June 8, 2010 at 09:39Asterisk for the head
A lot of notes, articles and books have been written about the use of the free Asterisk software telephone exchange. Not once this question was raised on Habré - both about the device, and about installation, and about subtleties of configuration. Today I want to look at Asterisk through the eyes of an IT manager who has “heard something” and who has to decide whether to implement this product, or opt for a “classic” PBX hardware.
So, Asterisk is an open source software exchange. Its creator is quite a commercial company Digium, which made a competent marketing move a dozen years ago: in its pure “soft” form, Asterisk is applicable in a very limited number of situations, and as soon as the task of pairing with “classical” telephony arises, you can’t do it alone with software , you need quite material glands, for which you have to pay quite material money. Therefore, Digium began and sponsored the development of Asterisk, and itself was engaged in the creation and sale of hardware for it.
To be honest, it’s worth noting that several more companies are developing hardware solutions for Asterisk; their solutions are more budgetary, but at the same time, experts agree that the pieces of hardware "from the developer" are 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 "start up", or prefers, at the risk of saving.
Like any PBX, Asterisk is a mediator and a switch between external lines of communication (it can be copper lines from a local telephone exchange, E1 stream from a telephone service provider or IP-telephony channels) and a set of terminal subscriber devices - in other words, telephone sets on user desks . Asterisk itself is not very demanding on hardware; in most cases, the old P-4 is enough. By the way, low-profile rack servers can play a trick here: most expansion cards are quite large-sized and may simply not fit into a 1-2U package - this should be taken into account.
Well, with external lines everything is more or less clear: the corresponding expansion cards are bought and connected. The PCI-E board for 1 E1 stream with an echo cancellation module (I do not recommend taking an echo-pass) will cost about $ 850, there are also options for 2 and 4 threads (the latter will cost $ 2300 already).
The analog line board will be cheaper - a board with three FXO modules for connecting city lines (each module has 4 ports, for 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 board. In general, the choice of boards is rich, you can choose the best solution for each specific case.
The prices are taken from a well-known Moscow provider of IP-telephony equipment (I will not name them, so as not to be considered advertising) and more or less reflect the market. In any case, compared with the average average automatic telephone exchange, these figures look rather modest - in any case, they do not plunge into shock.
There are generally three options:
Here the picture is a little less rosy. A fee for 8 FXS modules allows you to connect 32 analog phones and will cost about $ 1000. But at the same time - how many such boards can be crammed into a regular server? 3-4 maximum. In total, it will be difficult to get more than 120 analog subscriber ports on Asterisk. You can, of course, install 2-3 servers by connecting them together by IP, but the fault tolerance of such a solution will be much lower.
With IP-phones this problem does not arise, but another arises: the price of the terminal device. The cheapest phones offered on the market cost about $ 80, which means that the devices for hundreds of subscribers will be pulled by $ 8,000. You can sweeten the pill a bit, remembering that most modern IP phones include a built-in switch for 2 ports, which allows you to use only one LAN port on each workstation by connecting a computer through the phone. This can be useful in cases where there are no conventional telephone ports and it is not planned to lay them - so you can save a little.
Well - headset, plus a software SIP-phone. The cheapest option, but also the most inconvenient for employees. It will probably work effectively only for call centers and similar places.
A classic office PBX is usually accompanied by a third-party organization, and the on-site system administrator most often knows how to solve only tasks such as “switch the number from one device to another”.
At the same time, mid-level unix administrator is quite capable of installing, configuring, and maintaining Asterisk. If a complex configuration is expected, you can use the services of outsourcers once, who will install and configure everything, show “where to pick it”, and then the ordinary administrator will definitely do it.
If you don’t have such an administrator at hand, and you really want to try it - there are a number of ready-made distributions based on Asterisk - just boot from the CD, click "next" several times - and voila: the PBX is ready and even has a shell (usually - web interface) for administration. True, the flexibility of such “boxed" solutions is much lower: what you put in the administration interface - use it. Enough for a small office, but going beyond is already difficult.
And now the most delicious thing comes: it's time to talk about flexibility. The fact that in classic PBXs with grief in half is provided by expansion cards valued at several kilobaxes - Asterisk already has and works.
So, Asterisk is an open source software exchange. Its creator is quite a commercial company Digium, which made a competent marketing move a dozen years ago: in its pure “soft” form, Asterisk is applicable in a very limited number of situations, and as soon as the task of pairing with “classical” telephony arises, you can’t do it alone with software , you need quite material glands, for which you have to pay quite material money. Therefore, Digium began and sponsored the development of Asterisk, and itself was engaged in the creation and sale of hardware for it.
To be honest, it’s worth noting that several more companies are developing hardware solutions for Asterisk; their solutions are more budgetary, but at the same time, experts agree that the pieces of hardware "from the developer" are 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 "start up", or prefers, at the risk of saving.
Like any PBX, Asterisk is a mediator and a switch between external lines of communication (it can be copper lines from a local telephone exchange, E1 stream from a telephone service provider or IP-telephony channels) and a set of terminal subscriber devices - in other words, telephone sets on user desks . Asterisk itself is not very demanding on hardware; in most cases, the old P-4 is enough. By the way, low-profile rack servers can play a trick here: most expansion cards are quite large-sized and may simply not fit into a 1-2U package - this should 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 board for 1 E1 stream with an echo cancellation module (I do not recommend taking an echo-pass) will cost about $ 850, there are also options for 2 and 4 threads (the latter will cost $ 2300 already).
The analog line board will be cheaper - a board with three FXO modules for connecting city lines (each module has 4 ports, for 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 board. In general, the choice of boards is rich, you can choose the best solution for each specific case.
The prices are taken from a well-known Moscow provider of IP-telephony equipment (I will not name them, so as not to be considered advertising) and more or less reflect the market. In any case, compared with the average average automatic telephone exchange, these figures look rather modest - in any case, they do not plunge into shock.
Terminal devices
There are generally three options:
- Ordinary analog phones
- IP Phones
- Headsets connected to a computer
Here the picture is a little less rosy. A fee for 8 FXS modules allows you to connect 32 analog phones and will cost about $ 1000. But at the same time - how many such boards can be crammed into a regular server? 3-4 maximum. In total, it will be difficult to get more than 120 analog subscriber ports on Asterisk. You can, of course, install 2-3 servers by connecting them together by IP, but the fault tolerance of such a solution will be much lower.
With IP-phones this problem does not arise, but another arises: the price of the terminal device. The cheapest phones offered on the market cost about $ 80, which means that the devices for hundreds of subscribers will be pulled by $ 8,000. You can sweeten the pill a bit, remembering that most modern IP phones include a built-in switch for 2 ports, which allows you to use only one LAN port on each workstation by connecting a computer through the phone. This can be useful in cases where there are no conventional telephone ports and it is not planned to lay them - so you can save a little.
Well - headset, plus a software SIP-phone. The cheapest option, but also the most inconvenient for employees. It will probably work effectively only for call centers and similar places.
Escort
A classic office PBX is usually accompanied by a third-party organization, and the on-site system administrator most often knows how to solve only tasks such as “switch the number from one device to another”.
At the same time, mid-level unix administrator is quite capable of installing, configuring, and maintaining Asterisk. If a complex configuration is expected, you can use the services of outsourcers once, who will install and configure everything, show “where to pick it”, and then the ordinary administrator will definitely do it.
If you don’t have such an administrator at hand, and you really want to try it - there are a number of ready-made distributions based on Asterisk - just boot from the CD, click "next" several times - and voila: the PBX is ready and even has a shell (usually - web interface) for administration. True, the flexibility of such “boxed" solutions is much lower: what you put in the administration interface - use it. Enough for a small office, but going beyond is already difficult.
Functional
And now the most delicious thing comes: it's time to talk about flexibility. The fact that in classic PBXs with grief in half is provided by expansion cards valued at several kilobaxes - Asterisk already has and works.
- Flexible - truly flexible numbering plans. Call forwarding, any dialing schemes — sequential, parallel, ring — are configured with a few lines in the configuration file. Your humble servant at one time for a couple of hours made the scheme of work of three competing client units - the call came to the secretary, that one button redirected the call to the router circuit and then he randomly went to one of the units (each of which also had its own schemes call movement).
Voice mail. Already ready, eat and work. No problems with integration with E-mail: the message left on the answering machine can come in the form of an mp3 file to the “soap”. As well as vice versa: a call to a technical support phone can automatically generate a request in the Service Desk system, with the definition of the caller.
Conference call . When the management stated that it wanted to organize telephone conferences with offices in other countries, the task took half an hour. And with all the amenities:
- A call to a teleconference number.
- a pleasant female voice: "please, be called."
- Vasya.
- a pleasant female voice, to the conference: "Joins us ... Vasya!".
Well and so on. Moderation, “leading” mode, etc. When the "classic" telephone operator saw this, he bulged his eyes: "Yes, you ... yes, you know how much the teleconference fee costs!" Five bucks! ”
Any other possibilities for 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 based on it - it works.Reliability
Often there is an opinion: Asterisk is unreliable. In response, I can only say one thing: I have experience in its operation for more than three years 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 units in other countries. There was not a single tangible malfunction; The uptime of the server is currently 269 days.Summary
So, a lot has been written, to summarize.
Asterisk is a fully working and fairly reliable solution. At the same time, as for any tool, there are situations both when its implementation makes sense and when it is disadvantageous.
It is not beneficial to use Asterisk in configurations with a large number of analog lines. If you have a small factory with 1000 subscribers and already wired - Asterisk only makes sense to put in conjunction with the usual hardware PBX of the enterprise, 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 a unix administrator on staff. Here Asterisk can show itself in the best possible way.
There is also an option for using Asterisk as a platform for developing telephone solutions - call centers, integrated telephone systems. But this is a completely different story.