A person constantly needs communication - this is a scientifically proven fact. Alexander Bell began erasing the boundaries between people in 1876 by inventing the telephone. Over time, humanity has acquired mobile communications and the Internet; now subscribers are available anywhere in the world. But nevertheless, newer means of communication are appearing, one of them is IP technology.

How IP telephony works

IP technology is aimed at transmitting voice signals through a system built on IP networks or Voice over IP (voice over Internet protocol).
Devices that allow communication between two subscribers (phones, computers) are called IP gateways. The telephone signal, passing through the gateway, is converted (digitized, compressed) and sent via the IP network to the dialed subscriber. Next, the receiving IP gateway deciphers the information and delivers it to the subscriber.

Compared to conventional communications, IP telephony has a number of advantages:

Use communications to hold conferences with a large number of people, also through Skype.
- Possibility of transferring voice and text messages, video and audio files over the network.
- Communication can be carried out anywhere where there is Internet.
- Possibility of data transfer.
- The network is never busy.

Pros and cons of IP telephony

IP technology has both pros and cons.

Pros:

• - Low cost of connection, no matter where subscribers are located.
• - Improved call quality, does not depend on the distance between callers.
• - Consolidation of computer and telephone networks.

Minuses:

• - If the Internet transmission speed is low, the quality of communication will leave much to be desired.

The problem can be solved by increasing the speed or isolating a separate line.
Based on the above, IP telephony opens up great opportunities for enterprises with a large infrastructure, because significantly reduces communication costs and simplifies the process of connecting employees with each other.

Currently, about 400 companies provide IP services on a card basis.
The development of means of communication between people is constantly evolving; once upon a time we could not believe that we would talk and see a person in real time who was in another city. And so, this became possible with the help of IP telephony and Skype. Probably not everyone has yet understood the advantage of digital communication, and there are probably people who have not even heard of it. But who knows, maybe in the near future we will forget about telephone communications; a start has already been made for this.

20.01.2015

Any advertising strives to show only the best and most attractive aspects of a product, preferring to leave aside its shortcomings. It often happens that, having discovered these disadvantages, users share them with each other, thus focusing attention only on them. As a result, interest in the service decreases, and the company wonders what the reason is. Did not remain aloof from this trend and ip telephony. We invite you to get acquainted with some myths about this technology.

Myths about IP telephony

Myth one: poor sound quality. IP communications require the operator to comply with technical requirements for Internet speed and high-quality receiving and transmitting equipment. Where these requirements are not met, sound quality suffers. Typically, such providers offer their services at a reduced price. It should also be taken into account that in specialized IP phones the quality of sound transmission will be higher than in regular phones or in a headset.

Myth two: high cost of the service. Modern ip telephony tariffs which depend on the service package, offers its users budget and advanced options. For those customers who are interested in quality service, the operator will offer more advantageous options, but their cost will be higher than standard offers.

Myth three: it is not profitable for small companies to use this service. Telephone communication is an integral part of the work process, and here you should pay attention to the fact that IP communication tariffs are cheaper than regular ones. As a rule, operators offer a preferential package of services for companies that often use long-distance communications. The created single telephone space with one number will allow you to communicate with any client at any time and use the database to solve various work problems.

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In this article we will talk about software IP PBX(especially about the Asterisk family) - the foundation of modern corporate VoIP telephony. We will look at their main capabilities, configuration tricks, but most importantly, we will objectively analyze the pros and cons of these solutions. Let’s also try to estimate how much it will actually cost companies to implement a “free” (in quotes) software IP PBX.

Office PBX has been and remains one of the most important tools for communication between employees of business organizations and “average” citizens (potential consumers of goods and services), partner companies, suppliers of materials and components, distributors and representatives of government agencies. The basis of its functionality is initially the solution of problems of connecting the telephone sets of the calling and called subscribers, maintaining a communication session and disconnecting the connection upon completion of the conversation. To these “three pillars” of voice line switching, more and more new functions and services were gradually added, and currently their number reaches two to three dozen (depending on the PBX model).

Modern mini-PBXs are good for everyone, but for companies just starting their business, the cost of creating an internal telephone network on their basis sometimes seems “unaffordable.” And in search of a cheaper (but equivalent in functionality) technical solution, startups go to the segment of computer, that is, VoIP telephony, which provides the ability to transmit voice and digital information in one channel (and the company already has a local computer network “by default”).

In this segment, the lion's share of the market belongs to corporate telephone exchanges, the operation of which is based on the IP protocol (Internet Protocol), designed to organize the exchange of data in digital form (including speech) using packet switching (remember that traditional telephony uses channel switching). Such stations form an IP-PBX class, with two groups included in it: 1) hardware IP PBXs and 2) software IP PBXs, most of which are Linux distributions or executable files for Windows OS. We will talk in more detail about the second group today.

In a software IP PBX, all functions of analog, digital and hybrid telephone exchanges performed by switches, routers and other equipment are emulated by special software that is installed on any server or desktop running in the company

In the second group of the IP-PBX class, today there are about 20 varieties of so-called “free software” with open source code, which, by definition, gives consumers the right to supplement it with new functions that are needed. At the same time, almost half of the area of ​​free software for software PBXs refers to free products. And among them, the undisputed leader is the IP-PBX Asterisk, which is far ahead of its competitors, who share approximately 15% of the open-source IP-PBX market, which it left to outsiders. And most “starting up” small business companies focus on its use.

Advantages of software IP PBXs

What is the reason for such a high degree of popularity of IP-PBXs like Asterisk (Asterisk in English means an asterisk)?

Firstly, it has in its arsenal a full set of basic and additional functions of a mini PBX.

Secondly, it works with Skype.

Thirdly, it provides video communication.

Fourthly, its capabilities can be expanded, for example, in terms of parallel servicing of tens and even hundreds of telephone conversations, if computer boards are connected to the server with Asterisk software installed, providing communication with high-bandwidth lines such as T1/E1.

Competing free programs, intended mainly for IP-PBXs for specific applications, do not have such a set of characteristics (although in their areas they may surpass Asterisk in certain indicators).

Asterisk administration can be carried out using several graphical management tools, but the choice of most users, as a rule, is the FreePBX web interface, with the help of which subscriber numbers and functions can be added or replaced without much difficulty.

Both softphones (softphones) and all types of hardware user IP phones (with IP, USB, Wi-Fi interfaces) can be connected to the Asterisk software IP PBX.

The range of Asterisk functionality and services is constantly being replenished by many “free developers”, but such a “plus”, apparently, can only be appreciated by experienced users, while the majority of consumers are experiencing more and more difficulties with mastering new versions and ensuring their stability work. And this, as many years of experience in operating Asterisk shows, is not the most “terrible” of the shortcomings of this software (as, indeed, of other software PBXs).

Disadvantages of software IP PBXs

So, Asterisk software or any other similar IP PBX software can be downloaded for free on the Internet. Unfortunately, this is where the “free” ends.

The first cost item is installing Aterisk on the server. Since this is a complex software that uses the Linux operating system as a platform, a specialist who is well versed in it is required. That is, to install Asterisk you will have to hire an integrator company.

Advice from practice - the biggest mistake a company manager can make is to involve a full-time system administrator in the installation and, most importantly, in configuring Asterisk. The apparent simplicity of commissioning this IP PBX has already led to very large unplanned expenses in many companies, including eliminating the consequences of hacking (more on this below).

The second cost item is administration and maintenance. Performing these functions requires a Linux professional with knowledge of Asterisk and IP telephony technology and equipment. Such an “expensive employee” will have to be accepted into the company’s staff or “grow” into its ranks by spending money on his training and then paying him a high salary.

Advice from practice - the system administrator, who is usually involved in the administration of the PBX in companies, can, at best, cope with the basic setup of the system. Complex routing algorithms or advanced settings will require dozens of hours of digging through documentation and spending time on thematic forums. Moreover, frequent system updates (which are necessary) in the first year or two will lead to one or two days of complete loss of communication in the office. And all this will continue until your system administrator learns everything.

Thus, the cost of ownership and operational support of a free software PBX over time may exceed the cost of purchasing a hardware IP-PBX with an outsourced support service.

The main danger facing companies using Asterisk is the fairly easily realized possibility of external intrusion into the PBX. The most common reason for Asterisk hacks is the inability to correctly make the basic security settings of a software IP PBX. The second security weakness is due to the fact that, as noted above, “free programmers” often introduce new functional modules into Asterisk (which, in fact, users themselves can do), which introduce new vulnerabilities into the base software. Finding these gaps is not difficult for experienced hackers, and as a result of a successful attack, a wave of transit calls is sent through Asterisk, for which you will have to pay a tidy sum.

Why IP telephony and VoIP technology in general are cool. And now, we invite you to look at the other side of the coin. Every technology has its own disadvantages, vulnerabilities and limitations, and VoIP is no exception. So, we've found 9 reasons why VoIP sucks. Go!

Problems with NAT

The SIP and H.323 signaling protocols work by exchanging messages with an IP telephony server. The user who makes the call and the user who receives it may be on different networks behind NATing devices. Despite this, VoIP traffic can reach the server, and users will hear the call after the call parameters are fully negotiated. As soon as the user receiving the call picks up the phone, the media protocol - RTP - comes into play, which will send packets to the internal address of the remote phone (since it is the internal address that will be indicated in the previous SIP / H.323 headers), instead of sending them to the correct NATed address. But even if RTP packets are sent to the correct NATed IP address, most firewalls, especially those without the appropriate configuration, will drop such packets. So, if you decide to implement IP telephony and you have remote employees or branches, be prepared to understand the theory of NAT and configure the Firewall correctly.

Problems with connection quality

Circuit-switched networks (CSTN) guarantee excellent quality of transmitted audio information, since they do not share the transmission medium with other services. IP telephony typically intersects with other user traffic, such as mail and the Internet. Therefore, in order to achieve the same good voice quality when using IP telephony, it is often necessary to correctly configure traffic prioritization or even upgrade the existing infrastructure.

Caller location

In the case of circuit switched networks, information about the subscriber's location is recorded only once when the service is directly provided to the subscriber and is changed only if he moves, while the number is retained. In the case of mobile cellular networks, information about the subscriber's location can be determined using the triangulation method using the existing coordinates of base stations (mobile towers) or using GPS coordinates reported by the subscriber's mobile phone. In VoIP networks there is no easy way to determine the location of the caller, which is very often used by all sorts of scammers, extortionists, trolls and other dubious individuals. Some may think that this is good - why give someone the opportunity to find out your location? But think about the safety of yourself and your employees. If you call the emergency number in an emergency, they will also not be able to determine where the caller is, which could cost someone their life.

Substitution of CallerID and access to private data

CallerID (CID) is information about the calling subscriber's number. Many organizations use this information to determine whether a call from a particular number should be accepted or not. In the case of a public telephone network, this information is reported by the subscriber's home network. In VoIP networks, the CID is configured by the VoIP server administrator. The administrator can be either an honest VoIP telephony provider or an attacker who wants to impersonate someone else by replacing his number (CID).

In addition, since the number information (CID) is transmitted during the process of negotiating the parameters of a future SIP or H.323 connection, it can be intercepted using special programs such as Ethereal, tcpdump and Wireshark. Therefore, even if your provider hides your CID, you can still find it out by analyzing the intercepted connection traffic.

Phone interface

IP phones often have a very sparse interface that limits the ability to set a password to just numeric values, instead of a strong password based on the entire ASCII character set. In addition, many organizations neglect security and create a password that matches the internal number of the employee. (ext: 3054, secret: 3054). It is not difficult to guess that an attacker who has gained access to a phone will first try to guess the password and enter the internal number of the corresponding phone as it.

SIP authentication attack

During the SIP authentication process, passwords are transmitted not in clear text, but as hashes of these passwords calculated using the MD5 algorithm. An attacker can intercept traffic and use dictionaries offline to decrypt hashes to obtain the password. Again, if you use weak passwords, such as employee extension digits, then such hashes will take milliseconds to decrypt.

Interception of conversations

By the way, intercepting RTP traffic is also not difficult, namely, RTP packets contain voice information, that is, what you say. Having captured enough RTP traffic, you can decode it and listen to what the conversation was about.

DoS attack (denial of service) via SIP protocol

Due to the fact that the SIP protocol uses UDP as a transport protocol, which does not establish preliminary sessions, an attacker can “craft” SIP packets and bombard an IP telephony server with them. For example, he can bombard the server with packets like SIP CANCEL, which will force it to interrupt all ongoing calls.

Software vulnerabilities

VoIP servers, phones, gateways and softphones are solutions that contain one or another software. All kinds of DBMS, programming languages, software connectors, interpreters, modules, operating systems - critical vulnerabilities are constantly found in all of this, and information about these vulnerabilities is published in open sources. If you use old software, do not monitor and regularly update it, then you are at risk become a victim of attackers who know about these vulnerabilities and know how to exploit them.

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Telecom operators and the business community were the first to appreciate all the advantages of IP telephony compared to analogue: creating a corporate telephone network based on Internet data transmission channels is very profitable.

In addition to savings and the ability to deploy your own corporate network, IP telephony can provide a lot. So, what are the advantages of IP telephony?

First, communication systems are scalable

The advantage of IP telephony is that it allows you to quickly change the virtual PBX database: add or exclude subscribers from it. Most of the functionality is implemented through cloud technologies.
A virtual PBX allows you to build an office structure regardless of the size of your business. At the same time, digital communication systems make it possible to use virtual data exchange channels within a single network of branches, which eliminates the need to install equipment in all offices and branches.

Secondly, IP telephony is profitable

The advantage of Internet telephony compared to traditional telephony is that it saves money. As a rule, when switching to IP telephony, communication costs are greatly reduced in the first month. In addition, the range of tariffs in this case is quite wide: the choice of tariffs in IP and traditional telephony cannot be compared.

Thirdly, IP telephony removes distance restrictions

Whether working in the office, on a flexible schedule or remotely, employees constantly stay in touch. There is no longer any need to allocate money for communications on business trips and calls to branches: all company numbers are combined into a common network.
Digital communications make it possible to hold conferences, meetings or video presentations, automatically forward calls to the right subscribers and perform other actions that facilitate quick communication.

Fourth, ease of data management

IP and traditional telephony differ in that the first allows you to access any statistical data and set limits for spending funds. You can set restrictions on outgoing connections with certain subscribers.

Most hardware IP phones use SIP protocols because they work independently of a PC.

The advantages of SIP telephony make it easy to connect, and there is no need to lay additional lines. In addition, the low cost of SIP telephony is also ensured due to the characteristics of the channel.

There are indeed many advantages of IP telephony, but the transition to it must be deliberate, and the possibility of its use must be considered individually. The advantages of digital telephony are undeniable, but there are also disadvantages of IP telephony. The most important of them can be called direct dependence on the Internet. The Internet turns off and the telephone connection disappears. But this problem can be solved using forwarding: if it is not possible to contact an employee via an office phone, the call goes to his mobile phone.

Another disadvantage: when customizing the configuration, you need to program the PBX, as a result of which failures are possible, including severe and long-term ones. At best, they can create confusion for employees; at worst, they can lead to additional costs to resolve the problem.

There is also the possibility of hacking and data theft, since a computer network is used for communication.

And finally, it’s worth saying a few words about the high cost of equipment, as well as the fact that IP telephony is not always the cheapest solution.

The disadvantages of IP telephony are insignificant compared to its advantages, and the advantages of IP telephony are very impressive.

To make the right and final decision, you need to contact our company’s employees, who will quickly select the best option for your capabilities and needs.
We stay in touch with our clients after completion of the work and are always ready to help and advise if required.