers in 75 Russian cities. Connecting these numbers is free, you just have to pay monthly for the service. The only negative is that there are no foreign numbers in the Mango Office database.

The difference between SIP and IP and VoIP

VoIP stands for Voice over Internet Protocol, that is, voice communication over the Internet Protocol. In order for a call to go through this same Internet protocol, you need SIP - Session Initiation Protocol, that is, a session initiation protocol. Therefore, we can say that SIP is the basis of IP telephony. SIP allows a company to make voice calls and send messages over networks connected to the Internet.

It is important to note that SIP is not the only protocol used in Internet telephony, it is simply the most common.

IP telephony with SIP is a replacement for the old wired communication lines, which included a PBX system and a hardware line for transmitting analog signals. Local physical telephone lines required a significant initial investment, plus they were much more difficult to scale. And, let’s face it, customization was more absent than present.

SIP lines and VoIP technology have eliminated all these problems:

• they do not require physical equipment other than any device (computer, phone) connected to the network;
• no need for physical telephone lines - cables and wires in the office with its own PBX;
• a team is not needed to maintain this PBX, because the PBX is virtual;
• you can create a completely customized workspace through flexible configuration of your Nextel personal account;
• Different payment plans are available to pay only for relevant functions and not overpay.

Accordingly, the main difference between traditional and IP telephony is technology. IP telephony is a cloud service with a virtual PBX and space for transmitting, storing and processing your data.

It is important to understand that SIP is not a mobile number. It is not tied to a specific region or country, uses its own protocol (not GSM communication), and does not require a SIM card. Thus, although a SIP number may not be visually different from a mobile number, these are also fundamentally different technologies. Read more in our article “What is the difference between a number in SIP format and a mobile one.”

Telfin

The popular Russian provider Telfin has been providing its users with SIP telephony services for 15 years. The main product of the company and its distinctive feature is the virtual PBX Telfin. Office". The cost of Telfin services for four users per month is approximately 800 rubles. As additional options, you can connect a contact book, call monitoring, call quality assessment, analytics, missed call monitoring, call tracking, etc.

Telfin stands out from its competitors by the large number of free services already added to the virtual PBX in the form of basic functions. The standard functionality, for example, already includes voice mail, recording and the ability to save up to 1000 minutes of calls, API for integration with other applications, conference calling, Caller ID (automatic number identification), call log and statistics, call queue and various scenarios redirects.

The provider works with 38 countries around the world, connecting their numbers to its users. In addition, Telfin additionally offers virtual mobile numbers for St. Petersburg and Moscow, as well as 8-800 numbers.

How SIP telephony works

Step-by-step algorithm of how a SIP call works:

1. The call comes from a SIP phone.
2. The call passes through the PBX (cloud or office) and enters the IP network.
3. The call enters the Internet through the NNI (network-to-network interface) - this is a kind of connecting link between the Internet provider and the telephony network. Depending on the ISP, the SIP call will be routed through either a public or private route. The difference is in the level of security: the public route is not encrypted, while the private route goes directly through the client's Internet connection and does not end up on the public network.
4. SIP goes from the Internet (read: public space) to the Nextel network, and then goes to the IP network of a specific recipient.
5. Then there are two options. If a specific call recipient is using a digital device (connected to the internet), their call goes through directly. If he is using an analog telephone, then the call is routed through an analog telephone adapter (ATA).
6. The call rings, the subscriber can pick up the phone!

SIP makes calls via the Internet, the call can go to any device: mobile phone, analog (landline) number, telephone connection in the elevator of a residential building, other business telephone systems - in general, without restrictions. And the transfer of a signal from an IP network through an analog adapter takes a matter of seconds!

This is what the SIP call algorithm looks like in the picture:

Zadarma

Zadarma has been offering its services for 15 years. The main advantage of this provider is the low cost of calls: from 44 kopecks to landline numbers and from 1.65 rubles to mobile numbers.

The list of services includes numbers with code 8-800, numbers from 100 countries. The minimum monthly subscription fee is only 140 rubles, and many numbers are connected completely free of charge. When connecting to some tariffs, the user receives a virtual PBX for 30 participants, also free of charge. The disadvantage is that you need to pay additionally for the SMS notification service.

What you need to receive and send calls via SIP

SIP allows you to establish communication via a computer/phone and the Internet. Without any boundaries! Voice and video calls over SIP are free, there are no restrictive laws for them, there is no roaming or per-minute charges. This is a cost-effective part of Internet telephony that allows you to take advantage of the benefits of VoIP (IP telephony) while reducing communication costs.

To get started, you need to get a SIP address, and then install and configure a SIP client on your computer or phone. Let's look at everything you need to get started with SIP in more detail:

• SIP address/account. It can be obtained from an IP telephony provider, for example, by creating a free account in the Nextel service;
• SIP client. This is an application for a computer or mobile device that works as a kind of softphone and at the same time an interface for telephony management;
• Internet. IP telephony is telephony over the Internet protocol, and therefore a stable connection with good bandwidth is a must-have;
• communication device. Headphones and a microphone or headset - and you are ready to talk!

Gravitel

The Gravitel service has been operating in the IP telephony market for 12 years. The basic assembly of the virtual PBX from Gravitel includes about 80 functions for business. For five users per month you need to pay almost 1,800 rubles, so the cost of the service can be considered a disadvantage. The company has good 24/7 technical support. You will have to pay extra for storing calls, increasing the call recording time, and external numbers.

By connecting a virtual number to Gravitel, the user will receive a free package for 3000 minutes monthly to landline numbers in both capitals of Russia. The Gravitel database contains numbers from 44 cities in the country, as well as federal numbers 8-800.

Advantages of SIP telephony

1. Management . Unlike PRI-based solutions, SIP is not tied to a physical copper channel, that is, it is not limited by the presence of a local communication network. SIP allows you to create multiple virtual paths to ensure that your SIP network is always up and running. This not only increases the availability of communication (which is extremely important for business!), but also saves time on management. No wires, no problems with maintenance, repair, replacement...
2. Profitability . SIP allows you to reduce costs through a more flexible payment system. In particular, if you use multi-channel lines for business, it is you who determines the required number of channels. This means you don’t overpay for a standard set that you may not need at all. Choose a solution that meets your specific business needs and pay only for it.
3. Scalability . SIP is much easier to scale; thanks in no small part to the simple control via the user interface. That is, when you need to increase the number of lines for operators, this can be solved with a couple of clicks in your personal account (which make changes to the operation of the Nextel cloud PBX), rather than working with a real telephone exchange in the office, which requires a specialist who may have limited resources and another 1000 and 1 limit.
4. Unification . SIP communication is not limited locally, is flexible and accessible - much more affordable than traditional analogue. This is especially true in our time, when remote work is becoming the norm, which means we need solutions that will maintain the quality of business processes regardless of the location of employees. Nextel service allows you to make high-quality calls wherever you are.

MTT Business

And finally, the federal communications business provider MTT Business, which has been operating on the market since 1994. According to the company’s most popular tariff, the client receives a virtual PBX for 5 workplaces for 1,500 rubles, while a monthly fee of 1,900 rubles is required for the service.

There are about 20 functions in the basic configuration of the PBX, and you will need to pay separately for SMS notifications, recording conversations and individual greetings, and auto call back. The MTT Business database contains numbers from 92 Russian cities, numbers with an 8-800 code and mobile numbers.