Asterisk for the head
A lot of notes, articles and books have been written about using the Asterisk toll-free telephone exchange. Not once this question was raised on Habré - about the device, about the installation, and about the intricacies of configuration. Today I want to look at Asterisk through the eyes of an IT manager who has “heard something” and who has to make a decision to implement this product, or opt for a “classic” hardware PBX.
So, Asterisk is an open source software PBX. Its creator is quite a commercial company Digium, which made a competent marketing move a decade ago: in a pure “soft” form Asterisk is applicable in a very limited number of situations, and as soon as the task of conjugation with “classical” telephony arises - here you will not manage with just one software , we need quite material glands, for which we will have to pay quite material money. Therefore, Digium began and sponsored the development of Asterisk, and she took up the creation and sale of hardware for it.
For the sake of honesty, it is worth noting that several more companies are engaged in developing hardware solutions for Asterisk; their solutions are more budgetary, but at the same time, experts agree that the hardware “from the developer” is the most reliable. Well, then everyone decides for himself - he is ready to overpay a few hundred bucks for a fee that is guaranteed to “get started,” or he prefers to save, risking.
As with any PBX, Asterisk is an intermediary and a switch between external communication lines (these can be copper lines from a city PBX, an E1 stream from a telephone service provider or IP-telephony channels) and a set of end user devices — in other words, telephone sets on users' tables . Asterisk itself to the "hardware" is not very picky, in most cases, the old P-4 is enough. By the way, low-profile rack-mount servers here can play a cruel joke: most expansion cards are quite large and can simply not fit into the 1-2U case - this must be taken into account.
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Well, with external lines everything is more or less clear: the corresponding expansion cards are bought and connected. The PCI-E card for 1 E1 stream with an echo cancellation module (I don’t recommend taking an echod) will cost approximately $ 850, there are also options for 2 and 4 flows (the latter will cost $ 2,300).
An analog line card will cost less - a card with three FXO modules for connecting city lines (each module - 4 ports, a total of 12 lines) will cost about $ 650. At the same time, it is possible to install both modules for connecting city lines and modules for subscriber devices on one host card. In general, the choice of boards is rich, you can choose the optimal solution for each case.
The prices quoted are taken from a well-known Moscow supplier of IP-telephony equipment (I will not call it, so that it would not be considered advertising) and more or less reflect the market. In any case, compared with the usual average PBX, these numbers look quite modest - in any case, they do not plunge into shock.
In general, there are three options:
Here the picture is a little less rosy. The board for 8 FXS modules will allow you to connect 32 analog phones and will cost approximately $ 1000. But at the same time, how many such boards can you cram into a regular server? 3-4 maximum. So it turns out that getting more than 120 analog subscriber ports on Asterisk will already be difficult. You can, of course, put 2-3 servers, linking them together over IP, but the fault tolerance of such a solution will be much lower.
With IP phones this problem does not arise, but another one rises: the price of the terminal device. The cheapest of the phones on the market cost about $ 80, which means that the devices for hundreds of subscribers will pull on $ 8,000. You can sweeten the pill a bit, remembering that most modern IP phones include a built-in 2-port switch, which allows using only one local network port on each workplace by connecting a computer through a telephone. This can be useful in cases where there are no regular telephone ports and there are no plans to lay them - this is how you can save a little.
Well and - headsets, plus software SIP-phone. The cheapest option, but also the most inconvenient for employees. Effectively, it will work, perhaps, only for call centers and similar places.
A classic office PBX is usually accompanied by a third-party organization, and the system administrator in place often knows how to solve only tasks of the “switch number from one device to another” level.
At the same time, a mid-level unix administrator is fully capable of installing, configuring, and maintaining Asterisk. If a complex configuration is intended - you can use the services of outsourcers once, who will collect and configure everything, show “where to pick” and then the usual administrator will do it right.
If there is no such administrator at hand, but I really want to try - there are a number of already ready distributions based on Asterisk - just boot from the CD, click "next" several times - and voila: the PBX is ready and there is even a shell (usually - web interface) for administration. True, the flexibility of such "boxed" solutions is much lower: that they have laid the foundation of the administration interface - so use it. Enough for a small office, but going beyond it is already difficult.
And now comes the most delicious: it's time to talk about flexibility. The fact that in classic PBXs with grief in half is provided by expansion cards at the cost of several kilobaxes - Asterisk already has and works.
So, Asterisk is an open source software PBX. Its creator is quite a commercial company Digium, which made a competent marketing move a decade ago: in a pure “soft” form Asterisk is applicable in a very limited number of situations, and as soon as the task of conjugation with “classical” telephony arises - here you will not manage with just one software , we need quite material glands, for which we will have to pay quite material money. Therefore, Digium began and sponsored the development of Asterisk, and she took up the creation and sale of hardware for it.
For the sake of honesty, it is worth noting that several more companies are engaged in developing hardware solutions for Asterisk; their solutions are more budgetary, but at the same time, experts agree that the hardware “from the developer” is the most reliable. Well, then everyone decides for himself - he is ready to overpay a few hundred bucks for a fee that is guaranteed to “get started,” or he prefers to save, risking.
As with any PBX, Asterisk is an intermediary and a switch between external communication lines (these can be copper lines from a city PBX, an E1 stream from a telephone service provider or IP-telephony channels) and a set of end user devices — in other words, telephone sets on users' tables . Asterisk itself to the "hardware" is not very picky, in most cases, the old P-4 is enough. By the way, low-profile rack-mount servers here can play a cruel joke: most expansion cards are quite large and can simply not fit into the 1-2U case - this must be taken into account.
')
External communication lines
Well, with external lines everything is more or less clear: the corresponding expansion cards are bought and connected. The PCI-E card for 1 E1 stream with an echo cancellation module (I don’t recommend taking an echod) will cost approximately $ 850, there are also options for 2 and 4 flows (the latter will cost $ 2,300).
An analog line card will cost less - a card with three FXO modules for connecting city lines (each module - 4 ports, a total of 12 lines) will cost about $ 650. At the same time, it is possible to install both modules for connecting city lines and modules for subscriber devices on one host card. In general, the choice of boards is rich, you can choose the optimal solution for each case.
The prices quoted are taken from a well-known Moscow supplier of IP-telephony equipment (I will not call it, so that it would not be considered advertising) and more or less reflect the market. In any case, compared with the usual average PBX, these numbers look quite modest - in any case, they do not plunge into shock.
Terminal devices
In general, there are three options:
- Conventional Analog Phones
- IP phones
- Computer Headsets
Here the picture is a little less rosy. The board for 8 FXS modules will allow you to connect 32 analog phones and will cost approximately $ 1000. But at the same time, how many such boards can you cram into a regular server? 3-4 maximum. So it turns out that getting more than 120 analog subscriber ports on Asterisk will already be difficult. You can, of course, put 2-3 servers, linking them together over IP, but the fault tolerance of such a solution will be much lower.
With IP phones this problem does not arise, but another one rises: the price of the terminal device. The cheapest of the phones on the market cost about $ 80, which means that the devices for hundreds of subscribers will pull on $ 8,000. You can sweeten the pill a bit, remembering that most modern IP phones include a built-in 2-port switch, which allows using only one local network port on each workplace by connecting a computer through a telephone. This can be useful in cases where there are no regular telephone ports and there are no plans to lay them - this is how you can save a little.
Well and - headsets, plus software SIP-phone. The cheapest option, but also the most inconvenient for employees. Effectively, it will work, perhaps, only for call centers and similar places.
Escort
A classic office PBX is usually accompanied by a third-party organization, and the system administrator in place often knows how to solve only tasks of the “switch number from one device to another” level.
At the same time, a mid-level unix administrator is fully capable of installing, configuring, and maintaining Asterisk. If a complex configuration is intended - you can use the services of outsourcers once, who will collect and configure everything, show “where to pick” and then the usual administrator will do it right.
If there is no such administrator at hand, but I really want to try - there are a number of already ready distributions based on Asterisk - just boot from the CD, click "next" several times - and voila: the PBX is ready and there is even a shell (usually - web interface) for administration. True, the flexibility of such "boxed" solutions is much lower: that they have laid the foundation of the administration interface - so use it. Enough for a small office, but going beyond it is already difficult.
Functional
And now comes the most delicious: it's time to talk about flexibility. The fact that in classic PBXs with grief in half is provided by expansion cards at the cost of several kilobaxes - Asterisk already has and works.
- Flexible - truly flexible numbering plans. Redirects, any dialing schemes - sequential, parallel, circular - are configured by several lines in the configuration file. In due time, your humble servant made the work of three competing client departments in a couple of hours - the call went to the secretary, she forwarded the call to the router circuit with one button and then he randomly went to one of the departments (each of which also had its own call traffic).
Voice mail Already ready, there is and works. No problems with integration with E-mail: left on the answering machine message can come in the form of an mp3 file on the "soap". As well as vice versa: a call to the technical support phone can automatically form an application in the Service Desk system, with the caller's definition.
Conferencing . When the management stated that it wanted to organize conference calls with offices in other countries, the solution of the problem took half an hour. And with all the amenities:
- Call to the number of the newsgroup.
- a pleasant female voice: “please call it.”
- Vasya.
- a pleasant female voice to the conference: “We are joined by ... Vasya!”.
Well, and so on. Moderation, mode "master", etc. When the “classic” telephone operator saw this, he goggled his eyes: “Yes, you ... yes, you know how much a teleconference board costs! Five bucks! ”
Any other possibilities of taste and color . Asterisk can work with databases, has an API for working with external applications. I personally participated in the creation of the “telephone-bank” system on its base - it works.Reliability
Often there is an opinion: Asterisk is unreliable. In response, I can only say one thing: I have experience of more than three years of operation in a bank, with hundreds of IP-telephone internal subscribers, two E1 streams from different providers, a dozen analog copper lines and three IP-telephony channels with divisions in other countries. There was not a single tangible malfunction; server uptime is currently 269 days.Summary
So, a lot has been written, let's sum up.
Asterisk is a working and quite reliable solution. At the same time, as for any instrument, there are situations, both when its implementation makes sense, and when it is unprofitable.
It is not profitable to use Asterisk in configurations with a large number of analog lines. If you have a small plant with 1000 subscribers and wiring already laid out - it makes sense to put Asterisk in conjunction with the company's usual hardware PBX, connecting them with E1 or IP telephony.
It is advantageous to use Asterisk in a small office (up to 100 subscribers) with high requirements for the level of telephone services and if there is an unix administrator on the staff. Here, Asterisk can show itself at its best.
There is also the option of using Asterisk as a platform for developing telephone solutions - call centers, integrated telephone systems. But that's another story.
Source: https://habr.com/ru/post/95795/
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